Science.gov

Sample records for quaternary fission

  1. P-odd, P-even, and T-odd asymmetries in true quaternary fission of nuclei

    SciTech Connect

    Kadmensky, S. G. Titova, L. V.

    2013-04-15

    The coefficients of P-odd, P-even, and T -odd asymmetries for a third and a fourth prescission particle emitted in the true quaternary fission of nuclei that was induced by polarized cold neutrons were studied on the basis of quantum-mechanical fission theory. By using non-evaporation (nonadiabatic) mechanisms of light-particle emission, these coefficients were compared with the analogous coefficients for prescission third particles emitted in the ternary fission of nuclei.

  2. Study of ternary and quaternary spontaneous fission of sup 2 sup 5 sup 2 Cf with the NESSI detector

    E-print Network

    Tishchenko, V G; Hilscher, D; Jahnke, U

    2002-01-01

    Ternary and quaternary spontaneous decay of sup 2 sup 5 sup 2 Cf was studied with the NESSI detector, a combination of two 4 pi detectors for charged particles, neutrons and gamma-rays. The applied method of particle identification by measuring the energies and relative time-of-flights of the decay products is shown to be very effective for the study of rare decay modes. The energy and angular distributions of the decay products, the associated neutron multiplicities, the total energy of the prompt gamma-radiation as well as correlations between the various observables were measured for the first time in a single full-scale experiment. The characteristics of ternary fission known from previous investigations are confirmed in the frame of a methodically independent experiment. Preliminary estimates of the quaternary fission yield are presented. An attempt is made to determine the mechanism of quaternary fission.

  3. Probabilities for the emission of light particles and their energy and angular distributions for true quaternary nuclear fission

    SciTech Connect

    Kadmensky, S. G. Titova, L. V.

    2013-01-15

    On the basis of quantum-mechanical fission theory, the features of true quaternary nuclear fission are studied by treating this fission process as a sequence of three processes following one another in the course of time. The first two processes are the escape of the first and then the second of the two light particles emitted from the neck of a fissioning nucleus because of a nonadiabatic character of the collective deformation motion of this nucleus. Finally, the third process is the separation of the fissioning nucleus into two rather heavy fission fragments. The differences that arise in the emission probabilities and in the angular and energy distributions upon going over from the first emitted to the second emitted prescission third and fourth particles are analyzed by invoking experimental data on the spontaneous and thermalneutron-induced fission of nuclei, and it is shown that these differences are caused by the changes both in the geometric configuration of the fissioning nucleus and in the shell structure of its neck after the first prescission particle is emitted from it.

  4. The occurrence and fission-track ages of late neogene and quaternary volcanic sediments, Siwalik group, Northern Pakistan

    USGS Publications Warehouse

    Johnson, G.D.; Zeitler, P.; Naeser, C.W.; Johnson, N.M.; Summers, D.M.; Frost, C.D.; Opdyke, N.D.; Tahirkheli, R.A.K.

    1982-01-01

    Volcanic sediments, now mostly bentonites and bentonitic mudstones, occur throughout the Late Neogene and Quaternary Siwalik Group of northern Pakistan. A number of these deposits have been dated by the fission-track method, utilizing zircon phenocrysts from these deposits, and provide the chronometric constraints upon which a paleomagnetic stratigraphy is developed for the Siwalik Group. Notable in the occurrence of these altered tuff horizons is an apparent mode in their stratigraphic development from approximately 3.0 to 1.5 m.y. B.P. which coincides with the period of activity of the Dacht-e-Nawar volcanic complex of east-central Afghanistan. Fission-track ages of certain tuffs for critical areas of northern Pakistan are reported herein. ?? 1982.

  5. Fission-track evidence for Quaternary uplift of the Nanga Parbat region, Pakistan

    USGS Publications Warehouse

    Zeitler, P.K.; Johnson, N.M.; Naeser, C.W.; Tahirkheli, R.A.K.

    1982-01-01

    The north-striking Nanga Parbat-Haramosh Massif protrudes into the northwestern Himalaya along the axis of a great syntaxis1,2 (Fig. 1), where the Hindu Kush, Karakorum, and Himalayan ranges converge. As the Indus Suture Zone3 enters this region from the east it bifurcates into two branches, encircling what may be a docked island-arc terrane4. The southern branch (the Main Mantle Thrust) crops out on both flanks of the Nanga Parbat massif, forming a tight structural loop5. This massif and the adjacent terrane contain some of the highest peaks in the Himalaya; Nanga Parbat and the Indus River (located just 20km away) define the world's greatest continental relief (6,930 m). We report here the discovery of unexpectedly young sphene, zircon and apatite fission-track dates from the Nanga Parbat-Haramosh Massif. These dates (as low as 1.3 Myr for zircon and 0.4 Myr for apatite) imply that during the Pleistocene the Nanga Parbat region was uplifted and eroded at nearly 1 cm yr-1. ?? 1982 Nature Publishing Group.

  6. Deciphering Past and Present Tectonics of the Rio Grande Rift in New Mexico Utilizing Apatite Fission Track Thermochronology, Geochronology, Quaternary Faulting, and Cross-Section Restoration

    NASA Astrophysics Data System (ADS)

    Ricketts, J. W.; Karlstrom, K. E.; Kelley, S. A.; Priewisch, A.; Crossey, L. J.; Asmerom, Y.; Polyak, V.; Selmi, M.

    2011-12-01

    The Rio Grande rift provides an excellent laboratory for understanding styles and processes of extensional tectonics, and their driving forces. We apply apatite fission track (AFT) thermochronology, geochronology, fracture analysis, and cross-section restoration to decipher past and present tectonics of the Rio Grande rift. AFT data has been compiled from rift flank uplifts along the Rio Grande rift in an attempt to recognize long wavelength spatial and temporal patterns. AFT ages record time of cooling of rocks below ~110°C and, when cooling is due to exhumation, age elevation traverses can record upward advection of rocks through paleo 110°C isotherms. The relatively passive sides of half-grabens (e.g. Manzanos and Santa Fe Range) preserve Laramide AFT ages ranging from 45-70 Ma, indicating they were cooled during the Laramide Orogeny and have remained cooler than 110°C since then. Rift flanks on the tectonically active sides of half-grabens, (e.g. Sierra Ladrones, Sandias, Taos Range, and Sierra Blanca) have AFT ages that range from 35 Ma to <10 Ma, and record cooling that initiated with the Oligocene ignimbrite flare-up and continues through the Neogene. Our analysis tracks the approximate elevation of paleo 110°C isotherms in 10 Ma intervals from the Laramide to the present and shows that reconstructed paleoisotherms have been differentially uplifted, warped, and faulted since their time of formation, and hence serve as markers of uplift history and its mechanisms. AFT data at Ladron Peak, an active rift flank along the western margin of the Rio Grande rift in central New Mexico, indicates that it was rapidly unroofed between 20-10 Ma. Preliminary apatite helium data gives a similar age vs. elevation trend, but apatites have highly radiogenically damaged lattices and hence have corrected closure temperatures tens of degrees higher than AFT ages. The style of faulting at Ladron Peak is unusual because it is bounded by the anomalously low-angle (~15°) Jeter fault. In order to understand the evolution of faulting in this region, a balanced cross-section was constructed and restored to its pre-rift geometry. Our working hypothesis is that the low angle of the Jeter fault is most adequately explained by a rolling hinge model, where isostatic uplift causes progressive rotation of an initially steep (~60°) normal fault to shallower dips. Thirty km north of Ladron along the west side of the rift, Quaternary extensional faulting is evident in large travertine deposits at the Belen Quarry. Extensional fractures and cm-scale displacement normal faults at 4 locations give average paleostress orientations of 087, 112, 116, 127. A U-series age of 312 ka on faulted upper layers in one quarry indicates post-312 ka slip that we interpret to reflect surface manifestations of microseismicity above the Socorro magma body.

  7. Quaternary investigation

    SciTech Connect

    Stieve, A.

    1991-05-15

    The primary purpose of the Quaternary investigation is to provide information on the location and age of Quaternary deposits for use in evaluating the presence or absence of neotectonic deformation or paleoliquefaction features within the Savannah River Site (SRS) region. The investigation will provide a basis for evaluating the potential for capable faults and associated deformation in the SRS vicinity. Particular attention will be paid to the Pen Branch fault.

  8. Quaternary and Geomorphology.

    ERIC Educational Resources Information Center

    Andrews, J. T.; Graf, W. L.

    1983-01-01

    Highlights conferences and meetings of organizations involved with quaternary geology and geomorphology, including International Union of Quaternary Research Conference held in Moscow. The impetus of a revision of "The Quaternary of the United States" resulted from this conference. Includes activities/aims of "Friends of the Pleistocene"…

  9. Benchmarking Nuclear Fission Theory

    E-print Network

    G. F. Bertsch; W. Loveland; W. Nazarewicz; P. Talou

    2015-02-20

    We suggest a small set of fission observables to be used as test cases for validation of theoretical calculations. The purpose is to provide common data to facilitate the comparison of different fission theories and models. The proposed observables are chosen from fission barriers, spontaneous fission lifetimes, fission yield characteristics, and fission isomer excitation energies.

  10. Benchmarking nuclear fission theory

    SciTech Connect

    Bertsch, G. F.; Loveland, W.; Nazarewicz, W.; Talou, P.

    2015-05-14

    We suggest a small set of fission observables to be used as test cases for validation of theoretical calculations. Thus, the purpose is to provide common data to facilitate the comparison of different fission theories and models. The proposed observables are chosen from fission barriers, spontaneous fission lifetimes, fission yield characteristics, and fission isomer excitation energies.

  11. Benchmarking Nuclear Fission Theory

    E-print Network

    Bertsch, G F; Nazarewicz, W; Talou, P

    2015-01-01

    We suggest a small set of fission observables to be used as test cases for validation of theoretical calculations. The purpose is to provide common data to facilitate the comparison of different fission theories and models. The proposed observables are chosen from fission barriers, spontaneous fission lifetimes, fission yield characteristics, and fission isomer excitation energies.

  12. Bimodal fission

    SciTech Connect

    Hulet, E.K.

    1989-04-19

    In recent years, we have measured the mass and kinetic-energy distributions from the spontaneous fission of /sup 258/Fm, /sup 259/Md, /sup 260/Md, /sup 258/No, /sup 262/No, and /sup 260/(104). All are observed to fission with a symmetrical division of mass, whereas the total-kinetic-energy (TKE) distributions strongly deviated from the Gaussian shape characteristically found in the fission of all other actinides. When the TKE distributions are resolved into two Gaussians the constituent peaks lie near 200 and near 233 MeV. We conclude two modes or bimodal fission is occurring in five of the six nuclides studied. Both modes are possible in the same nuclides, but one generally predominates. We also conclude the low-energy but mass-symmetrical mode is likely to extend to far heavier nuclei; while the high-energy mode will be restricted to a smaller region, a region of nuclei defined by the proximity of the fragments to the strong neutron and proton shells in /sup 132/Sn. 16 refs., 7 figs., 1 tab.

  13. Fission meter

    DOEpatents

    Rowland, Mark S. (Alamo, CA); Snyderman, Neal J. (Berkeley, CA)

    2012-04-10

    A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source.

  14. B6) Quaternary Geology QUATERNARY GEOLOGY AND LANDFORMS BETWEEN

    E-print Network

    Briner, Jason P.

    The Quaternary geology and landforms in western New York State north of the southern Finger Lakes (Valley Heads recession across a scarp-dominated bedrock landscape from Batavia to the southern Lake Ontario shoreline. The complex sequence of proglacial lakes that accompanied glacial recession across the Great Lakes region

  15. Fission Xenon on Mars

    NASA Technical Reports Server (NTRS)

    Mathew, K. J.; Marti, K.; Marty, B.

    2002-01-01

    Fission Xe components due to Pu-244 decay in the early history of Mars have been identified in nakhlites; as in the case of ALH84001 and Chassigny the fission gas was assimilated into indigenous solar-type Xe. Additional information is contained in the original extended abstract.

  16. Fission gas detection system

    DOEpatents

    Colburn, Richard P. (Pasco, WA)

    1985-01-01

    A device for collecting fission gas released by a failed fuel rod which device uses a filter to pass coolant but which filter blocks fission gas bubbles which cannot pass through the filter due to the surface tension of the bubble.

  17. Robustness of Quaternary glacial cycles

    NASA Astrophysics Data System (ADS)

    Ganopolski, Andrei; Brovkin, Victor; Calov, Reinhard

    2015-04-01

    In spite of significant progress in paleoclimate reconstructions and modeling some aspects of Quaternary climate cycles are still poorly understood. Among them is the question of whether glacial cycles are deterministic and solely externally forced or, at least partially, they are stochastic. The answer to this question can only be obtained using a comprehensive Earth system models which incorporates all major components of the Earth system - atmosphere, ocean, land surface, northern hemisphere ice sheets, terrestrial biota and soil carbon, aeolian dust and marine biogeochemistry. Here, we used the Earth system model of intermediate complexity CLIMBER-2. The model was optimally tuned to reproduce climate, ice volume and CO2 variability for the last 0.8 million years. Using the same model version, we performed a large set of simulations covering the entire Quaternary (3 million years). By starting the model at different times (with the time step of 100,000 years) and using identical initial conditions we run the model for 500,000 years using the Earth's orbital variations as the only prescribed radiative forcing. We show that within less than 100,000 years after the beginning of each experiment the modeling results converge to the same solution which depends only on the orbital forcing and boundary conditions, such as topography and terrestrial sediment thickness for the ice sheets or volcanic CO2 outgassing for the carbon cycle. By using only several sets of the Northern Hemisphere orography and sediment thickness which represent different stages of landscape evolution during Quaternary, we are able to reproduce all major regimes of Quaternary long-term climate variability. Our results thus strongly support the notion that Quaternary glacial cycles are deterministic and externally forced.

  18. Biomodal spontaneous fission

    SciTech Connect

    Hulet, E.K. )

    1989-09-26

    Investigations of mass and kinetic-energy distributions from spontaneous fission have been extended in recent years to an isotope of element 104 and, for half-lives, to an isotope of element 108. The results have been surprising in that spontaneous fission half-lives have turned out to be much longer than expected and mass and kinetic- energy distributions were found to abruptly shift away from those of the lighter actinides, showing two modes of fission. These new developments have caused a re-evaluation of our understanding of the fission process, bringing an even deeper appreciation of the role played by nuclear shell effects upon spontaneous fission properties. 16 refs., 10 figs.

  19. Isomers in Fission Fragments

    SciTech Connect

    Urban, W.; Faust, H.; Jentschel, M.; Koester, U.; Krempel, J.; Materna, Th.; Mutti, P.; Soldner, T.; Genevey, J.; Pinston, J. A.; Simpson, G.; Sieja, K.; Nowacki, F.; Dorvaux, O.; Gall, B. J. P.; Roux, B.; Dare, J. A.

    2009-01-28

    The structure of neutron-rich nuclei produced as secondary fission fragments was investigated using the EUROGAM and GAMMASPHERE ACS arrays, the LOHENGRIN fission-fragment mass separator and the FIFI fission-fragment identifier. Fission products were populated in spontaneous fission of {sup 248}Cm and {sup 252}Cf and in thermal neutron-induced fission of {sup 233}U, {sup 235}U and {sup 241}Pu at ILL Grenoble. Particularly useful in such studies are isomeric states, well populated in fission due to their yrast character, easy to detect due to their long half lives and easy to interpret because of their relatively simple composition. We discuss their role in studies of neutron-rich nuclei, giving examples of isomers found in our recent experiments. A special type of K-isomers, resulting from 'crossing' of extruder and intruder orbitals plays a role in the mechanism of a sudden onset of deformation in the A = 100 and A = 150 regions. We present evidence for these isomers in both regions. Possible further studies in this field are proposed.

  20. Andrei Sher and Quaternary science

    NASA Astrophysics Data System (ADS)

    Kuzmina, Svetlana; Lister, Adrian M.; Edwards, Mary E.

    2011-08-01

    Andrei Sher (1939-2008) was a key individual in Beringian studies who made substantial and original contributions, but also, importantly, built bridges between western and eastern Beringian scientists spanning some five decades of research. He is perhaps best known as a Quaternary palaeontologist, specializing in large mammals, and mammoths in particular, but his field of his scientific research was much broader, encompassing Quaternary geology, stratigraphy, geocryology, and paleoenvironmental reconstructions. He worked mainly in Siberia, in the Kolyma and Indigirka lowlands, and Chukotka, but also completed fieldwork in Alaska and Yukon through joint projects with American and Canadian scientists. Andrei was an active scientist until the last days of his life. He was involved in many different research projects ranging from mammoth evolution, fossil insects and environmental changes and ancient DNA. Without Andrei's connections between researchers, many unique discoveries would likely be unknown.

  1. Quaternary ecology: A paleoecological perspective

    SciTech Connect

    Delcourt, H.R.; Delcourt, P.A.

    1991-01-01

    This book considers issues and problems in ecology which may be illuminated, if not solved, by considering paleoecology. The five central chapters include a discussion of application of Quaternary ecology to future global climate change, including global warming. Other areas presented include: population dispersal, invasions, expansions, and migrations; plant successions; ecotones; factors in community structure; ecosystem patterns and processes. Published case studies are numerous. The role played by continuing climatic change in vegetation change is acknowledged but not stressed.

  2. Fission Systems for Mars Exploration

    NASA Technical Reports Server (NTRS)

    Houts, Michael G.; Kim, T.; Dorney, D. J.; Swint, Marion Shayne

    2012-01-01

    Fission systems are used extensively on earth, and 34 such systems have flown in space. The energy density of fission is over 10 million times that of chemical reactions, giving fission the potential to eliminate energy density constraints for many space missions. Potential safety and operational concerns with fission systems are well understood, and strategies exist for affordably developing such systems. By enabling a power-rich environment and highly efficient propulsion, fission systems could enable affordable, sustainable exploration of Mars.

  3. Singlet fission photovoltaics

    E-print Network

    Lee, Jiye

    2013-01-01

    The efficiency of a solar cell is restricted by the "single junction limit," whereby photons with energy higher than the bandgap lose energy by thermalization. Singlet exciton fission splits a high-energy molecular excitation ...

  4. 40 CFR 721.10511 - Quaternary ammonium salts (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 false Quaternary ammonium salts (generic). 721.10511 Section 721...Substances § 721.10511 Quaternary ammonium salts (generic). (a) Chemical substance...identified generically as quaternary ammonium salts (PMNs P-07-320,...

  5. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  6. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 false Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  7. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2009-04-01 true Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  8. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  9. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  10. 40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Ethoxylated alkyl quaternary ammonium compound. 721.655 Section 721.655 ...Ethoxylated alkyl quaternary ammonium compound. (a) Chemical substance and significant...ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is subject...

  11. Singlet exciton fission photovoltaics.

    PubMed

    Lee, Jiye; Jadhav, Priya; Reusswig, Philip D; Yost, Shane R; Thompson, Nicholas J; Congreve, Daniel N; Hontz, Eric; Van Voorhis, Troy; Baldo, Marc A

    2013-06-18

    Singlet exciton fission, a process that generates two excitons from a single photon, is perhaps the most efficient of the various multiexciton-generation processes studied to date, offering the potential to increase the efficiency of solar devices. But its unique characteristic, splitting a photogenerated singlet exciton into two dark triplet states, means that the empty absorption region between the singlet and triplet excitons must be filled by adding another material that captures low-energy photons. This has required the development of specialized device architectures. In this Account, we review work to develop devices that harness the theoretical benefits of singlet exciton fission. First, we discuss singlet fission in the archetypal material, pentacene. Pentacene-based photovoltaic devices typically show high external and internal quantum efficiencies. They have enabled researchers to characterize fission, including yield and the impact of competing loss processes, within functional devices. We review in situ probes of singlet fission that modulate the photocurrent using a magnetic field. We also summarize studies of the dissociation of triplet excitons into charge at the pentacene-buckyball (C60) donor-acceptor interface. Multiple independent measurements confirm that pentacene triplet excitons can dissociate at the C60 interface despite their relatively low energy. Because triplet excitons produced by singlet fission each have no more than half the energy of the original photoexcitation, they limit the potential open circuit voltage within a solar cell. Thus, if singlet fission is to increase the overall efficiency of a solar cell and not just double the photocurrent at the cost of halving the voltage, it is necessary to also harvest photons in the absorption gap between the singlet and triplet energies of the singlet fission material. We review two device architectures that attempt this using long-wavelength materials: a three-layer structure that uses long- and short-wavelength donors and an acceptor and a simpler, two-layer combination of a singlet-fission donor and a long-wavelength acceptor. An example of the trilayer structure is singlet fission in tetracene with copper phthalocyanine inserted at the C60 interface. The bilayer approach includes pentacene photovoltaic cells with an acceptor of infrared-absorbing lead sulfide or lead selenide nanocrystals. Lead selenide nanocrystals appear to be the most promising acceptors, exhibiting efficient triplet exciton dissociation and high power conversion efficiency. Finally, we review architectures that use singlet fission materials to sensitize other absorbers, thereby effectively converting conventional donor materials to singlet fission dyes. In these devices, photoexcitation occurs in a particular molecule and then energy is transferred to a singlet fission dye where the fission occurs. For example, rubrene inserted between a donor and an acceptor decouples the ability to perform singlet fission from other major photovoltaic properties such as light absorption. PMID:23611026

  12. Late Quaternary history of the Atacama Desert

    E-print Network

    #12;#12;#12;#12;#12;73 Late Quaternary history of the Atacama Desert Claudio Latorre, Julio L and Kate Rylander Of the major subtropical deserts found in the Southern Hemisphere, the Atacama Desert is the driest. Throughout the Quaternary, the most pervasive climatic influence on the desert has been

  13. Ancient biomolecules in Quaternary palaeoecology

    NASA Astrophysics Data System (ADS)

    Hofreiter, Michael; Collins, Matthew; Stewart, John R.

    2012-02-01

    The last few years have seen an enormous proliferation of ancient biomolecules research, especially in the field of ancient DNA. Ancient DNA studies have been transformed by the advent of next generation sequencing, with the first Pleistocene sample being analysed in 2005, and several complete and draft genomes that have been compiled from ancient DNA to date. At the same time, although less conspicuous, research on ancient proteins has also seen advances, with the time limit for research on ancient biomolecules now extending to over 1 million years. Here we review which effects these developments have on research in Quaternary science. We identify several lines of research that have the potential to profit substantially from these recent developments in ancient biomolecules research. First, the identification of taxa can be made using ancient biomolecules, and in the case of ancient DNA, specimens can even be assigned to specific populations within a species. Second, increasingly large DNA data sets from Pleistocene animals allow the elucidation of ever more precise pictures of the population dynamic processes whereby organisms respond to climate and environmental change. With the accompanying better understanding of process in the Quaternary, past ecologies can also more realistically be interpreted from proxy data sets. The dominant message from this research so far is that the Quaternary saw a great deal more dynamism in populations than had been forecast by conventional palaeoecology. This suggests that reconstructions of past environmental conditions need to be done with caution. Third, ancient DNA can also now be obtained directly from sediments to elucidate the presence of both plant and animal species in an area even in the absence of identifiable fossils, be it macro- or micro-fossils. Finally, the analysis of proteins enables the identification of bone remains to genus and sometimes species level far beyond the survival time of DNA, at least in temperate regions, illustrating that precise data is now forthcoming from seemingly unlikely sources. Together, these approaches allow the study of environmental dynamics throughout a substantial part, and perhaps even the entire Quaternary (the last 2.6 million years).

  14. Process for treating fission waste

    DOEpatents

    Rohrmann, Charles A. (Kennewick, WA); Wick, Oswald J. (Richland, WA)

    1983-01-01

    A method is described for the treatment of fission waste. A glass forming agent, a metal oxide, and a reducing agent are mixed with the fission waste and the mixture is heated. After melting, the mixture separates into a glass phase and a metal phase. The glass phase may be used to safely store the fission waste, while the metal phase contains noble metals recovered from the fission waste.

  15. Microscopic Description of Induced Fission

    E-print Network

    N. Schunck

    2013-02-22

    Selected aspects of the description of neutron-induced fission in 240Pu in the framework of the nuclear energy density functional theory at finite temperature are presented. In particular, we discuss aspects pertaining to the choice of thermodynamic state variables, the evolution of fission barriers as function of the incident neutron energy, and the temperatures of the fission fragments.

  16. Student Experiments in Spontaneous Fission.

    ERIC Educational Resources Information Center

    Becchetti, F. D.; Ying, J. S.

    1981-01-01

    Advanced undergraduate experiments utilizing a commercially available, thin spontaneous fission source are described, including studies of the energy and mass distribution of the fission fragments and their energy and angular correlation. The experiments provide a useful introduction to fission, nuclear mass equations, heavy-ion physics, and…

  17. Elastocapillary Instability in Mitochondrial Fission.

    PubMed

    Gonzalez-Rodriguez, David; Sart, Sébastien; Babataheri, Avin; Tareste, David; Barakat, Abdul I; Clanet, Christophe; Husson, Julien

    2015-08-21

    Mitochondria are dynamic cell organelles that constantly undergo fission and fusion events. These dynamical processes, which tightly regulate mitochondrial morphology, are essential for cell physiology. Here we propose an elastocapillary mechanical instability as a mechanism for mitochondrial fission. We experimentally induce mitochondrial fission by rupturing the cell's plasma membrane. We present a stability analysis that successfully explains the observed fission wavelength and the role of mitochondrial morphology in the occurrence of fission events. Our results show that the laws of fluid mechanics can describe mitochondrial morphology and dynamics. PMID:26340213

  18. Elastocapillary Instability in Mitochondrial Fission

    NASA Astrophysics Data System (ADS)

    Gonzalez-Rodriguez, David; Sart, Sébastien; Babataheri, Avin; Tareste, David; Barakat, Abdul I.; Clanet, Christophe; Husson, Julien

    2015-08-01

    Mitochondria are dynamic cell organelles that constantly undergo fission and fusion events. These dynamical processes, which tightly regulate mitochondrial morphology, are essential for cell physiology. Here we propose an elastocapillary mechanical instability as a mechanism for mitochondrial fission. We experimentally induce mitochondrial fission by rupturing the cell's plasma membrane. We present a stability analysis that successfully explains the observed fission wavelength and the role of mitochondrial morphology in the occurrence of fission events. Our results show that the laws of fluid mechanics can describe mitochondrial morphology and dynamics.

  19. [Fission product yields of 60 fissioning reactions]. Final report

    SciTech Connect

    Rider, B.F.

    1995-05-01

    In keeping with the statement of work, I have examined the fission product yields of 60 fissioning reactions. In co-authorship with the UTR (University Technical Representative) Talmadge R. England ``Evaluation and Compilation of Fission Product Yields 1993,`` LA-UR-94-3106(ENDF-349) October, (1994) was published. This is an evaluated set of fission product Yields for use in calculation of decay heat curves with improved accuracy has been prepared. These evaluated yields are based on all known experimental data through 1992. Unmeasured fission product yields are calculated from charge distribution, pairing effects, and isomeric state models developed at Los Alamos National Laboratory. The current evaluation has been distributed as the ENDF/B-VI fission product yield data set.

  20. Quaternary Science Reviews 24 (2005) 19631968 Quaternary coastal morphology and sea-level

    E-print Network

    Laughlin, Robert B.

    2005-01-01

    Quaternary Science Reviews 24 (2005) 1963­1968 Editorial Quaternary coastal morphology and sea-level timescales. The position of sea level (ultimate base level) and changes of sea level over geological geomorphological and environmental change in adjacent landscapes. Sea level determines the lower limit

  1. Benchmarking the LAHET fission models

    SciTech Connect

    Prael, R.E.

    1995-12-31

    There has been considerable interest in improving the fission models in the LAHET Monte Carlo code for the transport and interaction of nucleons, pions, muons, fight ions, and antinucleons. Although subactinide fission contributes little to neutron production in lead or tungsten targets, it can be significant for simulation of target activation and fission product contamination. The availability of new data permits new comparisons to be made between experiment and calculation.

  2. The Irish quaternary fauna project

    NASA Astrophysics Data System (ADS)

    Woodman, Peter; Mccarthy, Margaret; Monaghan, Nigel

    Much of Ireland's Pleistocene and Early Holocene mammalian faunas are derived from a series of late 19th/early 20th century cave excavations. In many instances it would appear that the deposits containing these faunal remains were disturbed. This project assessed the chronological range of the mammalian species present in the caves using 14C dating, in particular accelerator mass spectrometry (AMS). The research has shown that (1) a wide range of mammals colonised Ireland in the period between at least 45 ka and 20 ka, with some elements surviving until close to the Last Glacial Maximum; (2) a more restricted range of species re-colonised Ireland during the Lateglacial period, with evidence for a slightly more temperature fauna being replaced by an Arctic fauna at about 11 ka; (3) certain elements of Ireland's Holocene fauna may have survived through from the Lateglacial into the Holocene; (4) there is a lack of evidence for red deer, Cervus elaphus, being present in the Early Holocene in Ireland; and (5) horse is only documented in the Irish Holocene from 4 ka. The paper also discusses the implications of the Quaternary Fauna Project for the Late Pleistocene of Ireland, the mechanism and period of colonisation of Ireland as well as the introduction of domesticates in the Mid Holocene.

  3. A Quaternary volcanic ash deposit in western Missouri

    SciTech Connect

    Emerson, J.W. )

    1993-03-01

    Quaternary volcanic ash has been found in more than fifty localities in the midwest. The most widespread deposits originated from the Long Valley caldera, California; the Jemez calderas, New Mexico; or the Yellowstone caldera, Wyoming. Fission track dating has grouped the deposits into six separate ash falls ranging from 700,000--2,000,000 years old. A small volcanic ash deposit in western Missouri may be correlative with those found along the Kansas and Marais de Cygnes rivers in eastern Kansas. The ash deposit is in Northwest Bates County Missouri, exposed along a tributary to Miami Creek, four miles east of the Kansas state line. The ash layer is interbedded with alluvial terrace deposits and ranges from fifteen to thirty inches in thickness. It is inferred to have been deposited in a pond or oxbow lake. The color is white with a pale yellow tinge (Munsell 10YR 8/2). Shard examination shows that about 70% are flat bubble-wall types, about 20% have straight ridges, less than 10% are bubble-junction, and only a trace are vesicular. The closest known volcanic ash occurrence is an ash outcropping in a Kansas river terrace near DeSoto, KS, forty-five miles to the northwest. The DeSoto deposit has been identified as the .62 m.y. Lava Creek B ash from the Yellowstone caldera. A preliminary correlation of the Missouri ash with the DeSoto ash is based on similar shard morphology and color.

  4. The SPIDER fission fragment spectrometer for fission product yield measurements

    NASA Astrophysics Data System (ADS)

    Meierbachtol, K.; Tovesson, F.; Shields, D.; Arnold, C.; Blakeley, R.; Bredeweg, T.; Devlin, M.; Hecht, A. A.; Heffern, L. E.; Jorgenson, J.; Laptev, A.; Mader, D.; O`Donnell, J. M.; Sierk, A.; White, M.

    2015-07-01

    The SPectrometer for Ion DEtermination in fission Research (SPIDER) has been developed for measuring mass yield distributions of fission products from spontaneous and neutron-induced fission. The 2E-2v method of measuring the kinetic energy (E) and velocity (v) of both outgoing fission products has been utilized, with the goal of measuring the mass of the fission products with an average resolution of 1 atomic mass unit (amu). The SPIDER instrument, consisting of detector components for time-of-flight, trajectory, and energy measurements, has been assembled and tested using 229Th and 252Cf radioactive decay sources. For commissioning, the fully assembled system measured fission products from spontaneous fission of 252Cf. Individual measurement resolutions were met for time-of-flight (250 ps FWHM), spacial resolution (2 mm FHWM), and energy (92 keV FWHM for 8.376 MeV). Mass yield results measured from 252Cf spontaneous fission products are reported from an E-v measurement.

  5. Measurement of Fission Product Yields from Fast-Neutron Fission

    NASA Astrophysics Data System (ADS)

    Arnold, C. W.; Bond, E. M.; Bredeweg, T. A.; Fowler, M. M.; Moody, W. A.; Rusev, G.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Henderson, R.; Kenneally, J.; Macri, R.; McNabb, D.; Ryan, C.; Sheets, S.; Stoyer, M. A.; Tonchev, A. P.; Bhatia, C.; Bhike, M.; Fallin, B.; Gooden, M. E.; Howell, C. R.; Kelley, J. H.; Tornow, W.

    2014-09-01

    One of the aims of the Stockpile Stewardship Program is a reduction of the uncertainties on fission data used for analyzing nuclear test data [1,2]. Fission products such as 147Nd are convenient for determining fission yields because of their relatively high yield per fission (about 2%) and long half-life (10.98 days). A scientific program for measuring fission product yields from 235U,238U and 239Pu targets as a function of bombarding neutron energy (0.1 to 15 MeV) is currently underway using monoenergetic neutron beams produced at the 10 MV Tandem Accelerator at TUNL. Dual-fission chambers are used to determine the rate of fission in targets during activation. Activated targets are counted in highly shielded HPGe detectors over a period of several weeks to identify decaying fission products. To date, data have been collected at neutron bombarding energies 4.6, 9.0, 14.5 and 14.8 MeV. Experimental methods and data reduction techniques are discussed, and some preliminary results are presented.

  6. Fission throughout the periodic table

    SciTech Connect

    Moretto, L.G.; Wozniak, G.J.

    1989-04-01

    The dualistic view of fission and evaporation as two distinct compound nucleus processes is substituted with a unified view in which fission, complex fragment emission, and light particle evaporation are seen as different aspects of a single process. 47 refs., 22 figs.

  7. Fission modes of mercury isotopes

    E-print Network

    M. Warda; A. Staszczak; W. Nazarewicz

    2012-07-17

    Background: Recent experiments on beta-delayed fission in the mercury-lead region and the discovery of asym- metric fission in 180 Hg [1] have stimulated theoretical interest in the mechanism of fission in heavy nuclei. Purpose: We study fission modes and fusion valleys in 180 Hg and 198 Hg to reveal the role of shell effects in pre-scission region and explain the experimentally observed fragment mass asymmetry and its variation with A. Methods: We use the self-consistent nuclear density functional theory employing Skyrme and Gogny energy density functionals. Results: The potential energy surfaces in multi-dimensional space of collective coordinates, including elongation, triaxiality, reflection-asymmetry, and necking, are calculated for 180 Hg and 198 Hg. The asymmetric fission valleys - well separated from fusion valleys associated with nearly spherical fragments - are found in in both cases. The density distributions at scission configurations are studied and related to the experimentally observed mass splits. Conclusions: The energy density functionals SkM\\ast and D1S give a very consistent description of the fission process in 180 Hg and 198 Hg. We predict a transition from asymmetric fission in 180 Hg towards more symmetric distribution of fission fragments in 198 Hg. For 180 Hg, both models yield 100 Ru/80 Kr as the most probable split. For 198 Hg, the most likely split is 108 Ru/90 Kr in HFB-D1S and 110 Ru/88 Kr in HFB-SkM\\ast.

  8. Fission Particle Emission Multiplicity Simulation

    Energy Science and Technology Software Center (ESTSC)

    2006-09-27

    Simulates discrete neutron and gamma-ray emission from the fission of heavy nuclei that is either spontaneous or neutron induced. This is a function library that encapsulates the fission physics and is intended to be called Monte Carlo transport code.

  9. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 false Tricyclic quaternary amine salt (generic). 721.10569 Section 721...721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance...generically as tricyclic quaternary amine salt (PMN P-08-471) is subject to...

  10. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with...

  11. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with...

  12. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tricyclic quaternary amine salt... Specific Chemical Substances § 721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance... tricyclic quaternary amine salt (PMN P-08-471) is subject to reporting under this section for...

  13. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tricyclic quaternary amine salt... Specific Chemical Substances § 721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance... tricyclic quaternary amine salt (PMN P-08-471) is subject to reporting under this section for...

  14. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Quaternary ammonium chloride combination. 172.165... § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride... the following compounds: n-dodecyl dimethyl benzyl ammonium chloride (CAS Reg. No. 139-07-1);...

  15. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with...

  16. The Fission Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Heffner, Mike

    2009-10-01

    New high-precision fission experiments have become a priority within the nuclear energy community due to a growing, world wide, interest in nuclear reactors. In particular, the designs of next generation reactors require reductions in the uncertainties on a number of energy dependent, neutron induced fission cross sections. The fission Time Projection Chamber (fission TPC) is the instrument that has been selected to carry out these challenging cross section measurements. This 6000 pad TPC with 2mm hex pads has a volume of only 2 liters and is filled with a hydrogen working gas. A unique set of electronics have been designed for the TPC that use all off the shelf components to reduce development costs. In this talk, I will show how the TPC will improve previous measurements, the design specifics of the fission TPC and the progress to date.

  17. Nuclear Fission Research at IRMM

    SciTech Connect

    Hambsch, Franz-Josef

    2005-05-24

    The Institute for Reference Materials and Measurements (IRMM) will celebrate its 45th anniversary in 2005. With its 150-MeV Geel Electron Linear Accelerator (GELINA) and 7-MV Van de Graaff accelerator as multi-purpose neutron sources, it served the nuclear physics community for this period.The research in the field of nuclear fission was focused in recent years on both the measurement and calculation of fission cross sections, and the measurement of fission fragment properties.Fission cross sections were determined for 233Pa and 234U; the fission process was studied in the resolved resonance region of 239Pu(n,f) and for 251Cf(nth,f). These measurements derive their interest from accelerator driven systems, the thorium fuel cycle, high temperature reactors, safety issues of current reactors, and basic physics. The measurements are supported by several modeling efforts that aim at improving model codes and nuclear data evaluation.

  18. A threshold for dissipative fission

    SciTech Connect

    Thoennessen, M.; Bertsch, G.F.

    1993-09-21

    The empirical domain of validity of statistical theory is examined as applied to fission data on pre-fission data on pre-fission neutron, charged particle, and {gamma}-ray multiplicities. Systematics are found of the threshold excitation energy for the appearance of nonstatistical fission. From the data on systems with not too high fissility, the relevant phenomenological parameter is the ratio of the threshold temperature T{sub thresh} to the (temperature-dependent) fission barrier height E{sub Bar}(T). The statistical model reproduces the data for T{sub thresh}/E{sub Bar}(T) < 0.26 {plus_minus} 0.05, but underpredicts the multiplicities at higher T{sub thresh}/E{sub Bar}(T) independent of mass and fissility of the systems.

  19. Catalytic enantioselective synthesis of quaternary carbon stereocentres

    NASA Astrophysics Data System (ADS)

    Quasdorf, Kyle W.; Overman, Larry E.

    2014-12-01

    Quaternary carbon stereocentres--carbon atoms to which four distinct carbon substituents are attached--are common features of molecules found in nature. However, before recent advances in chemical catalysis, there were few methods of constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for the synthesis of single stereoisomers of such organic molecules. This progress now makes it possible to incorporate quaternary stereocentres selectively in many organic molecules that are useful in medicine, agriculture and potentially other areas such as flavouring, fragrances and materials.

  20. Catalytic Enantioselective Synthesis of Quaternary Carbon Stereocenters

    PubMed Central

    Quasdorf, Kyle W.; Overman, Larry E.

    2015-01-01

    Preface Quaternary carbon stereocenters–carbon atoms to which four distinct carbon substituents are attached–are common features of molecules found in nature. However, prior to recent advances in chemical catalysis, there were few methods available for constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for synthesizing organic molecules containing such carbon atoms. This progress now makes it possible to selectively incorporate quaternary stereocenters in many high-value organic molecules for use in medicine, agriculture, and other areas. PMID:25503231

  1. Fifty years with nuclear fission

    SciTech Connect

    Behrens, J.W.; Carlson, A.D. )

    1989-01-01

    The news of the discovery of nuclear fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fifieth anniversary of its discovery by holding a topical meeting entitled, Fifty Years with Nuclear Fission,'' in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent development in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicated a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two fully days of sessions (April 27 and 28) at the main site of the NIST in Gaithersburg, Maryland. The wide range of topics covered in this Volume 1 by this topical meeting included plenary invited, and contributed sessions entitled: Preclude to the First Chain Reaction -- 1932 to 1942; Early Fission Research -- Nuclear Structure and Spontaneous Fission; 50 Years of Fission, Science, and Technology; Nuclear Reactors, Secure Energy for the Future; Reactors 1; Fission Science 1; Safeguards and Space Applications; Fission Data; Nuclear Fission -- Its Various Aspects; Theory and Experiments in Support of Theory; Reactors and Safeguards; and General Research, Instrumentation, and By-Product. The individual papers have been cataloged separately.

  2. Prompt Fission Neutron Emission in Resonance Fission of 239Pu

    SciTech Connect

    Hambsch, Franz-Josef; Oberstedt, Stephan; Varapai, Natallia; Serot, Olivier

    2005-05-24

    The prompt neutron emission probability from neutron-induced fission in the resonance region is being investigated at the time-of-flight facility GELINA of the IRMM. A double Frisch-gridded ionization chamber is used as a fission-fragment detector. For the data acquisition of both the fission-fragment signals as well as the neutron detector signals the fast digitization technique has been applied. For the neutron detection, large-volume liquid scintillation detectors from the DEMON collaboration are used. A specialized data analysis program taking advantage of the digital filtering technique has been developed to treat the acquired data.Neutron multiplicity investigations for actinides, especially in resonance neutron-induced fission, are rather scarce. They are, however, important for reactor control and safety issues as well as for understanding the basic physics of the fission process. Fission yield measurements on both 235U and 239Pu without prompt neutron emission coincidence have shown that fluctuation of the fission-fragment mass distribution exists from resonance to resonance, larger in the case of 235U. To possibly explain these observations, the question now is whether the prompt neutron multiplicity shows similar fluctuations with resonance energy.

  3. Arctic climates of the Quaternary

    NASA Astrophysics Data System (ADS)

    Spielhagen, R. F.; Bauch, H. A.; Frank, M.; Haley, B. A.

    2009-04-01

    The Atlantic Water (AW) inflow through the Fram Strait and across the Barents Sea and the freshwater runoff and brine rejection from sea ice formation on and close to the surrounding shelves are important processes for the formation of modern water masses in the interior Arctic Ocean. From microfossil and sedimentological data, isotopic data from planktic and benthic foraminifers, and 143Nd/144Nd ratios in leached sediment coatings from several well-dated Arctic sediment cores it is possible to reconstruct the variable influence of both processes on surface and intermediate waters in the Late Quaternary. Interglacials and interstadials were characterized by a broken sea ice cover with some open waters (leads) and a strong subsurface AW advection of Atlantic Water, feeding the deeper water masses. During the last ca. 250 ky such events usually were of a relatively short duration (10 ky or less), at times when the northern Eurasian shelves were ice-free. An exception is the last 50 ky interval, when a continuous inflow is recorded. Low Nd ratios indicate also a strong AW contribution to the intermediate waters since 50 ka and during MIS 5e. This conclusion is corroborated by high benthic carbon isotope values, indicative of well-ventilated waters at ca. 1500 m water depth. The good correlation between microfossil contents and insolation values suggests a dominant solar control of the AW inflow history. The time intervals of extended glaciations in northern Eurasia at ca. 190-130, 80-90, and 50-60 ka were characterized by a weak or lacking AW inflow and a strong input of terrestrial ice-rafted debris (IRD). Deglaciations were marked by strong influxes of freshwater from melting ice sheets and/or discharges from previously ice-dammed lakes. High Nd ratios indicate a significant contribution of brines from northern Siberian shelf/ice sheet margins to intermediate waters on the Lomonosov Ridge. The strongest freshwater events occurred at ca. 130 and 52 ka and resulted in an enhanced stratification of the upper water masses and poorly ventilated halocline and deep waters. While sediment records from the northernmost North Atlantic indicate a trend towards warmer peak interglacials and lesser IRD input during peak glacials in the last 500 ky, Arctic records do not reveal such a development. First strong IRD input occurred only during the Saalian glaciation, while earlier and even more extensive glaciations in northern Asia probably did not reach the Arctic paleo-coastline.

  4. Fifty years with nuclear fission

    SciTech Connect

    Behrens, J.W.; Carlson, A.D. )

    1989-01-01

    The news of the discovery of nucler fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fiftieth anniversary of its discovery by holding a topical meeting entitled, Fifty years with nuclear fission,'' in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent developments in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicating a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two full days of sessions (April 27 and 28) at the main sites of the NIST in Gaithersburg, Maryland. The wide range of topics covered by Volume 2 of this topical meeting included plenary invited, and contributed sessions entitled, Nuclear fission -- a prospective; reactors II; fission science II; medical and industrial applications by by-products; reactors and safeguards; general research, instrumentation, and by-products; and fission data, astrophysics, and space applications. The individual papers have been cataloged separately.

  5. Quaternary Geochronology 1 (2006) 7485 Research paper

    E-print Network

    Briner, Jason P.

    2006-01-01

    of complete shielding by the LIS. The lack of glacial erosion for at least the past 400 kyr suggests Island; Glacial history; Interglaciation; Erosion 1. Introduction The large-scale physiography of BaffinQuaternary Geochronology 1 (2006) 74­85 Research paper Limited ice-sheet erosion and complex

  6. Enantioselective construction of remote quaternary stereocentres

    NASA Astrophysics Data System (ADS)

    Mei, Tian-Sheng; Patel, Harshkumar H.; Sigman, Matthew S.

    2014-04-01

    Small molecules that contain all-carbon quaternary stereocentres--carbon atoms bonded to four distinct carbon substituents--are found in many secondary metabolites and some pharmaceutical agents. The construction of such compounds in an enantioselective fashion remains a long-standing challenge to synthetic organic chemists. In particular, methods for synthesizing quaternary stereocentres that are remote from other functional groups are underdeveloped. Here we report a catalytic and enantioselective intermolecular Heck-type reaction of trisubstituted-alkenyl alcohols with aryl boronic acids. This method provides direct access to quaternary all-carbon-substituted ?-, ?-, ?-, ?- or ?-aryl carbonyl compounds, because the unsaturation of the alkene is relayed to the alcohol, resulting in the formation of a carbonyl group. The scope of the process also includes incorporation of pre-existing stereocentres along the alkyl chain, which links the alkene and the alcohol, in which the stereocentre is preserved. The method described allows access to diverse molecular building blocks containing an enantiomerically enriched quaternary centre.

  7. FISSION AND FUSION Lecture 11.VII

    E-print Network

    Smith, Nathanael J.

    FISSION AND FUSION Lecture 11.VII #12;Review 2 Why does a system of nucleons form a nucleus, rather nucleon Overview 4 Tipler #12;Nuclear Fission Nuclear fission is a special type of nuclear reaction in which a heavy nucleus captures a neutron, and splits ("fissions") into two, roughly equal mass, products

  8. Background radiation from fission pulses

    SciTech Connect

    England, T.R.; Arthur, E.D.; Brady, M.C.; LaBauve, R.J.

    1988-05-01

    Extensive source terms for beta, gamma, and neutrons following fission pulses are presented in various tabular and graphical forms. Neutron results from a wide range of fissioning nuclides (42) are examined and detailed information is provided for four fuels: /sup 235/U, /sup 238/U, /sup 232/Th, and /sup 239/Pu; these bracket the range of the delayed spectra. Results at several cooling (decay) times are presented. For ..beta../sup -/ and ..gamma.. spectra, only /sup 235/U and /sup 239/Pu results are given; fission-product data are currently inadequate for other fuels. The data base consists of all known measured data for individual fission products extensively supplemented with nuclear model results. The process is evolutionary, and therefore, the current base is summarized in sufficient detail for users to judge its quality. Comparisons with recent delayed neutron experiments and total ..beta../sup -/ and ..gamma.. decay energies are included. 27 refs., 47 figs., 9 tabs.

  9. Singlet exciton fission in solution

    E-print Network

    Walker, Brian J.; Musser, Andrew J.; Beljonne, David; Friend, Richard H.

    2013-11-17

    Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley–Queisser limit in single-junction solar cells. Although the process through...

  10. Advanced Space Fission Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Houts, Michael G.; Borowski, Stanley K.

    2010-01-01

    Fission has been considered for in-space propulsion since the 1940s. Nuclear Thermal Propulsion (NTP) systems underwent extensive development from 1955-1973, completing 20 full power ground tests and achieving specific impulses nearly twice that of the best chemical propulsion systems. Space fission power systems (which may eventually enable Nuclear Electric Propulsion) have been flown in space by both the United States and the Former Soviet Union. Fission is the most developed and understood of the nuclear propulsion options (e.g. fission, fusion, antimatter, etc.), and fission has enjoyed tremendous terrestrial success for nearly 7 decades. Current space nuclear research and technology efforts are focused on devising and developing first generation systems that are safe, reliable and affordable. For propulsion, the focus is on nuclear thermal rockets that build on technologies and systems developed and tested under the Rover/NERVA and related programs from the Apollo era. NTP Affordability is achieved through use of previously developed fuels and materials, modern analytical techniques and test strategies, and development of a small engine for ground and flight technology demonstration. Initial NTP systems will be capable of achieving an Isp of 900 s at a relatively high thrust-to-weight ratio. The development and use of first generation space fission power and propulsion systems will provide new, game changing capabilities for NASA. In addition, development and use of these systems will provide the foundation for developing extremely advanced power and propulsion systems capable of routinely and affordably accessing any point in the solar system. The energy density of fissile fuel (8 x 10(exp 13) Joules/kg) is more than adequate for enabling extensive exploration and utilization of the solar system. For space fission propulsion systems, the key is converting the virtually unlimited energy of fission into thrust at the desired specific impulse and thrust-to-weight ratio. This presentation will discuss potential space fission propulsion options ranging from first generation systems to highly advanced systems. Ongoing research that shows promise for enabling second generation NTP systems with Isp greater than 1000 s will be discussed, as will the potential for liquid, gas, or plasma core systems. Space fission propulsion systems could also be used in conjunction with simple (water-based) propellant depots to enable routine, affordable missions to various destinations (e.g. moon, Mars, asteroids) once in-space infrastructure is sufficiently developed. As fuel and material technologies advance, very high performance Nuclear Electric Propulsion (NEP) systems may also become viable. These systems could enable sophisticated science missions, highly efficient cargo delivery, and human missions to numerous destinations. Commonalities between NTP, fission power systems, and NEP will be discussed.

  11. The microscopic theory of fission

    E-print Network

    W. Younes; D. Gogny

    2009-10-09

    Fission-fragment properties have been calculated for thermal neutron-induced fission on a $^{239}\\textrm{Pu}$ target, using constrained Hartree-Fock-Bogoliubov calculations with a finite-range effective interaction. A quantitative criterion based on the interaction energy between the nascent fragments is introduced to define the scission configurations. The validity of this criterion is benchmarked against experimental measurements of the kinetic energies and of multiplicities of neutrons emitted by the fragments.

  12. The Quaternary impact record from the Pampas, Argentina

    NASA Astrophysics Data System (ADS)

    Schultz, Peter H.; Zárate, Marcelo; Hames, Bill; Koeberl, Christian; Bunch, Theodore; Storzer, Dieter; Renne, Paul; Wittke, James

    2004-03-01

    Loess-like deposits cover much of central Argentina and preserve a rich record of impacts since the late Miocene. The present contribution focuses on two localities containing Quaternary impact glasses: along the coastal sequences near Centinela del Mar (CdM) and from near Rio Cuarto (RC). These highly vesicular glasses contain clear evidence for an impact origin including temperatures sufficient to melt most mineral constituents (1700°C) and to leave unique quench products such as ?-cristobolite. The CdM glasses occur within a relatively narrow horizon just below a marine transgression expressed by a series of coastal paleo-dunes and systematic changes in the underlying sediments. High-resolution 40Ar/39Ar dating methods yielded an age of 445±21 ka (2?). Glasses were also recovered from scattered occurrences lower in the section but were dated to 230±40 ka. This inconsistency between stratigraphic and radiometric age is most likely related to a nearby outcrop of glass that had been exposed and locally re-deposited in coastal lagoons during the last marine transgression at 125 ka. Sediments containing the original impact glass layer are now missing due to an unconformity, perhaps related to subsequent marine transgressions after the impact (410 ka and 340 ka) and hiatuses in deposition. Two different types of impact glasses from RC yield two distinct dates. High-resolution 40Ar/39Ar dating of fresher-appearing glasses (well-preserved tachylitic sheen) indicates an age of 6±2 ka (2?). Independent fission track analyses yielded a similar age of 2.3±1.6 ka (2?). More weathered glasses, however, gave significantly older ages of 114±26 ka (2?). Consequently, materials from two separate Quaternary impacts have been recovered at Rio Cuarto. The younger glasses are consistent with previously reported carbon dates for materials on the floor of one of the large elongate structures. The depths of excavation for the RC and CdM impacts are very different. While the RC glasses are largely derived from near-surface materials, the CdM glasses from the upper level contain added components consistent with Miocene marine evaporites at a depth of about 400-500 m (e.g., high CaO and P2O5). The CdM glasses also incorporated older loess-like sediments from depth based on the geochemistry. Several ratios of key trace and rare earth elements of sediments of different ages from the Miocene to the Holocene indicate a systematic compositional change through time. Such changes calibrate the observed differences in glass composition from their host sediments and further indicate incorporation of materials from depth. Consequently, the Argentine loess-like sediments preserve evidence for at least four separate Quaternary impacts. Based on foreign components in the glasses, the CdM impact very likely produced a crater (now buried or eroded) once as large as 6 km in diameter. The younger RC glasses, however, are consistent with shallower excavation consistent with an oblique impact.

  13. 40Ar/39Ar dating of Quaternary feldspar: examples from the Taupo Volcanic Zone, New Zealand

    USGS Publications Warehouse

    Pringle, M.S.; McWilliams, M.; Houghton, B.F.; Lanphere, M.A.; Wilson, C.J.N.

    1992-01-01

    Using a continuous laser and resistance furnace, we have measured ages on Quaternary plagioclase with an absolute precision of about ??30 ka and on Quaternary sanidine with a relative precision of better than 1%. Such precision was achieved by using low-temperature heating steps to remove much of the nonradiogenic argon contamination. Plagioclase is one of the most common mineral phases in volcanic rocks; thus, these procedures will be widely applicable to many problems for which precise radiometric age control has not been available. We studied plagioclase and plagioclase-sanidine concentrates from the oldest and the three largest silicic ash-flow deposits of the Taupo Volcanic Zone, New Zealand, one of the world's largest and most active volcanic systems. The results are in close agreement with new magnetostratigraphic data, suggesting that existing fission-track age determinations significantly underestimate the age of older units, and shift the inception of Taupo Vaolcanic Zone volcanism back to at least 1600 ka. -from Authors

  14. Quaternary glaciations in the Northern Hemisphere

    SciTech Connect

    Sibrava, V.; Bowen, D.Q.; Richmond, G.M.

    1987-01-01

    This volume presents the final report of Project 24 of the International Geological Correlation Programme. The publication is drawn from the contributions of leading individual scientist as well as from scientific research teams. It reflects the present state of knowledge of the Quaternary Glaciations in the Northern Hemisphere and their correlation in space and time, as well as providing a unique summary of climatic change.

  15. Fission product solvent extraction

    SciTech Connect

    Moyer, B.A.; Bonnesen, P.V.; Sachleben, R.A.

    1998-02-01

    Two main objectives concerning removal of fission products from high-level tank wastes will be accomplished in this project. The first objective entails the development of an acid-side Cs solvent-extraction (SX) process applicable to remediation of the sodium-bearing waste (SBW) and dissolved calcine waste (DCW) at INEEL. The second objective is to develop alkaline-side SX processes for the combined removal of Tc, Cs, and possibly Sr and for individual separation of Tc (alone or together with Sr) and Cs. These alkaline-side processes apply to tank wastes stored at Hanford, Savannah River, and Oak Ridge. This work exploits the useful properties of crown ethers and calixarenes and has shown that such compounds may be economically adapted to practical processing conditions. Potential benefits for both acid- and alkaline-side processing include order-of-magnitude concentration factors, high rejection of bulk sodium and potassium salts, and stripping with dilute (typically 10 mM) nitric acid. These benefits minimize the subsequent burden on the very expensive vitrification and storage of the high-activity waste. In the case of the SRTALK process for Tc extraction as pertechnetate anion from alkaline waste, such benefits have now been proven at the scale of a 12-stage flowsheet tested in 2-cm centrifugal contactors with a Hanford supernatant waste simulant. SRTALK employs a crown ether in a TBP-modified aliphatic kerosene diluent, is economically competitive with other applicable separation processes being considered, and has been successfully tested in batch extraction of actual Hanford double-shell slurry feed (DSSF).

  16. DNA Barcoding through Quaternary LDPC Codes

    PubMed Central

    Tapia, Elizabeth; Spetale, Flavio; Krsticevic, Flavia; Angelone, Laura; Bulacio, Pilar

    2015-01-01

    For many parallel applications of Next-Generation Sequencing (NGS) technologies short barcodes able to accurately multiplex a large number of samples are demanded. To address these competitive requirements, the use of error-correcting codes is advised. Current barcoding systems are mostly built from short random error-correcting codes, a feature that strongly limits their multiplexing accuracy and experimental scalability. To overcome these problems on sequencing systems impaired by mismatch errors, the alternative use of binary BCH and pseudo-quaternary Hamming codes has been proposed. However, these codes either fail to provide a fine-scale with regard to size of barcodes (BCH) or have intrinsic poor error correcting abilities (Hamming). Here, the design of barcodes from shortened binary BCH codes and quaternary Low Density Parity Check (LDPC) codes is introduced. Simulation results show that although accurate barcoding systems of high multiplexing capacity can be obtained with any of these codes, using quaternary LDPC codes may be particularly advantageous due to the lower rates of read losses and undetected sample misidentification errors. Even at mismatch error rates of 10?2 per base, 24-nt LDPC barcodes can be used to multiplex roughly 2000 samples with a sample misidentification error rate in the order of 10?9 at the expense of a rate of read losses just in the order of 10?6. PMID:26492348

  17. Energy production using fission fragment rockets

    SciTech Connect

    Chapline, G.; Matsuda, Y.

    1991-08-01

    Fission fragment rockets are nuclear reactors with a core consisting of thin fibers in a vacuum, and which use magnetic fields to extract the fission fragments from the reactor core. As an alternative to ordinary nuclear reactors, fission fragment rockets would have the following advantages: Approximately twice as efficient if one can directly convert the fission fragment energy into electricity; by reducing the buildup of a fission fragment inventory in the reactor one could avoid a Chernobyl type disaster; and collecting the fission fragments outside the reactor could simplify the waste disposal problem. 6 refs., 4 figs., 2 tabs.

  18. Assessment of fissionable material behaviour in fission chambers

    NASA Astrophysics Data System (ADS)

    Cabellos, O.; Fernández, P.; Rapisarda, D.; García-Herranz, N.

    2010-06-01

    A comprehensive study is performed in order to assess the pertinence of fission chambers coated with different fissile materials for high neutron flux detection. Three neutron scenarios are proposed to study the fast component of a high neutron flux: (i) high neutron flux with a significant thermal contribution such as BR2, (ii) DEMO magnetic fusion reactor, and (iii) IFMIF high flux test module. In this study, the inventory code ACAB is used to analyze the following questions: (i) impact of different deposits in fission chambers; (ii) effect of the irradiation time/burn-up on the concentration; (iii) impact of activation cross-section uncertainties on the composition of the deposit for all the range of burn-up/irradiation neutron fluences of interest. The complete set of nuclear data (decay, fission yield, activation cross-sections, and uncertainties) provided in the EAF2007 data library are used for this evaluation.

  19. Compact fission counter for DANCE

    SciTech Connect

    Wu, C Y; Chyzh, A; Kwan, E; Henderson, R; Gostic, J; Carter, D; Bredeweg, T; Couture, A; Jandel, M; Ullmann, J

    2010-11-06

    The Detector for Advanced Neutron Capture Experiments (DANCE) consists of 160 BF{sub 2} crystals with equal solid-angle coverage. DANCE is a 4{pi} {gamma}-ray calorimeter and designed to study the neutron-capture reactions on small quantities of radioactive and rare stable nuclei. These reactions are important for the radiochemistry applications and modeling the element production in stars. The recognition of capture event is made by the summed {gamma}-ray energy which is equivalent of the reaction Q-value and unique for a given capture reaction. For a selective group of actinides, where the neutron-induced fission reaction competes favorably with the neutron capture reaction, additional signature is needed to distinguish between fission and capture {gamma} rays for the DANCE measurement. This can be accomplished by introducing a detector system to tag fission fragments and thus establish a unique signature for the fission event. Once this system is implemented, one has the opportunity to study not only the capture but also fission reactions. A parallel-plate avalanche counter (PPAC) has many advantages for the detection of heavy charged particles such as fission fragments. These include fast timing, resistance to radiation damage, and tolerance of high counting rate. A PPAC also can be tuned to be insensitive to {alpha} particles, which is important for experiments with {alpha}-emitting actinides. Therefore, a PPAC is an ideal detector for experiments requiring a fast and clean trigger for fission. A PPAC with an ingenious design was fabricated in 2006 by integrating amplifiers into the target assembly. However, this counter was proved to be unsuitable for this application because of issues related to the stability of amplifiers and the ability to separate fission fragments from {alpha}'s. Therefore, a new design is needed. A LLNL proposal to develop a new PPAC for DANCE was funded by NA22 in FY09. The design goal is to minimize the mass for the proposed counter and still be able to maintain a stable operation under extreme radioactivity and the ability to separate fission fragments from {alpha}'s. In the following sections, the description is given for the design and performance of this new compact PPAC, for studying the neutron-induced reactions on actinides using DANCE at LANL.

  20. Thorium-uranium fission radiography

    NASA Technical Reports Server (NTRS)

    Haines, E. L.; Weiss, J. R.; Burnett, D. S.; Woolum, D. S.

    1976-01-01

    Results are described for studies designed to develop routine methods for in-situ measurement of the abundance of Th and U on a microscale in heterogeneous samples, especially rocks, using the secondary high-energy neutron flux developed when the 650 MeV proton beam of an accelerator is stopped in a 42 x 42 cm diam Cu cylinder. Irradiations were performed at three different locations in a rabbit tube in the beam stop area, and thick metal foils of Bi, Th, and natural U as well as polished silicate glasses of known U and Th contents were used as targets and were placed in contact with mica which served as a fission track detector. In many cases both bare and Cd-covered detectors were exposed. The exposed mica samples were etched in 48% HF and the fission tracks counted by conventional transmitted light microscopy. Relative fission cross sections are examined, along with absolute Th track production rates, interaction tracks, and a comparison of measured and calculated fission rates. The practicality of fast neutron radiography revealed by experiments to data is discussed primarily for Th/U measurements, and mixtures of other fissionable nuclei are briefly considered.

  1. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 false Quaternary ammonium salt of fluorinated alkylaryl amide. 721...Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl amide. ...identified generically as quaternary ammonium salt of fluorinated alkylaryl amide...

  2. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 false Quaternary ammonium salt of fluorinated alkylaryl amide. 721...Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl amide. ...identified generically as quaternary ammonium salt of fluorinated alkylaryl amide...

  3. Quaternary Geologic Map of Connecticut and Long Island Sound Basin

    USGS Publications Warehouse

    Stone, Janet Radway; Schafer, John P.; London, Elizabeth Haley; DiGiacomo-Cohen, Mary L.; Lewis, Ralph S.; Thompson, Woodrow B.

    2005-01-01

    The Quaternary geologic map (sheet 1) and explanatory figures and cross sections (sheet 2) portray the geologic features formed in Connecticut during the Quaternary Period, which includes the Pleistocene (glacial) and Holocene (postglacial) Epochs. The Quaternary Period has been a time of development of many details of the landscape and of all the surficial deposits. At least twice in the late Pleistocene, continental ice sheets swept across Connecticut. Their effects are of pervasive importance to the present occupants of the land. The Quaternary geologic map illustrates the geologic history and the distribution of depositional environments during the emplacement of glacial and postglacial surficial deposits and the landforms resulting from those events.

  4. Cranking mass parameters for fission

    E-print Network

    M. Mirea; R. C. Bobulescu

    2009-09-11

    A formalism for semi-adiabatic cranking mass parameters is presented. For the fission process of 234U, the time-dependent pairing equations of motion were used to calculate the excitation energy and to extract values of the cranking inertia. A fission barrier is determined by minimizing the action trajectory in a five dimensional configuration space spanned by elongation, necking, deformations of fragments and mass-asymmetry. The deformation energy is computed in the the frame of the microscopic-macroscopic model. The two center shell model with Woods-Saxon potentials is used in this context. Values of the inertia for excited fissioning systems are reported. A dependence between the cranking mass parameters and the intrinsic excitation energy is evidenced.

  5. Fission properties of the heaviest elements

    SciTech Connect

    Moller, P. |||; Nix, R.

    1995-03-01

    The authors discuss fission properties of the heaviest elements. In particular they focus on stability with respect to spontaneous fission and on the prospects of extending the region of known nuclei beyond the peninsula of currently known nuclides.

  6. Quantum efficiency and fission rate in tetracene

    E-print Network

    Wu, Tony Chang-Chi

    2013-01-01

    Using singlet fission in a photovoltaic cell, the theoretical energy conversion efficiency limit is larger than the Shockley-Queisser limit due to two excitons produced with one incident photon. In a singlet fission material, ...

  7. Mitochondrial Fusion and Fission in Mammals

    E-print Network

    Chan, David

    Mitochondrial Fusion and Fission in Mammals David C. Chan Division of Biology, California Institute dynamics, organelle morphology, membrane fusion, membrane trafficking Abstract Eukaryotic cells maintain. Unbalanced fission leads to mitochondrial fragmentation, and un- balanced fusion leads to mitochondrial

  8. Search for Singlet Fission Chromophores

    SciTech Connect

    Havlas, Z.; Akdag, A.; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, J.

    2012-01-01

    Singlet fission, in which a singlet excited chromophore shares its energy with a ground-state neighbor and both end up in their triplet states, is of potential interest for solar cells. Only a handful of compounds, mostly alternant hydrocarbons, are known to perform efficiently. In view of the large number of conditions that a successful candidate for a practical cell has to meet, it appears desirable to extend the present list of high performers to additional classes of compounds. We have (i) identified design rules for new singlet fission chromophores and for their coupling to covalent dimers, (ii) synthesized them, and (iii) evaluated their performance as neat solids or covalent dimers.

  9. Velocity fluctuations of fission fragments

    E-print Network

    Llanes-Estrada, Felipe J; Martinez, Jose L Muñoz

    2015-01-01

    We propose event by event velocity fluctuations of nuclear fission fragments as an additional interesting observable that gives access to the nuclear temperature in an independent way from spectral measurements and relates the diffusion and friction coefficients for the relative fragment coordinate in Kramer-like models (in which some aspects of fission can be understood as the diffusion of a collective variable through a potential barrier). We point out that neutron emission by the heavy fragments can be treated in effective theory if corrections to the velocity distribution are needed.

  10. Velocity fluctuations of fission fragments

    E-print Network

    Felipe J. Llanes-Estrada; Belen Martinez Carmona; Jose L. Muñoz Martinez

    2015-11-19

    We propose event by event velocity fluctuations of nuclear fission fragments as an additional interesting observable that gives access to the nuclear temperature in an independent way from spectral measurements and relates the diffusion and friction coefficients for the relative fragment coordinate in Kramer-like models (in which some aspects of fission can be understood as the diffusion of a collective variable through a potential barrier). We point out that neutron emission by the heavy fragments can be treated in effective theory if corrections to the velocity distribution are needed.

  11. Neutronics for critical fission reactors and subcritical fission in hybrids

    SciTech Connect

    Salvatores, Massimo

    2012-06-19

    The requirements of future innovative nuclear fuel cycles will focus on safety, sustainability and radioactive waste minimization. Critical fast neutron reactors and sub-critical, external source driven systems (accelerator driven and fusion-fission hybrids) have a potential role to meet these requirements in view of their physics characteristics. This paper provides a short introduction to these features.

  12. Spontaneous fission properties of the heavy elements: Bimodal fission

    SciTech Connect

    Hulet, E.K.

    1988-11-11

    We have measured the mass and kinetic-energy distributions from the spontaneous fission of SVYFm, SVYNo, SVZMd, SWMd, SW(104), and SWSNo. All are observed to fission with a symmetrical division of mass, whereas the total-kinetic-energy (TKE) distributions strongly deviated from the Gaussian shape characteristically found in the fission of all other actinides. When the TKE distributions are resolved into two Gaussian's, the constituent peaks lie near 200 and near 233 MeV. We conclude two modes or bimodal fission is occurring in five of the six nuclides studied. Both modes are possible in the same nuclide, but one generally predominates. We also conclude the low-energy but mass-symmetrical mode is likely to extend to far heavier nuclei; while the high-energy mode will be restricted to a smaller region, a region of nuclei defined by the proximity of the fragments to the strong neutron and proton shells in TSSn. 21 refs., 7 figs., 1 tab.

  13. Neutronics for critical fission reactors and subcritical fission in hybrids

    NASA Astrophysics Data System (ADS)

    Salvatores, Massimo

    2012-06-01

    The requirements of future innovative nuclear fuel cycles will focus on safety, sustainability and radioactive waste minimization. Critical fast neutron reactors and sub-critical, external source driven systems (accelerator driven and fusion-fission hybrids) have a potential role to meet these requirements in view of their physics characteristics. This paper provides a short introduction to these features.

  14. Nuclear fission in covariant density functional theory

    E-print Network

    A. V. Afanasjev; H. Abusara; P. Ring

    2013-09-12

    The current status of the application of covariant density functional theory to microscopic description of nuclear fission with main emphasis on superheavy nuclei (SHN) is reviewed. The softness of SHN in the triaxial plane leads to an emergence of several competing fission pathes in the region of the inner fission barrier in some of these nuclei. The outer fission barriers of SHN are considerably affected both by triaxiality and octupole deformation.

  15. Process for treating fission waste. [Patent application

    DOEpatents

    Rohrmann, C.A.; Wick, O.J.

    1981-11-17

    A method is described for the treatment of fission waste. A glass forming agent, a metal oxide, and a reducing agent are mixed with the fission waste and the mixture is heated. After melting, the mixture separates into a glass phase and a metal phase. The glass phase may be used to safely store the fission waste, while the metal phase contains noble metals recovered from the fission waste.

  16. Fission for Program Comprehension Jeremy Gibbons

    E-print Network

    Gibbons, Jeremy

    Fission for Program Comprehension Jeremy Gibbons Oxford University Computing Laboratory Wolfson at the cost of clarity. Fission is the same transformation, in reverse: creating structure, ex nihilo. We explore the use of fission for program comprehension, that is, for reconstructing the design of a program

  17. Renew Workshop on Fusion-Fission Hybrids

    E-print Network

    1 Renew Workshop on Fusion-Fission Hybrids Jeff Freidberg (MIT) Chair Phillip Finck (INL) Co and fission From universities, labs, government and industry #12;5 The Workshop (cont) First morning plenary contributed Technical findings #12;7 Status of Nuclear Power Fission View Components of nuclear power Fuel

  18. New Quaternary Low Correlation Zone Sequences Sang-Hyo Kim

    E-print Network

    No, Jong-Seon

    New Quaternary Low Correlation Zone Sequences Sang-Hyo Kim Wireless Device Solution Team Telecomm. R&D Center Samsung Electronics Suwon, Korea sanghyo7.kim@samsung.com Ji-Woong Jang, Kyoung-Young n, we propose a method of constructing quaternary low correlation zone(LCZ) sequences of period 2n

  19. 40 CFR 721.10511 - Quaternary ammonium salts (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Quaternary ammonium salts (generic... Specific Chemical Substances § 721.10511 Quaternary ammonium salts (generic). (a) Chemical substance and... ammonium salts (PMNs P-07-320, P-07-321, P-07-322, P-07-323, and P-07-324) are subject to reporting...

  20. 40 CFR 721.10511 - Quaternary ammonium salts (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Quaternary ammonium salts (generic... Specific Chemical Substances § 721.10511 Quaternary ammonium salts (generic). (a) Chemical substance and... ammonium salts (PMNs P-07-320, P-07-321, P-07-322, P-07-323, and P-07-324) are subject to reporting...

  1. Surface Micellization Patterns of Quaternary Ammonium Surfactants on Mica

    E-print Network

    Aksay, Ilhan A.

    Surface Micellization Patterns of Quaternary Ammonium Surfactants on Mica Heather N. Patrick equilibrium structures of adsorbed films of quaternary ammonium surfactants on mica have been investigated never been reported on graphite. Mica is a model hydrophilic surface and has been previously used

  2. Space Fission System Test Effectiveness

    NASA Astrophysics Data System (ADS)

    Houts, Mike; Schmidt, Glen L.; van Dyke, Melissa; Godfroy, Tom; Martin, James; Bragg-Sitton, Shannon; Dickens, Ricky; Salvail, Pat; Harper, Roger

    2004-02-01

    Space fission technology has the potential to enable rapid access to any point in the solar system. If fission propulsion systems are to be developed to their full potential, however, near-term customers need to be identified and initial fission systems successfully developed, launched, and utilized. One key to successful utilization is to develop reactor designs that are highly testable. Testable reactor designs have a much higher probability of being successfully converted from paper concepts to working space hardware than do designs which are difficult or impossible to realistically test. ``Test Effectiveness'' is one measure of the ability to realistically test a space reactor system. The objective of this paper is to discuss test effectiveness as applied to the design, development, flight qualification, and acceptance testing of space fission systems. The ability to perform highly effective testing would be particularly important to the success of any near-term mission, such as NASA's Jupiter Icy Moons Orbiter, the first mission under study within NASA's Project Prometheus, the Nuclear Systems Program.

  3. Etching fission tracks in zircons

    USGS Publications Warehouse

    Naeser, C.W.

    1969-01-01

    A new technique has been developed whereby fission tracks can be etched in zircon with a solution of sodium hydroxide at 220??C. Etching time varied between 15 minutes and 5 hours. Colored zircon required less etching time than the colorless varieties.

  4. Quaternary vertebrates from Greenland: A review

    NASA Astrophysics Data System (ADS)

    Bennike, Ole

    Remains of fishes, birds and mammals are rarely reported from Quaternary deposits in Greenland. The oldest remains come from Late Pliocene and Early Pleistocene deposits and comprise Atlantic cod, hare, rabbit and ringed seal. Interglacial and interstadial deposits have yielded remains of cod, little auk, collared lemming, ringed seal, reindeer and bowhead whale. Early and Mid-Holocene finds include capelin, polar cod, red fish, sculpin, three-spined stickleback, Lapland longspur, Arctic hare, collared lemming, wolf, walrus, ringed seal, reindeer and bowhead whale. It is considered unlikely that vertebrates could survive in Greenland during the peak of the last glaciation, but many species had probably already immigrated in the Early Holocene.

  5. Space Fission Propulsion System Development Status

    NASA Technical Reports Server (NTRS)

    Houts, Mike; VanDyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Williams, Eric; Harper, Roger; Salvail, Pat; Hrbud, Ivana; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    The world's first man-made self-sustaining fission reaction was achieved in 1942. Since then fission has been used to propel submarines, generate tremendous amounts of electricity, produce medical isotopes, and provide numerous other benefits to society. Fission systems operate independently of solar proximity or orientation, and are thus well suited for deep spare or planetary surface missions. In addition, the fuel for fission systems (enriched uranium) is virtually non-radioactive. The primary safety issue with fission systems is avoiding inadvertent system start - addressing this issue through proper system design is straightforward. Despite the relative simplicity and tremendous potential of space fission systems, the development and utilization of these systems has proven elusive. The first use of fission technology in space occurred 3 April 1965 with the US launch of the SNAP-10A reactor. There have been no additional US uses of space fission system. While space fission system were used extensively by the former Soviet Union, their application was limited to earth-orbital missions. Early space fission systems must be safely and affordably utilized if Ae are to reap the benefits of advanced space fission systems.

  6. Fission dynamics at low excitation energy

    E-print Network

    Y. Aritomo; S. Chiba

    2013-10-14

    The origin of mass asymmetry in the fission of uranium at a low excitation energy is clarified by a trajectory analysis of the Langevin equation. The positions of the peaks in the mass distribution of fission fragments are mainly determined by fission saddle points originating from the shell correction energy. The widths of the peaks, on the other hand, result from a shape fluctuation around the scission point caused by the random force in the Langevin equation. We found that a random vibration in the oblate direction of fissioning fragments is essential for the fission process. According to this picture, fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup. This is expected to lead to a new viewpoint of fission dynamics and the splitting mechanism.

  7. Space Fission Propulsion System Development Status

    NASA Technical Reports Server (NTRS)

    Houts, M.; Van Dyke, M. K.; Godfroy, T. J.; Pedersen, K. W.; Martin, J. J.; Dickens, R.; Williams, E.; Harper, R.; Salvail, P.; Hrbud, I.

    2001-01-01

    The world's first man-made self-sustaining fission reaction was achieved in 1942. Since then fission has been used to propel submarines, generate tremendous amounts of electricity, produce medical isotopes, and provide numerous other benefits to society. Fission systems operate independently of solar proximity or orientation, and are thus well suited for deep space or planetary surface missions. In addition, the fuel for fission systems (enriched uranium) is virtually non-radioactive. The primary safety issue with fission systems is avoiding inadvertent system start. Addressing this issue through proper system design is straight-forward. Despite the relative simplicity and tremendous potential of space fission systems, the development and utilization of these systems has proven elusive. The first use of fission technology in space occurred 3 April 1965 with the US launch of the SNAP-10A reactor. There have been no additional US uses of space fission systems. While space fission systems were used extensively by the former Soviet Union, their application was limited to earth-orbital missions. Early space fission systems must be safely and affordably utilized if we are to reap the benefits of advanced space fission systems. NASA's Marshall Space Flight Center, working with Los Alamos National Laboratory (LANL), Sandia National Laboratories, and others, has conducted preliminary research related to a Safe Affordable Fission Engine (SAFE). An unfueled core has been fabricated by LANL, and resistance heaters used to verify predicted core thermal performance by closely mimicking heat from fission. The core is designed to use only established nuclear technology and be highly testable. In FY01 an energy conversion system and thruster will be coupled to the core, resulting in an 'end-to-end' nuclear electric propulsion demonstrator being tested using resistance heaters to closely mimic heat from fission. Results of the SAFE test program will be presented. The applicability of a SAFE-powered electric propulsion system to outer planet science missions will also be discussed.

  8. A fission fragment detector for correlated fission output studies

    NASA Astrophysics Data System (ADS)

    Mosby, S.; Tovesson, F.; Couture, A.; Duke, D. L.; Kleinrath, V.; Meharchand, R.; Meierbachtol, K.; O'Donnell, J. M.; Perdue, B.; Richman, D.; Shields, D.

    2014-09-01

    A digital data acquisition system has been combined with a double Frisch gridded ionization chamber for use at both moderated and unmoderated neutron sources at the Los Alamos Neutron Science (LANSCE) facility. The high efficiency of the instrument combined with intense LANSCE beams and new acquisition system permits fission output measurements across 11 orders of magnitude incident neutron energy. The acquisition and analysis system is presented along with the first in-beam performance tests of the setup.

  9. Nuclear-fission studies with relativistic secondary beams: analysis of fission channels

    E-print Network

    C. Boeckstiegel; S. Steinhaeuser; K. -H. Schmidt; H. -G. Clerc; A. Grewe; A. Heinz; M. de Jong; A. R. Junghans; J. Mueller; B. Voss

    2007-12-21

    Nuclear fission of several neutron-deficient actinides and pre-actinides from excitation energies around 11 MeV was studied at GSI Darmstadt by use of relativistic secondary beams. The characteristics of multimodal fission of nuclei around 226Th are systematically investigated and interpreted as the superposition of three fission channels. Properties of these fission channels have been determined for 15 systems. A global view on the properties of fission channels including previous results is presented. The positions of the asymmetric fission channels are found to be constant in element number over the whole range of systems investigated.

  10. Fission Properties for R-Process Nuclei

    SciTech Connect

    Erler, J.

    2012-01-01

    We present a systematics of fission barriers and fission lifetimes for the whole landscape of superheavy elements (SHE), i.e., nuclei with Z 100. The fission lifetimes are also compared with the -decay half-lives. The survey is based on a self-consistent description in terms of the Skyrme-Hartree-Fock (SHF) approach. Results for various different SHF parametrizations are compared to explore the robustness of the predictions. The fission path is computed by quadrupole constrained SHF. The computation of fission lifetimes takes care of the crucial ingredients of the large-amplitude collective dynamics along the fission path, as self-consistent collective mass and proper quantum corrections. We discuss the different topologies of fission landscapes which occur in the realm of SHE (symmetric versus asymmetric fission, regions of triaxial fission, bimodal fission, and the impact of asymmetric ground states). The explored region is extended deep into the regime of very neutron-rich isotopes as they are expected to be produced in the astrophysical r process.

  11. Fission properties for r-process nuclei

    E-print Network

    J. Erler; K. Langanke; H. P. Loens; G. Martínez-Pinedo; P. -G. Reinhard

    2011-12-05

    We present a systematics of fission barriers and fission lifetimes for the whole landscape of super-heavy elements (SHE), i.e. nuclei with Z>100. The fission lifetimes are also compared with the alpha-decay half-lives. The survey is based on a self-consistent description in terms of the Skyrme-Hartree-Fock (SHF) approach. Results for various different SHF parameterizations are compared to explore the robustness of the predictions. The fission path is computed by quadrupole constrained SHF. The computation of fission lifetimes takes care of the crucial ingredients of the large-amplitude collective dynamics along the fission path, as self-consistent collective mass and proper quantum corrections. We discuss the different topologies of fission landscapes which occur in the realm of SHE (symmetric versus asymmetric fission, regions of triaxial fission, bi-modal fission, and the impact of asymmetric ground states). The explored region is extended deep into the regime of very neutron-rich isotopes as they are expected to be produced in the astrophysical r process.

  12. The VERDI fission fragment spectrometer

    NASA Astrophysics Data System (ADS)

    Frégeau, M. O.; Bry?, T.; Gamboni, Th.; Geerts, W.; Oberstedt, S.; Oberstedt, A.; Borcea, R.

    2013-12-01

    The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF) technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This configuration, where the stop detector will provide us simultaneously with the kinetic energy of the fragment and timing information, significantly limits energy straggling in comparison to legacy experimental setup where a thin foil was usually used as a stop detector. In order to improve timing resolution, neutron transmutation doped silicon will be used. The high resistivity homogeneity of this material should significantly improve resolution in comparison to standard silicon detectors. Post-neutron fission fragment masses are obtained form the time-of-flight and the energy signal in the silicon detector. As an intermediary step a diamond detector will also be used as start detector located very close to the target. Previous tests have shown that poly-crystalline chemical vapour deposition (pCVD) diamonds provides a coincidence time resolution of 150 ps not allowing complete separation between very low-energy fission fragments, alpha particles and noise. New results from using artificial single-crystal diamonds (sCVD) show similar time resolution as from pCVD diamonds but also sufficiently good energy resolution.

  13. Technical Application of Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Denschlag, J. O.

    The chapter is devoted to the practical application of the fission process, mainly in nuclear reactors. After a historical discussion covering the natural reactors at Oklo and the first attempts to build artificial reactors, the fundamental principles of chain reactions are discussed. In this context chain reactions with fast and thermal neutrons are covered as well as the process of neutron moderation. Criticality concepts (fission factor ?, criticality factor k) are discussed as well as reactor kinetics and the role of delayed neutrons. Examples of specific nuclear reactor types are presented briefly: research reactors (TRIGA and ILL High Flux Reactor), and some reactor types used to drive nuclear power stations (pressurized water reactor [PWR], boiling water reactor [BWR], Reaktor Bolshoi Moshchnosti Kanalny [RBMK], fast breeder reactor [FBR]). The new concept of the accelerator-driven systems (ADS) is presented. The principle of fission weapons is outlined. Finally, the nuclear fuel cycle is briefly covered from mining, chemical isolation of the fuel and preparation of the fuel elements to reprocessing the spent fuel and conditioning for deposit in a final repository.

  14. Antimicrobial Polymeric Materials with Quaternary Ammonium and Phosphonium Salts

    PubMed Central

    Xue, Yan; Xiao, Huining; Zhang, Yi

    2015-01-01

    Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers. PMID:25667977

  15. Quaternary geology of Avery Island, Louisiana

    SciTech Connect

    Autin, W.J.; McCulloh, R.P.; Davison, A.T.

    1986-09-01

    Avery Island, one of the Five Islands salt domes of south-central Louisiana, is a piercement-type dome that has been uplifted from several kilometers' depth. It is nearly circular in plan with a maximum elevation approximately 50 m above the surrounding coastal marsh. Dissection has produced a terrain of gullies and steep slopes. The features identified indicate a complex geologic history for Avery Island. Deposition of late Pleistocene sediments in a low-relief alluvial plain and subsequent soil development predate domal uplift. The stratigraphy of loess and colluvial silts indicates the island was emergent during loess depositions. The degree of dissection, distribution of colluvium, and shearing of Quaternary sediments reflects continual uplift after loess deposition.

  16. Quaternary coral reef refugia preserved fish diversity.

    PubMed

    Pellissier, Loïc; Leprieur, Fabien; Parravicini, Valeriano; Cowman, Peter F; Kulbicki, Michel; Litsios, Glenn; Olsen, Steffen M; Wisz, Mary S; Bellwood, David R; Mouillot, David

    2014-05-30

    The most prominent pattern in global marine biogeography is the biodiversity peak in the Indo-Australian Archipelago. Yet the processes that underpin this pattern are still actively debated. By reconstructing global marine paleoenvironments over the past 3 million years on the basis of sediment cores, we assessed the extent to which Quaternary climate fluctuations can explain global variation in current reef fish richness. Comparing global historical coral reef habitat availability with the present-day distribution of 6316 reef fish species, we find that distance from stable coral reef habitats during historical periods of habitat loss explains 62% of the variation in fish richness, outweighing present-day environmental factors. Our results highlight the importance of habitat persistence during periods of climate change for preserving marine biodiversity. PMID:24876495

  17. Fourfold nanosystems for quaternary storage devices

    NASA Astrophysics Data System (ADS)

    Blachowicz, T.; Ehrmann, A.

    2011-10-01

    In nano-magnetic coupled systems of wires, pronounced magnetization steps in the hysteresis loops have been found by micromagnetic simulations. The steps can be attributed to stable intermediate states, similar to flux-closed vortex states in ferromagnetic nano-rings. Due to the fourfold anisotropy of the system of four crossed nanowires, these states can be distinguished even by measuring the magnetization of the whole system, giving rise to four separated states without application of external magnetic field. Opposite to actual trials with nano-rings or layered structures, no additional method of symmetry breaking is necessary. Such an easily created system can be utilized, e.g., in quaternary (four states, i.e., two bits per magnetic nano-object) magnetic storage applications.

  18. Suggested terminology for Quaternary dating methods

    USGS Publications Warehouse

    Colman, Steven M.; Pierce, K.L.; Birkeland, P.W.

    1987-01-01

    Classification of Quaternary dating methods should be based on the level of quantitative information and the degree of confidence contained in the age estimates produced by the dating methods. We recommend the use of the terms numerical-age, calibrated-age, relative-age, and correlated-age to describe these levels. We also classify dating methods by type into sideral, isotopic, radiogenic, chemical and biological, geomorphic, and correlation methods. The use of "absolute" is inappropriate for most dating methods, and should be replaced by "numerical." The use of "date" should be minimized in favor of "age" or "age estimate." We recommend use of the abbreviations ka and Ma for most ages; calender dates can be used where appropriate and yr B.P. can be used for radiocarbon ages. ?? 1987.

  19. On Quaternary glaciations, observations and theories

    NASA Astrophysics Data System (ADS)

    Paillard, D.

    2015-07-01

    In a recent paper, Paillard (2015) presents a rapid overview of both major theoretical and empirical studies of Pleistocene glaciations. In particular, it is explained how, over the last 150 years, astronomical theories were confronted to observational constraints and why the "100-kyr problem" is still the major unsolved issue of Quaternary ice ages. This paper also discusses the main alternative theory, which involves changes in atmospheric carbon dioxide concentration. It is then argued that a synthesis of both theories would better account for empirical evidences, as well as for our current knowledge of climate physics. Indeed, if there is no doubt that ice ages are "paced" by the astronomy as evidenced in Hays et al. (1976), the cause of terminations, and therefore the dynamics of the 100-kyr cycles, appears to be closely linked to Southern Ocean climate and atmospheric pCO2.

  20. MODELING AND FISSION CROSS SECTIONS FOR AMERICIUM.

    SciTech Connect

    ROCHMAN, D.; HERMAN, M.; OBLOZINSKY, P.

    2005-05-01

    This is the final report of the work performed under the LANL contract on the modeling and fission cross section for americium isotopes (May 2004-June 2005). The purpose of the contract was to provide fission cross sections for americium isotopes with the nuclear reaction model code EMPIRE 2.19. The following work was performed: (1) Fission calculations capability suitable for americium was implemented to the EMPIRE-2.19 code. (2) Calculations of neutron-induced fission cross sections for {sup 239}Am to {sup 244g}Am were performed with EMPIRE-2.19 for energies up to 20 MeV. For the neutron-induced reaction of {sup 240}Am, fission cross sections were predicted and uncertainties were assessed. (3) Set of fission barrier heights for each americium isotopes was chosen so that the new calculations fit the experimental data and follow the systematics found in the literature.

  1. Comparative evaluation of solar, fission, fusion, and fossil energy resources. Part 2: Power from nuclear fission

    NASA Technical Reports Server (NTRS)

    Clement, J. D.

    1973-01-01

    Different types of nuclear fission reactors and fissionable materials are compared. Special emphasis is placed upon the environmental impact of such reactors. Graphs and charts comparing reactor facilities in the U. S. are presented.

  2. Fission dynamics within time-dependent Hartree-Fock: deformation-induced fission

    E-print Network

    Goddard, P M; Rios, A

    2015-01-01

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide $^{240}$Pu as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate non-adiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behaviour. Those beginning just beyond the ...

  3. Monte carlo sampling of fission multiplicity.

    SciTech Connect

    Hendricks, J. S.

    2004-01-01

    Two new methods have been developed for fission multiplicity modeling in Monte Carlo calculations. The traditional method of sampling neutron multiplicity from fission is to sample the number of neutrons above or below the average. For example, if there are 2.7 neutrons per fission, three would be chosen 70% of the time and two would be chosen 30% of the time. For many applications, particularly {sup 3}He coincidence counting, a better estimate of the true number of neutrons per fission is required. Generally, this number is estimated by sampling a Gaussian distribution about the average. However, because the tail of the Gaussian distribution is negative and negative neutrons cannot be produced, a slight positive bias can be found in the average value. For criticality calculations, the result of rejecting the negative neutrons is an increase in k{sub eff} of 0.1% in some cases. For spontaneous fission, where the average number of neutrons emitted from fission is low, the error also can be unacceptably large. If the Gaussian width approaches the average number of fissions, 10% too many fission neutrons are produced by not treating the negative Gaussian tail adequately. The first method to treat the Gaussian tail is to determine a correction offset, which then is subtracted from all sampled values of the number of neutrons produced. This offset depends on the average value for any given fission at any energy and must be computed efficiently at each fission from the non-integrable error function. The second method is to determine a corrected zero point so that all neutrons sampled between zero and the corrected zero point are killed to compensate for the negative Gaussian tail bias. Again, the zero point must be computed efficiently at each fission. Both methods give excellent results with a negligible computing time penalty. It is now possible to include the full effects of fission multiplicity without the negative Gaussian tail bias.

  4. Fission-product retention in HTGR fuels

    SciTech Connect

    Homan, F.J.; Kania, M.J.; Tiegs, T.N.

    1982-01-01

    Retention data for gaseous and metallic fission products are presented for both Triso-coated and Biso-coated HTGR fuel particles. Performance trends are established that relate fission product retention to operating parameters, such as temperature, burnup, and neutron exposure. It is concluded that Biso-coated particles are not adequately retentive of fission gas or metallic cesium, and Triso-coated particles which retain cesium still lose silver. Design implications related to these performance trends are identified and discussed.

  5. Saturation current of miniaturized fission chambers

    NASA Astrophysics Data System (ADS)

    Chabod, Sébastien P.

    2009-01-01

    We present the detailed formulae of the saturation currents for the four main categories of fission chambers operating in current mode. The results obtained are function of simple parameters: number of fission reactions within the chamber deposits, geometric characteristics of the electrodes and filling gas properties. A direct relation between the saturation current values and the ambient neutron flux is thus established. These results should reduce the number, the duration and the cost of the calibration procedures required to operate the fission chambers.

  6. Some Fission Problems Circa 1950 and 2008

    NASA Astrophysics Data System (ADS)

    ?wiatecki, W. J.

    In the first part of the talk I will recall conversations with Niels Bohr and John Wheeler concerning the puzzle of the asymmetric mass division in nuclear fission. In 1950 this was the outstanding problem in fission theory, and for a brief period I foolishly believed to have found the solution by relaxing the incompressibility assumption in the liquid drop model of fission. In the second part I will describe recent progress in the formulation and streamlining of the transition-state formulae for the competition between the disintegration of an excited compound nucleus by particle emission and fission.

  7. Theoretical Description of the Fission Process

    SciTech Connect

    Witold Nazarewicz

    2003-07-01

    The main goals of the project can be summarized as follows: Development of effective energy functionals that are appropriate for the description of heavy nuclei. Our goal is to improve the existing energy density (Skyrme) functionals to develop a force that will be used in calculations of fission dynamics. Systematic self-consistent calculations of binding energies and fission barriers of actinide and trans-actinide nuclei using modern density functionals. This will be followed by calculations of spontaneous fission lifetimes and mass and charge divisions using dynamic adiabatic approaches based on the WKB approximation. Investigate novel microscopic (non-adiabatic) methods to study the fission process.

  8. Late Quaternary history of North Eurasian Norway spruce (Picea abies)

    E-print Network

    Tinner, Willy

    Journal of Biogeography (J. Biogeogr.) (2015) 42, 1431­1442 #12;INTRODUCTION The boreal forest or taiga, the taiga experienced repeated range contractions and expansions driven by the Quaternary climate

  9. Fission dynamics within time-dependent Hartree-Fock: boost-induced fission

    E-print Network

    P. M. Goddard; P. D. Stevenson; A. Rios

    2015-10-27

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe induced fission processes, using quadrupole boosts in the nuclide $^{240}$Pu as an example. Methods: Quadrupole constrained Hartree-Fock calculations are used to create a potential energy surface. An isomeric state and a state beyond the second barrier peak are excited by means of instantaneous as well as temporally extended gauge boosts with quadrupole shapes. The subsequent deexcitation is studied in a time-dependent Hartree-Fock simulation, with emphasis on fissioned final states. The corresponding fission fragment mass numbers are studied. Results: In general, the energy deposited by the quadrupole boost is quickly absorbed by the nucleus. In instantaneous boosts, this leads to fast shape rearrangements and violent dynamics that can ultimately lead to fission. This is a qualitatively different process than the deformation-induced fission. Boosts induced within a finite time window excite the system in a relatively gentler way, and do induce fission but with a smaller energy deposition. Conclusions: The fission products obtained using boost-induced fission in time-dependent Hartree-Fock are more asymmetric than the fragments obtained in deformation-induced fission, or the corresponding adiabatic approaches.

  10. Spallation - Neutrons Beyond Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Conrad, Harald

    The classical research neutron sources are fission reactors. They have reached their technical limits as far as neutron flux is concerned. But there is an alternative way with many advantages: spallation. The emphasis in this context is on pulsed operation, which is easily achieved with spallation as being accelerator-driven. The extension of neutron scattering to fields not covered with reactors is discussed as well as the utilization of spallation neutrons for other fields such as nuclear waste transmutation and future power reactors.

  11. Quaternary cave levels in peninsular Florida

    NASA Astrophysics Data System (ADS)

    Florea, Lee J.; Vacher, H. L.; Donahue, Brian; Naar, David

    2007-05-01

    The hypothesis that caves in the Florida Peninsula are tied to Quaternary sea levels was proposed by hydrogeologists, without data, some 40 years ago. The hypothesis is a version of glacial control of cave levels, which is the logical combination of the water-table theory of speleogenesis and the concept that base level positions the water table. At the USA type example of glacial control of cave levels—Mammoth Cave in the Paleozoic rocks of Kentucky—the intermediary is base level determined by rivers. By hypothesis, the intermediary for Florida is glacioeustatic sea level. This paper presents elevation data that supports this hypothesis. Recent cave surveys in the air-filled caves and spot elevations from archived maps reveal prominent levels of passages centered at 5, 12, 21, and 30 m above sea level over broad areas. They do not follow the large-scale structure of the Floridan aquifer. Instead, they align with nearby, coastal marine terraces identified as modal peaks on frequency plots from various topographic data bases. Levels matching with the three highest terraces—Wicomico, Penholoway, and Talbott—are particularly clear. Lower levels, if they accord with sea-level stands, are likely composites. Data from cavities encountered in drilled wells (e.g., bit drops) and spot elevations from archived underwater cave maps demonstrate passage levels at depths of 15, 30, 70, and 90-120 m below the modern water table. The depths below water table are similar to the depths below sea level of distant submerged terraces and paleoshoreline features identified using multibeam bathymetric data in the Gulf of Mexico. The cave, bit-drop, and terrace data are all consistent with the concept that Quaternary sea level is the fundamental control on the cave-scale porosity within the Floridan aquifer. This conclusion does not rule out the possibility that lithologically favored positions, paleokarst features and confining units, and mixing zones are also involved in the location of caves levels in this near-coastal environment.

  12. Experimental investigation into Quaternary badland geomorphic development

    NASA Astrophysics Data System (ADS)

    Kasanin-Grubin, Milica; Kuhn, Nikolaus; Yair, Aaron; Bryan, Rorke; Schwanghart, Wolfgang

    2010-05-01

    Badland morphology is commonly linked to lithological properties of the bedrock. However, recent investigations indicate that the geomorphic development is sensitive to climate and in particular to precipitation characteristics. In this study, the precipitation characteristics that are critical for the Quaternary landscape development in the Dinosaur Badlands in Alberta, Canada, and Zin Valley Badlands, Negev Desert, Israel are investigated. Runoff, erosion and weathering were simulated in the field and the laboratory to determine rates for modeling different precipitation regimes. Currently, the geomorphic development in the Dinosaur badlands is characterized by weathering/supply limited conditions, leading to slope retreat independent of lithology. In the Negev, transport limited conditions cause frequent runoff discontinuity, creating a pattern of areas dominated by erosion or deposition. The results of the weathering and erosion experiments show that the balance between snowmelt induced weathering in the spring and summer rainfall and erosion determine the rate of slope retreat in the Dinosaur Badlands. In the Zin Valley, on the other hand, the magnitude of the individual rainstorms determines whether a slope section is eroded or acts as a sediment sink. The experiments illustrate that the badland slopes experienced an auto-stabilization during the Quaternary in the Zin Valley. In the Dinosaur Badlands Holocene climatic variations have not caused a permanent differentiation of patterns of erosion and deposition. Based on these results the reaction of badland slopes to changing precipitation characteristics was modeled. In their current state, both badland slope systems appear to be fairly stable against climate change in the range of those occurring during the Holocene. However, the stability is achieved in different ways. In the Dinosaur Badlands, weathering rates are low compared to erosion capacity, maintaining continuous evacuation of sediment from slopes to the flood planes of the Red Deer River system. Only a very pronounced contrast between winter weathering and drier summers would generate a colluvium and thus change slope hydrology. In the Zin Valley the development of a thick colluvium at the foot of the slopes has increased infiltration capacity, reducing runoff and sediment yield into the floodplain. Here, only an increase in rainfall magnitude would improve runoff continuity and induce the erosion of the colluvium. This would in turn reduce infiltration capacity and thus initiate a positive feedback on runoff and sediment yield into the Zin River. Overall, Holocene climate change appears to be insufficient to change the geomorphic development in both badlands. However, this stability is achieved not despite of climate, but because of the specific history of geomorphic development. In addition, the combination of erosion and weathering experiments with numerical modeling demonstrates the versatility of Experimental Geomorphology in landscape evolution studies.

  13. Fission dynamics within time-dependent Hartree-Fock: Deformation-induced fission

    NASA Astrophysics Data System (ADS)

    Goddard, Philip; Stevenson, Paul; Rios, Arnau

    2015-11-01

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus and the daughter products. Purpose: We explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide Pu240 as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate nonadiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behavior. Those beginning just beyond the barrier explore large-amplitude motion but do not fission, whereas those beginning beyond the two-fragment pathway crossing fission to final states which differ according to the exact initial deformation. Conclusions: Time-dependent Hartree-Fock is able to give a good qualitative and quantitative description of fast fission, provided one begins from a sufficiently deformed state.

  14. Fission dynamics within time-dependent Hartree-Fock: deformation-induced fission

    E-print Network

    P. M. Goddard; P. D. Stevenson; A. Rios

    2015-11-03

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide $^{240}$Pu as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate non-adiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behaviour. Those beginning just beyond the barrier explore large amplitude motion but do not fission, whereas those beginning beyond the two-fragment pathway crossing fission to final states which differ according to the exact initial deformation. Conclusions: Time-dependent Hartree-Fock is able to give a good qualitative and quantitative description of fast fission, provided one begins from a sufficiently deformed state.

  15. Nuclear Power from Fission Reactors. An Introduction.

    ERIC Educational Resources Information Center

    Department of Energy, Washington, DC. Technical Information Center.

    The purpose of this booklet is to provide a basic understanding of nuclear fission energy and different fission reaction concepts. Topics discussed are: energy use and production, current uses of fuels, oil and gas consumption, alternative energy sources, fossil fuel plants, nuclear plants, boiling water and pressurized water reactors, the light…

  16. Spontaneous fission properties and lifetime systematics

    SciTech Connect

    Hoffman, D.C.

    1989-03-01

    Half-lives for spontaneous fission of nuclides with even and odd numbers of particles are compared with recent theoretical calculations. A summary of odd particle hindrance factors is given. The most recent measurements of kinetic-energy and mass distributions and neutron emission for spontaneous fission of the heaviest nuclides are summarized and discussed. 51 refs., 9 figs.

  17. Fission properties of the BCPM functional

    E-print Network

    Samuel A. Giuliani; Luis M. Robledo

    2013-08-27

    We explore the properties of the Barcelona Catania Paris Madrid (BCPM) energy density functional concerning fission dynamics. Potential energy surfaces as well as collective inertias relevant in the fission process are computed for several nuclei where experimental data exists. Inner and outer barrier heights as well as fission isomer excitation energies are reproduced quite well in all the cases. The spontaneous fission half lives $t_{\\textrm{\\textrm{SF}}}$ are also computed using the standard semiclassical approach and the results are compared with the experimental data. A reasonable agreement with experiment is found over a range of 27 orders of magnitude but the theoretical predictions suffer from large uncertainties associated to the values of the parameters entering the spontaneous fission half life formula. The impact that increasing the pairing correlations strengths has in the spontaneous fission half lives is analyzed and found to be large in all the nuclei considered. Given the satisfactory description of the trend of fission properties with mass number we explore the fission properties of the even-even uranium isotope chain from $^{226}$U to $^{282}$U. Very large half lives are found when getting close to neutron number N=184.

  18. Options for Affordable Fission Surface Power Systems

    NASA Technical Reports Server (NTRS)

    Houts, Mike; Gaddis, Steve; Porter, Ron; VanDyke, Melissa; Martin Jim; Godfroy, Tom; Bragg-Sitton, Shannon; Garber, Anne; Pearson, Boise

    2006-01-01

    Fission surface power systems could provide abundant power anywhere on free surface of the moon or Mars. Locations could include permanently shaded regions on the moon and high latitudes on Mars. To be fully utilized; however, fission surface power systems must be safe, have adequate performance, and be affordable. This paper discusses options for the design and development of such systems.

  19. Nuclear Fission and Fission{minus}Product Spectroscopy: Second International Workshop. Proceedings

    SciTech Connect

    Fioni, G.; Faust, H.; Oberstedt, S.; Hambsch, F.

    1998-10-01

    These proceedings represent papers presented at the Second International Workshop on Nuclear Fission and Fission{minus}Product Spectroscopy held in Seyssins, France in April, 1998. The objective was to bring together the specialists in the field to overview the situation and to assess our present understanding of the fission process. The topics presented at the conference included nuclear waste management, incineration, neutron driven transmutation, leakage etc., radioactive beams, neutron{minus}rich nuclei, neutron{minus}induced and spontaneous fission, ternary fission phenomena, angular momentum, parity and time{minus}reversal phenomena, and nuclear fission at higher excitation energy. Modern spectroscopic tools for gamma spectroscopy as applied to fission were also discussed. There were 53 papers presented at the conference,out of which 3 have been abstracted for the Energy,Science and Technology database.(AIP)

  20. Fission Models of Population Variability

    PubMed Central

    Thompson, E. A.

    1979-01-01

    Most models in population genetics are models of allele frequency, making implicit or explicit assumptions of equilibrium or constant population size. In recent papers, we have attempted to develop more appropriate models for the analysis of rare variant data in South American Indian tribes; these are branching process models for the total number of replicates of a variant allele. The spatial distribution of a variant may convey information about its history and characteristics, and this paper extends previous models to take this factor into consideration. A model of fission into subdivisions is superimposed on the previous branching process, and variation between subdivisions is considered. The case where fission is nonrandom and the locations of like alleles are initially positively associated, as would happen were a tribal cluster or village to split on familial lines, is also analyzed. The statistics developed are applied to Yanomama Indian data on rare genetic variants. Due to insufficient time depth, no definitive new inferences can be drawn, but the analysis shows that this model provides results consistent with previous conclusions, and demonstrates the general type of question that may be answered by the approach taken here. In particular, striking confirmation of a higher-than-average growth rate, and hence smaller-than-previously-estimated age, is obtained for the Yan2 serum albumen variant. PMID:535728

  1. Adsorption and excess fission xenon

    NASA Astrophysics Data System (ADS)

    Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

    The adsorption of Xe and Kr on lunar soil 10084 was measured by a method that employs only very low fractions of monolayer coverage. Results are presented as parameters for calculation of the Henry constant for adsorption as a function of temperature. The adsorption potentials are about 3 kcal/mole for Kr and 5 kcal/mole for Xe; heating the sample in vacuum increased the Xe potential to nearly 7 kcal/mole. Henry constants at the characteristic lunar temperature are about 0.3 cu cm STP/g-atm. These data were applied to consider whether adsorption is important in producing the excess fission Xe effect characteristic of highland breccias. Sorption equilibrium with a transient lunar atmosphere vented fission Xe produces concentrations seven orders of magnitude lower than observed concentrations. Higher concentrations result because of the resistance of the regolith to upward diffusion of Xe. A diffusion coefficient of 0.26 sq cm/sec is estimated for this process.

  2. Theoretical Description of the Fission Process

    SciTech Connect

    Witold Nazarewicz

    2009-10-25

    Advanced theoretical methods and high-performance computers may finally unlock the secrets of nuclear fission, a fundamental nuclear decay that is of great relevance to society. In this work, we studied the phenomenon of spontaneous fission using the symmetry-unrestricted nuclear density functional theory (DFT). Our results show that many observed properties of fissioning nuclei can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. From the calculated collective potential and collective mass, we estimated spontaneous fission half-lives, and good agreement with experimental data was found. We also predicted a new phenomenon of trimodal spontaneous fission for some transfermium isotopes. Our calculations demonstrate that fission barriers of excited superheavy nuclei vary rapidly with particle number, pointing to the importance of shell effects even at large excitation energies. The results are consistent with recent experiments where superheavy elements were created by bombarding an actinide target with 48-calcium; yet even at high excitation energies, sizable fission barriers remained. Not only does this reveal clues about the conditions for creating new elements, it also provides a wider context for understanding other types of fission. Understanding of the fission process is crucial for many areas of science and technology. Fission governs existence of many transuranium elements, including the predicted long-lived superheavy species. In nuclear astrophysics, fission influences the formation of heavy elements on the final stages of the r-process in a very high neutron density environment. Fission applications are numerous. Improved understanding of the fission process will enable scientists to enhance the safety and reliability of the nation’s nuclear stockpile and nuclear reactors. The deployment of a fleet of safe and efficient advanced reactors, which will also minimize radiotoxic waste and be proliferation-resistant, is a goal for the advanced nuclear fuel cycles program. While in the past the design, construction, and operation of reactors were supported through empirical trials, this new phase in nuclear energy production is expected to heavily rely on advanced modeling and simulation capabilities.

  3. Fission dynamics at low excitation energy

    NASA Astrophysics Data System (ADS)

    Aritomo, Y.; Chiba, S.; Ivanyuk, F.

    2014-11-01

    The mass asymmetry in the fission of 236U at low excitation energy is clarified by the analysis of the trajectories obtained by solving the Langevin equations for the shape degrees of freedom. It is demonstrated that the position of the peaks in the mass distribution of fission fragments is determined mainly by the saddle point configuration originating from the shell correction energy. The width of the peaks, on the other hand, results from the shape fluctuations close to the scission point caused by the random force in the Langevin equation. We have found out that the fluctuations between elongated and compact shapes are essential for the fission process. According to our results the fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup, but is accompanied by the fluctuations between elongated and compact shapes. This picture presents a new viewpoint of fission dynamics and the splitting mechanism.

  4. Theory of neutron emission in fission

    SciTech Connect

    Madland, D.G.

    1989-01-01

    Following a summary of the observables in neutron emission in fission, a brief history is given of theoretical representations of the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity /bar /nu///sub p/. This is followed by descriptions, together with examples, of modern approaches to the calculation of these quantities including recent advancements. Emphasis will be placed upon the predictability and accuracy of the modern approaches. In particular, the dependence of N(E) and /bar /nu///sub p/ on the fissioning nucleus and its excitation energy will be discussed, as will the effects of and competition between first-, second- and third-chance fission in circumstances of high excitation energy. Finally, properties of neutron-rich (fission-fragment) nuclei are discussed that must be better known to calculate N(E) and /bar /nu///sub p/ with higher accuracy than is currently possible. 17 refs., 11 figs.

  5. Systematics of Fission-Product Yields

    E-print Network

    Wahl, A C

    2002-01-01

    Empirical equations representing systematics of fission-product yields have been derived from experimental data. The systematics give some insight into nuclear-structure effects on yields, and the equations allow estimation of yields from fission of any nuclide with atomic number Z sub F = 90 thru 98, mass number A sub F = 230 thru 252, and precursor excitation energy (projectile kinetic plus binding energies) PE = 0 thru approx 200 MeV--the ranges of these quantities for the fissioning nuclei investigated. Calculations can be made with the computer program CYFP. Estimates of uncertainties in the yield estimates are given by equations, also in CYFP, and range from approx 15% for the highest yield values to several orders of magnitude for very small yield values. A summation method is used to calculate weighted average parameter values for fast-neutron (approx fission spectrum) induced fission reactions.

  6. Fission Surface Power Technology Development Status

    NASA Technical Reports Server (NTRS)

    Palac, Donald T.; Mason, Lee S.; Houts, Michael G.; Harlow, Scott

    2010-01-01

    Power is a critical consideration in planning exploration of the surfaces of the Moon, Mars, and beyond. Nuclear power is an important option, especially for locations in the solar system where sunlight is limited in availability or intensity. NASA is maintaining the option for fission surface power for the Moon and Mars by developing and demonstrating technology for an affordable fission surface power system. Because affordability drove the determination of the system concept that this technology will make possible, low development and recurring costs result, while required safety standards are maintained. However, an affordable approach to fission surface power also provides the benefits of simplicity, robustness, and conservatism in design. This paper will illuminate the multiplicity of benefits to an affordable approach to fission surface power, and will describe how the foundation for these benefits is being developed and demonstrated in the Exploration Technology Development Program s Fission Surface Power Project.

  7. Superfluid dynamics of 258Fm fission

    E-print Network

    Guillaume Scamps; Cédric Simenel; Denis Lacroix

    2015-01-15

    Theoretical description of nuclear fission remains one of the major challenges of quantum many-body dynamics. The slow, mostly adiabatic motion through the fission barrier is followed by a fast, non-adiabatic descent of the potential between the fragments. The latter stage is essentially unexplored. However, it is crucial as it generates most of the excitation energy in the fragments. The superfluid dynamics in the latter stage of fission is obtained with the time-dependent Hartree-Fock theory including BCS dynamical pairing correlations. The fission modes of the 258Fm nucleus are studied. The resulting fission fragment characteristics show a good agreement with experimental data. Quantum shell effects are shown to play a crucial role in the dynamics and formation of the fragments. The importance of quantum fluctuations beyond the independent particle/quasi-particle picture is underlined and qualitatively studied.

  8. Microscopic Theory of Nuclear Fission: A Review

    E-print Network

    Schunck, N

    2015-01-01

    This article reviews how nuclear fission is described within nuclear density functional theory. In spontaneous fission, half-lives are the main observables and quantum tunnelling the essential concept, while in induced fission the focus is on fragment properties and explicitly time-dependent approaches are needed. The cornerstone of the current microscopic theory of fission is the energy density functional formalism. Its basic tenets, including tools such as the HFB theory, effective two-body effective nuclear potentials, finite-temperature extensions and beyond mean-field corrections, are presented succinctly. The EDF approach is often combined with the hypothesis that the time-scale of the large amplitude collective motion driving the system to fission is slow compared to typical time-scales of nucleons inside the nucleus. In practice, this hypothesis of adiabaticity is implemented by introducing (a few) collective variables and mapping out the many-body Schr\\"odinger equation into a collective Schr\\"odinge...

  9. Fifty years with nuclear fission. Volume 1

    SciTech Connect

    Behrens, J.W.; Carlson, A.D.

    1989-12-31

    The news of the discovery of nuclear fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fifieth anniversary of its discovery by holding a topical meeting entitled, ``Fifty Years with Nuclear Fission,`` in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent development in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicated a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two fully days of sessions (April 27 and 28) at the main site of the NIST in Gaithersburg, Maryland. The wide range of topics covered in this Volume 1 by this topical meeting included plenary invited, and contributed sessions entitled: Preclude to the First Chain Reaction -- 1932 to 1942; Early Fission Research -- Nuclear Structure and Spontaneous Fission; 50 Years of Fission, Science, and Technology; Nuclear Reactors, Secure Energy for the Future; Reactors 1; Fission Science 1; Safeguards and Space Applications; Fission Data; Nuclear Fission -- Its Various Aspects; Theory and Experiments in Support of Theory; Reactors and Safeguards; and General Research, Instrumentation, and By-Product. The individual papers have been cataloged separately.

  10. West Cameroon Quaternary lacustrine deposits: preliminary results

    NASA Astrophysics Data System (ADS)

    Maley, J.; Livingstone, D. A.; Giresse, P.; Brenac, P.; Kling, G.; Stager, C.; Thouveny, N.; Kelts, K.; Haag, M.; Fournier, M.; Bandet, Y.; Williamson, D.; Zogning, A.

    We present preliminary results from the study of a 23.50 m core (BM-6) representing the last 25 000 years. The core was collected in Barombi Mbo, an explosion crater lake formed probably during the Quaternary. The finely laminated sediment are composed mostly of dark brown to green clay rich organic matter (5-10% organic carbon). Each couplet is commonly composed of a lower unit rich in quartz, plant debris, muscovite and sponge spicules, and of a more clayey upper unit often with siderite (FeCO 3) crystals. The average periodicity for one couplet is between 6 and 20 radiocarbon years. The pollen results, which are compared with those of another forested site in Ghana, demonstrate the presence of a forest refuge in West Cameroon during the last major arid period, about 18 000 years BP. At the same time that equatorial forest was broken up, elements of montain vegetation descended to the lowlands. To provide an explanation for these phenomena marked by a drying and cooling of the climate, modern examples of extensions of montain biotopes to low altitude are described. These localized extensions are due to the persistence of cloud cover, often of stratiform type, generated over the relatively cold water of ocean upwellings. Such lowering of sea-surface temperature might be the primary regional cause of the changes of climate and vegetation that occurred in humid tropical Africa. The upwelling, presently synchronous throughout the Guinea Gulf, amplify the trade winds, which could account for the observed changes inland.

  11. Late Quaternary mammalian zoogeography of eastern Washington

    NASA Astrophysics Data System (ADS)

    Lyman, R. Lee; Livingston, Stephanie D.

    1983-11-01

    The late Quaternary mammalian zoogeographic history of eastern Washington as revealed by archaeological and paleontological research conforms to a set of past environmental conditions inferred from botanical data. During the relatively cool and moist late Pleistocene and early Holocene, Cervus cf. elaphus, Ovis canadensis, Vulpes vulpes, Martes americana, Alopex lagopus, and perhaps Rangifer sp., taxa with ecological preferences for mesic steppe habitats, were present in the now xeric Columbia Basin. As the climate became progressively warmer and drier during the late Pleistocene and early Holocene, Antilocapra americana, Onychomys leucogaster, Spermophilus townsendii, and Neotoma cinerea, taxa with ecological preferences for xeric steppe habitats, appear in the Columbia Basin. Bison sp. and Taxidea taxus may have been present in eastern Washington for the last 20,000 yr. Middle and late Holocene records for Oreamnos americanus, Spermophilus columbianus, S. townsendii, Lagurus curtatus, and Urocyon cinereoargenteus in central eastern Washington suggest fluctuations in the ranges of these taxa that conform to a middle Holocene period of less effective precipitation and a ca. 3500-yr-old period of more effective precipitation before essentially modern environmental conditions prevailed.

  12. A Quaternary Fault Database for Central Asia

    NASA Astrophysics Data System (ADS)

    Mohadjer, S.; Ehlers, T. A.; Bendick, R.; Stübner, K.; Strube, T.

    2015-09-01

    Earthquakes represent the highest risk in terms of potential loss of lives and economic damage for Central Asian countries. Knowledge of fault location and behavior is essential in calculating and mapping seismic hazard. Previous efforts in compiling fault information for Central Asia have generated a large amount of data that are published in limited-access journals with no digital maps publicly available, or are limited in their description of important fault parameters such as slip rates. This study builds on previous work by improving access to fault information through a web-based interactive map and an online database with search capabilities that allow users to organize data by different fields. The data presented in this compilation include fault location, its geographic, seismic and structural characteristics, short descriptions, narrative comments and references to peer-reviewed publications. The interactive map displays 1196 fault segments and 34 000 earthquake locations on a shaded-relief map. The online database contains attributes for 122 faults mentioned in the literature, with Quaternary and geodetic slip rates reported for 38 and 26 faults respectively, and earthquake history reported for 39 faults. This work has implications for seismic hazard studies in Central Asia as it summarizes important fault parameters, and can reduce earthquake risk by enhancing public access to information. It also allows scientists and hazard assessment teams to identify structures and regions where data gaps exist and future investigations are needed.

  13. Quaternary Ammonium Biocides: Efficacy in Application

    PubMed Central

    2014-01-01

    Quaternary ammonium compounds (QACs) are among the most commonly used disinfectants. There has been concern that their widespread use will lead to the development of resistant organisms, and it has been suggested that limits should be place on their use. While increases in tolerance to QACs have been observed, there is no clear evidence to support the development of resistance to QACs. Since efflux pumps are believe to account for at least some of the increased tolerance found in bacteria, there has been concern that this will enhance the resistance of bacteria to certain antibiotics. QACs are membrane-active agents interacting with the cytoplasmic membrane of bacteria and lipids of viruses. The wide variety of chemical structures possible has seen an evolution in their effectiveness and expansion of applications over the last century, including non-lipid-containing viruses (i.e., noroviruses). Selection of formulations and methods of application have been shown to affect the efficacy of QACs. While numerous laboratory studies on the efficacy of QACs are available, relatively few studies have been conducted to assess their efficacy in practice. Better standardized tests for assessing and defining the differences between increases in tolerance versus resistance are needed. The ecological dynamics of microbial communities where QACs are a main line of defense against exposure to pathogens need to be better understood in terms of sublethal doses and antibiotic resistance. PMID:25362069

  14. Prompt fission neutron spectra of n+235U above the (n,nf) fission threshold

    NASA Astrophysics Data System (ADS)

    Shu, Neng-Chuan; Jia, Min; Chen, Yong-Jing; Liu, Ting-Jin

    2015-05-01

    Calculations of prompt fission neutron spectra (PFNS) from the 235U(n, f) reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n,xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n,xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n,nf) or (n,2nf) reactions influences the PFNS shape, and the neutron spectra of the (n,xnf) fission-channel are soft compared with the neutron spectra of the (n,f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case. Supported by National Natural Science Foundation of China (11205246, 91126010, U1230127, 91226102), IAEA CRP (15905), and Defense Industrial Technology Development Program (B0120110034)

  15. Singlet fission in pentacene dimers

    PubMed Central

    Zirzlmeier, Johannes; Lehnherr, Dan; Coto, Pedro B.; Chernick, Erin T.; Casillas, Rubén; Basel, Bettina S.; Thoss, Michael; Tykwinski, Rik R.; Guldi, Dirk M.

    2015-01-01

    Singlet fission (SF) has the potential to supersede the traditional solar energy conversion scheme by means of boosting the photon-to-current conversion efficiencies beyond the 30% Shockley–Queisser limit. Here, we show unambiguous and compelling evidence for unprecedented intramolecular SF within regioisomeric pentacene dimers in room-temperature solutions, with observed triplet quantum yields reaching as high as 156 ± 5%. Whereas previous studies have shown that the collision of a photoexcited chromophore with a ground-state chromophore can give rise to SF, here we demonstrate that the proximity and sufficient coupling through bond or space in pentacene dimers is enough to induce intramolecular SF where two triplets are generated on one molecule. PMID:25858954

  16. Fifty years with nuclear fission. Volume 2

    SciTech Connect

    Behrens, J.W.; Carlson, A.D.

    1989-12-31

    The news of the discovery of nucler fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fiftieth anniversary of its discovery by holding a topical meeting entitled, ``Fifty years with nuclear fission,`` in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent developments in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicating a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two full days of sessions (April 27 and 28) at the main sites of the NIST in Gaithersburg, Maryland. The wide range of topics covered by Volume 2 of this topical meeting included plenary invited, and contributed sessions entitled, Nuclear fission -- a prospective; reactors II; fission science II; medical and industrial applications by by-products; reactors and safeguards; general research, instrumentation, and by-products; and fission data, astrophysics, and space applications. The individual papers have been cataloged separately.

  17. Carbohydrate Binding, Quaternary Structure and a Novel Hydrophobic Binding Site in Two Legume

    E-print Network

    Hamelryck, Thomas

    Carbohydrate Binding, Quaternary Structure and a Novel Hydrophobic Binding Site in Two Legume to four. # 1999 Academic Press Keywords: protein-carbohydrate interactions; quaternary structure; legume carbohydrates in a reversible fashion, without showing enzymatic activity towards these carbohydrates. Lectins

  18. FASTGRASS. Fission Product Release Ubase Fuels

    SciTech Connect

    Rest, J.; Zawadzki, S.A.

    1992-09-01

    FASTGRASS is a mechanistic code that predicts atomic and bubble behavior of fission gas in UO2 fuel under steady-state and transient conditions. FASTGRASS also calculates the behavior of the volatile fission products (VFP) I, Cs, and Te as well as the alkaline earth fission products (AEFP) Ba and Sr. The chemistry models include the reaction products Cs2MoO4, Cs2UO4, BaO, SrO and BaUO4. Both the condensed and vapor phases of BaO and SrO are considered. A basic premise of the FASTGRASS analysis is that the noble gases provide the major pathways for fission product release as well as the major reaction sites required for vapor phase formation of various reaction products. Models are included for fission-product generation, atomic migration, bubble nucleation and re-solution, bubble migration and coalescence, channel formation on grain faces, the interlinking of porosity along grain edges, and microcracking on both the amount of fission products released and on their distribution within the fuel. Mechanistic models are also included for grain growth/grain boundary sweeping, and for the behavior of fission products under liquefaction/dissolution and fuel melting conditions. FASTGRASS uses a realistic equation of state for xenon, experimentally derived steady-state bubble mobilities, and phenomenological modeling of bubble mobilities during transient nonequilibrium conditions to calculate the swelling due to retained fission-gas bubbles in the lattice, on grain faces, and along the grain edges. FASTGRASS also calculates fission-product release as a function of time for steady-state and transient thermal conditions. Two variants of the software are included: FASTGRASS, for multinode calculations, and PARAGRASS, for single-node calculations. PARAGRASS can be used as a module in a larger program.

  19. FASTGRASS. Fission Product Release Ubase Fuels

    SciTech Connect

    Rest, J.; Zawadzki, S.A.

    1992-09-01

    FASTGRASS is a mechanistic code that predicts atomic and bubble behavior of fission gas in UO2 fuel under steady-state and transient conditions. FASTGRASS also calculates the behavior of the volatile fission products (VFP) I, Cs, and Te as well as the alkaline earth fission products (AEFP) Ba and Sr. The chemistry models include the reaction products Cs2MoO4, Cs2UO4, BaO, SrO and BaUO4. Both the condensed and vapor phases of BaO and SrO are considered. A basic premise of the FASTGRASS analysis is that the noble gases provide the major pathways for fission product release as well as the major reaction sites required for vapor phase formation of various reaction products. Models are included for fission-product generation, atomic migration, bubble nucleation and re-solution, bubble migration and coalescence, channel formation on grain faces, the interlinking of porosity along grain edges, and microcracking on both the amount of fission products released and on their distribution within the fuel. Mechanistic models are also included for grain growth/grain boundary sweeping, and for the behavior of fission products under liquefaction/dissolution and fuel melting conditions. FASTGRASS uses a realistic equation of state for xenon, experimentally derived steady-state bubble mobilities, and phenomenological modeling of bubble mobilities during transient nonequilibrium conditions to calculate the swelling due to retained fission- gas bubbles in the lattice, on grain faces, and along the grain edges. FASTGRASS also calculates fission-product release as a function of time for steady-state and transient thermal conditions. Two variants of the software are included: FASTGRASS, for multinode calculations, and PARAGRASS, for single-node calculations. PARAGRASS can be used as a module in a larger program.

  20. Quaternary Evolution of Karliova Triple Junction

    NASA Astrophysics Data System (ADS)

    Sançar, Taylan; Zabc?, Cengiz; Akyüz, H. Serdar

    2013-04-01

    The arguments to explain Quaternary evolution of Karl?ova Triple Junction (KTJ) depends upon two different analogue models. The compressional type of Prandtl Cell Model (PCM) and 60 km wide shear zone with concomitant counter clockwise block rotation used to modelled for west and east of the KTJ respectively. The data for the model of west of the KTJ acquired by extensive field studies, and quantified geomorphic features. Compressional PCM put forward that behavior of slip lines controlled by boundary faults. But the model is not enough to explain slip distribution, age relation of them. At west of the KTJ boundary faults presented by eastern most segments of the North Anatolian Fault Zone (NAFZ) and the East Anatolian Fault Zone (EAFZ). Slip lines, however, presented by Bahçeli and Toklular faults. Both field studies and morphometric analyses undisputedly set forth that there are two different fault types between the NAFZ and EAFZ. The most strain loaded fault type, which are positioned near the NAFZ, start as a strike-slip fault and when it turn to SE its sense of motion change to oblique normal due to changing orientation of principal stress axes. The new orientation of stress axes exposed in the field as a special kind of caprock -cuesta-. The younger slip lines formed very close to junction point and accommodate less slip. Even though slip trajectories started from the boundary faults in compressional PCM, at the west of KTJ, right lateral trajectories more clearly formed close the NAFZ and left lateral trajectories, relatively less strain loaded fault type, are poorly formed close the EAFZ . We think that, this differences between KTJ and compressional PCM result from the distinction of velocity of boundary faults. East of the KTJ governed by completely different mechanism. The region controlled two main fault systems. The Varto Fault Zone (VFZ), the eastern branch of the KTJ, and Murat Fault (MF) delimited the region from north and south respectively. The region also delimited at west by the EAFZ. All secondary faults between these three faults are strike slip faults. The faults which are positioned NW-SE and nearly parallel to the N70W oriented VFZ are dextral, whereas sinistral faults are N-S oriented and nearly orthogonal to NW-SE trending right lateral faults. Sinistral faults develop in the overlap area between adjacent left stepping of dextral faults which are arranged in an en echelon pattern. This configuration formed under shear zone regime with one Previous shear zone model studies proposed that right lateral faults form the 17-24 degree to principal displacement zone. Paleo-magnetic studies of Plio-Quaternary rocks, which covered the all region, show that there is a counterclockwise block rotation between 18 to 23 degree that is clearly explain position of the secondary right lateral faults.

  1. Nuclear Thermal Rockets: The Physics of the Fission Reactor

    E-print Network

    Ross, Shane

    Nuclear Thermal Rockets: The Physics of the Fission Reactor Shane D. Ross Control and Dynamical heats up when it passes through a nuclear reactor, where controlled fission of some fissionable material, with the nuclear fission reactor as a heat source [Lawrence, Witter, and Humble, 1992]. it works essentially

  2. Recovery and use of fission product noble metals

    SciTech Connect

    Jensen, G.A.; Rohmann, C.A.; Perrigo, L.D.

    1980-06-01

    Noble metals in fission products are of strategic value. Market prices for noble metals are rising more rapidly than recovery costs. A promising concept has been developed for recovery of noble metals from fission product waste. Although the assessment was made only for the three noble metal fission products (Rh, Pd, Ru), there are other fission products and actinides which have potential value. (DLC)

  3. Isomeric-to-prompt fission ratios for the uranium fission isomers 236Um and 238Um

    NASA Astrophysics Data System (ADS)

    Tischler, R.; Kleinrahm, A.; Kroth, R.; Günther, C.

    1980-07-01

    Fission isomers in 236U and 238U have been populated in 235U(d, p)236Um, 236U(d, pn)236Um, and the 238U(d, pn)238Um reactions. Time spectra of fission fragments with respect to the cyclotron beam pulses have been measured. From these measurements the isomeric-to-prompt fission ratios are derived for deuteron energies ranging from 17 to 25 MeV. The isomeric-to-prompt ratios show a distinct maximum around 20 MeV for the (d, pn) reactions, whereas a monotonic decrease is observed for the 235U(d, p)236Um reaction. NUCLEAR REACTIONS, FISSION 235U(d, pf) and 236,238U(d, pnf), measured delayed fission fragment time spectra, deduced isomeric-to-prompt fission ratios.

  4. Fission dynamics within time-dependent Hartree-Fock: boost-induced fission

    E-print Network

    Goddard, P M; Rios, A

    2015-01-01

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe induced fission processes, using quadrupole boosts in the nuclide $^{240}$Pu as an example. Methods: Quadrupole constrained Hartree-Fock calculations are used to create a potential energy surface. An isomeric state and a state beyond the second barrier peak are excited by means of instantaneous as well as temporally extended gauge boosts with quadrupole shapes. The subsequent deexcitation is studied in a time-dependent Hartree-Fock simulation, with emphasis on fissioned final states. The corresponding fission fragment mass numbers are studied. Results: In general, the energy deposited by the quadrupole boost is quickl...

  5. Fission Matrix Capability for MCNP Monte Carlo

    SciTech Connect

    Carney, Sean E.; Brown, Forrest B.; Kiedrowski, Brian C.; Martin, William R.

    2012-09-05

    In a Monte Carlo criticality calculation, before the tallying of quantities can begin, a converged fission source (the fundamental eigenvector of the fission kernel) is required. Tallies of interest may include powers, absorption rates, leakage rates, or the multiplication factor (the fundamental eigenvalue of the fission kernel, k{sub eff}). Just as in the power iteration method of linear algebra, if the dominance ratio (the ratio of the first and zeroth eigenvalues) is high, many iterations of neutron history simulations are required to isolate the fundamental mode of the problem. Optically large systems have large dominance ratios, and systems containing poor neutron communication between regions are also slow to converge. The fission matrix method, implemented into MCNP[1], addresses these problems. When Monte Carlo random walk from a source is executed, the fission kernel is stochastically applied to the source. Random numbers are used for: distances to collision, reaction types, scattering physics, fission reactions, etc. This method is used because the fission kernel is a complex, 7-dimensional operator that is not explicitly known. Deterministic methods use approximations/discretization in energy, space, and direction to the kernel. Consequently, they are faster. Monte Carlo directly simulates the physics, which necessitates the use of random sampling. Because of this statistical noise, common convergence acceleration methods used in deterministic methods do not work. In the fission matrix method, we are using the random walk information not only to build the next-iteration fission source, but also a spatially-averaged fission kernel. Just like in deterministic methods, this involves approximation and discretization. The approximation is the tallying of the spatially-discretized fission kernel with an incorrect fission source. We address this by making the spatial mesh fine enough that this error is negligible. As a consequence of discretization we get a spatially low-order kernel, the fundamental eigenvector of which should converge faster than that of continuous kernel. We can then redistribute the fission bank to match the fundamental fission matrix eigenvector, effectively eliminating all higher modes. For all computations here biasing is not used, with the intention of comparing the unaltered, conventional Monte Carlo process with the fission matrix results. The source convergence of standard Monte Carlo criticality calculations are, to some extent, always subject to the characteristics of the problem. This method seeks to partially eliminate this problem-dependence by directly calculating the spatial coupling. The primary cost of this, which has prevented widespread use since its inception [2,3,4], is the extra storage required. To account for the coupling of all N spatial regions to every other region requires storing N{sup 2} values. For realistic problems, where a fine resolution is required for the suppression of discretization error, the storage becomes inordinate. Two factors lead to a renewed interest here: the larger memory available on modern computers and the development of a better storage scheme based on physical intuition. When the distance between source and fission events is short compared with the size of the entire system, saving memory by accounting for only local coupling introduces little extra error. We can gain other information from directly tallying the fission kernel: higher eigenmodes and eigenvalues. Conventional Monte Carlo cannot calculate this data - here we have a way to get new information for multiplying systems. In Ref. [5], higher mode eigenfunctions are analyzed for a three-region 1-dimensional problem and 2-dimensional homogenous problem. We analyze higher modes for more realistic problems. There is also the question of practical use of this information; here we examine a way of using eigenmode information to address the negative confidence interval bias due to inter-cycle correlation. We apply this method mainly to four problems: 2D pressurized water reactor (PWR) [6],

  6. Ternary and quaternary antimonide devices for thermophotovoltaic applications

    NASA Astrophysics Data System (ADS)

    Hitchcock, C. W.; Gutmann, R. J.; Ehsani, H.; Bhat, I. B.; Wang, C. A.; Freeman, M. J.; Charache, G. W.

    1998-12-01

    Thermophotovoltaic (TPV) devices have been fabricated using epitaxial ternary and quaternary layers grown on GaSb substrates. GaInSb ternary devices were grown by metalorganic vapor-phase epitaxy (MOVPE) with buffer layers to accommodate the lattice mismatch, and GaInAsSb lattice-matched quaternaries were grown by MOVPE and by liquid-phase epitaxy (LPE). Improved devices are obtained when optical absorption occurs in the p-layer due to the longer minority carrier diffusion length. Thick emitter p/n devices are limited by surface recombination, with highest quantum efficiency and lowest dark current being achieved with epitaxially grown surface passivation layers on lattice-matched MOVPE quaternaries. Thin emitter/thick base n/p devices are very promising, but require improved shallow high-quality n-type ohmic contacts.

  7. Quaternary naltrexone reverses radiogenic and morphine-induced locomotor hyperactivity

    SciTech Connect

    Mickley, G.A.; Stevens, K.E.; Galbraith, J.A.; White, G.A.; Gibbs, G.L.

    1984-04-01

    The present study attempted to determine the relative role of the peripheral and central nervous system in the production of morphine-induced or radiation-induced locomotor hyperactivity of the mouse. Toward this end, we used a quaternary derivative of an opiate antagonist (naltrexone methobromide), which presumably does not cross the blood-brain barrier. Quaternary naltrexone was used to challenge the stereotypic locomotor response observed in these mice after either an i.p. injection of morphine or exposure to 1500 rads /sup 60/Co. The quaternary derivative of naltrexone reversed the locomotor hyperactivity normally observed in the C57BL/6J mouse after an injection of morphine. It also significantly attenuated radiation-induced locomotion. The data reported here support the hypothesis of endorphin involvement in radiation-induced and radiogenic behaviors. However, these conclusions are contingent upon further research which more fully evaluates naltrexone methobromide's capacity to cross the blood-brain barrier.

  8. Ternary and quaternary antimonide devices for thermophotovoltaic applications

    SciTech Connect

    Hitchcock, C.W.; Gutmann, R.J.; Ehsani, H.; Bhat, I.B.; Wang, C.A.; Freeman, M.J.; Charache, G.W.

    1998-06-01

    Thermophotovoltaic (TPV) devices have been fabricated using epitaxial ternary and quaternary layers grown on GaSb substrates. GaInSb ternary devices were grown by metalorganic vapor phase epitaxy (MOVPE) with buffer layers to accommodate the lattice mismatch, and GaInAsSb lattice-matched quaternaries were grown by MOVPE and by liquid phase epitaxy (LPE). Improved devices are obtained when optical absorption occurs in the p-layer due to the longer minority carrier diffusion length. Thick emitter p/n devices are limited by surface recombination, with highest quantum efficiency and lowest dark current being achieved with epitaxially grown surface passivation layers on lattice-matched MOVPE quaternaries. Thin emitter/thick base n/p devices are very promising, but require improved shallow high-quality n-type ohmic contacts.

  9. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Quaternary ammonium salt of... New Uses for Specific Chemical Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl... identified generically as quaternary ammonium salt of fluorinated alkylaryl amide (PMN No. P-92-688)...

  10. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Quaternary ammonium salt of... New Uses for Specific Chemical Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl... identified generically as quaternary ammonium salt of fluorinated alkylaryl amide (PMN No. P-92-688)...

  11. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Quaternary ammonium salt of... New Uses for Specific Chemical Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl... identified generically as quaternary ammonium salt of fluorinated alkylaryl amide (PMN No. P-92-688)...

  12. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Quaternary ammonium salt of... New Uses for Specific Chemical Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl... identified generically as quaternary ammonium salt of fluorinated alkylaryl amide (PMN No. P-92-688)...

  13. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Quaternary ammonium salt of... New Uses for Specific Chemical Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl... identified generically as quaternary ammonium salt of fluorinated alkylaryl amide (PMN No. P-92-688)...

  14. 40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 2011-07-01 false Modified polymer of vinyl acetate and quaternary ammonium...Chemical Substances § 721.8658 Modified polymer of vinyl acetate and quaternary ammonium...substance identified generically as modified polymer of vinyl acetate and quaternary...

  15. 40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 2010-07-01 false Modified polymer of vinyl acetate and quaternary ammonium...Chemical Substances § 721.8658 Modified polymer of vinyl acetate and quaternary ammonium...substance identified generically as modified polymer of vinyl acetate and quaternary...

  16. 40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 false Modified polymer of vinyl acetate and quaternary ammonium...Chemical Substances § 721.8658 Modified polymer of vinyl acetate and quaternary ammonium...substance identified generically as modified polymer of vinyl acetate and quaternary...

  17. Fission target handling systemFission target handling system L. Serbina, E. Udup, F. Negoita (NIPNE-Bucharest)

    E-print Network

    McDonald, Kirk

    IFIN-HH Fission target handling systemFission target handling system L. Serbina, E. Udup, F cell entranceHot cell entrance Spent fission targets area F. Negoita, negoita water F. Negoita, negoita@tandem.nipne.roEURISOL-DS Task 4 Meeting, Legnaro, 19/09/2008 Fission targets

  18. Ice Age Earth: Late Quaternary geology and climate

    SciTech Connect

    Dawson, A.G.

    1992-01-01

    This book is a concise and readable account of the most important geologic records of the late Quaternary. It provides a synopsis of the major environmental changes that took place from approximately 13,000 to 7,000 years ago, highlighting the complexity and rapidity of past climate changes and the environmental responses they produced. The text is well illustrated, though some figures are rough and need more explanation. Also needed is a critical appraisal of the geochronology which places the paleoenvironmental records into the temporal domain. However, as a whole the book reaches its objective of summarizing the most important scientific findings about the nature of the late Quaternary climate changes.

  19. Fission barrier, damping of shell correction, and neutron emission in the fission of A ˜200

    NASA Astrophysics Data System (ADS)

    Mahata, K.; Kailas, S.; Kapoor, S. S.

    2015-09-01

    Decay of 210Po compound nucleus formed in light- and heavy-ion induced fusion reactions has been analyzed simultaneously using a consistent prescription for fission barrier and nuclear level density incorporating shell correction and its damping with excitation energy. Good descriptions of all the excitation functions have been achieved with a fission barrier of 21.9 ±0.2 MeV, indicating no significant shell correction at the saddle point. For this barrier height, the predicted statistical prefission neutrons in heavy-ion fusion-fission are much smaller than the experimental values, implying the presence of dynamical neutrons due to dissipation even at these low excitation energies (˜50 MeV ) in the mass region A ˜200 . When only heavy-ion induced fission excitation functions and the prefission neutron multiplicities are included in the fits, the deduced best-fit fission barrier depends on the assumed fission delay time, during which dynamical neutrons can be emitted. A fission delay of (0.8 ±0.1 ) ×10-19 s has been estimated corresponding to the above fission barrier height, assuming that the entire excess neutrons over and above the statistical model predictions are due to the dynamics. The present observation has implication on the study of fission time scale and nuclear viscosity using neutron emission as a probe.

  20. Characterization of Quaternary and suspected Quaternary faults, Amargosa area, Nevada and California

    SciTech Connect

    Anderson, R.E.; Crone, A.J.; Machette, M.N.; Bradley, L.A.; Diehl, S.F.

    1995-12-31

    This report presents the results of geologic studies that help define the Quaternary history of selected faults in the region around Yucca Mountain, Nevada. These results are relevant to the seismic-design basis of a potential nuclear waste repository at Yucca Mountain. The relevancy is based, in part, on a need for additional geologic data that became apparent in ongoing studies by S. Pezzopane (written commun., 1995) that resulted in the identification of 51 relevant and potentially relevant (see appendix A for definitions) individual and compound faults and fault zones in the 100-km-radius region around the Yucca Mountain site. These structures were divided into local and regional categories by Pezzopane (1995); this report deals with selected regional structures. In this introduction, the authors outline the scope and strategy of the studies and the tectonic environment of the studied structures.

  1. Microscopic description of complex nuclear decay: Multimodal fission

    SciTech Connect

    Staszczak, A.; Baran, A.; Dobaczewski, J.; Nazarewicz, W.

    2009-07-15

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  2. Microscopic description of complex nuclear decay: multimodal fission

    E-print Network

    Staszczak, A; Dobaczewski, J; Nazarewicz, W

    2009-01-01

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  3. Microscopic description of complex nuclear decay: Multimodal fission

    NASA Astrophysics Data System (ADS)

    Staszczak, A.; Baran, A.; Dobaczewski, J.; Nazarewicz, W.

    2009-07-01

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  4. Microscopic description of complex nuclear decay: multimodal fission

    E-print Network

    A. Staszczak; A. Baran; J. Dobaczewski; W. Nazarewicz

    2009-06-23

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  5. Advanced modeling of prompt fission neutrons

    SciTech Connect

    Talou, Patrick

    2009-01-01

    Theoretical and numerical studies of prompt fission neutrons are presented. The main results of the Los Alamos model often used in nuclear data evaluation work are reviewed briefly, and a preliminary assessment of uncertainties associated with the evaluated prompt fission neutron spectrum for n (0.5 MeV)+{sup 239}Pu is discussed. Advanced modeling of prompt fission neutrons is done by Monte Carlo simulations of the evaporation process of the excited primary fission fragments. The successive emissions of neutrons are followed in the statistical formalism framework, and detailed information, beyond average quantities, can be inferred. This approach is applied to the following reactions: {sup 252}Cf (sf), n{sub th} + {sup 239}Pu, n (0.5 MeV)+{sup 235}U, and {sup 236}Pu (sf). A discussion on the merits and present limitations of this approach concludes this presentation.

  6. Electron spectra from decay of fission products

    SciTech Connect

    Dickens, J K

    1982-09-01

    Electron spectra following decay of individual fission products (72 less than or equal to A less than or equal to 162) are obtained from the nuclear data given in the compilation using a listed and documented computer subroutine. Data are given for more than 500 radionuclides created during or after fission. The data include transition energies, absolute intensities, and shape parameters when known. An average beta-ray energy is given for fission products lacking experimental information on transition energies and intensities. For fission products having partial or incomplete decay information, the available data are utilized to provide best estimates of otherwise unknown decay schemes. This compilation is completely referenced and includes data available in the reviewed literature up to January 1982.

  7. Nuclear fission as resonance-mediated conductance

    E-print Network

    G. F. Bertsch

    2014-12-18

    For 75 years the theory of nuclear fission has been based on the existence of a collective coordinate associated with the nuclear shape, an assumption required by the Bohr-Wheeler formula as well as by the R-matrix theory of fission. We show that it is also possible to formulate the theory without the help of collective coordinates. In the new formulation, fission is facilitated by individual states in the barrier region rather than channels over the barrier. In a certain limit the theory reduces to a formula closely related to the formula for electronic conductance through resonant tunneling states. In contrast, conduction through channels gives rise to a staircase excitation function that is well-known in nanoscale electronics but has never been seen in nuclear fission.

  8. The Fission Time Projection Chamber Project

    NASA Astrophysics Data System (ADS)

    Hill, Tony

    2009-10-01

    New high-precision fission experiments have become a priority within the low-energy nuclear community. Modern sensitivity calculations have revealed unacceptable liabilities in some of the underlying fundamental nuclear data and have provided target accuracies for new measurements that are well beyond what can be delivered using current experimental technologies. A potential breakthrough in the precision barrier for these measurements is the deployment of a Time Projection Chamber (TPC). TPC detector systems were originally developed within the particle physics community and have played a central role in that field for nearly 25 years. A group of 6 universities and 3 national laboratories have undertaken the task of building the first TPC designed specifically for the purpose of measuring fission cross sections. In this talk, I will present the motivation for the fission TPC concept, a few details of the device and why we think an improvement on 50 years of fission experiments can be accomplished.

  9. Aqueous cutting fluid for machining fissionable materials

    DOEpatents

    Duerksen, Walter K. (Norris, TN); Googin, John M. (Oak Ridge, TN); Napier, Jr., Bradley (Powell, TN)

    1984-01-01

    The present invention is directed to a cutting fluid for machining fissionable material. The cutting fluid is formed of glycol, water and boron compound in an adequate concentration for effective neutron attenuation so as to inhibit criticality incidents during machining.

  10. Comparative Functional Genomics of the Fission Yeasts

    E-print Network

    Regev, Aviv

    The fission yeast clade—comprising Schizosaccharomyces pombe, S. octosporus, S. cryophilus, and S. japonicus—occupies the basal branch of Ascomycete fungi and is an important model of eukaryote biology. A comparative ...

  11. Fission Barriers of Compound Superheavy Nuclei

    E-print Network

    Sheikh, J. A.

    The dependence of fission barriers on the excitation energy of the compound nucleus impacts the survival probability of superheavy nuclei synthesized in heavy-ion fusion reactions. In this work, we investigate the isentropic ...

  12. Porous fission fragment tracks in fluorapatite

    SciTech Connect

    Li Weixing; Ewing, Rodney C.; Wang Lumin; Sun Kai; Lang, Maik; Trautmann, Christina

    2010-10-01

    Fission tracks caused by the spontaneous fission of {sup 238}U in minerals, as revealed by chemical etching, are extensively used to determine the age and thermal history of Earth's crust. Details of the structure and annealing of tracks at the atomic scale have remained elusive, as the original track is destroyed during chemical etching. By combining transmission electron microscopy with in situ heating, we demonstrate that fission tracks in fluorapatite are actually porous tubes, instead of having an amorphous core, as generally assumed. Direct observation shows thermally induced track fragmentation in fluoapatite, in clear contrast to the amorphous tracks in zircon, which gradually ''fade'' without fragmentation. Rayleigh instability and the thermal emission of vacancies control the annealing of porous fission tracks in fluorapatite.

  13. Our 50-year odyssey with fission: Summary

    SciTech Connect

    Nix, J.R.

    1989-01-01

    On the occasion of this International Conference on Fifty Years Research in Nuclear Fission, we summarize our present understanding of the fission process and the challenges that lie ahead. The basic properties of fission arise from a delicate competition between disruptive Coulomb forces, cohesive nuclear forces, and fluctuating shell and pairing forces. These static forces are primarily responsible for such experimental phenomena as deformed ground-state nuclear shapes, fission into fragments of unequal size, sawtooth neutron yields, spontaneously fissioning isomers, broad resonances and narrow intermediate structure in fission cross sections, and cluster radioactivity. However, inertial and dissipative forces also play decisive roles in the dynamical evolution of a fissioning nucleus. The energy dissipated between the saddle and scission points is small for low initial excitation energy at the saddle point and increases with increasing excitation energy. At moderate excitation energies, the dissipation of collective energy into internal single-particle excitation energy proceeds largely through the interaction of nucleons with the mean field and with each other in the vicinity of the nuclear surface, as well as through the transfer of nucleons between the two portions of the evolving dumbell-like system. These unique dissipation mechanisms arise from the Pauli exclusion principle for fermions and the details of the nucleon-nucleon interaction, which make the mean free path of a nucleon near the Fermi surface at low excitation energy longer than the nuclear radius. With its inverse process of heavy-ion fusion reactions, fission continues to yield surprises in the study of large-amplitude collective nuclear motion. 87 refs., 12 figs.

  14. Modeling Fission Product Sorption in Graphite Structures

    SciTech Connect

    Szlufarska, Izabela; Morgan, Dane; Allen, Todd

    2013-04-08

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high- temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission products on each type of graphite site. The model will include multiple simultaneous adsorbing species, which will allow for competitive adsorption effects between different fission product species and O and OH (for modeling accident conditions).

  15. Microscopic Theory of Nuclear Fission: A Review

    E-print Network

    N. Schunck; L. M. Robledo

    2015-11-24

    This article reviews how nuclear fission is described within nuclear density functional theory. In spontaneous fission, half-lives are the main observables and quantum tunnelling the essential concept, while in induced fission the focus is on fragment properties and explicitly time-dependent approaches are needed. The cornerstone of the current microscopic theory of fission is the energy density functional formalism. Its basic tenets, including tools such as the HFB theory, effective two-body effective nuclear potentials, finite-temperature extensions and beyond mean-field corrections, are presented succinctly. The EDF approach is often combined with the hypothesis that the time-scale of the large amplitude collective motion driving the system to fission is slow compared to typical time-scales of nucleons inside the nucleus. In practice, this hypothesis of adiabaticity is implemented by introducing (a few) collective variables and mapping out the many-body Schr\\"odinger equation into a collective Schr\\"odinger-like equation for the nuclear wave-packet. Scission configurations indicate where the split occurs. This collective Schr\\"odinger equation depends on an inertia tensor that includes the response of the system to small changes in the collective variables and also plays a special role in the determination of spontaneous fission half-lives. A trademark of the microscopic theory of fission is the tremendous amount of computing needed for practical applications. In particular, the successful implementation of the theories presented in this article requires a very precise numerical resolution of the HFB equations for large values of the collective variables. Finally, a selection of the most recent and representative results obtained for both spontaneous and induced fission is presented with the goal of emphasizing the coherence of the microscopic approaches employed.

  16. MCNP6 Fission Multiplicity with FMULT Card

    SciTech Connect

    Wilcox, Trevor; Fensin, Michael Lorne; Hendricks, John S.; James, Michael R.; McKinney, Gregg W.

    2012-06-18

    With the merger of MCNPX and MCNP5 into MCNP6, MCNP6 now provides all the capabilities of both codes allowing the user to access all the fission multiplicity data sets. Detailed in this paper is: (1) the new FMULT card capabilities for accessing these different data sets; (2) benchmark calculations, as compared to experiment, detailing the results of selecting these separate data sets for thermal neutron induced fission on U-235.

  17. A search for inverse fission of uranium

    SciTech Connect

    Yanez, R; Loveland, Walter; Beckerman, J.; Leonard, M.; Pettersson, G.; Gross, Carl J; Shapira, Dan; Liang, J Felix; Kohley, Zachary W; Varner Jr, Robert L

    2012-01-01

    There is a long-term interest in running the fission reaction backward, i.e., studying the 'inverse fission' of uranium. The recent availability of beams of n-rich fission fragments has stimulated interest in this endeavor. The purpose is to search for inverse fission in the reactions {sup 124,132}Sn + {sup 100}Mo. In the {sup 124}Sn + {sup 100}Mo reaction, evaporation residues were searched for using in-beam detection of evaporation residues, in-beam {alpha} spectroscopy, and post-irradiation {alpha} spectroscopy, while in the {sup 132}Sn + {sup 100}Mo reaction, the evaporation residue {sup 230}U was searched for using post-irradiation {alpha} spectroscopy. No evidence for the occurrence of the inverse fission reactions was found. The upper-limit cross section for the latter reaction is {approx}550 {mu}b, while the experimental upper-limit cross section for the former reaction is about 21{sup -21}{sup +38} nb. The intensity of suitable radioactive beams is not high enough at present to detect inverse fission. For the {sup 124}Sn + {sup 100}Mo reaction, the observed upper limits are below the estimates of current models for these reactions, probably due to fusion hindrance.

  18. Anatomy of neck configuration in fission decay

    E-print Network

    S. K. Patra; R. K. Choudhury; L. Satpathy

    2010-05-10

    The anatomy of neck configuration in the fission decay of Uranium and Thorium isotopes is investigated in a microscopic study using Relativistic mean field theory. The study includes $^{236}U$ and $^{232}Th$ in the valley of stability and exotic neutron rich isotopes $^{250}U$, $^{256}U$, $^{260}U$, $^{240}Th$, $^{250}Th$, $^{256}Th$ likely to play important role in the r-process nucleosynthesis in stellar evolution. Following the static fission path, the neck configurations are generated and their composition in terms of the number of neutrons and protons are obtained showing the progressive rise in the neutron component with the increase of mass number. Strong correlation between the neutron multiplicity in the fission decay and the number of neutrons in the neck is seen. The maximum neutron-proton ratio is about 5 for $^{260}$U and $^{256}$Th suggestive of the break down of liquid-drop picture and inhibition of the fission decay in still heavier isotopes. Neck as precursor of a new mode of fission decay like multi-fragmentation fission may also be inferred from this study.

  19. Fission cross section measurements at LANSCE

    NASA Astrophysics Data System (ADS)

    Tovesson, Fredrik; Hill, Tony

    2009-10-01

    Neutron induced fission cross sections of actinides are measured at the Los Alamos Neutron Science Center (LANSCE) in support of the Advanced Fuel Cycle Initiative (AFCI) and the National Nuclear Security Administration (NNSA). Nuclear technologies are increasingly dependent on advanced simulations for design and licensing requirements, and nuclear cross section data are important input parameters for the simulation tools. Fast nuclear reactor and stockpile stewardship applications often share nuclear data needs and requirements, and the LANSCE neutron source is ideal for measuring many of these data. The fission cross section measurements are guided by sensitivity studies performed in support of the AFCI program, as well as requests from NNSA. Recent results for the Pu-239 and Pu-241 fission cross sections from 0.01 eV to 200 MeV will be presented, and the discrepancy with current evaluations of the Pu-241 fission cross section discussed. Ongoing activities to extend the fission program will be presented, such as the development of a Time Projection Chamber (TPC) to significantly improve the experimental accuracies in fission cross section measurements.

  20. Ionization Chamber for Prompt Fission Neutron Investigations

    NASA Astrophysics Data System (ADS)

    Zeynalov, Sh.; Zeynalova, O.; Hambsch, F.-J.; Sedyshev, P.; Shvetsov, V.

    In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy measurement. Correlated FF kinetic energies, their masses and the angle of FF in respect to the axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electronic circuitry and special multi-channel pulse processing apparatus. Mathematical formulae provided for FF angles measured in respect to the coordinate axes. It was shown how the point of fission fragments origin on the target plane may be determined using the same measured data. The last feature made the TIC a rather powerful tool for prompt fission neutron (PFN) emission investigation in event-by-event analysis of individual fission reactions from non- point fissile source. Position sensitive neutron induced fission detector for neutron-imaging applications with both thermal and low energy neutrons was found as another possible implementation of the designed TIC.

  1. Accurate fission data for nuclear safety

    E-print Network

    A. Solders; D. Gorelov; A. Jokinen; V. S. Kolhinen; M. Lantz; A. Mattera; H. Penttila; S. Pomp; V. Rakopoulos; S. Rinta-Antila

    2013-04-08

    The Accurate fission data for nuclear safety (AlFONS) project aims at high precision measurements of fission yields, using the renewed IGISOL mass separator facility in combination with a new high current light ion cyclotron at the University of Jyvaskyla. The 30 MeV proton beam will be used to create fast and thermal neutron spectra for the study of neutron induced fission yields. Thanks to a series of mass separating elements, culminating with the JYFLTRAP Penning trap, it is possible to achieve a mass resolving power in the order of a few hundred thousands. In this paper we present the experimental setup and the design of a neutron converter target for IGISOL. The goal is to have a flexible design. For studies of exotic nuclei far from stability a high neutron flux (10^12 neutrons/s) at energies 1 - 30 MeV is desired while for reactor applications neutron spectra that resembles those of thermal and fast nuclear reactors are preferred. It is also desirable to be able to produce (semi-)monoenergetic neutrons for benchmarking and to study the energy dependence of fission yields. The scientific program is extensive and is planed to start in 2013 with a measurement of isomeric yield ratios of proton induced fission in uranium. This will be followed by studies of independent yields of thermal and fast neutron induced fission of various actinides.

  2. Improved Calculation of Thermal Fission Energy

    E-print Network

    X. B. Ma; W. L. Zhong; L. Z. Wang; Y. X. Chen; J. Cao

    2013-06-30

    Thermal fission energy is one of the basic parameters needed in the calculation of antineutrino flux for reactor neutrino experiments. It is useful to improve the precision of the thermal fission energy calculation for current and future reactor neutrino experiments, which are aimed at more precise determination of neutrino oscillation parameters. In this article, we give new values for thermal fission energies of some common thermal reactor fuel isotopes, with improvements on three aspects. One is more recent input data acquired from updated nuclear databases. the second one is a consideration of the production yields of fission fragments from both thermal and fast incident neutrons for each of the four main fuel isotopes. The last one is more carefully calculation of the average energy taken away by antineutrinos in thermal fission with the comparison of antineutrino spectrum from different models. The change in calculated antineutrino flux due to the new values of thermal fission energy is about 0.32%, and the uncertainties of the new values are about 50% smaller.

  3. Isotopic fission fragment distributions as a deep probe to fusion-fission dynamics

    E-print Network

    F. Farget; M. Caamano; O. Delaune; O. B. Tarasov; X. Derkx; K. -H. Schmidt; A. M. Amthor; L. Audouin; C. -O. Bacri; G. Barreau; B. Bastin; D. Bazin; B. Blank; J. Benlliure; L. Caceres; E. Casarejos; A. Chibihi; B. Fernandez-Dominguez; L. Gaudefroy; C. Golabek; S. Grevy; B. Jurado; O. Kamalou; A. Lemasson; S. Lukyanov; W. Mittig; D. J. Morrissey; A. Navin; J. Pereira; L. Perrot; M. Rejmund; T. Roger; M. -G. Saint-Laurent; H. Savajols; C. Schmitt; B. M. Sherill; C. Stodel; J. Taieb; J. -C. Thomas; A. C. Villari

    2012-09-24

    During the fission process, the nucleus deforms and elongates up to the two fragments inception and their final separation at scission deformation. The evolution of the nucleus energy with deformation is determined by the macroscopic properties of the nucleus, and is also strongly influenced by the single-particle structure of the nucleus. The fission fragment distribution is a direct consequence of the deformation path the nucleus has encountered, and therefore is the most genuine experimental observation of the potential energy landscape of the deforming nucleus. Very asymmetric fusion-fission reactions at energy close to the Coulomb barrier, produce well-defined conditions of the compound nucleus formation, where processes such as quasi-fission, pre-equilibrium emission and incomplete fusion are negligible. In the same time, the excitation energy is sufficient to reduce significantly structural effects, and mostly the macroscopic part of the potential is responsible for the formation of the fission fragments. We use inverse kinematics combined with spectrometers to select and identify the fission fragments produced in $^{238}$U+$^{12}$C at a bombarding energy close to and well-above the Coulomb barrier. For the first time, the isotopic yields are measured over the complete atomic-number distribution, between Z=30 and Z=63. The experimental set-up also allows to identify transfer-induced reactions, which lead to low-energy fission where the nuclear shell structure shows a strong influence on the fission-fragment distributions. The resulting set of data gives the possibility to observe the fission fragment properties over a wide range of excitation energy, and they reveal the vanishing of the shell effects in the potential energy of the fissioning nucleus, as well as the influence of fission dynamics.

  4. I-NERI ANNUAL TECHNICAL PROGRESS REPORT: 2006-002-K, Separation of Fission Products from Molten LiCl-KCl Salt Used for Electrorefining of Metal Fuels

    SciTech Connect

    S. Frank

    2009-09-01

    An attractive alternative to the once-through disposal of electrorefiner salt is to selectively remove the active fission products from the salt and recycle the salt back to the electrorefiner (ER). This would allow salt reuse for some number of cycles before ultimate disposal of the salt in a ceramic waste form. Reuse of ER salt would, thus, greatly reduce the volume of ceramic waste produced during the pyroprocessing of spent nuclear fuel. This final portion of the joint I-NERI research project is to demonstrate the separation of fission products from molten ER salt by two methods previously selected during phase two (FY-08) of this project. The two methods selected were salt/zeolite contacting and rare-earth fission product precipitation by oxygen bubbling. The ER salt used in these tests came from the Mark-IV electrorefiner used to anodically dissolved driver fuel from the EBR-II reactor on the INL site. The tests were performed using the Hot Fuel Dissolution Apparatus (HFDA) located in the main cell of the Hot Fuels Examination Facility (HFEF) at the Materials and Fuels complex on the INL site. Results from these tests were evaluated during a joint meeting of KAERI and INL investigators to provide recommendations as to the future direction of fission product removal from electrorefiner salt that accumulate during spent fuel treatment. Additionally, work continued on kinetic measurements of surrogate quaternary salt systems to provide fundamental kinetics on the ion exchange system and to expand the equilibrium model system developed during the first two phases of this project. The specific objectives of the FY09 I-NERI research activities at the INL include the following: • Perform demonstration tests of the selected KAERI precipitation and INL salt/zeolite contacting processes for fission product removal using radioactive, fission product loaded ER salt • Continue kinetic studies of the quaternary Cs/Sr-LiCl-KCl system to determine the rate of ion exchange during the salt/zeolite contacting process • Compare the adsorption models to experimentally obtained, ER salt results • Evaluate results obtained from the oxygen precipitation and salt/zeolite ion exchange studies to determine the best processes for selective fission-product removal from electrorefiner salt.

  5. Fission neutron source in Rome

    NASA Astrophysics Data System (ADS)

    Coppola, Mario; Di Majo, V.; Ingrao, G.; Rebessi, S.; Testa, A.

    1997-02-01

    A fission neutron source is operating in Rome at the ENEA Casaccia Research Center since 1971, consisting of a low power fast reactor named RSV-Tapiro. it is employed for a variety of experiments, including dosimetry, material testing, radiation protection and biology. In particular, application to experimental radiobiology includes studies of the biological action of neutrons in the whole-body irradiated animal, or in specialized systems in vivo or in vitro. For his purpose a vertical irradiation facility was originally constructed. Recently, a new horizontal irradiation facility has been designed to allow the exposure of larger samples or larger sample batches at one time. Dosimetry at the sample irradiation positions is routinely carried out by the conventional method of using two ion chambers. This physical dosimetry has recently been compared with the results of biological dosimetry based on the detection of chromosomal aberrations in peripheral blood human lymphocytes irradiated in vitro. A characterization of the radiation quality in the two configurations has been carried out by tissue equivalent proportional counter microdosimetry measurements. Information about the main characteristics of the reactor and the two irradiation facilities is provided and relevant results of the various measurements are summarized. Radiobiological results obtained using this neutron source are also briefly outlined.

  6. Quaternary International 90 (2002) 4156 Incipient tunnel channels

    E-print Network

    Fisher, Timothy G.

    2002-01-01

    Quaternary International 90 (2002) 41­56 Incipient tunnel channels Darren B. Sjogrena, *, Timothy G are often interpreted as tunnel channels or subaerial channels, partly filled with sediment from erosion. We conclude that the erosion of these linked pothole channels (incipient tunnel channels

  7. Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information

    ERIC Educational Resources Information Center

    Oehlke, Betsy M.; Dolliver, Holly A. S.

    2011-01-01

    The majority of soils in the western Wisconsin have developed from glacial sediments deposited during the Quaternary Period (2.6 million years before present). In many regions, multiple advances and retreats have left a complex landscape of diverse glacial sediments and landforms. The soils that have developed on these deposits reflect the nature…

  8. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Quaternary ammonium chloride combination. 172.165 Section 172.165 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives §...

  9. QUATERNARY RESEARCH 45, 282288 (1996) ARTICLE NO. 0029

    E-print Network

    Amundson, Ronald

    1996-01-01

    process. The apparent ages deduced from Radiocarbon ages of soil organic matter are evaluatedQUATERNARY RESEARCH 45, 282­288 (1996) ARTICLE NO. 0029 Radiocarbon Dating of Soil Organic Matter Hall, University of California, Berkeley, California 94720 AND SUSAN TRUMBORE Department of Earth

  10. Synthesis of Adjacent Quaternary Stereocenters by Catalytic Asymmetric Allylboration.

    PubMed

    Alam, Rauful; Vollgraff, Tobias; Eriksson, Lars; Szabó, Kálmán J

    2015-09-01

    Allylboration of ketones with ?-disubstituted allylboronic acids is performed in the presence of chiral BINOL derivatives. The reaction is suitable for single-step creation of adjacent quaternary stereocenters with high selectivity. We show that, with an appropriate choice of the chiral catalyst and the stereoisomeric prenyl substrate, full control of the stereo- and enantioselectivity is possible in the reaction. PMID:26316158

  11. Enantioselective Construction of ?-Quaternary Cyclobutanones by Catalytic Asymmetric Allylic Alkylation**

    PubMed Central

    Reeves, Corey M.; Eidamshaus, Christian; Kim, Jimin; Stoltz, Brian M.

    2013-01-01

    No Strain, No Gain! The first transition metal-catalyzed enantioselective ?-alkylation of cyclobutanones is reported. This method employs palladium catalysis and an electron deficient PHOX type ligand to afford all–carbon ?-quaternary cyclobutanones in good to excellent yields and enantioselectivities. PMID:23686812

  12. Historical distribution of Sundaland's Dipterocarp rainforests at Quaternary glacial maxima

    E-print Network

    Slik, Ferry

    Historical distribution of Sundaland's Dipterocarp rainforests at Quaternary glacial maxima Niels, 2014 (received for review February 21, 2014) The extent of Dipterocarp rainforests on the emergent the rainforests of Sundaland, and their distributions serve as a proxy for rainforest extent. We used species

  13. Minimal erosion of Arctic alpine topography during late Quaternary glaciation

    NASA Astrophysics Data System (ADS)

    Gjermundsen, Endre F.; Briner, Jason P.; Akçar, Naki; Foros, Jørn; Kubik, Peter W.; Salvigsen, Otto; Hormes, Anne

    2015-10-01

    The alpine topography observed in many mountainous regions is thought to have formed during repeated glaciations of the Quaternary period. Before this time, landscapes had much less relief. However, the spatial patterns and rates of Quaternary exhumation at high latitudes--where cold-based glaciers may protect rather than erode landscapes--are not fully quantified. Here we determine the exposure and burial histories of rock samples from eight summits of steep alpine peaks in northwestern Svalbard (79.5° N) using analyses of 10Be and 26Al concentrations. We find that the summits have been preserved for at least the past one million years. The antiquity of Svalbard’s alpine landscape is supported by the preservation of sediments older than one million years along a fjord valley, which suggests that both mountain summits and low-elevation landscapes experienced very low erosion rates over the past million years. Our findings support the establishment of northwestern Svalbard’s alpine topography during the early Quaternary. We suggest that, as the Quaternary ice age progressed, glacial erosion in the Arctic became inefficient and confined to ice streams, and high-relief alpine landscapes were preserved by minimally erosive glacier armour.

  14. A new design of fission detector for prompt fission neutron investigation

    NASA Astrophysics Data System (ADS)

    Zeynalov, Sh.; Zeynalova, O.; Nazarenko, M. A.; Hambsch, F.-J.; Oberstedt, S.

    2012-10-01

    In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy spectroscopy. Correlated FF kinetic energies, their masses and the angle of the fission axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electronic circuitry and special multi-channel pulse processing apparatus. Mathematical algorithms were provided along with formulae derived for fission axis angles determination. It was shown how the point of fission fragments origin on the target plane may be determined using the same measured data. The last feature made the TIC a rather powerful tool for prompt fission neutron (PFN) emission investigation in event by event analysis of individual fission reactions from non point fissile source. Position sensitive neutron induced fission detector for neutron imaging applications with both thermal and low energy neutrons was found as another possible implementation of the designed TIC.

  15. Microscopic Description of Nuclear Fission: Fission Barrier Heights of Even-Even Actinides

    E-print Network

    J. McDonnell; N. Schunck; W. Nazarewicz

    2013-01-31

    We evaluate the performance of modern nuclear energy density functionals for predicting inner and outer fission barrier heights and energies of fission isomers of even-even actinides. For isomer energies and outer barrier heights, we find that the self-consistent theory at the HFB level is capable of providing quantitative agreement with empirical data.

  16. Event-by-event fission simulation code, generates complete fission events

    Energy Science and Technology Software Center (ESTSC)

    2013-04-01

    FREYA is a computer code that generates complete fission events. The output includes the energy and momentum of these final state particles: fission products, prompt neutrons and prompt photons. The version of FREYA that is to be released is a module for MCNP6.

  17. Dual-fission chamber and neutron beam characterization for fission product yield measurements using monoenergetic neutrons

    NASA Astrophysics Data System (ADS)

    Bhatia, C.; Fallin, B.; Gooden, M. E.; Howell, C. R.; Kelley, J. H.; Tornow, W.; Arnold, C. W.; Bond, E. M.; Bredeweg, T. A.; Fowler, M. M.; Moody, W. A.; Rundberg, R. S.; Rusev, G.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Macri, R.; Ryan, C.; Sheets, S. A.; Stoyer, M. A.; Tonchev, A. P.

    2014-09-01

    A program has been initiated to measure the energy dependence of selected high-yield fission products used in the analysis of nuclear test data. We present out initial work of neutron activation using a dual-fission chamber with quasi-monoenergetic neutrons and gamma-counting method. Quasi-monoenergetic neutrons of energies from 0.5 to 15 MeV using the TUNL 10 MV FM tandem to provide high-precision and self-consistent measurements of fission product yields (FPY). The final FPY results will be coupled with theoretical analysis to provide a more fundamental understanding of the fission process. To accomplish this goal, we have developed and tested a set of dual-fission ionization chambers to provide an accurate determination of the number of fissions occurring in a thick target located in the middle plane of the chamber assembly. Details of the fission chamber and its performance are presented along with neutron beam production and characterization. Also presented are studies on the background issues associated with room-return and off-energy neutron production. We show that the off-energy neutron contribution can be significant, but correctable, while room-return neutron background levels contribute less than <1% to the fission signal.

  18. Measurement of the ?-decay to Spontaneous fission branching ratio of 252Cf with the NIFFTE Fission Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Snyder, Lucas; Niffte Collaboration

    2013-10-01

    Neutron-induced fission cross sections are of particular importance when simulating and modeling nuclear fuel cycles. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration is developing a fission Time Projection Chamber (TPC) to measure neutron-induced fission cross sections with total uncertainty of better than 1 %. To achieve such precision, the systematic uncertainties of the previously used measurement techniques must be addressed. The fission TPC will do this, in part, by providing detailed 3-dimensional images of fission fragments and other charged-particles produced in a neutron beam environment. Throughout the fission TPC's development phase the ?-decay and spontaneous fission of 252Cf has been used to benchmark its performance. Recently the first 252Cf data were collected using the fully instrumented fission TPC, which has nearly 6000 individual channels and provides 4 ? coverage. A preliminary analysis of the ?/SF branching ratio will be presented.

  19. Options For Development of Space Fission Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Houta, Mike; VanDyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Salvail, Pat; Hrbud, Ivana; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    Fission technology can enable rapid, affordable access to any point in the solar system. Potential fission-based transportation options include high specific power continuous impulse propulsion systems and bimodal nuclear thermal rockets. Despite their tremendous potential for enhancing or enabling deep space and planetary missions, to date space fission system have only been used in Earth orbit. The first step towards utilizing advanced fission propulsion systems is development of a safe, near-term, affordable fission system that can enhance or enable near-term missions of interest. An evolutionary approach for developing space fission propulsion systems is proposed.

  20. Options for development of space fission propulsion systems

    NASA Astrophysics Data System (ADS)

    Houts, Mike; van Dyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Salvail, Pat; Hrbud, Ivana

    2001-02-01

    Fission technology can enable rapid, affordable access to any point in the solar system. Potential fission-based transportation options include high specific power continuous impulse propulsion systems and bimodal nuclear thermal rockets. Despite their tremendous potential for enhancing or enabling deep space and planetary missions, to date space fission systems have only been used in Earth orbit. The first step towards utilizing advanced fission propulsion systems is development of a safe, near-term, affordable fission system that can enhance or enable near-term missions of interest. An evolutionary approach for developing space fission propulsion systems is proposed. .

  1. Bimodal fission in the Skyrme-Hartree-Fock approach

    E-print Network

    A. Staszczak; J. Dobaczewski; W. Nazarewicz

    2006-12-04

    Spontaneous-fission properties of 256Fm, 258Fm, and 260Fm isotopes are studied within the Skyrme-Hartree-Fock+BCS framework. In the particle-hole channel we take the Skyrme SkM* effective force, while in the particle-particle channel we employ the seniority pairing interaction. Three static fission paths for all investigated heavy fermium isotopes are found. The analysis of these fission modes allows to describe observed asymmetric fission of 256Fm, as well as bimodal fission of 258Fm and symmetric fission in 260Fm.

  2. Utilization of fission reactors for fusion engineering testing

    SciTech Connect

    Deis, G.A.; Miller, L.G.

    1985-02-08

    Fission reactors can be used to conduct some of the fusion nuclear engineering tests identified in the FINESSE study. To further define the advantages and disadvantages of fission testing, the technical and programmatic constraints on this type of testing are discussed here. This paper presents and discusses eight key issues affecting fission utilization. Quantitative comparisons with projected fusion operation are made to determine the technical assets and limitations of fission testing. Capabilities of existing fission reactors are summarized and compared with technical needs. Conclusions are then presented on the areas where fission testing can be most useful.

  3. Fission Surface Power Technology Development Update

    NASA Technical Reports Server (NTRS)

    Palac, Donald T.; Mason, Lee S.; Houts, Michael G.; Harlow, Scott

    2011-01-01

    Power is a critical consideration in planning exploration of the surfaces of the Moon, Mars, and places beyond. Nuclear power is an important option, especially for locations in the solar system where sunlight is limited or environmental conditions are challenging (e.g., extreme cold, dust storms). NASA and the Department of Energy are maintaining the option for fission surface power for the Moon and Mars by developing and demonstrating technology for a fission surface power system. The Fission Surface Power Systems project has focused on subscale component and subsystem demonstrations to address the feasibility of a low-risk, low-cost approach to space nuclear power for surface missions. Laboratory demonstrations of the liquid metal pump, reactor control drum drive, power conversion, heat rejection, and power management and distribution technologies have validated that the fundamental characteristics and performance of these components and subsystems are consistent with a Fission Surface Power preliminary reference concept. In addition, subscale versions of a non-nuclear reactor simulator, using electric resistance heating in place of the reactor fuel, have been built and operated with liquid metal sodium-potassium and helium/xenon gas heat transfer loops, demonstrating the viability of establishing system-level performance and characteristics of fission surface power technologies without requiring a nuclear reactor. While some component and subsystem testing will continue through 2011 and beyond, the results to date provide sufficient confidence to proceed with system level technology readiness demonstration. To demonstrate the system level readiness of fission surface power in an operationally relevant environment (the primary goal of the Fission Surface Power Systems project), a full scale, 1/4 power Technology Demonstration Unit (TDU) is under development. The TDU will consist of a non-nuclear reactor simulator, a sodium-potassium heat transfer loop, a power conversion unit with electrical controls, and a heat rejection system with a multi-panel radiator assembly. Testing is planned at the Glenn Research Center Vacuum Facility 6 starting in 2012, with vacuum and liquid-nitrogen cold walls to provide simulation of operationally relevant environments. A nominal two-year test campaign is planned including a Phase 1 reactor simulator and power conversion test followed by a Phase 2 integrated system test with radiator panel heat rejection. The testing is expected to demonstrate the readiness and availability of fission surface power as a viable power system option for NASA's exploration needs. In addition to surface power, technology development work within this project is also directly applicable to in-space fission power and propulsion systems.

  4. Theory of neutron emission in fission

    SciTech Connect

    Madland, D.G.

    1998-08-01

    A survey of theoretical representations of two of the observables in neutron emission in fission is given, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity {bar {nu}}{sub p}. Early representations of the two observables are presented and their deficiencies are discussed. This is followed by summaries and some examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the recent models. In particular, the dependencies of N(E) and {bar {nu}}{sub p} upon the fissioning nucleus and its excitation energy are treated in detail for the Los Alamos model. Recent work in the calculation of the prompt fission neutron spectrum matrix N(E, E{sub n}), where E{sub n} is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of the ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches. This paper is an extension of a similar paper presented at the International Centre for Theoretical Physics in 1996.

  5. Characterization of Quaternary and suspected Quaternary faults, regional studies, Nevada and California

    SciTech Connect

    Anderson, R.E.; Bucknam, R.C.; Crone, A.J.; Haller, K.M.; Machette, M.N.; Personius, S.F.; Barnhard, T.P.; Cecil, M.J.; Dart, R.L.

    1995-12-31

    This report presents the results of geologic studies that help define the Quaternary history of selected faults in the region around Yucca Mountain, Nevada. These results are relevant to the seismic-design basis of a potential nuclear waste repository at Yucca Mountain. The relevancy is based, in part, on a need for additional geologic data that became apparent in ongoing studies that resulted in the identification of 51 relevant and potentially relevant individual and compound faults and fault zones in the 100-km-radius region around the Yucca Mountain site. Geologic data used to characterize the regional faults and fault zones as relevant or potentially relevant seismic sources includes age and displacement information, maximum fault lengths, and minimum distances between the fault and the Yucca Mountain site. For many of the regional faults, no paleoseismic field studies have previously been conducted, and age and displacement data are sparse to nonexistent. In November 1994, the Branch of Earthquake and Landslide Hazards entered into two Memoranda of Agreement with the Yucca Mountain Project Branch to conduct field reconnaissance, analysis, and interpretation of six relevant and six potentially relevant regional faults. This report describes the results of study of those faults exclusive of those in the Pahrump-Stewart Valley-Ash Meadows-Amargosa Valley areas. We also include results of a cursory study of faults on the west flank of the Specter Range and in the northern part of the Last Chance Range. A four-phase strategy was implemented for the field study.

  6. Solution-processable singlet fission photovoltaic devices.

    PubMed

    Yang, Le; Tabachnyk, Maxim; Bayliss, Sam L; Böhm, Marcus L; Broch, Katharina; Greenham, Neil C; Friend, Richard H; Ehrler, Bruno

    2015-01-14

    We demonstrate the successful incorporation of a solution-processable singlet fission material, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), into photovoltaic devices. TIPS-pentacene rapidly converts high-energy singlet excitons into pairs of triplet excitons via singlet fission, potentially doubling the photocurrent from high-energy photons. Low-energy photons are captured by small-bandgap electron-accepting lead chalcogenide nanocrystals. This is the first solution-processable singlet fission system that performs with substantial efficiency with maximum power conversion efficiencies exceeding 4.8%, and external quantum efficiencies of up to 60% in the TIPS-pentacene absorption range. With PbSe nanocrystal of suitable bandgap, its internal quantum efficiency reaches 170 ± 30%. PMID:25517654

  7. Fission of pre-actinide nuclei

    E-print Network

    A. Deppman; G. S. Karapetyan; V. Guimarães; C. Gonzales; A. R. Balabekyan; N. A. Demekhina

    2014-12-12

    A study of photofission on 181Ta nucleus induced by bremsstrahlung photons with endpoint energies of 50 and 3500 MeV has been performed. The fission yields have been measured by using the induced-activity method in an off-line analysis. The absolute photofission cross sections for the tantalum target at 50 and 3500 MeV are found to be 5.4 \\pm 1.1 microb and 0.77\\pm0.11 mb, respectively, and the corresponding deduced fissilities are (0.23\\pm0.05) x 10^{-3} and (2.9 \\pm 0.9) x 10^{-3}. Mass- and charge-yield distributions were derived from the data. The results were compared with the simulated results from CRISP code for multi-modal fission by assuming symmetrical fission mode.

  8. Application of Fission Chamber to Uranium Microanalysis

    NASA Astrophysics Data System (ADS)

    Yamada, Kimio; Izumi, Shigeru; Otsuka, Hisao; Matsumoto, Tetsuo

    1983-02-01

    The possibility of using a fission chamber for quantitative analysis of uranium impurity in dynamic memory materials was studied. The fission chamber had two pairs of parallel disk electrodes. One electrode of each pair was used as a collector and was made of Teflon with a pure aluminum coating, while the other electrode was the material to be measured. Carbon dioxide was used as the ionization gas. Uranium in the materials was irradiated with neutrons and the number of fissions was counted to give the impurity content. Uranium contents in aluminum (99.8%) and Teflon were calculated, and measured values showed a fairly good reproducibility. The detection limit, determined by background fluctuations, for uranium impurity contained in the aluminum coated Teflon electrode was 4.0 ppb.

  9. Fast multilayer fission chamber with 239Pu

    NASA Astrophysics Data System (ADS)

    Bogdzel, A. A.; Gundorin, N. A.; Duka-Zolyòmi, À.; Kliman, J.; Grigoriev, Yu. V.

    1994-04-01

    For the investigation of neutron induced fission of heavy nuclei in the resonance energy range the fast multilayer ionization fission chamber with a 239Pu content of 1.6 g was constructed. The chamber is compact and a minimum of material has been used for its construction. The chamber is divided into 19 sections containing no more than 100 mg of 239Pu in a section whose intrinsic capacity is less than 100 pF. By using fast preamplifiers and constant fraction discriminators together with the combined method of amplitude and pulse length discrimination the background due to ?-particles is suppressed and a less perturbed pulse height distribution is obtained. The absolute fission fragments detection efficiency of the chamber is (60±8)%. Its time resolution does not exceed 2.6 ns.

  10. Lunar surface fission power supplies: Radiation issues

    SciTech Connect

    Houts, M.G.; Lee, S.K.

    1994-07-01

    A lunar space fission power supply shield that uses a combination of lunar regolith and materials brought from earth may be optimal for early lunar outposts and bases. This type of shield can be designed such that the fission power supply does not have to be moved from its landing configuration, minimizing handling and required equipment on the lunar surface. Mechanisms for removing heat from the lunar regolith are built into the shield, and can be tested on earth. Regolith activation is greatly reduced compared with a shield that uses only regolith, and it is possible to keep the thermal conditions of the fission power supply close to these seen in free space. For a well designed shield, the additional mass required to be brought fro earth should be less than 1000 kg. Detailed radiation transport calculations confirm the feasibility of such a shield.

  11. Phase Transition Induced Fission in Lipid Vesicles

    E-print Network

    C. Leirer; B. Wunderlich; V. M. Myles; M. F. Schneider

    2010-05-24

    In this work we demonstrate how the first order phase transition in giant unilamellar vesicles (GUVs) can function as a trigger for membrane fission. When driven through their gel-fluid phase transition GUVs exhibit budding or pearl formation. These buds remain connected to the mother vesicle presumably by a small neck. Cooling these vesicles from the fluid phase (T>Tm) through the phase transition into the gel state (Tfission of the neck, while the mother vesicle remains intact. Pearling tubes which formed upon heating break-up and decay into multiple individual vesicles which then diffuse freely. Finally we demonstrate that mimicking the intracellular bulk viscosity by increasing the bulk viscosity to 40cP does not affect the overall fission process, but leads to a significant decrease in size of the released vesicles.

  12. Study on fission blanket fuel cycling of a fusion-fission hybrid energy generation system

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Yang, Y.; Xu, H.

    2011-10-01

    This paper presents a preliminary study on neutron physics characteristics of a light water cooled fission blanket for a new type subcritical fusion-fission hybrid reactor aiming at electric power generation with low technical limits of fission fuel. The major objective is to study the fission fuel cycling performance in the blanket, which may possess significant impacts on the feasibility of the new concept of fusion-fission hybrid reactor with a high energy gain (M) and tritium breeding ratio (TBR). The COUPLE2 code developed by the Institute of Nuclear and New Energy Technology of Tsinghua University is employed to simulate the neutronic behaviour in the blanket. COUPLE2 combines the particle transport code MCNPX with the fuel depletion code ORIGEN2. The code calculation results show that soft neutron spectrum can yield M > 20 while maintaining TBR >1.15 and the conversion ratio of fissile materials CR > 1 in a reasonably long refuelling cycle (>five years). The preliminary results also indicate that it is rather promising to design a high-performance light water cooled fission blanket of fusion-fission hybrid reactor for electric power generation by directly loading natural or depleted uranium if an ITER-scale tokamak fusion neutron source is achievable.

  13. Low-mass fission detector for the fission neutron spectrum measurement

    SciTech Connect

    Wu, C Y; Henderson, R; Gostic, J; Haight, R C; Lee, H Y

    2010-10-20

    For the fission neutron spectrum measurement, the neutron energy is determined in a time-of-flight experiment by the time difference between the fission event and detection of the neutron. Therefore, the neutron energy resolution is directly determined by the time resolution of both neutron and fission detectors. For the fission detection, the detector needs not only a good timing response but also the tolerance of radiation damage and high {alpha}-decay rate. A parallel-plate avalanche counter (PPAC) has many advantages for the detection of heavy charged particles such as fission fragments. These include fast timing, resistance to radiation damage, and tolerance of high counting rate. A PPAC also can be tuned to be insensitive to particles, which is important for experiments with - emitting actinides. Therefore, a PPAC is an ideal detector for experiments requiring a fast and clean trigger for fission. In the following sections, the description will be given for the design and performance of a new low-mass PPAC for the fission-neutron spectrum measurements at LANL.

  14. Fundamental Fission Research with the NIFFTE Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Kleinrath, Verena; Niffte Collaboration

    2013-10-01

    The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) has developed a novel instrument for fission research - a Time Projection Chamber (TPC), which enables detailed tracking of charged particles emitted in neutron-induced fission. While the primary goal of the project is to measure fission cross sections with unprecedented precision, the TPC can also facilitate more fundamental fission studies. The detector's high efficiency (4-pi acceptance) and precise tracking capabilities (including energy deposition) provide a large amount of valuable information. Recent data collected during engineering runs using a U238/U235 target will be used to generate fission fragment angular distributions and yields as a function of incident neutron energy. These experimental results can lend insight into the evolution of nuclear shapes with respect to energy on the path to scission and therefore immediately drive fission theory development. Preliminary angular distributions and yields using the NIFFTE TPC will be presented. Neutron Induced Fission Fragment Tracking Experiment.

  15. Italian hybrid and fission reactors scenario analysis

    SciTech Connect

    Ciotti, M.; Manzano, J.; Sepielli, M.

    2012-06-19

    Italy is a country where a long tradition of studies both in the fission and fusion field is consolidated; nevertheless a strong public opinion concerned with the destination of the Spent Nuclear Fuel hinders the development of nuclear power. The possibility to a severe reduction of the NSF mass generated from a fleet of nuclear reactors employing an hypothetical fusionfission hybrid reactor has been investigated in the Italian framework. The possibility to produce nuclear fuel for the fission nuclear reactors with the hybrid reactor was analyzed too.

  16. In-beam Fission Study at JAEA

    NASA Astrophysics Data System (ADS)

    Nishio, Katsuhisa

    2013-12-01

    Fission fragment mass distributions were measured in heavy-ion induced fissions using 238U target nucleus. The measured mass distributions changed drastically with incident energy. The results are explained by a change of the ratio between fusion and quasifission with nuclear orientation. A calculation based on a fluctuation dissipation model reproduced the mass distributions and their incident energy dependence. Fusion probability was determined in the analysis. Evaporation residue cross sections were calculated with a statistical model in the reactions of 30Si + 238U and 34S + 238U using the obtained fusion probability in the entrance channel. The results agree with the measured cross sections for seaborgium and hassium isotopes.

  17. Italian hybrid and fission reactors scenario analysis

    NASA Astrophysics Data System (ADS)

    Ciotti, M.; Manzano, J.; Sepielli, M.

    2012-06-01

    Italy is a country where a long tradition of studies both in the fission and fusion field is consolidated; nevertheless a strong public opinion concerned with the destination of the Spent Nuclear Fuel hinders the development of nuclear power. The possibility to a severe reduction of the NSF mass generated from a fleet of nuclear reactors employing an hypothetical fusionfission hybrid reactor has been investigated in the Italian framework. The possibility to produce nuclear fuel for the fission nuclear reactors with the hybrid reactor was analyzed too.

  18. Dynamic fission instability of dissipative protoplanets

    SciTech Connect

    Boss, A.P.; Mizuno, H.

    1985-07-01

    Analytical and numerical approaches are taken to consider if a rapidly rotating, viscous protoearth would have lost mass by a fission process and thereby given birth to the moon. The fast rotation is assumed as the source of the instability in the dissipative liquid protoearth. Governing hydrodynamic equations are defined for the evolution of the protoearth. Account is taken of viscous dissipation, the pressure equation of state for the atmospheric material sent on a ballistic trajectory, and the effective viscosity. The results indicate that dynamic fission was probably not the process by which the protomoon came into existence. 61 references.

  19. Fission Yeast Cell Cycle Synchronization Methods.

    PubMed

    Tormos-Pérez, Marta; Pérez-Hidalgo, Livia; Moreno, Sergio

    2016-01-01

    Fission yeast cells can be synchronized by cell cycle arrest and release or by size selection. Cell cycle arrest synchronization is based on the block and release of temperature-sensitive cell cycle mutants or treatment with drugs. The most widely used approaches are cdc10-129 for G1; hydroxyurea (HU) for early S-phase; cdc25-22 for G2, and nda3-KM311 for mitosis. Cells can also be synchronized by size selection using centrifugal elutriation or a lactose gradient. Here we describe the methods most commonly used to synchronize fission yeast cells. PMID:26519320

  20. Uncertainty Quantification on Prompt Fission Neutrons Spectra

    SciTech Connect

    Talou, P. Madland, D.G.; Kawano, T.

    2008-12-15

    Uncertainties in the evaluated prompt fission neutrons spectra present in ENDF/B-VII.0 are assessed in the framework of the Los Alamos model. The methodology used to quantify the uncertainties on an evaluated spectrum is introduced. We also briefly review the Los Alamos model and single out the parameters that have the largest influence on the calculated results. Using a Kalman filter, experimental data and uncertainties are introduced to constrain model parameters, and construct an evaluated covariance matrix for the prompt neutrons spectrum. Preliminary results are shown in the case of neutron-induced fission of {sup 235}U from thermal up to 15 MeV incident energies.

  1. Angular Momentum Distribution of Fission Fragments

    NASA Astrophysics Data System (ADS)

    Stetcu, I.; Talou, P.; Kawano, T.; Jandel, M.

    2014-04-01

    Latest generation fission experiments provide an excellent testing ground for theoretical models. In this contribution we compare the measurements obtained with the DANCE calorimeter at LANSCE with our full-scale simulation of the primary fragment de-excitation, using the recently developed CGMF code, based on a Monte-Carlo implementation of the Hauser-Feshbach theoretical model. We compute the isomeric ratios as a function of the initial angular momentum of the fission fragments. Comparison with the available experimental data allows us to determine the initial spin distribution. Finally, we study the sensitivity to the discrete spectra input.

  2. Fission-gas release from uranium nitride at high fission rate density

    NASA Technical Reports Server (NTRS)

    Weinstein, M. B.; Kirchgessner, T. A.; Tambling, T. N.

    1973-01-01

    A sweep gas facility has been used to measure the release rates of radioactive fission gases from small UN specimens irradiated to 8-percent burnup at high fission-rate densities. The measured release rates have been correlated with an equation whose terms correspond to direct recoil release, fission-enhanced diffusion, and atomic diffusion (a function of temperature). Release rates were found to increase linearly with burnups between 1.5 and 8 percent. Pore migration was observed after operation at 1550 K to over 6 percent burnup.

  3. Fission Decay Widths for Heavy-Ion Fusion-Fission Reactions

    E-print Network

    S. G. McCalla; J. P. Lestone

    2008-01-30

    Cross-section and neutron-emission data from heavy-ion fusion-fission reactions are consistent with a Kramers-modified statistical model which takes into account the collective motion of the system about the ground state; the temperature dependence of the location of fission transition points; and the orientation degree of freedom. We see no evidence to suggest that the nuclear viscosity departs from the surface-plus-window dissipation model. The strong increase in the nuclear viscosity above a temperature of ~1 MeV deduced by others is an artifact generated by an inadequate fission model.

  4. Optimally moderated nuclear fission reactor and fuel source therefor

    DOEpatents

    Ougouag, Abderrafi M. (Idaho Falls, ID); Terry, William K. (Shelley, ID); Gougar, Hans D. (Idaho Falls, ID)

    2008-07-22

    An improved nuclear fission reactor of the continuous fueling type involves determining an asymptotic equilibrium state for the nuclear fission reactor and providing the reactor with a moderator-to-fuel ratio that is optimally moderated for the asymptotic equilibrium state of the nuclear fission reactor; the fuel-to-moderator ratio allowing the nuclear fission reactor to be substantially continuously operated in an optimally moderated state.

  5. Development and Utilization of Space Fission Power Systems

    NASA Technical Reports Server (NTRS)

    Houts, Michael; Mason, Lee S.; Palac, Donald T.; Harlow, Scott E.

    2008-01-01

    Space fission power systems could enable advanced civilian space missions. Terrestrially, thousands of fission systems have been operated since 1942. In addition, the US flew a space fission system in 1965, and the former Soviet Union flew 33 such systems prior to the end of the Cold War. Modern design and development practices, coupled with 65 years of experience with terrestrial reactors, could enable the affordable development of space fission power systems for near-term planetary surface applications.

  6. Development and Utilization of Space Fission Power Systems

    NASA Technical Reports Server (NTRS)

    Houts, Michael G.; Mason, Lee S.; Palac, Donald T.; Harlow, Scott E.

    2009-01-01

    Space fission power systems could enable advanced civilian space missions. Terrestrially, thousands of fission systems have been operated since 1942. In addition, the US flew a space fission system in 1965, and the former Soviet Union flew 33 such systems prior to the end of the Cold War. Modern design and development practices, coupled with 65 years of experience with terrestrial reactors, could enable the affordable development of space fission power systems for near-term planetary surface applications.

  7. Fission barriers in a macroscopic-microscopic model

    SciTech Connect

    Dobrowolski, A.; Pomorski, K.; Bartel, J.

    2007-02-15

    In the framework of the macroscopic-microscopic model, this study investigates fission barriers in the region of actinide nuclei. A very effective four-dimensional shape parametrization for fissioning nuclei is proposed. Taking, in particular, the left-right mass asymmetric and nonaxial shapes into account is demonstrated to have a substantial effect on fission barrier heights. The influence of proton versus neutron deformation differences on the potential energy landscape of fissioning nuclei is also discussed.

  8. Quaternary ammonium polyethylenimine nanoparticles for treating bacterial contaminated water.

    PubMed

    Farah, Shady; Aviv, Oren; Laout, Natalia; Ratner, Stanislav; Beyth, Nurit; Domb, Abraham J

    2015-04-01

    This study highlights the potential application of antimicrobial quaternary ammonium nanomaterials for water disinfection. Quaternary ammonium polyethylenimine (QA-PEI) nanoparticles (NPs) were synthesized by polyethylenimine crosslinking and alkylation with octyl iodide followed by methyl iodide quaternization. Particles modified with octyldodecyl alkyl chains were also prepared and evaluated. The antimicrobial activity of QA-PEI NPs was studied after anchoring in non-leaching polymeric coatings and also in aqueous suspension. Particles at different loadings (w/w) were embedded in polyethylene vinyl acetate and polyethylene methacrylic acid coatings and tested for antimicrobial activity against four representative strains of bacteria in static and dynamic modes. Coatings embedded with fluorescent labelled particles tracked by Axioscope fluorescence microscope during the antimicrobial test indicates no particles leaching out. Coatings loaded with 5% w/w QA-PEI exhibited strong antibacterial activity. Aqueous suspension was tested and found effective for bacterial decontamination at 0.1 ppm and maintains its activity for several weeks. PMID:25800358

  9. Community ecology in a changing environment: Perspectives from the Quaternary

    PubMed Central

    Jackson, Stephen T.; Blois, Jessica L.

    2015-01-01

    Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a “missing middle”: Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit. PMID:25901314

  10. Community ecology in a changing environment: Perspectives from the Quaternary.

    PubMed

    Jackson, Stephen T; Blois, Jessica L

    2015-04-21

    Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a "missing middle": Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit. PMID:25901314

  11. Synthesis and Antibacterial Activity of Novel Quaternary Ammonium Pyridoxine Derivatives.

    PubMed

    Shtyrlin, Nikita V; Sapozhnikov, Sergey V; Koshkin, Sergey A; Iksanova, Alfiya G; Sabirov, Arthur H; Kayumov, Airat R; Nureeva, Aliya A; Zeldi, Marina I; Shtyrlin, Yurii G

    2015-01-01

    A series of 26 quaternary ammonium pyridoxine derivatives were synthesized and their cytotoxicity and antibacterial activities against clinically relevant bacterial strains were tested in vitro. The antibacterial activity of mono-ammonium salts increased with the rise of the lipophilicity and compound 3,3,5-trimethyl-8,8-dioctyl-1,7,8,9-tetrahydro-[1,3]dioxino[5,4-d]pyrrolo[3,4-b]pyridin-8- ium chloride (2d) reaches a maximum among them. Bis-ammonium salt of pyridoxine 4 with two dimethyloctylamine groups also demonstrated high antibacterial activity despite lower lipophilicity. The results of MTT assay indicated that HEK 293 cells were more sensitive than HSF to quaternary ammonium pyridoxine derivatives. Compounds 2d and 4 did not induce the damage of the DNA and might be of interest in the development of new antimicrobials. PMID:25938426

  12. Enabling the Use of Space Fission Propulsion Systems

    SciTech Connect

    Mike Houts; Melissa Van Dyke; Tom Godfroy; James Martin; Kevin Pedersen; Ricky Dickens; Ivana Hrbud; Leo Bitteker; Bruce Patton; Suman Chakrabarti; Joe Bonometti

    2000-06-04

    This paper gives brief descriptions of advantages of fission technology for reaching any point in the solar system and of earlier efforts to develop space fission propulsion systems, and gives a more detailed description of the safe, affordable fission engine (SAFE) concept being pursued at the National Aeronautics and Space Administration's Marshall Space Flight Center.

  13. SPIDER Progress Towards High Resolution Correlated Fission Product Data

    NASA Astrophysics Data System (ADS)

    Shields, Dan; Meierbachtol, Krista; Tovesson, Fredrik; Arnold, Charles; Blackeley, Rick; Bredeweg, Todd; Devlin, Matt; Hecht, Adam; Jandel, Marian; Jorgenson, Justin; Nelson, Ron; White, Morgan; Spider Team

    2014-09-01

    The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) is under development with the goal of obtaining high-resolution, high-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (?), and total kinetic energy (TKE). A detailed description of the prototype SPIDER detector components will be presented. Characterization measurements with alpha and spontaneous fission sources will also be discussed. LA-UR-14-24875. The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) is under development with the goal of obtaining high-resolution, high-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (?), and total kinetic energy (TKE). A detailed description of the prototype SPIDER detector components will be presented. Characterization measurements with alpha and spontaneous fission sources will also be discussed. LA-UR-14-24875. This work is in part supported by LANL Laboratory Directed Research and Development Projects 20110037DR and 20120077DR.

  14. Convergence Improvement and Qualification of a Model for Fission

    E-print Network

    Boye, Johan

    Convergence Improvement and Qualification of a Model for Fission Gas Behaviour in Nuclear Fuel G and Qualification of a Model for Fission Gas Behaviour in Nuclear Fuel G A Ë L D U B U S Master's Thesis OF A MODEL FOR FISSION GAS BEHAVIOUR IN NUCLEAR FUEL Abstract : During the irradiation in a fuel assembly

  15. Fission of Entangled Spins: An Electronic Structure Perspective Xintian Feng,

    E-print Network

    Krylov, Anna I.

    Fission of Entangled Spins: An Electronic Structure Perspective Xintian Feng, Anatoliy V. Luzanov 61001, Ukraine *S Supporting Information ABSTRACT: Electronic structure aspects of singlet fission of singlet fission are explained. Based on the Cauchy-Schwarz inequality, we propose using the norm of one

  16. Fission barrier heights and lifetimes for heavy and superheavy nuclei

    E-print Network

    Pomorski, Krzysztof

    Fission barrier heights and lifetimes for heavy and superheavy nuclei J. Bartel*, A. Dobrowolski for Nuclear Research, Kiev, Ukraine Abstract. Ground-state masses, fission barrier heights and a lifetimes with the Yukawa folding procedure. Fission barrier height are nicely reproduced in our approach which contains

  17. Fission Yeast Tel1ATM and Rad3ATR

    E-print Network

    Nakamura, Toru M.

    Fission Yeast Tel1ATM and Rad3ATR Promote Telomere Protection and Telomerase Recruitment Bettina A organisms, including budding and fission yeasts, Arabidopsis, Drosophila, and mammals. However, such as fission yeast and humans. Here, we demonstrate by quantitative chromatin immunoprecipitation (ChIP) assays

  18. Protein-driven membrane stresses in fusion and fission

    E-print Network

    McMahon, Harvey

    Protein-driven membrane stresses in fusion and fission Michael M. Kozlov1 , Harvey T. McMahon2 fusion and fission become more evident if we disregard the accompanying biological processes and consider fusion or fission come from proteins andin most cases from membrane-bound proteins. In this review, we

  19. PASSAGE OF FISSION PRODUCTS THROUGH THE SKIN OF TUNA

    E-print Network

    PASSAGE OF FISSION PRODUCTS THROUGH THE SKIN OF TUNA SPECIAL SCIENTIFIC REPORT- FISHERIES No. 167 and Wildlife Service, John L. Farley, Director PASSAGE OF FISSION PRODUCTS THROUGH THE SKIN OF TUNA by Walter A was slow. PASSAGE OF FISSION PRODUCTS THROUGH THE SKIN OF TUNA In relation to "fallout" from nuclear -bomb

  20. Benchmarking nuclear fission theory G F Bertsch1

    E-print Network

    Bertsch George F.

    Note Benchmarking nuclear fission theory G F Bertsch1 , W Loveland2 , W Nazarewicz3,4 and P Talou5 a small set of fission observables to be used as test cases for validation of theoretical calculations. The purpose is to provide common data to facilitate the comparison of different fission theories and models

  1. Membrane Fission Is Promoted by Insertion of Amphipathic Helices and

    E-print Network

    McMahon, Harvey

    Membrane Fission Is Promoted by Insertion of Amphipathic Helices and Is Restricted by Crescent BAR membrane curva- ture. Here, we investigate membrane fission by shallow hydrophobic insertions- brane fission driven by hydrophobic insertions. A quantitative assay for vesiculation reveals an antag

  2. GENETICS | INVESTIGATION The Spontaneous Mutation Rate in the Fission Yeast

    E-print Network

    Lynch, Michael

    GENETICS | INVESTIGATION The Spontaneous Mutation Rate in the Fission Yeast Schizosaccharomyces of spontaneous mutations for the fission yeast Schizosaccharomyces pombe, a key model organism with many that the mechanisms of DNA maintenance may have diverged significantly between fission and budding yeasts

  3. Interleaved Preparation and Output in the COMIC Fission Module

    E-print Network

    Interleaved Preparation and Output in the COMIC Fission Module Mary Ellen Foster Institute, Edinburgh EH8 9LW United Kingdom M.E.Foster@ed.ac.uk Abstract We give a technical description of the fission the robust- ness of the fission module, and how it can be con- figured to support a variety of requirements

  4. Boolean Network Model Predicts Cell Cycle Sequence of Fission Yeast

    E-print Network

    Bornholdt, Stefan

    Boolean Network Model Predicts Cell Cycle Sequence of Fission Yeast Maria I. Davidich, Stefan network model of the cell-cycle regulatory network of fission yeast (Schizosaccharomyces Pombe sequence being a strongly attractive trajectory. Comparing the fission yeast cell-cycle model to a similar

  5. Analysis of Human Dopamine D3 Receptor Quaternary Structure.

    PubMed

    Marsango, Sara; Caltabiano, Gianluigi; Pou, Chantevy; Varela Liste, María José; Milligan, Graeme

    2015-06-12

    The dopamine D3 receptor is a class A, rhodopsin-like G protein-coupled receptor that can form dimers and/or higher order oligomers. However, the molecular basis for production of these complexes is not well defined. Using combinations of molecular modeling, site-directed mutagenesis, and homogenous time-resolved FRET, the interfaces that allow dopamine D3 receptor monomers to interact were defined and used to describe likely quaternary arrangements of the receptor. These were then compared with published crystal structures of dimeric ?1-adrenoreceptor, ?-opioid, and CXCR4 receptors. The data indicate important contributions of residues from within each of transmembrane domains I, II, IV, V, VI, and VII as well as the intracellular helix VIII in the formation of D3-D3 receptor interfaces within homo-oligomers and are consistent with the D3 receptor adopting a ?1-adrenoreceptor-like quaternary arrangement. Specifically, results suggest that D3 protomers can interact with each other via at least two distinct interfaces: the first one comprising residues from transmembrane domains I and II along with those from helix VIII and a second one involving transmembrane domains IV and V. Moreover, rather than existing only as distinct dimeric species, the results are consistent with the D3 receptor also assuming a quaternary structure in which two transmembrane domain I-II-helix VIII dimers interact to form a "rhombic" tetramer via an interface involving residues from transmembrane domains VI and VII. In addition, the results also provide insights into the potential contribution of molecules of cholesterol to the overall organization and potential stability of the D3 receptor and possibly other GPCR quaternary structures. PMID:25931118

  6. The impact of Quaternary Ice Ages on mammalian evolution.

    PubMed Central

    Lister, Adrian M

    2004-01-01

    The Quaternary was a time of extensive evolution among mammals. Most living species arose at this time, and many of them show adaptations to peculiarly Quaternary environments. The latter include continental northern steppe and tundra, and the formation of lakes and offshore islands. Although some species evolved fixed adaptations to specialist habitats, others developed flexible adaptations enabling them to inhabit broad niches and to survive major environmental changes. Adaptation to short-term (migratory and seasonal) habitat change probably played a part in pre-adapting mammal species to the longer-term cyclical changes of the Quaternary. Fossil evidence indicates that environmental changes of the order of thousands of years have been sufficient to produce subspeciation, but speciation has typically required one hundred thousand to a few hundred thousand years, although there are both shorter and longer exceptions. The persistence of taxa in environments imposing strong selective regimes may have been important in forcing major adaptive change. Individual Milankovitch cycles are not necessarily implicated in this process, but nor did they generally inhibit evolutionary change among mammals: many evolutionary divergences built over multiple climatic cycles. Deduction of speciation timing requires input from fossils and modern phenotypic and breeding data, to complement and constrain mitochondrial DNA coalescence dates which appear commonly to overestimate taxic divergence dates and durations of speciation. Migrational and evolutionary responses to climate change are not mutually exclusive but, on the contrary, may be synergistic. Finally, preliminary analysis suggests that faunal turnover, including an important element of speciation, was elevated in the Quaternary compared with the Neogene, at least in some biomes. Macroevolutionary species selection or sorting has apparently resulted in a modern mammalian fauna enriched with fast-reproducing and/or adaptively generalist species. PMID:15101579

  7. Fission Product Sorptivity in Graphite

    SciTech Connect

    Tompson, Jr., Robert V.; Loyalka, Sudarshan; Ghosh, Tushar; Viswanath, Dabir; Walton, Kyle; Haffner, Robert

    2015-04-01

    Both adsorption and absorption (sorption) of fission product (FP) gases on/into graphite are issues of interest in very high temperature reactors (VHTRs). In the original proposal, we proposed to use packed beds of graphite particles to measure sorption at a variety of temperatures and to use an electrodynamic balance (EDB) to measure sorption onto single graphite particles (a few ?m in diameter) at room temperature. The use of packed beds at elevated temperature is not an issue. However, the TPOC requested revision of this initial proposal to included single particle measurements at elevated temperatures up to 1100 °C. To accommodate the desire of NEUP to extend the single particle EDB measurements to elevated temperatures it was necessary to significantly revise the plan and the budget. These revisions were approved. In the EDB method, we levitate a single graphite particle (the size, surface characteristics, morphology, purity, and composition of the particle can be varied) or agglomerate in the balance and measure the sorption of species by observing the changes in mass. This process involves the use of an electron stepping technique to measure the total charge on a particle which, in conjunction with the measured suspension voltages for the particle, allows for determinations of mass and, hence, of mass changes which then correspond to measurements of sorption. Accommodating elevated temperatures with this type of system required a significant system redesign and required additional time that ultimately was not available. These constraints also meant that the grant had to focus on fewer species as a result. Overall, the extension of the original proposed single particle work to elevated temperatures added greatly to the complexity of the proposed project and added greatly to the time that would eventually be required as well. This means that the bulk of the experimental progress was made using the packed bed sorption systems. Only being able to recruit one graduate student meant that data acquisition with the packed bed systems ended up competing for the graduate student’s available time with the electrodynamic balance redesign and assembly portions of the project. This competition for available time was eventually mitigated to some extent by the later recruitment of an undergraduate student to help with data collection using the packed bed system. It was only the recruitment of the second student that allowed the single particle balance design and construction efforts to proceed as far as they did during the project period. It should be added that some significant time was also spent by the graduate student cataloging previous work involving graphite. This eventually resulted in a review paper being submitted and accepted (“Adsorption of Iodine on Graphite in High Temperature Gas-Cooled Reactor Systems: A Review,” Kyle L. Walton, Tushar K. Ghosh, Dabir S. Viswanath, Sudarshan K. Loyalka, Robert V. Tompson). Our specific revised objectives in this project were as follows: Experimentally obtain isotherms of Iodine for reactor grade IG-110 samples of graphite particles over a range of temperatures and pressures using an EDB and a temperature controlled EDB; Experimentally obtain isotherms of Iodine for reactor grade IG-110 samples of graphite particles over a range of temperatures and pressures using a packed column bed apparatus; Explore the effect that charge has on the adsorption isotherms of iodine by varying the charges on and the voltages used to suspend the microscopic particles in the EDB; and To interpret these results in terms of the existing models (Langmuir, BET, Freundlich, and others) which we will modify as necessary to include charge related effects.

  8. Quaternary diversification in a sexual Holarctic zooplankter, Daphnia galeata.

    PubMed

    Ishida, Seiji; Taylor, Derek J

    2007-02-01

    The effects of Quaternary glacial range partitioning on the diversification of Holarctic biota remain unclear. Glacial refugial lineages may form vicariant species, hybrid products, or merge after secondary contact. Here, we assess the effects of Quaternary glaciation on a Holarctic sexual zooplankter, Daphnia galeata, with apparently marked dispersal capacity and a widespread hybrid lineage in the New World. We collected samples of this species from 148 Holarctic lakes, analysed the nuclear and mitochondrial gene sequences, and tested predictions for hypotheses that account for the origin and spread of the New World D. galeata. We detected five nuclear phylogroups and four mitochondrial phylogroups, most of which were restricted to either the New World or the Old World. The oldest mitochondrial phylogroup was restricted to Japan. One major mitochondrial clade was distributed throughout the Holarctic, but only four haplotypes were shared among continents, and analysis of molecular variance indicated significant structure at the continental level. Haplotype sharing among continents could largely be attributed to anthropogenic introductions. Mismatch distributions, haplotype networks, phylogenetic trees, longitudinal haplotype diversity erosion and coalescence analyses are consistent with colonization from an Old World and a New World refugium. Our nuclear and mitochondrial DNA sequence evidence supports the hypothesis that the New World D. galeata underwent introgression with Daphnia dentifera, with dispersal being enhanced by glaciation. We conclude that Quaternary glaciation had a pronounced effect on the diversification of a Holarctic sexual zooplankter. PMID:17257114

  9. Multiple sources of alkanes in Quaternary oceanic sediment of Antarctica

    USGS Publications Warehouse

    Kvenvolden, K.A.; Rapp, J.B.; Golan-Bac, M.; Hostettler, F.D.

    1987-01-01

    Normal alkanes (n-C13n-C36), isoprenoid hydrocarbons (i-C15, i-C16, i-C18, i-C19, and i-C20) triterpanes (C27C32), and (C27C29) are present in low concentrations offshore Antarctica in near-surface, Quaternary sediment of the Wilkes Land continental margin and of the western Ross Sea. The distributions of these hydrocarbons are interpreted relative to possible sources and processes. The hydrocarbons appear to be mixtures of primary and recycled material from marine and terrigenous sources. The n-alkanes are most abundant and are characterized by two distinct populations, one of probable marine origin and the other likely from terrigenous, vascular plant sources. Because the continent of Antarctica today is devoid of higher plants, the plant-derived hydrocarbons in these offshore sediments probably came from wind-blown material and recycled Antarctic sediment that contains land-plant remains from an earlier period of time. Isoprenoid hydrocarbons are partially recycled and mainly of marine origin; the dominance of pristane over phytane suggests oxic paleoenvironmental conditions. Both modern and ancient triterpanes and steranes are present, and the distribution of these indicates a mixture of primary and recycled bacterial, algal, and possible higher-plant materials. Although the sampled sediments were deposited during the Quaternary, they apparently contain a significant component of hydrocarbons of pre-Quaternary age. ?? 1987.

  10. Uncertainties and Covariances of the Fission Cross Sections and the Fission Neutron Multiplicities for Actinides

    SciTech Connect

    Gai, E.V.; Ignatyuk, A.V.

    2008-12-15

    Experimental data on the fission cross sections and the fission-neutron multiplicities of actinides are analyzed on the basis of the unrecognized error-estimation method. Such an approach allows us to estimate reasonable systematic uncertainties of available data, which are underestimated by authors of most measurements as a rule. The corresponding uncertainties and covariances of evaluated data are obtained for the most important actinides in the 15-energy group representation. Differences between the present evaluations and the recent BOLNA results are discussed for the main actinides. It is shown that the fission cross section uncertainties are overestimated essentially in the BOLNA analysis for minor actinides. Uncertainties of the cross sections and the neutron multiplicities averaged over the Cf-252 fission-neutron spectrum are considered.

  11. Fission barriers and probabilities of spontaneous fission for elements with Z$\\geq$100

    E-print Network

    A. Baran; M. Kowal; P. -G. Reinhard; L. M. Robledo; A. Staszczak; M. Warda

    2015-03-05

    This is a short review of methods and results of calculations of fission barriers and fission half-lives of even-even superheavy nuclei. An approvable agreement of the following approaches is shown and discussed: The macroscopic-microscopic approach based on the stratagem of the shell correction to the liquid drop model and a vantage point of microscopic energy density functionals of Skyrme and Gogny type selfconsistently calculated within Hartree-Fock-Bogoliubov method. Mass parameters are calculated in the Hartree-Fock-Bogoliubov cranking approximation. A short part of the paper is devoted to the nuclear fission dynamics. We also discuss the predictive power of Skyrme functionals applied to key properties of the fission path of $^{266}$Hs. It applies the standard techniques of error estimates in the framework of a $\\chi^2$ analysis.

  12. Density Functional Theory Approach to Nuclear Fission

    E-print Network

    N. Schunck

    2013-01-20

    The Skyrme nuclear energy density functional theory (DFT) is used to model neutron-induced fission in actinides. This paper focuses on the numerical implementation of the theory. In particular, it reports recent advances in DFT code development on leadership class computers, and presents a detailed analysis of the numerical accuracy of DFT solvers for near-scission calculations.

  13. Cutting fluid for machining fissionable materials

    SciTech Connect

    Duerksen, W.K.; Googin, J.M.; Napier, B. Jr.

    1982-01-28

    The present invention is directed to a cutting fluid for machining fissionable material. The cutting fluid is formed of glycol, water and a boron compound in an adequate concentration for effective neutron attenuation so as to inhibit criticality incidents during machining.

  14. Critical Temperature from the Fission Data

    SciTech Connect

    Cherepanov, E. A.; Karnaukhov, V. A.

    2007-05-22

    Experimental and calculated data on the fission probability are compared for highly excited 188Os. The calculations have been made within the statistical model using the more reliable parameterizations for the temperature dependence or surface tension. It is concluded that the critical temperature for the nuclear liquid-gas phase transition is higher than 16 MeV.

  15. Propagation of a constant velocity fission wave

    NASA Astrophysics Data System (ADS)

    Deinert, Mark

    2011-10-01

    The ideal nuclear fuel cycle would require no enrichment, minimize the need fresh uranium, and produce few, if any, transuranic elements. Importantly, the latter goal would be met without the reprocessing. For purely physical reasons, no reactor system or fuel cycle can meet all of these objectives. However, a traveling-wave reactor, if feasible, could come remarkably close. The concept is simple: a large cylinder of natural (or depleted) uranium is subjected to a fast neutron source at one end, the neutrons would transmute the uranium downstream and produce plutonium. If the conditions were right, a self-sustaining fission wave would form, producing yet more neutrons which would breed more plutonium and leave behind little more than short-lived fission products. Numerical studies have shown that fission waves of this type are also possible. We have derived an exact solution for the propagation velocity of a fission wave through fertile material. The results show that these waves fall into a class of traveling wave phenomena that have been encountered in other systems. The solution places a strict conditions on the shapes of the flux, diffusive, and reactive profiles that would be required for such a phenomenon to persist. The results are confirmed numerically.

  16. Liquid uranium alloy-helium fission reactor

    DOEpatents

    Minkov, V.

    1984-06-13

    This invention describes a nuclear fission reactor which has a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200 to 1800/sup 0/C range, and even higher to 2500/sup 0/C.

  17. Liquid uranium alloy-helium fission reactor

    DOEpatents

    Minkov, Vladimir (Skokie, IL)

    1986-01-01

    This invention teaches a nuclear fission reactor having a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200.degree.-1800.degree. C. range, and even higher to 2500.degree. C., limited only by the thermal effectiveness of the structural materials, increasing the efficiency of power generation from the normal 30-35% with 300.degree.-500.degree. C. upper limit temperature to 50-65%. Irradiation of the circulating liquid fuel, as contrasted to only localized irradiation of a solid fuel, provides improved fuel utilization.

  18. After Apollo: Fission Origin of the Moon

    ERIC Educational Resources Information Center

    O'Keefe, John A.

    1973-01-01

    Presents current ideas about the fission process of the Moon, including loss of mass. Saturnian rings, center of the Moon, binary stars, and uniformitarianism. Indicates that planetary formation may be best explained as a destructive, rather than a constructive process. (CC)

  19. Fission Energy and Other Sources of Energy

    ERIC Educational Resources Information Center

    Alfven, Hannes

    1974-01-01

    Discusses different forms of energy sources and basic reasons for the opposition to the use of atomic energy. Suggests that research efforts should also be aimed toward the fission technology to make it acceptable besides major research studies conducted in the development of alternative energy sources. (CC)

  20. Energy distributions of fission fragments of preactinides and the hypothesisof independent fission modes

    SciTech Connect

    Itkis, M.G.; Okolovich, V.; Rusanov, A.Y.; Smirenkin, G.N.

    1985-05-01

    Experimental information is studied concerning the mass-energy distributions of fission fragments from preactinide nuclei from /sup 210/Tl to /sup 213/At. The dependence of the first and second moments of the fragment kinetic-energy distributions E/sub k/(M) and sigma/sup 2//sub E//sub k/(M) upon the excitation energy and nucleon content of the nuclei is analyzed. The two-fission-mode hypothesis is justified and its applicability range is found.

  1. SOFIA, a Next-Generation Facility for Fission Yields Measurements and Fission Study. First Results and Perspectives

    NASA Astrophysics Data System (ADS)

    Audouin, L.; Pellereau, E.; Taieb, J.; Boutoux, G.; Béliera, G.; Chatillon, A.; Ebran, A.; Gorbinet, T.; Laurent, B.; Martin, J.-F.; Tassan-Got, L.; Jurado, B.; Alvarez-Pol, H.; Ayyad, Y.; Benlliure, J.; Caamano, M.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Paradela, C.; Rodriguez-Sanchez, J.-L.; Vargas, J.; Casarejos, E.; Heinz, A.; Kelic-Heil, A.; Kurz, N.; Nociforo, C.; Pietri, S.; Prochazka, A.; Rossi, D.; Schmidt, K.-H.; Simon, H.; Voss, B.; Weick, H.; Winfield, J. S.

    2015-10-01

    Fission fragments play an important role in nuclear reactors evolution and safety. However, fragments yields are poorly known : data are essentially limited to mass yields from thermal neutron-induced fissions on a very few nuclei. SOFIA (Study On FIssion with Aladin) is an innovative experimental program on nuclear fission carried out at the GSI facility, which aims at providing isotopic yields on a broad range of fissioning systems. Relativistic secondary beams of actinides and pre-actinides are selected by the Fragment Separator (FRS) and their fission is triggered by electromagnetic interaction. The resulting excitation energy is comparable to the result of an interaction with a low-energy neutron, thus leading to useful data for reactor simulations. For the first time ever, both fission fragments are completely identified in charge and mass in a new recoil spectrometer, allowing for precise yields measurements. The yield of prompt neutrons can then be deduced, and the fission mechanism can be ascribed, providing new constraints for fission models. During the first experiment, all the technical challenges were matched : we have thus set new experimental standards in the measurements of relativistic heavy ions (time of flight, position, energy loss).This communication presents a first series of results obtained on the fission of 238U; many other fissioning systems have also been measured and are being analyzed presently. A second SOFIA experiment is planned in September 2014, and will be focused on the measurement of the fission of 236U, the analog of 235U+n.

  2. Database and Map of Quaternary Faults and Folds in Peru and its Offshore Region

    USGS Publications Warehouse

    Machare, Jose; Fenton, Clark H.; Machette, Michael N.; Lavenu, Alain; Costa, Carlos; Dart, Richard L.

    2003-01-01

    This publication consists of a main map of Quaternary faults and fiolds of Peru, a table of Quaternary fault data, a region inset map showing relative plate motion, and a second inset map of an enlarged area of interest in southern Peru. These maps and data compilation show evidence for activity of Quaternary faults and folds in Peru and its offshore regions of the Pacific Ocean. The maps show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds. These data are accompanied by text databases that describe these features and document current information on their activity in the Quaternary.

  3. SEDIMENTOLOGY AND GEOMORPHOLOGY OF QUATERNARY ALLUVIAL FANS WITH IMPLICATIONS TO GROWTH STRATA, LOST RIVER RANGE,

    E-print Network

    Dyer, Bill

    SEDIMENTOLOGY AND GEOMORPHOLOGY OF QUATERNARY ALLUVIAL FANS WITH IMPLICATIONS TO GROWTH STRATA......................................................................................14 5. UPPER CEDAR CREEK ALLUVIAL FAN.............................................. 19 Surface 6. JONES CREEK ALLUVIAL FAN......................................................... 67 Surface

  4. Fission Reaction Event Yield Algorithm, FREYA - For event-by-event simulation of fission

    NASA Astrophysics Data System (ADS)

    Verbeke, J. M.; Randrup, J.; Vogt, R.

    2015-06-01

    From nuclear materials accountability to detection of special nuclear material, SNM, the need for better modeling of fission has grown over the past decades. Current radiation transport codes compute average quantities with great accuracy and performance, but performance and averaging come at the price of limited interaction-by-interaction modeling. For fission applications, these codes often lack the capability of modeling interactions exactly: energy is not conserved, energies of emitted particles are uncorrelated, prompt fission neutron and photon multiplicities are uncorrelated. Many modern applications require more exclusive quantities than averages, such as the fluctuations in certain observables (e.g. the neutron multiplicity) and correlations between neutrons and photons. The new computational model, FREYA (Fission Reaction Event Yield Algorithm), aims to meet this need by modeling complete fission events. Thus it automatically includes fluctuations as well as correlations resulting from conservation of energy and momentum. FREYA has been integrated into the LLNL Fission Library, and will soon be part of MCNPX2.7.0, MCNP6, TRIPOLI-4.9, and Geant4.10.

  5. Prompt fission neutron spectra in fast-neutron-induced fission of 238U

    NASA Astrophysics Data System (ADS)

    Desai, V. V.; Nayak, B. K.; Saxena, A.; Suryanarayana, S. V.; Capote, R.

    2015-07-01

    Prompt fission neutron spectrum (PFNS) measurements for the neutron-induced fission of 238U are carried out at incident neutron energies of 2.0, 2.5, and 3.0 MeV, respectively. The time-of-flight technique is employed to determine the energy of fission neutrons. The prompt fission neutron energy spectra so obtained are analyzed using Watt parametrization to derive the neutron multiplicity and average prompt fission neutron energy. The present experimental PFNS data are compared with the evaluated spectra taken from the ENDF/B-VII.1 library and the predictive calculations carried out using the empire-3.2 (Malta) code with built-in Los Alamos (LA) and Kornilov PFNS models. The sensitivity of the empire-3.2 LA model-calculated PFNS to the nuclear level density parameter of the average fission fragment and to the total kinetic energy is investigated. empire-3.2 LA model PFNS calculations that use Madland 2006-recommended values [D. G. Madland, Nucl. Phys. A 772, 113 (2006), 10.1016/j.nuclphysa.2006.03.013] of the total kinetic energy and the level density parameter a =A /(10 ±0.5 ) compare very well to measured data at all incident neutron incident energies.

  6. The Quaternary adakite distribution of Kyushu Island, Ryukyu Arc, Japan

    NASA Astrophysics Data System (ADS)

    Shibata, T.; Yoshikawa, M.; Takemura, K.

    2011-12-01

    The Quaternary volcanoes are widely distributed in Kyusu Island, Japan. Philippine Sea plate is subducting beneath Kyushu. Clear distribution of deep seismic foci is observed below the Quaternary volcanoes in southern area, but not in northern area. Notsu et al. (1990, JVGR) examined the contribution of subduction to the magma source, and emphasized that no slab derived material is observed in northern area from Sr isotopic compositions. Volcanic activity similar to the within-plate type volcanism has been also emphasized for the magma genesis of this area (e.g. Kita et al, 2001, JVGR). However, we found adakitic rocks, which show high Sr/Y ratios and low Y concentrations (e.g. Defant and Drummond, 1990, Nature) from some Quaternary volcanoes in north Kyushu on the basis of published data (Otha et al, 1990, GANKO; Itoh, 1990, GANKO). Therefore, the magma genesis is still controversial. We studied lateral variations of Sr, Nd and Pb isotopic and trace element compositions for Quaternary volcanics from Kyushu to investigate the magma genesis. From the results, a clear variation of Sr/Y ratio, decreasing from north to south, is observed along the volcanic front. Some of the Sr/Y ratio of the most northern part of Kyusu shows the value >100. The all analyzed Pb isotope compositions show a single liner trend in 208Pb/204Pb v.s. 206Pb/204Pb diagram. The liner trend of Pb isotope ratios can be explained by the binary mixing of the Shikoku Basin basalt and tereginious sediment which might be a constituent of the subducting slab. The similar binary mixing relationships are found in Sr and Nd isotopic systematics. The isotopic characteristics of the Quaternary magma in Kyushu can be explained by the magma generation process of island arc, in spite of the lack of deep seismic foci in northern area. It is considered that high and low Sr/Y ratios suggest the contributions of partial melt in the north and aqueous fluid derived from subducting slab in the south, respectively. If these suggestions are correct, the difference of magma genesis in north and south might be related with the ages of subducting Philippine Sea plate which are < 25Ma at northern and >50 Ma at southern area.

  7. Predicting the Fission Yeast Protein Interaction Network

    PubMed Central

    Pancaldi, Vera; Saraç, Ömer S.; Rallis, Charalampos; McLean, Janel R.; P?evorovský, Martin; Gould, Kathleen; Beyer, Andreas; Bähler, Jürg

    2012-01-01

    A systems-level understanding of biological processes and information flow requires the mapping of cellular component interactions, among which protein–protein interactions are particularly important. Fission yeast (Schizosaccharomyces pombe) is a valuable model organism for which no systematic protein-interaction data are available. We exploited gene and protein properties, global genome regulation datasets, and conservation of interactions between budding and fission yeast to predict fission yeast protein interactions in silico. We have extensively tested our method in three ways: first, by predicting with 70–80% accuracy a selected high-confidence test set; second, by recapitulating interactions between members of the well-characterized SAGA co-activator complex; and third, by verifying predicted interactions of the Cbf11 transcription factor using mass spectrometry of TAP-purified protein complexes. Given the importance of the pathway in cell physiology and human disease, we explore the predicted sub-networks centered on the Tor1/2 kinases. Moreover, we predict the histidine kinases Mak1/2/3 to be vital hubs in the fission yeast stress response network, and we suggest interactors of argonaute 1, the principal component of the siRNA-mediated gene silencing pathway, lost in budding yeast but preserved in S. pombe. Of the new high-quality interactions that were discovered after we started this work, 73% were found in our predictions. Even though any predicted interactome is imperfect, the protein network presented here can provide a valuable basis to explore biological processes and to guide wet-lab experiments in fission yeast and beyond. Our predicted protein interactions are freely available through PInt, an online resource on our website (www.bahlerlab.info/PInt). PMID:22540037

  8. Fission track dating of kimberlitic zircons

    USGS Publications Warehouse

    Haggerty, S.E.; Raber, E.; Naeser, C.W.

    1983-01-01

    The only reliable method for dating kimberlites at present is the lengthy and specialized hydrothermal procedure that extracts 206Pb and 238U from low-uranium zircons. This paper describes a second successful method by fission track dating of large single-crystal zircons, 1.0-1.5 cm in dimension. The use of large crystals overcomes the limitations imposed in conventional fission track analysis which utilizes crushed fragments. Low track densities, optical track dispersion, and the random orientation of polished surfaces in the etch and irradiation cycle are effectively overcome. Fission track ages of zircons from five African kimberlites are reported, from the Kimberley Pool (90.3 ?? 6.5 m.y.), Orapa (87.4 ?? 5.7 and 92.4 ?? 6.1 m.y.), Nzega (51.1 ?? 3.8 m.y.), Koffiefontein (90.0 ?? 8.2 m.y.), and Val do Queve (133.4 ?? 11.5 m.y.). In addition we report the first radiometric ages (707.9 ?? 59.6 and 705.5 ?? 61.0 m.y.) of crustal zircons from kimberlites in northwest Liberia. The fission track ages agree well with earlier age estimates. Most of the zircons examined in this study are zoned with respect to uranium but linear correlations are established (by regression analysis) between zones of variable uranium content, and within zones of constant uranium content (by analysis of variance). Concordance between the fission track method and the U/Pb technique is established and we concluded that track fading from thermal annealing has not taken place. Kimberlitic zircons dated in this study, therefore, record the time of eruption. ?? 1983.

  9. Fission Technology for Exploring and Utilizing the Solar System

    NASA Technical Reports Server (NTRS)

    Houts, Mike; VanDyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Salvail, Pat; Hrbub, Ivana; Schmidt, George R. (Technical Monitor)

    2000-01-01

    Fission technology can enable rapid, affordable access to any point in the solar system. Potential fission-based transportation options include bimodal nuclear thermal rockets, high specific energy propulsion systems, and pulsed fission propulsion systems. In-space propellant re-supply enhances the effective performance of all systems, but requires significant infrastructure development. Safe, timely, affordable utilization of first-generation space fission propulsion systems will enable the development of more advanced systems. First generation space systems will build on over 45 years of US and international space fission system technology development to minimize cost,

  10. Fission Yield Measurements by Inductively Coupled Plasma Mass-Spectrometry

    SciTech Connect

    Irina Glagolenko; Bruce Hilton; Jeffrey Giglio; Daniel Cummings; Karl Grimm; Richard McKnight

    2009-11-01

    Correct prediction of the fission products inventory in irradiated nuclear fuels is essential for accurate estimation of fuel burnup, establishing proper requirements for spent fuel transportation and storage, materials accountability and nuclear forensics. Such prediction is impossible without accurate knowledge of neutron induced fission yields. Unfortunately, the accuracy of the fission yields reported in the ENDF/B-VII.0 library is not uniform across all of the data and much of the improvement is desired for certain isotopes and fission products. We discuss our measurements of cumulative fission yields in nuclear fuels irradiated in thermal and fast reactor spectra using Inductively Coupled Plasma Mass Spectrometry.

  11. Constraining the age and magnitude of uplift in the northern National Petroleum Reserve in Alaska (NPRA)-apatite fission-track analysis of samples from three wells

    USGS Publications Warehouse

    Houseknecht, David W.; Bird, Kenneth J.; O'Sullivan, Paul

    2011-01-01

    A broad, post-mid-Cretaceous uplift is defined in the northern National Petroleum Reserve in Alaska (NPRA) by regional truncation of Cretaceous strata, thermal maturity patterns, and amounts of exhumation estimated from sonic logs. Apatite fission-track (AFT) analysis of samples from three wells (South Meade No. 1, Topagoruk No. 1, and Ikpikpuk No. 1) across the eastern flank of the uplift indicates Tertiary cooling followed by Quaternary heating. Results from all three wells indicate that cooling, presumably caused by uplift and erosion, started about 75-65 Ma (latest Cretaceous-earliest Tertiary) and continued through the Tertiary Period. Data from South Meade indicate more rapid cooling after about 35-15 Ma (latest Eocene-middle Miocene) followed by a significant increase in subsurface temperature during the Quaternary, probably the result of increased heat flow. Data from Topagoruk and Ikpikpuk include subtle evidence of accelerated cooling starting in the latest Eocene-middle Miocene and possible evidence of increased temperature during the Quaternary. Subsurface temperature perturbations related to the insulating effect of permafrost may have been responsible for the Quaternary temperature increase at Topagoruk and Ikpikpuk and may have been a contributing factor at South Meade. Multiple lines of geologic evidence suggest that the magnitude of exhumation resulting from uplift and erosion is 5,000-6,500 ft at South Meade, 4,000-5,500 ft at Topagoruk, and 2,500-4,000 ft at Ikpikpuk. The results from these wells help to define the broad geometry of the uplift, which increases in magnitude from less than 1,000 ft at the Colville River delta to perhaps more than 7,000 ft along the northwestern coast of NPRA, between Point Barrow and Peard Bay. Neither the origin nor the offshore extent of the uplift, west and north of the NPRA coast, have been determined.

  12. Digital release of the Alaska Quaternary fault and fold database

    NASA Astrophysics Data System (ADS)

    Koehler, R. D.; Farrell, R.; Burns, P.; Combellick, R. A.; Weakland, J. R.

    2011-12-01

    The Alaska Division of Geological & Geophysical Surveys (DGGS) has designed a Quaternary fault and fold database for Alaska in conformance with standards defined by the U.S. Geological Survey for the National Quaternary fault and fold database. Alaska is the most seismically active region of the United States, however little information exists on the location, style of deformation, and slip rates of Quaternary faults. Thus, to provide an accurate, user-friendly, reference-based fault inventory to the public, we are producing a digital GIS shapefile of Quaternary fault traces and compiling summary information on each fault. Here, we present relevant information pertaining to the digital GIS shape file and online access and availability of the Alaska database. This database will be useful for engineering geologic studies, geologic, geodetic, and seismic research, and policy planning. The data will also contribute to the fault source database being constructed by the Global Earthquake Model (GEM), Faulted Earth project, which is developing tools to better assess earthquake risk. We derived the initial list of Quaternary active structures from The Neotectonic Map of Alaska (Plafker et al., 1994) and supplemented it with more recent data where available. Due to the limited level of knowledge on Quaternary faults in Alaska, pre-Quaternary fault traces from the Plafker map are shown as a layer in our digital database so users may view a more accurate distribution of mapped faults and to suggest the possibility that some older traces may be active yet un-studied. The database will be updated as new information is developed. We selected each fault by reviewing the literature and georegistered the faults from 1:250,000-scale paper maps contained in 1970's vintage and earlier bedrock maps. However, paper map scales range from 1:20,000 to 1:500,000. Fault parameters in our GIS fault attribute tables include fault name, age, slip rate, slip sense, dip direction, fault line type (i.e., well constrained, moderately constrained, or inferred), and mapped scale. Each fault is assigned a three-integer CODE, based upon age, slip rate, and how well the fault is located. This CODE dictates the line-type for the GIS files. To host the database, we are developing an interactive web-map application with ArcGIS for Server and the ArcGIS API for JavaScript from Environmental Systems Research Institute, Inc. (Esri). The web-map application will present the database through a visible scale range with each fault displayed at the resolution of the original map. Application functionality includes: search by name or location, identification of fault by manual selection, and choice of base map. Base map options include topographic, satellite imagery, and digital elevation maps available from ArcGIS on-line. We anticipate that the database will be publically accessible from a portal embedded on the DGGS website by the end of 2011.

  13. A transferable model for singlet-fission kinetics.

    PubMed

    Yost, Shane R; Lee, Jiye; Wilson, Mark W B; Wu, Tony; McMahon, David P; Parkhurst, Rebecca R; Thompson, Nicholas J; Congreve, Daniel N; Rao, Akshay; Johnson, Kerr; Sfeir, Matthew Y; Bawendi, Moungi G; Swager, Timothy M; Friend, Richard H; Baldo, Marc A; Van Voorhis, Troy

    2014-06-01

    Exciton fission is a process that occurs in certain organic materials whereby one singlet exciton splits into two independent triplets. In photovoltaic devices these two triplet excitons can each generate an electron, producing quantum yields per photon of >100% and potentially enabling single-junction power efficiencies above 40%. Here, we measure fission dynamics using ultrafast photoinduced absorption and present a first-principles expression that successfully reproduces the fission rate in materials with vastly different structures. Fission is non-adiabatic and Marcus-like in weakly interacting systems, becoming adiabatic and coupling-independent at larger interaction strengths. In neat films, we demonstrate fission yields near unity even when monomers are separated by >5 Å. For efficient solar cells, however, we show that fission must outcompete charge generation from the singlet exciton. This work lays the foundation for tailoring molecular properties like solubility and energy level alignment while maintaining the high fission yield required for photovoltaic applications. PMID:24848234

  14. Fifty years of nuclear fission: Nuclear data and measurements series

    SciTech Connect

    Lynn, J.E.

    1989-06-01

    This report is the written version of a colloquium first presented at Argonne National Laboratory in January 1989. The paper begins with an historical preamble about the events leading to the discovery of nuclear fission. This leads naturally to an account of early results and understanding of the fission phenomena. Some of the key concepts in the development of fission theory are then discussed. The main theme of this discussion is the topography of the fission barrier, in which the interplay of the liquid-drop model and nucleon shell effects lead to a wide range of fascinating phenomena encompassing metastable isomers, intermediate-structure effects in fission cross-sections, and large changes in fission product properties. It is shown how study of these changing effects and theoretical calculations of the potential energy of the deformed nucleus have led to broad qualitative understanding of the nature of the fission process. 54 refs., 35 figs.

  15. Multimodal Fission in Heavy-Ion Induced Reactions

    SciTech Connect

    Pokrovskiy, I. V.; Bogachev, A. A.; Iitkis, M. G.; Iitkis, J. M.; Kondratiev, N. A.; Kozulin, E. M.; Dorvaux, O.; Rowley, N.; Schmitt, Ch.; Stuttge, L.

    2006-08-14

    Mass, energy and folding angle distributions of the fission fragments as well as multiplicities of neutron and gamma-quanta emissions accompanying the fission process were measured for fission of 226Th, 227Pa and 234Pu compound nuclei produced in reactions with 18O and 26Mg projectiles over a wide energy range. Data were analyzed with respect to the presence of fission modes. Asymmetric fission was observed even at very high initial excitation for all the measured systems. The so-called fission mode S1 (caused by the proton shell Z{approx}50 and neutron shell N{approx}82 in heavy fragment) was found to be dominant in asymmetric fission of 234Pu. Reactions with not full linear momentum transfer were observed in the folding spectra for all the measured systems.

  16. Fission studies of secondary beams from relativistic uranium projectiles: The proton even-odd effect in fission fragment charge yields

    SciTech Connect

    Junghans, A. R.; Benlliure, J.; Schmidt, K.-H.; Voss, B.; Boeckstiegel, C.; Clerc, H.-G.; Grewe, A.; Heinz, A.; Jong, M. de; Mueller, J.; Steinhaeuser, S.; Pfuetzner, M.

    1999-09-02

    Nuclear-charge yields of fragments produced by fission of neutron-deficient isotopes of uranium, protactinium, actinium, and radium have been measured. These radioactive isotopes were produced as secondary beams, and electromagnetic fission was induced in a lead target with an average excitation energy around 11 MeV. The local even-odd effect in symmetric and in asymmetric fission of thorium isotopes is found to be independent of Z{sup 2}/A. The charge yields of the fission fragments of the odd-Z fissioning protactinium and actinium show a pronounced even-odd effect. In asymmetric fission the unpaired proton predominantly sticks to the heavy fragment. A statistical model based on the single-particle level density at the Fermi energy is able to reproduce the overall trend of the local even-odd effects both in even-Z and odd-Z fissioning systems.

  17. Fusion-fission energy systems evaluation

    SciTech Connect

    Teofilo, V.L.; Aase, D.T.; Bickford, W.E.

    1980-01-01

    This report serves as the basis for comparing the fusion-fission (hybrid) energy system concept with other advanced technology fissile fuel breeding concepts evaluated in the Nonproliferation Alternative Systems Assessment Program (NASAP). As such, much of the information and data provided herein is in a form that meets the NASAP data requirements. Since the hybrid concept has not been studied as extensively as many of the other fission concepts being examined in NASAP, the provided data and information are sparse relative to these more developed concepts. Nevertheless, this report is intended to provide a perspective on hybrids and to summarize the findings of the rather limited analyses made to date on this concept.

  18. Fusion, fragmentation, and fission of mitochondria.

    PubMed

    Polyakov, V Yu; Soukhomlinova, M Yu; Fais, D

    2003-08-01

    Individual mitochondria which form the chondriom of eucaryotic cells are highly dynamic systems capable of fusion and fragmentation. These two processes do not exclude one another and can occur concurrently. However, fragmentation and fusion of mitochondria regularly alternate in the cell cycle of some unicellular and multicellular organisms. Mitochondrial shapes are also described which are interpreted as intermediates of their "equational" division, or fission. Unlike the fragmentation, the division of mitochondria, especially synchronous division, is also accompanied by segregation of mitochondrial genomes and production of specific "dumbbell-shaped" intermediates. This review considers molecular components and possible mechanisms of fusion, fragmentation, and fission of mitochondria, and the biological significance of these processes is discussed. PMID:12948383

  19. Fission of a multiphase membrane tube

    E-print Network

    Jean-Marc Allain; Cornelis Storm; Aurelien Roux; Martine Ben Amar; Jean-Francois Joanny

    2004-09-01

    A common mechanism for intracellular transport is the use of controlled deformations of the membrane to create spherical or tubular buds. While the basic physical properties of homogeneous membranes are relatively well-known, the effects of inhomogeneities within membranes are very much an active field of study. Membrane domains enriched in certain lipids in particular are attracting much attention, and in this Letter we investigate the effect of such domains on the shape and fate of membrane tubes. Recent experiments have demonstrated that forced lipid phase separation can trigger tube fission, and we demonstrate how this can be understood purely from the difference in elastic constants between the domains. Moreover, the proposed model predicts timescales for fission that agree well with experimental findings.

  20. Fast-fission tokamak breeder reactors

    NASA Astrophysics Data System (ADS)

    Jassby, D. L.; Berwald, D. H.; Garner, J.; Whitley, R. H.; Maya, I.; Wong, C. P. C.; Lee, J. D.; Moir, R. W.

    1986-09-01

    A fast-fission blanket around a fusion plasma exploits high neutron multiplication for superior breeding and high-energy multiplication to generate significant net electrical power. A major improvement over previous fast-fission blanket concepts is the use of mobile fuel, namely a pebble-bed configuration with helium cooling. Upon loss of coolant, the mobile fuel can be gravity-dumped to a separately cooled dump tank before excessive temperatures are reached. The pebble bed is also compatible with rapid fuel exchange and a low-cost reprocessing method. With the ignited tokamak plasma producing 620 MW of fusion power, the net electric power is 1600 MWe and the annual fissile production exceeds 3 tonnes.

  1. Microscopic Calculations of 240Pu Fission

    SciTech Connect

    Younes, W; Gogny, D

    2007-09-11

    Hartree-Fock-Bogoliubov calculations have been performed with the Gogny finite-range effective interaction for {sup 240}Pu out to scission, using a new code developed at LLNL. A first set of calculations was performed with constrained quadrupole moment along the path of most probable fission, assuming axial symmetry but allowing for the spontaneous breaking of reflection symmetry of the nucleus. At a quadrupole moment of 345 b, the nucleus was found to spontaneously scission into two fragments. A second set of calculations, with all nuclear moments up to hexadecapole constrained, was performed to approach the scission configuration in a controlled manner. Calculated energies, moments, and representative plots of the total nuclear density are shown. The present calculations serve as a proof-of-principle, a blueprint, and starting-point solutions for a planned series of more comprehensive calculations to map out a large set of scission configurations, and the associated fission-fragment properties.

  2. Nuclear Fission Investigation with Twin Ionization Chamber

    NASA Astrophysics Data System (ADS)

    Zeynalova, O.; Zeynalov, Sh.; Nazarenko, M.; Hambsch, F.-J.; Oberstedt, S.

    2011-11-01

    The purpose of the present paper was to report the recent results, obtained in development of digital pulse processing mathematics for prompt fission neutron (PFN) investigation using twin ionization chamber (TIC) along with fast neutron time-of-flight detector (ND). Due to well known ambiguities in literature (see refs. [4, 6, 9 and 11]), concerning a pulse induction on TIC electrodes by FF ionization, we first presented detailed mathematical analysis of fission fragment (FF) signal formation on TIC anode. The analysis was done using Ramo-Shockley theorem, which gives relation between charged particle motion between TIC electrodes and so called weighting potential. Weighting potential was calculated by direct numerical solution of Laplace equation (neglecting space charge) for the TIC geometry and ionization, caused by FF. Formulae for grid inefficiency (GI) correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and discussed.

  3. SABR Fusion-Fission Hybrid Studies

    NASA Astrophysics Data System (ADS)

    Stewart, Chris

    2012-03-01

    The Subcritical Advanced Burner Reactor (SABR) concept is a fast reactor comprised of a tokamak fusion neutron source based on ITER surrounded by an annular fission core adapted from Integral Fast Reactor designs. Previous work has examined SABR used to help close the nuclear fuel cycle by fissioning the transuranics from spent nuclear fuel. One focus of the present work is a SABR Breeder Reactor to achieve tritium self-sufficieny and a Pu breeding ratio significantly above 1 in order to provide fuel for SABR as well as for MOX-fueled LWR's and other fast reactors. Another focus of this research is the dynamic safety simulation of lloss-of-flow loss-of-heat-sink, loss-of-power, and positive reactivity accidents in the TRU fuel SABR burner reactor. The reactivity effect of thermal-induced bowing of fuel pins has been modeled, which is expected to provide passive safety.

  4. Fission Surface Power Technology Development Status

    NASA Technical Reports Server (NTRS)

    Palac, Donald T.; Mason, Lee S.; Harlow, Scott

    2009-01-01

    With the potential future deployment of a lunar outpost there is expected to be a clear need for a high-power, lunar surface power source to support lunar surface operations independent of the day-night cycle, and Fission Surface Power (FSP) is a very effective solution for power levels above a couple 10 s of kWe. FSP is similarly enabling for the poorly illuminated surface of Mars. The power levels/requirements for a lunar outpost option are currently being studied, but it is known that cost is clearly a predominant concern to decision makers. This paper describes the plans of NASA and the DOE to execute an affordable fission surface power system technology development project to demonstrate sufficient technology readiness of an affordable FSP system so viable and cost-effective FSP system options will be available when high power lunar surface system choices are expected to be made in the early 2010s.

  5. System Concepts for Affordable Fission Surface Power

    NASA Technical Reports Server (NTRS)

    Mason, Lee; Poston, David; Qualls, Louis

    2008-01-01

    This paper presents an overview of an affordable Fission Surface Power (FSP) system that could be used for NASA applications on the Moon and Mars. The proposed FSP system uses a low temperature, uranium dioxide-fueled, liquid metal-cooled fission reactor coupled to free-piston Stirling converters. The concept was determined by a 12 month NASA/DOE study that examined design options and development strategies based on affordability and risk. The system is considered a low development risk based on the use of terrestrial-derived reactor technology, high efficiency power conversion, and conventional materials. The low-risk approach was selected over other options that could offer higher performance and/or lower mass.

  6. Final excitation energy of fission fragments

    E-print Network

    Karl-Heinz Schmidt; Beatriz Jurado

    2011-04-14

    We study how the excitation energy of the fully accelerated fission fragments is built up. It is stressed that only the intrinsic excitation energy available before scission can be exchanged between the fission fragments to achieve thermal equilibrium. This is in contradiction with most models used to calculate prompt neutron emission where it is assumed that the total excitation energy of the final fragments is shared between the fragments by the condition of equal temperatures. We also study the intrinsic excitation-energy partition according to a level density description with a transition from a constant-temperature regime to a Fermi-gas regime. Complete or partial excitation-energy sorting is found at energies well above the transition energy.

  7. Geology of the quaternary volcanic centres of the east Anatolia

    NASA Astrophysics Data System (ADS)

    Y?lmaz, Y.; Güner, Y.; ?aro?lu, F.

    1998-10-01

    Following the collision along the Bitlis-Zagros suture, a north-south convergence between the Arabian Platform and Laurasia has continued uninterrupted until the present. As a result, the continental crust has been shortened, thickened and consequently elevated to form the Turkish-Iranian high plateau. On the high plateau volcanic activity began during the Neogene, intensified during the late Miocene-Pliocene and continued until historical times. Large volcanic centres have been developed during the Quaternary which form significant peaks above the Turkish-Iranian high plateau. Among the Quaternary volcanoes, the major volcanic centres are Ararat, Tendürek, Suphan and Nemrut. Ararat (A?ri Da?i) is the largest volcanic center and is a compound stratovolcano, consisting of Greater Ararat and lesser Ararat. The former represents the highest elevation of Anatolia reaching over 5000 m in height. Tendürek is a double-peaked shield volcano, which produced a voluminous amount of basalt lava as extensive pahoehoe, and aa flows. It has an ill-defined semi-caldera. Suphan is an isolated stratovolcano, capped by silicic dome. It represents the second highest topographic elevation in Anatolia, with a height of over 4000 m. A cluster of subsidiary cones and small domes surrounds the volcano. Nemrut is the largest member of a group of volcanoes, which trend north-south. It is a stratovolcano, having a well-defined collapse caldera and a caldera lake. Various volcanic ejecta have been extruded from these volcanic centres over the last 1 to 2 million years. The Quaternary volcanic centres, although temporally and spatially closely associated, display a wide range of lavas from basalt to rhyolite. The volcanoes have diverse compositional trends; Ararat is distinctly subalkaline, Suphan is mildly subalkaline, Nemrut is mildly alkaline and Tendürek is strongly alkaline. The major and trace element compositions together with the isotope ratios indicate that their magmas were generated from a heterogeneous mantle source. Each of the volcanic centres has undergone a partly different magmatic evolution.

  8. An aminostratigraphy for the British Quaternary based on Bithynia opercula

    PubMed Central

    Penkman, Kirsty E.H.; Preece, Richard C.; Bridgland, David R.; Keen, David H.; Meijer, Tom; Parfitt, Simon A.; White, Tom S.; Collins, Matthew J.

    2013-01-01

    Aminostratigraphies of Quaternary non-marine deposits in Europe have been previously based on the racemization of a single amino acid in aragonitic shells from land and freshwater molluscs. The value of analysing multiple amino acids from the opercula of the freshwater gastropod Bithynia, which are composed of calcite, has been demonstrated. The protocol used for the isolation of intra-crystalline proteins from shells has been applied to these calcitic opercula, which have been shown to more closely approximate a closed system for indigenous protein residues. Original amino acids are even preserved in bithyniid opercula from the Eocene, showing persistence of indigenous organics for over 30 million years. Geochronological data from opercula are superior to those from shells in two respects: first, in showing less natural variability, and second, in the far better preservation of the intra-crystalline proteins, possibly resulting from the greater stability of calcite. These features allow greater temporal resolution and an extension of the dating range beyond the early Middle Pleistocene. Here we provide full details of the analyses for 480 samples from 100 horizons (75 sites), ranging from Late Pliocene to modern. These show that the dating technique is applicable to the entire Quaternary. Data are provided from all the stratotypes from British stages to have yielded opercula, which are shown to be clearly separable using this revised method. Further checks on the data are provided by reference to other type-sites for different stages (including some not formally defined). Additional tests are provided by sites with independent geochronology, or which can be associated with a terrace stratigraphy or biostratigraphy. This new aminostratigraphy for the non-marine Quaternary deposits of southern Britain provides a framework for understanding the regional geological and archaeological record. Comparison with reference to sites yielding independent geochronology, in combination with other lines of evidence, allows tentative correlation with the marine oxygen isotope record. PMID:23396683

  9. Quaternary geology and waste disposal in South Norfolk, England

    NASA Astrophysics Data System (ADS)

    Gray, J. M.

    South Norfolk is dominated by the till plain of the Anglian Glaciation in eastern England, and therefore there are very few disused gravel pits and quarries suitable for the landfilling of municipal waste. Consequently, in May 1991, Norfolk County Council applied for planning permission to develop an above ground or 'landraise' waste disposal site at a disused U.S. World War II Airfield at Hardwick in South Norfolk. The proposal involved excavating a pit 2-4 m deep into the Lowestoft Till and overfilling it to create a hill of waste up to 10 m above the existing till plain. In general, leachate containment was to be achieved by utilising the relatively low permeability till on the floor of the site, but with reworking of the till around the site perimeter because of sand lenses in the upper part of the till. This paper examines three aspects of the proposal and the wider issues relating to Quaternary geology and waste disposal planning in South Norfolk: (i) the suitability of the till as a natural leachate containment system; (ii) the appropriateness of the landraise landform; and (iii) alternative sites. A Public Inquiry into the proposals was held in January/February 1993 and notification of refusal of planning permission was published in August 1993. Among the grounds for refusal were an inadequate knowledge of the site's geology and hydrogeology and the availability of alternative sites. The paper concludes by stressing that a knowledge of Quaternary geology is crucial to both the planning and design of landfill sites in areas of glacial/Quaternary sediments.

  10. Delayed-fission properties of neutron-deficient americium nuclei

    SciTech Connect

    Hall, H.L. . Dept. of Chemistry)

    1989-10-23

    Characteristics of the delayed-fission decay mode in light americium nuclei have been investigated. Measurements on the unknown isotopes {sup 230}Am and {sup 236}Am were attempted, and upper limits on the delayed-fission branches of these nuclei were determined. Evidence of the existence of {sup 236}Am was observed in radiochemical separations. Total kinetic energy and mass-yield distributions of the electron-capture delayed-fission mode were measured for {sup 232}Am (t{sub 1/2} = 1.31 {plus minus} 0.04 min) and for {sup 234}Am (t{sub 1/2} = 2.32 {plus minus} 0.08 min), and delayed-fission probabilities of 6.9 {times} 10{sup {minus}4} and 6.6 {times} 10{sup {minus}5}, respectively, were determined. The total kinetic energy and the asymmetric mass-yield distributions are typical of fission of mid-range actinides. No discernible influence of the anomalous triple-peaked mass division characteristic of the thorium-radium region was detected. Measurements of the time correlation between the electron-capture x-rays and the subsequent fission conform that the observed fissions arise from the electron-capture delayed-fission mechanism. Delayed fission has provided a unique opportunity to extend the range of low-energy fission studies to previously inaccessible regions. 71 refs., 44 figs., 13 tabs.

  11. Neutron angular correlations in spontaneous and neutron-induced fission

    NASA Astrophysics Data System (ADS)

    Vogt, R.; Randrup, J.

    2014-12-01

    Background: Neutron emission is correlated in fission events because, on average, more than one neutron is emitted per fission. Measurements of these correlations, coupled with studies of more inclusive observables such as neutron multiplicity, provide sensitive information about the fission mechanism. Neutron-neutron angular correlations have been studied in both spontaneous fission of 252Cf and neutron-induced fission of 235U. These correlations, until recently incalculable in most available simulations of fission, can now be calculated in event-by-event simulations of fission. Purpose: Phenomenological studies of fission are of interest both for basic science and for practical applications. Neutron-neutron angular correlations are characteristic of the fissioning isotope and could be used in material identification. Method: We use our model of complete fission events, freya, to first study the sensitivity of two-neutron angular correlations to the model inputs and then compare to available data. We also compare our simulations to neutron-fragment angular correlations. Results: We find that the correlations calculated with freya are fairly robust with respect to the input parameters. Any strong deviations in the correlations result in poor agreement with measured inclusive neutron observables such as neutron multiplicity as a function of fragment mass and the neutron multiplicity distribution. The agreement of freya with the present set of correlation data is found to be good. Conclusions: freya can be used to reliably predict neutron-neutron angular correlations and could then be used to identify materials.

  12. Spontaneous fission half-lives and their systematics

    SciTech Connect

    Holden, N.E.

    1998-03-01

    Spontaneous fission is a phenomenon exhibited by heavy nuclei, which can be a major mode of decay of nuclei of elements heavier than thorium and can be a determining factor in their stability. For purposes of this paper, spontaneous fission will be considered a process in which a nucleus breaks up into two approximately equal parts. The emission of light nuclei or heavy ions such as {sup 12}C, {sup 16}O, or {sup 32}S will not be considered. This radioactive decay mode is often much smaller than the spontaneous fission decay mode, although this is not true in all cases. Barwick noted that this might indicate that the assumed half-life for spontaneous fission of some older experiments might be partially due to heavy fragment radioactivity. Other than taking note of this potential correction to spontaneous fission half-lives, this decay mode of heavy fragment radioactivity will be ignored. Excited states of some heavy nuclei may decay via spontaneous fission. These so-called fission isomers will not be discussed here. Electron capture (EC) or beta-delayed fission is a process in which prompt fission of a sufficiently excited daughter state occurs following population by EC or beta decay. The fission activity will appear to decay with the half-life of the parent and was earlier confused in some cases with SF. This process has been discussed in detail in a review and will not be considered in this paper.

  13. Recent Progress on the Stereoselective Synthesis of Cyclic Quaternary ?-Amino Acids

    PubMed Central

    Cativiela, Carlos; Ordóñez, Mario

    2010-01-01

    The most recent papers describing the stereoselective synthesis of cyclic quaternary ?-amino acids are collected in this review. The diverse synthetic approaches are classified according to the size of the ring and taking into account the bond that is formed to complete the quaternary skeleton. PMID:20300486

  14. Late Quaternary changes in biogenic opal uxes in the Southern Indian Ocean

    E-print Network

    Demouchy, Sylvie

    Late Quaternary changes in biogenic opal £uxes in the Southern Indian Ocean L. Dezileau a;Ã , J data. ß 2003 Elsevier B.V. All rights reserved. Keywords: Southern Ocean; Indian sector; biogenic opal 2003 Abstract Late Quaternary sedimentary and paleoenvironmental conditions in the southern Indian

  15. A review of Quaternary range shifts in European aquatic Coleopterageb_572 87..100

    E-print Network

    Murcia, Universidad de

    of the Quaternary fossil record of Euro- pean water beetles to evaluate their geographical and temporal coverage compiled Quaternary water beetle records from public databases and published references. We included of the species. Results Our final data set included over 9000 records for 259 water beetle species. Fossil

  16. Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region, California

    E-print Network

    Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region.K., and Gans, K.D., 2006, Maps of Quaternary deposits and liquefaction susceptibility in the central San and Liquefaction Interpretation Additional products of this research include postscript and PDF files

  17. Quaternary history of sea ice in the western Arctic Ocean based on foraminifera

    E-print Network

    Quaternary history of sea ice in the western Arctic Ocean based on foraminifera Leonid Polyak a 4 February 2013 Keywords: Western Arctic Ocean Foraminifers Quaternary Mid-Pleistocene Transition Sea ice history a b s t r a c t Sediment cores from the Northwind Ridge, western Arctic Ocean

  18. Identification of Quaternary Shape Memory Alloys with Near-Zero Thermal Hysteresis and Unprecedented

    E-print Network

    Rubloff, Gary W.

    Identification of Quaternary Shape Memory Alloys with Near-Zero Thermal Hysteresis of quaternary Ti­Ni­Cu­Pd SMAs and the thermal hysteresis are tailored. Novel alloys with near-zero thermal hysteresis, as predicted by the geometric non- linear theory of martensite, are identified. The thin

  19. Charophytes as lacustrine biomarkers during the quaternary in North Africa

    NASA Astrophysics Data System (ADS)

    Soulié-Märsche, I.

    The use of charophytes as biomarkers is discussed with emphasis on the differences in study methods for cosmopolitan and ecotype species. A first extensive inventory of Quaternary deposits of charophytes in Africa north of the equator comprising 18 sites from Senegal to the Sudan is drawn up with data on spatial and temporal distribution. The existence of relatively deep cold lakes in the Holocene is shown by the frequent presence of specimens of cold flora no longer present in Africa today. All the original data show the complementary nature of the study of fossil Charophyta for the multidisciplinary reconstitution of palaeoenvironments.

  20. Fission Barriers of Compound Superheavy Nuclei

    NASA Astrophysics Data System (ADS)

    Nazarewicz, Witold

    2010-02-01

    The dependence of fission barriers on the excitation energy of the compound nucleus impacts the survival probability of superheavy nuclei synthesized in heavy-ion fusion reactions. In this work [1,2], we investigate the isentropic fission barriers by means of the self-consistent nuclear density functional theory. The relationship between isothermal and isentropic descriptions is demonstrated. Calculations have been carried out for ^264Fm, ^272Ds, ^278Cp, ^292114, and ^312124. For nuclei around ^278Cp produced in ``cold fusion" reactions, we predict a more rapid decrease of fission barriers with excitation energy as compared to the nuclei around ^292114 synthesized in ``hot fusion'' experiments. This is explained in terms of the difference between the ground-state and saddle-point temperatures. [4pt] [1] J.C. Pei, W. Nazarewicz, J.A. Sheikh and A.K. Kerman, Phys. Rev. Lett. 102, 192501 (2009).[0pt] [2] J.A. Sheikh, W. Nazarewicz, and J.C. Pei, Phys. Rev. C 80, 011302(R) (2009). )

  1. Undergraduate Measurements For Fission Reactor Applications

    NASA Astrophysics Data System (ADS)

    Hicks, S. F.; Kersting, L. J.; Lueck, C. J.; McDonough, P.; Crider, B. P.; McEllistrem, M. T.; Peters, E. E.; Vanhoy, J. R.

    2011-06-01

    Undergraduate students at the University of Dallas (UD) have investigated elastic and inelastic neutron scattering cross sections on structural materials important for criticality considerations in nuclear fission processes. Neutrons scattered off of 23Na and NatFe were detected using neutron time-of-flight techniques at the University of Kentucky Low-Energy Nuclear Accelerator Facility. These measurements are part of an effort to increase the efficiency of power generation from existing fission reactors in the US and in the design of new fission systems. Students have learned the basics of how to operate the Model CN Van de Graaff generator at the laboratory, setup detectors and electronics, use data acquisition systems, and they are currently analyzing the angular dependence of the scattered neutrons for incident neutron energies of 3.57 and 3.80 MeV. Most students participating in the project will use the research experience as the material for their undergraduate research thesis required for all Bachelor of Science students at the University of Dallas. The first student projects on this topic were completed during the summer of 2010; an overview of student participation in this investigation and their preliminary results will be presented.

  2. Calculated fission properties of the heaviest elements

    SciTech Connect

    Moeller, P.; Nix, J.R.; Swiatecki, W.J.

    1986-09-01

    A quantitative calculation is presented that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. For the macroscopic part a Yukawa-plus-exponential model is used and for the microscopic part a folded-Yukawa single-particle potential is used. The three-quadratic-surface parameterization generates shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. The results of the calculations in terms of potential-energy surfaces and fission half-lives are presented for heavy even nuclei. The surfaces are displayed in the form of contour diagrams as functions of two moments of the shape. 53 refs., 15 figs., 1 tab.

  3. Late Quaternary geomorphology and soils in Crater Flat, Yucca mountain area, southern Nevada

    SciTech Connect

    Peterson, F.F.; Bell, J.W.; Ramelli, A.R.; Dorn, R.I.; Ku, T.L.

    1995-04-01

    Crater Flat is an alluvium-filled structural basin on the west side of Yucca Mountain, Nevada, which is under consideration for a high-level nuclear waste repository. North-trending, late Quaternary faults offset alluvium in Crater Flat both along the canyons of the western flanks of Yucca Mountain and out on the piedmont slope. We believe the initial lack of young offsets at Yucca Mountain was in part due to unrecognized late Quaternary stratigraphy. We hypothesize that alluviation in the Yucca Mountain region was more active during the late Quaternary than previously thought. Several techniques were tried to test this hypothesis. Results are compared with previous soils and surface-exposure dating studies, and correlated to stratigraphy of other late Quaternary units in the southern Nevada, Death Valley, and Mojave Desert areas, and provide new stratigraphic data relevant to understanding climatic-alluvial processes in the Basin and Range Province during the late Quaternary. 76 refs., 7 figs., 6 tabs.

  4. Early results utilizing high-energy fission product (gamma) rays to detect fissionable material in cargo

    SciTech Connect

    Slaughter, D R; Accatino, M R; Bernstein, A; Church, J A; Descalle, M A; Gosnell, T B; Hall, J M; Loshak, A; Manatt, D R; Mauger, G J; McDowell, M; Moore, T M; Norman, E B; Pohl, B A; Pruet, J A; Petersen, D C; Walling, R S; Weirup, D L; Prussin, S G

    2004-09-30

    A concept for detecting the presence of special nuclear material ({sup 235}U or {sup 239}Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their {beta}-delayed neutron emission or {beta}-delayed high-energy {gamma}-radiation between beam pulses provide the detection signature. Fission product {beta}-delayed {gamma}-rays above 3 MeV are nearly ten times more abundant than {beta}-delayed neutrons and are distinct from natural radioactivity and from nearly all of the induced activity in a normal cargo. Detector backgrounds and potential interferences with the fission signature radiation have been identified and quantified. An important goal in the US is the detection of nuclear weapons or special nuclear material (SNM) concealed in intermodal cargo containers. This must be done with high detection probability, low false alarm rates, and without impeding commerce, i.e. about one minute for an inspection. The concept for inspection has been described before and its components are now being evaluated. While normal radiations emitted from plutonium may allow its detection, the majority of {sup 235}U {gamma} ray emission is at 186 keV, is readily attenuated by cargo, and thus not a reliable detection signature for passive detection. Delayed neutron detection following a neutron or photon beam pulse has been used successfully to detect lightly or unshielded SNM targets. While delayed neutrons can be easily distinguished from beam neutrons they have relatively low yield in fission, approximately 0.008 per fission in {sup 239}Pu and 0.017 per fission in {sup 235}U, and are rapidly attenuated in hydrogenous materials making that technique unreliable when challenged by thick hydrogenous cargo overburden. They propose detection of {beta}-delayed high-energy {gamma} radiation as a more robust signature characteristic of SNM.

  5. Electron-capture delayed fission properties of 244Es

    SciTech Connect

    Shaughnessy, Dawn A.; Gregorich, Kenneth E.; Adams, Jeb L.; Lane, Michael R.; Laue, Carola A.; Lee, Diana M.; McGrath, Christopher A.; Ninov, Victor; Patin, Joshua B.; Strellis, Dan A.; Sylwester, Eric R.; Wilk, Philip A.; Hoffman, Darleane C.

    2001-03-16

    Electron-capture delayed fission was observed in {sup 244}Es produced via the {sup 237}Np({sup 12}C,5n){sup 244}Es reaction at 81 MeV (on target) with a production cross section of 0.31{+-}0.12 {micro}b. The mass-yield distribution of the fission fragments is highly asymmetric. The average preneutron-emission total kinetic energy of the fragments was measured to be 186{+-}19 MeV. Based on the ratio of the number of fission events to the measured number of {alpha} decays from the electron-capture daughter {sup 244}Cf (100% {alpha} branch), the probability of delayed fission was determined to be (1.2{+-}0.4) x 10{sup -4}. This value for the delayed fission probability fits the experimentally observed trend of increasing delayed fission probability with increasing Q value for electron-capture.

  6. Cross section for the subthreshold fission of {sup 236}U

    SciTech Connect

    Alekseev, A. A.; Bergman, A. A.; Berlev, A. I.; Koptelov, E. A.; Samylin, B. F.; Trufanov, A. M.; Fursov, B. I.; Shorin, V. S.

    2008-08-15

    The cross section for {sup 236}U fission in the neutron-energy range E{sub n} = 0.001-20 keV was measured by using the INR RAS (Institute of Nuclear Research, Russian Academy of Sciences, Moscow) LSDS-100 neutron spectrometer of the lead slowing-down spectrometer type. The resonance fission areas of the resonances at 5.45 eV and 1.28 keV were found, and the fission widths of these resonances were evaluated. The cross section for the {sup 238}U(n, f) fission process was measured, and the threshold sensitivity of the LSDS-100 to small values of fission cross sections was estimated. The well-known intermediate structure in the cross section for the neutron-induced subbarrier fission of {sup 236}U was confirmed.

  7. Experiments on nuclear fission induced by radioactive beams

    SciTech Connect

    Skobelev, N.K.

    1994-07-01

    The cross sections of {sup 209}Bi nuclear fission induced by secondary beams of {sup 6}He and {sup 4}He are measured under identical conditions. The experimental data are in good agreement with earlier results on the fission cross section of the {sup 4}He + {sup 209}Bi reaction. The measured values of the cross section of {sup 209}Bi fission induced by {sup 6}He ions are much higher than the cross sections of fission induced by {alpha}-particles. It is found that the fission threshold for the {sup 6}He + {sup 209}Bi reaction is shifted as compared to that of the {sup 4}He + {sup 209}Bi reaction. Various factors that can be responsible for the observed peculiarities in the {sup 209}Bi fission induced by the {sup 6}He ions are analyzed. 25 refs., 5 figs.

  8. Prompt fission gamma-ray studies at DANCE

    SciTech Connect

    Jandel, M.; Rusev, G.; Bond, E. M.; Bredeweg, T. A.; Chadwick, M. B.; Couture, A.; Fowler, M.. M; Haight, R. C.; Kawano, T.; Keksis, A. L.; Mosby, S. M.; O’Donnell, J. M.; Rundberg, R. S.; Stetcu, I.; Talou, P.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Stoyer, M. A.; Haslett, R. J.; Henderson, R. A.; Becker, J. A.; Wu, C. Y.

    2014-11-26

    Measurements of correlated data on prompt-fission ?-rays (PFG) have been carried out for various actinide isotopes in recent years using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL). We have developed a model that conveniently parametrizes the correlated data of ?-ray multiplicity and energy. New results on two- dimensional prompt-fission ?-ray multiplicity versus energy distributions from spontaneous fission on ²?²Cf and neutron-induced fission on 242mAm are presented together with previously obtained results on 233,235U and ²³?Pu. Correlated PFG data from ²?²Cf are also compared to results of the detailed theoretical model developed at LANL, for different thresholds of PFG energies. Future plans to measure correlated data on fission fragments, prompt fission neutrons and ?-rays at DANCE are presented.

  9. Exotic fission properties of highly neutron-rich Uranium isotopes

    E-print Network

    L. Satpathy; S. K. Patra; R. K. Choudhury

    2007-03-05

    The series of Uranium isotopes with $N=154 \\sim 172$ around the magic number N=162/164 are identified to be thermally fissile. The thermal neutron fission of a typical representative $^{249}$U of this region amenable to synthesis in the radioactive ion beam facilities is considered here. Semiempirical study of fission barrier height and width shows this nucleus to be infinitely stable against spontaneous fission due to increase in barrier width arising out of excess neutrons. Calculation of probability of fragment mass yields and microscopic study in relativistic mean field theory, show this nucleus to undergo a new mode of thermal fission decay termed {\\it multifragmentation fission} where a number of prompt scission neutrons are simultaneously released along with the two heavy fission fragments.

  10. Prompt fission gamma-ray studies at DANCE

    DOE PAGESBeta

    Jandel, M.; Rusev, G.; Bond, E. M.; Bredeweg, T. A.; Chadwick, M. B.; Couture, A.; Fowler, M.. M; Haight, R. C.; Kawano, T.; Keksis, A. L.; et al

    2014-11-26

    Measurements of correlated data on prompt-fission ?-rays (PFG) have been carried out for various actinide isotopes in recent years using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL). We have developed a model that conveniently parametrizes the correlated data of ?-ray multiplicity and energy. New results on two- dimensional prompt-fission ?-ray multiplicity versus energy distributions from spontaneous fission on ²?²Cf and neutron-induced fission on 242mAm are presented together with previously obtained results on 233,235U and ²³?Pu. Correlated PFG data from ²?²Cf are also compared to results of the detailed theoretical model developed at LANL,more »for different thresholds of PFG energies. Future plans to measure correlated data on fission fragments, prompt fission neutrons and ?-rays at DANCE are presented.« less

  11. Prompt Fission Gamma-ray Studies at DANCE

    NASA Astrophysics Data System (ADS)

    Jandel, M.; Rusev, G.; Bond, E. M.; Bredeweg, T. A.; Chadwick, M. B.; Couture, A.; Fowler, M. M.; Haight, R. C.; Kawano, T.; Keksis, A. L.; Mosby, S. M.; O'Donnell, J. M.; Rundberg, R. S.; Stetcu, I.; Talou, P.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Stoyer, M. A.; Haslett, R. J.; Henderson, R. A.; Becker, J. A.; Wu, C. Y.

    Measurements of correlated data on prompt-fission ?-rays (PFG) have been carried out for various actinide isotopes in recent years using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL). We have developed a model that conveniently parametrizes the correlated data of ?-ray multiplicity and energy. New results on two- dimensional prompt-fission ?-ray multiplicity versus energy distributions from spontaneous fission on 252Cf and neutron-induced fission on 242mAm are presented together with previously obtained results on 233,235U and 239Pu. Correlated PFG data from 252Cf are also compared to results of the detailed theoretical model developed at LANL, for different thresholds of PFG energies. Future plans to measure correlated data on fission fragments, prompt fission neutrons and ?-rays at DANCE are presented.

  12. Quaternary extensional and compressional tectonics revealed from Quaternary landforms along Kosi River valley, outer Kumaun Lesser Himalaya, Uttarakhand

    NASA Astrophysics Data System (ADS)

    Luirei, Khayingshing; Bhakuni, S. S.; Kothyari, Girish Ch.; Tripathi, Kavita; Pant, P. D.

    2015-06-01

    A portion of the Kosi River in the outer Kumaun Lesser Himalaya is characterized by wide river course situated south of the Ramgarh Thrust, where huge thickness (~200 m) of the landslide deposits and two to three levels of unpaired fan terraces are present. Brittle normal faults, suggesting extensional tectonics, are recognized in the Quaternary deposits and bedrocks as further supported by surface morphology. Trending E-W, these faults measure from 3 to 5 km in length and are traced as discontinuous linear mini-horst and fault scarps (sackungen) exposed due to cutting across by streams. Active normal faults have displaced the coarsely laminated debris fan deposits at two sites located 550 m apart. At one of the sites, the faults look like bookshelf faulting with the maximum displacement of ~2 m and rotation of the Quaternary boulders along the fault plane is observed. At another site, the maximum displacement measures about 0.60 cm. Thick mud units deposited due to blocking of the streams by landslides are observed within and above the fan deposit. Landslide debris fans and terrace landforms are widely developed; the highest level of fan is observed ~1240 m above mean sea level. At some places, the reworking of the debris fans by streams is characterized by thick laminated sand body. Along the South Almora Thrust and Ramgarh Thrust zones, the valleys are narrow and V-shaped where Quaternary deposits are sparse due to relatively rapid uplift across these thrusts. Along the South Almora Thrust zone, three to four levels of fluvial terraces are observed and have been incised by river exposing the bedrocks due to recent movement along the RT and SAT. Abandoned channel, tilted mud deposits, incised meandering, deep-cut V-shaped valleys and strath terraces indicate rapid uplift of the area. Thick mud sequences in the Quaternary columns indicate damming of streams. A ~10-km-long north-south trending transverse Garampani Fault has offset the Ramgarh Thrust producing tectonic landforms.

  13. The behavior of the fission products, as they are released from fission events during nuclear reaction, plays an important role in nuclear fuel performance. Fission product release can occur through grain

    E-print Network

    The behavior of the fission products, as they are released from fission events during nuclear reaction, plays an important role in nuclear fuel performance. Fission product release can occur through grain boundary (GB) at low burnups ; therefore, this study simulates the mass transport of fission gases

  14. Sharp change over from compound nuclear fission to shape dependent quasi fission

    E-print Network

    T. K. Ghosh; K. Banerjee; C. Bhattacharya; S. Bhattacharya; S. Kundu; P. Mali; J. K. Meena; G. Mukherjee; S. Mukhopadhyay; T. K. Rana; P. Bhattacharya; K. S. Golda

    2008-09-17

    Fission fragment mass distribution has been measured from the decay of $^{246}$Bk nucleus populating via two entrance channels with slight difference in mass asymmetries but belonging on either side of the Businaro Gallone mass asymmetry parameter. Both the target nuclei were deformed. Near the Coulomb barrier, at similar excitation energies the width of the fission fragment mass distribution was found to be drastically different for the $^{14}$N + $^{232}$Th reaction compared to the $^{11}$B + $^{235}$U reaction. The entrance channel mass asymmetry was found to affect the fusion process sharply.

  15. Mass resolved angular distribution of fission fragments for near-barrier fusion-fission reactions

    SciTech Connect

    Vorkapic, D.

    1997-05-01

    It is shown that K-equilibration fission can explain the decrease of mass resolved fission fragment anisotropy at larger mass asymmetries. Two competing mechanisms contribute to the anisotropy. The effective moment of inertia and K{sub 0}{sup 2} decreases with the increase of mass asymmetry and contribute to the increase of anisotropy. On the other hand, for larger asymmetries, the barriers are higher and lifetimes are longer. Such systems are more K equilibrated and will have smaller anisotropy. {copyright} {ital 1997} {ital The American Physical Society}

  16. Distribution and metabolism of quaternary amines in salt marshes

    NASA Technical Reports Server (NTRS)

    King, Gary M.

    1985-01-01

    Quaternary amines such as glycine betaine (GBT) are common osmotically active solutes in much of the marine biota. GBT is accumulated by various bacteria, algae, higher plants, invertebrates, and vertebrates in response to salinity or water stresses; in some species, GBT occurs at tens to hundreds of millimolar concentrations and can account for a significant fraction of total nitrogen. Initial studies suggest that GBT is readily converted to two potential methane precursors, trimethylamine (TMA) and acetate, in anoxic sediments. TMA is apparently the most important methane precursor in surface sediments containing sulfate reducing bacteria. In salt marshes, the bulk of the methane formed may be due to the metabolism of TMA rather than other substrates. Current research is focussed on testing this hypothesis and on determining the role of quaternary amino osmoregulatory solutes in methane fluxes from marine environments. Preliminary studies have dealt with several problems: (1) determination of GBT concentrations in the dominant flora and fauna of salt marshes; (2) synthesis of radiolabelled GBT for metabolic studies; and (3) determination of fates of BGT in marine sediments using radiotracers. Both GC and HPLC techniques have been used to assay GBT concentrations in plant and animal tissues. S. alterniflora is probably the only significant source of GBT (and indirectly of methane) since the biomass and distribution of most other species is limited. Current estimates suggest that S. alterniflora GBT could account for most of the methane efflux from salt marshes.

  17. Global warming: Perspectives from the Late Quaternary paleomammal record

    SciTech Connect

    Graham, R.W. )

    1993-03-01

    Global warming at the end of the Pleistocene caused significant environmental changes that directly and indirectly effected biotic communities. The biotic response to this global warming event can provide insights into the processes that might be anticipated for future climatic changes. The megafauna extinction may have been the most dramatic alteration of mammalian communities at the end of the Pleistocene. Late Quaternary warming also altered regional diversity patterns for some small mammal guilds without extinction. Reductions in body size for both small and large mammal species were also consequences of these environmental fluctuations. Geographic shifts in the distributions of individual mammal species resulted in changes in species composition of mammalian communities. The individualistic response of biota to environmental fluctuations define some boundary conditions for modeling communities. Understanding these boundary conditions is mandatory in planning for the preservation of biodiversity in the future. Finally, it is essential to determine how global warming will alter seasonal patterns because it is apparent from the paleobiological record that not all Quaternary warming events have been the same.

  18. Ecostratigraphic datums and sequence stratigraphy: Application to the marine Quaternary

    SciTech Connect

    Martin, R.E. ); Neff, E. ); Johnson, G.W. ); Krantz, D. )

    1991-03-01

    The marine Quaternary is characterized by few evolutionary appearances and extinctions of planktonic foraminifera. Because climatic fluctuations are a fundamental characteristic of Pleistocene, however, better stratigraphic resolution of the marine Quaternary can be gained by the establishment of biozones based on climatically controlled foraminiferal assemblages. Utilizing relative abundances of the warm-water Globorotalia menardii complex and temperature-water G. inflata, supplemented by left- and right-coiling varieties of G. truncatulinoides, the authors have subdivided the prezone-W Pleistocene of the tropical Atlantic (Core V16-205), Caribbean Sea (DSDP Core 502B), and northeast Gulf of Mexico (ODP Core 625B, Eureka Core E67-135) into 17 subzones, each with an average duration of {approximately}100,000 yrs. The subzones appear to reflect water mass shifts and disjunct species distributions resulting from expansion and contraction of northern hemisphere ice sheets. Hence, subzonal boundaries should also reflect change in eustatic sea level and sequence boundaries. Indeed, graphic correlation of the subzones, along with biostratigraphic markers and paleomagnetic and oxygen isotope datums, reveals changes in sediment accumulation rate (especially on the continental slope) and missing section, as well as intervals of deformation (core breaks) that affect the occurrence of subzonal boundaries and biostratigraphic markers.

  19. Historical distribution of Sundaland's Dipterocarp rainforests at Quaternary glacial maxima.

    PubMed

    Raes, Niels; Cannon, Charles H; Hijmans, Robert J; Piessens, Thomas; Saw, Leng Guan; van Welzen, Peter C; Slik, J W Ferry

    2014-11-25

    The extent of Dipterocarp rainforests on the emergent Sundaland landmass in Southeast Asia during Quaternary glaciations remains a key question. A better understanding of the biogeographic history of Sundaland could help explain current patterns of biodiversity and support the development of effective forest conservation strategies. Dipterocarpaceae trees dominate the rainforests of Sundaland, and their distributions serve as a proxy for rainforest extent. We used species distribution models (SDMs) of 317 Dipterocarp species to estimate the geographic extent of appropriate climatic conditions for rainforest on Sundaland at the last glacial maximum (LGM). The SDMs suggest that the climate of central Sundaland at the LGM was suitable to sustain Dipterocarp rainforest, and that the presence of a previously suggested transequatorial savannah corridor at that time is unlikely. Our findings are supported by palynologic evidence, dynamic vegetation models, extant mammal and termite communities, vascular plant fatty acid stable isotopic compositions, and stable carbon isotopic compositions of cave guano profiles. Although Dipterocarp species richness was generally lower at the LGM, areas of high species richness were mostly found off the current islands and on the emergent Sunda Shelf, indicating substantial species migration and mixing during the transitions between the Quaternary glacial maxima and warm periods such as the present. PMID:25385612

  20. Late Quaternary terrestrial vertebrate coprolites from New Zealand

    NASA Astrophysics Data System (ADS)

    Wood, Jamie R.; Wilmshurst, Janet M.

    2014-08-01

    Over the past decade, concerted efforts to find and study Late Quaternary terrestrial vertebrate coprolites in New Zealand have revealed new insights into the diets and ecologies of New Zealand's prehistoric birds. Here, we provide a broader review of the coprolites found in natural (non-archaeological) Late Quaternary deposits from New Zealand. We summarise the morphological diversity of the coprolites, and discuss the taphonomy of the sites in which they are found. Since the 1870s more than 2000 coprolites have been discovered from 30 localities, all restricted to the South Island. The distribution of coprolite localities appears to reflect the presence of geological and climatic factors that enhance the potential for coprolite preservation; coprolites require dry conditions for preservation, and have been found on the ground surface within drafting cave entrances and at shallow (<300 mm) depths beneath rock overhangs with a northerly aspect. We classify the coprolites into eleven morphotypes, each of which may represent a range of different bird and/or reptile species. A review of genetically identified specimens shows that coprolites of different bird species overlap in size and morphology, reinforcing the need for identifications to be based on ancient DNA analysis.

  1. European quaternary refugia: a factor in large carnivore extinction?

    NASA Astrophysics Data System (ADS)

    O'Regan, Hannah J.; Turner, Alan; Wilkinson, David M.

    2002-12-01

    The extinction of large carnivores in Europe during the Quaternary is reviewed and the potential role of glacial refugia in these extinctions is investigated using the VORTEX model for population viability analysis. A model was built for a medium sized big cat similar to the extinct Panthera gombaszoegensis utilising life history data from the modern jaguar Panthera onca. This approach highlighted the potential importance of glacial refugia in the extinction process. Even model refugia the size of the Italian peninsula did not guarantee persistence of a population over a 1000 yr time span, illustrating the role of chance in survival in such a refugium. An area the size of the largest Mediterranean island was unable to support a big cat population for a period of 1000 yr. The models also demonstrated the importance of inbreeding as a mechanism for extinction in refugia. It is suggested that repeated genetic bottlenecks during successive glaciations would tend to remove lethal recessive alleles from the population, increasing the probability of survival in refugia in subsequent glaciations. The history of extinction of large carnivores in the European Quaternary is interpreted in the light of these results.

  2. Neutron emission from fission fragments during acceleration p

    SciTech Connect

    Hinde, D.J.; Charity, R.J.; Foote, G.S.; Leigh, J.R.; Newton, J.O.; Ogaza, S.; Chatterjee, A.

    1984-03-19

    Fission-neutron angular correlations following fusion of /sup 19/F and /sup 232/Th have been measured. Conventional analysis, based on the approximation that post-fission neutrons originate only from fully accelerated fission fragments, gives unexpectedly large numbers of ''prefission'' neutrons. Comparison with the considerably less fissile system /sup 200/Pb gives the first convincing evidence that this approach is inadequate. Consideration of neutron emission from the accelerating fragments gives results consistent with expectations.

  3. Fission of actinide nuclei using multi-nucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Léguillon, Romain; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Makii, Hiroyuki; Nishinaka, Ichiro; Ishii, Tetsuro; Tsukada, Kazuaki; Asai, Masato; Chiba, Satoshi; Ohtsuki, Tsutomu; Araki, Shohei; Watanabe, Yukinobu; Tatsuzawa, Ryotaro; Takaki, Naoyuki

    2014-09-01

    We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. Present study is supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan.

  4. New Fission Cross Section Measurements using a Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Sadler, Michael

    2008-03-01

    A group of six universities (ACU, California Polytechnic, Colorado School of Mines, Georgia Institute of Technology, Ohio, and Oregon State) and three national laboratories (Los Alamos, Lawrence Livermore, and Idaho) have undertaken the task of building a Time Projection Chamber (TPC) to measure the fission cross sections needed for the next generation of nuclear reactors. The fission TPC concept will be presented, and why we think we can improve on 50 years of fission study.

  5. Search for {beta}-delayed fission of {sup 228}Ac

    SciTech Connect

    Xu Yanbing; Ding Huajie; Yuan Shuanggui; Yang Weifan; Niu Yanning; Li Yingjun; Xiao Yonghou; Zhang Shengdong; Lu Xiting

    2006-10-15

    Radium was radiochemically separated from natural thorium. Thin {sup 228}Ra{yields}{beta}{sup -228}Ac sources were prepared and exposed to mica fission track detectors, and measured by an HPGe {gamma}-ray detector. The {beta}-delayed fission events of {sup 228}Ac were observed and its {beta}-delayed fission probability was found to be (5{+-}2)x10{sup -12}.

  6. Fission studies with 140 MeV $\\bm?$-Particles

    E-print Network

    A. Buttkewitz; H. H. Duhm; F. Goldenbaum; H. Machner; W. Strauss

    2009-07-23

    Binary fission induced by 140 MeV $\\alpha$-particles has been measured for $^{\\rm nat}$Ag, $^{139}$La, $^{165}$Ho and $^{197}$Au targets. The measured quantities are the total kinetic energies, fragment masses, and fission cross sections. The results are compared with other data and systematics. A minimum of the fission probability in the vicinity $Z^2/A=24$ is observed.

  7. Elutriation for Cell Cycle Synchronization in Fission Yeast.

    PubMed

    Kume, Kazunori

    2016-01-01

    Cell synchronization is a powerful technique for studying the eukaryotic cell cycle events precisely. The fission yeast is a rod-shaped cell whose growth is coordinated with the cell cycle. Monitoring the cellular growth of fission yeast is a relatively simple way to measure the cell cycle stage of a cell. Here, we describe a detailed method of unperturbed cell synchronization, named centrifugal elutriation, for fission yeast. PMID:26254921

  8. Neutron flux profile monitor for use in a fission reactor

    DOEpatents

    Kopp, Manfred K. (Oak Ridge, TN); Valentine, Kenneth H. (Lenoir City, TN)

    1983-01-01

    A neutron flux monitor is provided which consists of a plurality of fission counters arranged as spaced-apart point detectors along a delay line. As a fission event occurs in any one of the counters, two delayed current pulses are generated at the output of the delay line. The time separation of the pulses identifies the counter in which the particular fission event occured. Neutron flux profiles of reactor cores can be more accurately measured as a result.

  9. Proton induced fission of 181-Ta at relativistic energies

    E-print Network

    Y. Ayyad; J. Benlliure; E. Casarejos; H. Álvarez-Pol; A. Bacquias; A. Boudard; M. Caamaño; T. Enqvist; V. Föhr; A. Keli?-Heil; K. Kezzar; S. Leray; C. Paradela; D. Pérez-Loureiro; R. Pleska?; D. Tarrío

    2012-03-07

    Total fission cross sections of 181-Ta induced by protons at different relativistic energies have been measured at GSI, Darmstadt. The inverse kinematics technique used together with a dedicated set-up, made it possible to determine these cross sections with high accuracy. The new data obtained in this experiment will contribute to the understanding of the fission process at high excitation energies. The results are compared with data from previous experiments and systematics for proton-induced fission cross sections.

  10. Cell Shape and Cell Division in Fission Yeast Minireview

    PubMed Central

    Piel, Matthieu; Tran, Phong T.

    2010-01-01

    The fission yeast Schizosaccharomyces pombe has served as an important model organism for investigating cellular morphogenesis. This unicellular rod-shaped fission yeast grows by tip extension and divides by medial fission. In particular, microtubules appear to define sites of polarized cell growth by delivering cell polarity factors to the cell tips. Microtubules also position the cell nucleus at the cell middle, marking sites of cell division. Here, we review the microtubule-dependent mechanisms that regulate cell shape and cell division in fission yeast. PMID:19906584

  11. Fission Study Using Multi-Nucleon Transfer Reactions

    NASA Astrophysics Data System (ADS)

    Nishio, K.; Hirose, K.; L?guillon, R.; Makii, H.; Nishinaka, I.; Orlandi, R.; Smallcombe, J.; Ishii, T.; Tsukada, K.; Asai, M.; Chiba, S.; Ohtsuki, T.; Tatsuzawa, R.; Takaki, N.

    2015-06-01

    Fission study using multi-nucleon transfer reaction will be discussed. This approach has an advantage that we can study fission of neutron-rich nuclei which cannot be accessed by particle or charged-particle capture reactions. Unique feature in our setup is that we can produce fission data for many nuclei using many transfer-channels. Also wide excitation energy range can be covered in this set up, allowing us to measure the excitation energy dependence of the fission properties. Preliminary data obtained in the 18O + 238U reaction will be presented..

  12. The Nature of Singlet Exciton Fission in Carotenoid Aggregates

    PubMed Central

    2015-01-01

    Singlet exciton fission allows the fast and efficient generation of two spin triplet states from one photoexcited singlet. It has the potential to improve organic photovoltaics, enabling efficient coupling to the blue to ultraviolet region of the solar spectrum to capture the energy generally lost as waste heat. However, many questions remain about the underlying fission mechanism. The relation between intermolecular geometry and singlet fission rate and yield is poorly understood and remains one of the most significant barriers to the design of new singlet fission sensitizers. Here we explore the structure–property relationship and examine the mechanism of singlet fission in aggregates of astaxanthin, a small polyene. We isolate five distinct supramolecular structures of astaxanthin generated through self-assembly in solution. Each is capable of undergoing intermolecular singlet fission, with rates of triplet generation and annihilation that can be correlated with intermolecular coupling strength. In contrast with the conventional model of singlet fission in linear molecules, we demonstrate that no intermediate states are involved in the triplet formation: instead, singlet fission occurs directly from the initial 1Bu photoexcited state on ultrafast time scales. This result demands a re-evaluation of current theories of polyene photophysics and highlights the robustness of carotenoid singlet fission. PMID:25825939

  13. Generalized Energy-Dependent Q Values for Fission

    SciTech Connect

    Vogt, R

    2010-03-31

    We extend Madland's parameterization of the energy release in fission to obtain the dependence of the fission Q value for major and minor actinides on the incident neutron energies in the range 0 {le} E{sub n} {le} 20 MeV. Our parameterization is based on the actinide evaluations recommended for the ENDF/B-VII.1 release. This paper describes the calculation of energydependent fission Q values based on the calculation of the prompt energy release in fission by Madland. This calculation was adopted for use in the LLNL ENDL database and then generalized to obtain the prompt fission energy release for all actinides. Here the calculation is further generalized to the total energy release in fission. There are several stages in a fission event, depending on the time scale. Neutrons and gammas may be emitted at any time during the fission event.While our discussion here is focussed on compound nucleus creation by an incident neutron, similar parameterizations could be obtained for incident gammas or spontaneous fission.

  14. A double ionization chamber for fission fragment detection

    NASA Astrophysics Data System (ADS)

    Chepigin, V. I.; Stepantsov, S. V.; Nagy, S.; Ter-Akopian, G. M.; Voronin, A. S.

    1984-03-01

    In the present paper some problems associated with studies of the spontaneous fission of transfermium elements are considered, and advantages of ionization chambers over other detectors for fission fragment detection are discussed. A double ionization chamber for detecting fission fragments has been built, and the energy and mass calibrations have been performed using the thermal neutron-induced fission of 235U. The use of a gas jet, in combination with a double ionization chamber as a detector, in experiments with heavy ions is discussed. Model experiments have been carried out.

  15. The nature of singlet exciton fission in carotenoid aggregates.

    PubMed

    Musser, Andrew J; Maiuri, Margherita; Brida, Daniele; Cerullo, Giulio; Friend, Richard H; Clark, Jenny

    2015-04-22

    Singlet exciton fission allows the fast and efficient generation of two spin triplet states from one photoexcited singlet. It has the potential to improve organic photovoltaics, enabling efficient coupling to the blue to ultraviolet region of the solar spectrum to capture the energy generally lost as waste heat. However, many questions remain about the underlying fission mechanism. The relation between intermolecular geometry and singlet fission rate and yield is poorly understood and remains one of the most significant barriers to the design of new singlet fission sensitizers. Here we explore the structure-property relationship and examine the mechanism of singlet fission in aggregates of astaxanthin, a small polyene. We isolate five distinct supramolecular structures of astaxanthin generated through self-assembly in solution. Each is capable of undergoing intermolecular singlet fission, with rates of triplet generation and annihilation that can be correlated with intermolecular coupling strength. In contrast with the conventional model of singlet fission in linear molecules, we demonstrate that no intermediate states are involved in the triplet formation: instead, singlet fission occurs directly from the initial 1B(u) photoexcited state on ultrafast time scales. This result demands a re-evaluation of current theories of polyene photophysics and highlights the robustness of carotenoid singlet fission. PMID:25825939

  16. Magnetic Materials Suitable for Fission Power Conversion in Space Missions

    NASA Technical Reports Server (NTRS)

    Bowman, Cheryl L.

    2012-01-01

    Terrestrial fission reactors use combinations of shielding and distance to protect power conversion components from elevated temperature and radiation. Space mission systems are necessarily compact and must minimize shielding and distance to enhance system level efficiencies. Technology development efforts to support fission power generation scenarios for future space missions include studying the radiation tolerance of component materials. The fundamental principles of material magnetism are reviewed and used to interpret existing material radiation effects data for expected fission power conversion components for target space missions. Suitable materials for the Fission Power System (FPS) Project are available and guidelines are presented for bounding the elevated temperature/radiation tolerance envelope for candidate magnetic materials.

  17. Fission barrier, damping of shell correction and neutron emission in the fission of A$\\sim$200

    E-print Network

    Mahata, K; Kapoor, S S

    2015-01-01

    Decay of $^{210}$Po compound nucleus formed in light and heavy-ion induced fusion reactions has been analyzed simultaneously using a consistent prescription for fission barrier and nuclear level density incorporating shell correction and its damping with excitation energy. Good description of all the excitation functions have been achieved with a fission barrier of 21.9 $\\pm$ 0.2 MeV. For this barrier height, the predicted statistical pre-fission neutrons in heavy-ion fusion-fission are much smaller than the experimental values, implying the presence of dynamical neutrons due to dissipation even at these low excitation energies ($\\sim$ 50~MeV) in the mass region A $\\sim$ 200. When only heavy-ion induced fission excitation functions and the pre-fission neutron multiplicities are included in the fits, the deduced best fit fission barrier depends on the assumed fission delay time during which dynamical neutrons can be emitted. A fission delay of (0.8 $\\pm$ 0.1 )$\\times 10^{-19}$ s has been estimated correspondin...

  18. Fission Product Data Measured at Los Alamos for Fission Spectrum and Thermal Neutrons on 239Pu, 235U, 238U

    NASA Astrophysics Data System (ADS)

    Selby, H. D.; Mac Innes, M. R.; Barr, D. W.; Keksis, A. L.; Meade, R. A.; Burns, C. J.; Chadwick, M. B.; Wallstrom, T. C.

    2010-12-01

    We describe measurements of fission product data at Los Alamos that are important for determining the number of fissions that have occurred when neutrons are incident on plutonium and uranium isotopes. The fission-spectrum measurements were made using a fission chamber designed by the National Institute for Standards and Technology (NIST) in the BIG TEN critical assembly, as part of the Inter-laboratory Liquid Metal Fast Breeder Reactor (LMFBR) Reaction Rate (ILRR) collaboration. The thermal measurements were made at Los Alamos' Omega West Reactor. A related set of measurements were made of fission-product ratios (so-called R-values) in neutron environments provided by a number of Los Alamos critical assemblies that range from having average energies causing fission of 400-600 keV (BIG TEN and the outer regions of the Flattop-25 assembly) to higher energies (1.4-1.9 MeV) in the Jezebel, and in the central regions of the Flattop-25 and Flattop-Pu, critical assemblies. From these data we determine ratios of fission product yields in different fuel and neutron environments (Q-values) and fission product yields in fission spectrum neutron environments for 99Mo, 95Zr, 137Cs, 140Ba, 141,143Ce, and 147Nd. Modest incident-energy dependence exists for the 147Nd fission product yield; this is discussed in the context of models for fission that include thermal and dynamical effects. The fission product data agree with measurements by Maeck and other authors using mass-spectrometry methods, and with the ILRR collaboration results that used gamma spectroscopy for quantifying fission products. We note that the measurements also contradict earlier 1950s historical Los Alamos estimates by ˜5-7%, most likely owing to self-shielding corrections not made in the early thermal measurements. Our experimental results provide a confirmation of the England-Rider ENDF/B-VI evaluated fission-spectrum fission product yields that were carried over to the ENDF/B-VII.0 library, except for 99Mo where the present results are about 4%-relative higher for neutrons incident on 239Pu and 235U. Additionally, our results illustrate the importance of representing the incident energy dependence of fission product yields over the fast neutron energy range for high-accuracy work, for example the 147Nd from neutron reactions on plutonium. An upgrade to the ENDF library, for ENDF/B-VII.1, based on these and other data, is described in a companion paper to this work.

  19. Antiproton Powered Gas Core Fission Rocket

    SciTech Connect

    Kammash, Terry

    2005-02-06

    Extensive research in recent years has demonstrated that 'at rest' annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas - inserted into the chamber just prior to the release of the antiproton - to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it.

  20. Isotopic Yields and Isoscaling in Fission

    E-print Network

    W. A. Friedman

    2003-11-21

    A simple model is proposed to examine the isotopic yields of the fragments from binary fission. For a given charge partition the peaks and widths in the isotope distributions are studied both with the liquid-drop model and with shell modifications. The basis for isoscaling is also explored. The symmetry energy plays a dominant role in both the distributions and the isoscaling behavior. A systematic increase in the isoscaling parameter, $\\alpha$, with the proton number of the fragment element is predicted in the context of the liquid-drop model. Deviations arising from shell corrections are explored.

  1. Recent fission cross section standards measurements

    SciTech Connect

    Wasson, O.A.

    1985-01-01

    The /sup 235/U(n,f) reaction is the standard by which most neutron induced fission cross sections are determined. Most of these cross sections are derived from relatively easy ratio measurements to /sup 235/U. However, the more difficult /sup 235/U(n,f) cross section measurements require the use of advanced neutron detectors for the determination of the incident neutron fluence. Examples of recent standard cross section measurements are discussed, various neutron detectors are described, and the status of the /sup 235/U(n,f) cross section standard is assessed. 23 refs., 8 figs., 4 tabs.

  2. Mechanics and morphogenesis of fission yeast cells.

    PubMed

    Davì, Valeria; Minc, Nicolas

    2015-12-01

    The integration of biochemical and biomechanical elements is at the heart of morphogenesis. While animal cells are relatively soft objects which shape and mechanics is mostly regulated by cytoskeletal networks, walled cells including those of plants, fungi and bacteria are encased in a rigid cell wall which resist high internal turgor pressure. How these particular mechanical properties may influence basic cellular processes, such as growth, shape and division remains poorly understood. Recent work using the model fungal cell fission yeast, Schizosaccharomyces pombe, highlights important contribution of cell mechanics to various morphogenesis processes. We envision this genetically tractable system to serve as a novel standard for the mechanobiology of walled cell. PMID:26291501

  3. Excitation energy dependence of fission in the mercury region

    E-print Network

    J. D. McDonnell; W. Nazarewicz; J. A. Sheikh; A. Staszczak; M. Warda

    2014-06-26

    Background: Recent experiments on beta-delayed fission reported an asymmetric mass yield in the neutron-deficient nucleus 180Hg. Earlier experiments in the mass region A=190-200 close to the beta-stability line, using the (p,f) and (\\alpha,f) reactions, observed a more symmetric distribution of fission fragments. While the beta-delayed fission of 180Hg can be associated with relatively low excitation energy, this is not the case for light-ion reactions, which result in warm compound nuclei. Purpose: To elucidate the roles of proton and neutron numbers and excitation energy in determining symmetric and asymmetric fission yields, we compute and analyze the isentropic potential energy surfaces of 174,180,198Hg and 196,210Po. Methods: We use the finite-temperature superfluid nuclear density functional theory, for excitation energies up to E*=30MeV and zero angular momentum. For our theoretical framework, we consider the Skyrme energy density functional SkM* and a density-dependent pairing interaction. Results: For 174,180Hg, we predict fission pathways consistent with asymmetric fission at low excitation energies, with the symmetric fission pathway opening very gradually as excitation energy is increased. For 198Hg and 196Po, we expect the nearly-symmetric fission channel to dominate. 210Po shows a preference for a slightly asymmetric pathway at low energies, and a preference for a symmetric pathway at high energies. Conclusions: Our self-consistent theory suggests that excitation energy weakly affects the fission pattern of the nuclei considered. The transition from the asymmetric fission in the proton-rich nuclei to a more symmetric fission in the heavier isotopes is governed by the shell structure of pre-scission configurations.

  4. Pairing-induced speedup of nuclear spontaneous fission

    DOE PAGESBeta

    Sadhukhan, Jhilam; Dobaczewski, J.; Nazarewicz, W.; Sheikh, J. A.; Baran, A.

    2014-12-22

    Collective inertia is strongly influenced at the level crossing at which the quantum system changes its microscopic configuration diabatically. Pairing correlations tend to make the large-amplitude nuclear collective motion more adiabatic by reducing the effect of these configuration changes. Competition between pairing and level crossing is thus expected to have a profound impact on spontaneous fission lifetimes. To elucidate the role of nucleonic pairing on spontaneous fission, we study the dynamic fission trajectories of 264Fm and 240Pu using the state-of-the-art self-consistent framework. We employ the superfluid nuclear density functional theory with the Skyrme energy density functional SkM* and a density-dependentmore »pairing interaction. Along with shape variables, proton and neutron pairing correlations are taken as collective coordinates. The collective inertia tensor is calculated within the nonperturbative cranking approximation. The fission paths are obtained by using the least action principle in a four-dimensional collective space of shape and pairing coordinates. Pairing correlations are enhanced along the minimum-action fission path. For the symmetric fission of 264Fm, where the effect of triaxiality on the fission barrier is large, the geometry of the fission pathway in the space of the shape degrees of freedom is weakly impacted by pairing. This is not the case for 240Pu, where pairing fluctuations restore the axial symmetry of the dynamic fission trajectory. The minimum-action fission path is strongly impacted by nucleonic pairing. In some cases, the dynamical coupling between shape and pairing degrees of freedom can lead to a dramatic departure from the static picture. As a result, in the dynamical description of nuclear fission, particle-particle correlations should be considered on the same footing as those associated with shape degrees of freedom.« less

  5. Fission neutron spectra measurements at LANSCE - status and plans

    SciTech Connect

    Haight, Robert C; Noda, Shusaku; Nelson, Ronald O; O' Donnell, John M; Devlin, Matt; Chatillon, Audrey; Granier, Thierry; Taieb, Julien; Laurent, Benoit; Belier, Gilbert; Becker, John A; Wu, Ching - Yen

    2009-01-01

    A program to measure fission neutron spectra from neutron-induced fission of actinides is underway at the Los Alamos Neutron Science Center (LANSCE) in a collaboration among the CEA laboratory at Bruyeres-le-Chatel, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The spallation source of fast neutrons at LANSCE is used to provide incident neutron energies from less than 1 MeV to 100 MeV or higher. The fission events take place in a gas-ionization fission chamber, and the time of flight from the neutron source to that chamber gives the energy of the incident neutron. Outgoing neutrons are detected by an array of organic liquid scintillator neutron detectors, and their energies are deduced from the time of flight from the fission chamber to the neutron detector. Measurements have been made of the fission neutrons from fission of {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. The range of outgoing energies measured so far is from 1 MeV to approximately 8 MeV. These partial spectra and average fission neutron energies are compared with evaluated data and with models of fission neutron emission. Results to date will be presented and a discussion of uncertainties will be given in this presentation. Future plans are to make significant improvements in the fission chambers, neutron detectors, signal processing, data acquisition and the experimental environment to provide high fidelity data including mea urements of fission neutrons below 1 MeV and improvements in the data above 8 MeV.

  6. Pairing-induced speedup of nuclear spontaneous fission

    SciTech Connect

    Sadhukhan, Jhilam; Dobaczewski, J.; Nazarewicz, W.; Sheikh, J. A.; Baran, A.

    2014-12-22

    Collective inertia is strongly influenced at the level crossing at which the quantum system changes its microscopic configuration diabatically. Pairing correlations tend to make the large-amplitude nuclear collective motion more adiabatic by reducing the effect of these configuration changes. Competition between pairing and level crossing is thus expected to have a profound impact on spontaneous fission lifetimes. To elucidate the role of nucleonic pairing on spontaneous fission, we study the dynamic fission trajectories of 264Fm and 240Pu using the state-of-the-art self-consistent framework. We employ the superfluid nuclear density functional theory with the Skyrme energy density functional SkM* and a density-dependent pairing interaction. Along with shape variables, proton and neutron pairing correlations are taken as collective coordinates. The collective inertia tensor is calculated within the nonperturbative cranking approximation. The fission paths are obtained by using the least action principle in a four-dimensional collective space of shape and pairing coordinates. Pairing correlations are enhanced along the minimum-action fission path. For the symmetric fission of 264Fm, where the effect of triaxiality on the fission barrier is large, the geometry of the fission pathway in the space of the shape degrees of freedom is weakly impacted by pairing. This is not the case for 240Pu, where pairing fluctuations restore the axial symmetry of the dynamic fission trajectory. The minimum-action fission path is strongly impacted by nucleonic pairing. In some cases, the dynamical coupling between shape and pairing degrees of freedom can lead to a dramatic departure from the static picture. As a result, in the dynamical description of nuclear fission, particle-particle correlations should be considered on the same footing as those associated with shape degrees of freedom.

  7. Quaternary Reorganization of North American Mid-continent Drainage Systems

    NASA Astrophysics Data System (ADS)

    Carson, E. C.; Rawling, J. E., III; Attig, J. W.; Bates, B. R.

    2013-12-01

    Identification of ancestral drainage systems in the North American mid-continent has been a topic of research and debate among geologists since the middle of the 19th Century. Over time our understanding of the significance of Quaternary glaciations in reshaping drainage patterns has grown. The ancestral Teays River, which drained large areas of the central Appalachians and flowed westward across Indiana and western Illinois, was dammed multiple times by Quaternary glaciers before finally being rerouted to the course of the modern central Ohio River. Similarly, the northward-flowing ancestral Pittsburgh River was dammed by pre-Illinoian glaciers; subsequent stream piracy converted this river system into the modern Allegheny, Monongahela and uppermost Ohio Rivers. Deposits and geomorphic features along the westward-flowing lower Wisconsin River indicate that the modern upper Mississippi River and Wisconsin River may have experienced a similar history of ice blockage, stream piracy, and radical rerouting. Coring into the Bridgeport strath terrace along the lower Wisconsin River reveals that the bedrock surface dips to the east, indicating the valley was cut by an eastward-flowing river. We believe the most likely scenario following this interpretation is that an ancestral river flowing along the modern upper Mississippi River valley made a sharp bend at Prairie du Chien, WI, and flowed eastward along the valley occupied by the modern lower Wisconsin River. This river, referred to here as the Wyalusing River, likely flowed northeastward into the Great Lakes (St. Lawrence) drainage until that path was blocked by ice advancing from the northwest. Subsequent stream piracy immediately south of the modern confluence of the Mississippi and Wisconsin Rivers rerouted these streams, converting them to the headwaters of the greater Mississippi drainage. The combined rerouting of these river systems into entirely different drainage basins necessitates significant fundamental changes to the total discharge of the St. Lawrence and Mississippi Rivers. While it is unclear if the Teays River ever flowed into the St. Lawrence drainage or developed as a westward-flowing tributary to the buried Mahomet valley in Illinois, both the ancestral Pittsburgh and Wyalusing Rivers originated as headwaters of the St. Lawrence basin before being rerouted as part of the Mississippi basin. The areas formerly drained by the Pittsburgh and Wyalusing Rivers comprise ~8% of the modern Mississippi River basin, and modern discharge from those areas represent ~14% of the mean annual discharge of the Mississippi River. The transfer of this drainage area and discharge to the Mississippi basin is mirrored by an equivalent loss from the St. Lawrence system during the Quaternary as a direct result of glacially-driven drainage system reorganization.

  8. Fission energy program of the US Department of Energy, FY 1981

    SciTech Connect

    Ferguson, Robert L.

    1980-03-01

    Information is presented concerning the National Energy Plan and fission energy policy; fission energy program management; converter reactor systems; breeder reactor systems; and special nuclear evaluations and systems.

  9. Asynchronous extinction of late Quaternary sloths on continents and islands

    PubMed Central

    Steadman, David W.; Martin, Paul S.; MacPhee, Ross D. E.; Jull, A. J. T.; McDonald, H. Gregory; Woods, Charles A.; Iturralde-Vinent, Manuel; Hodgins, Gregory W. L.

    2005-01-01

    Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their “last appearance” datum at ?11,000 radiocarbon years before present (yr BP) or slightly less in North America, ?10,500 yr BP in South America, and ?4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial–interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the sloth-bearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people. PMID:16085711

  10. Quaternary prevention, an answer of family doctors to overmedicalization.

    PubMed

    Jamoulle, Marc

    2015-02-01

    In response to the questioning of Health Policy and Management (HPAM) by colleagues on the role of rank and file family physicians in the same journal, the author, a family physician in Belgium, is trying to highlight the complexity and depth of the work of his colleagues and their contribution to the understanding of the organization and economy of healthcare. It addresses, in particular, the management of health elements throughout the ongoing relationship of the family doctor with his/her patients. It shows how the three dimensions of prevention, clearly included in the daily work, are complemented with the fourth dimension, quaternary prevention or prevention of medicine itself, whose understanding could help to control the economic and human costs of healthcare. PMID:25674569

  11. Quaternary prevention, an answer of family doctors to overmedicalization

    PubMed Central

    Jamoulle, Marc

    2015-01-01

    In response to the questioning of Health Policy and Management (HPAM) by colleagues on the role of rank and file family physicians in the same journal, the author, a family physician in Belgium, is trying to highlight the complexity and depth of the work of his colleagues and their contribution to the understanding of the organization and economy of healthcare. It addresses, in particular, the management of health elements throughout the ongoing relationship of the family doctor with his/her patients. It shows how the three dimensions of prevention, clearly included in the daily work, are complemented with the fourth dimension, quaternary prevention or prevention of medicine itself, whose understanding could help to control the economic and human costs of healthcare. PMID:25674569

  12. Quaternary eustatic sedimentary accretion of southern Bahamas Archipelago

    SciTech Connect

    Mitchell, S.W.

    1985-02-01

    Surficial geologic mapping indicates that the southern half of the Bahamas Archipelago is forming by the accretion of discrete depositional sequences resulting from successive eustatic sea level changes: (1) multiple beach and dune ridges, (2) estuarine, (3) lacustrine, (4) shallow subtidal, (5) reef and reef rubble, and (6) megadune complexes. The lithologies are accreted along unconformable erosional-solutional contacts - marine terraces and subaerial caliche crusts. During periods of significant transgression, sequences 1-5 are accreted. Sediments are predominantly skeletal and peloid. During periods of significant regression, megadune complexes are accreted. Ooids are the dominant sediment. Erosional-solutional features reflect areas of subaerial exposure and/or coastline erosion. Terraces at 10, 20, and 40 ft elevations are preserved along arid eastern Great Inagua Island. The calichification of Bahamian Quaternary carbonates has concentrated insoluble residues (quartz, feldspar, heavy minerals, crandallite, micrometeorites). Insoluble residue analysis provides a basis for the correlation of accreted eustatic sedimentary sequences.

  13. Control of Quaternary sea-level changes on gas seeps

    NASA Astrophysics Data System (ADS)

    Riboulot, Vincent; Thomas, Yannick; Berné, Serge; Jouet, Gwénaël.; Cattaneo, Antonio

    2014-07-01

    Gas seeping to the seafloor through structures such as pockmarks may contribute significantly to the enrichment of atmospheric greenhouse gases and global warming. Gas seeps in the Gulf of Lions, Western Mediterranean, are cyclical, and pockmark "life" is governed both by sediment accumulation on the continental margin and Quaternary climate changes. Three-dimensional seismic data, correlated to multi-proxy analysis of a deep borehole, have shown that these pockmarks are associated with oblique chimneys. The prograding chimney geometry demonstrates the syn-sedimentary and long-lasting functioning of the gas seeps. Gas chimneys have reworked chronologically constrained stratigraphic units and have functioned episodically, with maximum activity around sea level lowstands. Therefore, we argue that one of the main driving mechanisms responsible for their formation is the variation in hydrostatic pressure driven by relative sea level changes.

  14. Terrestrial paleoenvironmental effects of a late quaternary-age supernova

    NASA Astrophysics Data System (ADS)

    Brakenridge, G. R.

    1981-04-01

    Over 120 radio-emitting galactic supernova remnants (SNRs) have been catalogued. It is possible to evaluate the possible terrestrial importance of specific inferred radiation events. Because radio SNRs expand with age, and become indistinguishable from the interstellar medium at mean diameters of approximately 65 pc (ages of roughly 45,000 years), only late Quaternary time can be examined. However, it is for this period that detailed and well-dated terrestrial paleoenvironmental records are available. Such records can provide tests of any predicted supernova effects. There is at present considerable evidence supporting the hypothesis that the Vela supernova caused short-term but possibly severe terrestrial environmental changes. The information presented suggests that the effects to be predicted for the Vela supernova did occur, and began shortly after 11,000 C-14 yr B.P.

  15. Expanded record of Quaternary oceanographic change: Amerasian Arctic Ocean

    USGS Publications Warehouse

    Ishman, S.E.; Polyak, L.V.; Poore, R.Z.

    1996-01-01

    Four sediment cores collected from the Northwind and Mendeleyev ridges, Arctic Ocean, from 1089 m to 1909 m water depth, provide an oceanographic record extending back into the Matuyama reversed polarity chron. Benthic foraminiferal analyses show four prominent assemblage zones: Bolivina arctica, Cassidulina teretis, Bulimina aculeata, and Oridorsalis tener from the upper Matuyama reversed polarity chronozone through the Brunhes normal polarity chronozone. These assemblage zones represent depth-dependent benthic foraminiferal biofacies changes associated with oceanographic events that occurred in the Amerasian basin at ??? 780 and 300 ka, and indicate oceanographic influence from the North Atlantic. Recognition of these benthic assemblage zones in Arctic cores from the Alpha Ridge indicates that the benthic foraminiferal zonations in intermediate to deep water (>1000 m) Arctic cores may be more useful than preexisting lithostratigraphic zonations and should provide important information pertaining to the Quaternary paleoceanographic evolution of the Arctic Ocean.

  16. The Use of Quaternary Ammonium to Combat Dental Caries

    PubMed Central

    Ge, Yang; Wang, Suping; Zhou, Xuedong; Wang, Haohao; Xu, Hockin H. K.; Cheng, Lei

    2015-01-01

    Resin composites and adhesives are increasingly popular in dental restorations, but secondary caries is one of the main reasons for restoration failure. Quaternary ammonium monomers (QAMs) have an anti-microbial effect and are widely used in many fields. Since the concept of the immobilized antibacterial effect was put forward, dental restorations containing QAMs have been studied to reduce secondary caries. Previous studies have been struggling to develop novel anti-caries materials which might have triple benefits: good mechanical properties, antibacterial effects and remineralization potentials. Different kinds of QAMs have been proven to be effective in inhibiting the growth and metabolism of biofilms. Combination of QAMs and other nanoparticles in resin composites and adhesives could enhance their anti-caries capability. Therefore, QAMs are promising to show significant impact on the future of restorative and preventive dentistry. PMID:26635932

  17. Fission foil detector calibrations with high energy protons

    NASA Technical Reports Server (NTRS)

    Benton, E. V.; Frank, A. L.

    1995-01-01

    Fission foil detectors (FFD's) are passive devices composed of heavy metal foils in contact with muscovite mica films. The heavy metal nuclei have significant cross sections for fission when irradiated with neutrons and protons. Each isotope is characterized by threshold energies for the fission reactions and particular energy-dependent cross sections. In the FFD's, fission fragments produced by the reactions are emitted from the foils and create latent particle tracks in the adjacent mica films. When the films are processed surface tracks are formed which can be optically counted. The track densities are indications of the fluences and spectra of neutrons and/or protons. In the past, detection efficiencies have been calculated using the low energy neutron calibrated dosimeters and published fission cross sections for neutrons and protons. The problem is that the addition of a large kinetic energy to the (n,nucleus) or (p,nucleus) reaction could increase the energies and ranges of emitted fission fragments and increase the detector sensitivity as compared with lower energy neutron calibrations. High energy calibrations are the only method of resolving the uncertainties in detector efficiencies. At high energies, either proton or neutron calibrations are sufficient since the cross section data show that the proton and neutron fission cross sections are approximately equal. High energy proton beams have been utilized (1.8 and 4.9 GeV, 80 and 140 MeV) for measuring the tracks of fission fragments emitted backward and forward.

  18. Whole-rock uranium analysis by fission track activation

    NASA Technical Reports Server (NTRS)

    Weiss, J. R.; Haines, E. L.

    1974-01-01

    We report a whole-rock uranium method in which the polished sample and track detector are separated in a vacuum chamber. Irradiation with thermal neutrons induces uranium fission in the sample, and the detector records the integrated fission track density. Detection efficiency and geometric factors are calculated and compared with calibration experiments.

  19. The Neutron Induced Fission Fragment Tracking Experiment: Hardware Overview

    NASA Astrophysics Data System (ADS)

    Duke, Dana; Niffte Collaboration

    2011-04-01

    The goal of the Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) is to measure fission cross sections with unprecedented precision using time projection chamber (TPC) technology. The NIFFTE TPC hardware and supporting systems are discussed, including neutron source, gas system, and data acquisition. The current status of hardware implementation for the experiment will be presented.

  20. Mitochondrial Morphological Features Are Associated with Fission and Fusion Events

    PubMed Central

    Martin, Katie R.; Hlavacek, William S.; MacKeigan, Jeffrey P.

    2014-01-01

    Mitochondria are dynamic organelles that undergo constant remodeling through the regulation of two opposing processes, mitochondrial fission and fusion. Although several key regulators and physiological stimuli have been identified to control mitochondrial fission and fusion, the role of mitochondrial morphology in the two processes remains to be determined. To address this knowledge gap, we investigated whether morphological features extracted from time-lapse live-cell images of mitochondria could be used to predict mitochondrial fate. That is, we asked if we could predict whether a mitochondrion is likely to participate in a fission or fusion event based on its current shape and local environment. Using live-cell microscopy, image analysis software, and supervised machine learning, we characterized mitochondrial dynamics with single-organelle resolution to identify features of mitochondria that are predictive of fission and fusion events. A random forest (RF) model was trained to correctly classify mitochondria poised for either fission or fusion based on a series of morphological and positional features for each organelle. Of the features we evaluated, mitochondrial perimeter positively correlated with mitochondria about to undergo a fission event. Similarly mitochondrial solidity (compact shape) positively correlated with mitochondria about to undergo a fusion event. Our results indicate that fission and fusion are positively correlated with mitochondrial morphological features; and therefore, mitochondrial fission and fusion may be influenced by the mechanical properties of mitochondrial membranes. PMID:24733410

  1. Is bimodal fission an indirect experimental evidence for pionic radioactivity?

    E-print Network

    D. B. Ion; Reveica Ion-Mihai; M. L. Ion; Adriana I. Sandru

    2003-11-05

    In this paper new predictions for the spontaneous pion emission accompanied by fission are presented for all nuclei with Z between 100 and 108. The bimodal fission as an indirect experimental evidence for the pionic radioactivity is demonstrated. The experimental tests of this important connection are suggested.

  2. Fission-track ages from the Precambrian of Shropshire.

    USGS Publications Warehouse

    Naeser, C.W.; Toghill, P.; Ross, R.J., Jr.

    1982-01-01

    Four samples of Longmyndian and Uriconian strata from S of Shrewsbury, England have been processed for apatite and/or zircon fission-track ages. The resultant ages illustrate how depth of burial may affect fission-track ages. The analytical procedures followed were as described in Naeser (1979).-from Authors

  3. Electroplating method for producing ultralow-mass fissionable deposits

    DOEpatents

    Ruddy, Francis H. (Monroeville, PA)

    1989-01-01

    A method for producing ultralow-mass fissionable deposits for nuclear reactor dosimetry is described, including the steps of holding a radioactive parent until the radioactive parent reaches secular equilibrium with a daughter isotope, chemically separating the daughter from the parent, electroplating the daughter on a suitable substrate, and holding the electroplated daughter until the daughter decays to the fissionable deposit.

  4. A Fission-Powered Interstellar Precursor Mission

    SciTech Connect

    Lenard, R.X.; Lipinski, R.J.; West, J.L.; Wright, S.A.

    1998-10-28

    An 'interstellar precursor mission' lays the groundwork for eventual interstellar exploration by studying the interstellar medium and by stretching technologies that have potential application for eventual interstellar exploration. The numerous scientific goals for such a mission include generating a 3-D stellar map of our galaxy, studying Kuiper-belt and Oort cloud objects, and observing distant objects using the sun's gravitational lens as the primary of an enormous telescope. System equations are developed for a space tug which propels a 2500-kg scientific payload to 550 astronomical units in about 20 years. The tug to transport this payload uses electric propulsion with an Isp of 15,000 seconds and a fission reactor with a closed Brayton cycle to genemte the electricity. The optimal configuration may be to thrust for only about 6 years and then coast for the remaining 14 pars. This spacecraft does not require any physics breakthroughs or major advances in technology. The fission power syslem can be engineered and built by drawing upon known technologies developed for relatgd systems over the past 40 years. The tug system would eventually reach 1000 a.u in 33 years, and would have adequate power to relay large amounts of data throughout its journey.

  5. Fission fragment rockets: A potential breakthrough

    SciTech Connect

    Chapline, G.F.; Dickson, P.W.; Schnitzler, B.G.

    1988-01-01

    A new reactor concept which has the potential of enabling extremely energetic and ambitious space propulsion missions is described. Fission fragments are directly utilized as the propellant by guiding them out of a very low density core using magnetic fields. The very high fission fragment exhaust velocities yield specific impulses of approximately a million seconds while maintaining respectable thrust levels. Specific impulses of this magnitude allow acceleration of significant payload masses to several percent of the velocity of light and enable a variety of interesting missions, e.g., payloads to the nearest star, Alpha Centauri, in about a hundred years for very rapid solar system transport. The parameters reported in this paper are based on a very preliminary analysis. Considerable trade-off studies will be required to find the optimum system. We hope the optimum system proves to be as attractive as our preliminary analysis indicates, although we must admit that our limited effort is insufficient to guarantee any specific level of performance.

  6. Formation of asteroid pairs by rotational fission

    E-print Network

    Pravec, P; Polishook, D; Scheeres, D J; Harris, A W; Galad, A; Vaduvescu, O; Pozo, F; Barr, A; Longa, P; Vachier, F; Colas, F; Pray, D P; Pollock, J; Reichart, D; Ivarsen, K; Haislip, J; LaCluyze, A; Kusnirak, P; Henych, T; Marchis, F; Macomber, B; Jacobson, S A; Krugly, Yu N; Sergeev, A V; Leroy, A; 10.1038/nature09315

    2010-01-01

    Asteroid pairs sharing similar heliocentric orbits were found recently. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process4 may explain their formation - critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs revealing that primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissio...

  7. A fission-powered interstellar precursor mission

    SciTech Connect

    Lipinski, Ronald J.; Lenard, Roger X.; Wright, Steven A. West, John L.

    1999-01-01

    An {open_quotes}interstellar precursor mission{close_quotes} lays the groundwork for eventual interstellar exploration by studying the interstellar medium and by stretching technologies that have potential application for eventual interstellar exploration. The numerous scientific goals for such a mission include generating a 3-D stellar map of our galaxy, studying Kuiper-belt and Oort cloud objects, and observing distant objects using the sun{close_quote}s gravitational lens as the primary of an enormous telescope. System equations are developed for a space tug which propels a 2500-kg scientific payload to 550 astronomical units in about 20 years. The tug to transport this payload uses electric propulsion with an lsp of 15,000 seconds and a fission reactor with a closed Brayton cycle to generate the electricity. The optimal configuration may be to thrust for only about 6 years and then coast for the remaining 14 years. This spacecraft does not require any physics breakthroughs or major advances in technology. The fission power system can be engineered and built by drawing upon known technologies developed for related systems over the past 40 years. The tug system would eventually reach 1000 a.u in 33 years, and would have adequate power to relay large amounts of data throughout its journey. {copyright} {ital 1999 American Institute of Physics.}

  8. Brownian shape motion: Fission fragment mass distributions

    NASA Astrophysics Data System (ADS)

    Randrup, J.; Moller, P.

    2011-10-01

    Exploiting the expected strongly damped character of nuclear dynamics, we treat the nuclear shape evolution in analogy with Brownian motion and perform random walks on five-dimensional fission potential-energy surfaces which were calculated previously and are the most comprehensive available. Test applications give good reproduction of a selection of diverse experimental mass yields. This novel general approach requires only a single new global parameter, the critical neck size at which the mass partition is frozen in, and the results are remarkably insensitive to its specific value. A deeper understanding of these results can be achieved by including the friction tensor for the shape motion which appears to have only a minor effect on the resulting mass partition. Relative to previously employed models, the present approach represents a significant advance with regard to predictive power. It can be readily employed in regions of the nuclear chart that are of special astrophysical interest and it may, for example, help to clarify the importance of fission recycling for the r-process. Taking explicit account of the equilibration process, the treatment extends in a natural way the compound nucleus concept and it builds directly on the general picture of low-energy nuclear dynamics as being dissipation dominated. [PRL 106 (2011) 132503] DOE contracts AC02-05CH11231 (JR) AC52-06NA25396 (PM)

  9. Are seawater Sr/Ca variations preserved in Quaternary foraminifera?

    SciTech Connect

    Stoll, H.M.; Schrag, D.P.; Clemens, S.C.

    1999-11-01

    High precision measurements of Sr/Ca in planktonic foraminifera for the last 150 ka reveal Sr/Ca variations of up to 12% on glacial/interglacial time scales. Although records showing the largest variations appear to be strongly influenced by selective dissolution, other records show Sr/Ca variations of 3--5% that do not covary with indicators of dissolution intensity and that are reproduced in sites of contrasting Quaternary dissolution histories. These systematic variations are characterized by high Sr/Ca ratios during glacial maxima, followed by steep decreases during deglaciation and gradual increases through interstadial periods, closely following {delta}{sup 18}O curves. Foraminiferal Sr/Ca variations may reflect changes in the Sr/Ca ratio of seawater, or they may be due to kinetically or biologically induced changes in Sr partitioning. Coupled numerical models of the Sr and Ca budgets of the ocean reveal that sea level changes, together with large changes in river fluxes and carbonate accumulation rates, can produce seawater Sr/Ca variations that approximate both the shape and amplitude of foraminiferal Sr/Ca variations. However, such extreme changes in river and carbonate fluxes conflict with existing data on carbonate accumulation rates and Sr isotopic constraints on the magnitude of variations in the river flux. Smaller variations (1--3%) in the Sr/Ca ratio of seawater likely characterize Quaternary glacial cycles. Changes in Sr partitioning due to glacial-interglacial changes in the carbonate ion concentration and other environmental factors likely produce additional variation in the Sr/Ca record of planktonic foraminifera.

  10. Ceramic Hosts for Fission Products Immobilization

    SciTech Connect

    Peter C Kong

    2010-07-01

    Natural spinel, perovskite and zirconolite rank among the most leach resistant of mineral forms. They also have a strong affinity for a large number of other elements and including actinides. Specimens of natural perovskite and zirconolite were radioisotope dated and found to have survived at least 2 billion years of natural process while still remain their loading of uranium and thorium . Developers of the Synroc waste form recognized and exploited the capability of these minerals to securely immobilize TRU elements in high-level waste . However, the Synroc process requires a relatively uniform input and hot pressing equipment to produce the waste form. It is desirable to develop alternative approaches to fabricate these durable waste forms to immobilize the radioactive elements. One approach is using a high temperature process to synthesize these mineral host phases to incorporate the fission products in their crystalline structures. These mineral assemblages with immobilized fission products are then isolated in a durable high temperature glass for periods measured on a geologic time scale. This is a long term research concept and will begin with the laboratory synthesis of the pure spinel (MgAl2O4), perovskite (CaTiO3) and zirconolite (CaZrTi2O7) from their constituent oxides. High temperature furnace and/or thermal plasma will be used for the synthesis of these ceramic host phases. Nonradioactive strontium oxide will be doped into these ceramic phases to investigate the development of substitutional phases such as Mg1-xSrxAl2O4, Ca1-xSrxTiO3 and Ca1-xSrxZrTi2O7. X-ray diffraction will be used to establish the crystalline structures of the pure ceramic hosts and the substitution phases. Scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX) will be performed for product morphology and fission product surrogates distribution in the crystalline hosts. The range of strontium doping is planned to reach the full substitution of the divalent metal ions, Mg and Ca, in the ceramic host phases. The immobilization of rear earth (lanthanide series) fission products in these ceramic host phases will also be studied this year. Cerium oxide is chosen to represent the rear earth fission product for substitution studies in spinel, perovskite and zirconolite ceramic hosts. Cerium has +3 and +4 oxidation states and it can replace some of the trivalent or tetravalent host ions to produce the substitution ceramics such as MgAl2-xCexO4, CaTi1-xCexO3, CaZr1-xCexTi2O7 and CaZrTi2-xCexO7. X-ray diffraction analysis will be used to compare the crystalline structures of the pure ceramic hosts and the substitution phases. SEM-EDX analysis will be used to study the Ce distribution in the ceramic host phases. The range of cerium doping is planned to reach the full substitution of the trivalent or tetravalent ions, Al, Ti and Zr, in the ceramic host phases.

  11. Applications of Event-by-Event Fission Modeling with FREYA

    SciTech Connect

    Vogt, R; Randrup, J

    2011-09-16

    The recently developed code FREYA (Fission Reaction Event Yield Algorithm) generates large samples of complete fission events, consisting of two receding product nuclei as well as a number of neutrons and photons, all with complete kinematic information. Thus it is possible to calculate arbitrary correlation observables whose behavior may provide unique insight into the fission process. We first discuss the present status of FREYA, which has now been extended to include spontaneous fission. Concentrating on {sup 239}Pu(n{sub th},f), {sup 240}Pu(sf) and {sup 252}Cf(sf), we discuss the neutron multiplicity correlations, the dependence of the neutron energy spectrum on the neutron multiplicity, and the relationship between the fragment kinetic energy and the number of neutrons and their energies. We also suggest novel fission observables that could be measured with modern detectors.

  12. Angular momentum effects in multimodal fission of {sup 226}Th

    SciTech Connect

    Chubarian, G.G.; Hurst, B.J.; OKelly, D.; Schmitt, R.P.; Itkis, M.G.; Kondratiev, N.A.; Kozulin, E.M.; Oganessian, Y.T.; Pashkevich, V.V.; Pokrovsky, I.V.; Salamatin, V.S.; Rusanov, A.Y.; Calabretta, L.; Maiolino, C.; Lukashin, K.; Agodi, C.; Bellia, G.; Hanappe, F.; Liatard, E.; Huck, A.; Stuttge, L.

    1998-12-01

    The {gamma}-rays from the multimodal fission of the {sup 226}Th formed in {sup 18}O+{sup 208}Pb was investigated at the near- and sub-barrier energies. The corresponding excitation energies at the saddle point, E{sub sp}{sup {asterisk}}, ranged from 23 to 26 MeV. The average {gamma}-ray multiplicities and relative {gamma}-ray energies as a function of the mass of the fission fragments exhibits a complex structure and strong variations. Such strong variations have never been previously observed in heavy ion-induced fusion-fission reactions. Obtained results may be explained with the influence of shell effects on the properties of the fission fragments. Present work is the one in series of investigation of the multimodal fission phenomena in At-Th region. {copyright} {ital 1998 American Institute of Physics.}

  13. Neutron capture and fission in /sup 254g/ Es

    SciTech Connect

    Halperin, J.; Bigelow, J.E.; O'Kelley, G.D.; Oliver, J.H.; Wiggins, J.T.

    1985-07-01

    Integral neutron capture and neutron fission cross sections have been measured for the 276-day /sup 254g/ Es. Thermal cross sections and resonance integrals were evaluated using a cadmium filter technique. Capture cross sections were determined from alpha-particle spectrum measurements following neutron irradiations with cobalt flux monitors. Fission cross sections were measured using fission track detection techniques with STTU monitors. The fission cross-section values compared favorably with an absorption cross-section determination from a burnout experiment of SVTEs-SVUEs. The integral neutron capture and fission cross sections determined for /sup 254g/ Es are: sigma /sub c/ /sup th/ = 28.3 + or - 2.5 and I /sub c/ = 18.2 + or - 1.5 b, and sigma /sub F/ /sup th/ = 1970 + or - 200 and I /sub F/ = 1200 + or - 250 b.

  14. Angular momentum effects in multimodal fission of {sup 226}Th

    SciTech Connect

    Chubarian, G. G.; Hurst, B. J.; O'Kelly, D.; Schmitt, R. P.; Itkis, M. G.; Kondratiev, N. A.; Kozulin, E. M.; Oganessian, Yu. Ts.; Pashkevich, V. V.; Pokrovsky, I. V.; Salamatin, V. S.; Rusanov, A. Ya.; Calabretta, L.; Maiolino, C.; Lukashin, K.; Agodi, C.; Bellia, G.; Hanappe, F.; Liatard, E.; Huck, A.

    1998-12-21

    The {gamma}-rays from the multimodal fission of the {sup 226}Th formed in {sup 18}O+{sup 208}Pb was investigated at the near- and sub-barrier energies. The corresponding excitation energies at the saddle point, E{sub sp}*, ranged from 23 to 26 MeV. The average {gamma}-ray multiplicities and relative {gamma}-ray energies as a function of the mass of the fission fragments exhibits a complex structure and strong variations. Such strong variations have never been previously observed in heavy ion-induced fusion-fission reactions. Obtained results may be explained with the influence of shell effects on the properties of the fission fragments. Present work is the one in series of investigation of the multimodal fission phenomena in At-Th region.

  15. A twin ionization chamber for fission fragment detection

    NASA Astrophysics Data System (ADS)

    Budtz-Jørgensen, C.; Knitter, H.-H.; Straede, Ch.; Hambsch, F.-J.; Vogt, R.

    1987-08-01

    A twin ionization chamber for fission fragment detection is described. The detector permits measurement of the two fission fragment kinetic energies in an advantageous 2×2 ? geometry with an energy resolution of <0.5 MeV. The fission fragment emission angle ? with respect to the symmetry axis of the chamber is measured with a resolution in cos ? of <0.05. The fission fragment nuclear charge distributions can be determined and a timing signal can be extracted which allows a determination of the instant of fission with a time jitter of <0.7 ns. A pulse pileup rejection technique was developed which reduces pulse pileup by more than a factor 30. The electronic treatment of the chamber pulses and the data handling procedures including several of the necessary corrections are described in detail.

  16. First fission mass yield measurements using SPIDER at LANSCE

    NASA Astrophysics Data System (ADS)

    Meierbachtol, Krista; Tovesson, Fredrik; Arnold, Charles; Devlin, Matt; Bredeweg, Todd; Jandel, Marian; Jorgenson, Justin; Nelson, Ron; White, Morgan; Shields, Dan; Blakeley, Rick; Hecht, Adam

    2014-09-01

    Robust measurements of fission product properties, including mass yields, are important for advancing our understanding of the complex fission process and as improved inputs to calculation and simulation efforts in nuclear applications. The SPIDER detector, located at the Los Alamos Neutron Science Center (LANSCE), is a recently developed mass spectrometer aimed at measuring fission product mass yields with high resolution as a function of incident neutron energy and product mass, charge, and kinetic energy. The prototype SPIDER detector has been assembled, tested, installed at the Lujan Center at LANSCE, and taken initial thermal neutron induced measurements. The first results of mass yields for spontaneous fission of 252Cf and thermal neutron-induced fission of 235U measured with SPIDER will be presented. Ongoing upgrades and future plans for SPIDER will also be discussed. This work is in part supported by LANL Laboratory Directed Research and Development Projects 20110037DR and 20120077DR. LA-UR-14-24830.

  17. Fission matrix capability for MCNP, Part II - Applications

    SciTech Connect

    Carney, S. E.; Brown, F. B.; Kiedrowski, B. C.; Martin, W. R.

    2013-07-01

    This paper describes the initial experience and results from implementing a fission matrix capability into the MCNP Monte Carlo code. The fission matrix is obtained at essentially no cost during the normal simulation for criticality calculations. It can be used to provide estimates of the fundamental mode power distribution, the reactor dominance ratio, the eigenvalue spectrum, and higher mode spatial eigenfunctions. It can also be used to accelerate the convergence of the power method iterations. Past difficulties and limitations of the fission matrix approach are overcome with a new sparse representation of the matrix, permitting much larger and more accurate fission matrix representations. Numerous examples are presented. A companion paper (Part I - Theory) describes the theoretical basis for the fission matrix method. (authors)

  18. Characterization of the scission point from fission-fragment velocities

    E-print Network

    M. Caamaño; F. Farget; O. Delaune; K. -H. Schmidt; C. Schmitt; L. Audouin; C. -O. Bacri; J. Benlliure; E. Casarejos; X. Derkx; B. Fernández-Domínguez; L. Gaudefroy; C. Golabek; B. Jurado; A. Lemasson; D. Ramos; C. Rodríguez-Tajes; T. Roger; A. Shrivastava

    2015-07-15

    The isotopic-yield distributions and kinematic properties of fragments produced in transfer-induced fission of 240Pu and fusion-induced fission of 250Cf, with 9 MeV and 45 MeV of excitation energy respectively, were measured in inverse kinematics with the spectrometer VAMOS. The kinematic properties of identified fission fragments allow to derive properties of the scission configuration such as the distance between fragments, the total kinetic energy, the neutron multiplicity, the total excitation energy, and, for the first time, the proton- and neutron-number sharing during the emergence of the fragments. These properties of the scission point are studied as functions of the fragment atomic number. The correlation between these observables, gathered in one single experiment and for two different fissioning systems at different excitation energies, give valuable information for the understanding and modeling of the fission process.

  19. Improved Fission Neutron Data Base for Active Interrogation of Actinides

    SciTech Connect

    Pozzi, Sara; Czirr, J. Bart; Haight, Robert; Kovash, Michael; Tsvetkov, Pavel

    2013-11-06

    This project will develop an innovative neutron detection system for active interrogation measurements. Many active interrogation methods to detect fissionable material are based on the detection of neutrons from fission induced by fast neutrons or high-energy gamma rays. The energy spectrum of the fission neutrons provides data to identify the fissionable isotopes and materials such as shielding between the fissionable material and the detector. The proposed path for the project is as follows. First, the team will develop new neutron detection systems and algorithms by Monte Carlo simulations and bench-top experiments. Next, They will characterize and calibrate detection systems both with monoenergetic and white neutron sources. Finally, high-fidelity measurements of neutron emission from fissions induced by fast neutrons will be performed. Several existing fission chambers containing U-235, Pu-239, U-238, or Th-232 will be used to measure the neutron-induced fission neutron emission spectra. The challenge for making confident measurements is the detection of neutrons in the energy ranges of 0.01 – 1 MeV and above 8 MeV, regions where the basic data on the neutron energy spectrum emitted from fission is least well known. In addition, improvements in the specificity of neutron detectors are required throughout the complete energy range: they must be able to clearly distinguish neutrons from other radiations, in particular gamma rays and cosmic rays. The team believes that all of these challenges can be addressed successfully with emerging technologies under development by this collaboration. In particular, the collaboration will address the area of fission neutron emission spectra for isotopes of interest in the advanced fuel cycle initiative (AFCI).

  20. Seismic stratigraphy and quaternary evolution of the New York Bight Inner Continental Shelf 

    E-print Network

    Lotto, Linda L

    2000-01-01

    over the New York Bight Apex on the U. S. Atlantic inner continental shelf were analyzed to develop a better understanding of the Quaternary evolution of this inner continental shelf environment. Interpretation of the subbottom data reveals several...

  1. Induction of contact drematitis in guinea pigs by quaternary ammonium compounds: the mechanisms of antigen formation

    SciTech Connect

    Schallreuter, K.R.; Schulz, K.H.; Wood, J.M.

    1986-12-01

    Eight quaternary ammonium compounds were tested for their ability to induce contact dermatitis in guinea pigs by using a modified Freund's complete adjuvant test together with the guinea pig maximization test. Only two quaternary ammonium salts of eight tested could be designated as strong allergens. These two active substances were shown to be capable of stable association with membrane lipids in forming immunogenic complexes. This surface complexation phenomenon was confirmed by using a spin-labeled quaternary ammonium salt which competed for binding sites to the surface of epidermal cells in vivo. Electron spin resonance was used to demonstrate that stable ion-pairs are formed between binding sites and the two allergenic preservatives. Furthermore, information was obtained on the kinetics of immunogenic complex formation as well as on the position and orientation of the quaternary ammonium ion at the cell surface.

  2. OMVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics (title change from A)

    SciTech Connect

    HAN,JUNG; FIGIEL,JEFFREY J.; PETERSEN,GARY A.; MYERS JR.,SAMUEL M.; CRAWFORD,MARY H.; BANAS,MICHAEL ANTHONY; HEARNE,SEAN JOSEPH

    2000-01-18

    We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GrdnN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.

  3. Metalorganic Vapor-Phase Epitaxial Growth and Characterization of Quaternary AlGaInN

    SciTech Connect

    BANAS, MICHAEL ANTHONY; CRAWFORD, MARY H.; FIGIEL, JEFFREY J.; HAN, JUNG; LEE, STEPHEN R.; MYERS JR., SAMUEL M.; PETERSON, GARY D.

    1999-09-27

    In this letter we report the growth (by MOVPE) and characterization of quaternary AlGaInN. A combination of PL, high-resolution XRD, and RBS characterizations enables us to explore and delineate the contours of equil-emission energy and lattice parameters as functions of the quaternary compositions. The observation of room temperature PL emission as short as 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GdnN MQW heterostructures have also been grown; both x-ray diffraction and PL measurement suggest the possibility of incorporating this quaternary into optoelectronic devices.

  4. INTRODUCTION For much of the past century, the Quaternary record of the

    E-print Network

    Pederson, Joel L.

    the Pleistocene glaciations. Second, the unique Geological Society of America Field Guide 6 2005 From cirques.L., and Carson, E.C., 2005, From cirques to canyon cutting: New Quaternary research in the Uinta Mountains

  5. Quaternary volcano-lacustrine patterns and palaeobotanical data in southern Armenia

    E-print Network

    Utrecht, Universiteit

    imprints, pollen, insects and mammal bones) are related to major volcanic activity, basaltic flows and tectono-orogenic movements that occurred during the Quaternary period. The recent discovery of indicators

  6. Species-specific responses of Late Quaternary megafauna to climate and humans

    E-print Network

    Lorenzen, Eline D.; Nogué s-Bravo, David; Orlando, Ludovic; Weinstock, Jaco; Binladen, Jonas; Marske, Katharine A.; Ugan, Andrew; Borregaard, Michael K.; Gilbert, M. Thomas P.; Nielsen, Rasmus; Ho, Simon Y.W.; Goegel, Ted; Graf, Kelly E.; Byers, David; Stenderup, Jesper T.; Rasmussen, Morten; Campos, Paula F.; Leonard, Jennifer A.; Koepfli, Klaus-Peter; Froese, Duane; Zazula, Grant; Stafford, Thomas W. Jr.; Aaris-Sø rensen, Kim; Batra, Persaram; Haywood, Alan M.; Singarayer, Joy S.; Valdes, Paul J.; Boeskorov, Gennady; Burns, James A.; Davydov, Sergey P.; Haile, James; Jenkins, Dennis L.; Kosintsev, Pavel; Kuznetsova, Tatyana; Lai, Xulong; Martin, Larry D.; McDonald, H. Gregory; Mol, Dick; Meldgaard, Morten; Munch, Kasper; Stephan, Elisabeth; Sablin, Mikhail; Sommer, Robert S.; Sipko, Taras; Scott, Eric; Suchard, Marc A.; Tikhonov, Alexei; Willerslev, Rane; Wayne, Robert K.; Cooper, Alan; Hofreiter, Michael; Sher, Andrei; Shapiro, Beth; Rahbek, Carsten; Willerslev, Eske

    2014-11-17

    Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary remain contentious. We use ancient DNA, species distribution models and the human fossil record...

  7. Quaternary geologic and geomorphic framework for neotectonic analysis of the northeastern Franklin Mountains, El Paso, Texas 

    E-print Network

    Scherschel, Craig A.

    1995-01-01

    The Quaternary geology and geomorphology of a 45 km2 area along the northeastern Franklin Mountains near El Paso, Texas was characterized as part of a paleoseismic evaluation of the East Franklin Mountains fault. The East Franklin Mountains fault...

  8. Diatom-based Late Quaternary precipitation record for lowland tropical South America 

    E-print Network

    Fitzpatrick, Katharine Anne

    2012-06-25

    The late Quaternary palaeoclimatic history of the lowland Southern Hemisphere Tropics of South America (SHTSA) has been little studied and analysis of key climatic events, such as the Last Glacial Maximum (centred ~ ...

  9. A method to measure prompt fission neutron spectrum using gamma multiplicity tagging

    NASA Astrophysics Data System (ADS)

    Blain, E.; Daskalakis, A.; Block, R. C.; Barry, D.; Danon, Y.

    2016-01-01

    In order to improve on current prompt fission neutron spectrum measurements, a gamma multiplicity tagging method was developed at the Rensselaer Polytechnic Institute Gearttner Linear Accelerator Center. This method involves using a coincidence requirement on an array of BaF2 gamma detectors to determine the timing of a fission event. This allows for much larger fission samples to be used due to the higher penetrability of gammas compared to fission fragments. Additionally, since the method relies on gammas as opposed to fission fragments, the effects of the low level discriminator, used in fission chambers to eliminate alpha events, are not seen. A 252Cf fission chamber was constructed in order to determine the viability of this method as well as the efficiency when compared to a fission chamber. The implemented multiple gamma tagging method was found to accurately reproduce the prompt fission neutron spectrum for the spontaneous fission of 252Cf and to detect 30% of fission events.

  10. Fission Product Yield Study of 235U, 238U and 239Pu Using Dual-Fission Ionization Chambers

    NASA Astrophysics Data System (ADS)

    Bhatia, C.; Fallin, B.; Howell, C.; Tornow, W.; Gooden, M.; Kelley, J.; Arnold, C.; Bond, E.; Bredeweg, T.; Fowler, M.; Moody, W.; Rundberg, R.; Rusev, G.; Vieira, D.; Wilhelmy, J.; Becker, J.; Macri, R.; Ryan, C.; Sheets, S.; Stoyer, M.; Tonchev, A.

    2014-05-01

    To resolve long-standing differences between LANL and LLNL regarding the correct fission basis for analysis of nuclear test data [M.B. Chadwick et al., Nucl. Data Sheets 111, 2891 (2010); H. Selby et al., Nucl. Data Sheets 111, 2891 (2010)], a collaboration between TUNL/LANL/LLNL has been established to perform high-precision measurements of neutron induced fission product yields. The main goal is to make a definitive statement about the energy dependence of the fission yields to an accuracy better than 2-3% between 1 and 15 MeV, where experimental data are very scarce. At TUNL, we have completed the design, fabrication and testing of three dual-fission chambers dedicated to 235U, 238U, and 239Pu. The dual-fission chambers were used to make measurements of the fission product activity relative to the total fission rate, as well as for high-precision absolute fission yield measurements. The activation method was employed, utilizing the mono-energetic neutron beams available at TUNL. Neutrons of 4.6, 9.0, and 14.5 MeV were produced via the 2H(d,n)3He reaction, and for neutrons at 14.8 MeV, the 3H(d,n)4He reaction was used. After activation, the induced ?-ray activity of the fission products was measured for two months using high-resolution HPGe detectors in a low-background environment. Results for the yield of seven fission fragments of 235U, 238U, and 239Pu and a comparison to available data at other energies are reported. For the first time results are available for neutron energies between 2 and 14 MeV.

  11. Results of interlaboratory comparison of fission track ages for 1992 fission track workshop

    USGS Publications Warehouse

    Miller, D.S.; Crowley, K.D.; Dokka, R.K.; Galbraith, R.F.; Kowallis, B.J.; Naeser, C.W.

    1993-01-01

    Two apatites and one sphene were made available to the fission track research community for analysis prior to the 1992 Fission Track Workshop held in Philadelphia, U.S.A., 13-17 July. Eighteen laboratories throughout the world received aliquots of apatite and sphene. To date, analyses by 33 different scientists have been representing 15 different laboratories. With respect to the previous two interlaboratory comparisons, there is a noticeable improvement in the accuracy of the age results (Naeser and Cebula, 1978; Naeser et al., 1981; Miller et al., 1985;Miller et al.1990). Ninety-four percent of the analysis used the external detector method (EDM) combined with the zeta technique while the remaining individuals used the population method (POP). Track length measurements (requested for the first time in the interlaboratory comparison studies) were in relatively good agreement. ?? 1993.

  12. Control system for a small fission reactor

    DOEpatents

    Burelbach, J.P.; Kann, W.J.; Saiveau, J.G.

    1985-02-08

    A system for controlling the reactivity of a small fission reactor includes an elongated, flexible hollow tube in the general form of a helical coiled spring axially positioned around and outside of the reactor vessel in an annular space between the reactor vessel and a surrounding cylindrical-shaped neutron reflector. A neutron absorbing material is provided within the hollow tube with the rate of the reaction controlled by the extension and compression of the hollow tube, e.g., extension of the tube increases reactivity while its compression reduces reactivity, in varying the amount of neutron absorbing material disposed between the reactor vessel and the neutron reflector. Conventional mechanical displacement means may be employed to control the coil density of the hollow tube as desired.

  13. (Fuel, fission product, and graphite technology)

    SciTech Connect

    Stansfield, O.M.

    1990-07-25

    Travel to the Forschungszentrum (KFA) -- Juelich described in this report was for the purpose of participating in the annual meeting of subprogram managers for the US/DOE Umbrella Agreement for Fuel, Fission Product, and Graphite Technology. At this meeting the highlights of the cooperative exchange were reviewed for the time period June 1989 through June 1990. The program continues to contribute technology in an effective way for both countries. Revision 15 of the Subprogram Plan will be issued as a result of the meeting. There was interest expressed by KFA management in the level of support received from the NPR program and in potential participation in the COMEDIE loop experiment being conducted at the CEA.

  14. Budding and Fission of a multiphase vesicle

    E-print Network

    Jean-Marc Allain; Martine Ben Amar

    2005-04-08

    We present a model of bi-phasic vesicle in the limit of large surface tension. In this regime, the vesicle is completely stretched and well described by two spherical caps with a fold which concentrates the membrane stress. The conservation laws and geometric constraints restrict the space of possible shapes to a pair of solutions labeled by a parameter $\\tau$ given by {\\it line tension/pressure}. For a given $\\tau$ value, the two solutions differ by the length of the interface between domains. For a critical value $\\tau\\_c$, the two vesicle shapes become identical and no solution exists above this critical value. This model sheds new light on two proposed mechanisms (osmotic shocks and molecule absorption) to explain the budding and the fission in recent experiments.

  15. Detecting fission from special nuclear material sources

    DOEpatents

    Rowland, Mark S. (Alamo, CA); Snyderman, Neal J. (Berkeley, CA)

    2012-06-05

    A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. The system includes a graphing component that displays the plot of the neutron distribution from the unknown source over a Poisson distribution and a plot of neutrons due to background or environmental sources. The system further includes a known neutron source placed in proximity to the unknown source to actively interrogate the unknown source in order to accentuate differences in neutron emission from the unknown source from Poisson distributions and/or environmental sources.

  16. Large-scale fission product containment tests

    NASA Astrophysics Data System (ADS)

    Hilliard, R. K.; Postma, A. K.

    1980-11-01

    The Containment Systems Experiment (CSE) program is reviewed, with emphasis on the inherent processes that remove fission products from containment atmospheres and reduce their leakage to the environment. The CSE containment vessel was sized to represent a 1/5 linear scale model of a typical 1000 MW(e) PWR. Nineteen tests were performed in a stream-air atmosphere simulating post-LOCA conditions. In eight tests containment sprays were operated, in five tests a recirculating filter-adsorber loop was operated, and in six tests only natural, passive processes occurred. Sprays were the most effective in removing airborne iodine and particulate aerosols, followed by the filter loop. Although not as effective as the engineered safety features, natural processes of diffusion to surfaces, reaction with paint, gravity settling, and removal in leak paths are shown to be significant.

  17. Nuclear fission and the transuranium elements

    SciTech Connect

    Seaborg, G.T.

    1989-02-01

    Many of the transuranium elements are produced and isolated in large quantities through the use of neutrons furnished by nuclear fission reactions: plutonium (atomic number 94) in ton quantities; neptunium (93), americium (95), and curium (96) in kilogram quantities; berkelium (97) in 100 milligram quantities; californium (98) in gram quantities; and einsteinium (99) in milligram quantities. Transuranium isotopes have found many practical applications---as nuclear fuel for the large-scale generation of electricity, as compact, long-lived power sources for use in space exploration, as means for diagnosis and treatment in the medical area, and as tools in numerous industrial processes. Of particular interest is the unusual chemistry and impact of these heaviest elements on the periodic table. This account will feature these aspects. 9 refs., 5 figs.

  18. Results of interlaboratory comparison of fission-track age standards: Fission-track workshop-1984

    USGS Publications Warehouse

    Miller, D.S.; Duddy, I.R.; Green, P.F.; Hurford, A.J.; Naeser, C.W.

    1985-01-01

    Five samples were made available as standards for the 1984 Fission Track Workshop held in the summer of 1984 (Rensselaer Polytechnic Institute, Troy, New York). Two zircons, two apatites and a sphene were distributed prior to the meeting to 40 different laboratories. To date, 24 different analysts have reported results. The isotopic ages of the standards ranged from 16.8 to 98.7 Myr. Only the statement that the age of each sample was less than 200 Myr was provided with the set of standards distributed. Consequently, each laboratory was required to use their laboratory's accepted treatment (irradiation level, etching conditions, counting conditions, etc.) for these samples. The results show that some workers have serious problems in achieving accurate age determinations. This emphasizes the need to calibrate experimental techniques and counting procedures against age standards before unknown ages are determined. Any fission-track age determination published or submitted for publication can only be considered reliable if it is supported by evidence of consistent determinations on age standards. Only this can provide the scientific community with the background to build up confidence concerning the validity of the fission-track method. ?? 1985.

  19. Multiple-Coincidence Active Neutron Interrogation of Fissionable Materials

    SciTech Connect

    Tinsley, J.R., Hurley, J.P., Trainham, R., Keegan, R.P.

    2008-11-14

    In an extension of the Associated Particle Imaging technique that is used for the detection and imaging of hidden explosives, the present measurements use a beam of tagged 14.1 MeV neutrons in coincidence with two or more gammas to probe for the presence of fissionable materials. We have measured neutron-gamma-gamma coincidences with targets of depleted uranium, tungsten, lead, iron, and carbon and will present results that show the multiple-coincidence counting rate for the depleted uranium is substantially higher than any of the non-fissionable materials. In addition, the presence of coincidences involving delayed particle spectra provides a signature for fissionable materials that is distinct from that for non-fissionable ones. Information from the tagged neutron involved in the coincidence event is used to compute the position of the fissionable material in all three dimensions. The result is an imaging probe for fissionable materials that is compact and portable, and produces relatively low levels of background radiation. Simultaneous measurements on packages of interest for both explosives and fissionable materials are now feasible.

  20. Modelling Animal Group Fission Using Social Network Dynamics

    PubMed Central

    Sueur, Cédric; Maire, Anaïs

    2014-01-01

    Group life involves both advantages and disadvantages, meaning that individuals have to compromise between their nutritional needs and their social links. When a compromise is impossible, the group splits in order to reduce conflict of interests and favour positive social interactions between its members. In this study we built a dynamic model of social networks to represent a succession of temporary fissions involving a change in social relations that could potentially lead to irreversible group fission (i.e. no more group fusion). This is the first study that assesses how a social network changes according to group fission-fusion dynamics. We built a model that was based on different parameters: the group size, the influence of nutritional needs compared to social needs, and the changes in the social network after a temporary fission. The results obtained from this theoretical data indicate how the percentage of social relation transfer, the number of individuals and the relative importance of nutritional requirements and social links influence the average number of days before irreversible fission occurs. The greater the nutritional needs and the higher the transfer of social relations during temporary fission, the fewer days will be observed before an irreversible fission. It is crucial to bridge the gap between the individual and the population level if we hope to understand how simple, local interactions may drive ecological systems. PMID:24831471

  1. Single Particle Fluorescence Burst Analysis of Epsin Induced Membrane Fission

    PubMed Central

    Kustigian, Lauren; Puchalla, Jason; Carr, Chavela M.; Rye, Hays S.

    2015-01-01

    Vital cellular processes, from cell growth to synaptic transmission, rely on membrane-bounded carriers and vesicles to transport molecular cargo to and from specific intracellular compartments throughout the cell. Compartment-specific proteins are required for the final step, membrane fission, which releases the transport carrier from the intracellular compartment. The role of fission proteins, especially at intracellular locations and in non-neuronal cells, while informed by the dynamin-1 paradigm, remains to be resolved. In this study, we introduce a highly sensitive approach for the identification and analysis of membrane fission machinery, called burst analysis spectroscopy (BAS). BAS is a single particle, free-solution approach, well suited for quantitative measurements of membrane dynamics. Here, we use BAS to analyze membrane fission induced by the potent, fission-active ENTH domain of epsin. Using this method, we obtained temperature-dependent, time-resolved measurements of liposome size and concentration changes, even at sub-micromolar concentration of the epsin ENTH domain. We also uncovered, at 37°C, fission activity for the full-length epsin protein, supporting the argument that the membrane-fission activity observed with the ENTH domain represents a native function of the full-length epsin protein. PMID:25799353

  2. A New Method of Prompt Fission Neutron Energy Spectrum Unfolding

    SciTech Connect

    Zeynalova, O. V.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.

    2010-11-25

    The prompt neutron emission in spontaneous fission of {sup 252}Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. The goal was to find out the reasons of a long time existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of fission fragments (FF). On the one hand the {sup 252}Cf(sf) reaction is one of the main references for nuclear data, on the other hand the understanding of PFN emission mechanism is very important for nuclear fission theory. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 10{sup 7} fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.

  3. Compilation of fission product yields Vallecitos Nuclear Center

    SciTech Connect

    Rider, B.F.

    1980-01-01

    This document is the ninth in a series of compilations of fission yield data made at Vallecitos Nuclear Center in which fission yield measurements reported in the open literature and calculated charge distributions have been utilized to produce a recommended set of yields for the known fission products. The original data with reference sources, as well as the recommended yields are presented in tabular form for the fissionable nuclides U-235, Pu-239, Pu-241, and U-233 at thermal neutron energies; for U-235, U-238, Pu-239, and Th-232 at fission spectrum energies; and U-235 and U-238 at 14 MeV. In addition, U-233, U-236, Pu-240, Pu-241, Pu-242, Np-237 at fission spectrum energies; U-233, Pu-239, Th-232 at 14 MeV and Cf-252 spontaneous fission are similarly treated. For 1979 U234F, U237F, Pu249H, U234He, U236He, Pu238F, Am241F, Am243F, Np238F, and Cm242F yields were evaluated. In 1980, Th227T, Th229T, Pa231F, Am241T, Am241H, Am242Mt, Cm245T, Cf249T, Cf251T, and Es254T are also evaluated.

  4. Prompt fission neutron spectra and average prompt neutron multiplicities

    SciTech Connect

    Madland, D.G.; Nix, J.R.

    1983-01-01

    We present a new method for calculating the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity anti nu/sub p/ as functions of the fissioning nucleus and its excitation energy. The method is based on standard nuclear evaporation theory and takes into account (1) the motion of the fission fragments, (2) the distribution of fission-fragment residual nuclear temperature, (3) the energy dependence of the cross section sigma/sub c/ for the inverse process of compound-nucleus formation, and (4) the possibility of multiple-chance fission. We use a triangular distribution in residual nuclear temperature based on the Fermi-gas model. This leads to closed expressions for N(E) and anti nu/sub p/ when sigma/sub c/ is assumed constant and readily computed quadratures when the energy dependence of sigma/sub c/ is determined from an optical model. Neutron spectra and average multiplicities calculated with an energy-dependent cross section agree well with experimental data for the neutron-induced fission of /sup 235/U and the spontaneous fission of /sup 252/Cf. For the latter case, there are some significant inconsistencies between the experimental spectra that need to be resolved. 29 references.

  5. Fission-product SiC reaction in HTGR fuel

    SciTech Connect

    Montgomery, F.

    1981-07-13

    The primary barrier to release of fission product from any of the fuel types into the primary circuit of the HTGR are the coatings on the fuel particles. Both pyrolytic carbon and silicon carbide coatings are very effective in retaining fission gases under normal operating conditions. One of the possible performance limitations which has been observed in irradiation tests of TRISO fuel is chemical interaction of the SiC layer with fission products. This reaction reduces the thickness of the SiC layer in TRISO particles and can lead to release of fission products from the particles if the SiC layer is completely penetrated. The experimental section of this report describes the results of work at General Atomic concerning the reaction of fission products with silicon carbide. The discussion section describes data obtained by various laboratories and includes (1) a description of the fission products which have been found to react with SiC; (2) a description of the kinetics of silicon carbide thinning caused by fission product reaction during out-of-pile thermal gradient heating and the application of these kinetics to in-pile irradiation; and (3) a comparison of silicon carbide thinning in LEU and HEU fuels.

  6. Angular distribution in the neutron-induced fission of actinides

    NASA Astrophysics Data System (ADS)

    Leong, L. S.; Tassan-Got, L.; Tarrio, D.; Audouin, L.; Paradela, C.; Duran, I.; Le Naour, C.; Altstadt, S.; Andrzejewsky, J.; Barbagallo, M.; Bécares, V.; Be?vá?, F.; Belloni, F.; Berthoumieux, E.; Billowes, J.; Boccone, V.; Bosnar, D.; Brugger, M.; Calvino, F.; Calviani, M.; Cano-Ott, D.; Carrapiço, C.; Cerutti, F.; Chiaveri, E.; Chin, M.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dzysiuk, N.; Eleftheriadis, C.; Ferrari, A.; Fraval, K.; Ganesan, S.; García, A. R.; Giubrone, G.; Gómez-Hornillos, M. B.; Gonçalves, I. F.; González-Romero; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Gurusamy, P.; Jenkins, D. G.; Jericha, E.; Kadi, E.; Käppeler, F.; Karadimos, D.; Kivel, N.; Koehler, P.; Kokkoris, M.; Korschinek, G.; Kroll, J.; Krti?ka, M.; Langer, C.; Lederer, C.; Leeb, H.; Losito, R.; Manousos, A.; Marganiec, J.; Massimi, C.; Martínez, T.; Mastinu, P. F.; Mastromarco, M.; Meaze, M.; Mengon, A.; Mendoza, E.; Milazzo, P. M.; Mingrone, T.; Mirea, M.; Mondelaers, W.; Pavlik, A.; Perkowski, J.; Pignatari, M.; Plompen, A.; Praena, J.; Quesada, J. M.; Rauscher, T.; Reifhart, R.; Riego, A.; Roman, F.; Rubbia, C.; Sarmento, R.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Taín, J. L.; Tagliente, G.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Versaci, R.; Vermeulen, M. J.; Vlachoudis, V.; Vlastou, V.; Wallner, A.; Ware, T.; Weigand, M.; Weiß, C.; Wright, T.; Z?gec

    2013-12-01

    Above 1 MeV of incident neutron energy the fission fragment angular distribution (FFAD) has generally a strong anisotropic behavior due to the combination of the incident orbital momentum and the intrinsic spin of the fissioning nucleus. This effect has to be taken into account for the efficiency estimation of devices used for fission cross section measurements. In addition it bears information on the spin deposition mechanism and on the structure of transitional states. We designed and constructed a detection device, based on Parallel Plate Avalanche Counters (PPAC), for measuring the fission fragment angular distributions of several isotopes, in particular 232Th. The measurement has been performed at n_TOF at CERN taking advantage of the very broad energy spectrum of the neutron beam. Fission events were recognized by back to back detection in coincidence in two position-sensitive detectors surrounding the targets. The detection efficiency, depending mostly on the stopping of fission fragments in backings and electrodes, has been computed with a Geant4 simulation and validated by the comparison to the measured case of 235U below 3 keV where the emission is isotropic. In the case of 232Th, the result is in good agreement with previous data below 10 MeV, with a good reproduction of the structures associated to vibrational states and the opening of second chance fission. In the 14 MeV region our data are much more accurate than previous ones which are broadly scattered.

  7. Nuclear fission of neutron-deficient protactinium nuclides

    SciTech Connect

    Nishinaka, I.; Nagame, Y.; Tsukada, K.; Ikezoe, H.; Sueki, K.; Nakahara, H.; Tanikawa, M.; Ohtsuki, T.

    1997-08-01

    Fragment velocity, kinetic energy, mass yield, and element yield distributions in the fission of neutron-deficient Pa isotopes produced in the reactions of {sup 16}O and {sup 18}O on {sup 209}Bi have been measured at incident beam energies near and above the Coulomb barriers by the time-of-flight and radiochemical methods. An asymmetric mass-division component has been observed. Measured fission cross sections were compared with the results of statistical model calculations which take into account two fission barrier heights for symmetric and asymmetric yields. The fission barrier height deduced for the asymmetric fission is found slightly lower than that for the symmetric one. The difference between the two barrier heights in the fission of the present protactinium nuclides (N{approximately}135) is considerably smaller than that in the neutron-rich nuclide of {sup 233}Pa (N{approximately}142), indicating that the difference sensitively depends on the neutron number of the fissioning nuclide. {copyright} {ital 1997} {ital The American Physical Society}

  8. Constraining the level density using fission of lead projectiles

    NASA Astrophysics Data System (ADS)

    Rodríguez-Sánchez, J. L.; Benlliure, J.; Álvarez-Pol, H.; Audouin, L.; Ayyad, Y.; Bélier, G.; Boutoux, G.; Casarejos, E.; Chatillon, A.; Cortina-Gil, D.; Gorbinet, T.; Heinz, A.; Keli?-Heil, A.; Laurent, B.; Martin, J.-F.; Paradela, C.; Pellereau, E.; Pietras, B.; Ramos, D.; Rodríguez-Tajes, C.; Rossi, D. M.; Simon, H.; Taïeb, J.; Vargas, J.; Voss, B.

    2015-10-01

    The nuclear level density is one of the main ingredients for the statistical description of the fission process. In this work, we propose to constrain the description of this parameter by using fission reactions induced by protons and light ions on 208Pb at high kinetic energies. The experiment was performed at GSI (Darmstadt), where the combined use of the inverse kinematics technique with an efficient detection setup allowed us to measure the atomic number of the two fission fragments in coincidence. This measurement permitted us to obtain with high precision the partial fission cross sections and the width of the charge distribution as a function of the atomic number of the fissioning system. These data and others previously measured, covering a large range in fissility, are compared to state-of-the-art calculations. The results reveal that total and partial fission cross sections cannot unambiguously constrain the level density at ground-state and saddle-point deformations and additional observables, such as the width of the charge distribution of the final fission fragments, are required.

  9. Feasibility of an antiproton catalyzed fission fragment rocket

    SciTech Connect

    Hdinger, D.S.

    1992-03-01

    The purpose of this project was to investigate the feasibility of an antiproton catalyzed fission fragment rocket (FFR). The FFR is characterized by the extraction of fission fragments from the fissile fuel, and the utilization of their kinetic energy for thrust generation. A significant drawback to previous FFR designs was the requirement to maintain a critical nuclear pile as the fission fragment source. The author examined the possibility of replacing the critical pile with a sub-critical pile driven by antiprotons. Recent experiments have revealed that antiprotons stimulate highly energetic fissions in {sup 238}U, with a neutron multiplicity of 13.7 neutrons per fission. This interaction was used as a throttled neutron source. The pile consisted of layers of fissile coated fibers which are designed to allow fission fragments to escape them, where the fragments collide with a fluid. The heated fluid is then ejected from the rocket to provide thrust. The calculations performed indicate that each antiproton injected into the pile can stimulate 8 or more fissions while maintaining a neutron multiplication of less than 0.4. Based on the results seen, the engine design presented is inadequate. Limitations introduced by the reaction fluid far outweigh the simplicity-of-design gained. Despite this, the basic idea of using the antiproton-U interaction as a source of spacecraft propulsion warrants further study.

  10. New fission valley for /sup 258/Fm and nuclei beyond

    SciTech Connect

    Moeller, P.; Nix, J.R.; Swiatecki, W.J.

    1986-01-01

    Experimental results on the fission properties of nuclei close to /sup 264/Fm show sudden and large changes with a change of only one or two neutrons or protons. The nucleus /sup 258/Fm, for instance, undergoes symmetric fission with a half-life of about 0.4 ms and a kinetic energy peaked at about 235 MeV whereas /sup 256/Fm undergoes asymmetric fission with a half-life of about 3 h and a kinetic energy peaked at about 200 MeV. Qualitatively, these sudden changes hve been postulated to be due to the emergence of fragment shells in symmetric fission products close to /sup 132/Sn. A quantitative calculation that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. The implications of the new fission valley on the stability of the heaviest elements is discussed. 33 refs., 12 figs.

  11. Fission Surface Power System Initial Concept Definition

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Under the NASA Exploration Technology Development Program (ETDP) and in partnership with the Department of Energy (DOE), NASA has embarked on a project to develop Fission Surface Power (FSP) technology. The primary goals of the project are to 1) develop FSP concepts that meet expected surface power requirements at reasonable cost with added benefits over other options, 2) establish a hardwarebased technical foundation for FSP design concepts and reduce overall development risk, 3) reduce the cost uncertainties for FSP and establish greater credibility for flight system cost estimates, and 4) generate the key products to allow NASA decision-makers to consider FSP as a preferred option for flight development. The FSP project was initiated in 2006 as the Prometheus Program and the Jupiter Icy Moons Orbiter (JIMO) mission were phased-out. As a first step, NASA Headquarters commissioned the Affordable Fission Surface Power System Study to evaluate the potential for an affordable FSP development approach. With a cost-effective FSP strategy identified, the FSP team evaluated design options and selected a Preliminary Reference Concept to guide technology development. Since then, the FSP Preliminary Reference Concept has served as a point-of-departure for several NASA mission architecture studies examining the use of nuclear power and has provided the foundation for a series of "Pathfinder" hardware tests. The long-term technology goal is a Technology Demonstration Unit (TDU) integrated system test using full-scale components and a non-nuclear reactor simulator. The FSP team consists of Glenn Research Center (GRC), Marshall Space Flight Center (MSFC) and the DOE National Laboratories at Los Alamos (LANL), Idaho (INL), Oak Ridge (ORNL), and Sandia (SNL). The project is organized into two main elements: Concept Definition and Risk Reduction. Under Concept Definition, the team performs trade studies, develops analytical tools, and formulates system concepts. Under Risk Reduction the team develops hardware prototypes and conducts laboratory-based testing.

  12. Simulated fissioning of uranium and testing of the fission-track dating method

    USGS Publications Warehouse

    McGee, V.E.; Johnson, N.M.; Naeser, C.W.

    1985-01-01

    A computer program (FTD-SIM) faithfully simulates the fissioning of 238U with time and 235U with neutron dose. The simulation is based on first principles of physics where the fissioning of 238U with the flux of time is described by Ns = ??f 238Ut and the fissioning of 235U with the fluence of neutrons is described by Ni = ??235U??. The Poisson law is used to set the stochastic variation of fissioning within the uranium population. The life history of a given crystal can thus be traced under an infinite variety of age and irradiation conditions. A single dating attempt or up to 500 dating attempts on a given crystal population can be simulated by specifying the age of the crystal population, the size and variation in the areas to be counted, the amount and distribution of uranium, the neutron dose to be used and its variation, and the desired ratio of 238U to 235U. A variety of probability distributions can be applied to uranium and counting-area. The Price and Walker age equation is used to estimate age. The output of FTD-SIM includes the tabulated results of each individual dating attempt (sample) on demand and/or the summary statistics and histograms for multiple dating attempts (samples) including the sampling age. An analysis of the results from FTD-SIM shows that: (1) The external detector method is intrinsically more precise than the population method. (2) For the external detector method a correlation between spontaneous track count, Ns, and induced track count, Ni, results when the population of grains has a stochastic uranium content and/or when the counting areas between grains are stochastic. For the population method no correlation can exist. (3) In the external detector method the sampling distribution of age is independent of the number of grains counted. In the population method the sampling distribution of age is highly dependent on the number of grains counted. (4) Grains with zero-track counts, either in Ns or Ni, are in integral part of fissioning theory and under certain circumstances must be included in any estimate of age. (5) In estimating standard error of age the standard error of Ns and Ni and ?? must be accurately estimated and propagated through the age equation. Several statistical models are presently available to do so. ?? 1985.

  13. Discovery of a new mode of nuclear fission

    SciTech Connect

    Hulet, E.K.; Wild, J.F.; Dougan, R.J.; Lougheed, R.W.; Landrum, J.H.; Dougan, A.D.; Schaedel, M.; Hahn, R.L.; Baisden, P.A.; Henderson, C.M.

    1986-01-01

    We measured the mass and kinetic-energy partitioning in the spontaneous fission of /sup 258/Fm, /sup 259/Md, /sup 260/Md, /sup 258/No, and /sup 260/(104). Surprisingly, these energy distributions were skewed upward or downward from the peak in each case, except for /sup 260/(104), indicating a composite of two energy distributions. We interpret this as a new mode of fission in which there is mixture of liquid-drop-like and fragment-shell-directed symmetric fission.

  14. Bimodal symmetric fission observed in the heaviest elements

    SciTech Connect

    Hulet, E.K.; Wild, J.F.; Dougan, R.J.; Lougheed, R.W.; Landrum, J.H.; Dougan, A.D.; Schadel, M.; Hahn, R.L.; Baisden, P.A.; Henderson, C.M.

    1986-01-27

    We measured the mass and kinetic-energy partitioning in the spontaneous fission of /sup 258/Fm, /sup 259/Md, /sup 260/Md, /sup 258/No, and /sup 260/(104). All fissioned with mass distributions that were symmetric. Total-kinetic-energy distributions peaked near either 200 or 235 MeV. Surprisingly, these energy distributions were skewed upward or downward from the peak in each case, except for /sup 260/(104), indicating a composite of two energy distributions. We interpret this as a mixture of liquid-drop-like and fragment-shell directed symmetric fission, although theory had not anticipated this phenomenon.

  15. Scission neutron emission and prompt fission neutron spectrum

    E-print Network

    Kornilov, N V

    2001-01-01

    The mass, energy and angular integrated spectra of prompt fission neutrons for sup 2 sup 3 sup 5 U induced fission in the energy range from thermal to 5 MeV were analyzed. It allows assume that about 0.362+-0.025 neutrons per fission are emitted due to another mechanism then neutron emission from excited fragments after full acceleration. The spectrum of scission neutrons consists of two components with average energy 0.98 MeV and 2.74 MeV. The share of scission neutrons and their spectrum shape estimated in this work does not contradict to results of differential experiments analyzed in previous papers.

  16. Cross section for the subbarrier fission of {sup 244}Cm

    SciTech Connect

    Alekseev, A. A.; Bergman, A. A.; Berlev, A. I.; Koptelov, E. A.; Samylin, B. F.; Svirin, M. I.; Trufanov, A. M.; Fursov, B. I.; Shorin, V. S.

    2010-09-15

    The cross section for {sup 244}Cm fission induced by neutrons of energy in the range between 0.07 eV and 20 keV was measured by using the lead slowing-down spectrometer (LSDS-100) of the Institute for Nuclear Research (Russian Academy of Sciences, Moscow). The parameters of the resonance areas were determined for the lowest eight s-wave neutron resonances, and the respective fission widths were evaluated. Also, the parameters of the intermediate structure in the cross section for the subbarrier fission of {sup 244}Cm nuclei were evaluated. The results were compared with available data and recommendations based on evaluations.

  17. Fissioning uranium plasmas and nuclear-pumped lasers

    NASA Technical Reports Server (NTRS)

    Schneider, R. T.; Thom, K.

    1975-01-01

    Current research into uranium plasmas, gaseous-core (cavity) reactors, and nuclear-pumped lasers is discussed. Basic properties of fissioning uranium plasmas are summarized together with potential space and terrestrial applications of gaseous-core reactors and nuclear-pumped lasers. Conditions for criticality of a uranium plasma are outlined, and it is shown that the nonequilibrium state and the optical thinness of a fissioning plasma can be exploited for the direct conversion of fission fragment energy into coherent light (i.e., for nuclear-pumped lasers). Successful demonstrations of nuclear-pumped lasers are described together with gaseous-fuel reactor experiments using uranium hexafluoride.

  18. A fission gas release correlation for uranium nitride fuel pins

    NASA Technical Reports Server (NTRS)

    Weinstein, M. B.; Davison, H. W.

    1973-01-01

    A model was developed to predict fission gas releases from UN fuel pins clad with various materials. The model was correlated with total release data obtained by different experimentors, over a range of fuel temperatures primarily between 1250 and 1660 K, and fuel burnups up to 4.6 percent. In the model, fission gas is transported by diffusion mechanisms to the grain boundaries where the volume grows and eventually interconnects with the outside surface of the fuel. The within grain diffusion coefficients are found from fission gas release rate data obtained using a sweep gas facility.

  19. A hemispherical fission ion chamber designed for ?1 ?g samples

    NASA Astrophysics Data System (ADS)

    Bicknell, Paul A.; Block, Robert C.; Krycuk, George; Nakagome, Yoshihiro

    1980-12-01

    A hemispherical fission ion chamber was designed and built to measure neutron fission cross sections in the RINS spectrometer from 1 eV to 100 keV. The chamber system was tested with 10 ?Ci of 252Cf and the preamplifier overshoot from the RINS gamma flash recovered within 1 ?s to ?5% of the voltage corresponding to the mean fragment energy. One ?g of 235U was substituded for the 252Cf and the 235U energy-dependent fission cross section was measured and found to be in good agreement with the ENDF/B-IV evaluated cross section.

  20. Modelling of fission chambers in current mode—Analytical approach

    NASA Astrophysics Data System (ADS)

    Chabod, Sébastien; Fioni, Gabriele; Letourneau, Alain; Marie, Frédéric

    2006-10-01

    A comprehensive theoretical model is proposed to explain the functioning of fission chambers operated in current mode, even in very high neutron fluxes. The calibration curves are calculated as a function of basic physical parameters as fission rate, gas pressure and geometry of the chambers. The output current at saturation is precisely calculated, as well as the maximum voltage to be applied in order to avoid avalanche phenomena. The electric field distortion due to the space charge phenomena is also estimated. Within this model, the characteristic responses of fission chambers are correctly reproduced, in agreement with the experience feedback obtained at the ILL/Grenoble High-Flux Reactor.

  1. Sensitivity analysis of the fission gas behavior model in BISON.

    SciTech Connect

    Swiler, Laura Painton; Pastore, Giovanni; Perez, Danielle; Williamson, Richard

    2013-05-01

    This report summarizes the result of a NEAMS project focused on sensitivity analysis of a new model for the fission gas behavior (release and swelling) in the BISON fuel performance code of Idaho National Laboratory. Using the new model in BISON, the sensitivity of the calculated fission gas release and swelling to the involved parameters and the associated uncertainties is investigated. The study results in a quantitative assessment of the role of intrinsic uncertainties in the analysis of fission gas behavior in nuclear fuel.

  2. Large optical nonlinearity induced by singlet fission in pentacene films.

    PubMed

    Liu, Yunlong; Zhang, Chunfeng; Wang, Rui; Zhang, Bo; Tan, Zhanao; Wang, Xiaoyong; Xiao, Min

    2015-05-18

    By creating two triplet excitons from one photo-excited singlet exciton, singlet fission in organic semiconductors has drawn tremendous attention for its potential applications in boosting the efficiency of solar conversion. Here, we show that this carrier-multiplication effect can also be used to dramatically improve the nonlinear optical response in organic materials. We have observed large optical nonlinearity with a magnitude of ?((3)) up to 10(-9) esu in pentacene films, which is further shown to be a result of singlet fission by monitoring the temporal dynamics. The potential application of such efficient nonlinear optical response has been demonstrated with a singlet-fission-induced polarization rotation. PMID:25845461

  3. Actinide Neutron-Induced Fission Cross Section Measurements At LANSCE

    SciTech Connect

    Tovesson, F.; Laptev, A. B.; Hill, T. S.

    2011-06-01

    Fission cross sections of a range of actinides have been measured at the Los Alamos Neutron Science Center (LANSCE) in support of nuclear energy applications in a wide energy range from sub thermal energies up to 200 MeV. Parallel-plate ionization chambers are used to measure fission cross sections ratios relative to the {sup 235}U standard while incident neutron energies are determined using the time-of-flight method. Recent measurements include the {sup 233,238}U, {sup 239-242}Pu and {sup 243}Am neutron-induced fission cross sections. Obtained data are presented in comparison with existing evaluations and previous data.

  4. Actinide neutron-induced fission cross section measurements at LANSCE

    SciTech Connect

    Tovesson, Fredrik K; Laptev, Alexander B; Hill, Tony S

    2010-01-01

    Fission cross sections of a range of actinides have been measured at the Los Alamos Neutron Science Center (LANSCE) in support of nuclear energy applications in a wide energy range from sub-thermal energies up to 200 MeV. A parallel-plate ionization chamber are used to measure fission cross sections ratios relative to the {sup 235}U standard while incident neutron energies are determined using the time-of-flight method. Recent measurements include the {sup 233,238}U, {sup 239-242}Pu and {sup 243}Am neutron-induced fission cross sections. Obtained data are presented in comparison with ex isting evaluations and previous data.

  5. Neutrinos, Fission Cycling, and the r-process

    E-print Network

    J. Beun; G. C. McLaughlin; R. Surman; W. R. Hix

    2006-07-26

    It has long been suggested that fission cycling may play an important role in the r-process. Fission cycling can only occur in a very neutron rich environment. In traditional calculations of the neutrino driven wind of the core-collapse supernova, the environment is not sufficiently neutron rich to produce the r-process elements. However, we show that with a reduction of the electron neutrino flux coming from the supernova, fission cycling does occur and furthermore it produces an abundance pattern which is consistent with observed r-process abundance pattern in halo stars. Such a reduction can be caused by active-sterile neutrino oscillations or other new physics.

  6. Coherent bremsstrahlung and GDR width from 252Cf cold fission

    E-print Network

    Deepak Pandit; S. Mukhopadhyay; Srijit Bhattacharya; Surajit Pal; A. De; S. R. Banerjee

    2010-06-03

    The energy spectrum of the high energy gamma-rays in coincidence with the prompt gamma rays has been measured for the spontaneous fission of 252Cf. The nucleus-nucleus coherent bremsstrahlung of the accelerating fission fragments is observed and the result has been substantiated with a theoretical calculation based on the coulomb acceleration model. The width of the giant dipole resonance (GDR) decay from the excited fission fragments has been extracted for the first time and compared with the thermal shape fluctuation model (TSFM) in the liquid drop formalism. The extracted GDR width is significantly smaller than the predictions of TSFM.

  7. Experimental Progress Report--Modernizing the Fission Basis

    SciTech Connect

    Macri, R A

    2012-02-17

    In 2010 a proposal (Modernizing the Fission Basis) was prepared to 'resolve long standing differences between LANL and LLNL associated with the correct fission basis for analysis of nuclear test data'. Collaboration between LANL/LLNL/TUNL has been formed to implement this program by performing high precision measurements of neutron induced fission product yields as a function of incident neutron energy. This new program benefits from successful previous efforts utilizing mono-energetic neutrons undertaken by this collaboration. The first preliminary experiment in this new program was performed between July 24-31, 2011 at TUNL and had 2 main objectives: (1) demonstrating the capability to measure characteristic {gamma}-rays from specific fission products; (2) studying background effects from room scattered neutrons. In addition, a new dual fission ionization chamber has been designed and manufactured. The production design of the chamber is shown in the picture below. The first feasibility experiment to test this chamber is scheduled at the TUNL Tandem Laboratory from September 19-25, 2011. The dual fission chamber design will allow simultaneous exposure of absolute fission fragment emission rate detectors and the thick fission activation foils, positioned between the two chambers. This document formalizes the earlier experimental report demonstrating the experimental capability to make accurate (< 2 %) precision gamma-ray spectroscopic measurements of the excitation function of high fission product yields of the 239Pu(n,f) reaction (induced by quasimonoenergetic neutrons). A second experiment (9/2011) introduced an compact double-sided fission chamber into the experimental arrangement, and so the relative number of incident neutrons striking the sample foil at each bombarding energy is limited only by statistics. (The number of incident neutrons often limits the experimental accuracy.) Fission chamber operation was so exceptional that 2 more chambers have been fabricated; thus fission foils of different isotopes may be left in place with sample changes. The scope of the measurements is both greatly expanded and the results become vetted. Experiment 2 is not reported here. A continuing experiment has been proposed for February 2012.

  8. The discovery and spontaneous fission properties of /sup 262/No

    SciTech Connect

    Lougheed, R.W.; Hulet, E.K.; Wild, J.F.; Moody, K.J.; Dougan, R.J.; Gannett, C.M.; Henderson, R.A.; Hoffman, D.C.; Lee, D.M.

    1989-04-19

    We have discovered /sup 262/No, as the electron capture daughter of /sup 262/Lr(t/sub 1/2/ = 216 m). This new isotope of nobelium decays by spontaneous fission with about a 5-ms half-life which is several orders of magnitude longer than recent theoretical estimates. We measured a sharply symmetric fission-fragment mass division and a bimodal total kinetic energy distribution; the high-energy symmetric-fission path was most abundant. /sup 262/No is the first nuclide with 160 neutrons to be discovered and is the closest to the N = 162 neutron subshell for which enhanced stability is predicted. 14 refs., 3 figs.

  9. PHYSICAL REVIEW C 87, 014617 (2013) Monte Carlo Hauser-Feshbach predictions of prompt fission rays

    E-print Network

    Danon, Yaron

    2013-01-01

    PHYSICAL REVIEW C 87, 014617 (2013) Monte Carlo Hauser-Feshbach predictions of prompt fission rays and emission from primary fission fragments are calculated for thermal neutron induced fission of 235 U and 239 Pu and for spontaneous fission of 252 Cf using a Monte Carlo Hauser-Feshbach approach

  10. Event-by-event study of neutron observables in spontaneous and thermal fission

    E-print Network

    R. Vogt; J. Randrup

    2011-09-17

    The event-by-event fission model FREYA is extended to spontaneous fission of actinides and a variety of neutron observables are studied for spontaneous fission and fission induced by thermal neutrons with a view towards possible applications for detection of special nuclear materials.

  11. Quantifying glacial erosion in the European Alps using apatite fission track dating

    NASA Astrophysics Data System (ADS)

    Wangenheim, Cornelia; Glotzbach, Christoph

    2015-04-01

    To investigate the impact of glacial erosion on landscape evolution during the Quaternary, problems may occur in choosing the best method, because many methods only reflect parts of the era. Erosion rate calculations based on cosmogenic nuclides only cover the Holocene and erosion rate calculations based on river load gauging reflect even shorter timescales (e.g. von Blanckenburg 2005). In this study we investigate the potential of thermochronological methods, especially apatite fission track dating (AFT) to quantify glacial erosion in the European Alps. The topography of the European Alps is strongly influenced by Quaternary glaciations, as it formed characteristic features like overdeepened and hanging valleys. The study area is located in the Central Alps of Switzerland, which is a high mountain area. At ~0.9 Ma glacial erosion has led to a considerable increase in valley incision rates in this area (Haeuselmann et al. 2007) and therefore it is ideally suited to study the glacial impact on landscape evolution. The advantage of using AFT dating, while studying changes in erosional processes, is that possibly arising nonsteady-state erosion will be recorded within the spatial distribution of thermochronological ages. In this study we applied AFT dating on both bedrock and sediments. The bedrock samples derive from different elevations to figure out whether or not spatial differences and elevation dependencies exist. Combined with already published data we have a relatively high sample density distributed throughout the whole study area. The detrital samples originate from stream sediments and from glacial deposits in the form of late glacial moraines and cave sediments from the last ~0.5 Ma in order to obtain possible lateral variations in erosion. The AFT ages of the bedrocks vary between ~4 Ma and ~9 Ma, resulting in an average long-term exhumation rate of ~0.5 km/Ma. Most of the ages range between 7 and 9 Ma, confirmed by prevailing ages of stream sediment samples. The bedrock age distribution of this area indicates that ages do not only increase with elevation, they also show a distinct local trend along major valleys. This trend may be at least partly caused by focused valley incision during glaciations (Shuster et al. 2011), as the youngest ages appear around the position of the equilibrium line altitude of the Last Glacial Maximum, where it is assumed that Quaternary glacial erosion reached an integrative maxima. Haeuselmann, P. Granger, D. E. Jeannin, P.-Y. and Lauritzen, S.-E. (2007): Abrupt glacial valley incision at 0.8 Ma dated from cave deposits in Switzerland. - Geology 35, 143-146. Shuster, D. L., Cuffey, K. M., Sanders, J. W. and Balco, G. (2011): Thermochronometry reveals headward propagation of erosion in alpine landscape. - Science 332, 84-88. von Blanckenburg, F. (2005): The control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment. - Earth and Planetary Science Letters 237, 462 - 479.

  12. Results of a first generation least expensive approach to fission module tests: Non-nuclear testing of a fission system

    NASA Astrophysics Data System (ADS)

    van Dyke, Melissa; Godfroy, Tom; Houts, Mike; Dickens, Ricky; Dobson, Chris; Pederson, Kevin; Reid, Bob; Sena, J. Tom

    2000-01-01

    The use of resistance heaters to simulate heat from fission allows extensive development of fission systems to be performed in non-nuclear test facilities, saving time and money. Resistance heated tests on the Module Unfueled Thermal-hydraulic Test (MUTT) article has been performed at the Marshall Space Flight Center. This paper discusses the results of these experiments to date, and describes the additional testing that will be performed. Recommendations related to the design of testable space fission power and propulsion systems are made. .

  13. Causal link between Quaternary paleoclimatic changes and volcanic islands evolution

    NASA Astrophysics Data System (ADS)

    Quidelleur, X.; Hildenbrand, A.; Samper, A.

    2006-12-01

    High precision radiometric ages of large-volume volcanic flank collapses indicate a causal relationship between the evolution of volcanic islands from different geodynamic contexts and global climatic changes. We present a compilation of previously well-dated events within the last 1 Myr from Tahiti, Hawaii, Canary Islands, together with new ages from Guadeloupe and Martinique (Lesser Antilles). Ages of major flank collapses show a strong correlation with Quaternary climate changes evidenced by a global stack of benthic d18O records. Effectively, most collapses occurred within a glacial to interglacial termination. The ages reported here favor the hypothesis that for the last 900 kyr major flank collapse events occurred during the onset of glacial to interglacial transitions when a sudden influx of melt water from polar ice caps results in rapid sea level rise. Thus, it can be inferred that, when geological causes such as regional tectonics or edifice strength reduction due to volcanic processes are also present, rapid sea level rise can favor large mass wasting events. We propose that following a sub aerial erosion interval during low sea level stands, rapid sea level rise induces enhanced coastal erosion and sudden changes of pore pressure conditions within basal layers, which favor edifice failure. Since these events can trigger tsunamis and can initiate periods of increased volcanic activity, we show here that global warming may result in an increased likelihood of certain geologic hazards, such as large landslides of up to several hundreds cubic kilometers.

  14. Liquid chromatography of hydrocarbonaeous quaternary amines on cyclodextrin bonded silica

    USGS Publications Warehouse

    Abidi, S.L.

    1986-01-01

    Mixtures of n-alkylbenzyldimethylammonium chloride (ABDAC) were resolved into homologous components by high-performance liquid chromatography (HPLC) with a cyclodextrin-bonded silica stationary phase. With a few exceptions, results from this study are similar to those obtained from traditional reversed-phase HPLC. It was found that the presence of electrolytes in aqueous mobile phases is not a critical factor in determining the success of HPLC separation. Under normal HPLC conditions, a mobile phase consisting of either methanol–water (50:50) or acetonitrile–water (30:70) was employed for obtaining adequate resolution of the quaternary ammonium mixtures. Although the percent organic modifier–water profiles were similar to those in previous studies with these compounds, resolution (R) and selectivity (?) parameters were found to be quite susceptible to changes in the mobile phase solvent composition. The retention behavior of the cationic analytes in the homologous series is consistent with the hydrophobic-interaction concept proposed for the retention mechanism via dominant inclusion complex formation. Several electrolytes were chosen for a study of the counter ion effect on the chromatographic characteristics of ABDAC components. Among the electrolytes examined, the perchlorate ion was found most likely to act as an ion-pairing counter ion for ammonium cations in the HPLC system studied. A correlation study established linear relationships between the chain length of ABDAC and the logarithmic capacity factor (k2). The analytical utility of the HPLC method was demonstrated by the analysis of various unknown mixtures.

  15. Effects of late quaternary climate change on Palearctic shrews.

    PubMed

    Prost, Stefan; Klietmann, Johannes; van Kolfschoten, Thijs; Guralnick, Robert P; Waltari, Eric; Vrieling, Klaas; Stiller, Mathias; Nagel, Doris; Rabeder, Gernot; Hofreiter, Michael; Sommer, Robert S

    2013-06-01

    The Late Quaternary was a time of rapid climatic oscillations and drastic environmental changes. In general, species can respond to such changes by behavioral accommodation, distributional shifts, ecophenotypic modifications (nongenetic), evolution (genetic) or ultimately face local extinction. How those responses manifested in the past is essential for properly predicting future ones especially as the current warm phase is further intensified by rising levels of atmospheric carbon dioxide. Here, we use ancient DNA (aDNA) and morphological features in combination with ecological niche modeling (ENM) to investigate genetic and nongenetic responses of Central European Palearctic shrews to past climatic change. We show that a giant form of shrew, previously described as an extinct Pleistocene Sorex species, represents a large ecomorph of the common shrew (Sorex araneus), which was replaced by populations from a different gene-pool and with different morphology after the Pleistocene Holocene transition. We also report the presence of the cold-adapted tundra shrew (S. tundrensis) in Central Europe. This species is currently restricted to Siberia and was hitherto unknown as an element of the Pleistocene fauna of Europe. Finally, we show that there is no clear correlation between climatic oscillations within the last 50 000 years and body size in shrews and conclude that a special nonanalogous situation with regard to biodiversity and food supply in the Late Glacial may have caused the observed large body size. PMID:23505017

  16. Patterns of late Quaternary shelf-margin sedimentation, southwest Louisiana

    SciTech Connect

    Suter, J.R.; Berryhill, H.L.

    1986-09-01

    Late Quaternary extension of the continental shelf in the northern Gulf of Mexico has been largely accomplished by deposition at the shelf margin during sea level lowstands. The distribution and geometry of facies suggest that delta progradation during sea level fall and lowstand is a principal process for shelf accretion. Along the shelf margin of southwest Louisiana, sets of deltaic deposits corresponding to the last two lowstands of sea level have been mapped from high-resolution seismic profiles. Individual deltas extend farther than 5000 m/sup 2/ and are more than 160 m thick. Diapirism has had a controlling effect on sedimentation patterns of the shelf-margin deltas throughout their depositional histories. Shelf-margin deltas have also been the loci for the transfer of large volumes of sediment from the shelf to the upper slope by mass transport, with buried submarine troughs formed by retrogressive shelf-edge failure in association with major streams acting as conduits for sediment movement. In southwest Louisiana, mass transport deposits follow depressions formed by salt diapirism rather than creating broad aprons on the slope.

  17. Effects of Quaternary Ammonium Chain Length on Antibacterial Bonding Agents

    PubMed Central

    Li, F.; Weir, M.D.; Xu, H.H.K.

    2013-01-01

    The objectives of this study were to synthesize new quaternary ammonium methacrylates (QAMs) with systematically varied alkyl chain lengths (CL) and to investigate, for the first time, the CL effects on antibacterial efficacy, cytotoxicity, and dentin bond strength of bonding agents. QAMs were synthesized with CL of 3 to 18 and incorporated into Scotchbond Multi-Purpose (SBMP) bonding agent. The cured resins were inoculated with Streptococcus mutans. Bacterial early attachment was investigated at 4 hrs. Biofilm colony-forming units (CFU) were measured after 2 days. With CL increasing from 3 to 16, the minimum inhibitory concentration and minimum bactericidal concentration were decreased by 5 orders of magnitude. Incorporating QAMs into SBMP reduced bacterial early attachment, with the least colonization at CL = 16. Biofilm CFU for CL = 16 was 4 log lower than SBMP control (p < .05). All groups had similar dentin bond strengths (p > .1). The new antibacterial materials had fibroblast/odontoblast viability similar to that of commercial controls. In conclusion, increasing the chain length of new QAMs in bonding agents greatly increased the antibacterial efficacy. A reduction in Streptococcus mutans biofilm CFU by 4 log could be achieved, without compromising bond strength and cytotoxicity. New QAM-containing bonding agents are promising for a wide range of restorations to inhibit biofilms. PMID:23958761

  18. Ligand exchange in quaternary alloyed nanocrystals--a spectroscopic study.

    PubMed

    Gabka, Grzegorz; Bujak, Piotr; Giedyk, Kamila; Kotwica, Kamil; Ostrowski, Andrzej; Malinowska, Karolina; Lisowski, Wojciech; Sobczak, Janusz W; Pron, Adam

    2014-11-14

    Exchange of initial, predominantly stearate ligands for pyridine in the first step and butylamine (BA) or 11-mercaptoundecanoic acid (MUA) in the second one was studied for alloyed quaternary Cu-In-Zn-S nanocrystals. The NMR results enabled us to demonstrate, for the first time, direct binding of the pyridine labile ligand to the nanocrystal surface as evidenced by paramagnetic shifts of the three signals attributed to its protons to 7.58, 7.95 and 8.75 ppm. XPS investigations indicated, in turn, a significant change in the composition of the nanocrystal surface upon the exchange of initial ligands for pyridine, which being enriched in indium in the 'as prepared' form became enriched in zinc after pyridine binding. This finding indicated that the first step of ligand exchange had to involve the removal of the surface layer enriched in indium with simultaneous exposure of a new, zinc-enriched layer. In the second ligand exchange step (replacement of pyridine with BA or MUA) the changes in the nanocrystal surface compositions were much less significant. The presence of zinc in the nanocrystal surface layer turned out necessary for effective binding of pyridine as shown by a comparative study of ligand exchange in Cu-In-Zn-S, Ag-In-Zn-S and CuInS2, carried out by complementary XPS and NMR investigations. PMID:25252174

  19. Quaternary geochronology using the U-Th-Pb method

    SciTech Connect

    Getty, S.R.; DePaolo, D.J.

    1995-08-01

    We describe a method of uranium-thorium-lead (U-Th-Pb) isotopic age dating for Quaternary rocks. The approach uses an instrumental mass discrimination correction for lead isotope ratios, which allows small enrichments of radiogenic {sup 206}Pb and {sup 208}Pb to be detected at the level of 0.001%. Igneous rocks hosting minerals with a range in {sup 238}U/{sup 204}Pb values of 100 can be dated with uncertainties of approximately {+-}15-20 kyr. A Quarternary rhyolite dated at 1.19 Ma by K-Ar yields a {sup 238}U-{sup 206}Pb age of 1.03{+-}0.10 Ma. A Holocene dacite (9.5 ka) has uniform {sup 206}Pb/{sup 207}Pb to within {+-}0.0015% in groundmass phases, but 1 mm plagioclase phenocrysts have lower {sup 206}Pb/{sup 207}Pb by 0.105{+-}0.002% indicating contamination of the magma after plagioclase crystallization. High precision {sup 206}Pb/{sup 207}Pb ratios may be a useful new tool for petrogenetic studies.

  20. Formation of Late Quaternary paleoshorelines in Crete, Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Mouslopoulou, Vasiliki; Begg, John; Nicol, Andrew; Oncken, Onno; Prior, Christine

    2015-12-01

    Paleoshorelines of Late Quaternary age in western Crete do not exclusively increase in age with rising altitude as is generally observed worldwide. At numerous sites, for example, Late-Holocene paleoshorelines decrease in age with increasing altitude while in other cases paleoshorelines at similar altitude vary in age by tens of thousands of years. We propose that the observed paleoshoreline altitude-age relationships can be accounted for by eustatic sea-level changes and tectonic rock uplift without requiring substantial errors on radiocarbon ages or tectonic subsidence, as has been previously proposed. To test this model we use a dataset consisting of altitude and age data for 71 individual paleoshorelines sampled from 21 sites distributed along the entire Cretan coastline. These data include radiocarbon ages of marine biota (40 new dates) within beachrock resting on paleoshorelines ranging up to 48 kyr BP in age and ?20 m above present sea-level. We find that paleoshoreline formation reflects Late Holocene tectonic rock uplift in western Crete, preceded by eustatic sea-level rise and by >10 kyr BP rock uplift along the entire island. Our observations contravene existing models as they suggest that some paleoshorelines, and their associated lithified beachrock, survived passage through the wave-zone multiple times and formed throughout the sea-level cycle (i.e., preservation is not restricted to highstand deposits). These results may have application globally in regions where erosion-resistant carbonate beachrock mantles paleoshorelines.

  1. Carnivore size and quaternary climatic change in southern Africa

    NASA Astrophysics Data System (ADS)

    Klein, Richard G.

    1986-07-01

    The relationship between carnassial length and latitude south is analyzed for 17 African carnivore species to determine if individuals tend to be larger in cooler climates, as predicted by Bergmann's Rule. With modern data in support, middle and late Quaternary temperatures might then be inferred from mean carnassial length in fossil samples, such as those from Equus Cave, Elandsfontein, Sea Harvest. Duinefontein, and Swartklip in the Cape Province of South Africa. One problematic aspect of the study is the use of carnassial length and latitude as necessary but imperfect substitutes for body size and temperature, respectively. For some species, another difficulty is the relatively small number of available modern specimens, combined with their uneven latitudinal spread. Still, in 14 of the species, carnassial length does tend to increase with latitude south, while mean carnassial length in the same species tends to be greater in those fossil samples which accumulated under relatively cool conditions, as inferred from sedimentologic, palynological, or geochemical data. Given larger modern samples from a wide variety of latitudes, refinement of the mathematical relationship between carnassial length and latitude in various species may even permit quantitative estimates of past temperatures in southern Africa.

  2. Kinetics of synthesizing polymer-supported quaternary ammonium catalysts.

    PubMed

    Wu, Ho-Shing; Lo, Chi-Wei

    2006-01-01

    This study attempted to synthesize the optimum quaterary ammonium poly(styrene-co-methylstyrene) catalyst using the combinatorial chemistry method. The catalyst was synthesized by a mix-split method. A phase-transfer catalyst library with 25 kinds of polystyrene-supported quaternary ammonium salt catalyst was the the result of the reaction of five kinds of chloromethylated crosslinked polystyrene with five tert-amines. The allylation of phenol and the oxidation of benzyl alcohol were used as the probing reaction to screen out the most active catalyst for the reaction using the iterative deconvolution method. The screening conditions included teritary amine and organic solvent. The structure of the most active catalyst in the allylation of phenol shows 20 mol % ring substitution and 0.177-0.25-mm pellet size activated with trihexylamine. For oxidation of benzyl alcohol, the reaction conditions of the most active catalyst included a resin of 20% ring substitution and pellet size of 0.177-0.25 mm, activated with triethylamine reacting in an organic solvent of n-hexane. PMID:17096574

  3. Interhemispheric dynamics of the African rainbelt during the late Quaternary

    NASA Astrophysics Data System (ADS)

    Singarayer, Joy S.; Burrough, Sallie L.

    2015-09-01

    The spatial pattern of precipitation variability in tropical and subtropical Africa over the late Quaternary has long been debated. Prevailing hypotheses variously infer (1) insolation-controlled asymmetry of wet phases between hemispheres, (2) symmetric contraction and expansion of the tropical rainbelt, and (3) independent control on moisture available in Southern Africa via sea surface temperatures in the Indian Ocean. In this study we use climate-model simulations covering the last glacial cycle (120 kyr) with HadCM3 and the multi-model ensembles from PMIP3 (the Palaeoclimate Model Intercomparison Project) to investigate the long-term behaviour of the African rainbelt, and test these simulations against existing empirical palaeohydrological records. Through regional model-data comparisons we find evidence for the validity of several hypotheses, with various proposed processes occurring concurrently but with different regional emphasis (e.g. asymmetric shifts at the seasonal extremes and symmetric expansions/contractions towards West equatorial regions). Crucially, variations in rainfall are associated with multiple forcing mechanisms that vary in their dominance both spatially and temporally over the glacial cycle; an important consideration when interpreting and extrapolating from often relatively short palaeoenvironmental records.

  4. Late Quaternary environments, vegetation and agriculture in northern New Zealand

    NASA Astrophysics Data System (ADS)

    Horrocks, M.; Nichol, S. L.; Augustinus, P. C.; Barber, I. G.

    2007-03-01

    A sedimentological and plant microfossil history of the Late Quaternary is preserved in two sediment cores from early Polynesian ditch systems on southern Aupouri Peninsula. The study places human activities into a geomorphological and ecological context and allows comparison of natural and anthropogenic effects on two different geological settings: a floodplain and a relatively closed peat swamp. The data fill part of the current gap in the environmental record from northern New Zealand, namely MIS 3 (57k-26k yr BP). There is evidence for an increase in fire frequency in the region after 40k 14C yr BP, suggesting a shift to drier (and cooler) conditions. Pollen records show that conifer-hardwood forest dominated by podocarps (especially Dacrydium) prevailed prior to Polynesian arrival and deforestation within the last millennium, with Fuscopsora insignificant throughout. Both cores show sections with gaps in deposition or preservation, possible flood-stripping of peat during the pre-Holocene and mechanical disturbance by early Polynesians. The identification of prehistoric starch grains and other microremains of introduced Colocasia esculenta (taro) in both cores supports indirect evidence that the ditch systems of far northern New Zealand were used for the extensive cultivation of this crop. Copyright

  5. Regulated assembly and disassembly of the yeast telomerase quaternary complex

    PubMed Central

    Tucey, Timothy M.

    2014-01-01

    The enzyme telomerase, which elongates chromosome termini, is a critical factor in determining long-term cellular proliferation and tissue renewal. Hence, even small differences in telomerase levels can have substantial consequences for human health. In budding yeast, telomerase consists of the catalytic Est2 protein and two regulatory subunits (Est1 and Est3) in association with the TLC1 RNA, with each of the four subunits essential for in vivo telomerase function. We show here that a hierarchy of assembly and disassembly results in limiting amounts of the quaternary complex late in the cell cycle, following completion of DNA replication. The assembly pathway, which is driven by interaction of the Est3 telomerase subunit with a previously formed Est1–TLC1–Est2 preassembly complex, is highly regulated, involving Est3-binding sites on both Est2 and Est1 as well as an interface on Est3 itself that functions as a toggle switch. Telomerase subsequently disassembles by a mechanistically distinct pathway due to dissociation of the catalytic subunit from the complex in every cell cycle. The balance between the assembly and disassembly pathways, which dictate the levels of the active holoenzyme in the cell, reveals a novel mechanism by which telomerase (and hence telomere homeostasis) is regulated. PMID:25240060

  6. Quaternary heteroaromatic salts with prophylactic and antidotal activity towards soman

    SciTech Connect

    Sundberg, R.J.; Dalvie, D.; Cordero, J.; Sabat, M.

    1993-05-13

    A series of quaternary heteroaromatic salts has been prepared and evaluated for prophylactic and antidotal activity towards the lethal toxicity of soman. One series of compounds contains 2-, 3-, or 4-(dimethylaminocarbonyloxy)phenoxymethyl substituents at the 2 position of the following rings: 1,3-dimethylimidazolium, 1-methylpyridinium, 1-methylquinolinium, 1,3-dimethylbenzimidazolium and 1-methylimidazo1,2-Apyridinium. The compounds were evaluated both in vitro, by determining the IC50 for electric eel acetylcholinesterase, and in vivo, using both antidotal and prophylactic assays in mice. Compound 2b was most active in the in vitro assay (IC50 = 0.01 M). However, its toxicity is high and compound la is more effective in vivo with 80-100% protective activity against 2 LD50 of soman at 6.2 to 62.5 mg/kg. A second series of compounds consisted of 6-substituted 2'-, 3'-, and 4'-(dimethylaminocarbonyloxy) phenylimidazo (1,2-a) pyridinium salts (8).

  7. Quaternary glaciation of the Tashkurgan Valley, Southeast Pamir

    NASA Astrophysics Data System (ADS)

    Owen, Lewis A.; Chen, Jie; Hedrick, Kathyrn A.; Caffee, Marc W.; Robinson, Alexander C.; Schoenbohm, Lindsay M.; Yuan, Zhaode; Li, Wenqiao; Imrecke, Daniel B.; Liu, Jinfeng

    2012-07-01

    The Quaternary glacial history of Tashkurgan valley, in the transition between the Pamir and Karakoram, in Xinjiang Province, China was examined using remote sensing, field mapping, geomorphic analysis of landforms and sediments, and 10Be terrestrial cosmogenic nuclide dating. Moraines were assigned to four glacial stages: 1) the Dabudaer glacial stage that dates to the penultimate glacial cycle and/or earlier, and may represent one or more glaciations; 2) the Tashkurgan glacial stage that dates to early last glacial, most likely Marine Oxygen Isotope Stage (MIS) 4; 3) the Hangdi glacial stage that dates to MIS 2, possibly early MIS 2; and 4) the Kuzigun glacial stage that dates to the MIS 2, possibly the global Last Glacial Maximum, and is younger than the Hangdi glacial stage. Younger moraines and rock glaciers are present at the heads of tributary valleys; but these were inaccessible because they are located close to politically sensitive borders with Pakistan, Afghanistan and Tajikistan. Glaciers during the Dabudaer glacial stage advanced into the central part of the Tashkurgan valley. During the Tashkurgan glacial stages, glaciers advanced several kilometers beyond the mouths of the tributary valleys into the Tashkurgan valley. Glaciers during the Hangdi and Kuzigun glacial stages advanced just beyond the mouths of the tributary valleys. Glaciation in this part of the Himalayan-Tibetan orogen is likely strongly controlled by northern hemisphere climate oscillations, although a monsoonal influence on glaciation cannot be ruled out entirely.

  8. Latest quaternary volcanism in the St. George Basin, southwestern Utah

    SciTech Connect

    Millings, V.T. III; Green, J.D.; Nusbaum, R.L. . Dept. of Geology)

    1993-03-01

    The St. George Basin was the site of mafic volcanism from about 6 Ma to 1 ka. The nature of latest Quaternary volcanism is of interest because the Basin is recognized as a low temperature (< 90C) geothermal resource area and it is part of the transition zone between the Basin and Range Province and the Colorado Plateau. The authors have studied the geochemistry, mineralogy, and aerial distribution of two of the youngest eruptions centers: (1) Veyo Volcano; and (2) the Diamond Valley scoria cones (DVSC). Veyo Volcano erupted basaltic andesite, beginning with an explosive stage marked by a 0.5 m basal Plinian layer. Later eruptions alternated between quiescent and Strombolian-styles. Phenocrysts include clear plagioclase, sieve-texture plagioclase, olivine and rare augite. The DVSC and associated Santa Clara lava flow are tholeiitic basalt, consisting of olivine phenocrysts, and rare plagioclase phenocrysts. Based on preliminary geochemical data, Diamond Valley rocks exhibit lower incompatible element ratios compared to mafic rocks on the Markagunt Plateau and transition zone rocks. In contrast, Veyo Volcano rocks are similar to transition zone mafic rocks with regard to incompatible element abundances.

  9. Cellular uptake of polyurethane nanocarriers mediated by gemini quaternary ammonium.

    PubMed

    Ding, Mingming; He, Xueling; Wang, Zhigao; Li, Jiehua; Tan, Hong; Deng, Hua; Fu, Qiang; Gu, Qun

    2011-12-01

    The effective passage of drug formulations into tumor cells is a key factor in the development of nanoscale delivery systems. However, rapid cellular uptake with reduced toxicity remains a great challenge for efficient and safe delivery. In this study, we first use gemini quaternary ammonium (GQA) as a cell internalization promoter to enhance the cellular uptake of drug nanocarriers. It is found that a twenty times faster cell internalization could be achieved by introducing GQA into biodegradable multiblock polyurethane nanomicelles, as confirmed by flow cytometry and confocal laser scanning microscopy (CLSM) studies. Meanwhile, an added methoxyl-poly(ethylene glycol) (mPEG) outer corona could protect these cationic micelles from cytotoxicity at high concentrations, as verified by methyl tetrazolium (MTT) assay. Moreover, GQA not only acts as an enhancer for rapid cellular entry, but also plays an important role in controlled self-assembly and high drug loading capacity. Our work offers a new understanding on the role of cationic surfactants; and provides a facile and economical approach for the design of versatile drug nanocarriers to achieve efficient delivery and good biocompatibility. PMID:21907404

  10. Coupled micromorphological and stable isotope analysis of Quaternary calcrete development

    NASA Astrophysics Data System (ADS)

    Adamson, Kathryn; Candy, Ian; Whitfield, Liz

    2015-09-01

    Pedogenic calcretes are widespread in arid and semi-arid regions. Using calcrete profiles from four river terraces of the Rio Alias in southeast Spain, this study explores the potential of using detailed micromorphological and stable isotopic analysis to more fully understand the impacts of Quaternary environmental change on calcrete development. The four profiles increase in carbonate complexity with progressive age, reflecting calcretisation over multiple glacial-interglacial cycles since MIS 9 (c. 300 ka). Calcrete profiles contain a mixture of Alpha (non-biogenic) and Beta (biogenic) microfabrics. Alpha fabrics have higher ?13C and ?18O values. The profiles contain a range of crystal textures, but there is little difference between the ?13C and ?18O values of spar, microspar, and micrite cements. Strong positive covariance between ?13C and ?18O suggests that both isotopes are responding to the same environmental parameter, which is inferred to be relative aridity. The study reveals that the detailed co-analysis of calcrete micromorphology and stable isotope signatures can allow patterns of calcrete formation to be placed into a wider palaeoclimatic context. This demonstrates the potential of this technique to more reliably constrain the palaeoenvironmental significance of secondary carbonates in dryland settings where other proxy records may be poorly preserved.

  11. Interaction of ochratoxin A with quaternary ammonium beta-cyclodextrin.

    PubMed

    Poór, Miklós; Kunsági-Máté, Sándor; Szente, Lajos; Matisz, Gergely; Secenji, Györgyi; Czibulya, Zsuzsanna; K?szegi, Tamás

    2015-04-01

    Ochratoxin A (OTA) is a widely spread nephrotoxic food contaminant mycotoxin. Unfortunately, attenuation or prevention of the toxic effects of OTA is still an unresolved problem. Molecular inclusion of OTA by cyclodextrins (CDs) results in complexes with low stability. In the human organism, OTA exists mostly in the dianionic state (OTA(2-)). Therefore, our major goal was to develop a chemically modified cyclodextrin which gives a more stable complex with OTA than the previously published derivatives and which shows stronger preference towards OTA(2-). In our fluorescence spectroscopic study we demonstrate that quaternary ammonium beta-cyclodextrin (QABCD) fulfils both of these requirements. The calculated stability constant of the QABCD-OTA(2-) complex was 28,840 M(-1) (about 200-fold higher than that of the ?-CD-OTA(2-) complex). We hypothesize, that QABCD may be a suitable tool for the decontamination of different OTA-contaminated drinks; furthermore, for alleviation of the toxic effects of OTA, such complex formation may reduce its absorption from the intestine. PMID:25442535

  12. Late Quaternary sea-level changes of the Persian Gulf

    NASA Astrophysics Data System (ADS)

    Lokier, Stephen W.; Bateman, Mark D.; Larkin, Nigel R.; Rye, Philip; Stewart, John R.

    2015-07-01

    Late Quaternary reflooding of the Persian Gulf climaxed with the mid-Holocene highstand previously variously dated between 6 and 3.4 ka. Examination of the stratigraphic and paleoenvironmental context of a mid-Holocene whale beaching allows us to accurately constrain the timing of the transgressive, highstand and regressive phases of the mid- to late Holocene sea-level highstand in the Persian Gulf. Mid-Holocene transgression of the Gulf surpassed today's sea level by 7100-6890 cal yr BP, attaining a highstand of > 1 m above current sea level shortly after 5290-4570 cal yr BP before falling back to current levels by 1440-1170 cal yr BP. The cetacean beached into an intertidal hardground pond during the transgressive phase (5300-4960 cal yr BP) with continued transgression interring the skeleton in shallow-subtidal sediments. Subsequent relative sea-level fall produced a forced regression with consequent progradation of the coastal system. These new ages refine previously reported timings for the mid- to late Holocene sea-level highstand published for other regions. By so doing, they allow us to constrain the timing of this correlatable global eustatic event more accurately.

  13. New urethane oligodimethacrylates with quaternary alkylammonium for formulating dental composites.

    PubMed

    Buruiana, Tinca; Melinte, Violeta; Popa, Ionela D; Buruiana, Emil C

    2014-04-01

    The aim of this study was to prepare urethane dimethacrylates containing quaternary alkyl (C16, C12) ammonium and polyethylene glycol short sequences (Mn, 400 g/mol) and to investigate their behaviour in some experimental formulations in order to evaluate their potential applicability in the dental composites field. The structure of urethane dimethacrylates has been confirmed by (1)H ((13)C) NMR and FTIR spectra, as well as by electrospray ionization tandem mass spectroscopy, and gel permeation chromatography measurements. The effects of the cationic macromers on the properties of the filled/non-filled composites were examined through FTIR, photoDSC, and specific measurements as volumetric polymerization shrinkage, water sorption/solubility, contact angle, mechanical parameters, and morphology. The monomer compositions based on cationic dimethacrylate (6.88-27.52 wt%), BisGMA-analogue (48.18-68.82 wt%) and TEGDMA (23.3 wt%) showed a good photoreactivity in terms of double bond conversion (DC, 50.07-68.81 %) and polymerization rate (Rp, 0.099-0.141 s(-1)) measured by photoDSC compared to a control sample (BisGMA-1/TEGDMA: DC, 45.91 %; Rp, 0.162 s(-1)), while the polymerization shrinkage increased in acceptable limits (5.37-7.74 vol%). The mechanical properties (compressive, flexural and diametral tensile strength) of the composite resin incorporating 70 wt% silanized zirconium silicate micro/nanopowder can be modulated by the initial co-monomer concentrations. PMID:24435527

  14. Radiolysis of simple quaternary ammonium salt components of Amberlite resin

    NASA Astrophysics Data System (ADS)

    Dhiman, Surajdevprakash B.; LaVerne, Jay A.

    2013-05-01

    The radiation chemical yields of gaseous products, H2 and CH4, in the radiolysis of dry methylammonium chloride, dimethylammonium chloride, trimethylammonium chloride, tetramethylammonium chloride and benzyl trimethylammonium chloride by ?-rays and 5 MeV helium ions have been investigated. Some of these amines are the different components of the quaternary ammonium resin Amberlite, which is a strongly basic anion exchange resin based on a polystyrene divinylbenzene copolymer. Molecular hydrogen yields with ?-radiolysis range from a high of 4.43 molecules per 100 eV for trimethylammonium chloride to 0.07 and 0.05 molecules per 100 eV for tetramethylammonium chloride and benzyl trimethylammonium chloride, respectively. Yields of methane gas are generally negligible except for trimethylammonium chloride and tetramethylammonium chloride, 0.26 and 0.02 molecules per 100 eV, respectively. Isotopic labeling studies suggest that the first step in H2 production is the breakage of the Nsbnd H bond followed by abstraction of Hrad atom from the methyl groups. EPR analysis shows the formation of both N and C centered radicals. A comparison is made between the radiolysis of Amberlite and its various components.

  15. Epiguruk: a late Quaternary environmental record from northwestern Alaska

    USGS Publications Warehouse

    Hamilton, T.D.; Ashley, G.M.

    1993-01-01

    Epiguruk, a prominent bluff along the Kobuk River in northwestern Alaska, exposes a rich depositional record of Quaternary eolian and fluvial sand, with associated loess, paleosols, and periglacial features. Three major complexes of alluvial and eolian deposits are separated by two conspicuous organic-rich paleosols which formed during cool-moist interstadial intervals. Sediments between the two paleosols include eolian, channel, and floodplain deposits that formed during alluviation of the Kobuk River to a height of about 12m above the present level. The youngest depositional complex, which overlies the upper paleosol, is divisible into late Wisconsinan and Holocene components and into fluvial-channel, flood-plain, eolian-dune, sand-sheet, loess, and pond facies. Eolian sand from the active Kobuk sand sea overloaded the river during late Wisconsinan time, causing it to alluviate to about 13m above its modern level. The Holocene record reflects erosion and deposition by a small southern Tributary to the Kobuk River, downcutting by the Kobuk River toward its modern level, and subsequent erosion across a meander belt nearly 8km wide. 66 radiocarbon ages, many from rooted shrubs, provide a firm chronology for the past 35 k.y. at Epiguruk. -from Authors

  16. Quaternary geology of the Rhode Island inner shelf

    USGS Publications Warehouse

    Needell, S. W.; O'Hara, C. J.; Knebel, H. J.

    1983-01-01

    Five sedimentary units and three erosional unconformities identified in high-resolution seismic-reflection profiles reveal the stratigraphic framework and Quaternary history of the inner continental shelf south of Narragansett Bay, Rhode Island. Late Tertiary to early Pleistocene rivers eroded the pre-Mesozoic bedrock and the Upper Cretaceous to lower Tertiary coastal plain and continental shelf strata to form a lowland and cuesta having a north-facing escarpment. The lowland and landward flanks of the cuesta were modified by glaciers during Pleistocene time and subsequently were overlain by drift and end moraine deposits of the late Wisconsinan ice advance. During deglaciation, freshwater lakes formed between the retreating ice and end moraines. Prior to sea-level rise, the drift and older deposits were cut by streams flowing south and southwestward toward Block Island Sound. As sea level rose, postglacial valleys were partly filled by fluvial, freshwater-peat, estuarine and salt-marsh deposits. Transgressing seas eroded the sea floor, exposing bedrock and coastal plain outcrops, and deposited marine sediments. ?? 1983.

  17. Scientists Identify New Quaternary Materials for Solar Cell Absorbers (Fact Sheet), NREL Highlights, Science

    SciTech Connect

    Not Available

    2011-10-01

    Research provides insight for exploring use of earth-abundant quaternary semiconductors for large-scale solar cell applications. For large-scale solar electricity generation, it is critical to find new material that is Earth abundant and easily manufactured. Previous experimental studies suggest that Cu{sub 2}ZnSnS{sub 4} could be a strong candidate absorber materials for large-scale thin-film solar cells due to its optimal bandgap, high adsorption coefficient, and ease of synthesis. However, due to the complicated nature of the quaternary compound, it is unclear whether other quaternary compounds have physical properties suitable for solar cell application. Researchers at the National Renewable Energy Laboratory (NREL), Fudan University, and University College London have performed systematic searches of quaternary semiconductors using a sequential cation mutation method in which the material properties of the quaternary compounds can be derived and understood through the evolution from the binary, to ternary, and to quaternary compounds. The searches revealed that in addition to Cu{sub 2}ZnSnS{sub 4}, Cu{sub 2}ZnGeSe{sub 4} and Cu{sub 2}ZnSnSe{sub 4} are also suitable quaternary materials for solar cell absorbers. Through the extensive study of defect and alloy properties of these materials, the researchers propose that to maximize solar cell performance, growth of Cu{sub 2}ZnSnS{sub 4} under Cu-poor/Zn-rich conditions will be optimal and the formation of Cu{sub 2}ZnSn(S,Se){sub 4} alloy will be beneficial in improving solar cell performance.

  18. The translational landscape of fission yeast meiosis and sporulation

    E-print Network

    Duncan, Caia D. S.; Mata, Juan

    2014-06-15

    Sexual development in the fission yeast Schizosaccharomyces pombe culminates in meiosis and sporulation. We used ribosome profiling to investigate the translational landscape of this process. We show that the translation efficiency of hundreds...

  19. Identification of Fissionable Materials Using the Tagged Neutron Technique

    SciTech Connect

    R.P. Keegan, J.P. Hurley, J.R. Tinsley, R. Trainham

    2009-06-30

    This summary describes experiments to detect and identify fissionable materials using the tagged neutron technique. The objective of this work is to enhance homeland security capability to find fissionable material that may be smuggled inside shipping boxes, containers, or vehicles. The technique distinguishes depleted uranium from lead, steel, and tungsten. Future work involves optimizing the technique to increase the count rate by many orders of magnitude and to build in the additional capability to image hidden fissionable materials. The tagged neutron approach is very different to other techniques based on neutron die-away or photo-fission. This work builds on the development of the Associated Particle Imaging (API) technique at the Special Technologies Laboratory (STL) [1]. Similar investigations have been performed by teams at the Oak Ridge National Laboratory (ORNL), the Khlopin Radium Institute in Russia, and by the EURITRACK collaboration in the European Union [2,3,4].

  20. Active Neutron Interrogation to Detect Shielded Fissionable Material

    SciTech Connect

    D. L. Chichester; E. H. Seabury

    2009-05-01

    Portable electronic neutron generators (ENGs) may be used to interrogate suspicious items to detect, characterize, and quantify the presence fissionable material based upon the measurement of prompt and/or delayed emissions of neutrons and/or photons resulting from fission. The small size (<0.2 m3), light weight (<12 kg), and low power consumption (<50 W) of modern ENGs makes them ideally suited for use in field situations, incorporated into systems carried by 2-3 individuals under rugged conditions. At Idaho National Laboratory we are investigating techniques and portable equipment for performing active neutron interrogation of moderate sized objects less than ~2-4 m3 to detect shielded fissionable material. Our research in this area relies upon the use of pulsed deuterium-tritium ENGs and the measurement of die-away prompt fission neutrons and other neutron signatures in-between neutron pulses from the ENG and after the ENG is turned off.

  1. Fusion-fission hybrid studies in the United States

    SciTech Connect

    Moir, R.W.; Lee, J.D.; Berwald, D.H.; Cheng, E.T.; Delene, J.G.; Jassby, D.L.

    1986-05-20

    Systems and conceptual design studies have been carried out on the following three hybrid types: (1) The fission-suppressed hybrid, which maximizes fissile material produced (Pu or /sup 233/U) per unit of total nuclear power by suppressing the fission process and multiplying neutrons by (n,2n) reactions in materials like beryllium. (2) The fast-fission hybrid, which maximizes fissile material produced per unit of fusion power by maximizing fission of /sup 238/U (Pu is produced) in which twice the fissile atoms per unit of fusion power (but only a third per unit of nuclear power) are made. (3) The power hybrid, which amplifies power in the blanket for power production but does not produce fuel to sell. All three types must sell electrical power to be economical.

  2. Single Particle Fluorescence Burst Analysis of Membrane Fission 

    E-print Network

    Brooks, Arielle L

    2015-05-13

    The ability to catalyze the fission step of endocytosis is critical to many biological processes including cell communication and synaptic transmission. This activity must be tightly regulated for cellular homeostasis. Limitations of current...

  3. Delayed neutron measurements from fast fission of actinide waste isotopes 

    E-print Network

    Charlton, William S.

    1997-01-01

    A study was performed to determine the delayed neutron emission properties from fast fission of several actinide waste isotopes. The specific isotopes evaluated were U-235, Np-237, and Am-243. A calculational technique based on the microscopic...

  4. New Type of Asymmetric Fission in Proton-Rich Nuclei

    SciTech Connect

    Andreyev, A. N.; Elseviers, J.; Huyse, M.; Van Duppen, P.; Bree, N.; Cocolios, T. E.; Diriken, J.; Ivanov, O.; Van den Bergh, P.; Antalic, S.; Barzakh, A.; Fedorov, D.; Comas, V. F.; Heredia, J. A.; Fedosseev, V.; Marsh, B. A.; Van De Walle, J.; Franchoo, S.; Nishio, K.

    2010-12-17

    A very exotic process of {beta}-delayed fission of {sup 180}Tl is studied in detail by using resonant laser ionization with subsequent mass separation at ISOLDE (CERN). In contrast to common expectations, the fission-fragment mass distribution of the post-{beta}-decay daughter nucleus {sup 180}Hg (N/Z=1.25) is asymmetric. This asymmetry is more surprising since a mass-symmetric split of this extremely neutron-deficient nucleus would lead to two {sup 90}Zr fragments, with magic N=50 and semimagic Z=40. This is a new type of asymmetric fission, not caused by large shell effects related to fragment magic proton and neutron numbers, as observed in the actinide region. The newly measured branching ratio for {beta}-delayed fission of {sup 180}Tl is 3.6(7)x10{sup -3}%, approximately 2 orders of magnitude larger than in an earlier study.

  5. Relative kinetic energy correction to self-consistent fission barriers

    SciTech Connect

    Skalski, Janusz

    2006-11-15

    The effect of spurious relative kinetic energy removal on the fission barriers is discussed within the Skyrme Hartree-Fock method. Calculations for medium-heavy nuclei show that this correction is large and in the right direction.

  6. A new approach to barrier-top fission dynamics

    E-print Network

    Bertsch, G F

    2015-01-01

    We proposed a calculational framework for describing induced fission that avoids the Bohr-Wheeler assumption of well-defined fission channels. The building blocks of our approach are configurations that form a discrete, orthogonal basis and can be characterized by both energy and shape. The dynamics is to be determined by interaction matrix elements between the states rather than by a Hill-Wheeler construction of a collective coordinate. Within our approach, several simple limits can be seen: diffusion; quantized conductance; and ordinary decay through channels. The specific proposal for the discrete basis is to use the $K^\\pi$ quantum numbers of the axially symmetric Hartree-Fock approximation to generate the configurations. Fission paths would be determined by hopping from configuration to configuration via the residual interaction. We show as an example the configurations needed to describe a fictitious fission decay $^{32}{\\rm S} \\rightarrow ^{16}{\\rm O} + ^{16}{\\rm O}$. We also examine the geometry of th...

  7. Thermodynamics of fission products in UO2+-x

    SciTech Connect

    Nerikar, Pankaj V

    2009-01-01

    The stabilities of selected fission products - Xe, Cs, and Sr - are investigated as a function of non-stoichiometry x in UO{sub 2{+-}x}. In particular, density functional theory (OFT) is used to calculate the incorporation and solution energies of these fission products at the anion and cation vacancy sites, at the divacancy, and at the bound Schottky defect. In order to reproduce the correct insulating state of UO{sub 2}, the DFT calculations are performed using spin polarization and with the Hubbard U tenn. In general, higher charge defects are more soluble in the fuel matrix and the solubility of fission products increases as the hyperstoichiometry increases. The solubility of fission product oxides is also explored. CS{sub 2}O is observed as a second stable phase and SrO is found to be soluble in the UO{sub 2} matrix for all stoichiometries. These observations mirror experimentally observed phenomena.

  8. Fusion-fission reactions with modified Woods-Saxon potential

    E-print Network

    Ning Wang; Kai Zhao; Werner Scheid; Xizhen Wu

    2007-12-15

    A modified Woods-Saxon potential model is proposed for a unified description of the entrance channel fusion barrier and the fission barrier of fusion-fission reactions based on the Skyrme energy-density functional approach. The fusion excitation functions of 120 reactions have been systematically studied. The fusion (capture) cross sections are well described with the calculated potential and an empirical barrier distribution. Incorporating a statistical model (HIVAP code) for describing the decay of the compound nucleus, the evaporation residue (and fission) cross sections of 51 fusion-fission reactions have been systematically investigated. Optimal values of some key parameters of the HIVAP code are obtained based on the experimental data of these reactions. The experimental data are reasonably well reproduced by the calculated results. The upper and lower confidence limits of the systematic errors of the calculated results are given.

  9. Singlet exciton fission : applications to solar energy harvesting

    E-print Network

    Thompson, Nicholas John

    2014-01-01

    Singlet exciton fission transforms a single molecular excited state into two excited states of half the energy. When used in solar cells it can double the photocurrent from high energy photons increasing the maximum ...

  10. Localization lengthscales of triplet excitons in singlet fission materials

    E-print Network

    Bayliss, Sam L.; Thorley, Karl J.; Anthony, John E.; Bouchiat, Hélène; Greenham, Neil C.; Chepelianskii, Alexei D.

    2015-09-21

    singlet fission materials with distinct solid-state packing, and correlate the extracted localization lengthscales with the role of the excitonic environment. Using the magnetic susceptibility simultaneously determined through our experiments, we compare...

  11. Parallel Fission Bank Algorithms in Monte Carlo Criticality Calculations

    E-print Network

    Romano, Paul Kollath

    In this work we describe a new method for parallelizing the source iterations in a Monte Carlo criticality calculation. Instead of having one global fission bank that needs to be synchronized, as is traditionally done, our ...

  12. Microscopic theory of singlet exciton fission. III. Crystalline pentacene

    SciTech Connect

    Berkelbach, Timothy C. Reichman, David R.; Hybertsen, Mark S.

    2014-08-21

    We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singlet fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems.

  13. Singlet fission efficiency in tetracene-based organic solar cells

    E-print Network

    Wu, Tony C.

    Singlet exciton fission splits one singlet exciton into two triplet excitons. Using a joint analysis of photocurrent and fluorescence modulation under a magnetic field, we determine that the triplet yield within optimized ...

  14. The Nature of Singlet Exciton Fission in Carotenoid Aggregates

    E-print Network

    Musser, Andrew J.; Maiuri, Margherita; Brida, Daniele; Cerullo, Giulio; Friend, Richard H.; Clark, Jenny

    2015-03-31

    Singlet exciton fission allows the fast and efficient generation of two spin triplet states from one photoexcited singlet. It has the potential to improve organic photovoltaics, enabling efficient coupling to the blue to ultraviolet region...

  15. Transcriptional regulatory network for sexual differentiation in fission yeast

    E-print Network

    Mata, Juan; Wilbrey, Anna; Bahler, Jurg

    2007-10-10

    Abstract Background Changes in gene expression are hallmarks of cellular differentiation. Sexual differentiation in fission yeast (Schizosaccharomyces pombe) provides a model system for gene expression programs accompanying and driving cellular...

  16. On the rearrangement time of the fission reaction

    E-print Network

    G. Mouze; C. Ythier

    2010-04-08

    The rearrangement time \\Deltat of the fission reaction can be extracted from the full-width at half maximum (f.w.h.m.) of the isotopic distributions of fission fragments if this width is attributed to an uncertainty \\DeltaN in the neutron-number N of the fragment; then the energy-time uncertainty relation leads to \\Deltat = 0.17 yoctosecond.

  17. Calculation of Fission Observables Through Event-by-Event Simulation

    SciTech Connect

    Randrup, J; Vogt, R

    2009-06-04

    The increased interest in more exclusive fission observables has demanded more detailed models. We present here a new computational model, FREYA, that aims to met this need by producing large samples of complete fission events from which any observable of interest can then be extracted consistently, including arbitrary correlations. The various model assumptions are described and the potential utility of the model is illustrated by means of several novel correlation observables.

  18. Evaluation and compilation of fission product yields 1993

    SciTech Connect

    England, T.R.; Rider, B.F.

    1995-12-31

    This document is the latest in a series of compilations of fission yield data. Fission yield measurements reported in the open literature and calculated charge distributions have been used to produce a recommended set of yields for the fission products. The original data with reference sources, and the recommended yields axe presented in tabular form. These include many nuclides which fission by neutrons at several energies. These energies include thermal energies (T), fission spectrum energies (F), 14 meV High Energy (H or HE), and spontaneous fission (S), in six sets of ten each. Set A includes U235T, U235F, U235HE, U238F, U238HE, Pu239T, Pu239F, Pu241T, U233T, Th232F. Set B includes U233F, U233HE, U236F, Pu239H, Pu240F, Pu241F, Pu242F, Th232H, Np237F, Cf252S. Set C includes U234F, U237F, Pu240H, U234HE, U236HE, Pu238F, Am241F, Am243F, Np238F, Cm242F. Set D includes Th227T, Th229T, Pa231F, Am241T, Am241H, Am242MT, Cm245T, Cf249T, Cf251T, Es254T. Set E includes Cf250S, Cm244S, Cm248S, Es253S, Fm254S, Fm255T, Fm256S, Np237H, U232T, U238S. Set F includes Cm243T, Cm246S, Cm243F, Cm244F, Cm246F, Cm248F, Pu242H, Np237T, Pu240T, and Pu242T to complete fission product yield evaluations for 60 fissioning systems in all. This report also serves as the primary documentation for the second evaluation of yields in ENDF/B-VI released in 1993.

  19. Some New Aspects of Bimodal Fission in 258Fm Isotope

    E-print Network

    A. Staszczak; Z. Lojewski

    1996-03-21

    Using the multidimensional dynamic--programming method (MDPM) in the four--dimensional deformation space $\\{\\beta_{\\lambda}\\}$ with $\\lambda$=2, 4, 35 and 6 we were able to study evolution of the action integral for the fissioning nucleus $^{258}$Fm. We found the second minimum on the cross--section of the action integral for $\\beta_2 \\approx 1$ , what we interpret as the dynamical evidence of the bimodal fission in this heavy Fm isotope.

  20. Evidence for Conical Intersection Dynamics Mediating Ultrafast Singlet Exciton Fission

    E-print Network

    Musser, Andrew J.; Liebel, Matz; Schnedermann, Christoph; Wende, Torsten; Kehoe, Tom B.; Rao, Akshay; Kukura, Philipp

    2015-03-16

    cells. By converting high-energy photons into two low-energy excited states, singlet fission offers a means to overcome thermalisation losses. Devices based on pentacene, a fission sensitiser, have demonstrated external quantum efficiencies of 129... techniques such as transient absorption or photoluminescence spectroscopy enable direct monitoring of singlet and triplet exciton populations and the kinetics of their interconversion2,13–17. These methods, however, are generally insensitive to the nature...