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1

The effect of assimilation and fractional crystallization on U-series disequilibria in arc lavas  

NASA Astrophysics Data System (ADS)

U-series disequilibria in young arc lavas provide critical temporal constraint on magmatism in arc settings. Most young arc lavas have (231Pa/235U) and (226Ra/230Th) greater than unity. Although the majority of young arc lavas have 238U excess over 230Th, a significant amount of samples have (238U/230Th) < 1. Models involving recent addition of U-Ra rich fluids to the mantle wedge can explain the 238U and 226Ra excesses over 230Th, but it cannot explain 231Pa excess or 230Th excess. In-growth melting models can produce 231Pa excess and 230Th excess, but it cannot account for the overall positive correlation between 226Ra excess and Ba/Th or Sr/Th, which is interpreted as a typical feature of fluid addition. There are still heated debates on generation of U-series disequilibria in arc lavas and time-scale of magmatisms in convergent margins. Most arc lavas have experienced significant assimilation and fractional crystallization (AFC) during magma evolution. Although AFC processes can fundamentally change trace element and isotopic features of magma, its effect on U-series disequilibria has not been rigorously investigated despite its importance. It is not quite clear yet whether the correlations of U-series data with major-trace element compositions of arc lavas (e.g., (226Ra/230Th) vs. Sr/Th or Ba/Th) reflect the geochemical features of the fluid-metasomatised mantle wedge or result from magma differentiation processes. In this study, we use a numerical model to show that time-dependent AFC processes can significantly change U-series data and other geochemical features of arc lavas via fractional crystallization, decay of short-lived nuclides, and dilution by old crustal assimilant. The positive correlation between 226Ra excess and Ba/Th or Sr/Th can be produced by fractionation of plagioclase and amphibole with contemporaneous decay of 226Ra. Assimilation of old crustal materials may dilute the primary U-series disequilibria originating from melting of the metasomatised mantle. Our model can also reconcile the discrepancy of the time scales of arc magmatism indicated by U-Th-Pa-Ra and 10Be/Be systematics. Because correlations between parameters sensitive to fluid addition and U-series data could simply be produced by the AFC processes in a magma chamber within several thousands years, recent fluid addition and ultra-fast upwelling rates of magma may not be required for generation and preservation of 226Ra excess in young arc lavas. U-series disequilibria observed in arc settings might reflect in-growth melting in the mantle wedge plus magma differentiation processes in magma chamber at crustal depths.

Huang, F.; Gao, L.; Lundstrom, C. C.

2007-12-01

2

Characterization of Contaminant Transport Using Naturally-Occurring U-Series Disequilibria  

SciTech Connect

Study the migration of nuclear waste contaminants in subsurface fractured systems using naturally occurring uranium and thorium-series radionuclides as tracers under in-situ physico-chemical and hydrogeologic conditions. Radioactive disequilibria among members of these decay-series nuclides can provide information on the rates of adsorption-desorption and transport of contaminants as well as on fluid transport and rock dissolution in a natural setting.

TEH-LUNG KU

2001-06-01

3

The extent of U-series disequilibria produced during partial melting of the lower crust with implications for the formation of the Mount St. Helens dacites  

Microsoft Academic Search

The extent to which U-series disequilibria can be produced during partial melting of mafic lower crust is quantified using a simple batch melting model and both experimental and theoretical partition coefficients for U, Th and Ra. We show that partial melting of mafic lower crust can only produce small disequilibria between 238U, 230Th and 226Ra. Crystallisation of basalt and mixing

K. Berlo; S. Turner; J. Blundy; C. Hawkesworth

2004-01-01

4

The Influence of Ridge Geometry on Crustal Accretion: Insights From U-series Disequilibria on the SW Indian Ridge  

NASA Astrophysics Data System (ADS)

Recent work has proposed that crustal accretion on ultra-slow spreading plate boundaries, both magmatic and amagmatic, is largely a function of ridge geometry, melt production, and the ensuing change in the lithospheric thermal regime. We present U-series data from the ultra-slow spreading SW Indian Ridge in an attempt to unravel some of the complexities embedded in the issues surrounding spreading geometry and crustal accretion. Initial 238U-230Th-226Ra disequilibria measurements on 12 dredged glasses from between 10-25 E on the SW Indian Ridge show 238U and 230Th disequilibria. We interpret the 238U excesses (230Th/238U < 1) and 230Th excesses (230Th/238U > 1) to be primary based on measured 226Ra/230Th disequilibria, which indicate the lavas are young (< 8 ka). The suite as a whole exhibits a large range in 230Th/232Th and 238U/232Th, covering nearly the entire extent of variability seen in the global U-series MORB database. Glasses from the oblique segment show the most enriched compositions (230Th/232Th = 0.8 and 238U/232Th = 0.76) of any MORB measured but have minor 230Th excesses (<9%) or small 238U excesses (3.5%). In contrast, 230Th excesses in lavas from the orthogonal spreading segment vary from 2 - 29% and are elevated relative to values on the oblique spreading segment. To a first order, this may suggest strikingly different melting regimes beneath each spreading segment. Contrary to most existing MORB U-series data, the majority of the oblique segment lavas do not maintain a negative correlation between 230Th/238U and depth, while the orthogonal segment lavas do. Our U-series data indicate that the change in ridge geometry from the orthogonal spreading segment to the oblique spreading segment directly affects the lithospheric thermal regime (e.g. thickening of the conductive cooling lid), which therein produces changes in the melting column, depth of melting, melt production, and melt transport. We will address these melting parameters as well as constrain the effective source composition (e.g. garnet peridotite versus garnet pyroxenite).

Standish, J. J.; Sims, K. W.; Dick, H. J.

2004-12-01

5

TH isotope and U-series disequilibria in some alkali basalts  

NASA Astrophysics Data System (ADS)

The activities of 238U-series nuclides and 232Th have been measured by alpha spectrometry for nine alkali basalts from Heard island, Mt. Cameroon, Nyamuragira, and Nyiragongo. Large 226Ra enrichments are inferred to be absent from all, suggesting the absence of subsolidus fluids before magma genesis. Th isotope ratios are consistent with deep metasomatism forming carbonates beneath Nyiragongo, versus shallower metasomatism forming amphibole beneath Nyamuragira. In contrast, the Th/U ratio in the Nyamuragira source has increased with time, which is used to confirm that the Th/U ratio of the mantle is about 4.2.

Williams, R. W.; Gill, J. B.

1992-01-01

6

Source heterogeneity and melting conditions along the Southeast Indian Ridge: A U-series disequilibria perspective  

NASA Astrophysics Data System (ADS)

Variations in axial depth and spreading rate along the global system of mid-ocean ridges may be controlled either by mantle temperature and upwelling (melting) rate, or by chemical composition (mantle heterogeneity) and associated melting conditions, but the relative importance of each is poorly understood. To examine this on a regional scale (102 to 103 km), we have measured U-Th isotopes on 16 basaltic glasses collected along the Southeast Indian Ridge (SEIR) from 90 E to 117 E. This section of ridge is characterized by nearly constant spreading rate (70-75 mm/yr) and by a west-to-east gradient in axial depth from 2300 m to >4500 m, similar to that of the global ridge system away from the influence of hotspots. However, unlike the global dataset of U-series measurements on MORB, axial depth does not negatively correlate with measured 230Th-excess along the SEIR. This suggests that, at a regional scale, depth and extent of melting in the Indian Ocean mantle is influenced both by variations in mantle temperature and mantle composition. The SEIR glasses analyzed in this study can be separated into 3 geographically distinct groups; a western group (WG, 90E to 98E, 5 samples), a middle group (MG, 100E to 114E, 9 samples), and an eastern group (EG, east of 114E, 2 samples). Th and U concentrations range from 130-1158 ppb and 55-313 ppb, respectively, with measured Th/U = 2.35 to 3.78. All samples have 230Th- excesses, with (230Th/238U) ranging from 1.01 to 1.21. On a U-Th equiline diagram the geographic groups form 3 offset linear arrays, with the WG characterized by (230Th/232Th) = 1.42 to 1.24, the MG by (230Th/232Th) = 1.17 to 0.96, and the EG by (230Th/232Th) = 1.01 to 0.88. Collectively, these data have a range in (230Th/232Th)-(238U/232Th) covering nearly the entire global MORB array. All samples have pristine (234U/238U) = 1.000 0.004 indicating that the 230Th-excesses and (230Th/232Th) are magmatic in origin. ^{226}Ra-excesses (in 9 of 10 samples analyzed) indicate that post-eruptive decay does not contribute significantly to the observed variations in 230Th-excess. The slope of a sample array on a U-Th equiline diagram may be an indicator of solid mantle upwelling rate (Lundstrom et al., 1998), with a shallower slope produced by slower upwelling. A linear regression of all the SEIR data has a slope (0.85), similar to that of the fast spreading southern East Pacific Rise. However, when the geographical groupings are considered, the slope is steepest in the EG (1.45), intermediate in the MG (0.81) and shallowest in the WG (0.57). This is opposite of the predicted trend at constant spreading rate, where faster upwelling would imply hotter mantle and thus produce shallower axial depths in the west. This suggests that variations in melt production and axial depth, along the SEIR, are not solely produced by a west- to-east decrease in mantle upwelling rate. There is also a progression from ? < ?Pb in the west to ? ? ?Pb in the east (where ? equals the measured Th/U and ?Pb equals the time integrated Th/U computed from Pb-isotope systematics). This progression is consistent with an increased contribution from older enriched mantle that has melted with less Th-U fractionation in the eastern portion of the study area. Collectively, our results suggest that along the SEIR the geochemical variations depend as much on what is melting as they do on how it melts.

Russo, C. J.; Rubin, K. H.; Graham, D. W.

2006-12-01

7

Determining eruption ages and erosion rates of Quaternary basaltic volcanism from combined U-series disequilibria and cosmogenic exposure ages  

NASA Astrophysics Data System (ADS)

We present 238U-230Th -226Ra disequilibria and cosmogenic 3He and 36Cl data for the Bluewater flow of the Zuni-Bandera volcanic field in western New Mexico. The 238U-230Th disequilibria measured on separated groundmass phases yield an internal isochron age of 68 ka (+24/ 20 ka; 2?). This value cannot be directly compared with surface exposure ages unless erosion rates are known. The apparent (zero erosion) ages determined from both the 3He concentration (47.5 5 ka; 2?) and the 36Cl concentration (41.2 8.8 ka; 2?) are significantly younger than the U-Th isochron age. When minimum estimates of surface erosion based on flow morphology are considered, the 3He concentrations indicate a minimum exposure age of 60 ka, in good agreement with the U-Th isochron age, with a minimum erosion rate of 1.7 mm/k.y. and an erosion rate as high as 5 mm/k.y. in other locations. Correcting for erosion has little effect on the model 36Cl age and, as a result, the 36Cl age is significantly younger than the U-Th isochron age and erosion-corrected 3He ages; this discordance is attributed to a lack of closed-system behavior in the 36Cl system. These new ages have local significance for the geochronology of the Zuni-Bandera volcanic field; however, their larger significance is in their applicability to dating Quaternary basalts and quantifying erosion rates.

Sims, Kenneth W. W.; Ackert, Robert P., Jr.; Ramos, Frank C.; Sohn, Robert A.; Murrell, Michael T.; Depaolo, Donald J.

2007-05-01

8

U-series disequilibria in Guatemalan lavas, crustal contamination, and implications for magma genesis along the Central American subduction zone  

Microsoft Academic Search

New U-series results indicate that Guatemalan volcanic rocks display both 238U and 230Th excesses. 230Th excess is restricted to volcanoes in central Guatemala, both along and behind the front. 230Th excess correlates with a number of incompatible element ratios, such as Th\\/Nb and Ba\\/Th. It also shows a negative correlation with MgO. Guatemalan volcanic rocks have (230Th\\/232Th) ratios that overlap

James A. Walker; J. Erik Mickelson; Rebecca B. Thomas; Lina C. Patino; Barry Cameron; Michael J. Carr; Mark D. Feigenson; R. Lawrence Edwards

2007-01-01

9

Are U-Series Disequilibria Transparent to Crustal Processing of Magma? A Case Study at Bezymianny and Klyuchevskoy Volcanoes, Kamchatka, Russia  

NASA Astrophysics Data System (ADS)

Disequilibria in the short-lived uranium-series isotopic system can provide timescales of magma production, modification and transport in all tectonic settings. In volcanic arcs, the field has converged on the concept that (238U/230Th) and (226Ra/230Th) activities greater than one are a result of fluid fluxing from the slab to mantle wedge, and that the preservation of (226Ra/230Th) disequilibria requires rapid transport of melts from the mantle wedge to the surface (226Ra returns to equilibrium with 230Th in ~8000 years). The need for rapid transport coupled with the incompatibility of U-series elements suggest that U-series fractionation is not measurably affected by crustal processes. However, some well-studied arc systems, including the very productive Central Kamchatka Depression (CKD) of the Kamchatkan volcanic arc, show U-series data that are in conflict with this commonly accepted model. Our study focuses on two neighboring volcanic systems, Bezymianny and Klyuchevskoy volcanoes in the CKD. Separated by ~10km, these two systems are thought to share the same mantle source. Klyuchevskoy has primitive compositions (51-56 wt%) while Bezymianny erupts more differentiated andesites (57-63 wt% SiO2); therefore, by examining the U-series signals in these two systems it is possible to decouple a primary signal from one having undergone crustal processing. We record whole rock (238U/230Th) values for Bezymianny ranging from 0.94 to 0.96 in modern eruptive products, while (226Ra/230Th) are >1. We also observe a similar signal in older (212-6791BP) tephra deposits from Klyuchevskoy, measuring (238U/230Th) of 0.92-0.99 (unpublished data, collaborative research with the KALMAR project). (238U/230Th) <1 in arcs have mostly been reported from areas of thick continental crust (Andes; Sigmarsson et al. 1998, Garrison et al. 2006, Jicha et al. 2007) or from an arc where phases such as garnet and/or Al-rich clinopyroxene can retain a high U/Th in the crystalline residue (Jicha et al. 2009). Bezymianny and Klyuchevskoy have low Sr/Y (15.5-19.9), which precludes a significant influence of garnet in generating the observed Th-excess in the CKD. We investigate the possibility of shallow crustal processes such as fractional crystallization, and/or assimilation of local bulk rock or partial melts to fractionate U, Th, and Ra from one another. In particular, we focus on minor mineral phases, such as apatite and magnetite, which are present during early stages of differentiation (andesites) and may fractionate U from Th. We measure U and Th content in these phases in-situ by LA-ICP-MS to obtain average mineral-melt partitioning for each sample with U-series data. Using such average partition coefficients allows us to take into account variations in parameters such as temperature, pressure, and oxygen fugacity that may vary from sample to sample. This mineral trace element data is supported by bulk rock geochemistry and Pb isotope data to evaluate the effects of crustal processing on the U-series system during magma transport and storage.

Kayzar, T. M.; Nelson, B. K.; Bachmann, O.; Portnyagin, M.; Ponomareva, V.

2010-12-01

10

U-series disequilibria in Guatemalan lavas, crustal contamination, and implications for magma genesis along the Central American subduction zone  

NASA Astrophysics Data System (ADS)

New U-series results indicate that Guatemalan volcanic rocks display both 238U and 230Th excesses. 230Th excess is restricted to volcanoes in central Guatemala, both along and behind the front. 230Th excess correlates with a number of incompatible element ratios, such as Th/Nb and Ba/Th. It also shows a negative correlation with MgO. Guatemalan volcanic rocks have (230Th/232Th) ratios that overlap those of Costa Rican volcanics and are therefore considerably lower than the unusually high ratios characterizing volcanic rocks from Nicaragua. Along-arc variations in (230Th/232Th) therefore mirror those of a number of diagnostic geochemical parameters, such as Ba/La, which are symmetrical about a peak in west central Nicaragua. The one siliceous lava analyzed, from the Cerro Quemado dome complex, has a recognizable crustal imprint, distinguished, for instance, by high Th/Nb and low Ba/Th. In mafic samples, 238U excess is attributed to addition of a U-enriched fluid component from the subducting Cocos plate. Our preferred explanation for 230Th excess in Guatemalan mafic samples, on the other hand, is crustal contamination, consistent with the relatively high Th/Nb and low Ba/Th ratios in these samples. We suspect, however, that crustal contamination only exerts a sizable control over the U-series disequilibrium of mafic magmas in Guatemala, and not elsewhere along the Central American volcanic front. This agrees with previously published trace element and isotopic evidence that throughout Central America, with the exception of Guatemala, mafic magmas are largely uncontaminated by crustal material.

Walker, James A.; Mickelson, J. Erik; Thomas, Rebecca B.; Patino, Lina C.; Cameron, Barry; Carr, Michael J.; Feigenson, Mark D.; Edwards, R. Lawrence

2007-06-01

11

Petrogenesis and magma residence time of lavas from Tengchong volcanic field (China): Evidence from U series disequilibria and 40Ar\\/39Ar dating  

Microsoft Academic Search

We present U-Th disequilibria measurements as well as radiogenic and trace element data for volcanic rocks erupted over the past ~200,000 years at Tengchong volcano field (TVF), near the collisional belt of India-Asia, southwestern China. Mineral separates, matrix, and whole rock were analyzed separately by mass spectrometry for 230Th-238U disequilibria. Whole rocks are characterized by either 230Th enrichment or depletion

Fei Wang; Zicheng Peng; Rixiang Zhu; Huaiyu He; Liekun Yang

2006-01-01

12

U-series disequilibria in Kickem Jenny submarine volcano lavas: A new view of time-scales of magmatism in convergent margins  

NASA Astrophysics Data System (ADS)

We present data for U and its decay series nuclides 230Th, 226Ra, 231Pa, and 210Po for 14 lavas from Kick'em Jenny (KEJ) submarine volcano to constrain the time-scales and processes of magmatism in the Southern Lesser Antilles, the arc having the globally lowest plate convergence rate. Although these samples are thought to have been erupted in the last century, most have ( 226Ra)/( 210Po) within 15% of unity. Ten out of 14 samples have significant 226Ra excesses over 230Th, with ( 226Ra)/( 230Th) up to 2.97, while four samples are in 226Ra- 230Th equilibrium within error. All KEJ samples have high ( 231Pa)/( 235U), ranging from 1.56 to 2.64 and high 238U excesses (up to 43%), providing a global end-member of high 238U and high 231Pa excesses. Negative correlations between Sr, sensitive to plagioclase fractionation, and Ho/Sm, sensitive to amphibole fractionation, or K/Rb, sensitive to open system behavior, indicate that differentiation at KEJ lavas was dominated by amphibole fractionation and open-system assimilation. While ( 231Pa)/( 235U) does not correlate with differentiation indices such as Ho/Sm, ( 230Th)/( 238U) shows a slight negative correlation, likely due to assimilation of materials with slightly higher ( 230Th)/( 238U). Samples with 226Ra excess have higher Sr/Th and Ba/Th than those in 226Ra- 230Th equilibrium, forming rough positive correlations of ( 226Ra)/( 230Th) with Sr/Th and Ba/Th similar to those observed in many arc settings. We interpret these correlations to reflect a time-dependent magma differentiation process at shallow crustal levels and not the process of recent fluid addition at the slab-wedge interface. The high 231Pa excesses require an in-growth melting process operating at low melting rates and small residual porosity; such a model will also produce significant 238U- 230Th and 226Ra- 230Th disequilibrium in erupted lavas, meaning that signatures of recent fluid addition from the slab are unlikely to be preserved in KEJ lavas. We instead propose that most of the 238U- 230Th, 226Ra- 230Th, and 235U- 231Pa disequilibria in erupted KEJ lavas reflect the in-growth melting process in the mantle wedge (reflecting variations in U/Th, daughter-parent ratios, fO 2, and thermal structure), followed by modification by magma differentiation at crustal depths. Such a conclusion reconciles the different temporal implications from different U-series parent-daughter pairs and relaxes the time constraint on mass transfer from slab to eruption occurring in less than a few thousand years imposed by models whereby 226Ra excess is derived from the slab.

Huang, Fang; Lundstrom, Craig C.; Sigurdsson, Haraldur; Zhang, Zhaofeng

2011-01-01

13

Mantle melting and magma supply to the Southeast Indian Ridge: The roles of lithology and melting conditions from U-series disequilibria  

Microsoft Academic Search

Intermediate-spreading Southeast Indian Ridge (SEIR) basalts display geographic gradients from 90E to 118E in Th\\/U, (230Th\\/232Th) and 238U230Th226Ra disequilibria (230Th-excesses of 1 to 21% and 226Ra-excesses of 0 to 160%). Highly correlated (238U\\/232Th) and (230Th\\/232Th) (r2=0.94) span nearly the entire global MORB range; basalts from three of four ridge morphologies form subparallel, vertically stacked arrays on an equiline diagram. (226Ra\\/230Th)

Chris J. Russo; Ken H. Rubin; David W. Graham

2009-01-01

14

Radioactive disequilibria in mineralised fracture samples from two uranium occurrences in northern Sweden  

USGS Publications Warehouse

Mineralised fractures from two uranium occurrences in northern Sweden were examined mineralogically and isotopically to establish the presence or absence of radioactive equilibrium that may indicate recent rock-water interaction processes based on the natural mobility of uranium (i.e.; during the last 0.5 Ma). The results show evidence of radioactive disequilibrium in six of the nine samples investigated. Disequilibria are attributable to solution to solid 234U recoil gain (weakly mineralised zones adjacent to the main mineralisation) and solid to solution 234U recoil loss (moderate to highly mineralised zones). The absence of significant 238U loss in the samples emphasises the reducing conditions at the sampled depths. ?? 1984.

Smellie, J. A. T.; Rosholt, J. N.

1984-01-01

15

U-Series Transport Studies at the Pena Blanca, Mexico Natural Analog Site  

SciTech Connect

Natural analogs provide a line of evidence that supports the understanding of how natural and engineered processes would occur over long time frames and large spatial scales at a potential nuclear waste repository at Yucca Mountain, Nevada. Studies of U-series disequilibria within and around uranium deposits can provide valuable information on the timing of actinide mobility and hence the stability of a potential repository over geologic time scales. The Nopal I uranium deposit at Pena Blanca, Mexico, is situated in unsaturated tuff that is similar in composition to the Topopah Spring Tuff of Yucca Mountain and closely matches other evaluation criteria for suitable natural analogs. By modeling the observed radioactive isotope disequilibria at Nopal I, we can estimate the rates of sorption-desorption and dissolution-precipitation of the radionuclides over time. Such information is vital to the testing or validation of performance assessment models for geologic nuclear waste disposal.

A. M. Simmons; M. T. Murrell

2001-05-31

16

Magma dynamics at Mt Etna: Constraints from U-Th-Ra-Pb radioactive disequilibria and Sr isotopes in historical lavas  

Microsoft Academic Search

238U-230Th-226Ra-210Pb disequilibria and87Sr\\/86Sr ratios have been measured in a suite of prehistoric and historical lava flows from Mt. Etna. Whereas Th isotope ratios remain nearly constant during the whole period studied,226Ra and87\\/Sr86Sr data allow us to distinguish two mainepisodes in the volcanic history.For most of the past two millenia until 1970 A.D., Ra and Ba exhibit a similar behaviour (decreasing

Michel Condomines; Jean-Claude Tanguy; Valerie Michaud

1995-01-01

17

Uraanisarjojen radioaktiivisten epaetasapainojen kvantitatiivisesta tulkinnasta. (Quantitative interpretation of uranium series disequilibria).  

National Technical Information Service (NTIS)

The quantitative interpretation of radioactive disequilibria developed between radionuclides in natural decay chains has been discussed. Due to the wide spectrum of radioactive half lives of the member nuclides, uranium series can retain information long ...

K. Rasilainen J. Suksi

1992-01-01

18

U-series disequilibria in early diagenetic minerals from Lake Magadi sediments, Kenya: Dating potential  

Microsoft Academic Search

At the southern end of the Gregory Rift Valley, Lake Magadi occupies the bottom of a relatively large drainage basin. It is presently covered by a thick trona crust, which overlies two silty-clay units deposited during Late Pleistocene high lake stands. These units consist of a mixture of detrital grains (anorthoclase, amphiboles, quartz), clays (illite, authigenic zeolites), phosphates, and sedimentary

Christian Goetz; Claude Hillaire-Marcel

1992-01-01

19

Timescales of magma degassing Insights from U-series disequilibria, Mount Cameroon, West Africa  

NASA Astrophysics Data System (ADS)

Short-lived uranium-series isotope data from rocks erupted under explosive and effusive regimes are presented and used to provide constraints on the timescales of magmatic degassing and volatile fluxing during the 1999 and 2000 AD eruption of Mt. Cameroon. In contrast to the relatively homogenous major and trace element data of the analysed rocks, volcanic rocks from Mt. Cameroon reveal a spread of 230Th226Ra isotope data. Volcanic rocks erupted along the southwest rift in 1999 have (226Ra/230Th) ratios of ~ 1.25, whereas rocks erupted more axially in 2000 have relatively low (226Ra/230Th) ratios of 1.091.2 and concomitant low Ba/Th ratios. These differences imply separate magma chamber systems and probably reflect differences in the concentrations of water within the primary magmas, which led to different amounts of amphibole fractionation at depth. Variations in the (210Pb/226Ra)0 ratios are used to track degassing or volatile accumulation within the magma system. The near equilibrium (210Pb/226Ra) values for effusively erupted rocks from Mt. Cameroon suggest that this magma resided for more than several decades and less than a few thousand years before it erupted. The small excesses of 210Pb over 226Ra in some samples indicate that some of this magma was fluxed by a Rn-bearing gaseous phase for weeks to years before the eruption. In contrast, most explosively erupted rocks from Mt. Cameroon have deficits of 210Pb relative to 226Ra that require years to decades of degassing before eruption. We suggest that the magmas erupted as scoria at Mt. Cameroon degassed as they rose from lithospheric depths. Deep degassing was CO2-dominated, whereas shallower magma degassing involved more water and crystallisation of an anhydrous mineral assemblage.

Turner, M. B.; Reagan, M. K.; Turner, S. P.; Sparks, R. S. J.; Handley, H. K.; Girard, G.; Suh, C. E.

2013-07-01

20

U-Series Disequilibria in Soils, Pena Blanca Natural Analog, Chihuahua, Mexico.  

National Technical Information Service (NTIS)

The Nopal I uranium deposit located in the Sierra Pena Blanca, Mexico. The deposit was mined in the early 1980s, and ore was stockpiled close by. This stockpile area was cleared and is now referred to as the Prior High Grade Stockpile (PHGS). Some of the ...

A. Elizabeth F. Diana G. Philip

2006-01-01

21

U-series disequilibrium constraints on the origin of adakites  

NASA Astrophysics Data System (ADS)

No consensus has been reached concerning the origin of adakites that represent a subgroup of calk-alkaline lavas formed at convergent margins. The particular composition of these adakites is ascribed to the role of garnet in fractionating key trace element ratios. However, it is not clear if garnet is a residual phase during slab melting, lower crustal melting or a fractionating phase from a parental basaltic liquid. Here, we present U-series criteria that allow clear distinction between different petrogenetic processes for this particular type of magma. Adakites from several volcanoes of the Austral Volcanic Zone (S-Chile), under which a young and hot oceanic crust is slowly subducted, have been shown to have constant 230Th-excess over 238U ascribed to partial slab melting with eclogitic residue. In marked contrast, historical adakites from the Guagua Pichincha volcano (Ecuador), above the subducting Galapagos Ridge, all display 238U- and 226Ra excesses over 230Th (max 45% and 26%, respectively). As in the case of most arc lavas, such 230Th deficit is readily explained by important fluid-addition of U and Ra. Hydrous flux melting of the mantle wedge would generate water-rich basalts that upon fractional crystallisation can form the adikites in Ecuador. Moreover, the amount of fluid recorded by the U-Ra-Th systematics in Guagua Pichincha magmas can be shown to increase towards the present, and consequently the potential explosivity of the erupted magma. In summary, U-series disequilibria seem to be a good tracer for the origin of adakites that clearly can be formed in more than one way.

Sigmarsson, O.; Chmeleff, J.

2009-12-01

22

U-series dating of Lake Nyos maar basalts, Cameroon (West Africa): Implications for potential hazards on the Lake Nyos dam  

Microsoft Academic Search

From previously published 14C and KAr data, the age of formation of Lake Nyos maar in Cameroon is still in dispute. Lake Nyos exploded in 1986, releasing CO2 that killed 1750 people and over 3000 cattle. Here we report results of the first measurements of major elements, trace elements and U-series disequilibria in ten basanites\\/trachy-basalts and two olivine tholeiites from

Festus T. Aka; Tetsuya Yokoyama; Minoru Kusakabe; Eizo Nakamura; Gregory Tanyileke; Bekoa Ateba; Vincent Ngako; Joseph Nnange; Joseph Hell

2008-01-01

23

Time scale and conditions of weathering under tropical climate: Study of the Amazon basin with U-series  

NASA Astrophysics Data System (ADS)

The Rio Solimes/Amazonas (Amazon River) and its major tributaries have been analyzed for U-series nuclides. 238U 234U 230Th 226Ra disequilibria have been measured in the dissolved (<0.2 ?m) and suspended loads (>0.2 ?m) as well as bed sands. U-series disequilibria are closely related to major and trace element compositions and therefore reflect elemental fractionation during chemical weathering. Moreover, while the dissolved load records present-day weathering, suspended particles integrate the erosion history over much longer time scales (>100 ka). Lowland rivers are characterized by long time scales of chemical erosion (?100 ka) resulting in a high weathering intensity. Moreover, exchange between suspended particles and the dissolved load may explain the U-series signature for these rivers. By combining U-series and Pb isotopes in suspended particles, we show that erosion in the Rio Madeira basin occurred as a multi-step process, whereby the pristine continental crust was eroded several hundreds of Ma ago to produce sediments that have then been integrated in the Cordillera by crustal shortening and are currently eroded. In contrast, recent erosion of a pristine crust is more likely for the Rio Solimes/Amazonas (<10 ka). The suspended particles of the rivers draining the Andes (Solimes/Amazonas, Madeira) suggest time scales of weathering ranging between 4 and 20 ka. This indicates that suspended particles transported by those rivers are not stored for long periods in the Andean foreland basin and the tropical plain. The sediments delivered to the ocean have resided only a few ka in the Amazon basin (6.3 1 ka for the Rio Amazonas at bidos). Nevertheless, a large fraction of the sediments coming out from the Andes are trapped in the foreland basin and may never reach the ocean. Erosion in the Andes is not operating in steady state. U-series systematics shows unambiguously that rivers are exporting a lot more sediments than predicted by steady-state erosion and that is a consequence of soil destruction greater than production. By relating this observation to the short time scales of weathering inferred for the Andes (a few ka), it appears that the erosion regime has been recently perturbed, resulting in high denudation rates. A possible explanation would be the increase in precipitation less than 5 ka proposed by recent paleoclimatic studies. Our results indicate that erosion responds rapidly to high-frequency climatic fluctuations.

Dosseto, A.; Bourdon, B.; Gaillardet, J.; Allgre, C. J.; Filizola, N.

2006-01-01

24

Minimum speed limit for ocean ridge magmatism from 210Pb-226Ra-230Th disequilibria.  

PubMed

Although 70 per cent of global crustal magmatism occurs at mid-ocean ridges-where the heat budget controls crustal structure, hydrothermal activity and a vibrant biosphere-the tempo of magmatic inputs in these regions remains poorly understood. Such timescales can be assessed, however, with natural radioactive-decay-chain nuclides, because chemical disruption to secular equilibrium systems initiates parent-daughter disequilibria, which re-equilibrate by the shorter half-life in a pair. Here we use 210Pb-226Ra-230Th radioactive disequilibria and other geochemical attributes in oceanic basalts less than 20 years old to infer that melts of the Earth's mantle can be transported, accumulated and erupted in a few decades. This implies that magmatic conditions can fluctuate rapidly at ridge volcanoes. 210Pb deficits of up to 15 per cent relative to 226Ra occur in normal mid-ocean ridge basalts, with the largest deficits in the most magnesium-rich lavas. The 22-year half-life of 210Pb requires very recent fractionation of these two uranium-series nuclides. Relationships between 210Pb-deficits, (226Ra/230Th) activity ratios and compatible trace-element ratios preclude crustal-magma differentiation or daughter-isotope degassing as the main causes for the signal. A mantle-melting model can simulate observed disequilibria but preservation requires a subsequent mechanism to transport melt rapidly. The likelihood of magmatic disequilibria occurring before melt enters shallow crustal magma bodies also limits differentiation and heat replenishment timescales to decades at the localities studied. PMID:16177787

Rubin, K H; van der Zander, I; Smith, M C; Bergmanis, E C

2005-09-22

25

Uranium and thorium decay series disequilibria in young volcanic rocks  

SciTech Connect

Two of the central questions in igneous geochemistry that study of radioactive disequilibria can help to answer are: what are the rates of magma genesis; and what are the timescales of magma separation and transport. In addition to the temporal information that may be extracted from disequilibria data, the {sup 230}Th/{sup 232}Th of a young rock may be used as a tracer of the Th/U ratio of its source region. Measurements were made by isotope dilution alpha-spectrometry of {sup 238}U, {sup 234}U, {sup 230}Th, and {sup 232}Th in 20 subduction related, 3 oceanic intraplate, and 10 continental intraplate volcanics. {sup 210}Pb was measured in all, {sup 226}Ra was measured in about half, and {sup 228}Th was measured in 10 of the most recent samples. Disequilibrium between {sup 228}Th and {sup 232}Th was found only in the Nacarbonatite samples from Oldoinyo Lengai volcano in Tanzania, which is attributable to {sup 228}Ra/{sup 232}Th {approximately} 27 at the time of eruption. These rocks also have {sup 226}Ra/{sup 230}Th > 60. Three Ra-enrichment models are developed which constrain carbonatite magma formation at less than 20 years before eruption. The effects of different partial melting processes on the {sup 238}U decay series are investigated. If mid-ocean ridge basalts are formed by a dynamic melting process, the {sup 230}Th/{sup 232}Th of the basalts provides a minimum estimate of the Th/U ratio of the source region. The {sup 238}U enrichment in arc volcanics is probably the results of metasomatism of the source by fluids derived from the subducting slab, and the {sup 230}Th enrichment observed for other volcanics is probably due to the partial melting process in the absence of U-bearing fluids.

Williams, R.W.

1988-01-01

26

Integration of U-Series and Os Isotopic Data From the Azores: Insights Into Processes Controlling the Generation and Transport of Melt Within the Mantle beneath Ocean Island Volcanoes  

NASA Astrophysics Data System (ADS)

We observe broad correlations between U-series (specifically Th- and Ra disequilibria) isotopes and the spatial variations in likely melt source isotopic domains defined by Os isotopes beneath the Azores archipelago. More specifically, the central islands of the archipelago (Faial, Terceira and Sao Jorge); which preserve a previously reported unradiogenic (subchondritic) Os isotopic component also record correlated Os- U-series disequilibria, implying that the compositional variation at depth beneath the centre of the plume is exerting some control on melt generation and extraction processes. Significantly, simple diffusive transfer modelling suggests that in order to preserve such highly unradiogenic Os isotopic signatures through the melting process to the surface, a rapid transition from porous flow of melts through asthenospheric mantle to channel flow must take place. The length scale for this transition must be of the order of millimetres. If porous flow was dominant for longer length scales, then we would predict that the highly unradiogenic Os isotopic signature would rapidly become homogenesied with that of the surrounding asthenospheric mantle. Ra disequilibria suggest that this is likely to occur on time scales of between 100- 1000 years.

Schaefer, B. F.; Turner, S. P.

2006-12-01

27

How precise are U-series coral ages?  

Microsoft Academic Search

U-series dating of fossil reef corals is a well established and widely applied technique in paleoclimate research. Many fossil corals, however, show evidence for post-depositional diagenetic alteration, and it is generally accepted that the accuracy of U-series coral ages is more limited due to coral diagenesis than analytical precision. In recent years, three models have been published that try to

Denis Scholz; Augusto Mangini

2007-01-01

28

U-series disequilibrium in arc magmas induced by water-magma interaction  

NASA Astrophysics Data System (ADS)

Volcanic rocks from subduction zones are widely believed to originate by partial melting of mantle lherzolite modified by the addition of a fluid or melt extracted from the down-going slab. U-series disequilibrium in such magmas is commonly attributed to this particular melting process. A detailed study of U-series isotopes in the 650 y. B.P. eruptive sequence of Mt. Pele (Martinique) shows that plinian products are in radioactive equilibrium, whereas dome-forming products of the same eruption are characterized by 238U- 230Th disequilibrium. The same features apply to other plinian and dome-forming products of this volcano and systematically correspond to different eruptive styles. We attribute these characteristics to variable superficial interaction of magmas with the hydrothermal system during the final stages of eruption rather than to deep magma genesis processes. This conclusion might be generally applicable to arc magmas.

Villemant, Benot; Boudon, Georges; Komorowski, J.-C.

1996-05-01

29

U-series disequilibrium of basaltic rocks from Kick'em-Jenny submarine volcano, Lesser Antilles island arc  

NASA Astrophysics Data System (ADS)

Kick'em Jenny (KEJ) submarine volcano located 9 km to the north of Grenada in the Lesser Antilles volcanic arc produces lavas ranging in composition from high MgO basalts to moderately evolved andesites. We have determined U-series disequilibria in 12 porphyritic lavas erupted from KEJ volcano by TIMS and MC-ICP-MS methods to constrain the timing and identify the processes creating the magma diversity observed. The SiO2 contents of samples studied here vary from 47 to 55 wt.% SiO2 while REE patterns evolve from slightly LREE enriched, MREE/HREE = 1 patterns to strongly LREE enriched, MREE depleted concave-up patterns. Separate dissolutions of sample KEJ100 indicate an external reproducibility (1s) of 0.7% for (230Th/238U) (n=4), 0.8% for (230Th/232Th) (n=4) and 0.6% for (226Ra/230Th) (n=3), respectively. For all sample, (234U/238U) lies within 0.7% of unity, suggesting that secondary alteration by seawater has not disturbed the U-series data significantly. Sample ages for these submarine erupted samples are unknown, resulting in uncertain values for initial (226Ra/230Th); however, 10 out of 12 of the measured (226Ra/230Th) range between 3.16 and 1.13 and are thus unequivocally young with respect to decay of 230Th and 231Pa since eruption. The U (0.535 - 4.876 ppm) and Th (1.25 - 10.78 ppm) concentrations increase with SiO2 contents. (230Th/232Th) has a restricted range, varying from 0.994 to 1.093 with the exception of one sample. (230Th/238U) ranges from 0.684 to 0.875 while (231Pa/235U) ranges from 1.76 up to 2.84, among the highest 231Pa excess in island arcs yet reported. These data confirm previous observations of the unusual behavior of KEJ lavas relative to global observations in having both large 238U and 231Pa excesses. Combined with (226Ra/230Th), these disequilibria observations require that 238U excesses reflect more than solely fluid addition to the mantle wedge from the subducted oceanic slab.

Huang, F.; Lundstrom, C. C.

2005-12-01

30

Theoretical studies of {sup 238}U-{sup 230}Th-{sup 226}Ra and {sup 235}U-{sup 231}Pa disequilibria in young lavas produced by mantle melting  

SciTech Connect

This paper provides ready-to-use equations to describe variations in uranium-series (U-series) disequilibrium as a function of elemental distribution coefficients, melting porosity, melting rate, and melting time. The effects of these melting parameters on U-series disequilibria are quantitatively evaluated in both an absolute and relative sense. The importance of net elemental fractionation and ingrowth of daughter nuclides are also described and compared in terms of their relative contributions to total U-series disequilibrium. In addition, the authors compare the production of U-series disequilibrium during mantle melting to trace element fractionations produced by melting in a similar context. Trace element fractionations depend externally on the degree to which a source is melted, whereas U-series disequilibrium depends upon both the degree and rate of melting. In contrast to previous models, their approach to modeling U-series disequilibrium during dynamic melting collapses simply to a description of trace element behavior during dynamic melting when the appropriate decay terms are omitted. Their formulation shows that extremely small degrees of melting, sometimes called upon to explain observed extents of U-series disequilibrium, are not always required.

Zou, H.; Zindler, A.

2000-05-01

31

Plume-ridge interaction studied at the Galpagos spreading center: Evidence from 226Ra- 230Th- 238U and 231Pa- 235U isotopic disequilibria  

NASA Astrophysics Data System (ADS)

New 238U- 230Th- 226Ra and 231Pa- 235U disequilibria data measured by TIMS are presented for ridge-centered MORB glasses dredged during the R/V Sonne 158 cruise at the Galpagos or Cocos-Nazca Spreading Center (GSC) between 86.0W and 92.3W. The application of U-series isotopes to the GSC region, situated a few hundred kilometres to the north of the Galpagos hotspot, allows assessment of fundamental questions related to the dynamics of plume-ridge interaction. These include (1) the relationship between long-lived source variations, U-series disequilibria and extent of differentiation, (2) partial melting during solid upwelling, and (3) the nature and rates of plume-ridge mass transfer. The along axis U-series disequilibria variation show gradational patterns that locally are correlated with geochemical and isotopic parameters such as La/Sm, Tb/Yb, 206Pb/ 204Pb and 143Nd/ 144Nd as well as major element compositions. The correlation of ( 230Th)/( 238U) with radiogenic isotopes and Tb/Yb provides constraints on the plume source influence on the melting process, reflecting an increase in the amount of melting at depth in the presence of garnet or aluminous clinopyroxene. Moreover, the correlation between U-series signatures, radiogenic isotopes, incompatible element abundance and MgO content indicates a causative relationship between the melting of plume source materials and how these lavas differentiate at shallow depths. We speculate that this involves loss of alkalis from ascending melts to shallow peridotite and crustal gabbro, resulting in increased olivine fractionation from the magmas. The U-series data place stringent constraints on the timing of plume-ridge mass transfer and thus distinguish whether mass transfer occurs by movement of melts or solid mantle. Within the likely conditions proposed by the model of (Braun and Sohn [EPSL 213 (2003): 417-430] and with knowledge of ( 231Pa)/( 235U) and ( 230Th)/( 238U) observed in Galpagos Islands lavas [A. Saal, personal communication], we show that all 226Ra excess will be lost and the initial 231Pa and 230Th excesses will be largely decayed. Therefore, we conclude that the plume influence on the GSC lavas results from a solid mantle flow process instead of through migration of plume-derived melts to the ridge.

Kokfelt, Thomas Find; Lundstrom, Craig; Hoernle, Kaj; Hauff, Folkmar; Werner, Reinhard

2005-05-01

32

Vadose Zone Weathering Rates Inferred from U-Series Disequilibrium  

Microsoft Academic Search

The U-series isotope system can be used to quantify reaction rates in aquifers and thick vadose zone environments. The approach is based on the alpha -recoil of 234Th atoms across grain boundaries, which enriches the pore fluid in 234U. Dissolution of the solid phase releases mainly 238U to the pore fluid, so that the 234U\\/238U activity ratio of the pore

K. Maher; D. J. Depaolo; C. Steefel; J. N. Christensen

2003-01-01

33

234Th:238U disequilibria within the California Current  

Microsoft Academic Search

Profiles of dissolved and particulate 234Th were determined at several stations within the Cali- fornia Current. Modeling of the disequilibria between the 234Th and 23aU within the surface waters provides for estimates of the residence time of dissolved thorium with respect to particle scavenging (TP varies from 6 to 50 days), the particle residence time (TP varies from 2 to

KENNETH H. COALE; KENNETH W. BRULAND

1985-01-01

34

U-series constraints on mantle melting in the Manus back-arc basin  

NASA Astrophysics Data System (ADS)

Although studies have used U-series isotopes to constrain mantle melting processes beneath mid-ocean ridges, there have been far fewer investigations of back-arc basins, the nature of melting processes there and the role of subduction components from the nearby arc. Lavas dredged from the Manus back-arc basin, located behind the New Britain island arc in Papua New Guinea, display a large diversity of compositions ranging from normal depleted MORB and transitional MORB to typical Back arc basin basalts (BABB) and even extremely enriched BABB (XBABB). We have analysed U-Th-Ra disequilibria in Manus back-arc basin lavas that have previously been analysed for major and trace elements and Sr-Nd-Pb isotope ratios [1]. While most display (230Th/238U) ratios of 0.77-0.95 (brackets indicate activity ratios) a few lavas from the northerly Manus spreading centre and north of the East Rift have small Th excesses with (230Th/238U) < 1.06. (226Ra/230Th) ratios are generally > 1 implying that the lavas are < 8ka old and that no post-eruptive age correction needs to be applied for the U-Th data. The (230Th/238U) ratios do not change systematically with distance from the arc, i.e. we do observe U and Th excess at locations both closer and farther from the arc. However, with increasing distance from the arc, (230Th/232Th), U/Th and Ba/Th all decrease, while Yb concentrations and the Ce/Pb ratios generally increase. We also observe a slight increase of 87Sr/86Sr ratios and decrease of 143Nd/144Nd ~ 200-300 km from the active trench. The combined behaviour of U/Th and Ba/Th provides evidence that the influence of the U-rich 'arc' fluid decreases with increasing distance to the trench, while Ce/Pb ratios indicate that a depleted normal MORB-mantle becomes more important to the north. The zone of higher Sr and lower Nd isotope ratios most likely reflects an increased contribution from the subducted slab, while the relatively depleted isotopic ratios reflect melting of the depleted mantle wedge. The presence of (230Th/238U) < 1 and a decrease of magnitude of U excess with distance from the arc imply that a subduction component becomes less influential with increased distance but still may influence melting process on the order of many 100 kms behind the arc front. 1. Sinton, J.M., et al., Magma genesis and mantle heterogeneity in the Manus back-arc basin, Papua New Guinea. Journal of Petrology, 2003. 44(1): p. 159-195.

Beier, C.; Turner, S. P.; Bach, W.; Niedermeier, D.; Sinton, J.; Gill, J. B.

2008-12-01

35

Modeling U-Series Concordia/Discordia Using STELLA  

NSDL National Science Digital Library

U-Series dating techniques are widely used to determine the absolute ages of some of Earth's oldest rocks, but the concordia/discordia diagram can be quite difficult for students to grasp. In particular, the fact that differing amounts of lead and uranium loss from minerals such as zircon can be used to determine not only the original formation age, but also the time of metamorphism of a rock like granite, is a challenging concept. Making use of previous workers' web-published excercises on radiometric decay, I have produced a STELLA-based lab exercise to develop students' understanding of this important chronologic technique. Students create models of the two isotopic decay systems, 238U --> 206Pb and 235U --> 207Pb, and run these models for 4.5 billion years to create the concordia diagram. They then carry out experiments in which they "add" or "remove" varying amounts of lead or uranium in simulation of metamorphism. The uranium-lead ratios at the end of the simulation allow the discordia line to be plotted on top of the concordia diagram and the ages of original crystallization and metamorphism to be determined from the points of intersection of the two lines. In the course of the lab, students are introduced to the concepts of exponential decay and secular equilibrium as well as modeling concepts such as the creation of if-then statements.

Menking, Kirsten

36

Methods for obtaining sorption data from uranium-series disequilibria  

SciTech Connect

Two possible methods have been identified for obtaining in situ retardation factors from measurements of uranium-series disequilibria at Yucca Mountain. The first method would make use of the enhanced {sup 234}U/{sup 238}U ratio in groundwater to derive a signature for exchangeable uranium sorbed on the rock; the exchangeable uranium would be leached and assayed. The second method would use the ratio of {sup 222}Rn to {sup 234}U in solution, corrected for weathering, to infer the retardation factor for uranium. Similar methods could be applied to thorium and radium.

Finnegan, D.L.; Bryant, E.A.

1987-12-01

37

Measuring U-Series Isotopes in Polar Ice: Toward an Absolute Ice Chronometer  

Microsoft Academic Search

Comparison of ice records between ice sheets, alpine glaciers, and marine records currently rely on a combination of ice layer counting, matching relative time scales, and interpolation. U-series recoil from mineral aerosols (dust) into the ice matrix is one possible technique for determining the absolute age of ice, independent of any other parameters. However, the low concentrations of the U-series

S. M. Aciego; B. Bourdon; J. Schwander; T. Stocker

2007-01-01

38

Disequilibrium of the 238U series in basalt  

USGS Publications Warehouse

Radioisotope analyses of basalt samples from Hawaii, Japan, and Iwo Jima show that: (1) 234U and 238U are virtually in radioactive equilibrium, (2) 230Th exceeds equilibrium values in all these samples, (3) 210Pb concentrations range from 10-200% of the equilibrium values and average 30% deficient, and (4) 226Ra is probably not in equilibrium with 234U. The source regions of the basalts or magma forming processes are open systems, chemically. The enrichment of some of the uranium-daughter nuclides is insufficient to account for the excess 206Pb in volcanic rocks. The isotopic composition of lead and specific activity of 210Pb in sublimates from Showa-shinzan, Japan are also reported. ?? 1966.

Somayajulu, B. L. K.; Tatsumoto, M.; Rosholt, J. N.; Knight, R. J.

1966-01-01

39

Upwelling Rates Beneath Hotspots : Evidence From U-Series in Basalts From the Mid-Atlantic Ridge and the Azores Islands  

NASA Astrophysics Data System (ADS)

In this study, we have analyzed U-series in lavas from the Azores islands and the nearby Mid-Atlantic Ridge (FAZAR cruise) in an attempt to assess the relative importance of melting processes versus source variations in the context of ridge-hotpsot interaction. The lavas were analyzed for 238U-230Th (Turner et al. 1997, Bourdon et al. 1996) 226Ra-230Th and 235U-231Pa disequilibria by thermal ionisation mass spectrometry. Our results for the historic lavas from the Azores islands show that the 231Pa excess are at the low end of the trend found for other OIB (Pickett et al. 1997 and Bourdon et al. 1998) and fall on a positive correlation in a 231Pa/235U versus 230Th/238U diagram. In contrast, lavas from the nearby Mid-Atlantic ridge are characterized by larger (231Pa/235U) activity ratios for similar and greater (230Th/238U) ratios. There is also a weak correlation between 226Ra/230Th and 231Pa/235U. These data do not indicate a simple mixing trend between an N-MORB and an enriched component in the 231Pa/235U versus 230Th/238U diagram since the MORBs which do not have the most radiogenic isotope signatures compared with the Azores island basalts have some of the largest (230Th/238U) and 231Pa/235U. Clearly, the dynamics of melting must have played a role in generating larger 230Th and 231Pa excesses beneath the Mid-Atlantic ridge. We infer that this must be due to the absence of a lithospheric lid as larger excesses of 230Th and 231Pa can be generated for longer melting columns. Thus, ridge-hotspot interaction cannot imply a simple transfer of melt from the hotspot to the ridge. The 230Th/238U and 226Ra/230Th data across the Azores plateau shows a maximum for the island of Terceira and mimics the depth anomaly which is thought to result from the hotspot. This trend is also consistent with observations of rare gases (M. Moreira pers. comm.) and suggests that it must be related to the presence of deep material. The U-series trend is the reverse of the trend found in Hawaii by Sims et al. (2000) which was attributed to variations in upwelling rates across the rising plume. This observation can be rationalized in the context of an equilibrium melt transport model (Spiegelman and Elliott, 1993) where U-series disequilibria are sensitive to upwelling rates. For slow upwelling rates such as below the Azores, larger 230Th excesses are predicted in the center of the plume. This suggests that the upwelling rate beneath the center of the plume must be of the order of a few cm per year which is an order of magnitude lower than values estimated for Hawaii. Turner et al. 1997, Chem. Geol. 139, 145-164. Bourdon et al. 1996, Earth Planet. Sci. Lett. 142, 175-189. Pickett et al. 1997, Earth Planet. Sci. Lett. 148, 259-271. Sims et al. 1999, Geochim. Cosmochim. Acta. 63, 4119-4138. Spiegelman and Elliot, 1993, Earth Planet. Sci. Lett., 118, 1-20.

Bourdon, B. P.; Turner, S. P.

2001-12-01

40

Evaluation of Pleistocene groundwater flow through fractured tuffs using a U-series disequilibrium approach, Pahute Mesa, Nevada, USA  

USGS Publications Warehouse

Groundwater flow through fractured felsic tuffs and lavas at the Nevada National Security Site represents the most likely mechanism for transport of radionuclides away from underground nuclear tests at Pahute Mesa. To help evaluate fracture flow and matrixwater exchange, we have determined U-series isotopic compositions on more than 40 drill core samples from 5 boreholes that represent discrete fracture surfaces, breccia zones, and interiors of unfractured core. The U-series approach relies on the disruption of radioactive secular equilibrium between isotopes in the uranium-series decay chain due to preferential mobilization of 234U relative to 238U, and U relative to Th. Samples from discrete fractures were obtained by milling fracture surfaces containing thin secondary mineral coatings of clays, silica, FeMn oxyhydroxides, and zeolite. Intact core interiors and breccia fragments were sampled in bulk. In addition, profiles of rock matrix extending 15 to 44 mm away from several fractures that show evidence of recent flow were analyzed to investigate the extent of fracture/matrix water exchange. Samples of rock matrix have 234U/238U and 230Th/238U activity ratios (AR) closest to radioactive secular equilibrium indicating only small amounts of groundwater penetrated unfractured matrix. Greater U mobility was observed in welded-tuff matrix with elevated porosity and in zeolitized bedded tuff. Samples of brecciated core were also in secular equilibrium implying a lack of long-range hydraulic connectivity in these cases. Samples of discrete fracture surfaces typically, but not always, were in radioactive disequilibrium. Many fractures had isotopic compositions plotting near the 230Th-234U 1:1 line indicating a steady-state balance between U input and removal along with radioactive decay. Numerical simulations of U-series isotope evolution indicate that 0.5 to 1 million years are required to reach steady-state compositions. Once attained, disequilibrium 234U/238U and 230Th/238U AR values can be maintained indefinitely as long as hydrological and geochemical processes remain stable. Therefore, many Pahute Mesa fractures represent stable hydrologic pathways over million-year timescales. A smaller number of samples have non-steady-state compositions indicating transient conditions in the last several hundred thousand years. In these cases, U mobility is dominated by overall gains rather than losses of U.

Paces, James B;Nichols, Paul J;Neymark, Leonid A.;Rajaram, Harihar

2013-01-01

41

The Times Scale of Andesite Differentiation at Arenal Volcano, Costa Rica (1968-2003), Indicated by U-Th-Ra Disequilibria.  

NASA Astrophysics Data System (ADS)

Arenal Volcano in Costa Rica has continuously erupted since 1968 evolving in a complex fashion involving crystal fractionation, magma mixing, degassing, and wall-rock interaction (Reagan et al., 1987; Cigolini, 1998). We have measured trace-element concentrations and U-series disequilibria in whole rocks and mineral separates (pyroxene, plagioclase, magnetite) over the course of the eruption from 1968 to 2003 by ICP-MS, TIMS and PIMMS techniques. Whole rock and mineral separate analyses (n>20) show only minor variation in (230Th)/(232Th) (1.10 to 1.18). In contrast, (230Th)/(238U) range from 0.91 to 1.04 reflecting the moderate spread in Th/U. Th/U consistently change from low values in the early samples (2.4) to a constant, higher value from 1986 to present (2.65). The observed U-Th disequilibria are consistent with a time scale of mineral formation being much less than that of 230Th decay (<104 years -they are not old xenocrysts) for all samples in the study. A further implication is that mantle-derived recharge magmas entering the Arenal magma chamber either have changed through time from more U-enriched to less U-enriched, or that assimilation has changed the Th/U of the system but not (230Th)/(232Th) (but the assimilant has to be very young Arenal cumulates or fortuitously have the same (230Th)/(232Th)). Ra isotope data are being analyzed to evaluate whether differentiation and mineral formation in this system operate on a time scale closer to the half life of Ra (1600 years).

Tepley, F. J.; Lundstrom, C. C.; Williams, R. W.; Murrell, M. T.; Goldstein, S. J.

2004-12-01

42

234U/238U Disequilibria along sedimentary discontinuities in a deep formation: late diagenetic U-relocation processes vs. large scale fluid circulation evidence ?  

NASA Astrophysics Data System (ADS)

This work is part of geological investigations undertaken by the French Agency for Nuclear Waste Management (ANDRA) in order to study the safety of radioactive waste repository in deep geological clay layers. The target formation, from Mesozoic sedimentary rocks of the eastern Paris basin (France), is a thick (130--145 m), 400--500 m deep, Callovo-Oxfordian argilite unit, that is over- and underlain by Oxfordian and Bathonian limestones, respectively. Borehole core samples have been analysed for their uranium content and 234U/238U isotopic composition in order to examine the state of radioactive equilibrium existing between these two radionuclides naturally occurring in the rock. Any observations of disequilibrium should allow i) to document the mobility of these actinides in such deposits, and ii) to constrain the time scale of the geological phenomena responsible for it. Highly precise and accurate (234U/238U) analyses were obtained using Multiple Collector Inductively Coupled Plasma Mass Spectrometry. The overall reproducibility, including both chemical separation and spectrometric measurement, is about 0.15% (2?). Most samples of the target formation and its bounding rocks display secular equilibrium. However, in the Bathonian formation near the interface with the argilite layer, significant (234U/238U) disequilibria are observed along sub-horizontal sedimentary discontinuities, identified as styloliths, indicating that the process involved has been active during the last Ma. Isotopic and elemental compositions of uranium have been determined along a transect, perpendicular to a major discontinuity. The transect exhibits a symmetric pattern relative to this discontinuity with: (1) an increase of the U-concentration towards the stylolitic joint and (2) a sharp transition between significant (234U/238U) < 1 disequilibria in the stylolith to an excess of 234U ((234U/238U) = 1.05) in the vicinity of the joint, followed by a smooth decrease of the activity ratio away from the suture zone. Such disequilibria are commonly attributed to water/rock interaction phenomenon related to fluid circulation. In this case, mineralogical, trace and major element data rather indicate that the mechanism responsible for these disequilibria is epidiagenetic, directly associated with the presence of the stylolith, and likely due to micro-scale relocation of highly fractionated U. Therefore, the chemical system might be seen, at a larger scale, as a closed one. However, the phenomenon responsible for the recent reactivation of the stylolitization is not determined.

Deschamps, P.; Hillaire-Marcel, C.; Michelot, J.-L.; Doucelance, R.; Ghaleb, B.

2003-04-01

43

An open-system model for U-series age determinations of fossil corals  

Microsoft Academic Search

The source of excess 234U in fossil corals and its relationship to U-series age determinations has been an outstanding problem in geochronology for more than 20 years. With increasing numbers of U-series isotope measurements in corals, and significant improvements in analytical precision through mass spectrometry, it is increasingly apparent that a substantial fraction of observed isotope ratios cannot be reasonably

William G. Thompson; Marc W. Spiegelman; Steven L. Goldstein; Robert C. Speed

2003-01-01

44

U-series constraints on the Holocene human presence in the Cuatro Cienegas basin, Mexico  

Microsoft Academic Search

U-series tufa ages dating a human trackway have been obtained, part of a larger Late Pleistocene - Recent palaeoclimate and human occupation study of the Cuatro Cienegas basin, NE Mexico. Our analytical approach, including tracer calibration, couples aspects of what we consider best practice in the U-series community with our U-Pb experiences which includes the EarthTime U-Pb tracer calibration exercise.

S. R. Noble; N. Felstead; S. Gonzalez; M. J. Leng; S. E. Metcalfe; P. J. Patchett

2010-01-01

45

Impact of the 235U series on doses from intakes of natural uranium and decay progeny.  

PubMed

The doses from 235U series radionuclides have often been ignored in dose assessments involving natural uranium and progeny. This is due to the relatively low abundance of 235U in natural uranium (less than 5% on an activity basis). However, inclusion of the 235U series radionuclides, especially 227Ac and 231Pa, in dose calculations can have a substantial impact on estimated inhalation doses. PMID:9314233

Lowe, L M

1997-10-01

46

U-series Isotopes and the Time Scales of Magmatic Processes  

NASA Astrophysics Data System (ADS)

The first published record of a radioactive decay chain was 100 years ago this year, and the sequence of isotopes in the U and Th decay chains were largely determined in the following ten years. Isotopes of U, Th, Pa, Ra and Pb with half-lives in the range 75,000 to 22 years have had a major impact in our understanding of magmatic processes, because the time scales of magmatic processes are similar to the half lives of these isotopes, and physically realistic models of natural processes require information on the rates at which those processes occur. U-Th-Pa-Ra isotopes can now be measured by mass spectrometry, routinely with errors of less than ~1%. A key characteristic is that U-series isotopes can change significantly by radioactive decay while the crystals and rocks were forming. At subduction zones fluids may be transferred from the downgoing slab in a few 1000 years. In most tectonic settings the magmas and the peridotite matrix spend different lengths of time in the melt zone, and typically the observed isotope fractionation implies some form of dynamic melting process. New U-Pa isotope data for 40 young lavas from 7 different arcs worldwide have, with one exception, (231Pa/235U) > 1, and extend to values as high as 2.48. Their U/Nb ratios are < 9.0 and so > 80% of the U has been added from the subducting slab, and large enrichments of Pa over U occurred during melting and melt transport. The ages of phenocrysts and the time scale of differentiation of the host magma can be different, and in a number of cases it has been shown that the phenocrysts formed after the fractional crystallisation responsible for the whole rock composition. Different approaches are therefore used to investigate the crystallisation history and the differentiation of magmatic suites: crystallisation rates are ~ 10-10 to 10-11 cm/s, whereas differentiation to high silica magmas may take up to 2 x 105 years. The ages of crystals at the time of eruption can range back to 2-3 x 105 years, the older ages tend to be in the more evolved rock types, and it can take 105 years for high silica magmas to be generated at individual volcanic centres. Thus, the generation of evolved magmas is often thermally controlled, and the rates of fractional crystallisation have, for example, been linked to volcanic power outputs. In contrast, crystallisation in response to magma degassing or decompression, may be too fast for much fractional crystallisation to take place.

Hawkesworth, C. J.; Peate, D. W.; Regelous, M.; Turner, S. P.; George, R. M.

2003-12-01

47

Thermal ionization mass spectrometry U-series dating of a hominid site near Nanjing, China  

NASA Astrophysics Data System (ADS)

Mass spectrometric U-series dating of speleothems from Tangshan Cave, combined with ecological and paleoclimatic evidence, indicates that Nanjing Man, a typical Homo erectus morphologically correlated with Peking Man at Zhoukoudian, should be at least 580 k.y. old, or more likely lived during the glacial oxygen isotope stage 16 (620 ka). Such an age estimate, which is 270 ka older than previous electron spin resonance and alpha-counting U-series dates, has significant implications for the evolution of Asian H. erectus. Dentine and enamel samples from the coexisting fossil layer yield significantly younger apparent ages, that of the enamel sample being only less than one-fourth of the minimum age of Nanjing Man. This suggests that U uptake history is far more complex than existing models can handle. As a result, great care must be taken in the interpretation of electron spin resonance and U-series dates of fossil teeth.

Zhao, Jian-Xin; Hu, Kai; Collerson, Kenneth D.; Xu, Han-Kui

2001-01-01

48

Oceanic stratified euphotic zone as elucidated by 234Th : 238U disequilibria  

Microsoft Academic Search

Profiles of dissolved and particulate 234Th were determined at the VERTEX 2 and 3 stations off Manzanillo, Mexico, and at the VERTEX 4 station about 900 km north of Hawaii. By modeling the disequilibria between 234Th and 238U in the dissolved and particulate form, estimates of scav- enging rates for Th from the dissolved to particulate phases, particle residence times,

KENNETH H. COALE; KENNETH W. BRULAND

1987-01-01

49

Modeling of U-series Radionuclide Transport Through Soil at Pena Blanca, Chihuahua, Mexico  

NASA Astrophysics Data System (ADS)

The Nopal I uranium deposit is located at Pena Blanca in Chihuahua, Mexico. Mining of high-grade uranium ore occurred in the early 1980s, with the ore stockpiled nearby. The stockpile was mostly cleared in the 1990s; however, some of the high-grade boulders have remained there, creating localized sources of radioactivity for a period of 25-30 years. This provides a unique opportunity to study radionuclide transport, because the study area did not have any uranium contamination predating the stockpile in the 1980s. One high-grade boulder was selected for study based upon its shape, location, and high activity. The presumed drip-line off of the boulder was marked, samples from the boulder surface were taken, and then the boulder was moved several feet away. Soil samples were taken from directly beneath the boulder, around the drip-line, and down slope. Eight of these samples were collected in a vertical profile directly beneath the boulder. Visible flakes of boulder material were removed from the surficial soil samples, because they would have higher concentrations of U-series radionuclides and cause the activities in the soil samples to be excessively high. The vertical sampling profile used 2-inch thicknesses for each sample. The soil samples were packaged into thin plastic containers to minimize the attenuation and to standardize sample geometry, and then they were analyzed by gamma-ray spectroscopy with a Ge(Li) detector for Th-234, Pa-234, U-234, Th-230, Ra-226, Pb-214, Bi-214, and Pb-210. The raw counts were corrected for self-attenuation and normalized using BL-5, a uranium standard from Beaverlodge, Saskatchewan. BL-5 allowed the counts obtained on the Ge(Li) to be referenced to a known concentration or activity, which was then applied to the soil unknowns for a reliable calculation of their concentrations. Gamma ray spectra of five soil samples from the vertical profile exhibit decreasing activities with increasing depth for the selected radionuclides. Independent multi-element analyses of three samples by ICP-MS show decreasing uranium concentration with depth as well. The transport of the radionuclides is evaluated using STANMOD, a Windows-based software package for evaluating solute transport in porous media using analytical solutions of the advection-dispersion solute transport equation. The package allows various one-dimensional, advection-dispersion parameters to be determined by fitting mathematical solutions of theoretical transport models to observed data. The results are promising for future work on the release rate of radionuclides from the boulder, the dominant mode of transport (e.g., particulate or dissolution), and the movement of radionuclides through porous media. The measured subsurface transport rates provide modelers with a model validation dataset.

Pekar, K. E.; Goodell, P. C.; Walton, J. C.; Anthony, E. Y.; Ren, M.

2007-05-01

50

U-series ages of solitary corals from the California coast by mass spectrometry  

Microsoft Academic Search

The purpose of this study is to evaluate the feasibility of dating fossil solitary corals from Pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity, high-precision U-series technique based on thermal-ionization mass-spectrometry (TIMS). The TIMS technique is much more efficient than conventional α spectrometry and, as a result, multiple samples of an individual coral skeleton, or different

M. Stein; G. J. Wasserburg; J. H. Chen; K. R. Lajoie

1991-01-01

51

U-series ages of solitary corals from the California coast by mass spectrometry  

Microsoft Academic Search

The purpose of this study is to evaluate the feasibility of dating fossil solitary corals from Pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity, high-precision U-series technique based on thermal-ionization mass-spectrometry (TIMS). The TIMS technique is much more efficient than conventional a spectrometry and, as a result, multiple samples of an individual coral skeleton, or different

M. Stein; G. J. Wasserburg; K. R. Lajoie; J. H. Chen

1991-01-01

52

U-series dating of bone using the diffusion-adsorption model  

NASA Astrophysics Data System (ADS)

U-series dating of bone has suffered problems of reliability since its inception because bone remains an open system with respect to uranium. Commonly applied a priori assumptions of U uptake, such as early uptake or linear uptake, are inadequate because they have no physical or chemical bases, no means of demonstrating which model is suitable for a particular bone, and no intrinsic tests of reliability. Despite this and numerous examples of anomalous U-series dates, such assumptions are still routinely applied. We address this problem using the diffusion-adsorption (D-A) model of U uptake (Millard and Hedges, 1996), which incorporates a physicochemical description of U uptake. Using this model, we show how the U uptake of a bone responds to geochemical changes in the burial environment, which can lead to phenomena such as the removal of U from bones ("leaching") or U uptake late in their burial history ("recent uptake"), and we show how the overall uptake history is reflected in distributions (profiles) of U and U-series isotopes across a bone section. We present measurements of U concentration profiles, and 230Th/ 234U profiles on archeological bone from a number of different sites and burial environments and compare the results to profiles predicted by the D-A model. Bones that have undergone complex uptake histories (which include U leaching or recent uptake) are identified on the basis of these profiles and rejected as unsuitable for dating. For bones that appear to have undergone uptake under constant geochemical conditions, the D-A model is applied to calculate U-series dates, with much improved reliability.

Pike, A. W. G.; Hedges, R. E. M.; Van calsteren, P.

2002-12-01

53

Seasonal and spatial dynamics of 234Th\\/238U disequilibria in southern Lake Michigan  

Microsoft Academic Search

Measurements of 234Th\\/238U disequilibria were made on an approximately bimonthly basis over the course of a year in nearshore (1040 m deep) and offshore (160 m deep) surface waters of the southern basin of Lake Michigan (18,100 km2). The mean activity of 238U in Lake Michigan measured 230 20 dpm m?3, approximately 1 order of magnitude lower than what

James T. Waples; Kent A. Orlandini; David N. Edgington; J. Val Klump

2004-01-01

54

Seasonal and spatial dynamics of 234Th\\/238U disequilibria in southern Lake Michigan  

Microsoft Academic Search

Measurements of 234Th\\/238U disequilibria were made on an approximately bimonthly basis over the course of a year in nearshore (10-40 m deep) and offshore (160 m deep) surface waters of the southern basin of Lake Michigan (18,100 km2). The mean activity of 238U in Lake Michigan measured 230 +\\/- 20 dpm m-3, approximately 1 order of magnitude lower than what

James T. Waples; Kent A. Orlandini; David N. Edgington; J. Val Klump

2004-01-01

55

U-series and radiocarbon analyses of human and faunal remains from Wajak, Indonesia.  

PubMed

Laser ablation U-series dating results on human and faunal bone fragments from Wajak, Indonesia, indicate a minimum age of between 37.4 and 28.5 ka (thousands of years ago) for the whole assemblage. These are significantly older than previously published radiocarbon estimates on bone carbonate, which suggested a Holocene age for a human bone fragment and a late Pleistocene age for a faunal bone. The analysis of the organic components in the faunal material show severe degradation and a positive ?(13)C ratio indicate a high degree of secondary carbonatisation. This may explain why the thermal release method used for the original age assessments yielded such young ages. While the older U-series ages are not in contradiction with the morphology of the Wajak human fossils or Javanese biostratigraphy, they will require a reassessment of the evolutionary relationships of modern human remains in Southeast Asia and Oceania. It can be expected that systematic direct dating of human fossils from this area will lead to further revisions of our understanding of modern human evolution. PMID:23465338

Storm, Paul; Wood, Rachel; Stringer, Chris; Bartsiokas, Antonis; de Vos, John; Aubert, Maxime; Kinsley, Les; Grn, Rainer

2013-03-05

56

Using Pb-210/Ra-226 disequilibria for sablefish, Anoplopoma fimbria, age validation  

SciTech Connect

Age determination of sablefish (Anoplopoma fimbria) is typically done by counting growth zones on the burnt cross-section of the otolith. The break-and-burn method of age determination is difficult to apply to sablefish. Therefore, we applied a relatively new method of fish age validation, using the disequilibrium of Pb-210/Ra-226 in the otoliths. This method of validation complements previous methods which used oxytetracycline (OTC) marking to validate incremental growth in sablefish otoliths. The Pb-210/Ra-226 disequilibria generally confirmed the ageing criteria used to interpret the otolith's burnt cross-section.

Kastelle, C.R.; Kimura, D.K. (Alaska Fisheries Science Center, Seattle, WA (United States)); Nevissi, A.E.; Gunderson, D.R. (Univ. of Washington, Seattle, WA (United States))

1994-04-01

57

Symbiont survival and host-symbiont disequilibria under differential vertical transmission.  

PubMed Central

Interspecific genetic interactions in host-symbiont systems raise intriguing coevolutionary questions and may influence the effectiveness of public health and management policies. Here we present an analytical and numerical investigation of the effects of host genetic heterogeneity in the rate of vertical transmission of a symbiont. We consider the baseline case with a monomorphic symbiont and a single diallelic locus in its diploid host, where vertical transmission is the sole force. Our analysis introduces interspecific disequilibria to quantify nonrandom associations between host genotypes and alleles and symbiont presence/absence. The transient and equilibrium behavior is examined in simulations with randomly generated initial conditions and transmission parameters. Compared to the case where vertical transmission rates are uniform across host genotypes, differential transmission (i) increases average symbiont survival from 50% to almost 60%, (ii) dramatically reduces the minimum average transmission rate for symbiont survival from 0.5 to 0.008, and (iii) readily creates permanent host-symbiont disequilibria de novo, whereas uniform transmission can neither create nor maintain such associations. On average, heterozygotes are slightly more likely to carry and maintain the symbiont in the population and are more randomly associated with the symbiont. Results show that simple evolutionary forces can create substantial nonrandom associations between two species.

Sanchez, M S; Arnold, J; Asmussen, M A

2000-01-01

58

U-series ages of solitary corals from the California coast by mass spectrometry  

SciTech Connect

The purpose of this study is to evaluate the feasibility of dating fossil solitary corals from Pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity, high-precision U-series technique based on thermal-ionization mass-spectrometry (TIMS). The TIMS technique is much more efficient than conventional {alpha} spectrometry and, as a result, multiple samples of an individual coral skeleton, or different specimens from the same bed can be analyzed. Detached and well-rounded fossil specimens of the solitary coral Balanophyllia elegans were collected from relict littoral deposits on emergent marine terraces along the California coast at Cayucos terrace, Shell Beach terrace, Nestor terrace, San Diego, Bird Rock terrace, San Diego. Attached living specimens were collected from the intertidal zone on the modern terrace at Moss Beach. The calculated initial {sup 234}U activities in the fossil specimens of Balanophyllia elegans are higher than the {sup 234}U activity in modern seawater or in the modern specimen. The higher initial activities could possibly reflect the influx of {sup 234}U-enriched continental water into Pleistocene coastal waters, or it could reflect the influx of {sup 234}U-enriched continental water into Pleistocene coastal waters, or it could reflect minor diagenetic alteration, a persistent and fundamental problem in dating all corals.

Stein, M.; Wasserburg, G.J.; Chen, J.H. (California Inst. of Tech., Pasadena (United States)); Lajoie, K.R. (Geological Survey, Menlo Park, CA (United States))

1991-12-01

59

Spatial and temporal variations in terrestrial carbon isotope disequilibria simulated in coupled runs of the Community Climate System Model  

NASA Astrophysics Data System (ADS)

We introduce carbon isotope discrimination to the Community Climate System Model (CCSM) in order to simulate temporal and spatial variations in terrestrial fluxes of 12CO2 and 13CO2 and their impact on atmospheric CO2 and the seasonal and interannual isotope disequilibria, i.e., the differences between the isotopic ratios of photosynthetic and respiration. CCSM is initially spun up under preindustrial atmospheric CO2 concentrations and carbon isotope ratios to reach steady state sizes and carbon isotope ratios for soil and plant biomass. It is then run forward in coupled mode from 1900 using observed changes in atmospheric CO2 concentrations and isotope ratios. Initial results show that large seasonal and interannual isotope disequilibria associated with ENSO and associated root-zone soil-water drought stress in the tropics may be useful in determining whether observed changes in net CO2 fluxes are the result of decreases in photosynthesis or increases in respiration. In addition, we show that interannual variations in the relative contributions of C4 plants to total photosynthesis are important drivers of terrestrial disequilibria. And finally, recent rapid decreases in d13C of atmospheric CO2 due to the increasing rate of fossil fuel combustion make the use of isotope disequilibria in double deconvolutions an increasingly powerful tool in determining locations and timing of CO2 sources and sinks.

Suits, N. S.; Denning, A. S.; Thornton, P. E.; Baker, I. T.; Lee, J.

2005-12-01

60

Deep-dwelling planktonic foraminifera of the northeastern Pacific Ocean reveal environmental control of oxygen and carbon isotopic disequilibria  

NASA Astrophysics Data System (ADS)

We assess the utility of four species of living planktonic foraminifera as tracers of thermocline and intermediate water masses in the northern Pacific Ocean, based on their water-column distribution and shell isotopic composition. Assuming oxygen isotopic equilibria with the water column, we infer apparent calcification depths. This allows an estimate of apparent carbon isotopic disequilibria. We then relax the assumption of oxygen isotopic equilibrium to examine habitat effects on kinetic disequilibrium processes. In the California Current, left-coiling Neogloboquadrina pachyderma and Globigerina calida calcify in the upper thermocline. Globorotalia scitula resides within the Shallow Salinity Minumum (potential density ?? = 25.1-26.7), while Globoquadrina hexagona is associated with the deeper, North Pacific Intermediate Water ( ?? = 26.7-26.9). Apparent carbon isotopic disequilibria corrected for oxygen isotopic disequilibria, range from 1.0-1.9 in these asymbiotic species. The carbon isotopic disequilibrium can be modeled as a single exponential function of temperature or a logarithmic function of potential food supply. We infer that carbon isotopic disequilibrium increases with metabolic rate, related to temperature and/or food supply. Kinetic processes of oxygen and carbon isotopic disequilibria yields reasonable depth habitats if the slope of the oxygen:carbon isotopic shift is about 0.35, consistent with culture data. Our finding of a link between environment, metabolism, and isotopic disequilibrium observed in oceanic settings suggests the potential to better reconstruct the structure and biological processes of the upper water column from geologic data.

Ortiz, J. D.; Mix, A. C.; Rugh, W.; Watkins, J. M.; Collier, R. W.

1996-11-01

61

U-series constraints on the Holocene human presence in the Cuatro Cienegas basin, Mexico  

NASA Astrophysics Data System (ADS)

U-series tufa ages dating a human trackway have been obtained, part of a larger Late Pleistocene - Recent palaeoclimate and human occupation study of the Cuatro Cienegas basin, NE Mexico. Our analytical approach, including tracer calibration, couples aspects of what we consider best practice in the U-series community with our U-Pb experiences which includes the EarthTime U-Pb tracer calibration exercise. The recently discovered trackway is near a small hydrothermal pool within the basin [1], an ecologically highly significant oasis in the Chihuahuan desert. The oasis comprises >200 freshwater hydrothermal pools and a river system, and the related ecosystem hosts >70 endemic species[2]. Pools are fed by waters that circulate a deep karstic system and that originate in the surrounding upper Jurassic-lower Cretaceous Sierra Madre Oriental mountains (>3000m) [3]. The area hosted nomadic hunter-gatherers during the Holocene, and possibly as early as Late Pleistocene (~12 ka BP). Despite the basin's ecological significance, only three palaeoenvironmental studies have been published to date, and limited geochronological constraints are available. A pollen study of drill core through peats and tufas proximal to the pools suggested a long period of climatic stability and biogeographic isolation[4], a notion supported by the large number of endemic species, but other palynological and plant macrofossil data suggest that large climatic changes occurred post Late Pleistocene [5]. The 10 m long in situ trackway is preserved in tufa and five samples from the uppermost surfaces were analysed to date the footprints. The tufas comprise clean carbonate with no petrographic evidence of replacement and little contaminant detrital material (on some exposed upper surfaces). Powdered tufa was processed following [6-8], and analysed by TIMS (Triton, U) and MC-ICP-MS (Th, Nu HR), although our future analyses will primarily be obtained on a Neptune. Samples were spiked with a 229Th/236U tracer calibrated against gravimetric solutions prepared from Ames high-purity Th metal crystal and CRM 112a U metal ingot rather than natural materials of assumed secular equilibrium. ICP-MS mass bias and Faraday-SEM gain was monitored using CRM 112a and an in-house 229Th-230Th-232Th solution. Most samples have relatively high U contents (~2 ppm U), moderate [230Th/232Th] = 29-44, and initial [234U/238U] ~ 1.92. We obtain an age of 7.24 0.13 ka BP for this trackway based on an average of two samples of the uppermost tufa surface. Depth profiling of one sample shows consistently increasing age downwards (~370 a/cm). [1] Gonzalez, A.H.G. et al., 2006, Ichnos 16, 12-24;[2] Souza, V. et al., 2006, PNAS 103, 6565-6570; [3] Johannesson, K.H. et al., 2004, J.S.Am.Earth Sci. 17, 171-180; [4] Meyer, E. 1973, Ecology 54, 982-995; [5] Minckley, T.A. & Jackson, S. 2008. J. Biogeography 35, 188-190; [6] Edwards, R.L. et al., 1987, EPSL 81, 175-192; [8] Cheng, H. et al., 2000, Chem. Geol. 169, 17-33; [8] Potter, E.K. et al., 2005, EPSL 247, 10-17.

Noble, S. R.; Felstead, N.; Gonzalez, S.; Leng, M. J.; Metcalfe, S. E.; Patchett, P. J.

2010-12-01

62

U-series isotope and geodynamic constraints on mantle melting processes beneath the Newer Volcanic Province in South Australia  

NASA Astrophysics Data System (ADS)

Young (< 5 kyr) olivine- and clinopyroxene-phyric ne-hawaiites from Mounts Gambier and Schank in the Newer Volcanic Province in South Australia have been analysed for major and trace elements as well as for Sr and Nd isotopes and 238U 230Th disequilibria in order to constrain the mantle melting processes responsible for their origin. The rocks are relatively primitive (6.9 9.1% MgO), incompatible trace element-enriched alkali basalts with 87Sr/86Sr = 0.70398 0.70415 and 143Nd/144Nd = 0.51280 0.51271. Trace element modelling suggests that they reflect 3 6% partial melting in the presence of 2 8% residual garnet. Trends towards low K/K* are accompanied by decreasing 87Sr/86Sr and provide evidence for the involvement of hydrous phases during melting. 230Th excesses of 12 57% cannot be simulated by batch melting of the lithosphere and instead require dynamic melting models. It is argued that the distinction between continental basalts bearing significant U Th disequilibria and those in secular equilibrium reflects dynamic melting in upwelling asthenosphere, rather than static batch melting within the lithosphere or the presence or absence of residual garnet. Upwelling rates are estimated at 1.5 cm/yr. A subdued, localised topographic uplift associated with the magmatism suggests that any upwelling is more likely associated with a secondary mode localised to the upper mantle, rather than a broad zone of deeply-sourced (plume) upwelling. Upper mantle, edge-driven convection is consistent with seismic tomographic and anisotropy studies that imply rapid differential motion of variable thickness Australian lithosphere and the underlying asthenosphere. In this scenario, melting is linked to a significant contribution from hydrous mantle that is envisaged as resulting either from convective entrainment of lithosphere along the trailing edge of a lithospheric keel, or inherited variability in the asthenosphere.

Demidjuk, Zoe; Turner, Simon; Sandiford, Mike; George, Rhiannon; Foden, John; Etheridge, Mike

2007-09-01

63

Regolith formation rate from U-series nuclides: Implications from the study of a spheroidal weathering profile in the Rio Icacos watershed (Puerto Rico)  

NASA Astrophysics Data System (ADS)

A 2 m-thick spheroidal weathering profile, developed on a quartz diorite in the Rio Icacos watershed (Luquillo Mountains, eastern Puerto Rico), was analyzed for major and trace element concentrations, Sr and Nd isotopic ratios and U-series nuclides (238U-234U-230Th-226Ra). In this profile a 40 cm thick soil horizon is overlying a 150 cm thick saprolite which is separated from the basal corestone by a 40 cm thick rindlet zone. The Sr and Nd isotopic variations along the whole profile imply that, in addition to geochemical fractionations associated to water-rock interactions, the geochemical budget of the profile is influenced by a significant accretion of atmospheric dusts. The mineralogical and geochemical variations along the profile also confirm that the weathering front does not progress continuously from the top to the base of the profile. The upper part of the profile is probably associated with a different weathering system (lateral weathering of upper corestones) than the lower part, which consists of the basal corestone, the associated rindlet system and the saprolite in contact with these rindlets. Consequently, the determination of weathering rates from 238U-234U-230Th-226Ra disequilibrium in a series of samples collected along a vertical depth profile can only be attempted for samples collected in the lower part of the profile, i.e. the rindlet zone and the lower saprolite. Similar propagation rates were derived for the rindlet system and the saprolite by using classical models involving loss and gain processes for all nuclides to interpret the variation of U-series nuclides in the rindlet-saprolite subsystem. The consistency of these weathering rates with average weathering and erosion rates derived via other methods for the whole watershed provides a new and independent argument that, in the Rio Icacos watershed, the weathering system has reached a geomorphologic steady-state. Our study also indicates that even in environments with differential weathering, such as observed for the Puerto Rico site, the radioactive disequilibrium between the nuclides of a single radioactive series (here 238U-234U-230Th-226Ra) can still be interpreted in terms of a simplified scenario of congruent weathering. Incidentally, the U-Th-Ra disequilibrium in the corestone samples confirms that the outermost part of the corestone is already weathered.

Chabaux, F.; Blaes, E.; Stille, P.; di Chiara Roupert, R.; Pelt, E.; Dosseto, A.; Ma, L.; Buss, H. L.; Brantley, S. L.

2013-01-01

64

/sup 234/Th: /sup 238/U disequilibria within the California Current  

SciTech Connect

Profiles of dissolved and particulate /sup 234/Th were determined at several stations within the California Current. Modeling of the disequilibria between the /sup 234/Th and /sup 238/U within the surface waters provides for estimates of the residence time of dissolved thorium with respect to particle scavenging, the particle residence time, and the particulate /sup 234/Th flux exiting the surface layer. The model-derived, first-order scavenging rate constant for dissolved thorium is observed to be proportional to the rate of primary production. Particle residence times seem to be governed by the rate of zooplankton grazing and the types of zooplankton present. Model-derived particulate /sup 234/Th fluxes are in good agreement with direct measurements by sediment traps.

Coale, K.H.; Bruland, K.W.

1985-01-01

65

U Th Ra disequilibria and the time scale of fluid transfer and andesite differentiation at Arenal volcano, Costa Rica (1968 2003)  

NASA Astrophysics Data System (ADS)

To evaluate the time scale of fluid transfer and andesite differentiation at Arenal volcano in Costa Rica, we have measured trace-element concentrations and U-series disequilibria in whole rocks and mineral separates (pyroxene, plagioclase, magnetite) from lavas of the current eruption (1968 to 2003) by HR-ICP-MS, TIMS and PIMMS techniques. Whole rock and mineral separate analyses show a small but measurable variation in (230Th)/(232Th) (1.10 to 1.18). In contrast, (230Th)/(238U) range from 0.91 to 1.04 reflecting the moderate spread in Th/U. Stage 1 (1968 1971) whole rocks and mineral separates have both higher (230Th)/(232Th) and (238U)/(232Th) than to younger stage 2 lavas (1971 to present), which have lower, nearly constant (230Th)/(232Th) and lower, slightly variable (238U)/(232Th). 226Ra excesses exist in both whole rocks and mineral separates with (226Ra)/(230Th) ranging between 0.94 and 4.8. Whole rock (226Ra)/(230Th) are largest early in the eruption and decrease in the later lavas, which are influenced by newer recharge material. 238U 230Th whole rock and mineral data produce an inclined array on an equiline diagram, which we interpret to represent progressive melting of a variably fluxed mantle wedge and a Nicaraguan sediment component, and subsequent mixing. 238U 230Th internal isochrons suggest that minerals grew instantaneously with respect to the half-life of 230Th. Whole rock and mineral separate (226Ra)/(230Th) data indicate that melts were produced, transported, differentiated and erupted in < 8 kyr. Mineral (226Ra)/Ba (230Th)/Ba model ages are calculated and corrected for melt inclusions and glass adherents in the mineral fractions, and for the differential partitioning of Ra and Ba. Plagioclase model ages and 238U 230Th isochron ages suggest that plagioclase could be as young as a few years or as old as several centuries upon eruption.

Tepley, Frank J.; Lundstrom, Craig C.; Gill, James B.; Williams, Ross W.

2006-09-01

66

Remelting of recently depleted mantle within the Hawaiian plume inferred from the 226Ra 230Th 238U disequilibria of Pu'u '?'? eruption lavas  

NASA Astrophysics Data System (ADS)

Lavas from the Pu'u '?'? eruption of K?lauea Volcano are thought to partially bypass the shallow magma reservoir beneath the volcano's summit, and thus, provide a relatively direct window to the mantle. Here we use high-precision U-series isotope measurements of Pu'u '?'? lavas (1985 2001) to investigate the timing and mechanism of melt transport within the Hawaiian mantle plume. The lavas display small, but significant, temporal decreases in their 230Th 238U (2.5% to 1.4% excess 230Th) and 226Ra 230Th (14% to 12% excess 226Ra) disequilibria. These trends correlate systematically with larger decreases in abundance ratios of trace elements that are highly versus moderately incompatible during partial melting of the mantle. These ratios vary from a maximum of 23% for Ba / Yb to a minimum of 4% for Nd / Sm. Modeling of these geochemical signatures suggests that Pu'u '?'? lavas are increasingly derived from a mantle source that was recently depleted by prior melt extraction within the Hawaiian plume. The timing of this depletion must be longer than the 20-year duration of the eruption but less than several half-lives of 226Ra (< 8 kyr ago). A single magmatic process the transfer of melt from pores in steady-state equilibrium with the residual mantle into chemically isolated channels ultimately seems to control the rapid fluctuation in lava chemistry at Pu'u '?'?. Specifically, this mode of melt extraction (if it occurs frequently) would create numerous patches of recently depleted mantle within K?lauea's source region that may subsequently remelt. When melt is extracted into channels to supply a given eruption, such as Pu'u '?'?, it must be drained from an ever increasing volume in order to sustain the flow of melt to the surface. As the eruption continues, the volcano might tap melt from more distal areas and tend to encounter a greater number of patches of melt from recently depleted mantle. The source region of Pu'u '?'? lavas within the Hawaiian plume is also thought to contain long-lived, small-scale compositional heterogeneities based on temporal variations of ratios of highly incompatible trace elements (Ba / Th or Th / U) and 87Sr / 86Sr. This melt-transport mechanism would allow K?lauea to sample chemically and isotopically heterogeneous pockets of melt from fresh mantle that was never melted beneath Hawai'i (in addition to melt from recently depleted mantle), and thus, efficiently transmit the geochemical signatures of these compositional heterogeneities from the volcano's source region to the surface.

Pietruszka, Aaron J.; Hauri, Erik H.; Carlson, Richard W.; Garcia, Michael O.

2006-04-01

67

High-precision U-series dating of Holocene corals from South China Sea by thermal ionization mass spectrometry (TIMS)  

Microsoft Academic Search

Using the isotopic diluting and thermal ionization mass spectrometric (TIMS) technique, the U-series dating procedure was\\u000a established on the basis of measurement of national standard GBW04412. With this highly precise technique the Holocene corals\\u000a from the South China Sea were dated. Comparison between this method and ?-spectrometry was made. The results show that a thriving\\u000a period of corals in the

Zhibang Ma; Ming Xia; Chenghui Zhang; Zicheng Pen; Zhaorong Wang; Weidong Sun; Zhisheng An

1999-01-01

68

Evaluating U-series tools for weathering rate and duration on a soil sequence of known ages  

NASA Astrophysics Data System (ADS)

Four soil profiles of known age (40, 250, 600 and 3000 ka) from the Merced soil chronosequence in California were analysed for U and Th isotopes, and for major- and trace-element compositions, to test the assumption that leaching of U-series isotopes is a first order process with an invariant rate constant, as frequently assumed when applying this isotopic tool to determine weathering duration and sediment residence time. Average (230Th/238U) values for each profile decrease from a high of 1.28 in the youngest soil (40 ka) to 1.09, 0.99 and 0.98 in the 250 ka, 600 ka and 3000 ka soils respectively. (234U/238U) values also show variation across the 4 soils. The simultaneous variation in (230Th/238U) and (234U/238U) cannot be explained by a first-order kinetic model with invariant rate constants and instead requires that leaching coefficients for the U-series isotopes change with time. The observed data is consistent with a two-stage model that reflects an initial period of fast leaching of U and Th from a readily weathered soil pool (such as grain boundaries or defects), followed by slow leaching from a more resistant soil pool. Application of such a two-stage model may lead to significantly shorter calculated timescales of weathering than those obtained by the widely applied single-stage model of U-series weathering, which assumes no change in leaching coefficients over time. The results of this study have wide implications for published and future use of U-series tools in weathering studies.

Keech, Andrew R.; West, A. Joshua; Pett-Ridge, Julie C.; Henderson, Gideon M.

2013-07-01

69

High-precision U-series measurements of more than 500,000year old fossil corals  

Microsoft Academic Search

Robust, independent age constraints on the absolute timing of climate events based on the U-series dating of fossil coral are sparse before the last glacial cycle. Using multiple-collector inductively coupled plasma mass spectrometry with multiple-Faraday protocols, we are able to date ?600ka samples with an uncertainty of better than 15ka (2?), representing a three-fold improvement in precision compared with previous

Morten B. Andersen; Claudine H. Stirling; Emma-Kate Potter; Alex N. Halliday; Steven G. Blake; Malcolm T. McCulloch; Bridget F. Ayling; Michael O'Leary

2008-01-01

70

Middle Palaeolithic refugium, or archaeological misconception? A new U-Series and radiocarbon chronology of Abric Agut (Capellades, Spain)  

USGS Publications Warehouse

New U-Series and C14 (AMS) dates are provided for the Abric Agut (Capellades, Barcelona, Spain). This site was previously considered to be of Middle Palaeolithic age according to the characteristics of the lithic assemblage. In addition, human teeth were uncovered and attributed to neandertals. However, radiometric dating clearly indicates a Late Pleistocene-Early Holocene age. ?? 2002 Elsevier Science Ltd. All rights reserved.

Vaquero, M.; Esteban, M.; Allue, E.; Vallverdu, J.; Carbonell, E.; Bischoff, J. L.

2002-01-01

71

Comment on Ra-Th disequilibria systematics: Timescale of carbonatite magma formation at Oldoinyo Lengai volcano, Tanzania  

SciTech Connect

This paper discusses potential flaws in study by Williams, Gill, and bruland (1986) dealing with the extreme disequilibria between uranium and thorium series nuclides in alkalic carbonatite lava specimens. It discusses the apparent discrepencies between chemical compositions of lava which were reported from the same eruption. Clarification is made on the actual timing of eruptions in this volcanic region and the effects this would have on the petrogenesis interpretation of these rocks.

Gittins, J. (Univ. of Toronto, Ontario (Canada))

1988-04-01

72

Behaviour of nuclides and U-series disequilibrium in clayey sediments: application to the Late Jurassic record from the eastern Paris basin  

NASA Astrophysics Data System (ADS)

We present a record of U-series disequilibrium covering the Callovo-Oxfordian-Thitonian times of the Late Jurassic carbonated platform from the eastern part of the Paris basin. The Callovo-Oxfordian clayey layer is the potential host rock for reconnaissance work carried out by Andra (e.g., Agence Nationale de Gestion des Dchets Radioactifs) in eastern France, the objective of which is the designing and building of an underground research laboratory to study the aptitude of the clay-marl Callovo-Oxfordian layer for the storage of radioactive wastes. We analyse U and Th trace elements on both the labile fraction (extracted by cold HCl) and the total bulk sediments. The Th contents are extremely low in the Oxfordian shelf reef carbonates (<10 ppb) with respect to the Kimmeridgian-Tithonian clayey marls and the Callovian-Oxfordian argilites (up to 10 ppm). In contrast, the uranium contents are much more homogenous (1 ppm 0.8) along the section. With respect to bulk concentrations, the nuclide contents in the labile component are particularly low in the Callovian-Oxfordian argilites. This behaviour suggests that given the extremely low permeability of the rock, any groundwater circulation of solutes could only have taken place by diffusion - a very slow mechanism that favours water-rock interactions. For U-series analyses (measured by alpha-spectrometry), a total of 43 bulk-rock samples were preferentially microdrilled from the fine-grained lithologies, although the heterogeneity of carbonate facies within sections necessitated occasional sampling of coarser grained lithologies. Within the carbonate-rich part (Oxfordian to Tithonian) of the section, the 234U/238U ratios slightly fluctuate from secular equilibrium and are interpreted as preferential 234U-solution processes related to groundwater circulation. Preferential removal of 234U in this zone is also indicated by some 230Th/234U activity ratios higher than unity. In contrast, most of the samples from the Callovian-Oxfordian argilites plot on or close to the secular equilibrium line. The observed isotopic disequilibriums from samples taken on either side of the interface between the clay formation and the carbonated country rock, are mainly related to a 234U deficiency relative to 230Th and correspond to bulk U-solution.

Casanova, J.; Ngrel, Ph.; Innocent, C.; Brulhet, J.

2003-04-01

73

U-series ages of solitary corals from the California coast by mass spectrometry  

USGS Publications Warehouse

The purpose of this study is to evaluate the feasibility of dating fossil solitary corals from Pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity, high-precision U-series technique based on thermal-ionization mass-spectrometry (TIMS). The TIMS technique is much more efficient than conventional a spectrometry and, as a result, multiple samples of an individual coral skeleton, or different specimens from the same bed can be analyzed. Detached and well-rounded fossil specimens of the solitary coral Balanophyllia elegans were collected from relict littoral deposits on emergent marine terraces along the California coast at Cayucos terrace (elevation 8 m, previously dated at 124 and 117 Ky by ?? counting), Shell Beach terrace (elevation about 25 m, previously undated), Nestor terrace, San Diego (elevation 23 m, previously dated at 131 to 109 Ky ), Bird Rock terrace, San Diego ( elevation 8 m, previously dated at 81 Ky ). Attached living specimens were collected from the intertidal zone on the modern terrace at Moss Beach. Concentrations of 232Th in both living and fossil specimens are much higher than in reef-building corals (12 to 624 pmol/g vs. 0.1 to 1.6 pmol/g, respectively). However, because 230Th/232Th in Balanophyllia elegans are very low (2.22 ?? 10-3 to 4.33 ?? 10-4), the high 232Th concentrations have negligible effect on the 230Th-234U dates. The high 232Th concentration in the living specimen (33.1 pmol/g) indicates that a significant amount of 232Th is incorporated in the aragonitic skeleton during growth, or attached to clay-sized silicates trapped in the skeletal material. The calculated initial 234U activities in the fossil specimens of Balanophyllia elegans are higher than the 234U activity in modern seawater or in the modern specimen. The higher initial activities could possibly reflect the influx of 234U-enriched continental water into Pleistocene coastal waters, or it could reflect minor diagenetic alteration, a persistent and fundamental problem in dating all corals. Samples from a compound specimen from the Cayucos terrace were subjected to different preparation procedures. Samples prepared by a standard acid washing procedure yielded 230Th-234U ages of 125, 123, and 122 Ky, whereas samples prepared by an abbreviated procedure without acid washing yield significantly lower ages of 113 and 112 Ky. Two other specimens from the same bed yielded 230Th-234U ages of 118 and 115 Ky. Also, two specimens from a stratigraphically higher bed yielded ages of 120 and 117 Ky, and three specimens from a lower bed yield ages of 115, 113, and 101 Ky. Nine of the twelve ages of the treated samples from the Cayucos terrace range from 125 to 113 Ky. However, the ages do not follow the stratigraphie order. Two possible interpretations are ( 1 ) the age of the terrace deposit is 125 Ky and all younger ages reflect variable diagenetic alteration or (2) the age of the terrace is 125 to 113 Ky and the ages reflect sediment reworking over a period of 12 Ky. Three specimens from a single bed on the Shell Beach terrace yield ages of 126, 122, and 121 Ky, similar to the older ages from Cayucos. The ages of solitary corals from the Cayucos and Shell Beach terraces are similar to ages of reef-building corals from terraces at numerous tropical localities. These are correlated with the last interglacial sea-level highstand, which probably stood 2 to 10 m above present sea level. The youngest ages and present elevations of the Cayucos and Shell Beach terraces yield tectonic uplift rates of 0.01 and 0.15 m/Ky, respectively, assuming the original elevation of each terrace was 7 m. Four specimens from the basal gravel on the Nestor terrace yielded ages of 145, 143, 137, and 133 Ky. The three oldest ages, however, are older than that associated with the last interglacial. The possible explanations for these older ages are ( 1 ) diagenic alteration or ( 2 ) the Nestor terrace deposits reflect in s

Stein, M.; Wasserburg, G. J.; Lajoie, K. R.; Chen, J. H.

1991-01-01

74

U-series ages of solitary corals from the California coast by mass spectrometry  

NASA Astrophysics Data System (ADS)

The purpose of this study is to evaluate the feasibility of dating fossil solitary corals from Pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity, high-precision U-series technique based on thermal-ionization mass-spectrometry (TIMS). The TIMS technique is much more efficient than conventional a spectrometry and, as a result, multiple samples of an individual coral skeleton, or different specimens from the same bed can be analyzed. Detached and well-rounded fossil specimens of the solitary coral Balanophyllia elegans were collected from relict littoral deposits on emergent marine terraces along the California coast at Cayucos terrace (elevation 8 m, previously dated at 124 and 117 Ky by counting), Shell Beach terrace (elevation about 25 m, previously undated), Nestor terrace, San Diego (elevation 23 m, previously dated at 131 to 109 Ky ), Bird Rock terrace, San Diego ( elevation 8 m, previously dated at 81 Ky ). Attached living specimens were collected from the intertidal zone on the modern terrace at Moss Beach. Concentrations of 232 Th in both living and fossil specimens are much higher than in reef-building corals (12 to 624 pmol/g vs. 0.1 to 1.6 pmol/g, respectively). However, because 230 Th/ 232 Th in Balanophyllia elegans are very low (2.22 10 -3 to 4.33 10 -4 ), the high 232 Th concentrations have negligible effect on the 230 Th- 234 U dates. The high 232 Th concentration in the living specimen (33.1 pmol/g) indicates that a significant amount of 232 Th is incorporated in the aragonitic skeleton during growth, or attached to clay-sized silicates trapped in the skeletal material. The calculated initial 234 U activities in the fossil specimens of Balanophyllia elegans are higher than the 234 U activity in modern seawater or in the modern specimen. The higher initial activities could possibly reflect the influx of 234 U-enriched continental water into Pleistocene coastal waters, or it could reflect minor diagenetic alteration, a persistent and fundamental problem in dating all corals. Samples from a compound specimen from the Cayucos terrace were subjected to different preparation procedures. Samples prepared by a standard acid washing procedure yielded 230 Th- 234 U ages of 125, 123, and 122 Ky, whereas samples prepared by an abbreviated procedure without acid washing yield significantly lower ages of 113 and 112 Ky. Two other specimens from the same bed yielded 230 Th- 234 U ages of 118 and 115 Ky. Also, two specimens from a stratigraphically higher bed yielded ages of 120 and 117 Ky, and three specimens from a lower bed yield ages of 115, 113, and 101 Ky. Nine of the twelve ages of the treated samples from the Cayucos terrace range from 125 to 113 Ky. However, the ages do not follow the stratigraphie order. Two possible interpretations are ( 1 ) the age of the terrace deposit is 125 Ky and all younger ages reflect variable diagenetic alteration or (2) the age of the terrace is 125 to 113 Ky and the ages reflect sediment reworking over a period of 12 Ky. Three specimens from a single bed on the Shell Beach terrace yield ages of 126, 122, and 121 Ky, similar to the older ages from Cayucos. The ages of solitary corals from the Cayucos and Shell Beach terraces are similar to ages of reef-building corals from terraces at numerous tropical localities. These are correlated with the last interglacial sea-level highstand, which probably stood 2 to 10 m above present sea level. The youngest ages and present elevations of the Cayucos and Shell Beach terraces yield tectonic uplift rates of 0.01 and 0.15 m/Ky, respectively, assuming the original elevation of each terrace was 7 m. Four specimens from the basal gravel on the Nestor terrace yielded ages of 145, 143, 137, and 133 Ky. The three oldest ages, however, are older than that associated with the last interglacial. The possible explanations for these older ages are ( 1 ) diagenic alteration or ( 2 ) the Nestor terrace deposits reflect in some way a poorly documented early phase of the last interglacial sea level hi

Stein, M.; Wasserburg, G. J.; Lajoie, K. R.; Chen, J. H.

1991-12-01

75

U-Th-Ra disequilibria and the extent of off-axis volcanism across the East Pacific Rise at 930?N, 1030?N, and 1120?N  

NASA Astrophysics Data System (ADS)

There is widespread interest in the distance that mid-ocean ridge magmatism extends beyond the neovolcanic zone. Off-axis magmas also provide a means to map out variations across the melting zone. We present 238U-230Th-226Ra data for 35 well-characterized samples that extend up to 50 km away from the ridge axis across the East Pacific Rise at 930'N, 1030'N, and 1120'N. The (230Th/238U) ratios range from 1.00 to 1.19, and the (226Ra/230Th) ratios range from 1 to 2.78. The samples have a bimodal (230Th/238U) distribution with approximately half overlying published axial data on the U-Th diagram and the remainder lying close to the equiline. The U series disequilibria in the majority of the samples can be explained by aging subsequent to eruption in a zone 8 km wide about the neovolcanic zone, consistent with visual evidence for sample age. Nevertheless, seven of the samples lie above calculated (230Th/238U) axial decay curves and/or have 226Ra excesses implying eruption tens of kilometers off axis. These are consistent with evidence from seamounts and seismic interpretations that magmatism can extend up to 20 km off axis. The implication is that magma is not as efficiently focused beneath the ridge axis as has generally been believed. There is a decrease in initial (230Th/238U) in both these and published samples inferred to have formed off axis, but there is no compelling evidence that this reflects source heterogeneity. Simple modeling suggests that this could be explained by a decrease in fertility and melt column length as the overlying lithosphere thickens with age and the solidus shallows.

Turner, Simon; Beier, Christoph; Niu, Yaoling; Cook, Craig

2011-07-01

76

Preliminary U-series disequilibrium and thermoluminescence ages of surficial deposits and paleosols associated with Quaternary fault, Eastern Yucca Mountain  

SciTech Connect

Geochronological control is an essential component of paleoseismic evaluation of faults in the Yucca Mountain region. New U-series disequilibrium and thermoluminescence age estimates for pedogenic deposits that bracket surface-rupture events are presented from four sites exposing the Paintbrush Canyon, Bow Ridge and Stagecoach Road faults. Ages show an internal consistency with stratigraphic relationships as well as an overall concordancy between the two independent geochronometers. Age estimates are therefore interpreted to date depositional events or episodes of pedogenic carbonate mobility that can be used to establish a paleoseismic fault chronology. Ultimately, this type of chronological information will be used to evaluate seismic hazards at Yucca Mountain.

Paces, J.B.; Menges, C.M.; Bush, C.A.; Futa, K.; Millard, H.T.; Maat, P.B.; Whitney, J.W. [Geological Survey, Denver, CO (United States); Widmann, B. [Science Applications International Corp., Golden, CO (United States); Wesling, J.R. [Geomatrix Consultants, Inc., San Francisco, CA (United States)

1994-12-31

77

U-Th-Ra disequilibria in sediments of the Dora Baltea river (Italia)  

NASA Astrophysics Data System (ADS)

In order to constrain the transfer time of sediments in Alpine rivers, we propose to use the U-series nuclides approach recently developed for Himalayan rivers (e.g., Chabaux et al., 2008; Granet et al., 2010). Therefore, a series of bank sediments has beeen collected along the Dora Baltea river (Italia), one of the Po's tributaries draining the southern slope of the Mont Blanc Massif. In addition to U series nuclides, major and trace element concentrations and Sr and Nd isotope ratios have been analyzed for each sample. The study indicates that the (234U/238U)-, (230Th/234U)- and the (226Ra/230Th)- activity ratios are very similar for all the samples, whereas the 230Th/232Th ratios can differ from one sample to another. Such a variation, consistent with the Sr and Nd isotope data, is certainly the consequence of mineralogical heterogeneities in the samples. This suggests that the use of 238U-230Th-232Th systematics alone is probably insufficient for constraining the transfer time of sediments in the Po rivers alluvial plain, whereas the combination of 238U-230Th disequilibrium with the 230Th-226Ra disequilibrium can help to constrain such time information.

Chabaux, F.; Deloche, A.; Pelt, E.; Granet, M.; Perrone, Th.; Boutin, R.; Viville, D.; Rihs, S.; Stille, P.

2012-04-01

78

Assessment of chemical disequilibria in oil reservoirs: Implications for production- and diagenetic-timescale geochemical modelling  

SciTech Connect

The accurate prediction of reservoir fluid-rock interaction in oil reservoirs is important in both production engineering and reservoir geology. Produced and/or mixed brine scaling tendencies, formation damage and production treatments all require a knowledge of mineral dissolution and precipitation both close to the well-bore and in the interwell volume. This can be carried forward into the longer timescale over which diagenetic processes occur to predict reservoir quality and to trace migration pathways. Geochemical packages which are available to model such processes are based on equilibrium thermodynamics. However, during the relatively short timescale of oilfield production, the introduction of large volumes of external brines generally causes the fluid-rock system to be far from equilibrium. In order to apply quantitative geochemical modelling to prediction of production chemistry, the degree of chemical disequilibrium must be assessed. The Oilfield Scale Research Group at Heriot-Watt University has conducted an extensive series of flooding experiments in which many ([approx]40) reservoir cores have been reconditioned to reservoir conditions and seawater (or produced brine) has been injected over long time periods (up to months) at elevated temperatures. The composition of injection fluid and effluent are monitored throughout the flood and the full mineralogical analysis of the core both before and after these floods has been established. We are able to quantify the fluid-rock interaction. Both carbonate and aluminosilicate systems have been examined. Comparing the experimental core flooding data with thermodynamic simulations of those systems illuminates the degree of disequilibria present over production timescales. The results from many core floods in various mineralogical systems have been analyzed and will be presented. Certain reactions can be assigned to be rate independent over the timescale in question, by either occurring spontaneously or not at all.

Bunney, J.R.; Sorbie, K.S.; Jordan, M.M. (Heriot-Watt Univ., Edinburgh, Scotland (United Kingdom))

1996-01-01

79

The Role of Plants in the 238U-234U Disequilibria of Stream Waters: The Example of the Strengbach Watershed (Vosges, France)  

Microsoft Academic Search

Recent TIMS or MC ICPMS analyses of U disequilibria in the dissolved load of stream and river waters have confirmed the potential of the U activity ratio in river waters as a specific tracer of chemical fluxes coming from rocks and soils (e.g., 1). These precise measurements have also outlined that occurrence of U activity ratios lower than one in

M. Pierret; F. Chbaaux

2004-01-01

80

Short-lived radioactivity and magma genesis  

NASA Astrophysics Data System (ADS)

Short-lived decay products of uranium and thorium have half-lives and chemistries sensitive to the processes and time scales of magma genesis, including partial melting in the mantle and magmatic differentiation in the crust. Radioactive disequilibrium between U-238, Th-230, and Ra-226 is widespread in volcanic rocks. These disequilibria and the isotopic composition of thorium depend especially on the extent and rate of melting as well as the presence and composition of vapor during melting. The duration of mantle melting may be several hundred millennia, whereas ascent times are a few decades to thousands of years. Differentiation of most magmas commonly occurs within a few millennia, but felsic ones can be tens of millennia old upon eruption.

Gill, James; Condomines, Michel

1992-09-01

81

High-precision U-series dating of corals from Western Australia and implications for the timing and duration of the Last Interglacial  

Microsoft Academic Search

U-series ages using methods of thermal ionisation mass spectrometry (TIMS) are reported for Last Interglacial fossil reefs along the stable coastal margin of Western Australia. Thorium isotope ratios were measured with superior precision using methods of charge collection. High levels of precision in the measurement of both uranium and thorium isotopes has reduced the age uncertainty due to analytical errors,

C. H. Stirling; T. M. Esat; M. T. McCulloch; K. Lambeck

1995-01-01

82

TIMS U-series dating and stable isotopes of the last interglacial event in Papua New Guinea  

SciTech Connect

The extensive flight of uplifted reef terraces which occurs along the Vitiaz strait on the northern flank of the Huon Peninsula in PNG (Papua New Guinea) contains a particularly good record of sea level changes in the last 250 ky. The Huon terraces were the target of an international expedition which took place in July--August 1988. In particular, the authors searched for suitable samples for U-series dating in a reef complex designated as VII, which is correlated with the last interglacial episode and high sea level stand. This complex is composed of a barrier reef (VIIb), a lagoon, and a fringing reef (VIIa). Twelve corals from these terraces and two corals from the older reef complex VIII were selected for analysis. The petrography, oxygen and carbon isotope compositions, and magnesium and strontium concentrations were determined along with the concentrations and isotopic compositions of uranium and thorium. The simplest model for sea level height for terrace VII is a continuous rise between 134 and 118 ky. Alternatively, there may have been two periods of rapid sea level rise. In contrast, in the Bahamas, there is evidence that sea level remained rather constant over the time interval 132 to 120 ky. The absence of ages between 132 and 120 ky in PNG could be the result of changes in the local tectonic uplift rates during that time, or erosion that disrupted the continuous record. In any event, the authors find no basis for accepting a single brief time for the age of the last interglacial and applying this age as a precise chronometer for worldwide correlation, or as a test of climatic models. The older ages reported here precede the Milankovitch solar insolation peak at 128 ky, and the younger ages are [approximately]10 ky after this peak. If the present high-precision data are correct, then it will be necessary to reassess the validity of the Milankovitch theory of climatic changes. 76 refs., 6 figs., 6 tabs.

Stein, M.; Wasserburg, G.J.; Chen, J.H. (California Inst. of Technology, Pasadena (United States)); Aharon, P. (Louisiana State Univ., Baton Rouge (United States)); Zhu, Z.R.; Chappell, J. (Australian National Univ., Canberra (Australia)); Bloom, A. (Cornell Univ., Ithaca, NY (United States))

1993-06-01

83

Crystallization history of rhyolites at Long Valley, California, inferred from combined U-series and Rb-Sr isotope systematics  

NASA Astrophysics Data System (ADS)

In this study, we present 87Rb/ 86Sr and 230Th/ 238U isotope analyses of glasses and phenocrysts from postcaldera rhyolites erupted between 150 to 100 ka from the Long Valley magmatic system. Both isotope systems indicate complex magma evolution with preeruptive mineral crystallization and magma fractionation, followed by extended storage in a silicic magma reservoir. Glass analyses yield a Rb-Sr isochron of 257 39 ka, which can be explained by a feldspar-fractionation event 150 ky before eruption. Individual feldspar-glass pairs confirm this age result. A mineral 230Th- 238U isochron in a low-silica rhyolite from the Deer Mountain Dome defines an age of 236 1 ka, but the glass and whole rock do not lie on the isochron. U-Th fractionation of the rocks is controlled by the accessory minerals zircon and probably allanite, which crystallized at 250 3 ka and 187 9 ka, respectively. All major mineral phases contain accessory mineral phases; therefore, the mineral isochron represents a mixture of zircon and allanite populations. A precision of 1 ka for the mixing array implies that the minor phases must have crystallized within this timescale. Longer periods of crystal growth would cause the mixing array to be less well defined. U-series data from other low- and high-silica rhyolites indicate younger accessory mineral crystallization events at 200 and 140 ka, probably related to the thermal evolution of the magma reservoir. These crystallization events are, however, only documented by the accessory minerals and had no further influence on bulk magma compositions. We interpret the indistinguishable age results from both isotope systems (250 ka) to record the fractionation of small magma batches by filter pressing from a much larger underlying magma volume, followed by physical isolation and extended storage at the top of the magma reservoir for up to 150 ky.

Heumann, Arnd; Davies, Gareth R.; Elliott, Tim

2002-05-01

84

TIMS U-series dating and stable isotopes of the last interglacial event in Papua New Guinea  

NASA Astrophysics Data System (ADS)

The extensive flight of uplifted reef terraces which occurs along the Vitiaz strait on the northern flank of the Huon Peninsula in PNG (Papua New Guinea) contains a particularly good record of sea level changes in the last 250 ky. The Huon terraces were the target of an international expedition which took place in July-August 1988. In particular, we searched for suitable samples for U-series dating in a reef complex designated as VII, which is correlated with the last interglacial episode and high sea level stand. This complex is composed of a barrier reef (VIIb), a lagoon, and a fringing reef (VIIa). Twelve corals from these terraces and two corals from the older reef complex VIII were selected for analysis. The petrography, oxygen and carbon isotope compositions, and magnesium and strontium concentrations were determined along with the concentrations and isotopic compositions of uranium and thorium. 230Th- 234U ages of the corals with > 99% aragonite, having primary textures, and which show U/Sr ratios around 0.4 10 -3 and initial ? 234U values close to that of present seawater, appear to be reliable. The "most reliable" ages from complex VII corals fall in two tight groups centered at 118 ky and 134 ky. Corals with ?234U( T) values higher than 160 and U/Sr ratios substantially lower than seawater are assumed to have undergone diagenetic alteration, which appears to be common in this area. The simplest model for sea level height for terrace VII is a continuous rise between 134 and 118 ky. Alternatively, there may have been two periods of rapid sea level rise. In contrast, in the Bahamas, there is evidence that sea level remained rather constant over the time interval 132 to 120 ky. The absence of ages between 132 and 120 ky in PNG could be the result of changes in the local tectonic uplift rates during that time, or erosion that disrupted the continuous record. In any event, we find no basis for accepting a single brief time for the age of the last interglacial and applying this age as a precise chronometer for worldwide correlation, or as a test of climatic models. The older ages reported here precede the Milankovitch solar insolation peak at 128 ky, and the younger ages are ~ 10 ky after this peak. If the present high-precision data are correct, then it will be necessary to reassess the validity of the Milankovitch theory of climatic changes. The fundamental issue which must now be resolved is a means of identifying coral samples that have not been disturbed by diagenetic processes.

Stein, M.; Wasserburg, G. J.; Aharon, P.; Chen, J. H.; Zhu, Z. R.; Bloom, A.; Chappell, J.

1993-06-01

85

Origins of large-volume, compositionally zoned volcanic eruptions: New constraints from U-series isotopes and numerical thermal modeling for the 1912 Katmai-Novarupta eruption  

Microsoft Academic Search

We present the results of a combined U-series isotope and numerical modeling study of the 1912 Katmai-Novarupta eruption in Alaska. A stratigraphically constrained set of samples have compositions that range from basalt through basaltic andesite, andesite, dacite, and rhyolite. The major and trace element range can be modeled by 8090% closed-system crystal fractionation over a temperature interval from 1279C to

Simon Turner; Mike Sandiford; Mark Reagan; Chris Hawkesworth; Wes Hildreth

2010-01-01

86

High-precision TIMS U-series and AMS 14C dating of a coral reef lagoon sediment core from southern South China Sea  

Microsoft Academic Search

Accurate dating of lagoon sediments has been a difficult problem, although lagoon profiles, usually with high deposition rates, have a great potential for high-resolution climate reconstruction. We report 26 high-precision TIMS U-series dates (on 25 coral branches) and five AMS 14C dates (on foraminifera) for a 15.4-m long lagoon core from Yongshu Reef, Nansha area, southern South China Sea. All

Ke-Fu Yu; Jian-Xin Zhao; Pin-Xian Wang; Qi Shi; Qing-Shan Meng; Kenneth D. Collerson; Tung-Sheng Liu

2006-01-01

87

U-series dating of soda straw stalactites from excavated deposits: method development and application to Blanche Cave, Naracoorte, South Australia  

Microsoft Academic Search

This study aimed to further test the method, reported by St Pierre et al. (2009), to develop robust chronologies of deposits in limestone caves through U\\/Th (Uranium\\/Thorium or U-Series) dating of soda straw stalactites. The chronology of fossil bearing deposits at Blanche Cave was further constrained with thermal ionisation mass spectrometry (TIMS) U\\/Th dating of 17 additional soda straw stalactite

E. St Pierre; J. x Zhao; Y. x. Feng; E. Reed

88

U-series dating of dead Porites corals in the South China sea: Evidence for episodic coral mortality over the past two centuries  

Microsoft Academic Search

High-precision (up to 12 years) U-series dating of dead in situ massive Porites corals on the reef flats of Yongshu and Meiji Reefs, Nansha area, southern South China Sea reveals that mortality of these massive corals occurred many times over the past two centuries, many of which appear to correlate in time with historic El Nio events. Despite different habitats

Ke-Fu Yu; Jian-Xin Zhao; Qi Shi; Te-Gu Chen; Pin-Xian Wang; Kenneth D. Collerson; Tung-Sheng Liu

2006-01-01

89

U-series and oxygen isotope chronology of the mid-Pleistocene Lake Amora (Dead Sea basin)  

NASA Astrophysics Data System (ADS)

This study establishes for the first time the chronology and limnological history of Lake Amora (Dead Sea basin, Israel), whose deposits (the Amora Formation) comprise one of the longest exposed lacustrine records of the Pleistocene time. The Amora Formation consists of sequences of laminated primary aragonite and silty-detritus, Ca-sulfate minerals, halite and clastic units. This sedimentary sequence was uplifted and tilted by the rising Sedom salt diapir, exposing 320 m of sediments on the eastern flanks of Mt. Sedom (the Arubotaim Cave (AC) section). The chronology of the AC section is based on U-disequilibrium dating ( 230Th- 234U and 234U- 238U ages) combined with floating ?18O stratigraphy and paleomagnetic constraints. The determination of the 230Th- 234U ages required significant corrections to account for detrital Th and U. These corrections were performed on individual samples and on suites of samples from several stratigraphic horizons. The most reliable corrected ages were used to construct an age-elevation model that was further tuned to the oxygen isotope record of east Mediterranean foraminifers (based on the long-term similarity between the sea and lake oxygen isotope archives). The combined U-series- ?18O age-elevation model indicates that the (exposed) Amora sequence was deposited between 740 and 70 ka, covering seven glacial-interglacial cycles (Marine Isotope Stages (MIS) 18 to 5). Taking the last glacial Lake Lisan and the Holocene Dead Sea lacustrine systems as analogs of the depositional-limnological environment of Lake Amora, the latter oscillated between wet (glacial) and more arid (interglacial) conditions, represented by sequences of primary evaporites (aragonite and gypsum that require enhanced supply of freshwater to the lakes) and clastic sediments, respectively. The lake evolved from a stage of rapid shifts between high and low-stand conditions during 740 to 550 ka to a sabkha-like environment that existed (at the AC site) between 550 and 420 ka. This stage was terminated by a dry spell represented by massive halite deposition at 420 ka (MIS12-11). During MIS10-6 the lake fluctuated between lower and higher stands reaching its highest stand conditions at the late glacial MIS6, after which a significant lake level decline corresponds to the transition to the last interglacial (MIS5) low-stand lake, represented by the uppermost part of the Formation. ?18O values in the primary aragonite range between 6.0 and -1.3 , shifting cyclically between glacial and interglacial intervals. The lowest ?18O values are observed during interglacial stages and may reflect short and intense humid episodes that intermittently interrupted the overall arid conditions. These humid episodes, expressed also by enhanced deposition of travertines and speleothems, seem to characterize the Negev Desert, and in contrast to the overall dominance of the Atlantic-Mediterranean system of rain patterns in the Dead Sea basin, some humid episodes during interglacials may be traced to southern sources.

Torfstein, Adi; Haase-Schramm, Alexandra; Waldmann, Nicolas; Kolodny, Yehoshua; Stein, Mordechai

2009-05-01

90

Uranium-series disequilibria in Vanuatu arc volcanic rocks: constraints on pre-eruptive processes in contrasting volcanic systems  

NASA Astrophysics Data System (ADS)

Recent and present volcanism in the Vanuatu arc (South West Pacific Ocean) occurs at a variety of volcano types that exhibit a wide range of eruptive behaviour: from post-caldera lava-lake activity and lava flows at shield volcanoes (Ambrym), moderately explosive sub-plinian events and associated pyroclastic-flows and lava flows at stratovolcanoes (Lopevi), to persistent strombolian and vulcanian-style eruptions at scoria cones (Yasur). This precludes a generic model of magmatic and eruptive behaviour for the Vantuatu arc volcanoes and necessitates a detailed study of each system. Uranium-series disequilibria in volcanic rocks offer unique insights into pre-eruptive magmatic systems over process-relevant timescales e.g., 238U-230Th (380Ka), 230Th-226Ra (8Ka) and 226Ra-210Pb (100a). The short half-life of 210Pb (t1/2 = 22.6 years) and the volatile nature of the intermediate isotope, 222Rn, (intermediate between the 226Ra parent and 210Pb daughter) provide valuable information on magma transport, evolution and degassing over a timescale more pertinent to the processes leading up to volcanic eruptions. We present new Uranium-series isotope data (U-Th-Ra-210Pb) for young (< 100 years old) volcanic samples from Ambrym, Lopevi and Yasur volcanoes to investigate the timescales of magmatic evolution and degassing in the contrasting volcanic systems. 210Pb deficits ((210Pb/226Ra)0 < 1) in Ambrym and Yasur volcanic rocks suggest effective open-system magmatic degassing of 222Rn, consistent with the persistent lava-lakes/exposed magma and significant gas emissions observed at both volcanoes. Lopevi, on the other hand, largely displays excess 210Pb ((210Pb/226Ra)0 > 1) suggesting that 222Rn gas accumulation and fluxing preceding and/or during eruption (on a decadal timescale) is responsible for the more explosive-style of eruption witnessed at this volcano. Significant accumulation of recently crystallised plagioclase phenocrysts can also create 210Pb excesses in volcanic rocks, however, this process is not supported by the petrographic and geochemical data. In summary 210Pb-226Ra disequilibria in Vanuatu volcanic rocks reveal a strong link between pre-eruptive magma degassing systematics and the resultant style of volcanic activity.

Handley, H. K.; Turner, S.; Reagan, M. K.; Girard, G.; Cronin, S. J.; Firth, C.

2011-12-01

91

10Be and U-series dating of late Quaternary landforms along the southern San Jacinto fault: Implications for temporal slip rate variability  

NASA Astrophysics Data System (ADS)

Robust age control on faulted landforms with well-constrained offsets is essential to documenting the heterogeneous behavior of a fault zone over time. However, showing late Quaternary temporal slip rate variation is often challenging due to the difficultly of obtaining reliable ages for Quaternary deposits. Exposure ages from cosmogenic isotopes can be significantly affected by surface processes, and U-series dating of pedogenic carbonate provides only minimum ages because carbonate accumulation occurs after deposition. Fortunately, the controlling factors for the resulting age uncertainties of each method are relatively independent from each other, so a combination of cosmogenic isotope and U-series dating may significantly improve the reliability of landform dating and yield more robust slip rate estimates. We present preliminary results of this dual-dating approach at 4 sites along the southern San Jacinto fault zone in California: 2 sites along the Coyote Creek fault, and 2 sites along the Clark fault. These results show age agreement between the two dating methods. Along the southern Clark fault, a 10Be depth profile model age of 34.5 6.6 ka and a U-series age of 33.2 1.1 ka were obtained for an offset Q2b fan surface, and a Q3b surface yielded a weighted mean 10Be surface exposure age of 5.9 1.5 ka, similar to an U-series age of 6.3 0.4 ka. Along the northern Coyote Creek fault, preliminary data indicate a 10Be surface exposure age of 11.3 3.4 ka and a U-series age of 11.7 1.8 ka for an offset Q3a surface, and a 10Be surface exposure age of 6.9 1.0 ka and a U-series age of 7.8 0.9 ka for an offset Q3b surface. The remarkable consistency among ages from the two dating methods suggest that: (1) U-series ages of pedogenic carbonate clast rinds closely approach depositional ages of the host alluvium; (2) erosion may be negligible at the sampled sites; and (3) inherited 10Be has been accurately quantified (via depth profile) for the late Pleistocene deposits, and is negligible for Holocene fans. In general, our results show that, in an arid setting where post-depositional processes are limited and multiple dating techniques can be applied, reliable ages may be obtained to yield robust slip rates across and along fault zones. Preliminary slip-rate results from these sites imply that slip rates may have varied significantly over the late Quaternary, with an ~2x increase since ~8-6 kyr.

Blisniuk, K.; Oskin, M. E.; Fletcher, K.; Sharp, W. D.; Rockwell, T. K.

2009-12-01

92

Origins of 210Pb-226Ra disequilibria in basalts: New insights from the 1978 Asal Rift eruption  

NASA Astrophysics Data System (ADS)

There has been much debate as to whether 210Pb-226Ra disequilibria in young volcanic rocks result from partial melting, cumulate interaction or magma degassing. Here we present new data from basalts erupted in 1978 from Ardoukoba volcano in the Asal Rift. The (210Pb/226Ra)t ratios are very low (0.2 to 0.6) and appear to correlate negatively with (226Ra/230Th). Invariant (230Th/238U) and (231Pa/235U) ratios require similar melting rates, porosities, and extents for all parental magmas. Thus, the range in (226Ra/230Th), which is negatively correlated with Th concentration, reflects fractional crystallization over millennia after the magmas were emplaced into the crust. This precludes the 210Pb deficits from resulting from partial melting. Instead, the 210Pb deficits must have formed subsequent to magma differentiation and are interpreted to reflect several decades of magma degassing. Many young basalts erupted in a variety of tectonic settings are similarly depleted in 210Pb with respect to 226Ra, suggesting that they continuously degas over a period of a few to several decades, perhaps reflecting the time required to rise to the surface from deeper reservoirs. In some of these basalts, gas accumulation leads to the shallowest, most evolved, and earliest erupting magmas having the highest (210Pb/226Ra) ratios and sometimes 210Pb excesses.

Turner, Simon; Reagan, Mark; Vigier, Nathalie; Bourdon, Bernard

2012-07-01

93

Soil formation rates determined from Uranium-series isotope disequilibria in soil profiles from the southeastern Australian highlands  

NASA Astrophysics Data System (ADS)

The sustainability of soil resources is determined by the balance between the rates of production and removal of soils. Samples from four weathering profiles at Frogs Hollow in the upper catchment area of the Murrumbidgee River (southeastern Australia) were analyzed for their uranium-series (U-series) isotopic composition to estimate soil production rates. Sequential leaching was conducted on sample aliquots to assess how U-series nuclides are distributed between primary and secondary minerals. Soil is increasingly weathered from bottom to top which is evident from the decrease in (234U/238U) ratios and increase in relative quartz content with decreasing soil depth. One soil profile shows little variation in mineralogy and U-series geochemistry with depth, explained by the occurrence of already extensively weathered saprolite, so that further weathering has minimal effect on mineralogy and geochemistry. Al2O3 is mobilized from these soils, and hence a silicon-based weathering index treating Al2O3 as mobile is introduced, which increases with decreasing soil depth, in all profiles. Leached and unleached aliquots show similar mineralogy with slight variation in relative concentrations, whereas the elemental and isotopic composition of uranium and thorium show notable differences between leached and unleached samples. Unleached samples show systematic variations in uranium-series isotopic compositions with depth compared to leached samples. This is most likely explained by the mobilization of U and Th from the samples during leaching. Soil residence times are calculated by modeling U-series activity ratios for each profile separately. Inferred timescales vary up to 30 kyr for unleached aliquots from profile F1 to up to 12 kyr for both leached and unleached aliquots from profile F2. Muscovite content shows a linear relationship with U-series derived soil residence times. This relationship provides an alternative method to estimate residence timescales for profiles with significant U-series data scatter. Using this alternative approach, inferred soil residence times up to 33 kyr for leached samples of profile F1 and up to 34 kyr for leached samples of profile F3 were determined. A linear relationship between soil residence times and WIS (Si-based Weathering Index) exists and is used to estimate soil residence times for profile F3 (up to 28 kyr) and F4 (up to 37 kyr). The linear relationship between soil depth and calculated residence time allows determination of soil production rates, which range from 10 to 24 mm/kyr and are comparable to the rates determined previously using cosmogenic isotopes at the same site (Heimsath et al., 2001b). This implies that at this site, on the highland plateau of southeastern Australia, soil thickness has reached steady-state, possibly as a result of stable tectonic conditions but despite variable climatic conditions over the timescale of soil development. Soil-mantled landscapes are the geomorphic expression of this balance between soil production and denudation, and our results show that in tectonically quiescent regions, this landscape can be achieved in less than 30 kyr.

Suresh, P. O.; Dosseto, A.; Hesse, P. P.; Handley, H. K.

2013-10-01

94

Mass spectrometric U-series dating of Huanglong Cave in Hubei Province, central China: Evidence for early presence of modern humans in eastern Asia.  

PubMed

Most researchers believe that anatomically modern humans (AMH) first appeared in Africa 160-190ka ago, and would not have reached eastern Asia until ?50ka ago. However, the credibility of these scenarios might have been compromised by a largely inaccurate and compressed chronological framework previously established for hominin fossils found in China. Recently there has been a growing body of evidence indicating the possible presence of AMH in eastern Asia ca. 100ka ago or even earlier. Here we report high-precision mass spectrometric U-series dating of intercalated flowstone samples from Huanglong Cave, a recently discovered Late Pleistocene hominin site in northern Hubei Province, central China. Systematic excavations there have led to the in situ discovery of seven hominin teeth and dozens of stone and bone artifacts. The U-series dates on localized thin flowstone formations bracket the hominin specimens between 81 and 101ka, currently the most narrow time span for all AMH beyond 45ka in China, if the assignment of the hominin teeth to modern Homo sapiens holds. Alternatively this study provides further evidence for the early presence of an AMH morphology in China, through either independent evolution of local archaic populations or their assimilation with incoming AMH. Along with recent dating results for hominin samples from Homo erectus to AMH, a new extended and continuous timeline for Chinese hominin fossils is taking shape, which warrants a reconstruction of human evolution, especially the origins of modern humans in eastern Asia. PMID:23870460

Shen, Guanjun; Wu, Xianzhu; Wang, Qian; Tu, Hua; Feng, Yue-Xing; Zhao, Jian-Xin

2013-07-16

95

High-resolution mapping of uranium and other trace elements in recrystallized aragonite calcite speleothems from caves in the Pyrenees (France): Implication for U-series dating  

NASA Astrophysics Data System (ADS)

Aragonite and calcite speleothems were sampled in the cave of Pierre Saint-Martin (Pyrnes-Atlantiques, France). These speleothems contain significant amounts of uranium and strontium, which were measured spatially and chemically by nuclear microprobe analysis. Sr and U distributions are highly varied, with a marked contrast between aragonite and calcite because the aragonite concentrates Sr and U. On the other hand, Zn is preferentially located in calcite and in layers of organic matter trapped in CaCO3. Sr contents ranged from 440 to 1100 ?g/g in the calcite and 4900 to 18,500 ?g/g in the aragonite. U concentrations show remarkably high values from 11 to 19 ?g/g in the calcite and 89 to 350 ?g/g in the aragonite. These U and Sr concentrations are amongst the highest measured in supergene speleothems deposited by infiltrating meteoric waters. X-ray absorption experiments with synchrotron radiation suggested that uranium was incorporated in its hexavalent oxidation state in both aragonite and calcite. Recrystallization from aragonite into calcite was indicated by micromorphological observations for some of the samples. This recrystallization process may explain the uranium loss in neogenic calcite deposits and consequently the opening of the geochemical system, which can lead to errors in age dating with the U-series dating method. Uranium loss in recrystallized calcite is one of the important aspects to be considered in U-series dating and more generally for U geochemical stability in CaCO3.

Ortega, Richard; Maire, Richard; Devs, Guillaume; Quinif, Yves

2005-09-01

96

Long-term slip rates of the Elsinore-Laguna Salada fault, southern California, by U-series Dating of Pedogenic Carbonate in Progressively Offset Alluvial fan Remnants.  

NASA Astrophysics Data System (ADS)

The Elsinore-Laguna Salada (ELS) fault is one of the principal strands of the San Andreas fault system in southern California, however its seismic potential is often de-emphasized due to previous estimates of a low slip rate. Nevertheless, the fault zone has produced two historic earthquakes over M6, with the 1892 event estimated at >M7; thus further investigation of the long-term slip rate on the ELS fault is warranted. On the western slopes of the Coyote Mountains (CM), southwest Imperial Valley, a series of alluvial fans are progressively offset by the Elsinore fault. These fans can be correlated to their source drainages via distinctive clast assemblages, thereby defining measurable offsets on the fault. Dating of the CM fans (to compute slip rates), however, is challenging. Organic materials appropriate for C-14 dating are rare or absent in the arid, oxidizing environment. Cosmogenic surface exposure techniques are limited by the absence of suitable sample materials and are inapplicable to numerous buried fan remnants that are otherwise excellent strain markers. Pedogenic carbonate datable by U-series, however, occurs in CM soil profiles, ubiquitously developed in fan gravels, and is apparent in deposits as young as ~1 ka. In CM gravels 10's ka and older, carbonate forms continuous, dense, yellow coatings up to 3 mm thick on the undersides of clasts. Powdery white carbonate may completely engulf clasts, but is not dateable. Carefully selected samples of dense, innermost carbonate lamina weighing 10's of milligrams and analyzed by TIMS, are geochemically favorable for precise U-series dating (e.g., U = 1-1.5 ppm, median 238U/232Th ~ 7), and yield reproducible ages for coatings from the same microstratigraphic horizon (e.g., 48.2 2.7 and 49.9 2.2 ka), indicating that U-Th systems have remained closed and that inherited coatings, though present, have been avoided. Accordingly, U-series on pedogenic carbonate provides reliable minimum ages for deposition of host landforms, thereby facilitating determination of maximum bounds on corresponding slip rates. Results to date show that pedogenic carbonate dating in the CM has a useful range of at least 140 ka, thus progressively offset geomorphic surfaces in the CM study area afford the opportunity to examine the pattern of slip on the Elsinore fault over time scales from circa 10 to >100 ka.

Fletcher, K. E.; Rockwell, T. K.; Sharp, W. D.

2007-12-01

97

The 226Ra-230Th-238U disequilibria of enigmatic magmas from Piton de la Fournaise Volcano, Reunion Island (1950-1998)  

NASA Astrophysics Data System (ADS)

We present a detailed study of the 226Ra-230Th-238U disequilibria and selected incompatible trace-element abundances of lavas from Piton de la Fournaise, a frequently active ocean-island volcano, using high-precision MC-ICP-MS. The samples erupted between 1950-1998 from vents within the summit caldera (Enclos Fouque) or along the rift zones of the volcano. The lavas display a significant range in 226Ra-230Th disequilibria (25-33% excess 226Ra) and 230Th-238U disequilibria (14-20% excess 230Th). The (230Th/232Th) ratios of the lavas are relatively constant (0.9% range) and do not correlate with either Th/U or (230Th/238U). A strong correlation (R2=0.97) between the (230Th/238U) and Th/U ratios suggests that most of the Th-U fractionation in these lavas occurred recently compared to the 76 kyr half-life of 230Th [because the effects of this fractionation are not yet reflected in the (230Th/232Th) ratios]. In contrast, the 226Ra-230Th disequilbria do not correlate with the Ba/Th ratios of the lavas (a geochemical analog). Thus, the range in Ba/Th (6.1%) and (226Ra/230Th) ratios probably results from either more than one magmatic process or a single process operating over a time scale that is longer than the half-life of 226Ra (1600 years). Unlike Hawaiian shield volcanoes, which display systematic temporal geochemical variations on a time scale of decades to centuries, the fluctuations in lava chemistry at Piton de la Fournaise do not display any coherent trends over the last 50 years. Some geochemical parameters [e.g., Ba/U, Nd/Sm or (230Th/238U)] do vary systematically over a period of a few years, but these trends are not observed consistently for the same samples and different geochemical parameters. The origin of these complex variations in lava chemistry at Piton de la Fournaise is enigmatic, but probably includes a combination of mantle (Albarede and Tamagnan, 1988, J. Petrol. v. 29) and crustal (Sigmarsson et al., 2005, EPSL v. 234; Vlastelic et al., 2005, J. Petrol. v. 46) processes. Possible explanations for the data will be explored at the meeting.

Pietruszka, A. J.; Hauri, E. H.; Albarede, F.; Blichert-Toft, J.

2005-12-01

98

Linkage disequilibria among (CA){sub n} polymorphisms in the human dystrophin gene and their implications in carrier detection and prenatal diagnosis in Duchenne and Becker musclar dystrophies  

SciTech Connect

Four short tandem repeat loci, characterized by length polymorphisms of (CA){sub n} repeats, have been detected within introns 44, 45, 49, and 50 of the human dystrophin gene. The predicted heterozygosites for these loci range from 72 to 93%, and observed allele numbers range from 6 to 19 in 57 normal chromosomes, revealing their high degree of polymorphism. Evidence for significant disequilibria between the loci within introns 49 and 50 is found. These data appear to be consistent with observations of recombination frequencies between these markers and the length of the intron 44 in relation to the entire region. In addition, these four loci are collectively found to be 100% informative in carrier detection/prenatal diagnosis of Becker and Duchenne muscular dystrophies (B/DMD), whereas scoring the (CA){sub n} markers within introns 45 and 49 alone gives a 99.6% success rate. 13 refs., 4 tabs.

Chakraborty, R.; Zhong, Y.; Andrade, M. de [Univ. of Texas Graduate School of Biomedical Sciences, Houston, TX (United States)] [and others

1994-06-01

99

Enhancing in-situ U-series accessory mineral chronometry to constrain pace and processes of magma accumulation, storage, and eruption  

NASA Astrophysics Data System (ADS)

Over the past decade, deciphering absolute crystallization ages at micro-scales through in-situ U-series dating has spearheaded conceptual changes in the understanding of how magmas evolve en route to the surface. U-Th and U-Pb zircon geochronology by secondary ionization mass spectrometry (SIMS) now routinely accesses a continuous age spectrum extending well into the Holocene with ka precision for individual analysis spots ~25 - 40 ?m in diameter. SIMS depth profiling further increases spatial resolution at least tenfold. These developments are epitomized by studies that document multiple generations of zircon growth, predating eruptions by 10's to 100's of ka, as common features in silicic volcanics. Recently, these methods have been enhanced by (1) linking ages to Ti-in-zircon thermometry and trace element or oxygen isotopic fingerprinting; (2) tracking compositional changes with age in accessory minerals sensitive to magma differentiation, such as allanite; and (3) combining U-Th zircon ages with other chronometers, such as (U-Th)/He zircon or 226Ra-230Th-238U plagioclase dating. The emerging picture reveals a wide gamut of processes acting in magma bodies, including piecemeal, compartmentalized magma aggregation, protracted and thermally retrograde crystal storage coupled with magma differentiation, thermal rejuvenation and recycling of crystal mushes and solidified intrusions or magma chamber rinds, and wall rock assimilation. For the future, experimental constraints on accessory mineral-melt partitioning (e.g., Ayers and Luo, 2008: Geochim Cosmochim Acta, v. 72, p. A39) promise to put interpretation of zircon compositions on firmer footing, as is the case for additional accessory mineral saturation calibrations and improved modeling of existing ones (e.g., Harrison et al., 2007: Geology, v. 35, p. 635-638). By the same token, new experimental constraints on U-series element partitioning (e.g., Miller et al., 2007: Am Min, v. 92, p. 1535-1538) should enhance precision and applicability of mineral chronometers. Moreover, analytical advances in high spatial resolution SIMS hold promise for utilizing melt inclusions in zircon as an additional repository for constraining the chemical and thermal evolution of magmas.

Schmitt, A. K.

2008-12-01

100

238U-234U-230Th disequilibria and the sediment transit time in alluvial plains: examples from the Gangetic plain rivers  

NASA Astrophysics Data System (ADS)

The mechanisms and timescales of processes controlling the sediment formation and their transfers from continent to ocean are a prerequisite for correctly quantifying the rates of continental erosion but also for precisely evaluating the response of the erosion and sedimentation processes to tectonic and climatic forcing. Here we propose to illustrate, in the case of the Gangetic plain river system, the interest of 238U-234U-230Th disequilibria in the bank-river sediments for estimating the transfer time of sediments in the alluvial plains. The studied rivers involve (1) mountain-fed rivers, i.e. river transferring a great quantity of sediments from their source of high relief and forming large depositional areas in the plain, and (2) a foothill-fed river, that derives its sediments from foothills and from within the plains, and for which a large proportion of this material is redeposited after local reworking. The main result displayed by the U-Th data is a regular evolution of the 238U-230Th-232Th systematics along the rivers with a systematic decrease of both (238U/232Th) and (230Th/232Th) ratios in river-bank sediments from upstream to downstream. The variations can be related to mineralogical and chemical sediment evolution during their transfer (and storage) in the alluvial plains and valleys. The choice of a realistic model for the U and Th evolution model during the transfer of alluvions in the valleys and plains allows us to estimate the transit time of sediments in the Gangetic plain : about 100 ka for rivers taking their source in the himalayan chain, and longer transit-time of about 160-250 ka for foothill-fed rivers. This difference is probably related to the difference in the sediment transport dynamics of these two types of rivers. These results highlight the potential of the 238U-234U-230Th disequilibria to constrain the dynamic of the sedimentary transfers in the alluvial plains.

Chabaux, F. J.; Granet, M.; Pelt, E.; Franc-Lanord, C.; Galy, V.

2005-12-01

101

Hydrological implications of 234U/238U disequilibria observed along pressure dissolution discontinuities in deep Mesozoic limestone formations of the Eastern Paris basin  

NASA Astrophysics Data System (ADS)

Borehole core samples from the deep, low-permeability Mesozoic formations surrounding the target argilite layer of the Meuse/Haute-Marne experimental site of the French agency for nuclear waste management -ANDRA- were analyzed for their uranium isotopic abundance. This study attempts to decipher the history and the processes governing the mobility of uranium in such geological settings by means of precise measurements of the (234U/238U) activity ratio. Limestone zones characterized by pressure dissolution structures (stylolites or dissolution seams) display systematic (234U/238U) disequilibria: i) the material within the seams shows a deficit of 234U over 238U ((234U/238U) down to 0.80) and ii) the surrounding carbonate matrix is characterized by an activity ratio greater than unity (up to 1.05). These results highlight a discret, centimetric-scale uranium remobilization in the limestone formations along these sub-horizontal seams during the last 1-2 Ma and, consequently, active water/rock interaction processes since fractionation of 234U vs 238U necessary involves exchanges at the water/rock interface and migration via interstitial fluid. The nature and the modalities of the driving processes responsible for these disequilibria are not unequivocal, but different scenarios can be put forward to explain the U-remobilization observed: 1) late epidiagenetic processes associated to the presence of pressure dissolution structures, or 2) preferential fluid circulation along the stylolitic pathway. The major consequences in terms of the conceptual modeling of the hydrology behavior of the formations and, obviously, on the site performance assessment, are discussed.

Deschamps, P.; Hillaire-Marcel, C.; Michelot, J.; Doucelance, R.; Ghaleb, B.; Bushaert, S.

2004-05-01

102

Mantle Heterogeneity and Melting Along a Regional Axial Depth Gradient: Th-U Disequilibria Along the Southeast Indian Ridge  

NASA Astrophysics Data System (ADS)

Lateral variation in mantle temperature is generally considered to be the main cause for observed global correlations between regionally averaged mid-ocean ridge basalt (MORB) chemistry and ridge axis depth (Klein and Langmuir, 1987). Axial depth should be shallower above hotter mantle because the underlying mantle crosses its solidus at greater depth compared to cooler regions, and leads to greater crustal production. One expectation of this global model is that melting beneath ridges should involve progressively more (deep) garnet peridotite as ridge depth shallows. A negative correlation between (230Th/238U) and axial depth in a global dataset (largely dominated by eastern Pacific and Atlantic MORB) generally supports this notion, because garnet is known to fractionate Th from U during melting (Bourdon et al., 1996). The extent to which such global variations reflect only variations in melting conditions of passively upwelling mantle versus other conditions related to mantle heterogeneity or actively fed melting anomalies is presently unknown. To further address this question on the regional scale, we have measured Th-U isotopes on 11 basaltic glasses collected along the Southeast Indian Ridge (SEIR) from 90 E to 117 E. This 2600 km section of ridge is characterized by a west to east gradient in axial depth from 2300 m to >4500 m, similar to that of the global ridge system away from the influence of hotspots. However, unlike the global (230Th/238U)-axial depth correlation which uses regionally averaged data for ridge segments from a range of spreading rates, the SEIR is spreading at a nearly constant rate of 70-75 mm/yr and is devoid of large transform offsets. These first 11 SEIR glasses were selected to span the geographic range and to be representative of the elemental and isotopic compositions. Th and U concentrations range from 130-940 ppb and 55-267 ppb, respectively, with Th/U values ranging from 2.36 to 3.77. All samples show 230Th excesses, with (230Th/238U) ranging from 1.01 to 1.24. There is no correlation between (230Th/238U) and axial depth, in contrast to the simple prediction from the global scale model. On a (238U/232Th)-(230Th/232Th) equiline diagram the SEIR data form 3 geographical, non-collinear groupings: three basalts from the westernmost portion of our study area have the highest (230Th/232Th) and (238U/232Th), the easternmost basalt has significantly lower values, and basalts from a central region (101 E to 114 E) have intermediate values. The 7 central region basalts form a well-correlated positively sloping (230Th/232Th) vs. (238U/232Th) array which is shallower than the equiline and extends from 7% to 24% 230Th-excess. Overall, (230Th/232Th) shows a strong negative correlation with axial depth and, along with Th/U, correlates well with other isotopic tracers such as 3He/4He and 208Pb/206Pb, which vary systematically along axis. In contrast, (230Th/238U) shows no systematic variations with these isotopic parameters or axial depth. Unlike the global dataset, the Th-U disequilibria in SEIR MORB suggests that, at a regional scale, melting in the Indian Ocean mantle is primarily controlled by variations in mantle composition.

Russo, C. J.; Rubin, K. H.; Graham, D. W.

2004-12-01

103

High resolution analysis of uranium and thorium concentration as well as U-series isotope distributions in a Neanderthal tooth from Payre (Ardche, France) using laser ablation ICP-MS  

NASA Astrophysics Data System (ADS)

We have mapped U ( 238U) and Th ( 232Th) elemental concentrations as well as U-series isotope distributions in a Neanderthal tooth from the Middle Palaeolithic site of Payre using laser ablation ICP-MS. The U-concentrations in an enamel section varied between 1 and 1500 ppb. The U-concentration maps show that U-migration through the external enamel surface is minute, the bulk of the uranium having migrated internally via the dentine into the enamel. The uranium migration and uptake is critically dependent on the mineralogical structure of the enamel. Increased U-concentrations are observed along lineaments, some of which are associated with cracks, and others may be related to intra-prismatic zones or structural weaknesses reaching from the dentine into the enamel. The uranium concentrations in the dentine vary between about 25,000 and 45,000 ppb. Our systematic mapping of U-concentration and U-series isotopes provides insight into the time domain of U-accumulation. Most of the uranium was accumulated in an early stage of burial, with some much later overprints. None of the uranium concentration and U-series profiles across the root of the tooth complied with a single stage diffusion-adsorption (D-A) model that is used for quality control in U-series dating of bones and teeth. Nevertheless, in the domains that yielded the oldest apparent U-series age estimates, U-leaching could be excluded. This means that the oldest apparent U-series ages of around 200 ka represent a minimum age for this Neanderthal specimen. This is in good agreement with independent age assessments (200-230 ka) for the archaeological layer, in which it was found. The Th elemental concentrations in the dental tissues were generally low (between about 1 and 20 ppb), and show little relationship with the nature of the tissue.

Grn, Rainer; Aubert, Maxime; Joannes-Boyau, Renaud; Moncel, Marie-Hlne

2008-11-01

104

Properties of Natural Radiation and Radioactivity  

SciTech Connect

Ubiquitous natural sources of radiation and radioactive material (naturally occurring radioactive material, NORM) have exposed humans throughout history. To these natural sources have been added technologically-enhanced naturally occurring radioactive material (TENORM) sources and human-made (anthropogenic) sources. This chapter describes the ubiquitous radiation sources that we call background, including primordial radionuclides such as 40K, 87Rb, the 232Th series, the 238U series, and the 235U series; cosmogenic radionuclides such as 3H and 14C; anthropogenic radionuclides such as 3H, 14C, 137Cs, 90Sr, and 129I; radiation from space; and radiation from technologically-enhanced concentrations of natural radionuclides, particularly the short-lived decay products of 222Rn ("radon") and 220Rn ("thoron") in indoor air. These sources produce radiation doses to people principally via external irradiation or internal irradiation following intakes by inhalation or ingestion. The effective doses from each are given, with a total of 3.11 mSv y-1 (311 mrem y-1) to the average US resident. Over 2.5 million US residents receive over 20 mSv y-1 (2 rem y-1), primarily due to indoor radon. Exposure to radiation from NORM and TENORM produces the largest fraction of ubiquitous background exposure to US residents, on the order of 2.78 mSv (278 mrem) or about 89%. This is roughly 45% of the average annual effective dose to a US resident of 6.2 mSv y-1 (620 mrem y-1) that includes medical (48%), consumer products and air travel (2%), and occupational and industrial (0.1%). Much of this chapter is based on National Council on Radiation Protection and Measurements (NCRP) Report No. 160, "Ionizing Radiation Exposure of the Population of the United States," for which the author chaired the subcommittee that wrote Chapter 3 on "Ubiquitous Background Radiation."

Strom, Daniel J.

2009-07-13

105

Timscales of rhyodacite formation in Central America: U-series disequilibrium and implications for petrogenetic processes in El Salvador and Nicaragua.  

NASA Astrophysics Data System (ADS)

U-series isotopes were measured for rhyodacites from three calderas in El Salvador and Nicaragua along the Central American arc. These data reflect a general trend of increasing (230Th/232Th) from north to south along the arc system. Whole rocks and mineral separates from Ilopongo caldera, El Salvador have (230Th/232Th) of ~ 1.5, and (238U/230Th) of 0.8-1.9. A basaltic enclave from a dome within Ilopongo caldera has a slightly higher (230Th/232Th) of 1.6. Mineral-separate isochrons from this system are consistent with the young age (1600 yrs) of Ilopongo caldera. ^{226}Ra/^{228}Ra were also measured for the Ilopongo samples, and calculated (^{226}Ra/230Th) show a range in values from 0.9- 1.2. To the south of Ilopongo, dacites from Apoyeque caldera, Nicaragua have (230Th/232Th) of 2.5- 2.7, the highest values measured in Central America using plasma mass spectrometry. Rhyodacites from nearby Apoyo caldera, Nicaragua have (230Th/232Th) of ~ 2.2, with the exception of one basalt sample that has (230Th/232Th) of ~ 1.8. These values are consistent with previous measurements for Apoyo caldera. All samples have 230Th excesses, with the exception of one Apoyeque sample that is in equilibrium. In general, volcanic rocks from the Central American arc have ^{143}Nd/^{144}Nd values that are elevated above the mantle array and reflect addition of a high-^{143}Nd/^{144}Nd component from the slab. These new data suggest that this component is also likely to have high (230Th/232Th). Positive correlations between (230Th/232Th) and Ba/Th and also Ce/Pb indicate that this component is likely carried by both fluid and sediment. These data reflect a systematic, southward change in petrogenetic processes operating beneath the Central American arc.

Garrison, J. M.; Reagan, M. R.; Sims, K. W.; Patino, L. C.

2006-12-01

106

Origins of large-volume, compositionally zoned volcanic eruptions: New constraints from U-series isotopes and numerical thermal modeling for the 1912 Katmai-Novarupta eruption  

USGS Publications Warehouse

We present the results of a combined U-series isotope and numerical modeling study of the 1912 Katmai-Novarupta eruption in Alaska. A stratigraphically constrained set of samples have compositions that range from basalt through basaltic andesite, andesite, dacite, and rhyolite. The major and trace element range can be modeled by 8090% closed-system crystal fractionation over a temperature interval from 1279C to 719C at 100 MPa, with an implied volume of parental basalt of ?65 km3. Numerical models suggest, for wall rock temperatures appropriate to this depth, that 90% of this volume of magma would cool and crystallize over this temperature interval within a few tens of kiloyears. However, the range in 87Sr/86Sr, (230Th/238U), and (226Ra/230Th) requires open-system processes. Assimilation of the host sediments can replicate the range of Sr isotopes. The variation of (226Ra/230Th) ratios in the basalt to andesite compositional range requires that these were generated less than several thousand years before eruption. Residence times for dacites are close to 8000 years, whereas the rhyolites appear to be 50200 kyr old. Thus, the magmas that erupted within only 60 h had a wide range of crustal residence times. Nevertheless, they were emplaced in the same thermal regime and evolved along similar liquid lines of descent from parental magmas with similar compositions. The system was built progressively with multiple inputs providing both mass and heat, some of which led to thawing of older silicic material that provided much of the rhyolite.

Turner, Simon; Sandiford, Mike; Reagan, Mark; Hawkesworth, Chris; Hildreth, Wes

2010-01-01

107

Natural and man-made radioactivity in soils and plants around the research reactor of Inshass  

Microsoft Academic Search

The specific radioactivities of the U-series, 232Th, 137Cs and 40K were measured in soil samples around the Inshass reactor in Cairo, using a ?-ray spectrometer with a HpGe detector. The ?-activity of 238U, 234U and 235U was measured in the same soil samples by surface barrier detectors after radiochemical separation and the obtained results were compared with the specific activities

R. H. Higgy; M. Pimpl

1998-01-01

108

Radioactivity Calculations  

ERIC Educational Resources Information Center

Three problems in radioactive buildup and decay are presented and solved. Matrix algebra is used to solve the second problem. The third problem deals with flux depression and is solved by the use of differential equations. (LC)

Onega, Ronald J.

1969-01-01

109

Radioactivity Calculations  

ERIC Educational Resources Information Center

|Three problems in radioactive buildup and decay are presented and solved. Matrix algebra is used to solve the second problem. The third problem deals with flux depression and is solved by the use of differential equations. (LC)|

Onega, Ronald J.

1969-01-01

110

Radioactive Wastes  

NSDL National Science Digital Library

The purposes of this module are to develop multiple representations for decay of radioactive substances, in the context of environmental policies on a university campus, and to determine storage times for wastes to decay to safe levels for disposal.

Smith, David; Moore, Lang

2000-09-02

111

Radioactive Wastes  

NSDL National Science Digital Library

This module develops multiple representations for decay of radioactive substances, in the context of environmental policies on a university campus, and discusses storage times for wastes to decay to safe levels for disposal.

Smith, David

2000-09-02

112

Radioactive Decay  

NSDL National Science Digital Library

With knowledge of Maple, Mathmatica, or MatLab, one should be able to develop a mathematical model for decay of radioactive substances and develop a technique for deciding whether quantitative data fits the model or not.

Smith, David

2001-01-22

113

Rates of late Quaternary normal faulting in central Tibet from U-series dating of pedogenic carbonate in displaced fluvial gravel deposits  

NASA Astrophysics Data System (ADS)

Along the main boundary fault of the central Tibetan Shuang Hu graben, two well-preserved fluvial terrace surfaces are vertically offset by ~1.3 m (terrace I) and ~14.8 m (terrace II). Using thermal ionization mass spectrometry (TIMS), we have determined 48 230Th-234U-238U ages of small (10-40 mg) samples from pedogenic carbonate rinds on clasts in the terrace deposits. Based on textural, microstratigraphic and geochemical criteria, we conclude that the U-series ages of innermost-rind samples provide reliable ages of 16.4+/-1.9 ka for terrace I, and 233.1+/-9.3 ka for terrace II. This constrains the average rate of vertical displacement along the normal fault to be 0.079+/-0.011 mm/yr during the past ~16 kyr, and 0.064+/-0.007 mm/yr during the past ~233 kyr. Combining these results with slip-rate estimates for other normal faults along the graben margins indicates that the cumulative vertical displacement on all normal faults did not exceed ~0.3 mm/yr during the late Quaternary. This new rate from central Tibet is distinctly lower than the rate of 1.9+/-0.6 mm/yr inferred for normal faults bounding the Yadong-Gulu graben system in southern Tibet, consistent with more pronounced and common graben development in southern Tibet. We therefore suggest that normal faulting in southern Tibet is largely controlled by local processes, and that the age of its initiation is not a valid proxy for uplift of the Tibetan plateau, as has been widely assumed. Our data also place chronologic constraints on the termination of periglacial conditions in central Tibet during the last three interglaciations. Rind formation appears to have been relatively continuous on clasts in terrace I from ~16 ka. Clast rinds from terrace II, in contrast, are characterized by three main episodes of rind growth that are widely separated in time. The earliest and least well-preserved episode started at 233.1+/-9.3 ka, a second episode occurred at 131.8+/-7.8 ka, and a third episode was approximately coeval with rind formation in terrace I after 16.4+/-1.9 ka. In each case, the age of onset of carbonate rind accumulation coincides with independently estimated ages of global deglaciation. Accordingly, we conclude that periglacial conditions in the central Tibetan plateau terminated synchronously with early stages of global warming following the last three glacial maxima, and that fluvial aggradation, terrace formation, and pedogenic carbonate accumulation in terrace soils ensued rapidly.

Blisniuk, Peter M.; Sharp, Warren D.

2003-10-01

114

RADIOACTIVE BATTERY  

DOEpatents

A radioactive battery which includes a capsule containing the active material and a thermopile associated therewith is presented. The capsule is both a shield to stop the radiations and thereby make the battery safe to use, and an energy conventer. The intense radioactive decay taking place inside is converted to useful heat at the capsule surface. The heat is conducted to the hot thermojunctions of a thermopile. The cold junctions of the thermopile are thermally insulated from the heat source, so that a temperature difference occurs between the hot and cold junctions, causing an electrical current of a constant magnitude to flow.

Birden, J.H.; Jordan, K.C.

1959-11-17

115

Radioactive Wastes  

NSDL National Science Digital Library

Created by David Smith for the Connected Curriculum Project, this module develops multiple representations for decay of radioactive substances, in the context of environmental policies on a university campus, and discusses storage times for wastes to decay to safe levels for disposal. This is one of a much larger set of learning modules hosted by Duke University.

Smith, David

2010-04-29

116

Radioactive Decay  

NSDL National Science Digital Library

Created by William Barker and David Smith for the Connected Curriculum Project, the purposes of this module are to develop a mathematical model for decay of radioactive substances, and to develop a technique for deciding whether quantitative data fits the model or not. This is one lesson within a larger set of learning modules hosted by Duke University.

Smith, David; Barker, William

2010-07-05

117

Radioactive Decay  

NSDL National Science Digital Library

Created by William Barker and David Smith for the Connected Curriculum Project, this module develops a mathematical model for decay of radioactive substances, and a technique for deciding whether quantitative data fits the model or not. This is one within a much larger set of learning modules hosted by Duke University.

Smith, David; Barker, William

2010-06-28

118

Radioactive Waste.  

ERIC Educational Resources Information Center

|Presents a literature review of radioactive waste disposal, covering publications of 1976-77. Some of the studies included are: (1) high-level and long-lived wastes, and (2) release and burial of low-level wastes. A list of 42 references is also presented. (HM)|

Blaylock, B. G.

1978-01-01

119

Early diagenesis impact on precise U-series dating of deep-sea corals: Example of a 100200-year old Lophelia pertusa sample from the northeast Atlantic  

Microsoft Academic Search

Deep-sea coral has proved useful for paleoceanographic reconstructions and for documenting 14C-ages of water masses using 230Th-ages. However, for precise and accurate U-series dating, further information on coral-age structure, growth rate and diagenetic evolution is still needed. To document such processes, we used U-Th-226Ra systematics in a 40 cm diameter, Lophelia pertusa specimen collected in 1912 from the Eastern Atlantic

Edwige Pons-Branchu; Claude Hillaire-Marcel; Pierre Deschamps; Bassam Ghaleb; Daniel J. Sinclair

2005-01-01

120

Radioactive Wastes  

NSDL National Science Digital Library

Created by Lang Moore and David Smith for the Connected Curriculum Project, the purposes of this module are to develop multiple representations for decay of radioactive substances, in the context of environmental policies on a university campus, and to determine storage times for wastes to decay to safe levels for disposal. This is one lesson within a larger set of learning modules hosted by Duke University.

Smith, David; Moore, Lang

2010-07-06

121

Radioactive wastes  

Microsoft Academic Search

A review is presented of the treatment, storage, fixation and disposal of radioactive wastes. Various methods are described for extracting and separating the radionuclides, for example ¹³⁴Cs, ¹³⁷Cs, ²°⁴Tl and ⁶°Co ions were simultaneously deactivated on natural sorbents by precipitation reactions. For long term storage, wastes should be solidified and immobilized to ensure containment, reduce surveillance, and reduce the need

Straub

1977-01-01

122

Investigation of aerial dispersion of radioactive dust from an open-pit uranium mine by passive vinyl collectors  

Microsoft Academic Search

Detailed investigations of the aerial dispersion of radioactive dust from the biggest open-pit U mining and milling operation in Australia were carried out. Spatial distributions of the long-lived radionuclides of ²³⁸U series and their origin, i.e., mining and milling operations vs. natural background radiation, have been studied. Horizontal flux, dry deposition, and ground resuspension of the radionuclides were investigated along

H. B. L. Pettersson; J. Koperski

1991-01-01

123

Improved spatial resolution for U-series dating of opal at Yucca Mountain, Nevada, USA, using ion-microprobe and microdigestion methods  

USGS Publications Warehouse

Two novel methods of in situ isotope analysis, ion microprobe and microdigestion, were used for 230Th/U and 234U/238U dating of finely laminated opal hemispheres formed in unsaturated felsic tuff at Yucca Mountain, Nevada, proposed site for a high-level radioactive waste repository. Both methods allow analysis of layers as many as several orders of magnitude thinner than standard methods using total hemisphere digestion that were reported previously. Average growth rates calculated from data at this improved spatial resolution verified that opal grew at extremely slow rates over the last million years. Growth rates of 0.58 and 0.69 mm/m.y. were obtained for the outer 305 and 740 ??m of two opal hemispheres analyzed by ion microprobe, and 0.68 mm/m.y. for the outer 22 ??m of one of these same hemispheres analyzed by sequential microdigestion. These Pleistocene growth rates are 2 to 10 times slower than those calculated for older secondary calcite and silica mineral coatings deposited over the last 5 to 10 m.y. dated by the U-Pb method and may reflect differences between Miocene and Pleistocene seepage flux. The microdigestion data also imply that opal growth rates may have varied over the last 40 k.y. These data are the first indication that growth rates and associated seepage in the proposed repository horizon may correlate with changes in late Pleistocene climate, involving faster growth during wetter, cooler climates (glacial maximum), slower growth during transition climates, and no growth during the most arid climate (modern). Data collected at this refined spatial scale may lead to a better understanding of the hydrologic variability expected within the thick unsaturated zone at Yucca Mountain over the time scale of interest for radioactive waste isolation. ?? 2004 Elsevier Ltd.

Paces, J. B.; Neymark, L. A.; Wooden, J. L.; Persing, H. M.

2004-01-01

124

Rapid crystal recycling at Krafla Volcano, Iceland, inferred from oxygen-isotope and trace- element compositions and U-Th-Ra disequilibria in plagioclase  

NASA Astrophysics Data System (ADS)

The Icelandic central volcano of Krafla exhibits increasing assimilation of hydrothermally-altered crust with increasing differentiation of magmas, as evidenced by decreasing ?18O with decreasing MgO (Nicholson et al., 1991, J Pet 32, p.1005). The Krafla Fires eruption (1975-84) produced two different magma compositions simultaneously: quartz tholeiites near the center of the volcano, and olivine tholeiites north of the central volcano (Gronvold et al., 2008, Goldschmidt abstract). Examination of crystals in these magmas has the potential to provide information about the nature and timescales of mixing of distinct magmas and assimilation of crustal material at Krafla. We present oxygen-isotope compositions, trace-element compositions, and 238U-230Th-226Ra disequilibria measured in plagioclase crystals from samples of lavas erupted during two phases of the Krafla Fires eruption (ol tholeiite erupted Jan-Feb 1981, and qz tholeiite erupted Nov 1981). Oxygen-isotope data for multiple size fractions of plagioclase show a decrease in ?18O with increasing crystal size for the ol tholeiite (from ~4.1 permil to 3.5 permil), whereas there is no clear relationship between plagioclase size and oxygen-isotope composition in the qtz tholeiite (all size fractions average 4.1-4.3 permil). Furthermore, all measured plagioclase have ?18O lower than would be in equilibrium with the whole rock measurements (by up to 1.5 permil). These data imply that (1) few or none of the measured crystals precipitated from the host liquids, and (2) the crystals were entrained in the host magmas shortly prior to eruption, allowing them to maintain oxygen isotopic disequilibrium and heterogeneity within the crystal populations. These inferences are corroborated by trace element compositions measured in plagioclase by laser-ablation ICPMS, as the majority of analyzed points have Ba and Sr concentrations inconsistent with equilibrium partitioning between crystals and liquid. Furthermore, in the case of the olivine tholeiite, large (>125 microns) and small (<125 microns) size fractions of plagioclase have distinct REE patterns, suggesting that at least two foreign crystal components are present within this magma. Ra-Th model ages of all analyzed plagioclase fractions are undefined after correction for Ra/Ba fractionation during crystallization, suggesting that the liquid from which the measured plagioclase precipitated had higher Ra/Ba ratios than the host liquids. The preservation of Ra-Th disequilibria in the plagioclase crystals indicates that they (and presumably the magma that was their source) is young (<10 ka). The low ?18O of plagioclase suggests that the plagioclase source had assimilated more low-?18O crustal material than the host magmas. However, ?18O of a magma in equilibrium with the plagioclase would still lie within the range for mafic magmas from Krafla, and the major-element compositions of analyzed plagioclase are close to equilibrium with the host liquids, suggesting that the plagioclase crystals are antecrysts derived from a crystal mush or recently-solidified intrusion of basaltic magma within the Krafla reservoir system. In the case of the olivine tholeiite, more than one population of antecrysts are present, implying interaction with crystals derived from more than one earlier magma body, and suggesting that this process is common beneath Krafla.

Cooper, K. M.; Sims, K. W.; Eiler, J. M.; Banerjee, N. R.

2008-12-01

125

Comparing POC export from 234Th/ 238U and 210Po/ 210Pb disequilibria with estimates from sediment traps in the northwest Mediterranean  

NASA Astrophysics Data System (ADS)

We compare POC fluxes estimated using 234Th/ 238U and 210Po/ 210Pb disequilibria at the DYFAMED site, northwestern Mediterranean Sea. We also compare the POC fluxes estimated from these two isotope pairs with fluxes below the euphotic zone measured in moored sediment traps. The POC flux at 200 m estimated from 234Th and 210Po deficits and the POC/ 210Po or POC/ 234Th on >70 ?m filterable particles measured through three seasons (early spring, late spring, summer) ranged from 3.8 to 17.5 mmol C/m 2/d based on 234Th/ 238U and from 4.4 to 7.0 mmol C/m 2/d based on 210Po/ 210Pb disequilibrium. In comparison, sediment trap fluxes of POC at approximately 200 m ranged from 0.2 to 6.0 mmol C/m 2/d over the same interval. Values of POC/ 210Po and POC/ 234Th ratios in sediment trap material collected in time series or separated according to settling velocity (SV) were generally lower than values in the >70 ?m filterable particles at the same depth. The variation in POC/ 210Po and POC/ 234Th in material separated according to SV showed no clear relationship with SV and was controlled more by particle composition and degree of degradation. Both 234Th and 210Po showed sustained deficits in late spring and summer, despite low fluxes recorded in the trap. Lateral processes (transport of particles along isopycnals or intrusion of shelf waters to the site) and violations of temporal assumptions (steady-state vs. non-steady-state) may be responsible for this disparity. Based on the results of this study, we conclude that 210Po/ 210Pb disequilibrium is as valid as 234Th/ 238U as a proxy for estimating POC flux in the ocean.

Stewart, G.; Cochran, J. K.; Miquel, J. C.; Masqu, P.; Szlosek, J.; Rodriguez y Baena, A. M.; Fowler, S. W.; Gasser, B.; Hirschberg, D. J.

2007-09-01

126

238U series isotopes and 232Th in carbonates and black shales from the Lesser Himalaya: implications to dissolved uranium abundances in Ganga-Indus source waters.  

PubMed

238U and (232)Th concentrations and the extent of (238)U-(234)U-(230)Th radioactive equilibrium have been measured in a suite of Precambrian carbonates and black shales from the Lesser Himalaya. These measurements were made to determine their abundances in these deposits, their contributions to dissolved uranium budget of the headwaters of the Ganga and the Indus in the Himalaya and to assess the impact of weathering on (238)U-(234)U-(230)Th radioactive equilibrium in them. (238)U concentrations in Precambrian carbonates range from 0.06 to 2.07 microg g(-1). The 'mean' U/Ca in these carbonates is 2.9 ng U mg(-1) Ca. This ratio, coupled with the assumption that all Ca in the Ganga-Indus headwaters is of carbonate origin and that U and Ca behave conservatively in rivers after their release from carbonates, provides an upper limit on the U contribution from these carbonates, to be a few percent of dissolved uranium in rivers. There are, however, a few streams with low uranium concentrations, for which the carbonate contribution could be much higher. These results suggest that Precambrian carbonates make only minor contributions to the uranium budget of the Ganga-Indus headwaters in the Himalaya on a basin wide scale, however, they could be important for particular streams. Similar estimates of silicate contribution to uranium budget of these rivers using U/Na in silicates and Na* (Na corrected for cyclic and halite contributions) in river waters show that silicates can contribute significantly (approximately 40% on average) to their U balance. If, however, much of the uranium in these silicates is associated with weathering resistant minerals, then the estimated silicate uranium component would be upper limits. Uranium concentration in black shales averages about 37 microg g(-1). Based on this concentration, supply of U from at least approximately 50 mg of black shales per liter of river water is needed to balance the average river water U concentration, 1.7 microg L(-1) in the Ganga-Indus headwaters. Data on the abundance and distribution of black shales in their drainage basin are needed to test if this requirement can be met. (234)U/(238)U activity ratios in both carbonates and black shales are at or near equilibrium, thus preferential mobilization of (234)U from these deposits, if any, is within analytical uncertainties. (230)Th is equivalent to or in excess of (238)U in most of the carbonates. (230)Th/(238)U>1 indicates that during weathering, uranium is lost preferentially over Th. (232)Th concentrations in carbonates are generally quite low, <0.5 microg g(-1), though with a wide range, 0.01-4.8 microg g(-1). The variation in its concentrations seem to be regulated by aluminosilicate content of the carbonates as evident from the strong positive correlation between (232)Th and Al. PMID:12634002

Singh, S K; Dalai, Tarun K; Krishnaswami, S

2003-01-01

127

238U-230Th-226Ra-210Pb disequilibria study of the Nyiragongo volcanics from the East African Rift: implications for timescales of magmatic processes and eruption ages  

NASA Astrophysics Data System (ADS)

The silica-undersaturated Nyiragongo volcanics, located in the East African rift, show globally unique chemical compositions and among the lowest recorded viscosity among terrestrial silicate magmas, only higher than carbonatite lavas. We report 238U-230Th-226Ra-210Pb series disequilibria in 13 recent and prehistoric lava samples from Nyiragongo including those from the 2002 flank eruption and a 2003 lava lake sample. (230Th/238U) ranges from 0.90-0.97 in the recent lavas and from 0.94-1.09 in the prehistoric lavas. To explain the variable 230Th and 238U excesses in these lavas, we hypothesize that different processes with opposite effects in terms of fractionating Th/U in the mantle source are involved. These processes include: 1) low degree partial melting of a phlogopite-bearing mantle source (consistent with low K/Rb) with residual garnet (consistent with high chondrite-normalized Dy/Yb), to produce the observed 230Th excesses; and, 2) carbonate metasomatism for the 238U enrichment, consistent with high Zr/Hf in the Nyiragongo lavas. The Nyiragongo volcanics have higher (230Th/232Th) values than observed in most mantle-derived rocks, especially ocean-island basalts, suggesting that their mantle-source was affected by carbonate metasomatism less than 300 ka ago. Several Nyiragongo samples display significant 226Ra excesses implying rapid magma transport (less than 8 ka) from the mantle-source to the surface. Modeling the observed (226Ra/230Th) versus Zr/Hf correlation in the lavas indicates that the 2002, 2003 and a few pre-historic lavas incorporated 50-60% of a carbonate-metasomatized mantle source while the other pre-historic lavas show 10-22% contribution of this source. This result indicates that the Nyiragongo lavas were derived from a heterogeneous, non-uniformly carbonated mantle source. The 2002 lava shows (210Pb/226Ra) equilibrium, whereas the 2003 lava lake sample shows initial (210Pb/226Ra) < 1. The latter observation suggests that Nyiragongo magmas degas as they rise to the surface over years or decades before eruption. (210Pb/226Ra) equilibrium in the 2002 lava suggests that the 2002 magma may have stagnated for more than a decade before eruption. The high CO2 content, high emission rates, extreme fluidity, along with the inferred short residence time and our inferences of rapid magma transport and high eruption frequency suggest that the volcanic hazards of Nyiragongo, both from lava flows and gas emissions, are higher than previously estimated.

Chakrabarti, R.; Sims, K. W.; Basu, A. R.; Reagan, M. K.; Durieux, J.

2009-12-01

128

Timescales of magmatic processes and eruption ages of the Nyiragongo volcanics from 238U- 230Th- 226Ra- 210Pb disequilibria  

NASA Astrophysics Data System (ADS)

The silica-undersaturated Nyiragongo volcanics, located in the East African Rift, have globally unique chemical compositions and unusually low viscosities, only higher than carbonatite lavas, for terrestrial silicate magmas. We report 238U- 230Th- 226Ra- 210Pb series disequilibria in 13 recent and prehistoric lava samples from Nyiragongo including those from the 2002 flank eruption and a 2003 lava lake sample. ( 230Th/ 238U) ranges from 0.90 to 0.97 in the recent lavas and from 0.94 to 1.09 in the prehistoric lavas. To explain the variable 230Th and 238U excesses in these lavas, we hypothesize that different processes with opposite effects in terms of fractionating Th/U in the mantle source are involved. These processes include: 1) low degree partial melting of a phlogopite-bearing mantle source (consistent with low K/Rb) with residual garnet (consistent with high chondrite-normalized Dy/Yb), to produce the observed 230Th excesses; and, 2) carbonate metasomatism for the 238U enrichment, consistent with high Zr/Hf in the Nyiragongo lavas. The Nyiragongo volcanics have higher ( 230Th/ 232Th) values than observed in most mantle-derived rocks, especially ocean-island basalts, suggesting that their mantle source was affected by carbonate metasomatism less than 300 ka ago. Several Nyiragongo samples display significant 226Ra excesses implying rapid magma transport (less than 8 ka) from the mantle source to the surface. Modeling the observed ( 226Ra/ 230Th) versus Zr/Hf correlation in the lavas indicates that the 2002, 2003 and a few prehistoric lavas incorporated 50-60% of a carbonate-metasomatized mantle source while the other prehistoric lavas show 10-22% contribution of this source. This result indicates that the Nyiragongo lavas were derived from a heterogeneous, non-uniformly carbonated mantle source. The 2002 lava shows ( 210Pb/ 226Ra) equilibrium, whereas the 2003 lava lake sample shows initial ( 210Pb/ 226Ra) < 1. The latter observation suggests that Nyiragongo magmas degas as they rise to the surface over years or decades before eruption. ( 210Pb/ 226Ra) equilibrium in the 2002 lava suggests that the 2002 magma may have stagnated for more than a decade before eruption. The high CO 2 content, high emission rates, extreme fluidity, along with the inferred short residence time and our inferences of rapid magma transport and high eruptive frequency suggest that the volcanic hazards of Nyiragongo, both from lava flows and gas emissions, are higher than previously estimated.

Chakrabarti, Ramananda; Sims, Kenneth W. W.; Basu, Asish R.; Reagan, Mark; Durieux, Jacques

2009-10-01

129

FLIGHTS ACROSS RADIOACTIVE CLOUDS  

Microsoft Academic Search

Danger to personnel and equipment arising from radioactive contamination ; of aircraft after flying across radioactive clouds is discussed. Flights ; performed 20-30 minutes after an atomic bomb explosion are no longer dangerous. ; Radioactive dust penetrating into the aircraft constitutes a serious danger. ; Formation of nitrate in the aircraft decreases the radioactivity. Immediate ; decontamination of the aircraft

Chabowski

1960-01-01

130

Estimation of heat generation by radioactive decay of some phosphate rocks in Egypt.  

PubMed

Radiogenic heat production data for phosphate rocks outcropping on the three main areas Eastern Desert, Western Desert and Nile Valley are presented. They were derived from uranium, thorium and potassium concentration measurements of gamma radiation originating from the decay of (214)Bi ((238)U series), (208)Tl ((232)Th series) and the primary decay of (40)K. A low radioactive heat production rate (0.32+/-0.1 microWm(-3)) was found for Wadi Hegaza, whereas the highest value (19+/-4.1 microWm(-3)) was found for Gabel Anz, Eastern Desert of Egypt. PMID:19186064

Din, Khaled Salahel

2008-11-18

131

Levels of sup 137 Cs and natural radioactivity in Saudi Arabian soil  

SciTech Connect

After the Chernobyl accident, there was concern about contamination from the radioactive plume reaching Saudi Arabia. Cesium-137 concentration in the soil was measured to determine the degree of contamination from the accident. The concentrations of {sup 40}K, {sup 214}Bi, and {sup 228}Ac were determined as well. Bismuth-214 is a member of the {sup 238}U series, while {sup 228}Ac is from the {sup 238}Th series. Each of these isotopes emits several well-resolved photons of relatively high intensity per disintegration.

Abulfarai, W.; Abdul-Majid, S. (King Abdulaziz Univ., Jeddah (Saudi Arabia))

1991-01-01

132

Levels of sup 137 Cs and natural radioactivity in Saudi Arabian soil  

Microsoft Academic Search

After the Chernobyl accident, there was concern about contamination from the radioactive plume reaching Saudi Arabia. Cesium-137 concentration in the soil was measured to determine the degree of contamination from the accident. The concentrations of ⁴°K, ²¹⁴Bi, and ²²⁸Ac were determined as well. Bismuth-214 is a member of the ²³⁸U series, while ²²⁸Ac is from the ²³⁸Th series. Each of

W. Abulfarai; S. Abdul-Majid

1991-01-01

133

RADIO-ACTIVE TRANSDUCER  

DOEpatents

ABS>ure the change in velocity of a moving object. The transducer includes a radioactive source having a collimated beam of radioactive particles, a shield which can block the passage of the radioactive beam, and a scintillation detector to measure the number of radioactive particles in the beam which are not blocked by the shield. The shield is operatively placed across the radioactive beam so that any motion normal to the beam will cause the shield to move in the opposite direction thereby allowing more radioactive particles to reach the detector. The number of particles detected indicates the acceleration. (AEC)

Wanetick, S.

1962-03-01

134

Radioactive Waste Management.  

National Technical Information Service (NTIS)

Management of radioactive wastes is necessary to protect public health, public safety, and the environment from radioactive materials resulting from national defense programs, energy research and development, and commercial activities. Access to informati...

1990-01-01

135

Radioactivity and geophysics.  

National Technical Information Service (NTIS)

The paper recalls a few steps of the introduction of radioactivity in geophysics and astrophysics: contribution of radioelements to energy balance of the Earth, age of the Earth based on radioactive disintegration and the discovery of cosmic radiations. (...

P. Radvanyi

1992-01-01

136

Microfiltration of radioactive contaminants.  

National Technical Information Service (NTIS)

Cross-flow microfiltration processing of radioactive liquids has been in use at Chalk River Laboratories for about four years. The separation process removes suspended particles from radioactive waste solutions. The clean liquid can then be treated with c...

L. P. Buckley J. A. Slade S. Vijayan C. F. Wong

1993-01-01

137

Procedures for radioactive I-131  

SciTech Connect

Details of the radioactive I-131 administration and radiation safety considerations are presented. Topics covered include patient survey, radioactive labelling, levels in patients containing radioactivity, hospital discharge of radioactive patients, and nursing procedures.

Sharma, S.C. (Univ. of Louisville, KY (USA))

1988-12-01

138

Procedures for radioactive I-131.  

PubMed

Details of the radioactive I-131 administration and radiation safety considerations are presented. Topics covered include patient survey, radioactive labelling, levels in patients containing radioactivity, hospital discharge of radioactive patients, and nursing procedures. PMID:3252901

Sharma, S C

1988-12-01

139

U-series in zircon and 40Ar/39Ar geochronology reveal the most recent stage of a supervolcanic cycle in the Altiplano-Puna Volcanic Complex, Central Andes  

NASA Astrophysics Data System (ADS)

The ignimbrite flare up that produced the Altiplano-Puna Volcanic Complex of the Central Andes is characterized by episodic supervolcanism over a ~10 Ma time-span that climaxed about 4Ma. Since peak activity, the temporal and spatial record of volcanism suggests a waning of the system with only one other supervolcanic eruption at 2.6Ma. The most recent phase of volcanism from the APVC comprises a series of late Pleistocene domes that share a general petrochemical resemblance to the ignimbrites. New U-series data on zircons and high precision 40Ar/39Ar age determinations reveal that these effusive eruptions represent a temporally coherent magmatic episode. The five largest domes (Chao, Chillahuita, Chanka, Chascon-Runtu Jarita, and Tocopuri) have a combined volume >40 km3, and are distributed over an elliptical area of over 3000km2 centered at 22S 68W. They are crystal rich (>50%) dacites to rhyolites. New 40Ar/39Ar age determinations on biotite for the domes range range from 1086 to 19050 ka. However, 40Ar/39Ar ages from sanidine for some of the domes are more precise and span from 874 to 972 ka. We therefore interpret the eruption age of all these domes to be ~90 - 100 ka. This is consistent with SIMS U-series crystallization ages from the rims of 66 zircon crystals from four of the domes that reveal a fairly continuous spread of ages from ~90 ka to >300 ka with potentially common peaks in zircon ages at 100 ka and ~200 ka. U-Pb dating on the interiors of some of these zircon crystals indicates crystallization ages of up to 1.5 Ma. The common peaks of zircon crystallization between domes suggest that magma that fed these domes shared a larger regional source. Furthermore, the large volume of this potential source and the crystal-rich nature of the lava imply that this source was likely a large body of crystal-mush. The continuous nature of the zircon rim age population indicates that the residence time of this magma body was likely >200kyr. Potential peaks in zircon crystallization ages could result from periodic injections of andesitic magma that reinvigorated crystallization. However, the ubiquity of likely antecrystic zircon interiors suggests that the associated temperature rise was insufficient to cause complete resorbtion of the antecrysts. A shared peak of zircon crystallization just prior to eruptions, as well as co-eruption of andesitic lava connotes recharge as the eruption trigger.

Tierney, C.; de Silva, S. L.; Schmitt, A. K.; Jicha, B.; Singer, B. S.

2010-12-01

140

Radioactivity distribution in some Permian sediments from the Irat and Corumbata Formations of the Paran Basin, Southeastern Brazil.  

PubMed

In the city of Limeira, southeastern Brazil, an important exposure of Permian sediments of the Paran basin was revealed by an open pit mine that exploits limestone for production of soil correction compounds and raw materials for the ceramic industry. The radioactivity of these sediments was investigated in some detail and the results provided a general view of the vertical distributions of uranium, thorium and potassium concentrations and of the element ratios U/K, U/Th and Th/K. In general, the concentrations of the main natural radioactive elements are low, with uranium being enriched in some limestone and shale levels. In addition the results showed that the 238U series is in radioactive disequilibrium in many of the analyzed samples. Although the origin of the observed disequilibrium has not been investigated, the results suggest that it is due to weathering processes and water interaction with the rock matrix. PMID:14687638

Carlos, Dionsio Uendro; Ribeiro, Fernando Brenha; Saad, Antonio Roberto; Nicolai, Silvia Helena de Arajo

2004-01-01

141

Radioactivity and food  

SciTech Connect

Two topics relating to radioactivity and food are discussed: food irradiation for preservation purposes, and food contamination from radioactive substances. Food irradiation involves the use of electromagnetic energy (x and gamma rays) emitted by radioactive substances or produced by machine in order to destroy the insects and microorganisms present and prevent germination. The sanitary and economic advantages of treating food in this way are discussed. Numerous studies have confirmed that under strictly controlled conditions no undesirable changes take place in food that has been irradiated nor is radioactivity induced. Reference is made to the accident at the Chernobyl nuclear power station, which aroused public concern about irradiated food. The events surrounding the accident are reviewed, and its consequences with regard to contamination of different foods with radioactive substances, particularly iodine-131 and cesium-137, are described. Also discussed are the steps that have been taken by different international organizations to set limits on acceptable radioactivity in food.15 references.

Olszyna-Marzys, A.E. (Laboratorio Unificado de Control de Alimentos y Medicamentos (LUCAM) (Guatemala))

1990-03-01

142

A study of environmental radioactivity measurements for Cankiri, Turkey.  

PubMed

This study is the first to assess the level of background radiation for the Cankiri province of Turkey. Indoor air radon concentrations were determined using Columbia Resin-39 nuclear track detectors and the average (222)Rn activity was found to be 44 Bq m(-3) (equivalent to an annual effective dose of 1.1 mSv). Measurements of gamma doses in outdoor air were performed using a portable plastic scintillation detector and the average gamma absorbed dose rate was found to be 8 ?R h(-1) (corresponding to an annual effective dose of 87.7 ?Sv). Radionuclide activity concentrations in soil samples were measured through gamma-ray spectrometry and the average activities were determined as 17.7, 22.3, 357 and 4.1 Bq kg(-1) for the radionuclides (238)U, (232)Th, (40)K and (137)Cs, respectively. The average annual effective dose from the natural radioactivity sources ((238)U series, (232)Th series and (40)K) was calculated to be 44.4 ?Sv. Radioactivity levels of drinking water samples were carried out using a low-background proportional counter and the average gross alpha and beta activities were obtained as 0.25 and 0.26 Bq l(-1), respectively (equivalent to an annual effective dose of 184 ?Sv). The average radon concentrations in indoor air and the average radionuclide activities in soil were found to be lower than most Turkish cities while higher levels of outdoor gamma dose rate and water radioactivity were observed. The results of this study showed that the region's background radioactivity level differs considerably from the reported data for Turkish cities. PMID:22069234

Kapdan, Enis; Taskin, Halim; Kam, Erol; Osmanlioglu, A Erdal; Karahan, Gursel; Bozkurt, Ahmet

2011-11-07

143

Radioactive Waste Management Basis  

SciTech Connect

The purpose of this Radioactive Waste Management Basis is to describe the systematic approach for planning, executing, and evaluating the management of radioactive waste at LLNL. The implementation of this document will ensure that waste management activities at LLNL are conducted in compliance with the requirements of DOE Order 435.1, Radioactive Waste Management, and the Implementation Guide for DOE Manual 435.1-1, Radioactive Waste Management Manual. Technical justification is provided where methods for meeting the requirements of DOE Order 435.1 deviate from the DOE Manual 435.1-1 and Implementation Guide.

Perkins, B K

2009-06-03

144

Numerical dating of a Late Quaternary spit-shoreline complex at the northern end of Silver Lake playa, Mojave Desert, California: A comparison of the applicability of radiocarbon, luminescence, terrestrial cosmogenic nuclide, electron spin resonance, U-series and amino acid racemization methods  

Microsoft Academic Search

A Late Quaternary spit-shoreline complex on the northern shore of Pleistocene Lake Mojave of southeastern California, USA was studied with the goal of comparing accelerator mass spectrometry (AMS) radiocarbon, luminescence, electron spin resonance (ESR), terrestrial cosmogenic radionuclide (TCN) surface exposure, amino acid racemization (AAR) and U-series dating methods. The pattern of ages obtained by the different methods illustrates the complexity

Lewis A. Owena; Jordon Brightb; Robert C. Finkelc; Manoj K. Jaiswald; Darrell S. Kaufmanb; Shannon Mahane; Ulrich Radtkef; Joan S. Schneiderg; Warren Sharph; Ashok K. Singhvid; Claude N. Warreni

145

Radioactive waste disposal package  

DOEpatents

A radioactive waste disposal package comprising a canister for containing vitrified radioactive waste material and a sealed outer shell encapsulating the canister. A solid block of filler material is supported in said shell and convertible into a liquid state for flow into the space between the canister and outer shell and subsequently hardened to form a solid, impervious layer occupying such space.

Lampe, Robert F. (Bethel Park, PA)

1986-01-01

146

Radioactivity in Spanish spas  

Microsoft Academic Search

There are large number of spas in Spain and there is a lack of data concerning their radioactivity. The levels of radioactivity in a wide sample of Spanish spas were measured with special attention being paid to the radon and radium concentrations in the water, and to radon concentration in the indoor air of the spas. This study is primarily

J. Soto; P. L. Fernndez; L. S. Quinds; J. Gmez-Arozamena

1995-01-01

147

Radioactive Wastes. Revised.  

ERIC Educational Resources Information Center

|This publication is one of a series of information booklets for the general public published by the United States Atomic Energy Commission. This booklet deals with the handling, processing and disposal of radioactive wastes. Among the topics discussed are: The Nature of Radioactive Wastes; Waste Management; and Research and Development. There are

Fox, Charles H.

148

A Remote Radioactivity Experiment  

ERIC Educational Resources Information Center

|Imagine a high school with very few experimental resources and limited budgets that prevent the purchase of even basic laboratory equipment. For example, many high schools do not have the means of experimentally studying radioactivity because they lack Geiger counters and/or good radioactive sources. This was the case at the first high school one

Jona, Kemi; Vondracek, Mark

2013-01-01

149

ORNL radioactive waste operations  

Microsoft Academic Search

Since its beginning in 1943, ORNL has generated large amounts of solid, liquid, and gaseous radioactive waste material as a by-product of the basic research and development work carried out at the laboratory. The waste system at ORNL has been continually modified and updated to keep pace with the changing release requirements for radioactive wastes. Major upgrading projects are currently

J. D. Sease; E. M. King; J. H. Coobs; T. H. Row

1982-01-01

150

Temporary Personal Radioactivity  

ERIC Educational Resources Information Center

|As part of a bone scan procedure to look for the spread of prostate cancer, I was injected with radioactive technetium. In an effort to occupy/distract my mind, I used a Geiger counter to determine if the radioactive count obeyed the inverse-square law as a sensor was moved away from my bladder by incremental distances. (Contains 1 table and 2

Myers, Fred

2012-01-01

151

Calibration of Radioactive Sources  

NASA Astrophysics Data System (ADS)

All detector systems for the measurement of radioactivity in the different fields of applications need to be calibrated in terms of efficiency with radioactive sources of known activities and of known radionuclides. This is true for the measurement of environmental radioactivity, activities of sources for medical applications, or activities in the field of nuclear industry and nuclear research. It is the task of National Metrology Institutes (NMIs) and Calibration Laboratories to calibrate radioactive sources in terms of activity and to provide activity standards appropriate to the special needs of their customers. This chapter describes the methods to calibrate the activity of radioactive materials, the different types of calibration sources, and the wayto establish the traceability and international comparability of activity standards.

Arnold, Dirk; Janen, Herbert

152

Radioactive Decay Model  

NSDL National Science Digital Library

The EJS Radioactive Decay Model simulates the decay of a radioactive sample using discrete random events. It displays the number of radioactive nuclei as a function of time. You can change the initial number of nuclei and the decay constant as well as changing the plot to a semi-log plot. The Radioactive Decay model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ms_explicit_RadioactiveDecay.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2009-01-23

153

Incineration of Radioactive Waste.  

National Technical Information Service (NTIS)

In this study, made on contract for the Swedish Nuclear Power Inspectorate, different methods for incineration of radioactive wastes are reviewed. Operation experiences and methods under development are also discussed. The aim of incineration of radioacti...

C. Thegerstroem

1980-01-01

154

Table of Radioactive Isotopes.  

National Technical Information Service (NTIS)

A description is given for the Table of Radioactive Isotopes which will be published in 1986. The format of the table is given as to content and organization. 22 refs., 2 figs. (ERA citation 11:010444)

R. B. Firestone E. Browne

1985-01-01

155

Environmental Radioactivity Intercomparison, 1992.  

National Technical Information Service (NTIS)

Following on from two previous environmental radioactivity measurement intercomparison exercises, NPL conducted a third intercomparison of this sort in 1992. The results from the first two exercises were generally satisfactory, although the problem of cas...

S. M. Jerome M. J. Woods S. E. M. Lucas A. C. Hooley

1993-01-01

156

Understanding radioactive waste  

SciTech Connect

This document contains information on all aspects of radioactive wastes. Facts are presented about radioactive wastes simply, clearly and in an unbiased manner which makes the information readily accessible to the interested public. The contents are as follows: questions and concerns about wastes; atoms and chemistry; radioactivity; kinds of radiation; biological effects of radiation; radiation standards and protection; fission and fission products; the Manhattan Project; defense and development; uses of isotopes and radiation; classification of wastes; spent fuels from nuclear reactors; storage of spent fuel; reprocessing, recycling, and resources; uranium mill tailings; low-level wastes; transportation; methods of handling high-level nuclear wastes; project salt vault; multiple barrier approach; research on waste isolation; legal requiremnts; the national waste management program; societal aspects of radioactive wastes; perspectives; glossary; appendix A (scientific American articles); appendix B (reference material on wastes). (ATT)

Murray, R.L.

1981-12-01

157

Dynamic radioactive particle source  

SciTech Connect

A method and apparatus for providing a timed, synchronized dynamic alpha or beta particle source for testing the response of continuous air monitors (CAMs) for airborne alpha or beta emitters is provided. The method includes providing a radioactive source; placing the radioactive source inside the detection volume of a CAM; and introducing an alpha or beta-emitting isotope while the CAM is in a normal functioning mode.

Moore, Murray E.; Gauss, Adam Benjamin; Justus, Alan Lawrence

2012-06-26

158

Container for radioactive materials  

DOEpatents

A container for housing a plurality of canister assemblies containing radioactive material and disposed in a longitudinally spaced relation within a carrier to form a payload package concentrically mounted within the container. The payload package includes a spacer for each canister assembly, said spacer comprising a base member longitudinally spacing adjacent canister assemblies from each other and a sleeve surrounding the associated canister assembly for centering the same and conducting heat from the radioactive material in a desired flow path.

Fields, Stanley R. (Richland, WA)

1985-01-01

159

Radioactive Decay Distribution Model  

NSDL National Science Digital Library

The EJS Radioactive Decay Distribution Model simulates the decay of a radioactive sample using discrete random events. It displays the distribution of the number of events (radioactive decays) in a fixed time interval. If each event is assumed to occur independently and spontaneously with a constant probability, the resulting distribution if the Poisson distribution. You can change the initial number of nuclei, the decay constant and the time interval for the event distribution. The Radioactive Decay Distribution model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ms_explicit_RadioactiveDecayDistribution.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2009-01-23

160

Container for radioactive materials  

DOEpatents

A container is claimed for housing a plurality of canister assemblies containing radioactive material. The several canister assemblies are stacked in a longitudinally spaced relation within a carrier to form a payload concentrically mounted within the container. The payload package includes a spacer for each canister assembly, said spacer comprising a base member longitudinally spacing adjacent canister assemblies from each other and sleeve surrounding the associated canister assembly for centering the same and conducting heat from the radioactive material in a desired flow path. 7 figures.

Fields, S.R.

1984-05-30

161

Vacuuming radioactive sludge  

ScienceCinema

Vacuuming an estimated 55 cubic yards of radioactive sludge from the floor of Hanford's K East Basin was a complicated process. Workers stood on grates suspended above the 20-foot deep basin and manipulated vacuuming equipment at the end of long poles--using underwater cameras to guide their work.

162

Radioactivity of Fiestaware.  

National Technical Information Service (NTIS)

In order to investigate the question of the radioactivity of Fiestaware, I borrowed from Lee Schroeder 9 small Fiestaware plates of different colors. Eight of these plates are shown in the photograph below. The ninth was a rose colored plate that I got fr...

E. B. Norman

2002-01-01

163

Radioactivity and foods  

SciTech Connect

The purpose of this article is to describe and contrast two relationships between radiation and food--on the one hand, beneficial preservation of food by controlled exposure to ionizing radiation; and, on the other, contamination of food by accidental incorporation of radioactive nuclides within the food itself. In food irradiation, electrons or electromagnetic radiation is used to destroy microorganisms and insects or prevent seed germination. The economic advantages and health benefits of sterilizing food in this manner are clear, and numerous studies have confirmed that under strictly controlled conditions no undersirable changes or induced radioactivity is produced in the irradiated food. An altogether different situation is presented by exposure of food animals and farming areas to radioactive materials, as occurred after the major Soviet nuclear reactor accident at Chenobyl. This article furnishes the basic information needed to understand the nature of food contamination associated with that event and describes the work of international organizations seeking to establish appropriate safe limits for levels of radioactivity in foods.

Olszyna-Marzys, A.E. (Unified Lab. of Food and Drug Control, Guatemala City (Guatemala))

1991-01-01

164

TABLE OF RADIOACTIVE ELEMENTS.  

SciTech Connect

For those chemical elements which have no stable nuclides with a terrestrial isotopic composition, the data on radioactive half-lives and relative atomic masses for the nuclides of interest and importance have been evaluated and the recommended values and uncertainties are listed.

HOLDEN,N.E.

2001-06-29

165

AIR RADIOACTIVITY MONITOR  

DOEpatents

The monitor is designed to minimize undesirable background buildup. It consists of an elongated column containing peripheral electrodes in a central portion of the column, and conduits directing an axial flow of radioactively contaminated air through the center of the column and pure air through the annular portion of the column about the electrodes. (AEC)

Bradshaw, R.L.; Thomas, J.W.

1961-04-11

166

Table of radioactive isotopes  

Microsoft Academic Search

This book provides a comprehensive and critical evaluation of the nuclear and atomic properties of radioactive isotopes. Detailed radiation data for about 2000 of the 2755 known nuclides are presented in this up-to-date and concise book. The main section is organized by mass number (A), with entries for a given A derived from and referenced to the most recent corresponding

Edgardo Browne; Richard B. Firestone; V. S. Shirley

1986-01-01

167

Radioactive Decay - An Analog.  

ERIC Educational Resources Information Center

|Presents an analog of radioactive decay that allows the student to grasp the concept of half life and the exponential nature of the decay process. The analog is devised to use small, colored, plastic poker chips or counters. Provides the typical data and a graph which supports the analog. (YP)|

McGeachy, Frank

1988-01-01

168

Radioactive decay data tables  

Microsoft Academic Search

The estimation of radiation dose to man from either external or internal exposure to radionuclides requires a knowledge of the energies and intensities of the atomic and nuclear radiations emitted during the radioactive decay process. The availability of evaluated decay data for the large number of radionuclides of interest is thus of fundamental importance for radiation dosimetry. This handbook contains

Kocher

1981-01-01

169

Radioactive Waste: Production, Storage, Disposal.  

National Technical Information Service (NTIS)

Radioactive wastes are the leftovers from the use of nuclear materials for the production of electricity, diagnosis and treatment of disease, and other purposes. The materials are either naturally occurring or man-made. Certain kinds of radioactive materi...

2002-01-01

170

Radioactive I-131 from Fallout  

MedlinePLUS

... Trials Cancer Statistics Research & Funding News About NCI Radioactive I-131 from Fallout Page Options Print This ... Americans exposed to I-131 (a form of radioactive iodine) through fallout from above-ground nuclear testing ...

171

Environmental Radioactivity, Temperature, and Precipitation.  

ERIC Educational Resources Information Center

Reports that environmental radioactivity levels vary with temperature and precipitation and these effects are due to radon. Discusses the measurement of this environmental radioactivity and the theory behind it. (JRH)

Riland, Carson A.

1996-01-01

172

Environmental Radioactivity, Temperature, and Precipitation.  

ERIC Educational Resources Information Center

|Reports that environmental radioactivity levels vary with temperature and precipitation and these effects are due to radon. Discusses the measurement of this environmental radioactivity and the theory behind it. (JRH)|

Riland, Carson A.

1996-01-01

173

Radioactive waste shredding: Preliminary evaluation.  

National Technical Information Service (NTIS)

The critical constraints for sizing solid radioactive and mixed wastes for subsequent thermal treatment were identified via a literature review and a survey of shredding equipment vendors. The types and amounts of DOE radioactive wastes that will require ...

N. R. Soelberg G. A. Reimann

1994-01-01

174

Process for treating radioactive waste  

Microsoft Academic Search

A process for treating radioactive sludge waste wasted in a nuclear power plant comprises the steps of pulverizing the radioactive sludge waste into dry powder which is combustible, burning the powder into ashes, and pelletizing the ashes. The radioactive sludge waste including granular ion-exchange resins, powder resins, filter sludge, etc. is reduced in volume by subjecting to combustion.

M. Hirano; S. Horiuchi

1985-01-01

175

Fusion reactor radioactive waste management  

Microsoft Academic Search

Quantities and compositions of non-tritium radioactive waste are estimated for some current conceptual fusion reactor designs, and disposal of large amounts of radioactive waste appears necessary. Although the initial radioactivity of fusion reactor and fission reactor wastes are comparable, the radionuclides in fusion reactor wastes are less hazardous and have shorter half-lives. Areas requiring further research are discussed.

J. D. Kaser; A. K. Postma; D. J. Bradley

1976-01-01

176

QUANTITATIVE MEASUREMENTS OF CLOUD ELEMENT RADIOACTIVITY  

Microsoft Academic Search

A method is outlined for calculating the concentration of radioactive ; substances in cloud elements from their alpha tracks in a nuclear emulsion. ; Computational formulas were derived for the concentration of the radioactive ; elemerte of three radioactive families. The concentrations of radioactive ; substances and the radioactivity in cloud elements were calculated. The ; radioactivity of cloud elements

Potsius; V. Yu

1963-01-01

177

Radioactive Isotopes of Lanthanum  

Microsoft Academic Search

The radioactive isotope La140, known to be produced by deuteron and slow neutron bombardments of lanthanum is found to have a half-life of 40.0+\\/-0.3 hours. This isotope has now been produced by the reaction Ce140(n,p)La140. Evidence for the occurrence of a d, y reaction has been obtained through the formation of La140 by the reaction Ba138(d,y)La140. The 40-hour isotope decays

Katherine E. Weimer; M. L. Pool; J. D. Kurbatov

1943-01-01

178

Table of radioactive elements  

SciTech Connect

As has been the custom in the past, the Commission publishes a table of relative atomic masses and halflives of selected radionuclides. The information contained in this table will enable the user to calculate the atomic weight for radioactive materials with a variety of isotopic compositions. The atomic masses have been taken from the 1984 Atomic Mass Table. Some of the halflives have already been documented.

Holden, N.E.

1985-01-01

179

PROCESSING OF RADIOACTIVE WASTE  

DOEpatents

A process for treating radioactive waste solutions prior to disposal is described. A water-soluble phosphate, borate, and/or silicate is added. The solution is sprayed with steam into a space heated from 325 to 400 deg C whereby a powder is formed. The powder is melted and calcined at from 800 to 1000 deg C. Water vapor and gaseous products are separated from the glass formed. (AEC)

Johnson, B.M. Jr.; Barton, G.B.

1961-11-14

180

RADIOACTIVE MATERIALS SENSORS  

SciTech Connect

Providing technical means to detect, prevent, and reverse the threat of potential illicit use of radiological or nuclear materials is among the greatest challenges facing contemporary science and technology. In this short article, we provide brief description and overview of the state-of-the-art in sensor development for the detection of radioactive materials, as well as an identification of the technical needs and challenges faced by the detection community. We begin with a discussion of gamma-ray and neutron detectors and spectrometers, followed by a description of imaging sensors, active interrogation, and materials development, before closing with a brief discussion of the unique challenges posed in fielding sensor systems.

Mayo, Robert M.; Stephens, Daniel L.

2009-09-15

181

Radioactive waste material disposal  

DOEpatents

The invention is a process for direct conversion of solid radioactive waste, particularly spent nuclear fuel and its cladding, if any, into a solidified waste glass. A sacrificial metal oxide, dissolved in a glass bath, is used to oxidize elemental metal and any carbon values present in the waste as they are fed to the bath. Two different modes of operation are possible, depending on the sacrificial metal oxide employed. In the first mode, a regenerable sacrificial oxide, e.g., PbO, is employed, while the second mode features use of disposable oxides such as ferric oxide.

Forsberg, Charles W. (155 Newport Dr., Oak Ridge, TN 37830); Beahm, Edward C. (106 Cooper Cir., Oak Ridge, TN 37830); Parker, George W. (321 Dominion Cir., Knoxville, TN 37922)

1995-01-01

182

Radioactive waste processing apparatus  

DOEpatents

Apparatus for use in processing radioactive waste materials for shipment and storage in solid form in a container is disclosed. The container includes a top, and an opening in the top which is smaller than the outer circumference of the container. The apparatus includes an enclosure into which the container is placed, solution feed apparatus for adding a solution containing radioactive waste materials into the container through the container opening, and at least one rotatable blade for blending the solution with a fixing agent such as cement or the like as the solution is added into the container. The blade is constructed so that it can pass through the opening in the top of the container. The rotational axis of the blade is displaced from the center of the blade so that after the blade passes through the opening, the blade and container can be adjusted so that one edge of the blade is adjacent the cylindrical wall of the container, to insure thorough mixing. When the blade is inside the container, a substantially sealed chamber is formed to contain vapors created by the chemical action of the waste solution and fixant, and vapors emanating through the opening in the container.

Nelson, Robert E. (Lombard, IL); Ziegler, Anton A. (Darien, IL); Serino, David F. (Maplewood, MN); Basnar, Paul J. (Western Springs, IL)

1987-01-01

183

Radioactivity in Urals  

NASA Astrophysics Data System (ADS)

Interest in the problems due to the radioactive contamination of the environment has been frequently stimulated by rumors of an occurrence of severe contamination of lakes and rivers in areas of the Ural Mountains. Occasional evidence appearing in publications and provided by Soviet emigrants has been pieced together and seems to suggest that there is an ideal opportunity for groundwater geochemists and others to evaluate such major radioactivity in the environment. The reasons that such a study probably will not take place is that the contamination may have been caused for the most part by a nuclear explosion in a Soviet weapons plant.F. Parker, an environmental scientist at Vanderbilt University, in a study for the Department of Energy, deduced that a large explosion occurred in 1958 at a nuclear fuels reprocessing plant at Kyshtym in the Ural Mountains, according to a recent report (Science, July 8, 1983). The report refers to the original interpretations of Z. Medvedev, a Soviet geneticist, who concluded that nuclear fallout has contaminated a very extensive area around Kyshtym.

184

Radioactive Waste Incineration: Status Report  

Microsoft Academic Search

Incineration is generally accepted as a method of reducing the volume of radioactive waste. In some cases, the resulting ash may have high concentrations of materials such as Plutonium or Uranium that are valuable materials for recycling. Incineration can also be effective in treating waste that contains hazardous chemicals as well as radioactive contamination. Despite these advantages, the number of

A. R. Diederich; M. J. Akins

2008-01-01

185

RADIOACTIVITY OF THE HUMAN BODY  

Microsoft Academic Search

Although it is not yet possible to assess the biological role of natural ; raddoactivity in human life, it is important to determine its magnitude before ; any substantial change takes place in its level due to acquired radioactivity. ; Various techniques for measuring natural body radioactivity are reviewed. The ; low-level activities encountered require that the radiation detector should

F. W. Spiers; P. R. J. Burch

1957-01-01

186

Stefan Meyer: Pioneer of Radioactivity  

NASA Astrophysics Data System (ADS)

Stefan Meyer was one of the pioneers in radioactivity research and director of the Vienna Radium Institute, the first institution in the world devoted exclusively to radioactivity. I give here a biographical sketch of Meyer and of some of his colleagues and an overview of the research activities at the Radium Institute.

Reiter, Wolfgang L.

2001-03-01

187

TREATMENT OF RADIOACTIVE WASTE GASES  

Microsoft Academic Search

The disposal of radioactive waste gases from the plant-scale processes ; at the Hanford Atomic Products Operation presents a problem that is of ; coniderable importance in plant operation. Equipment developed for the efficicnt ; removal of the two prinipal contaminants: 1) gaseous radioactive iodine; and 2) ; an aerosol composed of other fission products is described. The program has

A. G. Blasewitz; W. C. Schmidt

1958-01-01

188

Heavy fragment radioactivities  

SciTech Connect

This recently discovered mode of radioactive decay, like alpha decay and spontaneous fission, is believed to involve tunneling through the deformation-energy barrier between a very heavy nucleus and two separated fragments the sum of whose masses is less than the mass of the parent nucleus. In all known cases the heavier of the two fragments is close to doubly magic /sup 208/Pb, and the lighter fragment has even Z. Four isotopes of Ra are known to emit /sup 14/C nuclei; several isotopes of U as well as /sup 230/Th and /sup 231/Pa emit Ne nuclei; and /sup 234/U exhibits four hadronic decay modes: alpha decay, spontaneous fission, Ne decay and Mg decay.

Price, P.B.

1987-12-10

189

Radioactive waste processing apparatus  

DOEpatents

Apparatus for use in processing radioactive waste materials for shipment and storage in solid form in a container is disclosed. The container includes a top, and an opening in the top which is smaller than the outer circumference of the container. The apparatus includes an enclosure into which the container is placed, solution feed apparatus for adding a solution containing radioactive waste materials into the container through the container opening, and at least one rotatable blade for blending the solution with a fixing agent such as cement or the like as the solution is added into the container. The blade is constructed so that it can pass through the opening in the top of the container. The rotational axis of the blade is displaced from the center of the blade so that after the blade passes through the opening, the blade and container can be adjusted so that one edge of the blade is adjacent the cylindrical wall of the container, to insure thorough mixing. When the blade is inside the container, a substantially sealed chamber is formed to contain vapors created by the chemical action of the waste solution and fixant, and vapors emanating through the opening in the container. The chamber may be formed by placing a removable extension over the top of the container. The extension communicates with the apparatus so that such vapors are contained within the container, extension and solution feed apparatus. A portion of the chamber includes coolant which condenses the vapors. The resulting condensate is returned to the container by the force of gravity.

Nelson, R.E.; Ziegler, A.A.; Serino, D.F.; Basnar, P.J.

1985-08-30

190

46 CFR 147.100 - Radioactive materials.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Radioactive materials. 147.100 Section 147.100...Requirements for Particular Materials § 147.100 Radioactive materials. (a) Radioactive materials must not be brought on...

2012-10-01

191

49 CFR 172.556 - RADIOACTIVE placard.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false RADIOACTIVE placard. 172.556 Section 172...SECURITY PLANS Placarding § 172.556 RADIOACTIVE placard. (a) Except for size and color, the RADIOACTIVE placard must be as follows:...

2011-10-01

192

46 CFR 147.100 - Radioactive materials.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Radioactive materials. 147.100 Section 147.100...Requirements for Particular Materials § 147.100 Radioactive materials. (a) Radioactive materials must not be brought on...

2011-10-01

193

49 CFR 172.556 - RADIOACTIVE placard.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false RADIOACTIVE placard. 172.556 Section 172...SECURITY PLANS Placarding § 172.556 RADIOACTIVE placard. (a) Except for size and color, the RADIOACTIVE placard must be as follows:...

2012-10-01

194

10 CFR 39.47 - Radioactive markers.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Radioactive markers. 39.47 Section 39.47...WELL LOGGING Equipment § 39.47 Radioactive markers. The licensee may use radioactive markers in wells only if the individual...

2013-01-01

195

Chemical and isotopic constraints on the generation and transport of magma beneath the East Pacific Rise  

Microsoft Academic Search

Interpretation of U-series disequilibria in midocean ridge basalts is highly dependent on the bulk partition coefficients for U and Th and therefore the mineralogy of the mantle source. Distinguishing between the effect of melting processes and variable source compositions on measured disequilibria (238U-230Th-226Ra and 235U-231Pa) requires measurement of the radiogenic isotopes Hf, Nd, Sr, and Pb. Here, we report measurements

K. W. W. SIMS; S. J. GOLDSTEIN; J. B LICHERT-TOFT; M. R. PERFIT; P. Kelemen; D. J. FORNARI; P. Michael; M. T Murrell; S. R Hart; D. J DePaolo; G. Layne; L. Ball; M. Jull; J. Bender

2002-01-01

196

Final disposal of radioactive waste  

NASA Astrophysics Data System (ADS)

In this paper the origin and properties of radioactive waste as well as its classification scheme (low-level waste - LLW, intermediate-level waste - ILW, high-level waste - HLW) are presented. The various options for conditioning of waste of different levels of radioactivity are reviewed. The composition, radiotoxicity and reprocessing of spent fuel and their effect on storage and options for final disposal are discussed. The current situation of final waste disposal in a selected number of countries is mentioned. Also, the role of the International Atomic Energy Agency with regard to the development and monitoring of international safety standards for both spent nuclear fuel and radioactive waste management is described.

Freiesleben, H.

2013-06-01

197

How Does Radioactive Decay Work?  

NSDL National Science Digital Library

This teacher's guide with exercises is intended to help teach the topics of radioactive decay and its use to determine age. It identifies four main concepts that students are likely to struggle with: spontaneity (randomness) of radioactive decay; the importance of isotopes; the concept of half-life; and how to choose which system of isotopes to use to determine age. The guide presents suggestions on how to make these ideas more understandable, and provides three exercises that can be used to demonstrate radioactive decay. Links to additional materials and information are embedded in the resource.

Wenner, Jennifer M.

2010-11-17

198

Apparatus for infectious radioactive waste  

SciTech Connect

This patent describes an apparatus for housing solid, radioactively and biologically contaminated waste during steam autoclave treatment thereof. It comprises a container means for housing solid infectious radioactive biological wastes, suitable for use during an autoclaving procedure, having at least one opening therein; a filter means for entrapping radioactive compounds contained in gases exiting the container means during autoclave treatment, the filter means being securely disposed within an opening of the container means such that any gas exiting the container means during autoclave treatment passes through the filter means; and indicator means for establishing that the biologically contaminated waste has been inactivated by exposure to a predetermined autoclaving temperature.

Stinson, M.C.; Galanek, M.S.

1991-11-19

199

RADIOACTIVE CONCENTRATOR AND RADIATION SOURCE  

DOEpatents

A method is presented for forming a permeable ion exchange bed using Montmorillonite clay to absorb and adsorb radioactive ions from liquid radioactive wastes. A paste is formed of clay, water, and a material that fomns with clay a stable aggregate in the presence of water. The mixture is extruded into a volume of water to form clay rods. The rods may then be used to remove radioactive cations from liquid waste solutions. After use, the rods are removed from the solution and heated to a temperature of 750 to 1000 deg C to fix the ratioactive cations in the clay.

Hatch, L.P.

1959-12-29

200

Radioactive Waste Management  

NASA Astrophysics Data System (ADS)

Issues related to the management of radioactive wastes are presented with specific emphasis on high-level wastes generated as a result of energy and materials production using nuclear reactors. The final disposition of these high-level wastes depends on which nuclear fuel cycle is pursued, and range from once-through burning of fuel in a light water reactor followed by direct disposal in a geologic repository to more advanced fuel cycles (AFCs) where the spent fuel is reprocessed or partitioned to recover the fissile material (primarily 235U and 239Pu) as well as the minor actinides (MAs) (neptunium, americium, and curium) and some long-lived fission products (e.g., 99Tc and 129I). In the latter fuel cycle, the fissile materials are recycled through a reactor to produce more energy, the short-lived fission products are vitrified and disposed of in a geologic repository, and the minor actinides and long-lived fission products are converted to less radiotoxic or otherwise stable nuclides by a process called transmutation. The advantages and disadvantages of the various fuel cycle options and the challenges to the management of nuclear wastes they represent are discussed.

Baisden, P. A.; Atkins-Duffin, C. E.

201

Airborne Penetration of Radioactive Clouds.  

National Technical Information Service (NTIS)

This report evaluates the threat to aircrew members when their aircraft approaches and subsequently penetrates a descending radioactive cloud generated by a nuclear weapon surface burst. The re-development of Hickman's program consists of a remodeling of ...

T. R. Kling

1983-01-01

202

Radioactive Waste Processing and Disposal.  

National Technical Information Service (NTIS)

The Technical Information Center, beginning in 1958, periodically issues bibliographies on radioactive wastes. This compilation contains 4144 citations of foreign and domestic research reports, journal articles, patents, conference proceedings, and books....

1980-01-01

203

Radioactive Waste Processing and Disposal.  

National Technical Information Service (NTIS)

The Technical Information Center, beginning in 1958, periodically issues bibliographies on radioactive wastes. This compilation contains 3597 citations of foreign and domestic research reports, journal articles, patents, conference proceedings, and books....

1980-01-01

204

Radioactive Organic Bromo-Compounds  

Microsoft Academic Search

CONSIDERABLE attention has recently been focused on the use of artificially radioactive substances in biological work. The radioactive isotope 82Br has been chosen by us because it has a conveniently long half-life (34 hours), it is chemically reactive, it gives off gamma-rays which aid in its detection, and finally, it can be prepared from 81Br either by the action of

E. Friedmann; A. K. Solomon; N. T. Werthessen

1939-01-01

205

Radioactive waste disposal and geology  

Microsoft Academic Search

This book is an excellent, well-presented treatise on the nature and types of radioactive wastes, disposal alternatives and strategies, radionuclide release and disposal models, geologic repositories, natural analogues, subsea-bed options, and low-level wastes. The authors provide national and international perspectives on radioactive waste disposal problems. They carefully dissected each issue, treating its pros and cons equally. Moreover, they is careful

K. B. Krauskopf

1988-01-01

206

U-Series dating of Dead Sea Basin carbonates  

Microsoft Academic Search

An attempt is made to apply the Th 230 \\/ U 234 dating method to inorganic marls which are presumably associated with pluviation in the Jordan River-Dead Sea graben. The resulting ages seem to be acceptable with respect to their Th 230 -U 234 relationships, their internal stratigraphic consistency and their agreement with available C-14 ages. However, other evidence on

Aaron Kaufman

1971-01-01

207

U series and amino acid dates from Jersey  

Microsoft Academic Search

Understanding of the raised beach and other interglacial sequences in the southern part of the British Isles has been improved through use of the amino acid racemization technique. This method has permitted correlation of these isolated and fragmentary marine deposits1,2 which, except for the Portland site, are located around the shores of the Bristol Channel1. By applying this technique with

D. H. Keen; R. S. Harmon; J. T. Andrews

1981-01-01

208

Storage depot for radioactive material  

DOEpatents

Vertical drilling of cylindrical holes in the soil, and the lining of such holes, provides storage vaults called caissons. A guarded depot is provided with a plurality of such caissons covered by shielded closures preventing radiation from penetrating through any linear gap to the atmosphere. The heat generated by the radioactive material is dissipated through the vertical liner of the well into the adjacent soil and thus to the ground surface so that most of the heat from the radioactive material is dissipated into the atmosphere in a manner involving no significant amount of biologically harmful radiation. The passive cooling of the radioactive material without reliance upon pumps, personnel, or other factor which might fail, constitutes one of the most advantageous features of this system. Moreover this system is resistant to damage from tornadoes or earthquakes. Hermetically sealed containers of radioactive material may be positioned in the caissons. Loading vehicles can travel throughout the depot to permit great flexibility of loading and unloading radioactive materials. Radioactive material can be shifted to a more closely spaced caisson after ageing sufficiently to generate much less heat. The quantity of material stored in a caisson is restricted by the average capacity for heat dissipation of the soil adjacent such caisson.

Szulinski, Milton J. (Richland, WA)

1983-01-01

209

Radioactive boulders in Hawks Crag Breccia  

Microsoft Academic Search

Several radioactive hornfels and granite boulders have been found scattered through the Hawks Crag Breccia in the Big River and Lower Buller Gorge areas., Uraninite has been identified in the radioactive biotite hornfels from the Lower Buller Gorge. An unidentified, iron-rich, uranium-bearing mineral occurs in the radioactive biotite hornfels from the Big River area. The radioactivity in the biotite granite

A. Wodzicki

1959-01-01

210

Endangered and Extinct Radioactivity  

NASA Astrophysics Data System (ADS)

Gamma ray spectroscopy holds great promise for probing nucleosynthesis in individual nucleosynthesis events, via observations of short-lived radioactivity, and for measuring global galactic nucleosynthesis today with detections of longer-lived radioactivity. Many of the astrophysical issues addressed by these observations are precisely those that must be understood in order to interpret observations of extinct radioactivity in meteorites. It was somewhat surprising that the former case was realized first for a Type II supernova, when both 56Co [1] and 57Co [2] were detected in SN 1987A. These provide unprecedented constraints on models of Type II explosions. Live 26Al in the galaxy might come from Type II supernovae and their progenitors, and if this is eventually shown to be the case, can constrain massive star evolution, supernova nucleosynthesis, the galactic Type II supernova rate, and even models of the chemical evolution of the galaxy [3]. Titanium-44 is produced primarily in the alpha-rich freezeout from nuclear statistical equilibrium, possibly in Type Ia [4] and almost certainly in Type II supernovae [5]. The galactic recurrence time of these events is comparable to the 44Ti lifetime, so we expect to be able to see at most a few otherwise unseen 44Ti remnants at any given time. No such remnants have been detected yet [6]. Very simple arguments lead to the expectation that about 4 x 10^-4 M(sub)solar mass of 44Ca are produced per century. The product of the supernova frequency times the 44Ti yield per event must equal this number. Even assuming that only the latest event would be seen, rates in excess of 2 century^-1 are ruled out at >=99% confidence by the gamma ray limits. Only rates less than 0.3 century^-1 are acceptable at >5% confidence, and this means that the yield per event must be >10^-3 M(sub)solar mass to produce the requisite 44Ca. Rates this low are incompatible with current estimates for Type II supernovae and yields this high are also very difficult to understand for any standard supernova models. This situation is puzzling. Searches for 60Fe gamma rays have also produced only upper limits, corresponding to a limit of 1.7 M(sub)solar mass in the present interstellar medium. Given the usual assumption of steady state between production and decay, the current rate of synthesis of 60Fe is less than 1.7 M(sub)solar mass/2.2 m.y. It has been suggested that a neutron-rich NSE occurs in small regions in both Type Ia supernovae supernovae and in core-collapse supernovae [7]. Either type might eject significant quantities of 60Fe. If we know the frequency of a particular type of 60Fe-producing event in the past few million years, then we can limit the mean 60Fe mass ejected per event. We have M(sub)ej (60Fe) <= 8 x 10^-5/R(SN) M(sub)solar mass where R(sub)SN is the frequency of the supernovae that eject 60Fe, in number per century. Type Ia supernovae might eject roughly 10^-4 M(sub)solar mass of 60Fe [8], which is very close to this limit. References: [1] Leising M. D. and Share G. H. (1990) Astrophys. J., 357, 638. [2] Kurfess J. D. et al. (1992) Astrophys. J. Lett., 399, L137. [3] Clayton D. D. et al. (1993) Astrophys. J. Lett., submitted. [4] Nomoto K. et al. (1984) Astrophys. J., 286, 644. [5] Woosley S. E. (1988) Proc. Astron. Soc. Aust., 7, 355. [6] Leising M. D. and Share G. H. (1993) Astrophys. J., submitted. [7] Hartmann D. H. et al. (1985) Astrophys. J., 297, 837. [8] Woosley S. E. (1991) In Gamma-Ray Line Astrophysics (P. Durouchoux and N. Prantzos, eds.), 270-290, AIP Conf. Proc. No. 232, New York.

Leising, M. D.

1993-07-01

211

Distribution of low-level natural radioactivity in a populated marine region of the Eastern Mediterranean Sea.  

PubMed

The levels of natural radioactivity have been evaluated in the water column of an eastern Mediterranean region (Saronikos Gulf), with respect to the relevant environmental parameters. A novel methodology was used for the determination of natural radionuclides, which substitutes the time-consuming radiochemical analysis, based on an in situ sample preconcentration using ion-selective manganese fibres placed on pumping systems. With regard to the results obtained, (238)U-series radionuclides were found at the same level or lower than those observed previously in Mediterranean regions indicating the absence of technologically enhanced naturally occurring radioactive material (TENORM) activities in the area. Similar results were observed for the (232)Th-series radionuclides and (40)K in the water column in comparison with the relevant literature on the Mediterranean Sea. The calculated ratios of (238)U-(232)Th and (40)K-(232)Th verified the lack of TENORM contribution in the Saronikos Gulf. Finally, a rough estimation was attempted concerning the residence times of fresh water inputs from a treatment plant of domestic wastes (Waste Water Treatment Plant of Psitalia) showing that fresh waters need a maximum of 15.77.6 d to be mixed with the open sea water. PMID:22539533

Evangeliou, Nikolaos; Florou, Heleny; Kritidis, Panayotis

2012-04-26

212

RADIOACTIVE TRACERS IN HYDROLOGIC STUDIES  

Microsoft Academic Search

Experiments were carried out in lakes and reservoirs in Massachusetts to ; determine eddy diffusion coefficients. The average eddy diffusion coefficient ; divided by the radius of the eddy was found to be 0.09 ft\\/sec. Experiments to ; determine the average velocity of streams and the dilution in streams by use of ; radioactive tracers were then performed. The diffusion

1958-01-01

213

Radioactivity air monitoring in Mexico  

Microsoft Academic Search

The program used for monitoring air for radioactivity in Mexico is ; described. It was designed to fit the following local conditions: Geographical ; and meteorological conditions have prevented the country from receiving ; considerable contamination from nuclear debris. Almost all activities being ; detected are transported to the eanth's surface from the stratosphere, where they ; were previously injected,

M. B. Skertchly; R. M. Nulman; M. B. Vasquez; C. A. Willis

1972-01-01

214

Radioactive contamination of the atmosphere  

Microsoft Academic Search

This article is a review of foreign works on the study of radioactive contamination of the atmosphere due primarily to diffusion of fission fragments from atomic tests. Several properties of fission fragment activity, namely its decay rate and the composition of its radiation, are considered, and methods are described for monitoring the fallout from the atmosphere and calculating the resulting

L. I. Gedeonov

1957-01-01

215

Radioactive decontamination apparatus and process  

Microsoft Academic Search

Apparatus for removing radioactive contamination from metal objects is disclosed, consisting of three of three separate pieces. The first is an electro- polishing tank, pump and filter assembly, ventilation duct and filter assembly, and DC power supply. The second is a rinse tank and a pump and filter assembly therefor. The third is a divot crane. The electro-polishing tank assembly

1983-01-01

216

Consumer Products Containing Radioactive Materials  

MedlinePLUS

... radium. The amount of radioactivity incorporated into the plants is low and does not harm the plant. Food Food contains a variety of different types ... generally fail to penetrate the dead layers of cells covering the skin and can be easily stopped ...

217

High-Level Radioactive Waste.  

ERIC Educational Resources Information Center

|Presents a method to calculate the amount of high-level radioactive waste by taking into consideration the following factors: the fission process that yields the waste, identification of the waste, the energy required to run a 1-GWe plant for one year, and the uranium mass required to produce that energy. Briefly discusses waste disposal and

Hayden, Howard C.

1995-01-01

218

Radioactivity in bottled mineral waters  

Microsoft Academic Search

Consumption of bottled mineral water is a growing practice and is sometimes a necessity rather than a choice. In this work, a study of the radioactive content of a wide selection of commercial bottled mineral waters for human intake was carried out. The origins of the analyzed waters were very different, coming from various locations in France, Portugal and Spain.

A Mart??n Snchez; M. P Rubio Montero; V Gmez Escobar; M Jurado Vargas

1999-01-01

219

Apparatus for treating radioactive concentrates  

Microsoft Academic Search

An apparatus is provided for treating various radioactive concentrates having a liquid component, such as suspensions and salt solutions, which are present separately in a processing plant from evaporation systems, resin bead ion exchange filters, and from at least one further separating stage provided with, for example, mechanical filters, sedimentation basins and\\/or powdered resin ion exchange filters. The filter concentrates

O. Meichsner; H. Queiser

1981-01-01

220

Measurement of radioactivity in soil  

Microsoft Academic Search

A series of soils originating from different rock types has been examined for their radioactive contents. The activities due to Ra 226 plus daughters, Th 232 plus daughters and K 40 were determined in 3 kg samples on a stablilized scintillation -ray spectrometer. The resulting pulse-height spectra were analysed by a least squares method using existing computer programmes. The purpose

Maria Vassilaki; L. Salmon; J. A. B. Gibson

1966-01-01

221

Natural radioactivity in Spanish soils  

Microsoft Academic Search

The program of studies and surveys of natural radiation and radioactivity in Spain organized by our research group at the end of the 1980s included a 4-y national survey to determine the concentrations of natural radionuclides in soil. Results obtained from measurements of soil samples collected nationwide at >900 sampling sites are reported and discussed in this paper. Correlations between

L. S. Quindos; P. L. Fernandez; J. Soto; C. Rodenas; J. Gomez

1994-01-01

222

Radioactivity and the Biology Teacher  

ERIC Educational Resources Information Center

|Discusses minimum necessary nuclear fundamentals of radioactive isotopes such as levels of activity, specific activity and the use of carrier materials. Corrections that need to be taken into account in using an isotope to obtain a valid result are also described and statistics for a valid result are included. (BR)|

Hornsey, D. J.

1974-01-01

223

Monitoring of Radioactivity in 1979.  

National Technical Information Service (NTIS)

Data are given on the monitoring of radioactive contamination of air and some food stuff at world locations throughout Western South America, South Pacific and Africa during 1979. Data are included on the total beta and gamma activity and radionuclide con...

1979-01-01

224

Intense beams of radioactive nuclei  

Microsoft Academic Search

Most research reactors, for example, IBR-2, IBR-30 (Dubna), and BR-10 (Obninsk), have more than ten channels. It is shown theoretically and experimentally that one of these channels can be used as a source of heavy radioactive ions. This substantially extends the range of applications of these reactors in physical investigations. A method based on the electrostatic extraction of ions is

O. E. Kolyaskin; Yu. V. Norseev; L. N. Somov

1995-01-01

225

Radioactive waste disposal in granite  

Microsoft Academic Search

The principal geotechnical problems in selecting a repository site for radioactive waste disposal in granite are to evaluate the suitability of the rock mass in terms of: (1) fracture characteristics, (2) thermomechanical effects, and (3) fracture hydrology. Underground experiments in a mine in Sweden have provided an opportunity to study these problems. The research has demonstrated the importance of hydrogeology

P. A. Witherspoon; D. J. Watkins

1982-01-01

226

Source, Transport and Dumping of Radioactive Waste.  

National Technical Information Service (NTIS)

The results of an examination into the problems of radioactive waste are presented, in particular the sources, transport and dumping and the policy considerations in favour of specific methods. The theoretical background of radioactive waste is described,...

1980-01-01

227

Nuclear-Transfer Spectroscopy Using Radioactive Targets.  

National Technical Information Service (NTIS)

The feasibiity and techniques for carrying out transfer spectroscopic experiments with radioactive targets having half lives down to a fraction of a year are reviewed. The use of such radioactive targets is illustrated by recent studies of the spectroscop...

R. A. Naumann R. Dewberry R. T. Kouzes R. Hoff H. Boerner

1981-01-01

228

Radioactive Waste Incineration: Status Report  

SciTech Connect

Incineration is generally accepted as a method of reducing the volume of radioactive waste. In some cases, the resulting ash may have high concentrations of materials such as Plutonium or Uranium that are valuable materials for recycling. Incineration can also be effective in treating waste that contains hazardous chemicals as well as radioactive contamination. Despite these advantages, the number of operating incinerators currently in the US currently appears to be small and potentially declining. This paper describes technical, regulatory, economic and political factors that affect the selection of incineration as a preferred method of treating radioactive waste. The history of incinerator use at commercial and DOE facilities is summarized, along with the factors that have affected each of the sectors, thus leading to the current set of active incinerator facilities. In summary: Incineration has had a long history of use in radioactive waste processing due to their ability to reduce the volume of the waste while destroying hazardous chemicals and biological material. However, combinations of technical, regulatory, economic and political factors have constrained the overall use of incineration. In both the Government and Private sectors, the trend is to have a limited number of larger incineration facilities that treat wastes from a multiple sites. Each of these sector is now served by only one or two incinerators. Increased use of incineration is not likely unless there is a change in the factors involved, such as a significant increase in the cost of disposal. Medical wastes with low levels of radioactive contamination are being treated effectively at small, local incineration facilities. No trend is expected in this group. (authors)

Diederich, A.R.; Akins, M.J. [WorleyParsons, Reading, PA (United States)

2008-07-01

229

Alpha radioactive background in BGO crystals  

NASA Astrophysics Data System (ADS)

We describe some cases of unusual internal radioactive background in BGO crystals. Routinely produced at the Nikolaev Institute of Inorganic Chemistry during nearly a quarter of a century, BGO crystals have low radioactive background caused by 207Bi contamination. However, some BGO crystals incidentally have higher internal radioactive background with activity up to 10 Bq/kg. This background is pure alpha radioactivity. It is caused by 210Po contamination and has technogenic origin.

Grigoriev, D. N.; Kazanin, V. F.; Kuznetcov, G. N.; Novoselov, I. I.; Schotanus, P.; Shavinski, B. M.; Shepelev, S. N.; Shlegel, V. N.; Vasiliev, Ya. V.

2010-11-01

230

49 CFR 175.705 - Radioactive contamination.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Radioactive contamination. 175.705 Section...Classification of Material § 175.705 Radioactive contamination. (a) A carrier...contact by any person with Class 7 (radioactive) materials that may have been...

2012-10-01

231

49 CFR 175.705 - Radioactive contamination.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Radioactive contamination. 175.705 Section...Classification of Material § 175.705 Radioactive contamination. (a) A carrier...contact by any person with Class 7 (radioactive) materials that may have been...

2011-10-01

232

Radioactive waste treatment technologies and environment  

Microsoft Academic Search

The radioactive waste treatment and conditioning are the most important steps in radioactive waste management. At the Slovak Electric, plc, a range of technologies are used for the processing of radioactive waste into a form suitable for disposal in near surface repository. These technologies operated by JAVYS, PLc. Nuclear and Decommissioning Company, PLc. Jaslovske Bohunice are described. Main accent is

Jan HORVATH; Dusan KRASNY

2007-01-01

233

Process for decontaminating gas containing radioactive iodine  

Microsoft Academic Search

A vent gas containing radioactive iodine and methyl iodide is effectively decontaminated by chemically adsorbing the iodine contained in the vent gas onto an activated carbon layer at first, then physically adsorbing the methyl iodide contained in the vent gas onto another activated carbon layer separately disposed from the former activated carbon layer, and retaining the radioactive iodine and radioactive

M. Hirano; M. Takeshima; T. Saito; A. Shimozato

1977-01-01

234

10 CFR Appendix E to Part 835 - Values for Establishing Sealed Radioactive Source Accountability and Radioactive Material Posting...  

Code of Federal Regulations, 2013 CFR

... false Values for Establishing Sealed Radioactive Source Accountability and Radioactive Material Posting and Labeling Requirements...Part 835Values for Establishing Sealed Radioactive Source Accountability and Radioactive...

2013-01-01

235

Radioactive waste shredding: Preliminary evaluation  

SciTech Connect

The critical constraints for sizing solid radioactive and mixed wastes for subsequent thermal treatment were identified via a literature review and a survey of shredding equipment vendors. The types and amounts of DOE radioactive wastes that will require treatment to reduce the waste volume, destroy hazardous organics, or immobilize radionuclides and/or hazardous metals were considered. The preliminary steps of waste receipt, inspection, and separation were included because many potential waste treatment technologies have limits on feedstream chemical content, physical composition, and particle size. Most treatment processes and shredding operations require at least some degree of feed material characterization. Preliminary cost estimates show that pretreatment costs per unit of waste can be high and can vary significantly, depending on the processing rate and desired output particle size.

Soelberg, N.R.; Reimann, G.A.

1994-07-01

236

Radioactive Decays in Geant4  

NASA Astrophysics Data System (ADS)

The simulation of radioactive decays is a common task in Monte-Carlo systems such as Geant4. Usually, a system either uses an approach focusing on the simulations of every individual decay or an approach which simulates a large number of decays with a focus on correct overall statistics. The radioactive decay package presented in this work permits, for the first time, the use of both methods within the same simulation framework - Geant4. The accuracy of the statistical approach in our new package, RDM-extended, and that of the existing Geant4 per-decay implementation (original RDM), which has also been refactored, are verified against the ENSDF database. The new verified package is beneficial for a wide range of experimental scenarios, as it enables researchers to choose the most appropriate approach for their Geant4-based application.

Hauf, Steffen; Kuster, Markus; Batic, Matej; Bell, Zane W.; Hoffmann, Dieter H. H.; Lang, Philipp M.; Neff, Stephan; Pia, Maria Grazia; Weidenspointner, Georg; Zoglauer, Andreas

2013-08-01

237

Stratospheric Mixing from Radioactive Fallout  

Microsoft Academic Search

The radioactive fallout during 1959 shows that the Russian October 1958 debris dominated the northern hemisphere and came down with a residence time corresponding to about 8 months. The rest of the world had a steady fallout rate of about .06 mC\\/miS\\/inch of rain throughout the year, whereas values for the northern hemisphere came down to this value in the

W. F. Libby; C. E. Palmer

1960-01-01

238

Radioactive fuel cell storage rack  

SciTech Connect

A radioactive fuel cell storage rack is comprised of structural elements including elements which are hollow and cruciform in section. Each leg of the cruciform structural element includes a neutron shield therein. The free end of the legs of the cruciform structural element converge so as to have an included angle of approximately 90/sup 0/. The rack is comprised of such cruciform elements as well as cooperating elements which are generally T and L shaped in section.

Holtz, M.; Singh, K.P.

1983-05-03

239

Radioactive Aerosols Emission in Fires  

Microsoft Academic Search

The inner walls of glove-boxes used in nuclear facilities may be contaminated by radioactive aerosols. It is therefore necessary to be able to predict the release rate of these aerosols in the case of a fire. This phenomenon has been studied in a small-scale test-chamber (volume 0.085 m), using 10 cm 10 cm Plexiglas samples, with cerium oxide (CeO2)

Yvette Fernandez; Patrick Burghoffer

1995-01-01

240

Environmental Geochemistry of Radioactive Contamination  

NASA Astrophysics Data System (ADS)

Psychometric studies of public perception of risk have shown that dangers associated with radioactive contamination are considered the most dreaded and among the least understood hazards (Slovic, 1987). Fear of the risks associated with nuclear power and associated contamination has had important effects on policy and commercial decisions in the last few decades. In the US, no new nuclear power plants were ordered between 1978 and 2002, even though it has been suggested that the use of nuclear power has led to significantly reduced CO2 emissions and may provide some relief from the potential climatic changes associated with fossil fuel use. The costs of the remediation of sites contaminated by radioactive materials and the projected costs of waste disposal of radioactive waste in the US dwarf many other environmental programs. The cost of disposal of spent nuclear fuel at the proposed repository at Yucca Mountain will likely exceed 10 billion. The estimated total life cycle cost for remediation of US Department of Energy (DOE) weapons production sites ranged from 203-247 billion dollars in constant 1999 dollars, making the cleanup the largest environmental project on the planet (US DOE, 2001). Estimates for the cleanup of the Hanford site alone exceeded $85 billion through 2046 in some of the remediation plans.Policy decisions concerning radioactive contamination should be based on an understanding of the potential migration of radionuclides through the geosphere. In many cases, this potential may have been overestimated, leading to decisions to clean up contaminated sites unnecessarily and exposing workers to unnecessary risk. It is important for both the general public and the scientific community to be familiar with information that is well established, to identify the areas of uncertainty and to understand the significance of that uncertainty to the assessment of risk.

Siegel, M. D.; Bryan, C. R.

2003-12-01

241

Chernobyl radioactivity persists in fish  

Microsoft Academic Search

After the accident at the Chernobyl nuclear reactor in 1986, the concentration of radioactive caesium (134Cs and 137Cs) in fish was expected to decline rapidly. The estimated ecological half-life (the time needed to reduce the average caesium concentration by 50%) was 0.3 to 4.6 years,. Since 1986, we have measured radiocaesium in brown trout (Salmo trutta) and Arctic charr (Salvelinus

Bror Jonsson; Torbjrn Forseth; Ola Ugedal

1999-01-01

242

Intense beams of radioactive nuclei  

SciTech Connect

Most research reactors, for example, IBR-2, IBR-30 (Dubna), and BR-10 (Obninsk), have more than ten channels. It is shown theoretically and experimentally that one of these channels can be used as a source of heavy radioactive ions. This substantially extends the range of applications of these reactors in physical investigations. A method based on the electrostatic extraction of ions is considered. This method makes it possible to obtain isotopically pure beams of radioactive nuclei with an intensity of about 10{sup 10} nuclei/s and higher by exposing gaseous and solid targets to reactor neutrons. Following neutron capture by a nucleus, the atom is ionized with a certain probability as the result of conversion of a photon produced in the reaction (n, {gamma}) on an electron or as the result of ensuing K capture or {beta} decay of the nucleus that captured the neutron. The radioactive ions produced are extracted from the volume by an electric field and are then accelerated or deposited on an appropriate electrode. It is shown experimentally that, for a proper choice of the target geometry, the collection coefficient of {sup 125}I ions for a gaseous target containing {sup 124}Xe and for a solid target (containing, for example, {sup 181}Ta) amounts to about 50%. 14 refs., 2 figs.

Kolyaskin, O.E.; Men`shikov, L.I. [Russian Research Center Kurchatov Institute, Moscow (Russian Federation); Norseev, Y.N.; Somov, L.N. [Joint Institute for Nuclear Research, Moscow (Russian Federation)

1995-06-01

243

Radioactivity  

Microsoft Academic Search

Cesium-134 and -137 in Foods, Gamma-Ray Spectrophotometric Methods. The method entitled {open_quotes}Cs-134 and Cs-137 in Foods, Gamma-Ray Spectrophotometric Method{close_quotes} has been adopted official first action, with minor revisions. Iodine 131: The method {open_quotes}Iodine-131 in Milk, Radiochemical Separation Method{close_quotes} has been accepted by the Committee on Residues and Related Topics and has been recommended to the Methods Committee for adoption first

Baratta

1997-01-01

244

Radioactivity  

SciTech Connect

Cesium-134 and -137 in Foods, Gamma-Ray Spectrophotometric Methods. The method entitled {open_quotes}Cs-134 and Cs-137 in Foods, Gamma-Ray Spectrophotometric Method{close_quotes} has been adopted official first action, with minor revisions. Iodine 131: The method {open_quotes}Iodine-131 in Milk, Radiochemical Separation Method{close_quotes} has been accepted by the Committee on Residues and Related Topics and has been recommended to the Methods Committee for adoption first action. Search is continuing for a new Associated Referee. Plutonium-239: The Associate Referee is doing a literature search for a method for the determination of plutonium in foods. When one is selected, she will prepared a protocol for a collaborative study and submit it for approval. Radium-228: Search is ongoing for a new Associate Referee. When one is appointed, a method should be selected and tested. Strontium-89 and -90: The Associate Referee is investigating methods using resin discs and/or resin columns for these radionuclides. These methods are now being used in analyses for strontium-89 and -90 in water. She will now attempt to apply it to milk. If successful, she will prepare a protocol for a collaborative study and submit it for approval. Tritium: Search is continuing for a new Associate Referee for this topic.

Baratta, E.J. [Winchester Engineering and Analytical Center, Winchester, MA (United States)

1997-01-01

245

Radioactive Waste Management BasisSept 2001  

SciTech Connect

This Radioactive Waste Management Basis (RWMB) documents radioactive waste management practices adopted at Lawrence Livermore National Laboratory (LLNL) pursuant to Department of Energy (DOE) Order 435.1, Radioactive Waste Management. The purpose of this RWMB is to describe the systematic approach for planning, executing, and evaluating the management of radioactive waste at LLNL. The implementation of this document will ensure that waste management activities at LLNL are conducted in compliance with the requirements of DOE Order 435.1, Radioactive Waste Management, and the Implementation Guide for DOE manual 435.1-1, Radioactive Waste Management Manual. Technical justification is provided where methods for meeeting the requirements of DOE Order 435.1 deviate from the DOE Manual 435.1-1 and Implementation Guide.

Goodwin, S S

2011-08-31

246

SHIPPING CONTAINER FOR RADIOACTIVE MATERIAL  

DOEpatents

A shipping container is described for transponting a large number of radioactive nuclear fuel element modules which produce a substantial amount of heat. The container comprises a primary pressure vessel and shield, and a rotatable head having an access port that can be indexed with module holders in the container. In order to remove heat generated in the fuel eleme nts, a heat exchanger is arranged within the container and in contact with a heat exchange fluid therein. The heat exchanger communicates with additional external heat exchangers, which dissipate heat to the atmosphere. (AEC)

Nachbar, H.D.; Biggs, B.B.; Tariello, P.J.; George, K.O.

1963-01-15

247

Radioactive beams with the HHIRF accelerators  

SciTech Connect

There is an increasing interest in radioactive ion beams for astrophysics and nuclear physics research and applied programs. This interest has led to an International Conference on Radioactive Nuclear Beams and a Workshop on the Science of Intense Radioactive Ion Beams. In addition, a steering committee has been formed to consider the development of a very large and intense RIB facility in North America to produce both proton- and neutron-rich beams. This report discusses development of these beams.

Olsen, D.K.; Alton, G.D.; Baktash, C.; Dowling, D.T.; Garrett, J.D.; Haynes, D.L.; Jones, C.M.; Juras, R.C., Lane, S.N.; Lee, I.Y.; Meigs, M.J.; Mills, G.D.; Mosko, S.W.; Tatum, B.A. Toth, K.S. (Oak Ridge National Lab., TN (USA)); Carter, H.K. (UNISOR, Oak Ridge, TN (USA))

1991-01-01

248

Radioactive Drug Research Committee (RDRC) Program  

Center for Drug Evaluation (CDER)

... qualified study investigators. properly licensed medical facility to possess and handle radioactive materials. ... Developing Medical Imaging Drug and ... More results from www.fda.gov/drugs/scienceresearch/researchareas

249

Spontaneously generated radioactive nanoparticles in the environment  

NASA Astrophysics Data System (ADS)

For almost 100 years, and perhaps longer, observers have detected spontaneous dispersal of radioactivity from macroscopic quantities of radioactive materials with the first published observations reported in 1910. In the 1960"s and later, radioactivity was observed to migrate through HEPA filters de-spite their well-established filtration characteristics. In measurements of ground water, radioactivity has been found to disperse from its original location of deposition in soil, despite the size, insolubility, and resistance to chemical reactions of the radioactive particles originally deposited. Similarly, measurements of the uptake of these materials in lung tissue and studies of their solubility in simulated biological fluids showed the solubility to be related to the radioactivity of the materials. In numerous practical examples, the migration and deposition of radioactivity affects work and operational practices. Despite this long and varied history indicating the importance of self-dispersal of radioactive materials, no measurements had ever been reported of the materials which were actually dispersed until recently and the results are quite surprising, suggesting a well-defined process creating discrete nanoparticle fractions. This paper will review the history of the observations of spontaneous dispersal of radioactivity and close with a description of the first measure-ments of the dispersed nanoparticles and suggestions of the physical processes involved in their formation.

Marlow, William H.; Cheng, Yung-Sung

2003-04-01

250

Radioactive Waste: Resources for Environmental Literacy  

NSDL National Science Digital Library

Since World War II, hundreds of thousands of tons of radioactive materials have been produced in the United States. How we will dispose of nuclear waste is a controversial issue with a large technical component. This book provides a useful resource for enhancing student understanding of the physics of radioactivity as well as the storage and disposal of radioactive waste. It encourages students to discuss these complex environmental issues using arguments based on the science behind issues related to radioactivity, technology, risk assessment, and tradeoffs.

Council, Environmental L.; National Science Teachers Association (NSTA)

2007-05-16

251

Student Understanding of Ionizing Radiation and Radioactivity  

NSDL National Science Digital Library

This article describes how researchers identified specific difficulties students had with ionizing radiation and radioactivity using interviews. They also explore students' pre-instruction thoughts on these topics.

Prather, Edward E.; Harrington, Randal R.

2006-06-19

252

Non-radioactive stand-in for radioactive contamination. I. Non-radioactive tests. [High-pressure, hot water decontamination  

SciTech Connect

Candidate non-radioactive materials for use as a stand-in for radioactive contamination during application of a high-pressure, hot water decontamination were identified and evaluated. A stand-in for radioactive contamination is needed to evaluate the decontaminability of replacement canyon cranes at the manufacturers location where actual radioactive contamination cannot be used. This evaluation was conducted using high-pressure, hot-water at 420 psi, 190/sup 0/F, and 20 gal/min through a 1/8-in.-diam nozzle, the decontamination technique preferred by SRP Separations Department for this application. A non-radioactive stand-in for radioactive contamination was desired that would be removed by direct blast stream contact but would remain intact on surfaces where direct contact does not occur. This memorandum describes identification of candidate non-radioactive stand-in materials and evaluation of these materials in screening tests and tests with high-pressure, hot-water blasting. The following non-radioactive materials were tested: carpenter's line chalk; typing correction fluid; dye penetrant developer; latex paint with attapulyite added; unaltered latex paint; gold enamel; layout fluid; and black enamel. Results show that blue layout fluid and gold enamel have similar adherence that is within the range expected for actual radioactive contamination. White latex paint has less adherence than expected for actual radioactive contamination. The film was removed at a rate of <1 sec/in./sup 2/. Black enamel has more adherence than expected from actual radioactive contamination. In these tests ASTM No. 2B surfaces were harder to clean than either ASTM No. 1 or electropolished surfaces which had similar cleaning properties. A 90/sup 0/ blast angle was more effective than a 45/sup 0/ blast angle. In these tests there was no discernible effect of blast distance between 1 and 3 ft.

Rohe, M.J.; Rankin, W.N.; Postles, R.L.

1985-10-08

253

SEPARATION OF RADIOACTIVE COLUMBIUM TRACER  

DOEpatents

A process is presented for the recovery of radioactive columbium from solutions containing such columbium together with radioactive tellurium. The columbium and tellurium values are separated from such solutions by means of an inorganic oxide carrier precipitate, such as MnO/sub 2/. This oxide carrier precipitate and its associated columbium and telluriuan values are then dissolved in an aqueous acidic solution and nonradioactive tellurium, in an ionic form, is then introduced into such solution, for example in the form of H/sub 2/TeO/sub 3/. The tellurium present in the solution is then reduced to the elemental state and precipitates, and is then separated from the supernataat solution. A basic acetate precipitate is formed in the supernatant and carries the remaining columblum values therefrom. After separation, this basic ferric acetate precipitate is dissolved, and the ferric ions are removed by means of an organic solvent extraction process utilizing ether. The remaining solution contains carrier-free columbium as its only metal ion.

Glendenin, L.E.; Gest, H.

1958-08-26

254

Radioactive Waste Disposal Implications of Extending Part IIA to cover Radioactively Contaminated Land  

Microsoft Academic Search

A short study has been carried out of the potential radioactive waste disposal issues associated with the proposed extension of Part IIA to address radioactively contaminated land, where there is no other suitable existing legislation. It was found that there is likely to be an availability problem with respect to disposal at landfills of the radioactive wastes arising from remediation.

DJ Nancarrow

255

Local area networks in radioactivity measurements  

Microsoft Academic Search

We describe the operation of a Local Area Network at Nuclear Chemistry Laboratory involved in surveillance of environmental radioactivity. Detailed consideration is given separately to computer and network hardware, radiation instrument interfacing, software, as well as operations. The application of a Local Area Network offers considerable improvements in the laboratory preformance, quality assurance of radioactivity analyses, and data reporting.

T. M. Semkow; C. D. Schwenker; M. E. Kitto; J. C. Daly

1994-01-01

256

RECENT RESULTS FROM ALPINE AIR RADIOACTIVITY MEASUREMENTS  

Microsoft Academic Search

By means of various diagrams, the transient pattern of the natural and ; artificial radioactivity and of air impurities in 1959 at a valley and a ; neighboring mountain station was represented and described. It was shown that ; the air layer near the ground added more long-lived radioactive substances by ; repeated eddying up from the ground than from

1960-01-01

257

RADIOACTIVE CONTROL ON ATMOSPHERIC ELECTRICAL BASIS  

Microsoft Academic Search

Theoretical investigations were made of how far survey measurements of ; radioactivity in the air may be carried out by methods of atmospheric electricity. ; For this, the influence of a radioactive cloud on the elements of atmospheric ; electricity in the cloud and in its surrounding was estimated. The derived ; formulas were applied on some examples. These show

Oster

1963-01-01

258

Overview of Radioactive Waste Disposal at Sea  

Microsoft Academic Search

For hundreds of years, the seas have been used as a place to dispose of wastes from human activities. Although no high level radioactive waste has been disposed of into the sea, variable amounts of packaged low level radioactive wastes have been dumped at 47 sites in the northern part of the Atlantic and Pacific Oceans. in 1946 the first

Dominique Calmet

1992-01-01

259

Acid digestion of combustible radioactive wastes  

Microsoft Academic Search

The following conclusions resulted from operation of Radioactive Acid Digestion Test Unit (RADTU) for processing transuranic waste: (1) the acid digestion process can be safely and efficiently operated for radioactive waste treatment.; (2) in transuranic waste treatment, there was no detectable radionuclide carryover into the exhaust off-gas. The plutonium decontamination factor (DF) between the digester and the second off-gas tower

C. R. Allen; R. E. Lerch; M. D. Crippen; R. G. Cowan

1982-01-01

260

Potential impacts of pending residual radioactivity rules.  

National Technical Information Service (NTIS)

The purpose of this paper is to present an overview of pending rules governing residual radioactive release criteria and radioactive waste management, and the potential impact of these rules on the Fernald Scrap Metal program. More than 300,000 cubic mete...

D. D. Burns

1995-01-01

261

Radioactivity in Trinitite six decades later  

Microsoft Academic Search

The first nuclear explosion test, named the Trinity test, was conducted on July 16, 1945 near Alamogordo, New Mexico. In the tremendous heat of the explosion, the radioactive debris fused with the local soil into a glassy material named Trinitite. Selected Trinitite samples from ground zero (GZ) of the test site were investigated in detail for radioactivity. The techniques used

Pravin P. Parekh; Thomas M. Semkow; Miguel A. Torres; Douglas K. Haines; Joseph M. Cooper; Peter M. Rosenberg; Michael E. Kitto

2006-01-01

262

Passive radar detection of radioactive pollution  

Microsoft Academic Search

The new method of passive radar detection of radioactive pollution based on electromagnetic radiation registration on wavelength of 2 1 cm is offered. This radiation is spontaneous and it appears in result of atmospheric components dissociation at its interaction with radioactive elements. Experimental measurement results and their theoretical processing for detection of potentially dangerous objects on the territory of Siberian

V. P. Yakubov; V. B. Antipov; D. Y. Losev; I. A. Yuriev

1999-01-01

263

AIRBORNE RADIOACTIVITY AFTER A REACTOR ACCIDENT  

Microsoft Academic Search

For operation of nuclear reactors in densely populated areas elaborate ; precautions are necessary. In planning safety measures attention should be given ; not only to normal operating conditions but also to the procedures to he adopted ; for an accidental release of radioactive substances. When a radioactive aerosol ; is created as a resuli of a reactor accident, it

Blok

1959-01-01

264

The changing face of radioactivity in steel  

Microsoft Academic Search

The question of radioactivity in iron and steel is a matter of definition and limits of detectability. A broad statement could be made that all steel that started with blast furnace iron is radioactive. This statement is not due to the practice of using wear-indication sources in the refractory of blast furnaces. Rather, it is because of the nature of

LaMastra

1995-01-01

265

Soil washing and radioactive contamination  

SciTech Connect

Soil washing, a technique combining both physical and chemical processes to produce significant volume reduction of contaminated soils, is widely regarded as a panacea for the huge inventory of contaminated soils in the DOE Complex. While the technology has been demonstrated for organics and to some extent for metals, review of the publications available on the practical applications to radioactive sites, indicates that most volume reduction is a product of unique circumstances such as screening or floating out non-soil materials containing most of the contaminants, or leaching contaminants (uranium or TRU) that exist as anionic complexes (Grant, 1991) which are not held by the soil cation-exchange-capacity. In either case, the potential for success of the technology is extremely site and contaminant specific. The Environmental Protection Agency's (EPA) guidance on soil washing treatability studies suggests a 50% reduction of contamination in particles over 2mm as a reasonable cutoff for choosing soil washing for further development (EPA, 1991).

Gombert, D.; Bosley, J.B.

1992-03-20

266

Environmental geochemistry of radioactive contamination.  

SciTech Connect

This report attempts to describe the geochemical foundations of the behavior of radionuclides in the environment. The information is obtained and applied in three interacting spheres of inquiry and analysis: (1) experimental studies and theoretical calculations, (2) field studies of contaminated and natural analog sites and (3) model predictions of radionuclide behavior in remediation and waste disposal. Analyses of the risks from radioactive contamination require estimation of the rates of release and dispersion of the radionuclides through potential exposure pathways. These processes are controlled by solubility, speciation, sorption, and colloidal transport, which are strong functions of the compositions of the groundwater and geomedia as well as the atomic structure of the radionuclides. The chemistry of the fission products is relatively simple compared to the actinides. Because of their relatively short half-lives, fission products account for a large fraction of the radioactivity in nuclear waste for the first several hundred years but do not represent a long-term hazard in the environment. The chemistry of the longer-lived actinides is complex; however, some trends in their behavior can be described. Actinide elements of a given oxidation state have either similar or systematically varying chemical properties due to similarities in ionic size, coordination number, valence, and electron structure. In dilute aqueous systems at neutral to basic pH, the dominant actinide species are hydroxy- and carbonato-complexes, and the solubility-limiting solid phases are commonly oxides, hydroxides or carbonates. In general, actinide sorption will decrease in the presence of ligands that complex with the radionuclide; sorption of the (IV) species of actinides (Np, Pu, U) is generally greater than of the (V) species. The geochemistry of key radionuclides in three different environments is described in this report. These include: (1) low ionic strength reducing waters from crystalline rocks at nuclear waste research sites in Sweden; (2) oxic water from the J-13 well at Yucca Mountain, Nevada, the site of a proposed repository for high level nuclear waste (HLW) in tuffaceous rocks; and (3) reference brines associated with the Waste Isolation Pilot Plant (WIPP). The transport behaviors of radionuclides associated with the Chernobyl reactor accident and the Oklo Natural Reactor are described. These examples span wide temporal and spatial scales and include the rapid geochemical and physical processes important to nuclear reactor accidents or industrial discharges as well as the slower processes important to the geologic disposal of nuclear waste. Application of geochemical information to remediating or assessing the risk posed by radioactive contamination is the final subject of this report. After radioactive source terms have been removed, large volumes of soil and water with low but potentially hazardous levels of contamination may remain. For poorly-sorbing radionuclides, capture of contaminated water and removal of radionuclides may be possible using permeable reactive barriers and bioremediation. For strongly sorbing radionuclides, contaminant plumes will move very slowly. Through a combination of monitoring, regulations and modeling, it may be possible to have confidence that they will not be a hazard to current or future populations. Abstraction of the hydrogeochemical properties of real systems into simple models is required for probabilistic risk assessment. Simplifications in solubility and sorption models used in performance assessment calculations for the WIPP and the proposed HLW repository at Yucca Mountain are briefly described.

Bryan, Charles R.; Siegel, Malcolm Dean

2003-09-01

267

Radioactive Target Production at RIA  

NASA Astrophysics Data System (ADS)

We explore the production of samples of long-lived isotopes (t1/2 >1 h) at an advanced radioactive ion beam facility, RIA. Production yields at RIA are compared to capabilities at stable beam facilities and at high-flux reactors. Long-lived neutron-rich nuclei can generally be produced more efficiently in a nuclear reactor if appropriate target samples are available. As a result, only two s process branch point nuclei, 135Cs and 163Ho, seem suitable for sample production at RIA. In contrast, samples of many long-lived proton-rich nuclei are produced effectively at RIA, including isotopes important for the p process. Sample production at RIA is more favored when the lifetime of the isotope is shorter.

Blackmon, J. C.

2002-12-01

268

Microbiological treatment of radioactive wastes  

SciTech Connect

The ability of microorganisms which are ubiquitous throughout nature to bring about information of organic and inorganic compounds in radioactive wastes has been recognized. Unlike organic contaminants, metals cannot be destroyed, but must be either removed or converted to a stable form. Radionuclides and toxic metals in wastes may be present initially in soluble form or, after disposal may be converted to a soluble form by chemical or microbiological processes. The key microbiological reactions include (i) oxidation/reduction; (ii) change in pH and Eh which affects the valence state and solubility of the metal; (iii) production of sequestering agents; and (iv) bioaccumulation. All of these processes can mobilize or stabilize metals in the environment.

Francis, A.J.

1992-12-31

269

Radioactive effluents in Savannah River  

SciTech Connect

During 1990, low-level radiometric studies of the Savannah River continued to distinguish between effluent contributions from Plant Vogtle and the Savannah River Site. Measurements of these radioactive effluents are of mutual interest to both institutions, as they can address disturbing trends before they become health and legal concerns. The Environmental Technology Section (ETS) has conducted radiometric studies of Plant Vogtle since late 1986, prior to its startup. The plant has two 1100 MWe pressurized water reactors developed by Westinghouse. Unit 1 started commercial operations in June 1987, and Unit 2 began in May 1989. During powered operations, ETS has routinely detected neutron-activated isotopes in controlled releases but all activities have been several orders of magnitude below the DOE guide values. In 1990, processing improvements for Vogtle effluents have yielded even lower activities in the river. The Vogtle release data and the ETS measurements have tracked well over the past four years.

Winn, W.G.

1991-11-27

270

Diverter assembly for radioactive material  

DOEpatents

A diverter assembly for diverting a pneumatically conveyed holder for a radioactive material between a central conveying tube and one of a plurality of radially offset conveying tubes includes an airtight container. A diverter tube having an offset end is suitably mounted in the container for rotation. A rotary seal seals one end of the diverter tube during and after rotation of the diverter tube while a spring biased seal seals the other end of the diverter tube which mvoes between various offset conveying tubes. An indexing device rotatably indexes the diverter tube and this indexing device is driven by a suitable drive. The indexing mechanism is preferably a geneva-type mechanism to provide a locking of the diverter tube in place.

Andrews, Katherine M. (Pittsburgh, PA); Starenchak, Robert W. (Youngwood, PA)

1989-01-01

271

[Examination of radioactive contamination in foods].  

PubMed

Following the Fukushima nuclear plant accident in Mar. 2011, the examination of radioactive contamination in foods is being carried out in Nagoya. During the period between 30 Mar. 2011 and 31 Oct. 2012, a total of 300 food samples were collected and the concentrations of radioactive nuclides were determined by means of ?-ray spectrometry using a high-purity germanium semiconductor detector. The results of analysis indicate that the concentrations of radioactive iodine (I) and cesium (Cs) were below the regulatory limits. Radioactive I ((131)I) was detected in 7 samples which belonged to the categories of green and yellow vegetables and other vegetables. Radioactive Cs ((134)Cs and (137)Cs) was detected in 60 samples which belonged to the categories of rice and its processed products, potatoes and its processed products, nuts and seeds, green and yellow vegetables, other vegetables, fruits, mushrooms, fishes and shellfishes, processed sea foods, meat, milk and dairy products and other beverages. PMID:23676695

Miyazaki, Hitoshi; Tsuchiyama, Tomoyuki; Terada, Hisaya

2013-01-01

272

The safe disposal of radioactive wastes  

PubMed Central

A comprehensive review is given of the principles and problems involved in the safe disposal of radioactive wastes. The first part is devoted to a study of the basic facts of radioactivity and of nuclear fission, the characteristics of radioisotopes, the effects of ionizing radiations, and the maximum permissible levels of radioactivity for workers and for the general public. In the second part, the author describes the different types of radioactive wastereactor wastes and wastes arising from the use of radioisotopes in hospitals and in industryand discusses the application of the maximum permissible levels of radioactivity to their disposal and treatment, illustrating his discussion with an account of the methods practised at the principal atomic energy establishments.

Kenny, A. W.

1956-01-01

273

Production of high intensity radioactive beams  

SciTech Connect

The production of radioactive nuclear beams world-wide is reviewed. The projectile fragmentation and the ISOL approaches are discussed in detail, and the luminosity parameter is used throughout to compare different production methods. In the ISOL approach a thin and a thick target option are distinguished. The role of storage rings in radioactive beam research is evaluated. It is concluded that radioactive beams produced by the projectile fragmentation and the ISOL methods have complementary characteristics and can serve to answer different scientific questions. The decision which kind of facility to build has to depend on the significance and breadth of these questions. Finally a facility for producing a high intensity radioactive beams near the Coulomb barrier is proposed, with an expected luminosity of {approximately}10{sup 39} cm{sup {minus}2} s{sup {minus}1}, which would yield radioactive beams in excess of 10{sup 11} s{sup {minus}1}. 9 refs., 3 figs., 7 tabs.

Nitschke, J.M.

1990-04-01

274

Apparatus and method for radioactive waste screening  

SciTech Connect

An apparatus and method relating to screening radioactive waste are disclosed for ensuring that at least one calculated parameter for the measurement data of a sample falls within a range between an upper limit and a lower limit prior to the sample being packaged for disposal. The apparatus includes a radiation detector configured for detecting radioactivity and radionuclide content of the of the sample of radioactive waste and generating measurement data in response thereto, and a collimator including at least one aperture to direct a field of view of the radiation detector. The method includes measuring a radioactive content of a sample, and calculating one or more parameters from the radioactive content of the sample.

Akers, Douglas W.; Roybal, Lyle G.; Salomon, Hopi; Williams, Charles Leroy

2012-09-04

275

Radioactive Contamination Control Work Practices  

SciTech Connect

At Hanford, loose radioactive material can be found in plant systems, rooms, ventilation ducts, fuel pools, and outside radiological work facilities. Work practices used to accomplish radiological work in nuclear facilities often concern keeping radioactive contamination from spreading. This is not an easy task as the contamination activity levels can be very high and the material can be very unstable. Most of the time, the contamination is not visible, so we have to rely on surveys taken by Radiological Controls personnel to tell workers where the contamination is located and the activity levels present. The work practices used by workers are critical in controlling contamination spread, but it is impossible to document all of the work practices a worker should use. Many times, something will happen during the job that could result in a contamination spread. We rely on the workers knowledge and experience to realize when a potential spread of contamination is occurring, and take the actions necessary to prevent it from happening. It is important that a worker understand the concepts of contamination control in order to make the right decisions when work is accomplished. In facilities that work with ''fissile'' materials there is increased concern that nothing be done that increases the chance that a ''criticality accident'' might occur during work. Criticality safety personnel need to be consulted and approve contamination control practices that could increase the potential for a criticality accident. This Workshop includes a discussion of fundamental contamination control practices and new techniques used for radiological work. This is intended to be very informative and include hands-on exercises to provide the attendees with an appreciation of the methods being used to confine contamination spread.

WAGGONER, L.O.

2002-10-01

276

10 CFR 835.1202 - Accountable sealed radioactive sources.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 false Accountable sealed radioactive sources. 835.1202 Section 835...OCCUPATIONAL RADIATION PROTECTION Sealed Radioactive Source Control § 835.1202 Accountable sealed radioactive sources. (a) Each...

2009-01-01

277

46 CFR 109.559 - Explosives and radioactive materials.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Explosives and radioactive materials. 109.559 Section 109...Miscellaneous § 109.559 Explosives and radioactive materials. Except as authorized...charge, no person may use explosives or radioactive materials and equipment on a...

2012-10-01

278

49 CFR 172.310 - Class 7 (radioactive) materials.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Class 7 (radioactive) materials. 172.310 Section... Marking § 172.310 Class 7 (radioactive) materials. In addition to any...subpart, each package containing Class 7 (radioactive) materials must be marked as...

2012-10-01

279

10 CFR 835.1202 - Accountable sealed radioactive sources.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Accountable sealed radioactive sources. 835.1202 Section 835...OCCUPATIONAL RADIATION PROTECTION Sealed Radioactive Source Control § 835.1202 Accountable sealed radioactive sources. (a) Each...

2010-01-01

280

49 CFR 172.310 - Class 7 (radioactive) materials.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Class 7 (radioactive) materials. 172.310 Section... Marking § 172.310 Class 7 (radioactive) materials. In addition to any...subpart, each package containing Class 7 (radioactive) materials must be marked as...

2011-10-01

281

48 CFR 52.223-7 - Notice of radioactive materials.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Notice of radioactive materials. 52.223-7 Section...and Clauses 52.223-7 Notice of radioactive materials. As prescribed in 23...insert the following clause: Notice of Radioactive Materials (JAN 1997)...

2012-10-01

282

10 CFR 76.83 - Transfer of radioactive material.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Transfer of radioactive material. 76.83 Section 76... Safety § 76.83 Transfer of radioactive material. (a) The Corporation may not transfer radioactive material except as authorized...

2013-01-01

283

41 CFR 50-204.28 - Storage of radioactive materials.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Storage of radioactive materials. 50-204.28 Section 50-204...Radiation Standards § 50-204.28 Storage of radioactive materials. Radioactive materials stored in a nonradiation area...

2013-07-01

284

10 CFR 76.81 - Authorized use of radioactive material.  

Code of Federal Regulations, 2010 CFR

...Authorized use of radioactive material. 76.81 Section 76... CERTIFICATION OF GASEOUS DIFFUSION PLANTS Safety § 76.81 Authorized use of radioactive material. Unless otherwise authorized...possession and use of radioactive material to the locations...

2009-01-01

285

10 CFR 76.81 - Authorized use of radioactive material.  

Code of Federal Regulations, 2010 CFR

...Authorized use of radioactive material. 76.81 Section 76... CERTIFICATION OF GASEOUS DIFFUSION PLANTS Safety § 76.81 Authorized use of radioactive material. Unless otherwise authorized...possession and use of radioactive material to the locations...

2010-01-01

286

Report of radioactivity survey research in fiscal year 1988.  

National Technical Information Service (NTIS)

The National Institute of Radiological Sciences has been surveyed, as part of the radioactivity research project by the Science and Technology Agency, radioactivity levels in the environment and safety analysis for radioactive fallouts associated with nuc...

1989-01-01

287

40 CFR 141.25 - Analytical methods for radioactivity.  

Code of Federal Regulations, 2010 CFR

...141.25 - Analytical methods for radioactivity.] 40 PROTECTION OF ENVIRONMENT...Sec. 141.25 Analytical methods for radioactivity. (a) Analysis for the following...determine compliance with Sec. 141.66 (radioactivity) in accordance with...

2009-07-01

288

40 CFR 141.25 - Analytical methods for radioactivity.  

Code of Federal Regulations, 2010 CFR

...141.25 - Analytical methods for radioactivity.] 40 PROTECTION OF ENVIRONMENT...Sec. 141.25 Analytical methods for radioactivity. (a) Analysis for the following...determine compliance with Sec. 141.66 (radioactivity) in accordance with the methods...

2009-07-01

289

Influence of Radioactivity on Surface Interaction Forces  

SciTech Connect

Although some differences have been observed, the transport behavior of radioactive aerosol particles has often been assumed to be analogous to the behavior of nonradioactive aerosols in dispersion models. However, radioactive particles can become electrostatically charged as a result of the decay process. Theories have been proposed to describe this self-charging phenomenon, which may have a significant effect on how these particles interact with one another and with charged surfaces in the environment. In this study, atomic force microscopy (AFM) was employed to quantify surface forces between a particle and a planar surface and to compare measurements with and without the involvement of radioactivity. The main objective of this work is to assess directly the effects of radioactivity on the surface interactions of radioactive aerosols via the measurement of the adhesion force. The adhesion force between a silicon nitride AFM tip and an activated gold substrate was measured so that any possible effects due to radioactivity could be observed. The adhesion force between the tip and the gold surface increased significantly when the gold substrate (25 mm{sup 2} surface area) was activated to a level of approximately 0.6 mCi. The results of this investigation will prompt further work into the effects of radioactivity in particle-surface interactions.

Walker, Mark E [ORNL; McFarlane, Joanna [ORNL; Glasgow, David C [ORNL; Chung, Eunhyea [Georgia Institute of Technology; Taboada Serrano, Patricia L [ORNL; Yiacoumi, Sotira [Georgia Institute of Technology; Tsouris, Costas [ORNL

2010-01-01

290

Antiprotonic Radioactive Atom for Nuclear Structure Studies  

SciTech Connect

A future experiment to synthesize antiprotonic radioactive nuclear ions is proposed for nuclear structure studies. Antiprotonic radioactive nuclear atom can be synthesized in a nested Penning trap where a cloud of antiprotons is prestored and slow radioactive nuclear ions are bunch-injected into the trap. By observing of the ratio of {pi}+ and {pi}- produced in the annihilation process, we can deduce the different abundance of protons and neutrons at the surface of the nuclei. The proposed method would provide a unique probe for investigating the nuclear structure of unstable nuclei.

Wada, M. [Atomic Physics Laboratory, RIKEN 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Yamazaki, Y. [Atomic Physics Laboratory, RIKEN 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Institute of Physics, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1, Komaba, Meguro, Tokyo 153-8902 (Japan)

2005-10-19

291

Procedures for interstitial radioactive gold grains  

SciTech Connect

Detailed implantation procedures and safety guidelines for use of interstitial radioactive gold grains are presented. These guidelines have been found to be of practical value for personnel involved with the implant to ensure compliance with regulations but are not necessarily the only procedures which could be utilized. Topics covered include: Description of Grains and Implantation, Management and Planning of Au-198, Source Logging, Source Transportation, Source Accounting During and After Implant, Room Monitoring, Recording, Dosimetry Films, Nursing Procedures, Levels in Patients Containing Radioactivity, and Patient Discharge of Radioactive Patients.

Sharma, S.C. (Univ. of Louisville, KY (USA))

1989-01-01

292

Thermodynamic stability of radioactivity standard solutions.  

PubMed

Optimal thermodynamic stability conditions must prevail when radioactivity standard solutions are prepared. These conditions are studied, they relate to: * The nature of the radioactive ion, which makes it possible to establish the pH of the solubilization medium at a given concentration, * The carrier concentration, which is determined by considering the radionuclide production method and the prior concentration in the original solution from the supplier, * The most stable oxidation state of the radioactive ion and of the carrier ion, which must be considered at the pH established by the solubilization medium. A procedure for all the glassware used in preparation has been implemented. PMID:16679023

Iroulart, Marie Gabrielle

2006-05-06

293

Radioactive anomaly discrimination from spectral ratios  

DOEpatents

A method for discriminating a radioactive anomaly from naturally occurring radioactive materials includes detecting a first number of gamma photons having energies in a first range of energy values within a predetermined period of time and detecting a second number of gamma photons having energies in a second range of energy values within the predetermined period of time. The method further includes determining, in a controller, a ratio of the first number of gamma photons having energies in the first range and the second number of gamma photons having energies in the second range, and determining that a radioactive anomaly is present when the ratio exceeds a threshold value.

Maniscalco, James; Sjoden, Glenn; Chapman, Mac Clements

2013-08-20

294

Radioactive Beams and Exploding Stars at ORNL  

SciTech Connect

Beams of radioactive nuclei from the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL) are being used to make direct and indirect measurements of reactions important in novae, X-ray bursts, supernovae, and our Sun. Experimental results are used in nuclear data evaluations and element synthesis calculations to determine their astrophysical impact. Recent accomplishments include: the first neutron transfer reaction [(d, p)] measurements on nuclei in the r-process path in supernovae; precision measurements with radioactive 18F beams for novae; and a direct 7Be(p,{gamma})8B measurement relevant for the solar neutrino flux determination.

Smith, Michael S. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6354 (United States)

2006-07-12

295

Procedures for interstitial radioactive gold grains.  

PubMed

Detailed implantation procedures and safety guidelines for use of interstitial radioactive gold grains are presented. These guidelines have been found to be of practical value for personnel involved with the implant to ensure compliance with regulations but are not necessarily the only procedures which could be utilized. Topics covered include: Description of Grains and Implantation, Management and Planning of Au-198, Source Logging, Source Transportation, Source Accounting During and After Implant, Room Monitoring, Recording, Dosimetry Films, Nursing Procedures, Levels in Patients Containing Radioactivity, and Patient Discharge of Radioactive Patients. PMID:2742746

Sharma, S C

1989-01-01

296

Evaluation of Terrorist Interest in Radioactive Wastes  

SciTech Connect

Since September 11, 2001, intelligence gathered from Al Qaeda training camps in Afghanistan, and the ensuing terrorist activities, indicates nuclear material security concerns are valid. This paper reviews available information on sealed radioactive sources thought to be of interest to terrorists, and then examines typical wastes generated during environmental management activities to compare their comparative 'attractiveness' for terrorist diversion. Sealed radioactive sources have been evaluated in numerous studies to assess their security and attractiveness for use as a terrorist weapon. The studies conclude that tens of thousands of curies in sealed radioactive sources are available for potential use in a terrorist attack. This risk is mitigated by international efforts to find lost and abandoned sources and bring them under adequate security. However, radioactive waste has not received the same level of scrutiny to ensure security. This paper summarizes the activity and nature of radioactive sources potentially available to international terrorists. The paper then estimates radiation doses from use of radioactive sources as well as typical environmental restoration or decontamination and decommissioning wastes in a radioactive dispersal device (RDD) attack. These calculated doses indicate that radioactive wastes are, as expected, much less of a health risk than radioactive sources. The difference in radiation doses from wastes used in an RDD are four to nine orders of magnitude less than from sealed sources. We then review the International Atomic Energy Agency (IAEA) definition of 'dangerous source' in an adjusted comparison to common radioactive waste shipments generated in environmental management activities. The highest waste dispersion was found to meet only category 1-3.2 of the five step IAEA scale. A category '3' source by the IAEA standard 'is extremely unlikely, to cause injury to a person in the immediate vicinity'. The obvious conclusion of the analysis is that environmental management generated radioactive wastes have substantially less impact than radioactive sources if dispersed by terrorist-induced explosion or fire. From a health standpoint, the impact is very small. However, there is no basis to conclude that wastes are totally unattractive for use in a disruptive or economic damage event. Waste managers should be cognizant of this potential and take measures to ensure security of stored waste and waste shipments. (authors)

McFee, J.N.; Langsted, J.M.; Young, M.E. [Shaw Environmental and Infrastructure, Inc., 9201 East Dry Creek Rd. Centennial, CO 80112 (United States); Day, J.E. [Shaw Environmental and Infrastructure, Inc., 1725 Duke St, Suite 400, Alexandria, VA 22314 (United States)

2006-07-01

297

Science with radioactive beams: the alchemist's dream  

NASA Astrophysics Data System (ADS)

Nuclear science is being transformed by a new capacity to create beams of radioactive nuclei. Until now all of our knowledge of nuclear physics and the applications which flow from it has been derived from studies of radioactive decay and nuclear reactions induced by beams of the 283 stable or long-lived nuclear species we can find on Earth. Here we describe first how beams of radioactive nuclei can be created. The present status of nuclear physics is then reviewed before potential applications to nuclear physics, nuclear astrophysics, materials science, bio-medical, and environmental studies are described.

Gelletly, W.

2001-05-01

298

Radioactive Beams and Exploding Stars at ORNL  

NASA Astrophysics Data System (ADS)

Beams of radioactive nuclei from the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL) are being used to make direct and indirect measurements of reactions important in novae, X-ray bursts, supernovae, and our Sun. Experimental results are used in nuclear data evaluations and element synthesis calculations to determine their astrophysical impact. Recent accomplishments include: the first neutron transfer reaction [(d, p)] measurements on nuclei in the r-process path in supernovae; precision measurements with radioactive 18F beams for novae; and a direct 7Be(p,?)8B measurement relevant for the solar neutrino flux determination.

Smith, Michael S.

2006-07-01

299

Radioactivities related to coal mining.  

PubMed

Natural radioactivity concentrations due to the coal mining in Gabal El-Maghara, North Sinai, Egypt, were determined using gamma-ray spectroscopy. Coal, water and soil samples were investigated in this study. The (226)Ra, (232)Th and (40)K activity concentrations in coal before extraction were 18.5 +/- 0.5, 29.5 +/- 1.2 and 149.0 +/- 8.4 Bq kg(-1), respectively. These concentrations were reduced to 18-22% after extraction due to the clay removal of the coal ore. The activity contents of the water and soil samples collected from the surrounding area did not show any evidence of enhancement due to the mining activities. Absorbed dose rate and effective dose equivalent in the mine environment were 29.4 nGy h(-1) and 128.0 microSv a(-1), respectively. The measured activity concentrations in the mine environment and the surrounding areas (5 km away from the mine) are similar to that found in other regions in North and South Sinai. Based on the measurements of gamma-ray emitting radionuclides, the mine activity does not lead to any enhancement in the local area nor represents any human risk. PMID:16049576

Seddeek, Mostafa K; Sharshar, Taher; Ragab, Hossam S; Badran, Hussein M

2005-06-30

300

Soil washing and radioactive contamination  

SciTech Connect

Soil washing, a technique combining both physical and chemical processes to produce significant volume reduction of contaminated soils, is widely regarded as a panacea for the huge inventory of contaminated soils in the DOE Complex. While the technology has been demonstrated for organics and to some extent for metals, review of the publications available on the practical applications to radioactive sites, indicates that most volume reduction is a product of unique circumstances such as screening or floating out non-soil materials containing most of the contaminants, or leaching contaminants (uranium or TRU) that exist as anionic complexes (Grant, 1991) which are not held by the soil cation-exchange-capacity. In either case, the potential for success of the technology is extremely site and contaminant specific. The Environmental Protection Agency`s (EPA) guidance on soil washing treatability studies suggests a 50% reduction of contamination in particles over 2mm as a reasonable cutoff for choosing soil washing for further development (EPA, 1991).

Gombert, D.; Bosley, J.B.

1992-03-20

301

Field tests using radioactive matter.  

PubMed

During recent years, the assessment of possible radiological consequences of a terrorist attack associated with a release of radioactive substances (RaS) has been in the focus of interest of emergency preparedness and radiation protection specialists, as well as experts dealing with the dispersion of harmful substances in the atmosphere. Suitable tools for these analyses are applications of mathematical and physical models and simulation of this attack under 'realistic' conditions. The work presented here summarises the results of four tests, in which a RaS (a Tc-99 m solution) was dispersed over a free area with the use of an industrial explosive. Detection methods and techniques employed in these tests are described and values characterising the RaS dispersion--dose rates, surface activities in horizontal and vertical directions, volume activities, their space and time distributions and mass concentrations of aerosols produced after the explosion are presented and compared. These data will be applied to a comparison of outcomes of models used for the assessment of radiation accidents as well as in future field tests carried out under conditions of more complex geometry (indoor environment, terrain obstacles, etc.). PMID:20089512

Prouza, Z; Beckova, V; Cespirova, I; Helebrant, J; Hulka, J; Kuca, P; Michalek, V; Rulik, P; Skrkal, J; Hovorka, J

2010-01-19

302

Low-Level Radioactive Biomedical Wastes.  

National Technical Information Service (NTIS)

A summary of the management and hazards of low-level radioactive biomedical wastes is presented. The volume, disposal methods, current problems, regulatory agencies, and possible solutions to disposal problems are discussed. The benefits derived from usin...

G. W. Casarett

1978-01-01

303

Legal Approach to Radioactive Waste Management.  

National Technical Information Service (NTIS)

The authors of this paper review the major legal problems raised by radioactive waste management. They stress the complexity of such problems by posing three main queries: surveillance or no surveillance; liability or no liability and finally internationa...

B. Derche P. Rocamora A. Salelles

1983-01-01

304

Determination of a Radioactive Waste Classification System.  

National Technical Information Service (NTIS)

Several classification systems for radioactive wastes are reviewed and a system is developed that provides guidance on disposition of the waste. The system has three classes: high-level waste (HLW), which requires complete isolation from the biosphere for...

J. J. Cohen W. C. King

1978-01-01

305

Radioactive Waste Streams: Waste Classification for Disposal.  

National Technical Information Service (NTIS)

Radioactive waste is a byproduct of nuclear weapons production, commercial nuclear power generation, and the naval reactor program. Waste byproducts also result from radioisotopes used for scientific, medical, and industrial purposes. The legislative defi...

A. Andrews

2006-01-01

306

Issues of natural radioactivity in phosphates  

SciTech Connect

The fertilization of phosphorus (P) fertilizers is essential in agricultural production, but phosphates contain in dependence on their origin different amounts of trace elements. The problem of cadmium (Cd) loads and other heavy metals is well known. However, only a limited number of investigations examined the contamination of phosphates with the two heaviest metals, uranium (U) and thorium (Th), which are radioactive. Also potassium (K) is lightly radioactive. Measurements are done n the radioactivity content of phosphates, P fertilizers and soils. The radiation doses to workers and public as well as possible contamination of soils from phosphate rock or fertilizer caused by these elements or their daughter products is of interest with regard to radiation protection. The use of P fertilizers is necessary for a sustainable agriculture, but it involves radioactive contamination of soils. The consequences of the use of P fertilizers is discussed, also with regard to existing and proposed legislation. 11 refs., 2 figs., 7 tabs.

Schnug, E.; Haneklaus, S. [Institute of Plant Nutrition and Soil Science, Braunschweig (Germany); Schnier, C. [GKSS-Research Centre, Geesthacht (Germany); Scholten, L.C. [KEMA, Arnhem (Netherlands)

1996-12-31

307

M&M Model for Radioactive Decay  

NSDL National Science Digital Library

A tasty in-class demonstration of radioactive decay using two colors of M&M's. Illustrates the quantitative concepts of probability and exponential decay. This activity is appropriate for small classes (<40 students).

Wenner, Jennifer

308

Radioactive Dating: A Method for Geochronology.  

ERIC Educational Resources Information Center

|Gives historical background on the discovery of natural radiation and discusses various techniques for using knowledge of radiochemistry in geochronological studies. Indicates that of these radioactive techniques, Potassium-40/Argon-40 dating is used most often. (JN)|

Rowe, M. W.

1985-01-01

309

Domestic Smoke Detectors Using Radioactive Material.  

National Technical Information Service (NTIS)

Increasing numbers of technical and consumer products incorporating radioactive material are becoming available to the Australian public. One consumer device of this type coming into common use is the domestic smoke detector that uses Americium 241 in det...

1979-01-01

310

Studies of induced radioactivity at the AGS  

SciTech Connect

With the goals of higher proton intensities, along with the many modes the AGS now runs and those being commissioned to run, we have begun detailed studies of the beam induced radioactivity in the AGS.

Brown, K.A.; Tanaka, M.

1987-01-01

311

Radioactive Dating: A Method for Geochronology.  

ERIC Educational Resources Information Center

Gives historical background on the discovery of natural radiation and discusses various techniques for using knowledge of radiochemistry in geochronological studies. Indicates that of these radioactive techniques, Potassium-40/Argon-40 dating is used most often. (JN)

Rowe, M. W.

1985-01-01

312

Using Popcorn to Simulate Radioactive Decay  

NSDL National Science Digital Library

Popping popcorn in your class is an excellent way to illustrate both the spontaneity and irreversible change associated with radioactive decay. It helps students to understand the unpredictability of decay.

Wenner, Jennifer

313

Radioactive isotopes in solid-state physics  

Microsoft Academic Search

Radioactive atoms have been used in solid-state physics and in material science for many decades. Besides their classical application as tracer for diffusion studies, nuclear techniques such as M\\\\\\

Manfred Deicher

2002-01-01

314

Demonstration of radioactive decay using pennies  

NSDL National Science Digital Library

A demonstration (with full class participation) to illustrate radioactive decay by flipping coins. Shows students visually the concepts of exponential decay, half-life and randomness. Works best in large classes -- the more people, the better.

Wenner, Jennifer

315

RADIOACTIVITY STANDARDS DISTRIBUTION PROGRAM FY 1977  

EPA Science Inventory

A program is described for the distribution of calibrated radioactive samples, as one function of EPA's quality assurance program for environmental radiation measurements. Included is a discussion of the objectives of the distribution program and a description of the preparation,...

316

RADIOACTIVITY STANDARDS DISTRIBUTION PROGRAM, 1978-1979  

EPA Science Inventory

A program for the distribution of calibrated radioactive samples, as one function of EPA's quality assurance program for environmental radiation measurements, is described. Included is a discussion of the objectives of the distribution program and a description of the preparation...

317

Principles for Sampling Airborne Radioactivity from Stacks  

SciTech Connect

This book chapter describes the special processes involved in sampling the airborne effluents from nuclear faciities. The title of the book is Radioactive Air Sampling Methods. The abstract for this chapter was cleared as PNNL-SA-45941.

Glissmeyer, John A.

2010-10-18

318

Radioactive diagnostic agent for bone scanning and non-radioactive carrier therefor  

Microsoft Academic Search

A radioactive diagnostic agent for bone scanning, is disclosed which comprises \\/SUP 99mTC and a non-radioactive carrier comprising at least one chosen from methanehydroxydiphosphonic acid and their salts and at least one reducing agent for pertechnetates in a weight ratio of about 1:1 to 7:1 and prevents the accumulation of radioactivity in liver so that definite diagnosis can be assured.

M. Hayashi; M. Hazue; K. Takahashi

1984-01-01

319

Use of Radioactive Iodine for Thyroid Cancer  

PubMed Central

Context Substantial uncertainty persists over the indications for radioactive iodine for thyroid cancer. Use of radioactive iodine over time and the correlates of its use remain unknown. Objective To determine practice patterns, the degree to which hospitals vary in their use of radioactive iodine, and factors that contribute to this variation Design, Setting, Patients We performed time trend analysis of radioactive iodine use in a cohort of 189,219 well-differentiated thyroid cancer patients treated at 981 hospitals associated with the National Cancer Database between 1990 and 2008. We used multilevel analysis to assess the correlates of patient and hospital characteristics on radioactive iodine use in the cohort treated from 20042008. Main Outcome Measure Use of radioactive iodine after total thyroidectomy Results Between 1990 and 2008, across all tumor sizes, there was a significant rise in the proportion of well-differentiated thyroid cancer patients receiving radioactive iodine (1373/3397, versus 11539/20620, P<0.001). Multivariable analysis of patients treated from 2004 to 2008 found that there was a statistical difference in radioactive iodine use between AJCC stage I and IV (odds ratios (OR) 0.34 (0.310.37) but not between stage II/III versus IV (OR 0.97 (0.881.07), 1.06 (0.951.17), respectively). In addition to patient and tumor characteristics, hospital volume was associated with radioactive iodine use. Wide variation in radioactive iodine use existed, and only 21.1% of this variation was accounted for by patient and tumor characteristics. Hospital type and case volume accounted for 17.1% of the variation. After adjusting for available patient, tumor, and hospital characteristics, much of the variance, 29.1%, was attributable to unexplained hospital characteristics. Conclusions Among patients treated for well-differentiated thyroid cancer at hospitals in the National Cancer Database, there was an increase in the proportion receiving radioactive iodine between 1990 and 2008; much of the variation in use was associated with hospital characteristics.

Haymart, MR; Banerjee, M; Stewart, AK; Koenig, RJ; Birkmeyer, JD; Griggs, JJ

2012-01-01

320

Thermodynamic stability of radioactivity standard solutions  

Microsoft Academic Search

Optimal thermodynamic stability conditions must prevail when radioactivity standard solutions are prepared. These conditions are studied, they relate to:The nature of the radioactive ion, which makes it possible to establish the pH of the solubilization medium at a given concentration,The carrier concentration, which is determined by considering the radionuclide production method and the prior concentration in the original solution from

Marie Gabrielle Iroulart

2006-01-01

321

Radioactive ion beam line in Lanzhou  

Microsoft Academic Search

Radioactive ion beam line in Lanzhou (RIBLL) has been constructed for the production of short-lived radioactive nuclei and\\u000a studies of exotic nuclei far from the ?-stability line. It has been put into operation recently at the National Laboratory\\u000a of Heavy Ion Accelerator Lanzhou. RIBLL consists of two doubly achromatic parts with a solid acceptance ???6.5 msr, momentum\\u000a acceptance ?p\\/p=5% and

Wenlong Zhan; Zhongyan Guo; Guanhua Liu; Jianrong Dang; Ruirong He; Sixin Zhou; Quanmin Yin; Yixiao Luo; Yifang Wang; Baowen Wei; Zhiyu Sun; Guoqing Xiao; Jinchuan Wang; Shanhong Jiang; Jiaxing Li; Xiangwei Meng; Wansheng Zhang; Lijun Qing; Quanjin Wang

1999-01-01

322

Tokai Radioactive Ion Accelerator Complex (TRIAC)  

NASA Astrophysics Data System (ADS)

An ISOL-based radioactive nuclear beam (RNB) facility, Tokai Radioactive Ion Accelerator Complex (TRIAC), has been jointly developed by High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA). The facility started to supply RNBs for experiments in 2005 and RNBs including fission fragments with energies up to 1.1MeV/A are available in the present. Several experimental studies were performed successfully using 8Li beams with various energies.

Watanabe, Y. X.; Arai, S.; Arakaki, Y.; Fuchi, Y.; Hirayama, Y.; Imai, N.; Ishiyama, H.; Jeong, S. C.; Kawakami, H.; Miyatake, H.; Niki, K.; Nomura, T.; Okada, M.; Oyaizu, M.; Tanaka, M. H.; Tomizawa, M.; Yoshikawa, N.; Abe, S.; Hanashima, S.; Hashimoto, T.; Ichikawa, S.; Ikezoe, H.; Ishii, T.; Ishizaki, N.; Kabumoto, H.; Katayama, I.; Koizumi, M.; Matsuda, M.; Mitsuoka, S.; Nakanoya, T.; Nishio, K.; Ohuchi, I.; Osa, A.; Sato, T. K.; Takeuchi, S.; Tayama, H.; Tsukihashi, Y.

2007-11-01

323

Transport of Radioactive Material by Alpha Recoil  

SciTech Connect

The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and results of a number of the studies.

Icenhour, A.S.

2005-05-19

324

Transport of Radioactive Material by Alpha Recoil  

Microsoft Academic Search

The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and

A. S. Icenhour

2005-01-01

325

Liquid radioactive waste subsystem design description  

SciTech Connect

The Liquid Radioactive Waste Subsystem provides a reliable system to safely control liquid waste radiation and to collect, process, and dispose of all radioactive liquid waste without impairing plant operation. Liquid waste is stored in radwaste receiver tanks and is processed through demineralizers and temporarily stored in test tanks prior to sampling and discharge. Radwastes unsuitable for discharge are transferred to the Solid Radwaste System.

NONE

1986-06-01

326

Emissions of naturally occurring radioactivity: fireclay mine and refractory plant  

Microsoft Academic Search

Atmospheric emissions of naturally occurring radioactivity were measured at a fireclay mine and the associated plant that produces refractory brick products. The only significant radioactive emission from the mine was radon-222. An analysis of the ore radioactivity and surface area of the mine indicated that the radon released is comparable to that from any similar surface area of similar radioactivity.

1981-01-01

327

PWR-GALE. PWR Effluent Radioactivity Releases  

SciTech Connect

PWR-GALE calculates the expected annual releases of radioactive materials in gaseous and liquid effluents from pressurized light water reactors (PWRs). The calculations are based on data generated from operating reactors, field and laboratory tests, and plant-specific considerations incorporated to reduce the quantity of radioactive materials that may be released to the environment during normal operation including anticipated operational occurrences. PWR-GALE consists of two program, PGALEGS and PGALELQ. PGALEGS calculates the releases of radioactive materials (noble gases, radioactive particulates, carbon-14, tritium, argon-41, and iodine) in gaseous effluents from the waste gas processing system, steam generator blowdown system, condenser air ejector exhaust, containment purge exhaust, ventilation exhaust air from the auxiliary and turbine buildings and the spent fuel area, and steam leakage from the secondary system. PGALELQ calculates the releases of radioactive materials in liquid effluents from processed water generated from the boron recovery system to maintain plant water balance or for tritium control; processed liquid waste discharged from the waste systems, steam generator blowdown treatment system, and that discharged from the chemical waste and condensate demineralizer regeneration system; liquid waste discharged from the turbine building floor drain sumps; and detergent waste.

Willis, C.A. [Nuclear Regulatory Commission, Washington, DC (United States)

1992-01-13

328

Radioactive waste management in a hospital.  

PubMed

Most of the tertiary care hospitals use radioisotopes for diagnostic and therapeutic applications. Safe disposal of the radioactive waste is a vital component of the overall management of the hospital waste. An important objective in radioactive waste management is to ensure that the radiation exposure to an individual (Public, Radiation worker, Patient) and the environment does not exceed the prescribed safe limits. Disposal of Radioactive waste in public domain is undertaken in accordance with the Atomic Energy (Safe disposal of radioactive waste) rules of 1987 promulgated by the Indian Central Government Atomic Energy Act 1962. Any prospective plan of a hospital that intends using radioisotopes for diagnostic and therapeutic procedures needs to have sufficient infrastructural and manpower resources to keep its ambient radiation levels within specified safe limits. Regular monitoring of hospital area and radiation workers is mandatory to assess the quality of radiation safety. Records should be maintained to identify the quality and quantity of radioactive waste generated and the mode of its disposal. Radiation Safety officer plays a key role in the waste disposal operations. PMID:21475524

Khan, Shoukat; Syed, At; Ahmad, Reyaz; Rather, Tanveer A; Ajaz, M; Jan, Fa

2010-01-01

329

Founder Effects and Linkage Disequilibria in Experimental Populations of Drosophila  

PubMed Central

Six laboratory populations of Drosophila paulistorum were examined for changes in gene frequencies at an enzyme locus, tetrazolium oxidase (To). In some of the populations, the alleles were introduced on over 100 independently derived chromosomes. These populations showed considerable stability in gene frequencies although they were at widely different starting frequencies. Other populations were begun with only a few (about 6) independently derived chromosomes. These populations showed significant and somewhat erratic changes in To gene frequencies. The difference in behavior of the two sets of populations was almost certainly caused by linkage effects due to sample size. The implication of these studies in understanding the role of the founder effect in natural populations is briefly discussed.

Powell, Jeffrey R.; Richmond, Rollin C.

1974-01-01

330

Security in the Transport of Radioactive Materials  

SciTech Connect

The United States Department of Energy National Nuclear Security Administration's (DOE/NNSA)Global Threat Reduction Initiative (GTRI), the International Atomic Energy Agency (IAEA) and active IAEA Donor States are working together to strengthen the security of nuclear and radioactive materials during transport to mitigate the risks of theft, diversion, or sabotage. International activities have included preparing and publishing the new IAEA guidance document Security in the Transport of Radioactive Material while ensuring that security recommendations do not conflict with requirements for safety during transport, and developing and providing training programs to assist other countries in implementing radioactive material transport security programs. This paper provides a brief update on the status of these transportation security efforts.

Pope, Ron [Oak Ridge National Laboratory (Retired); Rawl, Richard R [ORNL

2010-01-01

331

Radioactive tank waste remediation focus area  

SciTech Connect

EM`s Office of Science and Technology has established the Tank Focus Area (TFA) to manage and carry out an integrated national program of technology development for tank waste remediation. The TFA is responsible for the development, testing, evaluation, and deployment of remediation technologies within a system architecture to characterize, retrieve, treat, concentrate, and dispose of radioactive waste stored in the underground stabilize and close the tanks. The goal is to provide safe and cost-effective solutions that are acceptable to both the public and regulators. Within the DOE complex, 335 underground storage tanks have been used to process and store radioactive and chemical mixed waste generated from weapon materials production and manufacturing. Collectively, thes tanks hold over 90 million gallons of high-level and low-level radioactive liquid waste in sludge, saltcake, and as supernate and vapor. Very little has been treated and/or disposed or in final form.

NONE

1996-08-01

332

Tilted foil polarization of radioactive beam nuclei  

NASA Astrophysics Data System (ADS)

Tilted foil polarization has up to now been mostly applied to nuclear reaction products recoiling out of a target traversed by a primary particle beam. Being a universal phenomenon it can be applied equally well to beams of particles, primary or secondary, radioactive or other. There are however some technical considerations arising from the nature of the beam particles. Radioactive beams are associated with ground state nuclei. They usually have low nuclear spin and as a consequence-as will be shown later-low polarization. Secondary beams are usually low in intensity and do not impose any constraints on the foils they traverse; unlike intense primary heavy ion beams which, if they traverse the foils, essentially limit the foil material to carbon. We review here briefly the tilted foil polarization process and then discuss an experiment with an isomer beam. Finally we review experiments with radioactive beams, past, present and planned for the future.

Goldring, Gvirol

1992-11-01

333

Radioactivity and electron acceleration in supernova remnants  

SciTech Connect

We argue that the decays of radioactive nuclei related to {sup 44}Ti and {sup 56}Ni ejected during supernova explosions can provide a vast pool of mildly relativistic positrons and electrons which are further accelerated to ultrarelativistic energies by reverse and forward shocks. This interesting link between two independent processes - the radioactivity and the particle acceleration - can be a clue for solution of the well known theoretical problem of electron injection in supernova remnants. In the case of the brightest radio source Cas A, we demonstrate that the radioactivity can supply adequate number of energetic electrons and positrons for interpretation of observational data provided that they are stochastically preaccelerated in the upstream regions of the forward and reverse shocks.

Zirakashvili, V. N. [Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, 142190 Troitsk, Moscow Region (Russian Federation); Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Aharonian, F. A. [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

2011-10-15

334

Landscape of Two-Proton Radioactivity  

NASA Astrophysics Data System (ADS)

Ground-state two-proton (2p) radioactivity is a decay mode found in isotopes of elements with even atomic numbers located beyond the two-proton drip line. So far, this exotic process has been experimentally observed in a few light- and medium-mass nuclides with Z?30. In this study, using state-of-the-art nuclear density functional theory, we globally analyze 2p radioactivity and for the first time identify 2p-decay candidates in elements heavier than strontium. We predict a few cases where the competition between 2p emission and ? decay may be observed. In nuclei above lead, the ?-decay mode is found to be dominating and no measurable candidates for the 2p radioactivity are expected.

Olsen, E.; Pftzner, M.; Birge, N.; Brown, M.; Nazarewicz, W.; Perhac, A.

2013-05-01

335

Radioactive decays at limits of nuclear stability  

NASA Astrophysics Data System (ADS)

The last decades brought impressive progress in synthesizing and studying properties of nuclides located very far from the beta stability line. Among the most fundamental properties of such exotic nuclides, the ones usually established first are the half-life, possible radioactive decay modes, and their relative probabilities. When approaching limits of nuclear stability, new decay modes set in. First, beta decays are accompanied by emission of nucleons from highly excited states of daughter nuclei. Second, when the nucleon separation energy becomes negative, nucleons start being emitted from the ground state. A review of the decay modes occurring close to the limits of stability is presented. The experimental methods used to produce, identify, and detect new species and their radiation are discussed. The current theoretical understanding of these decay processes is reviewed. The theoretical description of the most recently discovered and most complex radioactive processthe two-proton radioactivityis discussed in more detail.

Pftzner, M.; Karny, M.; Grigorenko, L. V.; Riisager, K.

2012-04-01

336

The UK Committee on Radioactive Waste Management.  

PubMed

The UK Committee on Radioactive Waste Management is charged with recommending to Government, by July 2006, options for the long term management of the UK's radioactive waste legacy. These options should inspire public confidence. Now, more than halfway into the time allotted, we, as two former members of the Committee, express our concerns at the wayward approach that has been adopted. The Committee has placed emphasis on gaining public confidence but this has been done at the expense of recruiting the best scientific expertise in the management of radioactive waste, an act which we believe will actually undermine public confidence. Furthermore, given also the immense importance of this decision to public safety, national security and the national interest, we believe urgent steps should be taken to review the Committee's process, its management and its sponsorship. PMID:16286694

Baverstock, Keith; Ball, David J

2005-09-06

337

Wide range radioactive gas concentration detector  

DOEpatents

A wide range radioactive gas concentration detector and monitor which is capable of measuring radioactive gas concentrations over a range of eight orders of magnitude. The device of the present invention is designed to have an ionization chamber which is sufficiently small to give a fast response time for measuring radioactive gases but sufficiently large to provide accurate readings at low concentration levels. Closely spaced parallel plate grids provide a uniform electric field in the active region to improve the accuracy of measurements and reduce ion migration time so as to virtually eliminate errors due to ion recombination. The parallel plate grids are fabricated with a minimal surface area to reduce the effects of contamination resulting from absorption of contaminating materials on the surface of the grids. Additionally, the ionization chamber wall is spaced a sufficient distance from the active region of the ionization chamber to minimize contamination effects.

Anderson, David F. (Los Alamos, NM)

1984-01-01

338

Completion of the Radioactive Materials Packaging Handbook  

SciTech Connect

The Radioactive Materials Packaging Handbook: Design, Operation and Maintenance, which will serve as a replacement for the Cask Designers Guide (Shappert, 1970), has now been completed and submitted to the Oak Ridge National Laboratory (ORNL) electronics publishing group for layout and printing; it is scheduled to be printed in late spring 1998. The Handbook, written by experts in their particular fields, is a compilation of technical chapters that address the design aspects of a package intended for transporting radioactive material in normal commerce; it was prepared under the direction of M. E. Wangler of the US Department of Energy (DOE) and is intended to provide a wealth of technical guidance that will give designers a better understanding of the regulatory approval process, preferences of regulators on specific aspects of package design, and the types of analyses that should be considered when designing a package to carry radioactive materials.

Shappert, L.B.

1998-02-01

339

Perspectives of Radioactive Contamination in Nuclear War  

PubMed Central

The degrees of risk associated with the medical, industrial and military employment of nuclear energy are compared. The nature of radioactive contamination of areas and of persons resulting from the explosion of nuclear weapons, particularly the relationship between the radiation exposure and the amount of physical debris, is examined. Some theoretical examples are compared quantitatively. It is concluded that the amount of radio-activity that may be carried on the contaminated person involves a minor health hazard from gamma radiation, compared to the irradiation arising from contaminated areas.

Waters, W. R.

1967-01-01

340

Tokai Radioactive Ion Accelerator Complex (TRIAC)  

Microsoft Academic Search

.\\u000a An ISOL-based radioactive nuclear beam (RNB) facility,\\u000a Tokai Radioactive Ion Accelerator Complex (TRIAC),\\u000a has been jointly developed\\u000a by High Energy Accelerator Research Organization (KEK)\\u000a and Japan Atomic Energy Agency (JAEA).\\u000a The facility started to supply RNBs for experiments in 2005\\u000a and RNBs including fission fragments with energies up to 1.1MeV\\/A\\u000a are available in the present.\\u000a Several experimental studies were

Y. X. Watanabe; S. Arai; Y. Arakaki; Y. Fuchi; Y. Hirayama; N. Imai; H. Ishiyama; S. C. Jeong; H. Kawakami; H. Miyatake; K. Niki; T. Nomura; M. Okada; M. Oyaizu; M. H. Tanaka; M. Tomizawa; N. Yoshikawa; S. Abe; S. Hanashima; T. Hashimoto; S. Ichikawa; H. Ikezoe; T. Ishii; N. Ishizaki; H. Kabumoto; I. Katayama; M. Koizumi; M. Matsuda; S. Mitsuoka; T. Nakanoya; K. Nishio; I. Ohuchi; A. Osa; T. K. Sato; S. Takeuchi; H. Tayama; Y. Tsukihashi

2007-01-01

341

Radioactive-Waste Incineration at Purdue University.  

National Technical Information Service (NTIS)

A study conducted at Purdue University to evaluate the feasibility of using a small (45 kg/h), inexpensive (less than $10K) incinerator for incinerating low-level radioactive waste is described. An oil-fired, dual-chamber pathological waste incinerator wa...

1982-01-01

342

Notes on Incineration of Radioactive Waste.  

National Technical Information Service (NTIS)

The problem of finding commercial sites for the disposal of low-level radioactive waste and temporary storage of residues containing transuranic elements has led to research on using a method to reduce the volume of the waste originating from nuclear inst...

L. M. Martin

1984-01-01

343

Helium-Shell Nucleosynthesis and Extinct Radioactivities  

NASA Astrophysics Data System (ADS)

We present details of explosive nucleosynthesis in the helium-burning shell of a 25 solar mass star. We describe the production of short-lived radioactivities in this environment. We finally describe how to access the details of our calculations over the world-wide web.

Meyer, B. S.; The, L.-S.; Clayton, D. D.; El Eid, M. F.

2004-03-01

344

Canister arrangement for storing radioactive waste  

DOEpatents

The subject invention relates to a canister arrangement for jointly storing high level radioactive chemical waste and metallic waste resulting from the reprocessing of nuclear reactor fuel elements. A cylindrical steel canister is provided with an elongated centrally disposed billet of the metallic waste and the chemical waste in vitreous form is disposed in the annulus surrounding the billet.

Lorenzo, Donald K. (Knoxville, TN); Van Cleve, Jr., John E. (Kingston, TN)

1982-01-01

345

Discrimination of airborne radioactivity from radon progeny  

Microsoft Academic Search

Naturally occurring radon and thoron progeny are the most interfering nuclides in the aerosol monitoring system. The high background and fluctuation of natural radioactivity on the filter can cause an error message to the aerosol monitor. A theoretical model was applied in the simulation of radon and thoron progeny behavior in the environment and on the filter. Results show that

Ching-Jiang Chen; Pao-Shan Weng; Tieh-Chi Chu; Earl O. Knutson

1994-01-01

346

Survey of Radioactivities Induced by Lithium Ions.  

National Technical Information Service (NTIS)

Lithium-induced nuclear reactions which lead to radioactivities are surveyed for application to experiments with intense lithium-ion beams from pulsed power generators. Positive Q-value reactions for 7Li ions of up to 15 MeV on carbon, aluminum, steel, br...

F. C. Young D. V. Rose

1992-01-01

347

Airborne radioactivity measurements from the chernobyl plume  

Microsoft Academic Search

Airborne gamma-ray measurements were made aboard the Pacific Northwest Laboratory (PNL) DC-3 and the National Oceanic and Atmospheric Administration (NOAA) King Air research aircraft before and during the first passage of the Chernobyl radioactive cloud over the west coast of the North American continent. Measurements were made from Anchorage, Alaska south to Reno, Nevada. Calculated trajectories were used to estimate

E. A. Lepel; W. K. Hensley; J. F. Boatman; K. M. Busness; W. E. Davis; D. E. Robertson; W. G. N. Slinn

1988-01-01

348

A Sensitive Cloud Chamber without Radioactive Sources  

ERIC Educational Resources Information Center

|We present a sensitive diffusion cloud chamber which does not require any radioactive sources. A major difference from commonly used chambers is the use of a heat sink as its bottom plate. The result of a performance test of the chamber is given. (Contains 8 figures.)|

Zeze, Syoji; Itoh, Akio; Oyama, Ayu; Takahashi, Haruka

2012-01-01

349

Airborne penetration of radioactive clouds. Master's thesis  

Microsoft Academic Search

This report evaluates the threat to aircrew members when their aircraft approaches and subsequently penetrates a descending radioactive cloud generated by a nuclear weapon surface burst. The re-development of Hickman's program consists of a remodeling of the computational methods for sky-shine dose and cloud model. The code also computes the ionizing dose rate an air crew member receives when flying

1983-01-01

350

Method for decontamination of radioactive metal surfaces  

DOEpatents

Disclosed is a method for removing radioactive contaminants from metal surfaces by applying steam containing an inorganic acid and cerium IV. Cerium IV is applied to contaminated metal surfaces by introducing cerium IV in solution into a steam spray directed at contaminated metal surfaces. Cerium IV solution is converted to an essentially atomized or vapor phase by the steam.

Bray, L.A.

1996-08-13

351

MIDGE LARVAE AS INDICATORS OF RADIOACTIVE POLLUTION  

Microsoft Academic Search

The role of midge larvae, or blood worms, as an indicator or radioactive ; pollution of surface waters was investigated. The larvae of two species were ; obtained from a silt deposit and studies were made on larvae ecology and feeding ; habits and their position in specific food chains. The uptake of Fe⁵⁹ and ; P³² by the larvae

1961-01-01

352

Effect of Scattering Neutrons on Induced Radioactivity  

Microsoft Academic Search

M. DANYSZ, J. Rotblat, L. Wertenstein and M. Zyw1 have found that iodine and silver exposed to neutrons acquire a stronger radioactivity if the neutrons are allowed to pass through lead or gold. We have investigated further this effect using different substances as scatterers, in the form of cylinders of 55 mm. height and 24.5 mm. diameter, with a coaxial

J. Rotblat; M. Zyw

1936-01-01

353

Half-lives of some Radioactive Isotopes  

Microsoft Academic Search

IN the course of investigations with radioactive isotopes in this Department, anomalous rates of decay have been observed with some isotopes in particular chemical forms. The escape of iodine-131 from evaporated samples of sodium iodide has already been reported by one of us1, and Hevesy2 has reported the escape of carbon-14 from exposed samples of barium carbonate. Anomalies have also

W. K. Sinclair; A. F. Holloway

1951-01-01

354

OXIDATION OF RADIOACTIVITY GLUCOSE BY AERATED SLUDGE  

Microsoft Academic Search

Treatment of organic waste by aerated sludge depends on the metabolic ; activitles of many microorganisms present in the mixed liquor. A study was made ; of carbohydrate dissimilation by sludge organisms present in organic wastes. ; Radioactive glucose, labeled at the carbon-1 or carbon-6 atom, was used to follow ; the fate of the glucose molecule with respect to

N. Porges; A. E. Wasserman; W. J. Hopkins; L. Jasewicz

1958-01-01

355

Annual radioactive waste tank inspection program - 1992  

SciTech Connect

Aqueous radioactive wastes from Savannah River Site (SRS) separations processes are contained in large underground carbon steel tanks. Inspections made during 1992 to evaluate these vessels and evaluations based on data accrued by inspections made since the tanks were constructed are the subject of this report.

McNatt, F.G.

1992-12-31

356

Institutional storage and disposal of radioactive materials.  

PubMed

Storage and disposal of radioactive materials from nuclear medicine operations must be considered in the overall program design. The storage of materials from daily operation, materials in transit, and long-term storage represent sources of exposure. The design of storage facilities must include consideration of available space, choice of material, occupancy of surrounding areas, and amount of radioactivity anticipated. Neglect of any of these factors will lead to exposure problems. The ultimate product of any manipulation of radioactive material will be some form of radioactive waste. This waste may be discharged into the environment or placed within a storage area for packaging and transfer to a broker for ultimate disposal. Personnel must be keenly aware of packaging regulations of the burial site as well as applicable federal and local codes. Fire codes should be reviewed if there is to be storage of flammable materials in any area. Radiation protection personnel should be aware of community attitudes when considering the design of the waste program. PMID:3749915

St Germain, J

1986-07-01

357

Remediation of groundwater contaminated with radioactive compounds  

Technology Transfer Automated Retrieval System (TEKTRAN)

Both naturally radioactive isotopes and isotopes from man-made sources may appear in groundwater. Depending on the physical and chemical characteristics of the contaminant, different types of treatment methods must be applied to reduce the concentration. The following chapter discusses treatment opt...

358

Simplifying the Mathematical Treatment of Radioactive Decay  

ERIC Educational Resources Information Center

|Derivation of the law of radioactive decay is considered without prior knowledge of calculus or the exponential series. Calculus notation and exponential functions are used because ultimately they cannot be avoided, but they are introduced in a simple way and explained as needed. (Contains 10 figures, 1 box, and 1 table.)|

Auty, Geoff

2011-01-01

359

Physics with energetic radioactive ion beams  

SciTech Connect

Beams of short-lived, unstable nuclei have opened new dimensions in studies of nuclear structure and reactions. Such beams also provide key information on reactions that take place in our sun and other stars. Status and prospects of the physics with energetic radioactive beams are summarized.

Henning, W.F.

1996-12-31

360

X-Ray Diffraction on Radioactive Materials.  

National Technical Information Service (NTIS)

X-ray diffraction studies on radioactive materials are discussed with the aim of providing a guide to new researchers in the field. Considerable emphasis is placed on the safe handling and loading of not-too-exotic samples. Special considerations such as ...

D. Schiferl R. B. Roof

1978-01-01

361

Low Radioactivity Spectral gamma Calibration Facility.  

National Technical Information Service (NTIS)

A low radioactivity calibration facility has been constructed at the Nevada Test Site (NTS). This facility has four calibration models of natural stone that are 3 ft in diameter and 6 ft long, with a 12 in. cored borehole in the center of each model and a...

M. A. Mathews H. R. Bowman L. H. Huang M. J. Lavelle A. R. Smith

1986-01-01

362

Safe transport of radioactive materials in Egypt  

NASA Astrophysics Data System (ADS)

In Egypt the national regulations for safe transport of radioactive materials (RAM) are based on the International Atomic Energy Agency (IAEA) regulations. In addition, regulations for the safe transport of these materials through the Suez Canal (SC) were laid down by the Egyptian Atomic Energy Authority (EAEA) and the Suez Canal Authority (SCA). They are continuously updated to meet the increased knowledge and the gained experience. The technical and protective measures taken during transport of RAM through SC are mentioned. Assessment of the impact of transporting radioactive materials through the Suez Canal using the INTERTRAN computer code was carried out in cooperation with IAEA. The transported activities and empty containers, the number of vessels carrying RAM through the canal from 1963 to 1991 and their nationalities are also discussed. The protective measures are mentioned. A review of the present situation of the radioactive wastes storage facilities at the Atomic Energy site at Inshas is given along with the regulation for safe transportation and disposal of radioactive wastes

El-Shinawy, Rifaat M. K.

1994-07-01

363

Use of Radioactive Tracers in Dynamic Sedimentology.  

National Technical Information Service (NTIS)

In the first part, developments in the use of radioactive tracers in sedimentology are recalled together with the corresponding fields of application and the identities of the main users. The state-of-the-art in France is also discussed; The main characte...

F. Tola

1982-01-01

364

X rays and radioactivity: a complete surprise.  

National Technical Information Service (NTIS)

The discoveries of X rays and of radioactivity came as complete experimental surprises; the physicists, at that time, had no previous hint of a possible structure of atoms. It is difficult now, knowing what we know, to replace ourselves in the spirit, ast...

P. Radvanyi M. Bordry

1995-01-01

365

Indirect estimation of radioactivity in containerized cargo  

Microsoft Academic Search

Naturally occurring radioactive material in containerized cargo challenges the state of the art in national and international efforts to detect illicit nuclear and radiological material in transported containers. Current systems are being evaluated and new systems envisioned to provide the high probability of detection necessary to thwart potential threats, combined with extremely low nuisance and false alarm rates necessary to

Kenneth D. Jarman; Chad Scherrer; L. E. Smith; Lawrence Chilton; K. K. Anderson; Jennifer J. Ressler; Lynn L. Trease

2011-01-01

366

Obtaining and Investigating Unconventional Sources of Radioactivity  

ERIC Educational Resources Information Center

|This paper provides examples of naturally radioactive items that are likely to be found in most communities. Additionally, there is information provided on how to acquire many of these items inexpensively. I have found that the presence of these materials in the classroom is not only useful for teaching about nuclear radiation and debunking the

Lapp, David R.

2010-01-01

367

Attempts to develop radioactive anticancer drugs  

Microsoft Academic Search

Since 1953, attempts have been made to develop radioactive drugs. Preparations of tritiated menadiol sodium diphosphate (T-MNDP) of high specific activity showed a definite, though limited, but sometimes useful effect in the treatment of certain patients with advanced tumors, especially adenocarcinoma of the colon and of the pancreas and malignant melanoma of the skin. The next step was to use

Joseph S. Mitchell; Ian Brown; B. Chir; Robert N. Carpenter

1983-01-01

368

THE DECONTAMINATION OF RADIOACTIVE LABORATORY WATER  

Microsoft Academic Search

The processing of radioactively poisoned waste water is, in many ; respects, problematic in spite of numerous investigations. Some results, ; obtained in coprecipitation studies on Ca⁴⁵, Fe⁵⁹, Zn⁶⁵, and Tl\\/; sup 204\\/ in distilled and tap wate r with or without carriers, are discussed. A ; table shows the most favorable precipitation conditions or results on additionai ; radioisotopes,

H. Koch; W. Weiland

1962-01-01

369

Radioactive source detection by sensor networks  

Microsoft Academic Search

Detection limits of sensor networks for moving radioactive sources are characterized, using Bayesian methods in conjunction with computer simulation. These studies involve point sources moving at constant velocity, emulating vehicular conveyance on a straight road. For networks involving ten nodes, respective Bayesian methods are implementable in real time. We probe the increased computational requirements incurred by larger numbers of nodes

Sean M. Brennan; Angela M. Mielke; David C. Torney

2005-01-01

370

Fastener tightening in a radioactive (hot) cell  

Microsoft Academic Search

Accurate remote tightening of fasteners in a radioactive (Hot) cell can be a very exasperating experience. Viewing can be difficult (in many places) and work sometimes must be done using mirrors and\\/or cameras. If electro mechanical manipulators are used, the operator has no ''feel,'' which often can result in cross threading, or improper torquing of fasteners. At the Interim Examination

Kalk

1986-01-01

371

Annual radioactive waste tank inspection program - 1996  

SciTech Connect

Aqueous radioactive wastes from Savannah River Site (SRS) separations processes are contained in large underground carbon steel tanks. Inspections made during 1996 to evaluate these vessels, and evaluations based on data accrued by inspections performed since the tanks were constructed, are the subject of this report.

McNatt, F.G.

1997-04-01

372

Security in the Transport of Radioactive Materials  

Microsoft Academic Search

The United States Department of Energy National Nuclear Security Administration's (DOE\\/NNSA)Global Threat Reduction Initiative (GTRI), the International Atomic Energy Agency (IAEA) and active IAEA Donor States are working together to strengthen the security of nuclear and radioactive materials during transport to mitigate the risks of theft, diversion, or sabotage. International activities have included preparing and publishing the new IAEA guidance

Ron Pope; Richard R Rawl

2010-01-01

373

Evaluation of Terrorist Interest in Radioactive Wastes  

Microsoft Academic Search

Since September 11, 2001, intelligence gathered from Al Qaeda training camps in Afghanistan, and the ensuing terrorist activities, indicates nuclear material security concerns are valid. This paper reviews available information on sealed radioactive sources thought to be of interest to terrorists, and then examines typical wastes generated during environmental management activities to compare their comparative 'attractiveness' for terrorist diversion. Sealed

J. N. McFee; J. M. Langsted; M. E. Young; J. E. Day

2006-01-01

374

Radioactive fallout from Chinese nuclear weapons test  

Microsoft Academic Search

Radioactive fallout from this Chinese nuclear test resulted in measurable deposition of short-lived debris over much of the United States. The fallout levels varied by more than 1000-fold and showed significant temporary or spatial fractionation with higher levels of deposition being associated with rain. The particle size with which the airborne debris was associated decreased continuously with time following detonation

C. W. Thomas; J. K. Soldat; W. B. Silker; R. W. Perkins

1976-01-01

375

Hazardous chemical and radioactive wastes at Hanford  

SciTech Connect

The Hanford Site was established in 1944 to produce plutonium for defense. During the past four decades, a number of reactors, processing facilities, and waste management facilities have been built at Hanford for plutonium production. Generally, Hanford`s 100 Area was dedicated to reactor operation; the 200 Area to fuel reprocessing, plutonium recovery, and waste management; and the 300 Area to fuel fabrication and research and development. Wastes generated from these operations included highly radioactive liquid wastes, which were discharged to single- and double-shell tanks; solid wastes, including both transuranic (TRU) and low-level wastes, which were buried or discharged to caissons; and waste water containing low- to intermediate-level radioactivity, which was discharged to the soil column via near-surface liquid disposal units such as cribs, ponds, and retention basins. Virtually all of the wastes contained hazardous chemical as well as radioactive constituents. This paper will focus on the hazardous chemical components of the radioactive mixed waste generated by plutonium production at Hanford. The processes, chemicals used, methods of disposition, fate in the environment, and actions being taken to clean up this legacy are described by location.

Keller, J.F.; Stewart, T.L.

1991-07-01

376

Hazardous chemical and radioactive wastes at Hanford  

SciTech Connect

The Hanford Site was established in 1944 to produce plutonium for defense. During the past four decades, a number of reactors, processing facilities, and waste management facilities have been built at Hanford for plutonium production. Generally, Hanford's 100 Area was dedicated to reactor operation; the 200 Area to fuel reprocessing, plutonium recovery, and waste management; and the 300 Area to fuel fabrication and research and development. Wastes generated from these operations included highly radioactive liquid wastes, which were discharged to single- and double-shell tanks; solid wastes, including both transuranic (TRU) and low-level wastes, which were buried or discharged to caissons; and waste water containing low- to intermediate-level radioactivity, which was discharged to the soil column via near-surface liquid disposal units such as cribs, ponds, and retention basins. Virtually all of the wastes contained hazardous chemical as well as radioactive constituents. This paper will focus on the hazardous chemical components of the radioactive mixed waste generated by plutonium production at Hanford. The processes, chemicals used, methods of disposition, fate in the environment, and actions being taken to clean up this legacy are described by location.

Keller, J.F.; Stewart, T.L.

1991-07-01

377

Repository for radioactive waste-vault backfill  

US Patent & Trademark Office Database

A method of forming a repository for radioactive waste comprises locating the waste in a subterranean vault and backfilling the vault with a filling material which is water permeable and provides a substantial reservoir of available alkalinity such that any ground water permeating through the filling material to the waste has a pH of at least 10.5.

Hooper; Alan James (Gloucester, GB)

1998-04-14

378

Annual Radioactive Waste Tank Inspection Program - 1997  

SciTech Connect

Aqueous radioactive wastes from Savannah River Site (SRS) separations processes are contained in large underground carbon steel tanks. Inspections made during 1997 to evaluate these vessels, and evaluations based on data accrued by inspections performed since the tanks were constructed are the subject of this report.

McNatt, F.G. [Westinghouse Savannah River Company, AIKEN, SC (United States)

1998-05-01

379

Gamma spectrometry calibrations with natural radioactive materials  

NASA Astrophysics Data System (ADS)

Natural radioactive materials were used for detector calibration. We found that KCl is a very suitable material for this purpose. The efficiency curve shape was derived by using ? ray lines of 214Bi normalised using a known quantity of KCl in the same geometry. The best fit was found by the least squares method. The summing correction coefficients for 214Bi are determined.

Panteli?, Gordana

1996-02-01

380

Clay barriers in radioactive waste disposal  

Microsoft Academic Search

Deep geological is one of the preferred options for the disposal of high level radioactive waste. In most designs, the canisters placed in drifts or boreholes are surrounded by an engineered barrier usually made of compacted swelling clay. The barrier undergoes severe heating from the canisters and hydration from the host rock. In this situation a number of interacting thermal,

Antonio Gens; Sebasti Olivella

2001-01-01

381

Annual Radioactive Waste Tank Inspection Program - 1998  

SciTech Connect

Aqueous radioactive wastes from Savannah River Site separations processes are contained in large underground carbon steel tanks. Inspections made during 1998 to evaluate these vessels and auxiliary appurtenances, along with evaluations based on data accrued by inspections performed since the tanks were constructed, are the subject of this report.

McNatt, F.G.

1999-10-27

382

ANNUAL RADIOACTIVE WASTE TANK INSPECTION PROGRAM 2008  

SciTech Connect

Aqueous radioactive wastes from Savannah River Site (SRS) separations and vitrification processes are contained in large underground carbon steel tanks. Inspections made during 2008 to evaluate these vessels and other waste handling facilities along with evaluations based on data from previous inspections are the subject of this report.

West, B.; Waltz, R.

2009-06-11

383

Artificial Radioactivity Reference Horizons in Greenland Firn.  

National Technical Information Service (NTIS)

Total beta measurements have been made on melt water samples from a stratigraphically dated firn core profile from the inland Greenland ice sheet (77 deg 10 min N, 61 deg 08 min W). A marked increase in radioactivity is found in the 1953 firn layer which ...

G. Crozaz C. C. Langway E. Picciotto

1966-01-01

384

RADIOACTIVE MATERIALS IN BIOSOLIDS: DOSE MODELING  

EPA Science Inventory

The Interagency Steering Committee on Radiation Standards (ISCORS) has recently completed a study of the occurrence within the United States of radioactive materials in sewage sludge and sewage incineration ash. One component of that effort was an examination of the possible tra...

385

Radioactive waste disposal in granite. [Stripa mine  

Microsoft Academic Search

The principal geotechnical problems in selecting a repository site for radioactive waste disposal in granite are to evaluate the suitability of the rock mass in terms of: (1) fracture characteristics, (2) thermomechanical effects, and (3) fracture hydrology. Underground experiments in a mine in Sweden have provided an opportunity to study these problems. The research has demonstrated the importance of hydrogeology

P. A. Witherspoon; D. J. Watkins

1982-01-01

386

RADIOACTIVITY OF BATHOLITHE OF ELBEMA (HOGGAR)  

Microsoft Academic Search

The distribution of uranium, potassium, and alpha and gamma ; radioactivity of a granite massif in the Hoggar, Sahara was examined. ; Statistical application of results show the existence of a close relationship ; between activity fluctuations and uranium content variations. There is, on the ; other hand, no clear correlation between activity and KO content. (auth);

Coulomb

1958-01-01

387

RADIOACTIVE WASTE DISPOSAL IN THE RUSSIAN FEDERATION  

Microsoft Academic Search

There are currently few licensed repositories for disposal of radioactive waste within the Russian Federation. This impasse has evolved due to extreme concerns by local and state governments about the safety of such facilities and the lack of coordinated action by the many ministries and agencies that each have some responsibility for the design, siting, licensing and operation of these

Nikolai Laverov; Yuriy Shiyan; Paul Childress

2000-01-01

388

EVALUATION OF BITUMENS FOR RADIOACTIVE WASTE IMMOBILIZATION  

Microsoft Academic Search

The Brazilian research center CDTN - Centro de Desenvolvimento da Tecnologia Nuclear - has been carrying out research on the incorporation of radioactive wastes in different types of bitumen, aiming to obtain monolithic, homogeneous, chemically and mechanically stable waste forms. The solidification of waste is mandatory if compliance with the safety standards for transport, storage and disposal are sought. The

Marcia Flavia; Righi Guzella; Tnia Valria da Silva

389

Radioactive Waste Management Criteria in Fusion Reactor Materials Selection.  

National Technical Information Service (NTIS)

Fusion reactors will have to meet both quantitative and qualitative criteria for the disposal and/or reuse of radioactive materials. The most important quantitative criteria presently govern the near-surface disposal of radioactive wastes in the United St...

J. S. Herring S. Fetter

1987-01-01

390

49 CFR 172.438 - RADIOACTIVE YELLOW-II label.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false RADIOACTIVE YELLOW-II label. 172.438 Section 172.438 Transportation Other Regulations Relating to Transportation...REQUIREMENTS, AND SECURITY PLANS Labeling § 172.438 RADIOACTIVE YELLOW-II label. (a) Except...

2012-10-01

391

77 FR 10401 - Low-Level Radioactive Waste Management Issues  

Federal Register 2010, 2011, 2012, 2013

...NRC-2011-0012] Low-Level Radioactive Waste Management Issues AGENCY: Nuclear Regulatory...assessment as part of its radioactive waste management decision-making. The DOE...Assessment Directorate, Division of Waste Management and Environmental...

2012-02-22

392

77 FR 26991 - Low-Level Radioactive Waste Management Issues  

Federal Register 2010, 2011, 2012, 2013

...3150-AI92 Low-Level Radioactive Waste Management Issues AGENCY: Nuclear Regulatory...and Low-Level Radioactive Waste Management'' (76 FR 50500; August...Assessment Directorate, Division of Waste Management and Environmental...

2012-05-08

393

10 CFR 39.69 - Radioactive contamination control.  

Code of Federal Regulations, 2013 CFR

... Energy 1 2013-01-01 2013-01-01 false Radioactive contamination control. 39.69 Section 39.69 Energy...WELL LOGGING Radiation Safety Requirements § 39.69 Radioactive contamination control. (a) If the licensee...

2013-01-01

394

Radioactive Effluents, Portsmouth Gaseous Diffusion Plant, Calendar Year 1982.  

National Technical Information Service (NTIS)

Radioactive discharges from the Portsmouth Gaseous Diffusion Plant are discussed and tabulated. Tables indicate both the location of the discharge and the nuclides discharged. All discharges for 1982 are well below the Radioactive Concentration Guide limi...

T. A. Acox L. F. Hary L. S. Klein

1983-01-01

395

Legislative developments in radioactive materials transportation, April 1993--August 1993.  

National Technical Information Service (NTIS)

This is the seventh report prepared by the National Conference of State Legislatures (NCSL) on developments in radioactive materials transportation. It updates information contained in the April 1993 report on Legislative Developments in Radioactive Mater...

J. B. Reed J. Cummins

1993-01-01

396

10 CFR 835.1201 - Sealed radioactive source control.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Sealed radioactive source control. 835.1201 Section 835.1201 Energy DEPARTMENT OF ENERGY OCCUPATIONAL...RADIATION PROTECTION Sealed Radioactive Source Control § 835.1201 Sealed...

2013-01-01

397

10 CFR 835.1202 - Accountable sealed radioactive sources.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Accountable sealed radioactive sources. 835.1202 Section 835.1202 Energy DEPARTMENT OF ENERGY OCCUPATIONAL RADIATION PROTECTION Sealed Radioactive Source Control § 835.1202 Accountable...

2013-01-01

398

Status of the Holifield Radioactive Ion Beam Facility.  

National Technical Information Service (NTIS)

The Holifield Radioactive Ion Beam Facility received authorization in December 1996 to commence routine operation as a National User Facility. Significant progress has been made toward the goal of providing high-quality radioactive ion beams. The task of ...

M. J. Meigs

2001-01-01

399

Aspects of Underground Disposal of Radioactive Waste in Rock Salt.  

National Technical Information Service (NTIS)

The subject of the thesis concerns disposal of radioactive waste in underground rock-salt formations. Rock salt is one of the few potential host formations for accomodating radioactive waste; it has a relatively high thermal conductivity and is practicall...

W. M. G. T. van den Broek

1989-01-01

400

Radioactive waste vitrification offgas analysis proposal  

SciTech Connect

Further validation of the Hanford Waste Vitrification Plant (HWVP) feed simulants will be performed by analyzing offgases during crucible melting of actual waste glasses and simulants. The existing method of vitrifying radioactive laboratory-scale samples will be modified to allow offgas analysis during preparation of glass for product testing. The analysis equipment will include two gas chromatographs (GC) with thermal conductivity detectors (TCD) and one NO/NO{sub x} analyzer. This equipment is part of the radioactive formating offgas system. The system will provide real-time analysis of H{sub 2}, O{sub 2}, N{sub 2}, NO, N{sub 2}O, NO{sub 2}, CO, CO{sub 2}, H{sub 2}O, and SO{sub 2}. As with the prior melting method, the product glass will be compatible with durability testing, i.e., Product Consistency Test (PCT) and Material Characterization Center (MCC-1), and crystallinity analysis. Procedures have been included to ensure glass homogeneity and quenching. The radioactive glass will be adaptable to Fe{sup +2}/{Sigma}Fe measurement procedures because the atmosphere above the melt can be controlled. The 325 A-hot cell facility is being established as the permanent location for radioactive offgas analysis during formating, and can be easily adapted to crucible melt tests. The total costs necessary to set up and perform offgas measurements on the first radioactive core sample is estimated at $115K. Costs for repeating the test on each additional core sample are estimated to be $60K. The schedule allows for performing the test on the next available core sample.

Nelson, C.W.; Morrey, E.V.

1993-11-01

401

Accelerated radioactive beams from REX-ISOLDE  

NASA Astrophysics Data System (ADS)

In 2001 the linear accelerator of the Radioactive beam EXperiment (REX-ISOLDE) delivered for the first time accelerated radioactive ion beams, at a beam energy of 2 MeV/u. REX-ISOLDE uses the method of charge-state breeding, in order to enhance the charge state of the ions before injection into the LINAC. Radioactive singly-charged ions from the on-line mass separator ISOLDE are first accumulated in a Penning trap, then charge bred to an /A/q<4.5 in an electron beam ion source (EBIS) and finally accelerated in a LINAC from 5 keV/u to energies between 0.8 and 2.2 MeV/u. Dedicated measurements with REXTRAP, the transfer line and the EBIS have been carried out in conjunction with the first commissioning of the accelerator. Thus the properties of the different elements could be determined for further optimization of the system. In two test beam times in 2001 stable and radioactive Na isotopes (23Na-26Na) have been accelerated and transmitted to a preliminary target station. There 58Ni- and 9Be- and 2H-targets have been used to study exited states via Coulomb excitation and neutron transfer reactions. One MINIBALL triple cluster detector was used together with a double sided silicon strip detector to detect scattered particles in coincidence with ?-rays. The aim was to study the operation of the detector under realistic conditions with ?-background from the ?-decay of the radioactive ions and from the cavities. Recently for efficient detection eight tripple Ge-detectors of MINIBALL and a double sided silicon strip detector have been installed. We will present the first results obtained in the commissioning experiments and will give an overview of realistic beam parameters for future experiments to be started in the spring 2002.

ISOLDE Collaboration; Kester, O.; Sieber, T.; Emhofer, S.; Ames, F.; Reisinger, K.; Reiter, P.; Thirolf, P. G.; Lutter, R.; Habs, D.; Wolf, B. H.; Huber, G.; Schmidt, P.; Ostrowski, A. N.; von Hahn, R.; Repnow, R.; Fitting, J.; Lauer, M.; Scheit, H.; Schwalm, D.; Podlech, H.; Schempp, A.; Ratzinger, U.; Forstner, O.; Wenander, F.; Cederkll, J.; Nilsson, T.; Lindroos, M.; Fynbo, H.; Franchoo, S.; Bergmann, U.; Oinonen, M.; yst, J.; den Bergh, P. Van; Duppen, P. Van; Huyse, M.; Warr, N.; Weisshaar, D.; Eberth, J.; Jonson, B.; Nyman, G.; Pantea, M.; Simon, H.; Shrieder, G.; Richter, A.; Tengblad, O.; Davinson, T.; Woods, P. J.; Bollen, G.; Weissmann, L.; Liljeby, L.; Rensfelt, K. G.

2003-05-01

402

Radioactivity concentrations in soils of the Xiazhuang granite area, China  

Microsoft Academic Search

The natural radioactivity of soils at the Xiazhuang granite massif of Southern China has been studied. The radioactivities of 55 samples have been measured with a low-background HPGe detector. The radioactivity concentrations of 238U and 40K ranged from 40.2 to 442 and from 442 to 913Bq\\/kg, respectively, while the radioactivity concentration of 232Th varied only slightly. In order to evaluate

Ya-xin Yang; Xin-min Wu; Zhong-ying Jiang; Wei-xing Wang; Ji-gen Lu; Jun Lin; Lei-Ming Wang; Yuan-fu Hsia

2005-01-01

403

Stable radioactive diagnostic agent and a non-radioactive carrier therefor  

Microsoft Academic Search

A stable non-radioactive carrier for use in production of ⁹⁹ \\/SUP m\\/ Tc-labeled radioactive diagnostic agent comprising a chelating agent, a water-soluble reducing agent for pertechnetate and a stabilizer chosen from ascorbic acid and erythorbic acid, and their pharmaceutically acceptable salts and esters in an amount of more than about 100 moles per 1 mol of said water-soluble reducing agent.

M. Azuma; M. Hazue

1984-01-01

404

Radioactive Materials Packaging (RAMPAC) Radioactive Materials Incident Report (RMIR). RAMTEMP users manual  

SciTech Connect

The purpose of this document is to familiarize the potential user with RadioActive Materials PACkaging (RAMPAC), Radioactive Materials Incident Report (RMIR), and RAMTEMP databases. RAMTEMP is a minor image of RAMPAC. This reference document will enable the user to access and obtain reports from databases while in an interactive mode. This manual will be revised as necessary to reflect enhancements made to the system.

Tyron-Hopko, A.K.; Driscoll, K.L.

1985-10-01

405

Evaluation of Method for Counting Gross Radioactivity in Water  

Microsoft Academic Search

The detection and measurement of radioactivity in water is discussed ; with respect to the evaluation of methods for counting gross radioactivity. The ; results obtained when two samples of water containing a radioisotope were sent to ; various laboratories are presented. Approximately half the agencies were able to ; determine gross radioactivity within 10 to 15% of the true

J. W. Mullins; R. C. Kroner; D. G. Ballinger; H. P. Kramer

1961-01-01

406

Rapid screening of radioactivity in food for emergency response  

Microsoft Academic Search

This paper describes the development of methods for the rapid screening of gross alpha (GA) and gross beta (GB) radioactivity in liquid foods, specifically, Tang drink mix, apple juice, and milk, as well as screening of GA, GB, and gamma radioactivity from surface deposition on apples. Detailed procedures were developed for spiking of matrices with 241Am (alpha radioactivity), 90Sr\\/90Y (beta

A. Bari; A. J. Khan; T. M. Semkow; U.-F. Syed; A. Roselan; D. K. Haines; G. Roth; M. Arndt

2011-01-01

407

On the radioactivity of summer clouds on Mount Olympus  

Microsoft Academic Search

The radioactivity in different parts of a cloud as well as the radioactivity of the atmosphere before and after the cloud's passage are examined with stationary samplers --- fall-out pans, Grunow cloud-catchers of various materials, and air-pumps --- at elevations of 1800 m and 2817 m, on Mt Olympus --- Greece. The relation between the cloud's density and its radioactivity

Susan D. Danali

1969-01-01

408

On the radioactivity of summer clouds on Mount Olympus  

Microsoft Academic Search

The radioactivity in different parts of a cloud as well as the radioactivity of the atmosphere before and after the cloud's passage are examined with stationary samplers fall-out pans, Grunow cloud-catchers of various materials, and air-pumps at elevations of 1800 m and 2817 m, on Mt Olympus Greece. The relation between the cloud's density and its radioactivity

Susan D. Danali

1969-01-01

409

The importance of radioactivity in geoscience and mining  

Microsoft Academic Search

Almost simultaneously with Roentgen rays, natural radioactivity was discovered. Its investigation led to important fundamentals of the geosciences: petrophysics, terrestrial heat flow, isotope geology, and absolute geological chronology. In applied geophysics and geology, exploration of radioactive ores and of tectonic faults, and radiometric well loggings, are used. Production of radioactive water and mining for uranium ores are discussed, including their

H.-G. Reinhardt; H. Gast

1995-01-01

410

Stirring system for radioactive waste water storage tank  

Microsoft Academic Search

A stirring system for 100-m[sup 3] radioactive liquid waste tanks was constructed to unify radioactive concentrations in the tank. The stirring system is effective in certifying that the radioactive concentrations in the tanks are less than the legal limits before they are drained away as waste liquid. This system is composed of discharge units, pipe lines, and a controller. The

Yoshimune Ogata; Kunihide Nishizawa

1999-01-01

411

40 CFR 147.3005 - Radioactive waste injection wells.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Radioactive waste injection wells. 147.3005...Other New Mexico Tribes § 147.3005 Radioactive waste injection wells. Notwithstanding...operators of wells used to dispose of radioactive waste (as defined in 10 CFR part...

2013-07-01

412

10 CFR 76.81 - Authorized use of radioactive material.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Authorized use of radioactive material. 76.81 Section 76...Safety § 76.81 Authorized use of radioactive material. Unless otherwise authorized...shall confine its possession and use of radioactive material to the locations...

2013-01-01

413

49 CFR 172.436 - RADIOACTIVE WHITE-I label.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false RADIOACTIVE WHITE-I label. 172.436 Section...SECURITY PLANS Labeling § 172.436 RADIOACTIVE WHITE-I label. (a) Except for size and color, the RADIOACTIVE WHITE-I label must be as...

2011-10-01

414

49 CFR 172.436 - RADIOACTIVE WHITE-I label.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false RADIOACTIVE WHITE-I label. 172.436 Section...SECURITY PLANS Labeling § 172.436 RADIOACTIVE WHITE-I label. (a) Except for size and color, the RADIOACTIVE WHITE-I label must be as...

2012-10-01

415

40 CFR 227.30 - High-level radioactive waste.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false High-level radioactive waste. 227.30 Section 227.30 Protection... Definitions § 227.30 High-level radioactive waste. High-level radioactive waste means the aqueous waste resulting...

2013-07-01

416

49 CFR 172.440 - RADIOACTIVE YELLOW-III label.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false RADIOACTIVE YELLOW-III label. 172.440...PLANS Labeling § 172.440 RADIOACTIVE YELLOW-III label. (a) Except for size and color, the RADIOACTIVE YELLOW-III label must be as...

2012-10-01

417

49 CFR 172.440 - RADIOACTIVE YELLOW-III label.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false RADIOACTIVE YELLOW-III label. 172.440...PLANS Labeling § 172.440 RADIOACTIVE YELLOW-III label. (a) Except for size and color, the RADIOACTIVE YELLOW-III label must be as...

2011-10-01

418

Storing solid radioactive wastes at the Savannah River Plant  

Microsoft Academic Search

The facilities and the operation of solid radioactive waste storage at the Savannah River Plant (SRP) are discussed in the report. The procedures used to segregate and the methods used to store radioactive waste materials are described, and the monitoring results obtained from studies of the movement of radionuclides from buried wastes at SRP are summarized. The solid radioactive waste

J. H. Horton; J. C. Corey

1976-01-01

419

Transfer of Radioactive Materials from Living Cells to Fixed Cells  

Microsoft Academic Search

Transfer of radioactive materials to fixed cells from an overlying layer of living cells has been examined to determine whether fixed cells can act as acce'ptors of glycosyltransferases of living cells. After the incubation of living cells lying upon fixed cells along with radioactive precursor, the living cells were removed by EDTA treatment, and the radioactivity associated with the fixed

HISAKO SAKIYAMA; HIROSHI OTSU; SHIRO KANEGASAKI

420

Exploring solid state physics properties with radioactive isotopes  

Microsoft Academic Search

Radioactive atoms have been used in solid state physics for many years. Established nuclear techniques such as Mbauer spectroscopy, perturbed angular correlation, -NMR and emission channelling have now been joined by new and successful tracer techniques like radioactive deep level transient spectroscopy, capacitance voltage measurements, Hall-effect measurements or photoluminescence spectroscopy. Numerous radioactive species, ranging from to , are employed to

Doris Forkel-Wirth

1999-01-01

421

Beneficial role of conflict in radioactive waste management programs  

Microsoft Academic Search

Of the technical, political, and social problems associated with radioactive waste management, least is known about the latter two. Lay persons tend to generalize negative attitudes about other nuclear activity to radioactive waste management. Thus, conflict appears inevitable between the general public, citizen action groups, and decision-makers on radioactive waste management. The basis of conflict, we believe, can be found

B. A. Payne; R. G. Williams

1985-01-01

422

40 CFR 141.25 - Analytical methods for radioactivity.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Analytical methods for radioactivity. 141.25 Section 141.25 ...141.25 Analytical methods for radioactivity. (a) Analysis for the following...determine compliance with § 141.66 (radioactivity) in accordance with the...

2010-07-01

423

49 CFR 175.701 - Separation distance requirements for packages containing Class 7 (radioactive) materials in...  

Code of Federal Regulations, 2012 CFR

...requirements for packages containing Class 7 (radioactive) materials in passenger-carrying...requirements for packages containing Class 7 (radioactive) materials in passenger-carrying...passenger-carrying aircraft between Class 7 (radioactive) materials labeled RADIOACTIVE...

2012-10-01

424

10 CFR 61.41 - Protection of the general population from releases of radioactivity.  

Code of Federal Regulations, 2010 CFR

...general population from releases of radioactivity. 61.41 Section 61.41 Energy...general population from releases of radioactivity. Concentrations of radioactive...should be made to maintain releases of radioactivity in effluents to the general...

2009-01-01

425

10 CFR 61.41 - Protection of the general population from releases of radioactivity.  

Code of Federal Regulations, 2010 CFR

...general population from releases of radioactivity. 61.41 Section 61.41 Energy...general population from releases of radioactivity. Concentrations of radioactive...should be made to maintain releases of radioactivity in effluents to the general...

2010-01-01

426

Emissions of naturally occurring radioactivity: fireclay mine and refractory plant  

SciTech Connect

Atmospheric emissions of naturally occurring radioactivity were measured at a fireclay mine and the associated plant that produces refractory brick products. The only significant radioactive emission from the mine was radon-222. An analysis of the ore radioactivity and surface area of the mine indicated that the radon released is comparable to that from any similar surface area of similar radioactivity. The major particulate radioactivity from the refractory operation was polonium-210, released as the brick was fired. Approximately 26 percent of the polonium-210 in green brick was driven off in the kilns.

Andrews, V.E.

1981-02-01

427

Radioactive scrap metal decontamination technology assessment report  

SciTech Connect

Within the DOE complex there exists a tremendous quantity of radioactive scrap metal. As an example, it is estimated that within the gaseous diffusion plants there exists in excess of 700,000 tons of contaminated stainless steel. At present, valuable material is being disposed of when it could be converted into a high quality product. Liquid metal processing represents a true recycling opportunity for this material. By applying the primary production processes towards the material`s decontamination and re-use, the value of the strategic resource is maintained while drastically reducing the volume of material in need of burial. Potential processes for the liquid metal decontamination of radioactively contaminated metal are discussed and contrasted. Opportunities and technology development issues are identified and discussed. The processes compared are: surface decontamination; size reduction, packaging and burial; melting technologies; electric arc melting; plasma arc centrifugal treatment; air induction melting; vacuum induction melting; and vacuum induction melting and electroslag remelting.

Buckentin, J.M.; Damkroger, B.K.; Schlienger, M.E. [Sandia National Labs., Albuquerque, NM (United States). Liquid Metal Processing Lab.

1996-04-01

428

ELECTRONIC ANALOG COMPUTER FOR DETERMINING RADIOACTIVE DISINTEGRATION  

DOEpatents

A computer is presented for determining growth and decay curves for elements in a radioactive disintegration series wherein one unstable element decays to form a second unstable element or isotope, which in turn forms a third element, etc. The growth and decay curves of radioactive elements are simulated by the charge and discharge curves of a resistance-capacitance network. Several such networks having readily adjustable values are connected in series with an amplifier between each successive pair. The time constant of each of the various networks is set proportional to the half-life of a corresponding element in the series represented and the charge and discharge curves of each of the networks simulates the element growth and decay curve.

Robinson, H.P.

1959-07-14

429

A Novel Radioactive Isotope Ion Target SCRIT  

NASA Astrophysics Data System (ADS)

Electron scattering is a superior method to investigate the internal structure, such as charge distribution, of atomic nuclei. Most of the radii of nuclei were determined unambiguously by that. However, radioactive isotopes (RI) which recently came up to a major research interest have not been accessible due to the difficulty in making fixed targets and taking measurements before they decay. We proposed a conceptually new target called SCRIT (Self-Confining Radioactive Isotope ion Target) as opposed to a collider method. The luminosity expected for SCRIT is inevitably low (typically on the order of 1.E+27/cm2/s) and a large acceptance detector system is required. We plan to perform a coincidence measurement using an electron arm and a recoil ion detector which needs to be developed. Current status of the ion trapping with a prototype SCRIT and the background measurement results in an electron storage ring will be discussed.

Kurita, Kazuyoshi; Masuda, Tetsuya; Koseki, Tadashi; Noda, Akira; Shirai, Toshiyuki; Tongu, Hiromu; Furukawa, Yukihiro; Tamae, Tadaaki; Ito, Sachiko; Ohnishi, Tetsuya; Suda, Toshimi; Takeda, Hiroyuki; Wang, Shuo; Emoto, Takashi; Nakamura, Masato; Wakasugi, Masanori; Yano, Yasushige

2006-11-01

430

A simple description of cluster radioactivity  

NASA Astrophysics Data System (ADS)

The partial half-life of radioactive decay of nuclei by the emission of fragments heavier than the ?-particle, such as the emission of carbon, oxygen, neon, magnesium and silicon isotopes from trans-lead nuclei (known as cluster radioactivity), is re-evaluated in the framework of a semi-empirical, one-parameter model based on the quantum mechanical tunneling mechanism through a potential barrier where the Coulomb, centrifugal and overlapping contributions to the barrier are considered within the spherical nucleus approximation. This treatment has proven adequate not only to fit all the existing half-life data, but also to give more reliable half-life predictions for new, yet unmeasured cases of spontaneous emission of massive nuclear fragments from both heavy and intermediate-mass parent nuclei. In celebration of the 80th anniversary of the discovery of the neutron.

Tavares, O. A. P.; Medeiros, E. L.

2012-07-01

431

Two-proton radioactivity of 45Fe  

SciTech Connect

In an experiment at the SISSI-LISE3 facility of GANIL, the decay of the proton drip line nucleus 45Fe has been studied. Fragment-implantation events have been correlated with radioactive decay events in a 16x16 pixel silicon-strip detector. The decay-energy spectrum of 45Fe implants shows a distinct peak at (1.14+/-0.04) MeV with a half-life of T(1/2)=(4.7(+3.4)(-1.4)) ms. None of the events in this peak is in coincidence with beta particles. For a longer correlation interval, daughter decays of the two-proton daughter 43Cr can be observed after 45Fe implantation. The decay energy for 45Fe agrees nicely with several theoretical predictions for two-proton radioactivity.

Miernik, K. [University of Warsaw; Dominik, W. [University of Warsaw; Janas, Z. [University of Warsaw; Pfutzner, M. [University of Warsaw; Grigorenko, L. [Joint Institute for Nuclear Research, Dubna, Russia; Bingham, C. R. [University of Tennessee, Knoxville (UTK); Czyrkowski, H. [University of Warsaw; Cwiok, Mikolaj [Warsaw University; Darby, Iain [University of Tennessee, Knoxville (UTK); Dabrowski, Ryszard [Warsaw University; Ginter, T. N. [Michigan State University, East Lansing; Grzywacz, R. [University of Tennessee, Knoxville (UTK); Karny, M. [University of Warsaw; Korgul, A. [University of Warsaw; Kusmierz, W. [University of Warsaw; Liddick, Sean [University of Tennessee, Knoxville (UTK); Rajabali, Mustafa [University of Tennessee, Knoxville (UTK); Rykaczewski, Krzysztof Piotr [ORNL; Stolz, A. [Michigan State University, East Lansing

2009-01-01

432

Soluble pig for radioactive waste transfer lines  

SciTech Connect

Flushing transfer pipe after radioactive waste transfers generates thousands of gallons of additional radioactive waste each year at the Hanford site. The use of pneumatic pigging with waste soluble pigs as a means to clear transfer piping may be an effective alternative to raw water flushes. A feasibility study was performed by a group of senior mechanical engineering students for their senior design project as part of their curriculum at Washington State University. The students divided the feasibility study into three sub-projects involving: (1) materials research, (2) delivery system design, and (3) mockup fabrication and testing. The students screened through twenty-three candidate materials and selected a thermoplastic polymer combined 50:50 wt% with sucrose to meet the established material performance criteria. The students also prepared a conceptual design of a remote pneumatic delivery system and constructed a mockup section of transfer pipe for testing the prototype pigs.

Ohl, P.C., Westinghouse Hanford

1996-12-02

433

Radioactivity in bottled waters sold in Mexico.  

PubMed

Measurements of gross alpha and beta activities were made on 21 domestic and international brands of bottled (purified and mineral) water sold in the Mexican market to assess its radiological quality. Alpha and beta activities were determined using a liquid-scintillation detector with pulse-shape analysis feature. All the purified water had values of beta activity lower than the limit for potable drinking water (1.0 Bq/l), while three brands surpassed the limit of alpha activity (0.1 Bq/l). The limit for alpha radioactivity content was exceed by three mineral waters; the results show a correlation between radioactivity content and mineral salts, which are related with the origin and treatment of the waters. PMID:12102353

Dvila Rangel, J I; Lpez del Rio, H; Mireles Garca, F; Quirino Torres, L L; Villalba, M L; Colmenero Sujo, L; Montero Cabrera, M E

2002-06-01

434

Radioactive beam production at the Bevalac  

SciTech Connect

At the Bevalac radioactive beams are routinely produced by the fragmentation process. The effectiveness of this process with respect to the secondary beam's emittance, intensity and energy spread depends critically on the nuclear reaction kinematics and the magnitude of the incident beam energy. When this beam energy significantly exceeds the energies of the nuclear reaction process, many of the qualities of the incident beam can be passed on to the secondary beam. Factors affecting secondary beam quality are discussed along with techniques for isolating and purifying a specific reaction product. The on-going radioactive beam program at the Bevalac is used as an example with applications, present performance and plans for the future. 6 refs., 6 figs., 1 tab.

Alonso, J.R.; Feinberg, B.; Kalnins, J.G.; Krebs, G.F.; McMahan, M.A.; Tanihata, I.

1989-10-01

435

Radioactive hot cell access hole decontamination machine  

DOEpatents

Radioactive hot cell access hole decontamination machine. A mobile housing has an opening large enough to encircle the access hole and has a shielding door, with a door opening and closing mechanism, for uncovering and covering the opening. The housing contains a shaft which has an apparatus for rotating the shaft and a device for independently translating the shaft from the housing through the opening and access hole into the hot cell chamber. A properly sized cylindrical pig containing wire brushes and cloth or other disks, with an arrangement for releasably attaching it to the end of the shaft, circumferentially cleans the access hole wall of radioactive contamination and thereafter detaches from the shaft to fall into the hot cell chamber.

Simpson, William E. (Richland, WA)

1982-01-01

436

ORNL Radioactive Beams for Stellar Explosion Studies  

NASA Astrophysics Data System (ADS)

Thermonuclear reactions on unstable nuclei generate the energy that power nova explosions and X-ray bursts. In these explosions and others such as supernovae, these reactions serve to synthesize nuclei that (via their decay) can serve as tracers of the explosion mechanism. A powerful approach to improve our understanding of these explosions is to utilize beams of radioactive nuclei for direct and indirect measurements of these reactions. We are pursuing this approach at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL) to study reactions in the rp-process (with beams of 17,18F) and the r-process (with beams of 82Ge, 84Se 130,132Sn, 134Te). These measurements are combined with synergistic data evaluations and element synthesis calculations. Highlights of recent results are presented.

Smith, Michael S.

2008-05-01

437

Handbook of high-level radioactive waste transportation  

SciTech Connect

The High-Level Radioactive Waste Transportation Handbook serves as a reference to which state officials and members of the general public may turn for information on radioactive waste transportation and on the federal government`s system for transporting this waste under the Civilian Radioactive Waste Management Program. The Handbook condenses and updates information contained in the Midwestern High-Level Radioactive Waste Transportation Primer. It is intended primarily to assist legislators who, in the future, may be called upon to enact legislation pertaining to the transportation of radioactive waste through their jurisdictions. The Handbook is divided into two sections. The first section places the federal government`s program for transporting radioactive waste in context. It provides background information on nuclear waste production in the United States and traces the emergence of federal policy for disposing of radioactive waste. The second section covers the history of radioactive waste transportation; summarizes major pieces of legislation pertaining to the transportation of radioactive waste; and provides an overview of the radioactive waste transportation program developed by the US Department of Energy (DOE). To supplement this information, a summary of pertinent federal and state legislation and a glossary of terms are included as appendices, as is a list of publications produced by the Midwestern Office of The Council of State Governments (CSG-MW) as part of the Midwestern High-Level Radioactive Waste Transportation Project.

Sattler, L.R.

1992-10-01

438

Studies with Exotic Nuclei: Two Proton Radioactivity  

SciTech Connect

In the present paper, we present measurements that led to the discovery of two-proton radioactivity. After the first observation of this decay mode for {sup 45}Fe, new measurements evidenced this decay mode also for {sup 54}Zn and most likely {sup 48}Ni. A new detector based on the time-projection chamber principle allowed now to visualize the two protons directly.

Borcea, C.; Blank, B.; Canchel, G.; Demonchy, C. E.; Giovinazzo, J.; Hay, L.; Huikari, J.; Leblanc, S.; Matea, I.; Pedroza, J.-L.; Pibernat, J.; Serani, L. [Centre d'etudes nucleaires de Bordeaux-Gradignan, Universite Bordeaux 1-UMR 5797 CNRS/IN2P3, Chemin du Solarium, BP 120, F-33175 Gradignan Cedex (France); Oliveira Santos, F. de; Grevy, S.; Perrot, L.; Stodel, C.; Thomas, J.-C. [Grand Accelerateur National d'Ions Lourds, CEA/DSM-CNRS/IN2P3, Bvd Henri Becquerel, BP 55027, F-14076 CAEN Cedex 5 (France); Dossat, C. [DAPNIA, CEA Saclay, F-91191 Gif-sur-Yvette Cedex (France)

2008-01-24

439

Radioactive-ion-beam research at Livermore  

NASA Astrophysics Data System (ADS)

The ability to produce secondary radioactive heavy ion beams which can be isolated, focused, and transported to a secondary target can enable reaction studies and other research with the approximately more than 1300 nuclei with decay lifetimes approximately more than 1 microsec. Current research in secondary beam production and future applications in astrophysics, nuclear structure, heavy ion physics, and radiotherapy are examined as well as associated spin off and technology transfer in applied physics.

Haight, R. C.; Mathews, G. J.; Ward, R. A.; Woosley, S. E.

1983-06-01

440

A review of edible mushroom radioactivity  

Microsoft Academic Search

The review deals mainly with the situation in Europe where wild-growing mushrooms are widely consumed as a delicacy and some species have been found to be extensively contaminated by radioactive fallout from the Chernobyl disaster in 1986. The natural isotope 40K usually causes activities of 0.81.5 kBq kg?1 dry matter. Activities of 137Cs, from nuclear weapons testing, below 1 kBq

Pavel Kala?

2001-01-01

441

THE CURRENT RADIOACTIVE WASTE MANAGEMENT IN ROMANIA  

Microsoft Academic Search

In 1957, Romania commissioned a Russian-designed VVR-S research reactor used for scientific activities and radioisotope production. This reactor is now planned for decommissioning. An American TRIGA -type research reactor has been in use since 1978. The first Canadian CANDU-6 type power reactor was commissioned in December 1996 and is in commercial operation. The radioactive waste management in Romania followed decentralized

V. Andrei; F. Glodeanu; I. Rotaru; T. Chirica

2000-01-01

442

Progress of radioactive waste management in Lithuania  

Microsoft Academic Search

The only one nuclear power plant in the Republic of Lithuania Ignalina Nuclear Power Plant contains two RBMK-1500 water-cooled graphite-moderated channel-type power reactors. The first and the second reactors were shut down by the end of 2004 and by the end of 2009, respectively. During operation, the power plant has accumulated large quantities of radioactive waste, including spent nuclear

P. Poskas; J. E. Adomaitis; V. Ragaisis; V. Simonis; A. Smaizys; R. Kilda; D. Grigaliuniene

443

Fabrication of radioactive stents by ion implantation  

NASA Astrophysics Data System (ADS)

Worldwide about one million patients require treatment of stenosed coronary arteries annually. Often a tubular stainless steel mesh (stent) is implanted to mechanically support the injured vessel. Restenosis, an abundant complication (20%-30%) can be prevented, if the vessel is treated with ionizing radiation. Stents can deliver radiation if they are made radioactive. The radio isotope 32P is well suited when ion implanted. Radioactive ions sources require high efficiency to keep the radioactive inventory small. Reliability, ease of operation, and maintenance are mandatory. A small emittance is important to minimize losses during mass separation and beam transport. A 2.45 GHz ECR source was developed for the implantation of 32P. The source consists of two coils for the axial and a permanent hexapole for the radial confinement. The microwaves are fed in radially by a loop connected to a silver plated brass tube surrounding the plasma chamber. The plasma chamber is made from Pyrex. Neutron activated phosphorus, containing 30 ppm 32P, is introduced from the rear end on a rod. As support gas D2 is used. By this 32P+ can be separated from (31PD)+. The extraction is done in two steps: 60 kV-30 kV-ground. Mass separation is accomplished by a double focusing 90 magnet (radius 500 mm). During four years of operation about 1000 radioactive stents per year have been provided for animal experiments and clinical trials. Only one maintenance to exchange the extraction system due to degradation of high voltage stability was required so far.

Huttel, Erhard; Kaltenbaek, Johann; Schloesser, Klaus; Schweickert, Hermann

2002-02-01

444

Radioactive contamination of the Yenisei River  

Microsoft Academic Search

Based on observational data in the period 19711993, radioactive contamination of the Yenisei River ecosystem was analysed within 2000 km of the site of discharges from the Krasnoyarsk Mining and Chemical Industrial Complex. Data on the content of 24Na, 32P, 46Sc, 51Cr, 54Mn, 56Mn, 58Co, 60Co, 59Fe, 65Zn, 90Sr, 95Zr, 95Nb, 103Ru, 106Ru, 134Cs, 137Cs, 140Ba, 141Ce, 144Ce and 239Np

E. G. Tertyshnik

1995-01-01

445

Electrically Driven Technologies for Radioactive Aerosol Abatement  

SciTech Connect

The purpose of this research project was to develop an improved understanding of how electriexecy driven processes, including electrocoalescence, acoustic agglomeration, and electric filtration, may be employed to efficiently treat problems caused by the formation of aerosols during DOE waste treatment operations. The production of aerosols during treatment and retrieval operations in radioactive waste tanks and during thermal treatment operations such as calcination presents a significant problem of cost, worker exposure, potential for release, and increased waste volume.

David W. DePaoli; Ofodike A. Ezekoye; Costas Tsouris; Valmor F. de Almeida

2003-01-28

446

Radioactive beam facilities of North America  

Microsoft Academic Search

There are several nuclear physics laboratories in North America that have on-going research using energetic and stopped radioactive beams. These include the large ISOL-based programs ISAC at TRIUMF in Canada and HRIBF at Oak Ridge and the in-flight fragmentation program at the NSCL of Michigan State University. There are also smaller, more specialized, programs using a variety of techniques at

J. A. Nolen

2004-01-01

447

Flow of radioactive fluids in porous media  

Microsoft Academic Search

Radioactive tracers, in particular, tritium (HU3D), are finding ever-increasing applications in hydrological and oil reservoir studies. Tritium is a convenient, easy- to-handle, and inexpensive tracer for use in fluid injection operations. However, its low energy emissions and possible adsorption on porous media may detract from its desirable characteristics. The present investigation was designed to study the qualitative and quantitative flow

P. J. Bolivar; S. M. Farouq Ali

1967-01-01

448

Procedures for radioactive I-125 seed implants  

SciTech Connect

Typical safety procedures and guidelines for the use of radioactive I-125 seed implant are presented. Topics covered include: Physical properties, management and planning of I-125, source logging, source transportation, source accounting during and after implant, room monitoring, recording, dosimetry films, nursing procedures, discharge of patient. These guidelines have been found to be of practical value for personnel involved with the implant to ensure compliance with the regulations, but are not necessarily the only procedures that could be utilized.

Sharma, S.C. (Univ. of Louisville, KY (USA))

1988-12-01

449

Summary of radioactive materials package stowage  

SciTech Connect

A tiedown system is necessary to attach a package of radioactive materials to a transport vehicle, be it a truck trailer, railcar, or barge. National and international tiedown regulations are summarized and discussed in this paper. Experimental and analytical evaluations of tiedown loads and responses also are summarized, with particular emphasis on a joint French/Belgian program examining cask and tiedown responses under accident conditions. 14 refs., 9 figs., 2 tabs.

Gonzales, A.

1988-06-01

450

Radioactive Ion Beams at INFN Laboratories  

SciTech Connect

The LNS and the LNL are the two laboratories of INFN devoted to the research on nuclear physics. Since the 1995 the LNS are involved in the design and construction of the Radioactive Ion Beam facilities called EXCYT. In the early of 2000 the LNL starts a project for second generation RIB facilities called SPES. In the 2004 at the LNS we start also the production of RIB by in flight fragmentation. Here the status and perspective of these three projects are presented.

Calabretta, L.; Celona, L.; Chines, F.; Cosentino, L.; Cuttone, G.; Finocchiaro, P.; Maggiore, M.; Pappalardo, A.; Piazza, L.; Re, M.; Rifuggiato, D.; Rovelli, A.; Pappalardo, A. [INFN Laboratori Nazionali del Sud, Via S. Sofia 62, 95123 Catania (Italy); Andrighetto, A.; Prete, G.; Biasetto, L.; Manzolaro, M.; Sarchiapone, L.; Galata, A.; Lombardi, A. [INFN Laboratori Nazionali di Legnaro, Via Romea 6, 35020 Legnaro (Italy)

2010-04-30

451

Non-radioactive in situ hybridization  

Microsoft Academic Search

A number of immunocytochemical detection systems for determining the chromosomal localization of specific nucleic acid sequences by non-radioactive in situ hybridization have been compared. The procedures were: 1. the peroxidase\\/diaminobenzidine (PO\\/DAB) combination, either or not gold\\/silver intensificated; 2. alkaline phosphatase marking using the nitro-blue tetrazolium plus bromochloro-indolyl phosphate substrate combination (AP\\/NBT+CIP); and 3. immunogold with or without silver enhancement. The

A. F. M. Cremers; N. Jansen in de Wal; J. Wiegant; R. W. Dirks; P. Weisbeek; M. Ploeg; J. E. Landegent

1987-01-01

452

Radioactivity in the industrial effluent disposed soil  

NASA Astrophysics Data System (ADS)

Studies on radiation and radioactivity distribution in the soils of effluent disposed from the sugar industry in India have been conducted. The external gamma dose rates in air and natural radionuclides activities in the soils were measured using an Environmental Radiation Dosimeter and a Gamma-ray Spectrometer respectively. The soil samples were also subject to various physico-chemical analyses. This study revealed some remarkable results that are discussed in the article.

Senthilkumar, R. D.; Narayanaswamy, R.; Meenashisundaram, V.

2012-04-01

453

Improvements in detergency precision with radioactive soil  

Microsoft Academic Search

Recent work on the use of seven-component, doubly labeled radioactive soil to evaluate deter-gency has depended on the analyses\\u000a of the fabric for residual soil. Because of the variation of soil concentration within and between fabric swatches, considerable\\u000a replication was required to lower the standard deviations to ?10%. A method for the analysis of wash water has been developed\\u000a which

W. T. Shebs; B. E. Gordon

1968-01-01

454

Energetic protons induced radioactivity in space detectors  

Microsoft Academic Search

Induced radioactivity in space detectors was simulated by bombarding protons of 1.2GeV and 1.7GeV on several CsI and CdTe crystals. Product nuclides were measured and identified by gamma ray spectroscopy and we have quantified the gamma-ray and 511keV gamma-ray emissions from the mainly identified isotopes, and the production yield of the long lived activation products.

J. L. Ferrero; C. Roldan; F. Ballester; E. Navarro; Y. Schutz; G. Martinez; B. Cordier; J. P. Leray; F. Albernhe; V. Borrel

1996-01-01

455

Criteria for onsite transfers of radioactive material  

SciTech Connect

A general description of the requirements for making onsite transfers of radioactive material is provided in Chapter 2, along with the required sequencey of activities. Various criteria for package use are identified in Chapters 3-13. These criteria provide protection against undue radiation exposure. Package shielding, containment, and surface contamination requirements are established. Criteria for providing criticality safety are enumerated in Chapter 6. Criteria for providing hazards information are established in Chapter 13. A glossary is provided.

Opperman, E.K.; Jackson, E.J.; Eggers, A.G.

1992-12-31

456

Performance assessment of radioactive waste repositories  

Microsoft Academic Search

The current plans for permanent disposal of radioactive waste call for its emplacement in deep underground repositories mined from geologically stable rock formations. The U.S. Nuclear Regulatory Commission and U.S. Environmental Protection Agency have established regulations setting repository performance standards for periods of up to 10,000 years after disposal. Compliance with these regulations will be based on a performance assessment

J. E. Campbell; R. M. Cranwell

1988-01-01

457

Radioactive isotopes in solid state physics  

Microsoft Academic Search

A wide range of solid state physics techniques is using radioactive ion beams, both from on-line and off-line separators. The different techniques can be roughly subdivided into two classes: one, including the hyperfine techniques like Mbauer spectroscopy (MS), Perturbed Angular Correlation (PAC) spectroscopy, ?-NMR and the ion-beam technique of Emission Channeling (EC). They all crucially depend on the availability of

Doris Forkel-Wirth

1997-01-01

458

Radioactive isotopes in solid state physics  

Microsoft Academic Search

A wide range of solid state physics techniques is using radioactive ion beams, both from on-line and off-line separators. The different techniques can be roughly subdivided into two classes: one, including the hyperfine techniques like Mbauer spectroscopy (MS), Perturbed Angular Correlation (PAC) spectroscopy, beta-NMR and the ion-beam technique of Emission Channeling (EC). They all crucially depend on the availability of

D. Forkel-Wirth

1996-01-01

459

Radioactive Particles Released from Different Nuclear Sources  

Microsoft Academic Search

Following releases from severe nuclear events such as nuclear weapon tests, use of depleted uranium ammunition and reactor\\u000a explosions or fire, a major fraction of refractory radionuclides such as uranium (U) and plutonium (Pu) is present as particles,\\u000a often ranging from submicrons to fragments. Radioactive particles and colloids are also released via effluents from reprocessing\\u000a facilities and civil reactors, and

Brit Salbu

460

Specific radioactivity of potassium in sea water  

SciTech Connect

The authors check the validity of the assumption concerning the constancy of A /SUB K/ in seawater. Accurate methods have been developed for determining the radioactivity of K-40 and the over-all potassium percentage in seawater samples. 14 samples were taken in the Pacific Ocean. The authors found that A /SUB K/ can be used as an indicator of elevated concentrations in large bodies of water of both extraterrestrial and volcanic matter.

Sapozhnikov, Y.A.; Merkushov, A.V.

1986-02-01

461

Two-proton radioactivity of 45Fe  

NASA Astrophysics Data System (ADS)

The decay of the extremely neutron-deficient isotope 45Fe has been studied by using a new type of gaseous detector in which a technique of optical imaging is used to record tracks of charged particles. The two-proton radioactivity and the ? -decay channels were clearly identified. For the first time, the angular and energy correlations between two protons emitted from the 45Fe ground state were measured. The obtained results were confronted with predictions of a three-body model.

Miernik, K.; Dominik, W.; Janas, Z.; Pftzner, M.; Grigorenko, L.; Bingham, C.; Czyrkowski, H.; ?wiok, M.; Darby, I. G.; D?browski, R.; Ginter, T.; Grzywacz, R.; Karny, M.; Korgul, A.; Ku?mierz, W.; Liddick, S. N.; Rajabali, M.; Rykaczewski, K.; Stolz, A.

2009-12-01

462

Procedures for radioactive I-125 seed implants.  

PubMed

Typical safety procedures and guidelines for the use of radioactive I-125 seed implant are presented. Topics covered include: Physical properties, management and planning of I-125, source logging, source transportation, source accounting during and after implant, room monitoring, recording, dosimetry films, nursing procedures, discharge of patient. These guidelines have been found to be of practical value for personnel involved with the implant to ensure compliance with the regulations, but are not necessarily the only procedures that could be utilized. PMID:3252898

Sharma, S C

1988-12-01

463

Novel techniques to search for neutron radioactivity  

NASA Astrophysics Data System (ADS)

Two new methods to observe neutron radioactivity are presented. Both methods rely on the production and decay of the parent nucleus in flight. The relative velocity measured between the neutron and the fragment is sensitive to half-lives between 1 and 100ps for the Decay in Target (DiT) method. The transverse position measurement of the neutron in the Decay in a Magnetic Field (DiMF) method is sensitive to half-lives between 10 ps and 1 ns.

Thoennessen, M.; Christian, G.; Kohley, Z.; Baumann, T.; Jones, M.; Smith, J. K.; Snyder, J.; Spyrou, A.

2013-11-01

464

Sargent Curves for Artificilly Radioactive Substances  

Microsoft Academic Search

Sargent curves have been plotted for a number of elements whose end-points have been determined by extrapolation of the Konopinski-Uhlenbeck curves. The points lie on three smooth curves whose shapes agree with theoretical calculations based on the K-U theory. The relative values for the transition matrix moments are obtained and a discussion of the spins of the radioactive elements is

Allan C. Mitchell

1937-01-01

465

PROCESS OF DECONTAMINATING MATERIAL CONTAMINATED WITH RADIOACTIVITY  

DOEpatents

A process is described for decontaminating metallic objects, such as stainless steel equipment, which consists in contacting such objects with nltric acid in a concentration of 35 to 60% to remove the major portion of the contamination; and thereafter contacting the partially decontaminated object with a second solution containing up to 20% of alkali metal hydroxide and up to 20% sodium tartrate to remove the remaining radioactive contaminats.

Overholt, D.C.; Peterson, M.D.; Acken, M.F.

1958-09-16

466

Discovery of oxygen radioactivity of atomic nuclei  

Microsoft Academic Search

By using solid-state nuclear track detectors arranged in 2pi geometry we collected 27 events due to the radioactive decay of 228Th by 20O emission. The partial half-life is (5.29 +\\/- 1.01) 1020 s and the branching ratio relative to alpha decay is (1.13 +\\/- 0.22) 10-13. This is the first case of observation of spontaneous emission of oxygen

R. Bonetti; C. Chiesa; A. Guglielmetti; C. Migliorino; A. Cesana; M. Terrani

1993-01-01

467

Radioactive waste management in the former USSR  

SciTech Connect

Radioactive waste materials--and the methods being used to treat, process, store, transport, and dispose of them--have come under increased scrutiny over last decade, both nationally and internationally. Nuclear waste practices in the former Soviet Union, arguably the world's largest nuclear waste management system, are of obvious interest and may affect practices in other countries. In addition, poor waste management practices are causing increasing technical, political, and economic problems for the Soviet Union, and this will undoubtedly influence future strategies. this report was prepared as part of a continuing effort to gain a better understanding of the radioactive waste management program in the former Soviet Union. the scope of this study covers all publicly known radioactive waste management activities in the former Soviet Union as of April 1992, and is based on a review of a wide variety of literature sources, including documents, meeting presentations, and data base searches of worldwide press releases. The study focuses primarily on nuclear waste management activities in the former Soviet Union, but relevant background information on nuclear reactors is also provided in appendixes.

Bradley, D.J.

1992-06-01

468

Radioactive Waste Burial Grounds. Environmental Information Document  

SciTech Connect

This document provides environmental information on postulated closure options for the Radioactive Waste Burial Grounds at the Savannah River Plant and was developed as background technical documentation for the Department of Energy`s proposed Environmental Impact Statement (EIS) on waste management activities for groundwater protection at the plant. The results of groundwater and atmospheric pathway analyses, accident analysis, and other environmental assessments discussed in this document are based upon a conservative analysis of all foreseeable scenarios as defined by the National Environmental Policy Act (CFR, 1986). The scenarios do not necessarily represent actual environmental conditions. This document is not meant to be used as a closure plan or other regulatory document to comply with required federal or state environmental regulations. The closure options considered for the Radioactive Waste Burial Grounds are waste removal and closure, no waste removal and closure, and no action. The predominant pathways for human exposure to chemical and/or radioactive constituents are through surface, subsurface, and atmospheric transport. Modeling calculations were made to determine the risks to human population via these general pathways for the three postulated closure options. An ecological assessment was conducted to predict the environmental impacts on aquatic and terrestrial biota. The relative costs for each of the closure options were estimated.

Jaegge, W.J.; Kolb, N.L.; Looney, B.B.; Marine, I.W.; Towler, O.A.; Cook, J.R.

1987-03-01

469

Sources of Radioactive Isotopes for Dirty Bombs  

NASA Astrophysics Data System (ADS)

From the security perspective, radioisotopes and radioactive sources are not created equal. Of the many radioisotopes used in industrial applications, medical treatments, and scientific research, only eight, when present in relatively large amounts in radioactive sources, pose high security risks primarily because of their prevalence and physical properties. These isotopes are americium-241, californium-252, cesium-137, cobalt-60, iridium-192, radium-226, plutonium-238, and strontium-90. Except for the naturally occurring radium-226, nuclear reactors produce the other seven in bulk commercial quantities. Half of these isotopes emit alpha radiation and would, thus, primarily pose internal threats to health; the others are mainly high-energy gamma emitters and would present both external and internal health hazards. Therefore, the response to a "dirty bomb" event depends on what type of radioisotope is chosen and how it is employed. While only a handful of major corporations produce the reactor-generated radioisotopes, they market these materials to thousands of smaller companies and users throughout the world. Improving the security of the high-risk radioactive sources will require, among other efforts, cooperation among source suppliers and regulatory agencies.

Lubenau, Joel

2004-05-01

470

BEARS: Radioactive ion beams at LBNL  

SciTech Connect

BEARS (Berkeley Experiments with Accelerated Radioactive Species) is an initiative to develop a radioactive ion-beam capability at Lawrence Berkeley National Laboratory. The aim is to produce isotopes at an existing medical cyclotron and to accelerate them at the 88 inch Cyclotron. To overcome the 300-meter physical separation of these two accelerators, a carrier-gas transport system will be used. At the terminus of the capillary, the carrier gas will be separated and the isotopes will be injected into the 88 inch Cyclotron`s Electron Cyclotron Resonance (ECR) ion source. The first radioactive beams to be developed will include 20-min {sup 11}C and 70-sec {sup 14}O, produced by (p,n) and (p,{alpha}) reactions on low-Z targets. A test program is currently being conducted at the 88 inch Cyclotron to develop the parts of the BEARS system. Preliminary results of these tests lead to projections of initial {sup 11}C beams of up to 2.5 {times} 10{sup 7} ions/sec and {sup 14}O beams of 3 {times} 10{sup 5} ions/sec.

Powell, J.; Guo, F.Q. [Lawrence Berkeley National Lab., CA (United States); Haustein, P.E. [Brookhaven National Lab., Upton, NY (United States). Chemistry Dept.] [and others

1998-07-01

471

Radioactive iodine therapy in cats with hyperthyroidism  

SciTech Connect

Eleven cats with hyperthyroidism were treated with radioactive iodine (/sup 131/I). Previous unsuccessful treatments for hyperthyroidism included hemithyroidectomy (2 cats) and an antithyroid drug (7 cats). Two cats had no prior treatment. Thyroid scans, using technetium 99m, showed enlargement and increased radionuclide accumulation in 1 thyroid lobe in 5 cats and in both lobes in 6 cats. Serum thyroxine concentrations were high and ranged from 4.7 to 18 micrograms/dl. Radioactive iodine tracer studies were used to determine peak radioactive iodine uptake (RAIU) and effective and biological half-lives. Activity of /sup 131/I administered was calculated from peak RAIU, effective half-life, and estimated thyroid gland weight. Activity of /sup 131/I administered ranged from 1.0 to 5.9 mCi. The treatment goal was to deliver 20,000 rad to hyperactive thyroid tissue. However, retrospective calculations based on peak RAIU and effective half-life obtained during the treatment period showed that radiation doses actually ranged from 7,100 to 64,900 rad. Complete ablation of the hyperfunctioning thyroid tissue and a return to euthyroidism were seen in 7 cats. Partial responses were seen in 2 cats, and 2 cats became hypothyroid. It was concluded that /sup 131/I ablation of thyroid tumors was a reasonable alternative in the treatment of hyperthyroidism in cats. The optimal method of dosimetry remains to be determined.

Turrel, J.M.; Feldman, E.C.; Hays, M.; Hornof, W.J.

1984-03-01

472

Packaging and transportation of radioactively contaminated lead  

SciTech Connect

Under the management of the Nuclear Decommissioning Authority (NDA) the government of the United Kingdom has launched an ambitious program to remediate the nation's nuclear waste legacy. Over a twenty-five year period NDA plans to decommission several first generation nuclear power plants and other radioactive facilities. The use innovative, safe 'fit for purpose' technologies will be a major part of this complex program. This paper will present a case study of a recently completed project undertaken in support of the nuclear decommissioning activities at the Sellafield site in the United Kingdom. The focus is on an innovative application of new packaging technology developed for the safe transportation of radioactively contaminated lead objects. Several companies collaborated on the project and contributed to its safe and successful conclusion. These companies include British Nuclear Group, Gravatom Engineering, W. F. Bowker Transport, Atlantic Container Lines, MHF Logistical Solutions and Energy Solutions. New containers and a new innovative inter-modal packaging system to transport the radioactive lead were developed and demonstrated during the project. The project also demonstrated the potential contribution of international nuclear recycling activities as a safe, economic and feasible technical option for nuclear decommissioning in the United Kingdom. (authors)

Gleason, Eugene [MHF Logistical Solutions, UK, Limited (United Kingdom); Holden, Gerard [Gravatom Engineering Limited (United Kingdom)

2007-07-01

473

[Working environment measurement of radioactive substances].  

PubMed

The control of the working environment is one of the most important duties in any working place to prevent occupational disease. In Japan, in the case of the controlled area using unsealed radioisotopes, the measurement of the concentration of airborne radioactive substances should be carried out under the regulations of the "Industrial Safety and Health Law" and the "Ordinance on Prevention of Ionizing Radiation Hazards". Many reports showed that the results of regular working environment measurements of radioactive substances were about background levels. Safe working environments are sufficiently guaranteed by a suitable estimation and handling under the strict regulation by the "Laws Concerning the Prevention from Radiation Hazards Due to Radioisotopes and Others". The regulation by "Ordinance on Prevention of Ionizing Radiation Hazards" would be relaxed in the field of education and research, which use very low quantities of radioactive substances, in ways such as estimation by calculation in place of the actual measurement, decrease of the number of monthly measurements, and measurement exemption for low levels of isotopes. PMID:18170964

Kunugita, Naoki

2007-12-01

474

Soils: man-caused radioactivity and radiation forecast  

SciTech Connect

Available in abstract form only. Full text of publication follows: One of the main tasks of the radiation safety guarantee is non-admission of the excess over critical radiation levels. In Russia they are man-caused radiation levels. Meanwhile any radiation measurement represents total radioactivity. That is why it is hard to assess natural and man-caused contributions to total radioactivity. It is shown that soil radioactivity depends on natural factors including radioactivity of rocks and cosmic radiation as well as man-caused factors including nuclear and non-nuclear technologies. Whole totality of these factors includes unpredictable (non-deterministic) factors - nuclear explosions and radiation accidents, and predictable ones (deterministic) - all the rest. Deterministic factors represent background radioactivity whose trends is the base of the radiation forecast. Non-deterministic factors represent man-caused radiation treatment contribution which is to be controlled. This contribution is equal to the difference in measured radioactivity and radiation background. The way of calculation of background radioactivity is proposed. Contemporary soils are complicated technologically influenced systems with multi-leveled spatial and temporary inhomogeneity of radionuclides distribution. Generally analysis area can be characterized by any set of factors of soil radioactivity including natural and man-caused factors. Natural factors are cosmic radiation and radioactivity of rocks. Man-caused factors are shown on Fig. 1. It is obvious that man-caused radioactivity is due to both artificial and natural emitters. Any result of radiation measurement represents total radioactivity i.e. the sum of activities resulting from natural and man-caused emitters. There is no gauge which could separately measure natural and man-caused radioactivity. That is why it is so hard to assess natural and man-caused contributions to soil radioactivity. It would have been possible if human activity had led to contamination of soil only by artificial radionuc