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1

The use of TLD-700H dosemeters in the assessment of external doses at the former Semipalatinsk nuclear test site.  

PubMed

The joint projects performed since 1995 by the Jülich Research Centre in co-operation with the Kazakh National Nuclear Centre in the area of the former nuclear test site near Semipalatinsk, in eastern Kazakhstan, have assessed the current dose rate of the population at and around the test site, as well as determining retrospectively the dose rate of persons affected by the atmospheric tests. Measurements of the population by personal dosemeters depend on reliably wearing these dosemeters over prolonged periods of time, and of a sufficient dosemeter return. In the past, such measurements have been particularly successful whenever short wearing times were possible. This requires high sensitivity of the dosemeters. The suitability of the highly sensitive TLD material of the BICRON TLD 700H type for such personal dosimetry measurements was investigated. It was tested in practical field application at the Semipalatinsk nuclear test site in September 2000. Initial results are available from individual doses received by a group of geologists and a group of herdsmen at the test site. For the first time, the individual dose was measured directly in these population groups. Detection limits below 1 microSv permit informative measurements for wearing times of less than two weeks. Most individual doses did not arise significantly out of local fluctuations of natural background. A conservative assessment from the aspect of practical health physics yielded a mean personal dose of 0.55 microSv per day for the herdsmen, whereas the geologists received a mean personal dose of 0.45 microSv per day. For an annual exposure period of typically, about three months, the radiation dose received by the persons investigated, in addition to the natural radiation exposure, is thus well below the international limit value of 1 mSv x a(-1) for the population dose. PMID:12382756

Hill, P; Dederichs, H; Pillath, J; Schlecht, W; Hille, R; Artemev, O; Ptitskaya, L; Akhmetov, M

2002-01-01

2

Pre-irradiation and post-irradiation fading of the Harshaw 8841 TLD in different environmental conditions.  

PubMed

The pre-irradiation and post-irradiation fading of a commercially available LiF:Mg,Cu,P thermoluminescent detector (TLD)-the Harshaw 8841 TLD-have been assessed. The Harshaw 8841 TLD comprises three TLD-700H chips (99.7% 7LiF and 0.03% 6LiF by weight) and one TLD-600H chip (4.4% 7LiF and 95.6% 6LiF by weight). Pre-irradiation and post-irradiation fading were measured for storage times up to 164 d and three different storage temperatures (-8, 25 and 50 degrees C). Dosemeters were irradiated in a mixed photon-neutron field so that the fading behaviour of the photon and neutron signals could be studied. The TLD-700H and TLD-600H chips exhibited complex changes in sensitivity and signal that depended on storage time, storage temperature and the type of radiation to which the chips had been exposed. However, the magnitudes of these changes in sensitivity and signal were relatively small. TLD-600H and TLD-700H, therefore, exhibit good stability of sensitivity and signal. PMID:17008363

Jones, L A; Stokes, R P

2006-09-28

3

Evaluating two extremity dosemeters based on LiF:Mg,Ti or LiF:Mg,Cu,P.  

PubMed

Evaluation of a new extremity dosemeter is presented. The dosemeter is a passive device that is easy to wear and features a permanent individual numerical ID with barcode, a watertight case, an automatic TLD reader and database management software. Two dosemeters were studied: the first consists of a 100 mg x cm(-2) 7LiF:Mg,Ti (TLD-700) chip and a 42 mg x cm(-2) cap, the other consists of a 7 mg x cm(-2) layer of 7LiF:Mg,Cu,P (TLD-700H) powder and a 5 mg x cm(-2) cap. Sensitivity, repeatability, lower limit detection, angular responses and energy responses for these dosemeters are studied and presented. The dose calculation algorithm is developed and its dosimetric performance accuracy is compared with the standard ANSI N13.32-1995, Performance Testing of Extremity Dosemeters. PMID:12382737

Luo, L Z; Velbeck, K J; Rotunda, J E

2002-01-01

4

Optimization of the Readout Procedures for the Harshaw 8800 TL (Thermoluminescent) Dosimetry System.  

National Technical Information Service (NTIS)

The optimization of the readout procedures for Harshaw's LiF-TLDs and it 8800 automatic TLD reader were studied. The optimization was based on the TLD sensitivity stability during 8-10 recycling uses. Three types of TLDs under several exposure conditions ...

C. Liu C. S. Sims T. A. Rhea

1989-01-01

5

Glass as a gamma Ray Dosemeter.  

National Technical Information Service (NTIS)

The advantages of glass as a gamma -rays dosemeter are studied. Experiments have shown that ordinary microscope object glass can be used as a dosemeter, which dose range for linear response extends from about 10 exp 4 -10 exp 6 rads. Heat treatment of the...

Sutrisno Puspodikoro

1978-01-01

6

State of the Art in Electronic Dosemeters for Neutrons  

SciTech Connect

The paper presents an overview of electronic personal dosemeters for neutrons in mixed neutron/photon fields. The energy response of commercially available electronic dosemeters in quasi-monoenergetic neutron fields and their performance in working places is discussed. The response curves are extended to high-energy neutrons up to 100 MeV, new prototype dosemeters are described and discussed especially for use at high-energy accelerators and in space.

Luszik-Bhadra, Marlies [Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig (Germany)

2011-05-05

7

State of the Art in Electronic Dosemeters for Neutrons  

NASA Astrophysics Data System (ADS)

The paper presents an overview of electronic personal dosemeters for neutrons in mixed neutron/photon fields. The energy response of commercially available electronic dosemeters in quasi-monoenergetic neutron fields and their performance in working places is discussed. The response curves are extended to high-energy neutrons up to 100 MeV, new prototype dosemeters are described and discussed especially for use at high-energy accelerators and in space.

Luszik-Bhadra, Marlies

2011-05-01

8

Operational experience of electronic active personal dosemeter and comparison with CaSo4:Dy TL dosemeter in Indian PHWR.  

PubMed

Direct reading dosemeter has been used for day-to-day radiation exposure control and management for last four decades in Indian nuclear power plants (NPPs). Recently new real time, alarm and pre-alarm on equivalent dose/dose rate, storage of dose/dose rate and maximum dose rate, user-friendly electronic active personal dosemeter (APD) has been implemented into practice for the first time at Kaiga Atomic Power Station-3&4,  of Indian NPPs. The dosemeter showed tolerance level (L) 0.1085±0.0450 compared with 0.1869±0.0729 (average±SD) for CaSO4:Dy, TL dosemeter, having narrow range trumpet curve, nil electromagnetic interference. Records of >29 000 for APD and TL dosemeter were analysed for comparasion of the measurement of the individual dose. APD followed general acceptance rule of ±25 % for dose >1 mSv. Monthly Station collective dose by TL dosemeters and APD for normal reactor operation as well as outage are found in good agreement. Operational experiences and statistical analysis support that an APD dosemeter is reasonably equivalent to CaSO4:Dy TL dosemeter. The accuracy, reproducibility and repeatability of the measurement of radiation for (137)Cs are comparable with CaSO4:Dy, TL dosemeter. Operational experience of APD during the normal operation as well as outage showed as one of the best ALARA tool for occupational dose monitoring, control, management and future outage planning. PMID:23528326

Singh, Vishwanath P; Managanvi, S S; Bihari, R R; Bhat, H R

2013-03-24

9

Calibration of Neutron Dosemeters in the Presence of Scattered Neutrons.  

National Technical Information Service (NTIS)

The calibration of area and personnel dosemeters for neutron radiation is commonly carried out by means of isotopic neutron sources. In performing such irradiations in laboratories of usual dimensions the neutron spectrum, fluence rate and derived dosimet...

A. Rimpler

1987-01-01

10

Active electronic personal dosemeter in interventional radiology.  

PubMed

A recently developed active electronic personal dosemeter (AEPD) was utilised in order to measure the levels and the structure of occupational exposure to scattered X-ray radiation of medical staff who performed percutaneous revascularisation therapy that involves interventional radiology (IR) on the pelvis and upper leg arteries. The AEPDs, placed on the operators' and assistants' chests, that is, above the protective apron, continuously measured and recorded the received doses and, as a novelty, dose rates as a function of time, thus yielding a unique record of occupational doses and dose rates pattern at the working place. This paper presents and discusses one typical daily pattern in which seven percutaneous interventions were performed. PMID:19060296

Prlic, I; Suric Mihic, M; Vucic, Z

2008-12-05

11

Calibration of Far West Technology (FWT-60) radiachromic dye dosemeters  

SciTech Connect

Radiachromic dye dosimetry was used to measure kilogray doses absorbed by various liquid samples during gamma-ray exposure in a spent nuclear fuel pool. The source of nuclear fuel was the Advanced Test Reactor (ATR) at the Idaho National Engineering Laboratory (INEL). Calibrations were performed using a {sup 60}Co source and were run on bare dosemeters, as well as on dosemeters which mocked to simulate the samples. These dosemeters were prepared as a dye-impregnated nylon film and are commercially available. When exposed to gamma-ray doses of 0.5 to 200 kGy, a color change occurs which has an optical density proportional to absorbed dose. The difference in the calibration curves demonstrated the importance of irradiation of dosemeters under conditions as close to the actual samples as possible. Since these dosemeters could not be immersed directly in the organic solutions of interest, they were sandwiched between layers of lucite and stainless steel. This simulated the conditions inside an irradiated sample and provides a practical method of measuring absorbed doses. The reproducibility of measurements using the radiachromic dye dosemeters is also shown. 10 refs.

Mincher, B.J.; Zaidi, M.K.

1992-08-01

12

Calibration of Far West Technology (FWT-60) radiachromic dye dosemeters  

SciTech Connect

Radiachromic dye dosimetry was used to measure kilogray doses absorbed by various liquid samples during gamma-ray exposure in a spent nuclear fuel pool. The source of nuclear fuel was the Advanced Test Reactor (ATR) at the Idaho National Engineering Laboratory (INEL). Calibrations were performed using a {sup 60}Co source and were run on bare dosemeters, as well as on dosemeters which mocked to simulate the samples. These dosemeters were prepared as a dye-impregnated nylon film and are commercially available. When exposed to gamma-ray doses of 0.5 to 200 kGy, a color change occurs which has an optical density proportional to absorbed dose. The difference in the calibration curves demonstrated the importance of irradiation of dosemeters under conditions as close to the actual samples as possible. Since these dosemeters could not be immersed directly in the organic solutions of interest, they were sandwiched between layers of lucite and stainless steel. This simulated the conditions inside an irradiated sample and provides a practical method of measuring absorbed doses. The reproducibility of measurements using the radiachromic dye dosemeters is also shown. 10 refs.

Mincher, B.J.; Zaidi, M.K.

1992-01-01

13

Prediction analysis of dose equivalent responses of neutron dosemeters used at a MOX fuel facility.  

PubMed

To predict how accurately neutron dosemeters can measure the neutron dose equivalent (rate) in MOX fuel fabrication facility work environments, the dose equivalent responses of neutron dosemeters were calculated by the spectral folding method. The dosemeters selected included two types of personal dosemeter, namely a thermoluminescent albedo neutron dosemeter and an electronic neutron dosemeter, three moderator-based neutron survey meters, and one special instrument called an H(p)(10) monitor. The calculations revealed the energy dependences of the responses expected within the entire range of neutron spectral variations observed in neutron fields at workplaces. PMID:21498409

Tsujimura, N; Yoshida, T; Takada, C

2011-04-14

14

Superheated emulsions as high-energy neutron dosemeters.  

PubMed

Superheated emulsions being inexpensive, easy to fabricate, and having tissue equivalent composition make them as one of the popular neutron dosemeters. One more advantage is that they can be made insensitive to gamma rays by the choice of the sensitive liquid. It is observed that the response of commercially available bubble detector to neutron decreases above 20 MeV while its response is roughly flat in the 0.1-15 MeV region. This restricts its application as a dosemeter to high-energy neutrons. The response of bubble detector from Bubble Technology Industries, has been observed by using Pb-breeder for high-energy neutrons from different facilities in Japan. It is observed that 2-3 cm Pb-breeder is effective in increasing the response of the detector to the nominal value. Theoretical calculation using MCNPX code indicates an increase in neutrons in the energy range of 0.1-10 MeV with Pb-breeder. The present work indicates the possibility of using the bubble detector as a dosemeter to high-energy neutron using a Pb-breeder of proper thickness. PMID:15353668

Das, Mala; Sawamura, Teruko; Abe, Masashi; Kaneko, Junichi H; Homma, Akira; Fujita, Fumiyuki; Tsuda, Shuichi; Nishitani, Takeo

2004-01-01

15

The Role of Historical Operations Information for Supporting Remedial Investigation Work at the Former Harshaw Chemical Site  

SciTech Connect

In the early stages of hazardous, toxic, and radioactive waste (HTRW) site investigations, basic record searches are performed to help direct the agencies investigating contaminated sites to areas of concern and to identify contaminants of interest (COI). Plans developed on the basis of this preliminary research alone are often incomplete and result in unexpected discoveries either while in the field investigating the site or after the reports have been written. Many of the sites investigated under the Formerly Utilized Sites Remedial Action Program (FUSRAP) have complex histories that are slowly uncovered over the life of the project. Because of programmatic constraints, nuances of these sites are often discovered late in their programs and result in increased expenditures in order to fully characterize the site, perform a robust feasibility study, and recommend appropriate alternatives for remediation. By identifying resources for public records, classified records, historic aerial photographs, and other sources of site-specific historical information, a process can be established to optimize the collection of information and to develop efficient and complete project plans. In many cases, interviews with past site employees are very useful tools. In combining what is found in the records, observed on historic aerial photographs, and heard from former employees and family members, teams investigating these sites can begin to compile sound and more complete conceptual site models (CSM(s). The former Harshaw Chemical Site (HCS) illustrates this discovery process. HCS is part of FUSRAP. Preliminary investigations by the U.S. Department of Energy (DOE) in the 1970's provided an initial CSM of activities that had taken place that may have resulted in contamination. The remedial investigation (RI) conducted by the U.S. Army Corps of Engineers (USACE) was designed around this CSM. The RI work, however, identified a number of site conditions that were unexpected, including new potential COI associated with recycled uranium and contaminant locations that were inconsistent with the original CSM. As part of an RI Addendum effort, the USACE reconsidered its understanding of HCS historical activities. This effort included an intensive review of available historical aerial photography, an in-depth Potentially Responsible Parties (PRP) investigation, additional analysis of the production processes in place at HCS, and targeted supplemental data collection. The result of this effort was a revised CSM that included a number of previously unidentified potential COI and a much clearer understanding of the processes and resulting waste streams potentially associated with environmental contamination. Because of their complex and often poorly documented operational histories, unexpected discoveries will always be a part of investigating sites such as HCS. Taking advantage of available resources and expending funds for thorough historical research early in the life of a project will help to reduce the chances for expensive field re-mobilizations and significant schedule delays. A complete and accurate site history also allows for more efficient long-term technical and budgetary planning, thus eliminating many obstacles associated with the ultimate disposition of HTRW sites. (authors)

Kolhoff, A. [U.S. Army Corps of Engineers - Buffalo District, Buffalo, NY (United States); Johnson, R.; Peterson, J.; Picel, K. [Argonne National Laboratory, Argonne, IL (United States); DeVaughn, J. [Science Applications International Corporation, Twinsburg, OH (United States)

2008-07-01

16

New concept of IEC standards for radiation protection dosemeters.  

PubMed

The International Electrotechnical Commission (IEC) develops new standards for radiation protection dosemeters which follow a new concept. They are much more flexible in detail, but still ensure the same measurement quality. They are, for example, no longer specific for the detector type, but rather specific for the measurement task, e.g. for individual monitoring with active direct-reading instruments. Another example is that they are flexible with respect to the ranges of influence quantities. The conceptual changes are described in this paper, together with the advantages this new concept provides for manufacturers, users and legislators. PMID:18420572

Ambrosi, P; Behrens, R

2008-04-16

17

Type testing of the Siemens Plessey electronic personal dosemeter.  

PubMed

This paper presents the results of a laboratory assessment of the performance of a new type of personal dosimeter, the Electronic Personal Dosemeter made by Siemens Plessey Controls Limited. Twenty pre-production dosimeters and a reader were purchased by Ontario Hydro for the assessment. Tests were performed on radiological performance, including reproducibility, accuracy, linearity, detection threshold, energy response, angular response, neutron response, and response time. There were also tests on the effects of a variety of environmental factors, such as temperature, humidity, pulsed magnetic and electric fields, low- and high-frequency electromagnetic fields, light exposure, drop impact, vibration, and splashing. Other characteristics that were tested were alarm volume, clip force, and battery life. The test results were compared with the relevant requirements of three standards: an Ontario Hydro standard for personal alarming dosimeters, an International Electrotechnical Commission draft standard for direct reading personal dose monitors, and an International Electrotechnical Commission standard for thermoluminescence dosimetry systems for personal monitoring. In general, the performance of the Electronic Personal Dosemeter was found to be quite acceptable: it met most of the relevant requirements of the three standards. However, the following deficiencies were found: slow response time; sensitivity to high-frequency electromagnetic fields; poor resistance to dropping; and an alarm that was not loud enough. In addition, the response of the electronic personal dosimeter to low-energy beta rays may be too low for some applications. Problems were experienced with the reliability of operation of the pre-production dosimeters used in these tests. PMID:7790213

Hirning, C R; Yuen, P S

1995-07-01

18

Tupe testing of the Siemens Plessey electronic personal dosemeter  

SciTech Connect

This paper presents the results of a laboratory assessment of the performance of a new type of personal dosimeter, the Electronic Personal Dosemeter made by Siemens Plessey Controls Limited. Twenty pre-production dosimeters and a reader were purchased by Ontario Hydro for the assessment. Tests were performed on radiological performance, including reproducibility, accuracy, linearity, detection threshold, energy response, angular response, neutron response, and response time. There were also tests on the effects of a variety of environmental factors, such as temperature, humidity, pulsed magnetic and electric fields, low- and high-frequency electromagnetic fields, light exposure, drop impact, vibration, and splashing. Other characteristics that were tested were compared with the relevant requirements of three standards: an Ontario Hydro standard for personal alarming dosimeters, an International Electrotechnical Commission draft standard for direct reading personal dose monitors, and an International Electrotechnical Commission standard for thermoluminescence dosimetry systems for personal monitoring. In general, the performance of the Electronic Personal Dosemeter was found to be quite acceptable: it met most of the relevant requirements of the three standards. However, the following deficiencies were found: slow response time; sensitivity to high-frequency electromagnetic fields; poor resistance to dropping; and an alarm that was not loud enough. In addition, the response of the electronic personal dosimeter to low-energy beta rays may be too low for some applications. Problems were experienced with the reliability of operation of the pre-production dosimeters used in these tests. 11 refs., 8 figs., 24 tabs.

Hirning, C.R. [Ontario Hydro, Whitby, Ontario (Canada); Yuen, P.S. [Chalk River Laboratories, Chalk River, Ontario (Canada)

1995-07-01

19

Calibration, performance and type testing of personal dosemeters used in ionising-radiation applications in Greece.  

PubMed

Active Personal Dosemeters (APDs) are widely used in real-time personal dosimetry. Their performance, operational characteristics and limitations, as well as their calibration should be routinely checked to assure satisfactory operation and safe use. This study summarises the results of such type tests and calibrations performed in almost 4750 dosemeters at Ionising Radiation Calibration Laboratory (HIRCL) of Greek Atomic Energy Commission (GAEC). About 13.8% of the pencil type and 4.3% of the electronic dosemeters were found to be out of limits of acceptable performance. For the pencil type dosemeters, the mean calibration factor (CF+/-SD) for high- and low-dose categories was found to be 1.014+/-0.102 (range 0.793-1.458) and 0.995+/-0.059 (range 0.794-1.311), respectively. Of these >85% of them had reproducibility better than 90%, while <1% showed remarkable non-linearity and approximately 10% of them failed to retain the dose reading within the limits after 24 h. For the electronic dosemeters, the mean CF was 1.034+/-0.046 (range 0.967-1.238). The majority of them showed good reproducibility and linearity results while, after irradiation, the dose readings were not shifted through time. The energy response varies with the dosemeter type, reaching in one dosemeter type down to 50%. Both electronic and pencil did not showed electronic equilibrium problems. PMID:17185312

Boziari, A; Hourdakis, C J

2006-12-21

20

The use of active personal dosemeters as a personal monitoring device: comparison with TL dosimetry.  

PubMed

The use of active personal dosemeters (APDs) not only as a warning device but also, in some cases, as an official and hence stand-alone dosemeter is rapidly increasing. A comparison in terms of dose, energy and angle dependence, among different types of APD and a routinely used whole-body thermoluminescence dosemeter (TLD) has been performed. Significant differences were found between the TLD readings and mainly some not commonly used APDs. The importance of choosing the best adapted APD according to the radiation field characteristics is pointed out. PMID:21196464

Boziari, A; Koukorava, C; Carinou, E; Hourdakis, C J; Kamenopoulou, V

2010-12-31

21

Use of commercial alanine and TL dosemeters for dosimetry intercomparisons among Italian radiotherapy centres.  

PubMed

In the implementation of a large-scale dosimetry intercomparison one of the main constraints is the availability of large number of dosemeters of the highest quality. Therefore, ISS tested the possibility of using commercially available dosemeters, alanine pellets and thermoluminescence (TL) dosimetry chips, for transfer dosimetry within the Italian intercomparison programme. In this work the characterisation of commercial alanine and TL dosemeters along with the ISS dose assessment procedure used in the Italian intercomparison are reported. Results demonstrate the feasibility of the ISS approach to transfer dosimetry since it is possible to measure 10 Gy with a combined uncertainty of 1% (1sigma) and 1 Gy with a combined uncertainty of 1.7% (1sigma) with alanine and TL dosemeters, respectively. PMID:16644956

Onori, S; Bortolin, E; Calicchia, A; Carosi, A; De Angelis, C; Grande, S

2006-04-27

22

Compliance of electronic personal neutron dosemeters with the new International Standard IEC 61526.  

PubMed

The recommendations and test requests for the dose equivalent response of personal neutron dosemeters formulated by the new International Standard IEC 61526 are summarised. In particular, IEC 61526 allows the use of broad fields if dosemeters do not fulfil the hard requirements using monoenergetic neutrons. Some broad fields which can work as a replacement field using ISO sources (252Cf, 252Cf (D2O mod.), 241Am-Be) and simulated workplace fields (CANEL and SIGMA) are described. This work shows the results of recent measurements of the personal dose equivalent response for the dosemeters Thermo Electron EPD-N2, Aloka PDM-313 and the prototype dosemeter PTB DOS-2002, and discusses their compliance with respect to the new IEC 61526 standard. PMID:17213218

Luszik-Bhadra, M

2007-01-08

23

1983 ORNL intercomparison of personnel neutron and gamma dosemeters  

SciTech Connect

The Ninth Personnel Dosimetry Intercomparison Study was conducted during April 19-21, 1983, at the Oak Ridge National Laboratory. Dosemeters from 33 participating agencies were mounted on water-filled polyethylene elliptical phantoms and exposed to a range of low-level dose equivalents (0.02-0.45 mSv gamma and 0.49-11.14 mSv neutron) which could be encountered during routine personnel monitoring in mixed radiation fields. The Health Physics Research Reactor served as the radiation source for six separate exposures which used four different shield conditions: unshielded and shielded with steel, steel/concrete, and concrete. Results of the neutron measurements indicate that it is not unusual for dose equivalent estimates made under the same conditions by different agencies to differ by more than a factor of 2. Albedo systems, which were the most popular neutron monitors in this study, provided the most accurate results with CR-39 recoil track being least accurate. Track and film neutron systems exhibited problems providing measurable indication of neutron exposure at dose equivalents of about 0.50 mSv. Gamma measurements showed that TLD and film systems generally overestimated dose equivalents in the mixed radiation fields with film exhibiting significant problems providing measurable indication of gamma exposure at dose equivalents lower than about 0.15 mSv. Under the conditions of this study in which exposures were carefully controlled and participants had information concerning exposure conditions and incident spectra prior to dosemeter analysis, only slightly more than half of all neutron and gamma dose equivalent estimates met regulatory accuracy standards relative to reference values. These results indicate that continued improvement of mixed-field personnel dosimetry is required by many participating organizations. 15 references, 30 tables.

Swaja, R.E.; Sims, C.S.; Greene, R.T.

1985-01-01

24

A Photographic Dosemeter for the Measurement of Personal Doses of Environmental Radiation  

Microsoft Academic Search

An attempt has been made to develop a pocket dosemeter to measure small doses of radiation delivered at natural background dose-rates.The dosemeter employs cylindrical plastic scintillators in contact with Ilford PM1 film to achieve a sensitivity, at background dose-rates, of 25-30 times that of the film alone. Two Perspex cylinders are used to provide a control density area, and the

P W Henson

1963-01-01

25

High-energy response of passive dosemeters in use at LANL.  

PubMed

The high-energy neutron response of three passive dosemeters in use at the Los Alamos National Laboratory (LANL) has been investigated using metrology-grade fields. The dosemeters include the LANL Model 8823 TLD badge and the LANL PN3 track etch device. Both are dosemeters of record at LANL. The third device was the Personal Neutron Dosemeter (PND), a superheated emulsion device, manufactured by Bubble Technology Industries, Inc. (BTI). The response of the three dosemeters at neutron energies exceeding 10 MeV was assessed with monoenergetic neutrons at the Physikalisch-Technische Bundesanstalt facility (14.8 and 19 MeV). For the sake of completeness, data collected at lower energies are also included in this study. High-energy quasi-monoenergetic beams produced by the cyclotron facilities at the Université Catholique de Louvain (UCL) and the The Svedberg Laboratory (TSL) were also utilised as part of this study. These measurements were made to better understand and help interpret dosemeter readings obtained by workers at high-energy accelerators, such as the 800 MeV spallation neutron source facility located at the Los Alamos Neutron Science Center (LANSCE). PMID:17522036

Olsher, Richard H; McLean, Thomas D; Mallett, Michael W; Romero, Leonard L; Devine, Robert T; Hoffman, Jeffrey M

2007-05-23

26

Characteristics and Performance of the Sunna High Dose Dosemeter Using Green Photoluminescence and UV Absorption Readout Methods  

SciTech Connect

Growth in the use of ionizing radiation for medical sterilization and the potential for wide-scale international food irradiation have created the need for robust, mass-producible, inexpensive, and highly accurate radiation dosemeters. The Sunna dosemeter, lithium fluoride injection-moulded in a polyethylene matrix, can be read out using either green photoluminescence or ultraviolet (UV) absorption.

Miller, Steven D.; Murphy, Mark K.; Tinker, Mike R.; Kovacs, Andres; Mclaughlin, William

2002-01-01

27

Calibration of personal dosemeters in terms of the ICRU operational quantities  

SciTech Connect

The International Commission on Radiological Units and Measurements (ICRU) has defined several new operational quantities for radiation protection purposes. The quantities to be used for personal monitoring are defined at depths in the human body. Because these quantities are impossible to measure directly, the ICRU has recommended that personal dosemeters should be calibrated under simplified conditions on an appropriate phantom, such as the ICRU sphere. The US personal dosimetry accreditation programs make use of a 30 {times} 30 {times} 15 cm polymethymethacrylate (PMMA) phantom, therefore it is necessary to relate the response of dosemeters calibrated on this phantom to the ICRU operational quantities. Calculations of the conversion factors to compute dosemeter response in terms of the operational quantities have been performed using the code MCNP. These calculations have also been compared to experimental measurements using thermoluminescent (TLD) detectors.

McDonald, J.C. [Pacific Northwest Lab., Richland, WA (United States); Hertel, N.E. [Texas Univ., Austin, TX (United States). Dept. of Mechanical Engineering

1992-05-01

28

Independent evaluation of optically stimulated luminescence (OSL) 'dot' dosemeters for environmental monitoring.  

PubMed

Optically stimulated luminescence (OSL) 'dot' dosemeters (manufactured by Landauer®) are reported to have a high degree of environmental stability, high level of sensitivity and provide wide range of dose measuring capabilities from 0.05 mGy to 100 Gy. The optical read out method is fast and relatively simple and permits repeated read out, but few studies have been performed about its application in monitoring radiation in the environment. This study was initiated to independently test the performance of OSL dot dosemeters for the application of measuring doses of radiation in the outdoor environment. Testing was performed in the laboratory to evaluate reproducibility and stability and in the field to evaluate accuracy relative to calibrated high-pressure ionisation chambers. The results showed that OSL dot dosemeters had good reproducibility and stability in both laboratory and field tests and met the performance requirements of standards of the American National Standards Institute. PMID:20947590

Timilsina, Bindu; Gesell, Thomas F

2010-10-14

29

Operational comparison of TLD albedo dosemeters and solid state nuclear tracks detectors in fuel fabrication facilities.  

PubMed

The authors carried out an operational study that compared the use of TLD albedo dosemeters and solid state nuclear tracks detector in plutonium environments of Japan Nuclear Cycle Development Institute, Tokai Works. A selected group of workers engaged in the fabrication process of MOX (Plutonium-Uranium mixed oxide) fuel wore both TLD albedo dosemeters and solid state nuclear tracks detectors. The TL readings were generally proportional to the counted etch-pits, and thus the dose equivalent results obtained from TLD albedo dosemeter agreed with those from solid state nuclear tracks detector within a factor of 1.5. This result indicates that, in the workplaces of the MOX fuel plants, the neutron spectrum remained almost constant in terms of time and space, and the appropriate range of field-specific correction with spectrum variations was small in albedo dosimetry. PMID:17337735

Tsujimura, N; Takada, C; Yoshida, T; Momose, T

2007-03-03

30

Comparison of measurements on tissue kerma and photon radiation dose made with emergency dosemeters  

SciTech Connect

The purpose of this paper is to compare the tissue equivalence and tissue kerma for dosimetric tissue-equivalent detectors with allowance for the neutron spectra. Results are given for the calculated dose sensitivities for the DINA and GNEIS dosemeters for a portion of the neutron spectra recommended by IAEA for comparative tests. The measurements were made with five nuclear systems - BR-10, RF-GS, BR-1-21, BR-1-21, and IBR-30 - as well as with accelerators. Doses from photon radiation were also measured using thermoluminescent and photoluminescent dosemeters sensitive to neutrons.

Golub, V.V.; Lashuk, A.I.; Shalin, V.A.

1987-05-01

31

Ustanovka dlya poverki nejtronnykh dozimetrov i radiometrov. (Neutron dosemeters and radiometers check-up installation).  

National Technical Information Service (NTIS)

Self-protecting installation UPND-1 for checking-up of neutron dosemeters and radiometers is developed for the operative check-up of the working devices by the equivalent field method and the reverse squares one. The installation is supplied by typical co...

E. A. Konovalov L. M. Ploshchanskij Y. Sajkov V. I. Fominykh

1989-01-01

32

Comparison of measurements on tissue kerma and photon radiation dose made with emergency dosemeters  

Microsoft Academic Search

The purpose of this paper is to compare the tissue equivalence and tissue kerma for dosimetric tissue-equivalent detectors with allowance for the neutron spectra. Results are given for the calculated dose sensitivities for the DINA and GNEIS dosemeters for a portion of the neutron spectra recommended by IAEA for comparative tests. The measurements were made with five nuclear systems -

V. V. Golub; A. I. Lashuk; V. A. Shalin

1987-01-01

33

Long-term PTB intercomparison of passive H*(10) dosemeters used in area monitoring  

NASA Astrophysics Data System (ADS)

This intercomparison serves to investigate the long-term behaviour of passive (or similarly used active) H*(10) dosemeters which are dedicated to the monitoring of the surroundings of nuclear plants and accelerators and used in the radiation field of the natural ambient radiation. From autumn 2005 to spring 2007, approx. 650 photon and neutron dosemeters were exposed to environmental radiation at three dosimetric reference sites, operated by the Physikalisch-Technische Bundesanstalt (PTB). In addition to the measurements under natural conditions a number of dosemeters was also subjected to an additional irradiation in PTB photon and neutron fields. Ten measuring bodies and institutions, which are involved in ambient monitoring in Germany, Austria and Switzerland, took part in this intercomparison. The intercomparison revealed the typical precision to be expected from long-term dose measurements in the natural environment. The difference of the response of the dosemeters to terrestrial and to cosmic radiation was determined. From the results of this intercomparison some sources of uncertainty were identified and some recommendations to improve area monitoring were derived.

Dombrowski, H.; Neumaier, S.

2012-04-01

34

Assessment of neutron dosemeters around standard sources and nuclear fissile objects.  

PubMed

In order to evaluate the neutron doses around nuclear fissile objects, a comparative study has been made on several neutron dosemeters: bubble dosemeters, etched-track detectors (CR-39) and 3He-filled proportional counters used as dose-rate meters. The measurements were made on the ambient and the personal dose equivalents H*(10) and Hp(10). Results showed that several bubble dosemeters should have been used due to a low reproducibility in the measurements. A strong correlation with the neutron energy was also found, with about a 30% underestimation of Hp(10) for neutrons from the PuBe source, and about a 9% overestimation for neutrons from the 252Cf source. Measurements of the nuclear fissile objects were made using the CR-39 and the dose-rate meters. The CR-39 led to an underestimation of 30% with respect to the neutron dose-rate meter measurements. In addition, the MCNP calculation code was used in the different configurations. PMID:12382734

Raimondi, N; Tournier, B; Groetz, J E; Piot, J; Riebler, E; Crovisier, P; Chambaudet, A; Cabanné, N

2002-01-01

35

Brazilian gamma-neutron dosemeter: response to 241AmBe and 252Cf neutron sources.  

PubMed

With the aim of improving the monitoring of workers potentially exposed to neutron radiation in Brazil, the IPEN/CNEN-SP in association with PRO-RAD designed and developed a passive individual gamma-neutron mixed-field dosemeter calibrated to be used to (241)AmBe sources. To verify the dosimetry system response to different neutron spectra, prototypes were irradiated with a (252)Cf source and evaluated using the dose-calculation algorithm developed for (241)AmBe sources. PMID:21186217

Souto, E B; Campos, L L

2010-12-24

36

The features of the new radon gas CR39 dosemeter developed at the ENEA Institute of Radioprotection  

Microsoft Academic Search

A new radon gas dosemeter (patent pending) has been designed and tested to be used as a routine referenced device to monitor radon exposures in workplaces and dwelling. It has been conceived as a practical tool to be effectively used in the practice of a qualified Service, operating under QA. Monte Carlo simulation has been extensively used to optimize the

M. Calamosca; S. Penzo; G. Gualdrini

2003-01-01

37

Experimental determination of CR39 counting efficiency to ? particles to design the holder of a new radon gas dosemeter  

Microsoft Academic Search

To design a new radon gas dosemeter, the knowledge of the SSNTD ? counting efficiency is essential. It depends primarily on the energy and incidence angle into the detector, then on the etching conditions and finally on the track counting procedure. Therefore the elicited efficiency function represents all these factors. The detectors were exposed to ? particles at different angles

M. Calamosca; S. Penzo; G. Gualdrini

2003-01-01

38

Responses of commercially available neutron electronic personal dosemeters in neutron fields simulating workplaces at MOX fuel fabrication facilities  

Microsoft Academic Search

The authors investigated the performance of three commercially available electronic personal dosemeters (EPDs) in evaluating neutron dose equivalents and discussed their suitability to work environments in MOX fuel fabrication facilities. The EPDs selected for this study were NRY21 (Fuji Electric Systems), PDM-313 (Aloka) and DMC 2000 GN (MGP Instruments). All tests were conducted in moderated 252Cf neutron fields with neutron spectral

N. Tsujimura; T. Yoshida; C. Takada

39

Photon beam audits for radiation therapy clinics: a pilot mailed dosemeter study in Turkey.  

PubMed

A thermoluminescent dosemeter (TLD) mailed dose audit programme was performed at five radiotherapy clinics in Turkey. The intercomparison was organised by the University of Wisconsin Radiation Calibration Laboratory (UWRCL), which was responsible for the technical aspects of the study including reference irradiations, distribution, collection and evaluation. The purpose of these audits was to perform an independent dosimetry check of the radiation beams using TLDs sent by mail. Acrylic holders, each with five TLD chips inside and instructions for their irradiation to specified absorbed dose to water of 2 Gy, were mailed to all participating clinics. TLD irradiations were performed with a 6 MV linear accelerator and (60)Co photon beams. The deviations from the TL readings of UWRCL were calculated. Discrepancies inside the limits of ±5 % between the participant-stated dose, and the TLD-measured dose were considered acceptable. One out of 10 beams checked was outside this limit, with a difference of 5.8 %. PMID:21362695

Yegingil, Z; DeWerd, L A; Davis, S D; Hammer, C; Kunugi, K

2011-02-28

40

Automation of radiation dosimetry using PTW dosemeter and LabVIEW™  

NASA Astrophysics Data System (ADS)

Automation of UNIDOS “Dosemeter” using personal computer (PC) is discussed in this paper.In order to save time and eliminate human operation errors during the radiation dosimetry, suitable software, using LabVIEW™ graphical programming language, was written to automate and facilitate the processes of measurements, analysis and data storage.The software calculates the calibration factor of the ionization chamber in terms of air kerma or absorbed dose to water according to IAEA dosimetry protocols. It also has the ability to print a calibration certificate.The obtained results using this software are found to be more reliable and flexible than those obtained by manual methods previously employed.Using LabVIEW™ as a development tool is extremely convenient to make things easier when software modifications and improvements are needed.

Weiss, C.; Al-Frouh, K.; Anjak, O.

2011-10-01

41

Track-etch dosemeter response to neutrons up to 300 MeV  

SciTech Connect

Electro-chemical and chemical track-etch dosemeters were obtained from commercial suppliers and exposed to neutrons produced at the LANTF WNR white neutron source at 15{degree} with no shielding and filtered by polyethylene blocks of 2.5, 5.1, 10.2, 20.3 and 40.6 cin thickness. The neutron spectrum was determined using calculations. Mean energies from 28 to 300 MeV were produced. Dose was calculated from the NCRP-38 flux-to-dose conversion. The results are compared with NTA film which was exposed in the same configuration. The response of track etch dosimeters was found to reach a minimum and then rise as the average neutron energy increased. The response of the NTA film increased as the neutron energy increased.

Devine, R.T.; Walker, S.; Staples, P.; Duran, M. [Los Alamos National Lab., NM (United States); Mundis, R.; Miller, J. [Science Applications International Corp., Los Alamos, NM (United States)

1996-04-01

42

A comparative study of the responses of lithium borate and calcium sulphate phosphors in a TL personal dosemeter.  

PubMed

This work summarises the results of a series of experiences made on Panasonic UD-802AS, a multi-element dosemeter that is currently used in Caorso Nuclear Power Plant for personnel external monitoring. Two main topics have been considered: energy response and the influence of working place dose rate on relative readings of the elements at the end of the monitoring period. The presence of four elements of different materials and filtrations gives the possibility of evaluating radiation energy by a simple algorithm, so that an accurate estimate of the personal dose equivalent can be provided; the good results of the participation of Caorso Individual Monitoring Service (IMS) to 'EURADOS 2008 intercomparison on whole-body dosemeters' account for the reliability of the method. A study on the response in low-dose rate fields is also reported, giving in practice interesting information about operational conditions. PMID:21296771

Ceretti, M; Costa, G; Romani, S; Bobba, F

2011-02-04

43

The use of Lithium Flouride Thermoluminescent Dosemeters to measure the Dose Distribution of a 15 MeV Electron Beam  

Microsoft Academic Search

A comparison was made of the central axis depth-dose curves obtained for 15 MeV electrons using an ion chamber and LiF dosemeters. The two uncorrected curves were very similar and gave the same depth-dose curves within experimental limits. Corrections that must be made to the LiF curve for energy and dose dependence and to the ion chamber readings for the

Peter R Almond; Ann Wright; J. F. Lontz II

1967-01-01

44

Comparison of TLD100 and MCP-Ns for use as an extremity dosemeter for PET nuclear medicine staff  

Microsoft Academic Search

This study focuses on extremity monitoring of PET nuclear medicine personnel. In particular, it aims to compare the performance of ring dosemeters with TLD-100 and MCP-Ns detectors during the handling of positron emitters such as 18F-FDG radiopharmaceuticals. Experimental and Monte Carlo results highlight the fact that the contribution of positron to Hp(0.07), in contact with or at short distances from

M. Ginjaume; S. Pérez; M. A. Duch; X. Ortega

2008-01-01

45

Dose rate dependency of electronic personal dosemeters measuring X- and gamma-ray radiation.  

PubMed

Three models of electronic personal dosemeters (EPDs)-Siemens Mk 2.3, Rados RAD-60S and Vertec Bleeper Sv-were irradiated with seven photon beam qualities: 60Co, 137Cs and the ISO narrow spectrum series X-ray qualities N-250, N-200, N-150, N-60 and N-20. The personal dose equivalent rates delivered to the devices varied between 0.002 and 0.25 mSv s(-1). Measurements were made with the EPDs mounted free-in-air as well as against Lucite and water phantoms. Results for all models of EPDs showed differences in personal dose equivalent energy response for different energies covered by this range of radiation qualities, with different models showing variations from 15 to 65%. In some cases, the personal dose equivalent rate response of these devices varied by a factor of 3 between irradiations at typical calibration dose rates and those normally encountered by nuclear energy workers. PMID:18420561

McCaffrey, J P; Shen, H; Downton, B

2008-04-16

46

Organ and effective dose evaluation in diagnostic radiology based on in-phantom dose measurements with novel photodiode-dosemeters.  

PubMed

Organ and the effective doses of patients undergoing clinical X ray examinations of chest and abdomen were evaluated with an anthropomorphic phantom and a new dosimetry system. The system was comprised of 34 pin photodiode dosemeters placed in/on particular tissues or organs of the anthropomorphic phantom, where the tissues and organs are defined by the International Commission on Radiological Protection (ICRP) to estimate the effective doses. Dosemeter signals were acquired on a personal computer directly, and converted into absorbed doses, from which the organ and the effective doses were evaluated on the computer. Our study showed that organ doses ranged from <0.01 to 0.72 mGy in routine X-ray radiography of chest and of abdomen and from 0.07 to 55.91 mGy in routine computed tomography (CT) examinations with current multi-slice CT scanners. The effective dose observed in the chest CT examination was approximately 300 times higher than that in chest radiography. PMID:16439515

Kawaura, Chiyo; Aoyama, Takahiko; Koyama, Shuji; Achiwa, Masataka; Mori, Masaki

2006-01-26

47

Bias and uncertainty of penetrating photon dose measured by film dosemeters in an epidemiological study of US nuclear workers.  

PubMed

A retrospective exposure assessment of 1269 study subjects was completed for use in a multi-site case-control study of the relationship between protracted workplace external radiation exposure and leukaemia mortality. The majority of exposure data result from film badge monitoring programmes at the four US weapons production facilities and a US Naval shipyard. Bias and uncertainty in reported exposures among study facilities and across time were as result of differences in incident photon energy, exposure geometry, dosemeter type and dosimetry methods. These sources of measurement uncertainty were examined by facility and time to derive bias factors (B) for normalising exposures. In conjunction with facility reported results, the bias factors provide a means to estimate the equivalent dose, penetrating to a depth of 10 mm [H(p)(10)] and the equivalent dose to the active bone marrow for use in the epidemiological study. Uncertainty was expressed as the constructed 95% confidence interval (i.e. the 2.5th-97.5th% range) of the estimated parameter. The bias factors indicate that recorded exposures provide a reasonable estimate of H(p)(10) (bias factor near unity) and overestimate equivalent dose to active bone marrow (H(T)) by a factor between 1.2 and 1.7. On average, dosemeter-response uncertainties estimated using Monte Carlo simulation were approximately +/-19 and +/-33% for H(p)(10) and H(T), respectively. PMID:15769802

Daniels, R D; Schubauer-Berigan, M K

2005-03-15

48

The use of passive personal neutron dosemeters to determine the neutron component of cosmic radiation fields in spacecraft  

NASA Astrophysics Data System (ADS)

For the altitude range and inclination of the International Space Station (ISS), secondary neutrons can be a major contributor to dose equivalent inside a spacecraft. The exact proportion is very dependent on the amount of shielding of the primary galactic cosmic radiation and trapped particles, but is likely to lie in the range of 10% to 50%. Personal neutron dosemeters of simple design, and processed using simple techniques developed for personal dosimetry may be used to estimate this neutron component. For the etch regime employed, the combination of high LET threshold (there is little response below a restricted LET200 in PADC of about 40 keV ?m-1), and poor angle dependence of response to high-energy charged particles (HZE), results in a much reduced overall response of the neutron dosimeter to the HZE component of the field in spacecraft and no response to protons of energy greater than about 2 MeV. Preliminary measurements indicate that for examples of the HZE component of the radiation fields in spacecraft, a correction of 5 to 10 % is necessary to account for the detector HZE response. Alternatively, an additional chemical etch can be carried out which allows discrimination. Recent results for exposures in low Earth orbit are reported.

Bartlett, D. T.; Hager, L. G.; Tanner, R. T.

49

On the use of LiF:Mg,Ti thermoluminescence dosemeters in space--a critical review.  

PubMed

The use of LiF:Mg,Ti thermoluminescence dosemeters (TLDs) in space radiation fields is reviewed. It is demonstrated in the context of modified track structure theory and microdosimetric track structure theory that there is no unique correlation between the relative thermoluminescence (TL) efficiency of heavy charged particles, neutrons of all energies and linear energy transfer (LET). Many experimental measurements dating back more than two decades also demonstrate the multivalued, non-universal, relationship between relative TL efficiency and LET. It is further demonstrated that the relative intensities of the dosimetric peaks and especially the high-temperature structure are dependent on a large number of variables, some controllable, some not. It is concluded that TL techniques employing the concept of LET (e.g. measurement of total dose, the high-temperature ratio (HTR) methods and other combinations of the relative TL efficiency of the various peaks used to estimate average Q or simulate Q-LET relationships) should be regarded as lacking a sound theoretical basis, highly prone to error and, as well, lack of reproducibility/universality due to the absence of a standardised experimental protocol essential to reliable experimental methodology. PMID:14653322

Horowitz, Y S; Satinger, D; Fuks, E; Oster, L; Podpalov, L

2003-01-01

50

Calculated energy response correction factors for LiF thermoluminescent dosemeters employed in the seventh EULEP dosimetry intercomparison  

NASA Astrophysics Data System (ADS)

Several dosimetry intercomparisons for whole body irradiation of mice have been organized by the European Late Effects Project Group (EULEP). These studies were performed employing a mouse phantom loaded with LiF thermoluminescent dosemeters (TLDs). In-phantom, the energy response of the LiF TLDs differs from free-in-air, due to spectral differences caused by attenuation and scatter of x-rays. From previous studies, energy response correction factors in-phantom relative to free-in-air were available for full scatter conditions. In the more recent intercomparisons, however, full scatter conditions were not always employed by the participants. Therefore, Monte Carlo calculations of radiation transport were performed to verify the LiF TLD energy response correction factors in-phantom relative to free-in-air for full scatter conditions and to obtain energy response correction factors for geometries where full scatter conditions are not met. For incident x-rays with HVLs in the 1 to 3.5 mm Cu range, the energy response correction factor in-phantom deviates by 2 to 4 per cent from that measured free-in-air. This is in reasonable agreement with previously published results. The energy response correction factors obtained from the present study refer to a calibration in terms of muscle tissue dose in-phantom using gamma rays. For geometries where full scatter conditions are not fulfilled, the energy response correction factors are different by up to about 3 per cent at maximum from that at full scatter conditions. The dependence of the energy response correction factor as a function of the position in-phantom is small, i.e. about 1 per cent at maximum between central and top or bottom positions.

Zoetelief, J.; Jansen, J. Th M.

1997-08-01

51

The effect of visible light on Harshaw Model 8801 thermoluminescent dosimeters  

SciTech Connect

It has been known for some time that illumination of lithium fluoride (LiF) thermoluminescent dosimeters, particularly with ultraviolet wavelengths, causes these dosimeters to emit thermoluminescence (TL), similar to that caused by exposure to radiation. However the effect of incandescent light on dosimeters is not well documented. In this study the growth, saturation and spectral dependence of this luminescence is studied for open dosimeter cards illuminated with room incandescent light, and for dosimeters inside their holders exposed to bright sunlight. The results confirm that illumination with room light does give rise to luminescence in unirradiated dosimeters. Light in the ultraviolet is an order of magnitude more efficient in producing this TL than is longer wave length (red) visible light. The illumination-induced TL saturates at intensities that correspond to TL produced by exposure of about 70 mR of {sup 137}Cs; thus illumination clearly can give rise to false radiation exposure reports. Moreover it was fund that the dosimeter holder allows enough light to enter so that exposure of dosimeters to bright sunlight will activate some of the chips of the dosimeter cards in a fashion identical to that of room light. The glow curves produced by light are broader than those produced by gamma irradiation and a series of experiments have confirmed that the light induced TL comes from the Teflon sheets holding the LiF dosimeters, rather than the LiF chips themselves. 13 refs., 5 figs., 2 tabs.

Sonder, E.; Ahmed, A.B.; McMahan, K.L.; Colwell, D.S.; Smith, P.R.

1990-09-01

52

Phototransferred Thermoluminescence of KCL:Eu2+ Dosemeters  

Microsoft Academic Search

The phototransferred thermoluminescence (PTTL) of KCl:Eu2+ crystals was studied after exposure to X -rays or beta radiation. The main thermoluminescence (TL) peaks were found around 370, 390 and 470 K. The 470 K highest intensity peak is considered to be the dosimetric peak due to its low fading and linear dose behavior. The main dosimetric peak is sharply decreased after

M. Barboza-Flores; R. Meléndrez; V. Chernov; R. Bernal; T. M. Piters; R. Pérez-Salas; R. Aceves; M. Pedroza-Montero; B. Castañeda

2001-01-01

53

Individual gamma Dosemeter MD 20: Physical Tests and Evaluation Tests.  

National Technical Information Service (NTIS)

Tests on the digital individual dose ratemeter type DM 20 for gamma radiation measurement are presented. The aim of this testing is an evaluation of main physical characteristics under irradiation. Results are given in tables and graphs. Relative sensitiv...

R. Laureana

1981-01-01

54

Lithium-gadolinium-borate as a neutron dosemeter.  

PubMed

Lithium-gadolinium-borate (LGB) dispersed as microcrystals within the plastic scintillator BC-490 is a promising material for accurate neutron dosimetry in mixed n/gamma fields. Spectral information > 1 MeV is obtained by capture gating proton recoil events in the plastic scintillator to subsequent capture in (6)Li. Below 1 MeV, isolated capture events in either gadolinium or (6)Li give energy information in this region. Discrimination based on capture gating is used to reject false coincidences due to gamma rays or incorrectly gated neutron events. A detailed Monte Carlo model has been created in MCNPX that predicts the energy response of the LGB spectrometer in the capture-gated mode of operation. X-ray microtomography has been performed on the detector in order to obtain the LGB microcrystal distribution within the plastic scintillator, and this is incorporated into the model. The way in which the calculated response functions can be included in an unfolding procedure is outlined. PMID:17578875

Lewis, D V; Spyrou, N M; Williams, A M; Beeley, P A

2007-06-19

55

Multisphere neutron spectrometric system with thermoluminescence dosemeters: sensitive improvement.  

PubMed

In this work, a neutron spectrometric system based on a set of moderating spheres with thermoluminescence detectors (TLD) is presented. The system at the Nuclear Regulatory Authority (ARN) Dosimetry Laboratory consists of 12 solid spheres made of high-density polyethylene (p = 0.95 g x cm(-3)), with diameters ranging from 2" to 12" and TLD sensitive to thermal and gamma radiation, namely TLD-600 and TLD-700, located at the centre of the spheres. The neutron response matrix for this Bonner Sphere Spectrometer (BSS) was calculated using the MCNP-IVB code and the library ENDF/B-VI in the energy range between thermal neutrons and 100 MeV. The neutron spectrum was obtained using the LOUH182 unfolding code. The improvement in sensitivity of the system is based on the election of a different heating cycle of the TLD that allows an increase in sensitivity by a factor of 2.6 compared with the standard laboratory treatment. The system response for the calibration with an Am-Be source is presented. PMID:12382722

Gregori, B; Papadópulos, S; Cruzate, J; Kunst, J J

2002-01-01

56

Phototransferred Thermoluminescence of KCL:Eu2+ Dosemeters  

NASA Astrophysics Data System (ADS)

The phototransferred thermoluminescence (PTTL) of KCl:Eu2+ crystals was studied after exposure to X -rays or ? radiation. The main thermoluminescence (TL) peaks were found around 370, 390 and 470 K. The 470 K highest intensity peak is considered to be the dosimetric peak due to its low fading and linear dose behavior. The main dosimetric peak is sharply decreased after illumination with UV light of a previously irradiated specimen. The PTTL is wavelength dependent and has been shown to peak in the 220 - 230 nm region and 650 nm in previously non irradiated and irradiated samples, respectively. The PTTL spectral response is always a broad band around 390 - 490 nm peaked at 425 nm, which is related to the well-known Eu2+ emission.

Barboza-Flores, M.; Meléndrez, R.; Chernov, V.; Bernal, R.; Piters, T. M.; Pérez-Salas, R.; Aceves, R.; Pedroza-Montero, M.; Castañeda, B.

2001-04-01

57

Alarm inhalation dosemeter for long living radioactive dust due to an uncontrolled release  

SciTech Connect

MyRIAM is the acronym for My Radioactivity In Air Monitor and points out that the device was designed for personal use to detect any radioactivity in the air at the place and at the moment of danger. The active air sampling process enables a detection limit several orders of magnitude below that of Gamma detectors. Therefore, it is the unique way to detect dangerous exposures in time.Individual protection against inhalation of long living radioactive dust (LLRD) saves human life and health. LLRD may occur in natural environment as well as in case of nuclear accidence or military and terrorist attacks. But in any case, the immediate warning of the population is of great importance. Keep in mind: it is very easy to avoid LLRD inhalation--but you have to recognize the imminent danger. The second requirement of gap-less documentation and reliable assessment of any derived LLRD exposure is building the link to Dosimetry applications.The paper demonstrates the possibility to design small and low cost air samplers, which can be used as personal alarm dosimeters and fulfil the requirements mentioned above.Several test measurements taken by a mobile phone sized MyRIAM, shall be used to demonstrate the correctness of this statement.

Streil, T.; Oeser, V. [SARAD GmbH, Wiesbadener Str. 10-20, D-01159 Dresden (Germany); Rambousky, R.; Buchholz, F. W. [SARAD GmbH, Wiesbadener Str. 10-20, D-01159 Dresden (Germany); Armed Forces Scientific Institute for Protection Technologies-NBC Protection PO.Box 1142, 29633 Munster (Germany)

2008-08-07

58

Response of silicon diode dosemeters to scattered radiation from megavoltage photon beams.  

PubMed

Dose response effects of diodes due to the high atomic number of silicon relative to water are investigated. While quality chances in the primary component of a megavoltage beam with depth are minimal. Compton scattered photons are shown to have a substantial effect on the quality leading to their enhanced absorption in silicon via the photoelectric effect. Monte Carlo methods were used to study and model this phenomenon. Measurements of dose rate, depth and field size dependence are examined for commercially available diode detectors and ionisation chambers. PMID:12382780

Yin, Z; Hugtenburg, R P; Beddoe, A H

2002-01-01

59

Detection of thermal neutrons with a CMOS pixel sensor for a future dosemeter  

SciTech Connect

The RaMsEs group (Radioprotection et Mesures Environnementales) is developing a new compact device for operational neutron dosimetry. The electronic part of the detector is made of an integrated active pixel sensor, originally designed for tracking in particle physics. This device has useful features for neutrons, such as high detection efficiency for charged particles, good radiation resistance, high readout speed, low power consumption and high rejection of photon background. A good response of the device to fast neutrons has already been demonstrated [1]. In order to test the sensibility of the detector to thermal neutrons, experiments have been carried out with a 512 x 512 pixel CMOS sensor on a californium source moderated with heavy water (Cf.D{sub 2}O) on the Van Gogh irradiator at the LMDN, IRSN, Cadarache (France)). A thin boron converter is used to benefit from the significant cross section of the {sup 10}B (n,{alpha}) {sup 7}Li reaction. Results show a high detection efficiency (around 10{sup -3}) of the device to thermal neutrons. Our measurements are in good agreement with GEANT4 Monte Carlo simulations. (authors)

Vanstalle, M.; Husson, D.; Higueret, S.; Le, T. D.; Nourreddine, A. M. [Institut Pluridisciplinaire Hubert Curien, Univ. of Strasbourg, CNRS, 67037 Strasbourg (France)

2011-07-01

60

Thermoluminescence solid-state nanodosimetry--the peak 5A/5 dosemeter.  

PubMed

The shape of composite peak 5 in the glow curve of LiF:Mg,Ti (TLD-100) following (90)Sr/(90)Y beta irradiation, previously demonstrated to be dependent on the cooling rate used in the 400°C pre-irradiation anneal, is shown to be dependent on ionisation density in both naturally cooled and slow-cooled samples. Following heavy-charged particle high-ionisation density (HID) irradiation, the temperature of composite peak 5 decreases by ?5°C and the peak becomes broader. This behaviour is attributed to an increase in the relative intensity of peak 5a (a low-temperature satellite of peak 5). The relative intensity of peak 5a is estimated using a computerised glow curve deconvolution code based on first-order kinetics. The analysis uses kinetic parameters for peaks 4 and 5 determined from ancillary measurements resulting in nearly 'single-glow peak' curves for both the peaks. In the slow-cooled samples, owing to the increased relative intensity of peak 5a compared with the naturally cooled samples, the precision of the measurement of the 5a/5 intensity ratio is found to be ?15% (1 SD) compared with ?25% for the naturally cooled samples. The ratio of peak 5a/5 in the slow-cooled samples is found to increase systematically and gradually through a variety of radiation fields from a minimum value of 0.13±0.02 for (90)Sr/(90)Y low-ionisation density irradiations to a maximum value of ?0.8 for 20 MeV Cu and I ion HID irradiations. Irradiation by low-energy electrons of energy 0.1-1.5 keV results in values between 1.27 and 0.95, respectively. The increasing values of the ratio of peak 5a/5 with increasing ionisation density demonstrate the viability of the concept of the peak 5a/5 nanodosemeter and its potential in the measurement of average ionisation density in a 'nanoscopic' mass containing the trapping centre/luminescent centre spatially correlated molecule giving rise to composite peak 5. PMID:21149323

Fuks, E; Horowitz, Y S; Horowitz, A; Oster, L; Marino, S; Rainer, M; Rosenfeld, A; Datz, H

2010-12-13

61

Application Of The Thermoluminescent Dosemeters For The Measurement Of Low Level Background  

NASA Astrophysics Data System (ADS)

The results obtained in the measurement of the low level radiation background by using a thermoluminescent (TL) system, in a former salt mine, designed to be used as an underground laboratory , are presented.

Stochioiu, Ana I.; Sahagia, Maria C.; Mihai, Felicia S.; Tudor, Ion L.; Lupescu, Henrieta I.

2007-04-01

62

Test of Spectrometers and Dosemeters for the Investigation of the Radiation Environment onboard Spacecraft and around High Energy Accelerators  

Microsoft Academic Search

Neutron fields encountered around high-energy accelerators and on board spacecraft are both characterised by a broad spectral distribution extending from thermal energies to several hundred MeV. Therefore they pose a considerable challenge for appropriate monitoring of this component for radiation protection purposes on ground and in orbit. This is of particular importance for new accelerators like the upcoming FAIR project

Günther Reitz; Thomas Berger; Michelle Boudreau; Burkhard Wiegel; Marlies Luszik-Bhadra; Stefan Röttger; Ralf Nolte; Torsten Radon; Germany F. D. Smit

63

ABSORBED DOSE MEASUREMENTS OF A HANDHELD 50 kVP X-RAY SOURCE IN WATER WITH THERMOLUMINESCENCE DOSEMETERS  

Microsoft Academic Search

Absorbed dose rate measurements of a 50 kVp handheld X-ray probe source in a water phantom are described. The X-ray generator is capable of currents of up to 40 lA, and is designed for cranial brachytherapy and intraoperative applications with applicators. The measurements were performed in a computer-controlled water phantom in which both the source and the detectors are mounted.

Christopher Soares; Chris Drupieski; Brian Wingert; Garey Pritchett; Vasilis Pagonis; Michelle O'Brien; Alan Sliski; Pawel Bilski; Pawel Olko

64

Monte Carlo modelling and real-time dosemeter measurements of dose rate distribution at a 60Co industrial irradiation plant  

NASA Astrophysics Data System (ADS)

The dose rate distribution in a MDS Nordion JS7500 60Co industrial irradiation plant has been calculated using the egspp Monte Carlo code. This code is a development of the established EGSnrc code developed and distributed by National Research Council of Canada. The coding method is described and absolute dose rates given for each of the dwell positions in the path through the irradiator. These calculated dose rates have been compared with measurements made using a radiation resistant electronic dosimetry system. In addition, the integral dose derived from calculated and measured dose rates has been compared to the value obtained using chemical dosimeters.

Bailey, M.; Sephton, J. P.; Sharpe, P. H. G.

2009-07-01

65

Operational specifications of the L.I.T.E.S. (Laser Illuminated Track Etch Scattering) dosemeter reader  

Microsoft Academic Search

The Personnel Dosimetry Operations Team at the Los Alamos National Laboratory (LANL) has accepted the LITES dosimeter reader into its suite of radiation dose measurement instruments. The LITES instrument transmits coherent light from a HeNe laser through the pertinent track etch foil and a photodiode measures the amount of light scattered by the etched tracks. A small beam stop blocks

M. E. Moore; R. T. Devine; H. J. Gepford; R. J. McKeever; J. M. Hoffman

2004-01-01

66

Thermoluminescent characteristics of new pre-calibrated dosimeters (TLD) in commercially available readers for selected applications  

Microsoft Academic Search

This paper reports the performance of newly developed pre-calibrated Thermoluminescent Dosimeters (TLD) with a description and performance results for two commercially available TLD readers. Introduced for use in basic research, medical diagnostics and therapy applications, the Harshaw Model 5500 Automatic TLD Reader evaluates up to 50 dosimeters (rods, chips, disks, mu-cubes) per loading; the Harshaw Model 3500 Manual TLD Reader

R. A. Tawil; P. Pontikos; A. Szalanczy; K. Velbeck; W. Bruml; J. E. Rotunda

1994-01-01

67

Caracterizacion de un sistema de dosimetria personal termoluminiscente (UD-710A, UD-802, UD-875 Panasonic). (Characterization of a thermoluminiscence personnel dosimetry system).  

National Technical Information Service (NTIS)

Various tests carried out to characterize a Thermoluminiscence Personnel Dosimetry Automatic System, based on the optical heating of amultielement dosemeter are presented. The dosemeter consists of Lithium Borate (Copper) and Calcium Sulphate (Thallium) p...

C. Vazquez J. C. Saez T. Labarta

1989-01-01

68

Chemical and Structural Characterization of Thermally Degraded Black Chrome.  

National Technical Information Service (NTIS)

The very popular black chrome coating, Harshaw Chemical Company's Chromonyx, was characterized in terms of materials science to determine the nature of its microstructure and contribution to solar selectivity. The properties and degradation mode were reve...

C. M. Lampert J. Washburn

1980-01-01

69

Evaluation of Commercially Available TLD Readers.  

National Technical Information Service (NTIS)

The performance of two commercially available thermoluminescence bulb dosimetry systems, the Victoreen 2810 Ultra Sensitive TLD Reader and the Harshaw Model 2000P Bulb Dosimetry System, was investigated. Of primary interest was the reliability of the inst...

J. Gulbin G. de Planque

1981-01-01

70

Surface Analysis of a Deactivated Coal Liquifaction Catalyst.  

National Technical Information Service (NTIS)

Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (ESCA) have been used to study new and used coal liquefaction catalysts. By examining Harshaw 0402T cobalt and molybdenum oxide hydrodesulfurization catalyst with these and other analy...

P. H. Holloway D. K. Kramer

1977-01-01

71

Pulsed Microreactor Study of Catalyst Used in the Synthoil Process.  

National Technical Information Service (NTIS)

In studying the deactivation mechanisms of the Harshaw 0402T cobalt and molybdenum oxide catalyst used in the SYNTHOIL coal liquefaction reactor, a pulsed microreactor with a gas chromatography detection system has been found useful in measuring catalyst ...

D. M. Heinze

1977-01-01

72

The NRPB radon personal dosimetry service  

Microsoft Academic Search

A radon personal dosemeter has been developed. The dosemeter is simple, cheap, robust, disposable and indelibly numbered. The operation principle is that of a radon diffusion chamber, which principle has been established both experimentally and theoretically. The dosemeter is an enclosure which excludes radon progeny and detritus whilst allowing access of radon gas. The alpha particles from the decay of

D. T. Bartlett; P. J. Gilvin; R. Still; D. W. Dixon; J. C. H. Miles

1988-01-01

73

An evaluation of semiconductor and ionization chamber detectors for diagnostic x-ray dosimetry measurements  

Microsoft Academic Search

Dosemeters for performance testing of x-ray equipment may utilize semiconductor technology or ionization chambers (ICs). Semiconductor dosemeters incorporate several elements into the detectors from which compensation for variations in response with photon energy is derived. The design of the detectors influences their response with angle and this is different from that of ICs. The responses of semiconductor detectors (SDs) and

C J Martin

2007-01-01

74

DosiMir: Radiation measurements inside the Soviet Space Station Mir, first results  

Microsoft Academic Search

Two dosemeter packets containing Thermoluminescence Dosemeters (TLD's) and track etch foils were used to measure the absorbed dose and the average Linear Energy Transfer (LET) of the radiation within the Space Station Mir. One packet was exposed over a period of about 5 months and the other one during the Austria-Soviet manned space program in Oct. 1991. Various types of

N. Vana; W. Schoener; M. Fugger; J. A. Akatov

1992-01-01

75

Neutron Response of a New Albedo-Neutron Dosimeter.  

National Technical Information Service (NTIS)

The Los Alamos Scientific Laboratory is converting from a film badge to a badge containing thermoluminescent dosimeters (TLD's). The new dosimeter consists of a plastic badge holding an aluminum card which contains three TLD-700 and one TLD-600 Harshaw Li...

A. W. Blackstock J. R. Cortez G. J. Littlejohn E. Storm

1978-01-01

76

Evaluation of Spurious Readings in Los Alamos Personnel TL Dosimeters.  

National Technical Information Service (NTIS)

This study investigates the possibility of tritium build-up in TLD-600 chips irradiated with neutrons and the causes of spurious readings in the Harshaw TLD cards used for personnel dosimetry. Experiments indicated that spurious readings in TLD-600 chips,...

Y. Eisen G. J. Littlejohn J. R. Cortez

1984-01-01

77

Catalytic hydrogenation of coal-derived liquids. Interim report, December 1976February 1977  

Microsoft Academic Search

It is the objective of this research to convert coal to clean distillate fuels. This program will be limited to research on products from existing coal liquefaction processes. The results of batch tests of COED tar with sixteen different hydrocracking catalysts are reported as well as that from three catalysts tested in the continuous reactor. In a typical result Harshaw's

L. Berg; F. P. McCandless

1977-01-01

78

Catalyst development program for hydrodesulfurization and liquefaction of coal to produce clean boiler fuels. Quarterly report, December 1976February 1977  

Microsoft Academic Search

The first series of candidate catalysts has been identified for trial in the rapid screening reactor at Harshaw Chemical Company. The list is intended primarily as a survey of types with the intention to demonstrate that the screening tests show differences among these catalysts and to provide clues for development. A modified work plan has been adopted for the rapid

L. J. Hillenbrand; H. M. Grotta; G. W. Felton; W. R. Alcorn

1977-01-01

79

Alanine blends for ESR measurements of thermal neutron fluence in a mixed radiation field.  

PubMed

In this paper, the results of a study on the electron spin resonance (ESR) dosimetry to measure thermal neutron fluence in a mixed radiation field (neutron and photons) are presented. The ESR responses of alanine dosemeters with different additives are compared. In particular, the (10)B-acid boric and the Gd-oxide were chosen to enhance the sensitivity of alanine dosemeters to thermal neutrons. Irradiations were carried out inside the thermal column of the TAPIRO reactor of the ENEA center, Casaccia Rome. The main results are a greater neutron sensitivity and a smaller lowest detectable fluence for the dosemeters with gadolinium than for dosemeters of alanine with (10)B, which is well known to be much more sensitive to thermal neutrons than simple alanine. PMID:17517673

Marrale, M; Brai, M; Gennaro, G; Triolo, A; Bartolotta, A; D'Oca, M C; Rosi, G

2007-05-21

80

Evaluation of scattered neutrons in fast neutron calibration field using (sup 252)Cf and (sup 241)Am-Be neutron source.  

National Technical Information Service (NTIS)

The Facility of Radiation Standard of the Japan Atomic Energy Research Institute (FRS-JAERI) is equipped with a fast neutron calibration field in order to calibrate personnel dosemeters and surveymeters for neutron. This calibration field is produced with...

J. R. Dumais M. Yoshizawa Y. Yamaguchi

1998-01-01

81

Estudio y determinacion de las propiedades termoluminiscentes de un nuevo dosimetro de (sub alpha) -Al2O3:C. (Study and determination of thermoluminescent properties of a new dosemeter based on (sub (alpha)) -Al(sub 2)O(sub 3):C).  

National Technical Information Service (NTIS)

Study and determination of the thermoluminescent properties of a new dosimeter based on (sub (alpha)) -Al(sub 2)O(sub 3):C. Dosimetric characteristics studied were: glow curve structure, sensitivity, reproducibility, TL response as function of dose, and f...

T. Rivera Montalvo

1993-01-01

82

The Physical Measurements of Electron Beams from 6 to 18 Mev: Absorbed Dose and Energy Calibration  

Microsoft Academic Search

An aluminium calorimeter has been used to measure the G-values for the ferrous sulphate dosemeter for incident electron energies of 13·25, 15·9 and 18 Mev. The ferrous sulphate dosemeter was then used to determine the correction factor to be applied to an ion chamber reading taken in a Lucite phantom to obtain absorbed dose in water. The factor was found

Peter R Almond

1967-01-01

83

An investigation of false positive dosimetry results  

SciTech Connect

The Waste Isolation Pilot Plant (WIPP) is a facility designed for the demonstration of the safe disposal of transuranic waste. Currently, the radiation source term is confined to sealed calibration and check sources since WIPP has not received waste for disposal. For several years the WIPP Dosimetry Group has operated a Harshaw Model 8800C reader to analyze Harshaw 8801-7776 thermoluminescent cards (3 TLD-700 and 1 TLD-600) with 8805 holder. The frequency of false positive results for quarterly dosimeter exchanges is higher than desired by the Dosimetry Group management. Initial observations suggested that exposure to intense ambient sunlight may be responsible for the majority of the false positive readings for element 3. A study was designed to investigate the possibility of light leaking through the holder and inducing a signal in element 3. This paper discusses the methods and results obtained, with special emphasis placed on recommendations to reduce the frequency of light-induced false positive readings.

Lewandowski, M.A.; Davis, S.A.; Goff, T.E.; Wu, C.F.

1996-12-31

84

Thermoluminescent dosimeters (TLD) quality assurance network in the Czech Republic  

Microsoft Academic Search

Introduction: The Czech thermoluminescent dosimeters (TLD) quality assurance network was established in 1997. Its aim is to pursue a regular independent quality audit in Czech radiotherapy centres and to support state supervision.Materials and methods: The audit is realised via mailed TL dosimetry. The TLD system consists of encapsulated LiF:Mg,Ti powder (type MT-N) read with Harshaw manual reader model 4000. Basic

Daniela Kroutil??ková; Josef Novotný; Libor Judas

2003-01-01

85

The Urbach Tails and Reflection Spectra of NaCl Single Crystals  

Microsoft Academic Search

In the tail part region of the first exciton band, the absorption constant (10-1 to 102 cm-1) was measured on zone-refined and Harshaw NaCl single crystals from 10°K to 573°K. Fundamental absorption tails of pure NaCl single crystals are represented by the modified Urbach rule, which describes the influence of zero-point lattice vibrations at low temperature. Analysing a temperature dependence

Takeo Miyata; Tetsuhiko Tomiki

1967-01-01

86

Evaluation of commercially available TLD readers  

Microsoft Academic Search

The performance of two commercially available thermoluminescence bulb dosimetry systems, the Victoreen 2810 Ultra Sensitive TLD Reader and the Harshaw Model 2000P Bulb Dosimetry System, was investigaed. Of primary interest was the reliability of the instruments at an exposure range typically encountered in environmental radiation when monitoring on a monthly basis, i.e., approx. 10 mR. Uniformity, linearity, and reproducibility test

J. Gulbin; G. Deplanque

1981-01-01

87

The Development, Characterization, and Performance Evaluation of a New Combination Type Personnel Neutron Dosimeter  

Microsoft Academic Search

A new combination type personnel neutron dosimeter has been designed and developed at the Oak Ridge National Laboratory (ORNL). The combination personnel neutron dosimeter (CPND) consists of a Harshaw albedo neutron thermoluminescent dosimeter (two pairs of TLD-600\\/TLD-700) and two bubble detectors (one BD-100R and one BDS-1500 from Bubble Technology Industries, Canada). The CPND was developed with the aim of having

Chwei-Jeng Liu; Chweijeng

1989-01-01

88

Dosimetric study of thermoluminescent detectors in clinical photon beams using liquid water and PMMA phantoms.  

PubMed

The purpose of this study was the dosimetric evaluation of thermoluminescent detectors of calcium sulphate doped with dysprosium (CaSO4:Dy) produced by IPEN compared to the TL response of lithium fluoride doped with magnesium and titanium (LiF:Mg,Ti) dosimeters and microdosimeters produced by Harshaw Chemical Company to clinical photon beams dosimetry (6 and 15 MV) using liquid water and PMMA phantoms. PMID:22341404

Matsushima, Luciana C; Veneziani, Glauco R; Sakuraba, Roberto K; da Cruz, José C; Campos, Letícia L

2011-12-06

89

Continuous hydrogenation of vegetable oils in reactors equipped with static mixers  

Microsoft Academic Search

Continuous hydrogenation of industrially refined soybean oil with Harshaw Ni catalyst was achieved in a slurry column equipped\\u000a with Sulzer SMV motionless mixers. The influence of the operating parameters (temperature, pressure, catalyst concentration\\u000a and gas velocity) was investigated. The presumption that, in this equipment, the liquid-solid mass transfer limits the rate\\u000a of the process is in good agreement with the

Lucian M. Rusnac; Octavian Floarea; Radu V. Vladea

1992-01-01

90

Response of thermoluminescent dosimeters to photons simulated with the Monte Carlo method  

Microsoft Academic Search

Personal monitors composed of thermoluminescent dosimeters (TLDs) made of natural fluorite (CaF2:NaCl) and lithium fluoride (Harshaw TLD-100) were exposed to gamma and X rays of different qualities. The GEANT4 radiation transport Monte Carlo toolkit was employed to calculate the energy depth deposition profile in the TLDs. X-ray spectra of the ISO\\/4037-1 narrow-spectrum series, with peak voltage (kVp) values in the

M. Moralles; C. C. Guimarães; E. Okuno

2005-01-01

91

Nuclear-magnetic-resonance study of dislocation effects and axial compression effects in cesium iodide single crystals  

Microsoft Academic Search

The intensity of the 127I NMR in single crystals of CsI obtained from Harshaw Chemical Co. has been examined as a function of the orientation of the crystals with respect to the external magnetic field. The intensity varies due to the changing amount of first-order quadrupole broadening of the 127I NMR line as a crystal is rotated in the magnetic

G. R. Gerhart; H. O. Hooper

1974-01-01

92

Optimization of the photon response for a LiF thermoluminescent dosimeter  

SciTech Connect

A Harshaw LiF TLD card holder was optimized for maximum discrimination between different energies of irradiating photons in order to improve the dosimetric response. Since dose is proportional energy deposited, a theoretical model was created to estimate the TLD response by calculating the energy deposition. These results correlated with experimental data from NIST to within 20%. In order to increase the accuracy of the model, energy deposition calculations were made using the MCNP particle transport program. MCNP improved the correlation of the modeled data with the experimental data. Next, Harshaw`s 8825 card holder was optimized for photon energy determination by analyzing the card holder`s response with different filter materials and thickness. This analysis showed that increasing the copper filter thickness by 20 times and doubling the tin filter thickness compared to the original 8825 design improved the TLD`s photon energy determination response. The improved 8825 card holder was constructed and experiments were conducted at Armstrong Laboratories. The MCNP model predicted the experimental response of the card holder to within two standard deviations for all beams except M60. Finally, recommendations for a new card holder were made by Naval Dosimetry Center which included a modified filter for improved dose determination.

Carnell, R.C.

1998-12-31

93

Thermal neutron equivalent dose assessment around the KFUPM neutron source storage area using NTDs. King Fahd University of Petroleum and Minerals.  

PubMed

Area passive neutron dosemeters based on nuclear track detectors (NTDs) have been used for 13 days to assess accumulated low doses of thermal neutrons around neutron source storage area of the King Fahd University of Petroleum and Minerals (KFUPM). Moreover, the aim of this study is to check the effectiveness of shielding of the storage area. NTDs were mounted with the boron converter on their surface as one compressed unit. The converter is a lithium tetraborate (Li2B4O7) layer for thermal neutron detection via 10B(n,alpha)7Li and 6Li(n,alpha)3H nuclear reactions. The area passive dosemeters were installed on 26 different locations around the source storage area and adjacent rooms. The calibration factor for NTD-based area passive neutron dosemeters was found to be 8.3 alpha tracks x cm(-2) x microSv(-1) using active snoopy neutron dosemeters in the KFUPM neutron irradiation facility. The results show the variation of accumulated dose with locations around the storage area. The range of dose rates varied from as low as 40 nSvx h(-1) up to 11 microSv x h(-1). The study indicates that the area passive neutron dosemeter was able to detect accumulated doses as low as 40 nSv x h(-1), which could not be detected with the available active neutron dosemeters. The results of the study also indicate that an additional shielding is required to bring the dose rates down to background level. The present investigation suggests extending this study to find the contribution of doses from fast neutrons around the neutron source storage area using NTDs through proton recoil. The significance of this passive technique is that it is highly sensitive and does not require any electronics or power supplies, as is the case in active systems. PMID:12474945

Abu-Jarad, F; Fazal-ur-Rehman; Al-Haddad, M N; Al-jarallah, M I

2002-01-01

94

Different versions of the right answer: the importance of measurement uncertainty in radiation dosimetry.  

PubMed

The performance of radiation dosemeters that are issued by approved individual monitoring services generally meet international standards, with typical results within a few tens of per cent of the reference value. Experienced dosimetry practitioners will understand the uncertainties and treat monitoring results with due caution. However, where different technologies (for example, where passive and electronic dosemeters) are used side by side, apparent disagreements can arise. These apparent disagreements between different systems can be significant, and dosimetrists must be prepared to help in addressing the issues that result. PMID:20952420

Gilvin, Phil; McWhan, Andrew

2010-10-14

95

Dosimetry quality assurance in Martin Marietta Energy Systems' centralized external dosimetry system  

SciTech Connect

External dosimetry needs at the four Martin Marietta Energy Systems facilities are served by Energy Systems Centralized External Dosimetry System (CEDS). The CEDS is a four plant program with four dosimeter distribution centers and two dosimeter processing centers. Each plant has its own distribution center, while processing centers are located at ORNL and the Y-12 Plant. The program has been granted accreditation by the Department of Energy Laboratory Accreditation Program (DOELAP). The CEDS is a TLD based system which is responsible for whole-body beta-gamma, neutron, and extremity monitoring. Beta-gamma monitoring is performed using the Harshaw/Solon Technologies model 8805 dosimeter. Effective October 1, 1992 the standard silver mylar has been replaced with an Avery mylar foil blackened on the underside with ink. This was done in an effort to reduce the number of light induced suspect readings. At this time we have little operational experience with the new blackened mylars-The CEDS neutron dosimeter is the Harshaw model 8806B. This card/holder configuration contains two TLD-600/TLD-700 chip pairs; one pair is located beneath a cadmium filter and one pair is located beneath a plastic filter. In routine personnel monitoring the CEDS neutron dosimeter is always paired with a CEDS beta-gamma dosimeter.The CEDS extremity dosimeter is composed of a Harshaw thin TLD-700 dosiclip placed inside a Teledyne RB-4 finger sachet. The finger sachet provides approximately 7 mg/cm[sup 2] filtration over the chip. A teflon ring surrounds the dosiclip to help prevent tearing of the vinyl sachet.

Souleyrette, M.L.

1992-10-23

96

MEASUREMENTS OF THE EQUIVALENT DOSE IN AIRCRAFT WITH TLDS  

Microsoft Academic Search

For measurements of the equivalent dose of the mixed radiation fields in aircraft usually many different measuring devices are necessary for consideration of the different components of the radiation field. This work discusses the possibility of using thermoluminescence dosemeters (TLDs) for determination of absorbed dose and average LET of this complex radiation field in aircraft. The HTR-method, developed for determination

M. Noll; N. Vana; W. Schöner; M. Fugger

97

Dose measurements in space by the Hungarian Pille TLD system  

Microsoft Academic Search

Exposure of crew, equipment, and experiments to the ambient space radiation environment in low Earth orbit poses one of the most significant problems to long-term space habitation. Accurate dose measurement has become increasingly important during the assembly (extravehicular activity (EVA)) and operation of space stations such as on Space Station Mir.Passive integrating detector systems such as thermoluminescent dosemeters (TLDs) are

I Apáthy; S Deme; I Fehér; Y. A Akatov; G Reitz; V. V Arkhanguelski

2002-01-01

98

Alanine and TLD coupled detectors for fast neutron dose measurements in neutron capture therapy (NCT).  

PubMed

A method was investigated to measure gamma and fast neutron doses in phantoms exposed to an epithermal neutron beam designed for neutron capture therapy (NCT). The gamma dose component was measured by TLD-300 [CaF2:Tm] and the fast neutron dose, mainly due to elastic scattering with hydrogen nuclei, was measured by alanine dosemeters [CH3CH(NH2)COOH]. The gamma and fast neutron doses deposited in alanine dosemeters are very near to those released in tissue, because of the alanine tissue equivalence. Couples of TLD-300 and alanine dosemeters were irradiated in phantoms positioned in the epithermal column of the Tapiro reactor (ENEA-Casaccia RC). The dosemeter response depends on the linear energy transfer (LET) of radiation, hence the precision and reliability of the fast neutron dose values obtained with the proposed method have been investigated. Results showed that the combination of alanine and TLD detectors is a promising method to separate gamma dose and fast neutron dose in NCT. PMID:15353722

Cecilia, A; Baccaro, S; Cemmi, A; Colli, V; Gambarini, G; Rosi, G; Scolari, L

2004-01-01

99

DETERMINATION OF THE ABSORBED DOSE AND THE AVERAGE LET OF SPACE RADIATION IN DEPENDENCE OF SHIELDING CONDITIONS  

Microsoft Academic Search

The HTR-method, developed for determination of absorbed dose and average LET of mixed radiation fields in space, was applied during several space missions on space station MIR, space shuttles and satellites. The method utilizes the changes of peak height ratios in the glowcurves in dependence on the linear energy transfer LET. Due to the small size of the dosemeters the

N. Vana; W. Schöner; M. Noll; M. Fugger; Y. Akatov; V. Shurshakov

100

Correlation of patient skin doses in cardiac interventional radiology with dose-area product  

Microsoft Academic Search

The use of X-rays in cardiac interventional radiology has the potential to induce deterministic radiation effects on the patient's skin. Guidelines published by official organizations encourage the recording of information to evaluate this risk, and the use of reference values in terms of the dose-area product (DAP). Skin dose measurements were made with thermo- luminescent dosemeters placed at eight different

S VAN DE PUTTE; F VERHAEGEN; Y TAEYMANS; H THIERENS

101

Measurements of individual doses from external radiation in the Brjansk region of the Russian republic of the USSR.  

National Technical Information Service (NTIS)

Individual doses from external photon radiation to various occupational groups in three different villages in the Brjansk region of the Russian republic of the USSR have been measured by individual TL-dosemeters. A total of 86 persons were monitored for a...

E. Wallstroem T. Woehni

1991-01-01

102

Recent achievements in external radiation dosimetry  

Microsoft Academic Search

Some of the more relevant recent achievements and developments in the field of external radiation dosimetry are reviewed in this presentation. Among them, topics related to personal dosimetry, as the relative role of active and passive methods and the features of some recently proposed new methods. Electronic personal dosemeters and Optically Stimulated Luminescence, OSL, have already accredited their adequacy for

Antonio Delgado

103

DETERMINATION OF THE RADIATION ENVIRONMENT ON TOP OF HIGH ALTITUDE MOUNTAINS  

Microsoft Academic Search

Bonner Sphere Spectrometers (BSS) with a 6LiI(Eu) scintillation counter and thermoluminescent dosemeters (TLDs), respectively, were used to determine the absorbed dose and the average LET in a complex mixed radiation field on top of Mt. Sonnblick (3105 m). Special interest was laid on the determination of the neutron spectrum because of the contribution of neutrons to the biologically relevant dose

M. Noll; W. Schöner; N. Vana; M. Hajek; M. Minarik; T. Berger

104

Review of radiological physics, dosimetry and biology research at the University of Wisconsin during 1961-1984  

SciTech Connect

This report provides a comprehensive review of the overall activities in this program since its inception in 1961. The most consequential development was the development of lithium fluoride as a thermoluminescent dosemeter (TLD). Also studied were the potentialities of ionization chambers for use in personnel neutron dosimetry and applied microdosimetric research. (ACR)

Cameron, J.R.; Moran, P.R.; Attix, F.H.; DeLuca, P.M. Jr.

1984-01-01

105

Study of the improvement of TLD cards for personal neutron dosimetry  

NASA Astrophysics Data System (ADS)

In this work, personal thermoluminescence dosimeter (TLD) cards type of GN-6770 (holder type 8806) from Harshaw were used for personal neutron dosimetry. The response of the dosimeters has been determined in terms of the personal absorbed dose and personal dose equivalent for different neutron energy components, based on the recommendations of ICRP-60 and ICRU-49. Neutron irradiation was performed using a 5 mCi Am-Be neutron source. The TLD reader, type Harshaw 6600, was installed and calibrated for accurate neutron doses equivalent to gamma-ray doses. It was found that fast neutron doses measured by TLD (badges or cards) are in agreement with those measured by neutron TE (tissue equivalent gas) ionization chambers and neutron monitors. Thermal neutron doses measured by TLD cards were overestimated when compared with those measured by neutron monitors. Additional Cd was used to reduce thermal neutron doses to be in agreement with actual thermal doses. Other configurations for TLD crystals are also suggested for accurate thermal neutron dose measurements.

Rabie, N.; Hassan, G. M.; El-Sersy, A. R.; Ezzat, M.

106

Catalytic methods for improved coal liquefaction and hydrotreating: Quarterly report No. 6 for the period December 23, 1986 through March 22, 1987  

SciTech Connect

During this quarter we synthesized two new ruthenium catalysts. The first catalyst, Ru/sub 3/(CO)/sub 12/ supported on alumina, Ru(OM), was prepared to compare the reactivity of supported ruthenium carbonyl with that of bulk ruthenium, and with the RuMo(OM) catalyst prepared last quarter. The second catalyst was a RuCoMo catalyst prepared from the promotion of sulfided Harshaw CoMo with ruthenium trichloride, rather than with ruthenium carbonyl, which was used in previous preparations. We found that the ruthenium supported on alumina, Ru(OM), had the same activity and selectivity as bulk ruthenium, and was totally poisoned by hydrogen sulfide, as was the bulk metal. We also found that the RuCoMo prepared by ruthenium trichloride promotion had a similar activity and selectivity as the RuCoMo catalyst prepared by ruthenium carbonyl impregnation. Comparisons of the CoMo and RuCoMo catalysts were made on the HDN of decahydroquinoline (DHQ). We found in both cases the HDN product was almost exclusively propylcyclohexane, showing that the formation of propylbenzene during the HDN of quinoline must come from propylaniline or benzotetrahydroquinoline. We also compared the surface areas and pore sizes of the Harshaw CoMo and promoted RuCoMo catalysts and found them very similar. This quarter we presented a summary of our work on our use of organometallic precursors and promoted RuCoMo catalysts at the Denver ACS meeting. 4 refs.

Hirschon, A.S.; Laine, R.M.; Wilson, R.B. Jr.

1987-04-01

107

Personal dose equivalent angular response factors for photons with energies up to 1 GeV.  

PubMed

When performing personal dosemeter calibrations, the dosemeters are typically irradiated while mounted on slab-type phantoms and oriented facing the source. Performance testing standards or intercomparison studies may also specify various rotational angles to test the response of the dosemeter and associated algorithm as this rotation introduces changes in the quantity of delivered dose. Correction factors for rotational effects are available, but many have not been updated in recent years and were typically calculated using the kerma approximation. The personal dose equivalent, Hp(d), is the quantity recommended by the International Commission on Radiation Units and Measurements to be used as an approximation of the protection quantity effective dose when performing personal dosemeter calibrations. The personal dose equivalent can be defined for any location and depth within the body, but typically the location of interest is the trunk where personal dosemeters are worn and in this instance a suitable approximation is a 30 cm × 30 cm × 15 cm slab-type phantom. In this work personal dose equivalent conversion coefficients for photons with energies up to 1 GeV have been calculated for depths of 0.007, 0.3 and 1.0 cm in the slab phantom for rotational angles ranging from 15° to 75°. Angular response factors have been determined by comparing the conversion coefficients for each angle and energy to those reported in an earlier work for a non-rotational (e.g. perpendicular to the phantom face) geometry. The angular response factors were determined for discrete angles, but fits of the factors are provided. PMID:22914333

Veinot, K G

2012-08-22

108

Tenth ORNL Personnel Dosimetry Intercomparison Study  

SciTech Connect

The Tenth Personnel Dosimetry Intercomparison Study was conducted at the Oak Ridge National Laboratory during April 9-11, 1984. Dosemeter badges from 31 participating organizations were mounted on 40cm Lucite phantoms and exposed to a range of dose equivalents which could be encountered during routine personnel monitoring in mixed radiation fields. The Health Physics Research Reactor served as the only source of radiation for eight of the ten irradiations which included a low (approx. 0.50 mSv) and high (approx. 10.00 mSv) neutron dose equivalent run for each of four shield conditions. Two irradiations were also conducted for which concrete- and Lucite-shield reactor irradiations were gamma-enhanced using a /sup 137/Cs source. Results indicated that some participants had difficulty obtaining measurable indication of neutron and gamma exposures at dose equivalents less than about 0.50 mSv and 0.20 mSv, respectively. Albedo dosemeters provided the best overall accuracy and precision for the neutron measurements. Direct interaction TLD systems showed significant variation in accuracy with incident spectrum, and threshold neutron dosemeters (film and recoil track) underestimated reference values by more than 50%. Gamma dose equivalents estimated in the mixed fields were higher than reference values with TL gamma dosemeters generally yielding more accurate results than film. Under the conditions of this study in which participants had information concerning exposure conditions and radiation field characteristics prior to dosemeter evaluation, only slightly more than half of all reported results met regulatory standards for neutron and gamma accuracy. 19 refs., 2 figs., 29 tabs.

Swaja, R.E.; Chou, T.L.; Sims, C.S.; Greene, R.T.

1985-03-01

109

Characterisation of the TAPIRO BNCT epithermal facility.  

PubMed

A collimated epithermal beam for boron neutron capture therapy (BNCT) research has been designed and built at the TAPIRO fast research reactor. A complete experimental characterisation of the radiation field in the irradiation chamber has been performed, to verify agreement with IAEA requirements. Slow neutron fluxes have been measured by means of an activation technique and with thermoluminescent detectors (TLDs). The fast neutron dose has been determined with gel dosemeters, while the fast neutron spectrum has been acquired by means of a neutron spectrometer based on superheated drop detectors. The gamma-dose has been measured with gel dosemeters and TLDs. For an independent verification of the experimental results, fluxes, doses and neutron spectra have been calculated with Monte Carlo simulations using the codes MCNP4B and MCNPX_2.1.5 with the direct statistical approach (DSA). The results obtained confirm that the epithermal beams achievable at TAPIRO are of suitable quality for BNCT purposes. PMID:15353724

Burn, K W; Colli, V; Curzio, G; d'Errico, F; Gambarini, G; Rosi, G; Scolari, L

2004-01-01

110

Characterisation of the TAPIRO BNCT thermal facility.  

PubMed

Dosimetry and spectrometry measurements have been carried out in the thermal column of the research fast reactor RSV-TAPIRO (ENEA-Casaccia, Rome) in order to investigate its suitability for irradiation of cells or mice, with a view to research in the interests of boron neutron capture therapy (BNCT). The thermal column consists of a graphite moderator (40 cm thick) containing a lead shield (13 cm thick) in order to shield reactor background. The irradiation volume, inside this structure, has cubic shape (18 x 18 x 18 cm3). Besides measurements of fluence and dose rates in air or in phantom performed with thermoluminescence dosemeters (TLDs) and using the activation technique, dose and fluence profiles have been generated using a method based on gel dosemeters analysed with optical imaging. To check the consistency of the results, spectrometry measurements in the same irradiation volume have been performed by means of bubble detectors. PMID:15353725

Rosi, G; Gambarini, G; Colli, V; Gay, S; Scolari, L; Fiorani, O; Perrone, A; Nava, E; Fasolo, F; Visca, L; Zanini, A

2004-01-01

111

Content of uranium in urine of uranium miners as a tool for estimation of intakes of long-lived alpha radionuclides.  

PubMed

Uranium in the urine of 10 uranium miners (hewers), 27 members of general population and 11 family members of miners was determined by the High-Resolution ICP-MS method. Concentration of uranium in urine of the miners was converted to daily excretion of (238)U under the assumption that the daily excretion of urine is 2 l and compared with the modelled excretion of (238)U. Daily excretion of (238)U was modelled using input data from personal dosemeters from a component for measurement of intake of long-lived alpha radionuclides. A reasonable agreement between evaluated and measured values was found. The uncertainty of inhalation intakes, derived from measurements of filters from personal dosemeters, and uncertainty of concentration of uranium in urine are discussed. PMID:21208936

Malátová, I; Becková, V; Tomásek, L; Hulka, J

2011-01-04

112

A A field test for extremity dose assessment during outages at Korean nuclear power plants.  

PubMed

During maintenance on the water chamber of a steam generator, the pressuriser heater and the pressure tube feeder in nuclear power plants, workers are likely to receive high radiation doses due to the severe workplace conditions. In particular, it is expected that workers' hands would receive the highest radiation doses because of their contact with the radioactive materials. In this study, field tests for extremity dose assessments in radiation workers undertaking contact tasks with high radiation doses were conducted during outages at pressurised water reactors and pressurised heavy water reactors in Korea. In the test, the radiation workers were required to wear additional thermoluminescent dosemeters (TLDs) on their backs and wrists and an extremity dosemeter on the finger, as well as a main TLD on the chest while performing the maintenance tasks. PMID:23091221

Kim, Hee Geun; Kong, Tae Young

2012-10-22

113

A comparison of different neutron spectroscopy systems at the reactor facility VENUS  

NASA Astrophysics Data System (ADS)

The VENUS facility is a zero-power research reactor mainly devoted to studies on LWR fuels. Localised high-neutron rates were found around the reactor, with a neutron/gamma dose equivalent rate ratio as high as three. Therefore, a study of the neutron dosimetry around the reactor was started some years ago. During this study, several methods of neutron spectroscopy were employed and a study of individual and ambient dosemeters was performed. A first spectrometric measurement was done with the IPSN multisphere spectrometer in three positions around the reactor. Secondly, the ROSPEC spectrometer from the Fraunhofer Institut was used. The spectra were also measured with the bubble interactive neutron spectrometer. These measurements were compared with a numerical simulation of the neutron field made with the code TRIPOLI-3. Dosimetric measurements were made with three types of personal neutron dosemeters: an albedo type, a track etch detector and a bubble detector.

Vanhavere, F.; Vermeersch, F.; Chartier, J. L.; Itié, C.; Rosenstock, W.; Köble, T.; d'Errico, F.

2002-01-01

114

Temperature response of a number of plastic dosimeters for radiation processing  

NASA Astrophysics Data System (ADS)

Various plastic dosemeters are employed for dosimetry control of radiation processing within gamma and electron irradiation facilities. The temperature response of a dosimeter is important when the dose to such a dosimeter is accumulated under varying irradiation temperatures. Such measurements would be significant for proper assessment of the dose for better process control, as well as, performance evaluation of dosimetry systems. In this work we have developed a high current peltier junction temperature controller system for our Gammacell-220. This system has been designed to regulate the operating temperature of the irradiation chamber in the range of 0 to 80 C this system has been applied to measure the temperature response of the red perspex, a local clear PMMA, Gammex, Gammachrome, and Gafchromic dosimeters. The curves of relative performance or variation of the induced optical densities of the above dosemeters versus the irradiation temperature at fixed dose values are obtained.

Sohrabpour, M.; Kazemi, A. A.; Mousavi, H.; Solati, K.

1993-10-01

115

Fricke gel dosimetry in boron neutron capture therapy.  

PubMed

Gel dosimetry allows three-dimensional (3D) measurement of absorbed dose in tissue-equivalent dosemeter phantoms. Gel phantoms are imaged using optical techniques. In neutron capture therapy (NCT), properly designed gel dosemeters can give 3D dose distributions, due to the various components of the secondary radiation, in phantoms exposed in the thermal or epithermal column of a nuclear reactor. In addition to the therapeutic dose arising from the reaction 10B(n,alpha)7Li, the other dose components are also obtainable, i.e. the gamma dose (due to reactor background and to the reaction 1H(n,gamma)2H of thermal neutrons with hydrogen, the dose due to protons emitted in the reaction 14N(n,p)14C of thermal neutrons with nitrogen and the dose due to recoil protons resulting from elastic scattering of epithermal neutrons. PMID:12382781

Gambarini, G; Birattari, C; Colombi, C; Pirola, L; Rosi, G

2002-01-01

116

A method to characterise site, urban and regional ambient background radiation.  

PubMed

Control dosemeters are routinely provided to customers to monitor the background radiation so that it can be subtracted from the gross response of the dosemeter to arrive at the occupational dose. Landauer, the largest dosimetry processor in the world with subsidiaries in Australia, Brazil, China, France, Japan, Mexico and the UK, has clients in approximately 130 countries. The Glenwood facility processes over 1.1 million controls per year. This network of clients around the world provides a unique ability to monitor the world's ambient background radiation. Control data can be mined to provide useful historical information regarding ambient background rates and provide a historical baseline for geographical areas. Historical baseline can be used to provide site or region-specific background subtraction values, document the variation in ambient background radiation around a client's site or provide a baseline for measuring the efficiency of clean-up efforts in urban areas after a dirty bomb detonation. PMID:20959341

Passmore, C; Kirr, M

2010-10-19

117

Establishment of radiation qualities for mammography according to the IEC 61267 and TRS 457.  

PubMed

This article presents the technical conditions necessary to establish appropriate radiation qualities for the calibration of the dosemeters used in the mammography detectors in the Laboratório de Ciências Radiológicas (LCR) from the Universidade do Estado do Rio de Janeiro. Tests were conducted to evaluate the homogeneity of the radiation field, scattering, half-value layers and system stability. The calibration method (substitution) is described in this work. A moderate alteration in filtration makes it possible to maintain the half-value layers within the limits recommended. The results indicate the adequacy of the LCR laboratory for the calibration of the dosemeters in the radiation qualities for mammography with an expanded uncertainty in the best measurement capability of ± 1.8 % (k = 2). PMID:21062803

Pires, Evandro J; David, Mariano G; Peixoto, J Guilherme; Dealmeida, Carlos E

2010-11-09

118

The importance of the direction distribution of neutron fluence, and methods of determination  

NASA Astrophysics Data System (ADS)

For the estimation of non-isotropic quantities such as personal dose equivalent and effective dose, and for the interpretation of the readings of personal dosemeters, it is necessary to determine both the energy and direction distributions of the neutron fluence. In fact, for workplace fields, the fluence and dose-equivalent responses of dosemeters and the relationships of operational and protection quantities, are frequently more dependent on the direction than on the energy distribution. In general, the direction distribution will not be independent of the energy distribution, and simultaneous determination of both may be required, which becomes a complex problem. The extent to which detailed information can be obtained depends on the spectrometric properties and on the angle dependence of the response of the detectors used. Methods for the determination of direction distributions of workplace fields are described.

Bartlett, D. T.; Drake, P.; d'Errico, F.; Luszik-Bhadra, M.; Matzke, M.; Tanner, R. J.

2002-01-01

119

A multi-detector neutron spectrometer with nearly isotropic response for environmental and workplace monitoring  

NASA Astrophysics Data System (ADS)

This communication describes an improved design for a neutron spectrometer consisting of 6Li thermoluminescent dosemeters located at selected positions within a single moderating polyethylene sphere. The spatial arrangement of the dosemeters has been designed using the MCNPX Monte Carlo code to calculate the response matrix for 56 log-equidistant energies from 10-9 to 100 MeV, looking for a configuration that permits to obtain a nearly isotropic response for neutrons in the energy range from thermal to 20 MeV. The feasibility of the proposed spectrometer and the isotropy of its response have been evaluated by simulating exposures to different reference and workplace neutron fields. The FRUIT code has been used for unfolding purposes. The results of the simulations as well as the experimental tests confirm the suitability of the prototype for environmental and workplace monitoring applications.

Gómez-Ros, J. M.; Bedogni, R.; Moraleda, M.; Delgado, A.; Romero, A.; Esposito, A.

2010-01-01

120

A whole-body dosimetry system for personal monitoring based on hot-pressed thin layer TLD.  

PubMed

We are introducing a new high-capacity thermoluminescent dosemeter (TLD) system to measure the whole body values of H(p)(10) and H(p)(0.07) from photons for use in individual monitoring services. Small and light-weight badges allow a convenient application in a wide variety of workplaces with photon radiation from 20 keV to at least 7 MeV. The main advantage of this system will be the large capacity of ? 100,000 dosemeters per month at costs equivalent to the current film monitoring. The hot-pressed thin-layer TL detector (LiF:Mg,Ti) is welded onto an aluminium substrate and provided with a data matrix code for automatic processing. The detector holder has been optimised, that no additional filter is necessary. The new designed TLD reader with readout times <10 s will allow a large throughput and a considerable degree of automation. PMID:21227958

Busch, F; Engelhardt, J; Martini, E; Lesz, J

2011-01-11

121

Dose reduction to radiosensitive tissues in CT. Do commercially available shields meet the users' needs?  

Microsoft Academic Search

AIM: To assess the effectiveness and economy of routinely using commercially available in-plane bismuth shielding during CT scanning of the chest and brain.METHODS AND MATERIALS: Forty patients were scanned with thermoluminescent dosemeters (TLDs) in situ to measure the radiation dose to the thyroid and eye during CT scanning of the brain and chest. Half of the patients had the “AttenuRad”

D. J McLaughlin; R. B Mooney

2004-01-01

122

Monitoring the eye lens: which dose quantity is adequate?  

NASA Astrophysics Data System (ADS)

Recent epidemiological studies suggest a rather low dose threshold (below 0.5 Gy) for the induction of a cataract of the eye lens. Some other studies even assume that there is no threshold at all. Therefore, protection measures have to be optimized and current dose limits for the eye lens may be reduced in the future. The question of which personal dose equivalent quantity is appropriate for monitoring the dose to the eye lens arises from this situation. While in many countries dosemeters calibrated in terms of the dose equivalent quantity Hp(0.07) have been seen as being adequate for monitoring the dose to the eye lens, this might be questionable in the case of reduced dose limits and, thus, it may become necessary to use the dose equivalent quantity Hp(3) for this purpose. To discuss this question, the dose conversion coefficients for the equivalent dose of the eye lens (in the following eye lens dose) were determined for realistic photon and beta radiation fields and compared with the values of the corresponding conversion coefficients for the different operational quantities. The values obtained lead to the following conclusions: in radiation fields where most of the dose comes from photons, especially x-rays, it is appropriate to use dosemeters calibrated in terms of Hp(0.07) on a slab phantom, while in other radiation fields (dominated by beta radiation or unknown contributions of photon and beta radiation) dosemeters calibrated in terms of Hp(3) on a slab phantom should be used. As an alternative, dosemeters calibrated in terms of Hp(0.07) on a slab phantom could also be used; however, in radiation fields containing beta radiation with the end point energy near 1 MeV, an overestimation of the eye lens dose by up to a factor of 550 is possible.

Behrens, R.; Dietze, G.

2010-07-01

123

The use of gel dosimetry to measure the 3D dose distribution of a 90Sr\\/90Y intravascular brachytherapy seed  

Microsoft Academic Search

Absorbed dose distributions in 3D imparted by a single 90Sr\\/90Y beta particle seed source of the type used for intravascular brachytherapy were investigated. A polymer gel dosimetry medium was used as a dosemeter and phantom, while a special high-resolution laser CT scanner with a spatial resolution of 100 µm in all dimensions was used to quantify the data. We have

G Massillon-JL; R Minniti; M G Mitch; M J Maryanski; C G Soares

2009-01-01

124

On the linearity of the high-temperature emission from 7LiF:Mg,Ti (TLD700)  

Microsoft Academic Search

It is known since the early 1970s [e.g., Jähnert, B., 1972. The response of TLD-700 thermoluminescent dosemeters to protons and alpha particles. Health Phys. 23, 112–114.] that the high-temperature emission (HTE) from LiF:Mg,Ti thermoluminescence (TL) phosphors shows a distinctly different LET dependence than the dominant glow peak 5. This behaviour of the high-temperature structure can be attributed to the earlier

T. Berger; M. Hajek

2008-01-01

125

Implementation of an electronic personal dosimetry system (EPD) at Oldbury-on-Severn power station.  

PubMed

This article presents the implementation of an electronic personal dosemeter (EPD) as a film badge replacement at Oldbury-on-Severn power station, which is the first major site to use an approval issued by the UK Health and Safety Executive (HSE) for dose measurement by an EPD. The practicalities and history behind the introduction of an EPD for personal dosimetry are described. PMID:11281529

Clarke, P W; Weeks, A R

2001-03-01

126

IEC standards for individual monitoring of ionising radiation.  

PubMed

This paper presents IEC/SC 45B 'Radiation protection instrumentation' and its standards for individual monitoring of ionising radiation: IEC 61526 Ed. 3 for active personal dosemeters and IEC 62387-1 for passive integrating dosimetry systems. The transposition of these standards as CENELEC (European) standards is also discussed together with the collaboration between IEC/SC 45B and ISO/TC 85/SC 2. PMID:21098629

Voytchev, M; Ambrosi, P; Behrens, R; Chiaro, P

2010-11-23

127

Radon contamination of natural gas in a storage cavern  

Microsoft Academic Search

Measurements of radon concentration in air and of the radon exhalation rate were made in an underground storage cavern for natural gas. Relatively good agreement was observed between the average radon concentration calculated from the radon exhalation rate data (5 kBq m?3) and the average radon concentration measured using two different techniques (electret dosemeters: 7.2 kBq m?3; Lucas cells: from

J. Thomas

1996-01-01

128

Evaluation of factors to convert absorbed dose calibrations from graphite to water for the NPL high-energy photon calibration service  

Microsoft Academic Search

The National Physical Laboratory (NPL) provides a high-energy photon calibration service using 4-19 MV x-rays and 60Co gamma-radiation for secondary standard dosemeters in terms of absorbed dose to water. The primary standard used for this service is a graphite calorimeter and so absorbed dose calibrations must be converted from graphite to water. The conversion factors currently in use were determined

R. F. Nutbrown; S. Duane; D. R. Shipley; R. A. S. Thomas

2002-01-01

129

Optimum parameters of TLD100 powder used for radiotherapy beams calibration check  

SciTech Connect

External audit of the absorbed dose determination from radiotherapy machines is performed using Lithium fluoride (LiF) TLD-100. Optimal parameters needed to obtain highly accurate dosage from LiF powder was investigated, including the setup of the Harshaw 4000 reader. A linear correspondence between the thermoluminescent signal and the mass of the powder was observed, demonstrating that the dose can be evaluated with small samples of powder. The reproducibility of the thermoluminescence dosimeter (TLD) readings obtained with up to 10 samples from 1 capsule containing 160 mg of powder was around 1.5% (1 standard deviation [SD]). The time required for the manual evaluation of TLDs can be improved by 3 readings without loss of accuracy. Better reproducibility is achieved if the capsules are evaluated 7 days after irradiation using a nitrogen flow of 300 cc/min.

Arib, M. [Laboratoire Secondaire des Etalons en Dosimetrie, Centre de Recherche Nucleaire d'Alger, Alger Gare (Algeria)]. E-mail: mehenna.arib@comena-dz.org; Yaich, A. [Laboratoire Secondaire des Etalons en Dosimetrie, Centre de Recherche Nucleaire d'Alger, Alger Gare (Algeria); Messadi, A. [Laboratoire Secondaire des Etalons en Dosimetrie, Centre de Recherche Nucleaire d'Alger, Alger Gare (Algeria); Dari, F. [Laboratoire Secondaire des Etalons en Dosimetrie, Centre de Recherche Nucleaire d'Alger, Alger Gare (Algeria)

2006-10-01

130

Thermal expansion measurements on four optical materials from room temperature to 10 k.  

PubMed

In a continuing study of the physical properties of optical materials, measurements are reported of the linear thermal expansion coefficients for four ir-transmitting materials in the temperature range 10-300 K. A new glass and three polycrystalline materials were investigated by use of a three-terminal capacitance- type dilatometer incorporated into a cryostat. The glass, designated No. 20 by Texas Instruments, Inc., is a nonoxide chalcogenide glass with the composition Ge(33)Se(55)As(l2). One of the po]ycrystalline materials studied, T-12 (Harshaw Chemical Co.), is an optically integral two-phase material composed of equal molar proportions of CaF(2) and BaF(2). The other two materials are microcrystalline, hot-pressed forms of CdS and CdTe (Irtran 6), manufactured by the Eastman Kodak Co. PMID:20119054

Browder, J S; Ballard, S S

1972-04-01

131

Heating Rate Effects on Thermoluminescence of BaSO4:Eu+PTFE Prepared at Inin-Mexico  

NASA Astrophysics Data System (ADS)

In this work, we show the influence of heating rate (H.R.) on the thermoluminescence (TL) signal of BaSO4 activated by Eu ions. The maximum temperature, the TL integral, the activation energy, the frequency factor and full width at half maximum of the TL glow-peak as a function of the H.R. were studied. The TL reading system used was a Harshaw TL reader model 4000, with constant H.R. in the range from 2 to 12 K/s. The irradiation dose was 0.1 Gy from 60Co in all cases. The kinetic parameters and their dependence on the H.R. were evaluated using the sequential quadratic programming glow curve deconvolution (SQPGCD). The experimental results showed that as the H.R. increases, the IM shifts to higher temperature; similar behavior of the kinetics parameters were obtained.

Gonzalez, P. R.; Furetta, C.; Cruz-Zaragoza, E.; Azorín, J.

132

ESR and TL dosimetry systems: comparative measurements for human phantom.  

PubMed

Mixtures of small fragments of tooth enamel as well as thermoluminescence (TL) dosimeters were placed into the tissue-equivalent phantom of the human head with skeleton (approximately at the level of the jaws) and irradiated using 137Cs low dose-rate gamma therapeutic sources ('SELEKTRON' LDR 137Cs). Phantom, samples of teeth and TL detectors were irradiated behind water tank to produce scattered irradiation. The same irradiation with the same geometry was performed in air too. For gamma-spectrometry 137Cs sources with very low activity were used but with the same geometry as therapeutic sources. The absorbed dose in enamel was estimated with the help of ESR spectrometer 'ESP-300 E' (Brucker). The samples of tooth enamel were partially used for preliminary dose evaluation by ESR signal before starting of experiment. TL dosimetry was performed by TL reader model 8800 (HARSHAW) using TL dosimeters calibrated with 137Cs. The paper presents data obtained in comparative aspects. PMID:9022197

Stepanenko, V F; Skvortsov, V G; Ivannikov, A I; Kondrashov, A E; Vaichulis, P P; Denisenko, O N; Kozlov, V A; Khamidova, L G; Tikunov, D D; Panfilov, A P; Eichhozff, U

133

Preirradiation sensitivity loss of reader-annealed LiF TLDs  

SciTech Connect

Yankee Atomic Electric Company (YAEC) maintains a thermoluminescent dosimeter (TLD) dosimetry service using a Harshaw TLD badge system consisting of two TLD cards in a plastic case and automatic 2271 readers. Beginning in 1986, a standardized on-site quality assurance testing program was instituted for the facilities provided with YAEC personnel dosimetry. Results obtained during the first half of 1986 indicated a low bias in test TLD results on the order of 10 to 15%. A subsequent investigation attributed this bias to a previously unidentified loss in the sensitivity of reader-annealed LiF TLDs with storage time prior to irradiation. The discovery of this effect, based on in-plant quality assurance testing, demonstrates the usefulness of even relatively simple quality assurance tests by users themselves, regardless of the apparent thoroughness of other testing.

Poeton, R.W.; Stanford, N.; Scannel, M.J.

1987-01-01

134

Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part I: Scope and methods of the project.  

PubMed

Supported by the European Commission, the EVIDOS project started in November 2001 with the broad goal of evaluating state of the art dosimetry techniques in representative workplaces of the nuclear industry. Seven European institutes joined efforts with end users at nuclear power plants, at fuel processing and reprocessing plants, and at transport and storage facilities. A comprehensive programme was devised to evaluate capabilities and limitations of standard and innovative personal dosemeters in relation to the mixed neutron-photon fields of concern to the nuclear industry. This paper describes the criteria behind the selection of dosimetry techniques and workplaces that were analysed, as well as the organisation of the measurement campaigns. Particular emphasis was placed on the evaluation of a variety of electronic personal dosemeters, either commercially available or previously developed by the partners. The estimates provided by these personal dosemeters were compared to reference values of dose equivalent quantities derived from spectrometry and fluence-to-dose equivalent conversion coefficients. Spectrometry was performed both with conventional multisphere and with some original instrumentation providing energy and direction resolution, based on silicon detectors and superheated drop detectors mounted on or in spherical moderators. The results were collected in a large, searchable database and are intended to be used in the harmonisation of dosimetric procedures for mixed radiation fields and for the approval of dosimetry services in Europe. PMID:17522043

d'Errico, F; Bartlett, D; Bolognese-Milsztajn, T; Boschung, M; Coeck, M; Curzio, G; Fiechtner, A; Kyllönen, J-E; Lacoste, V; Lindborg, L; Luszik-Bhadra, M; Reginatto, M; Schuhmacher, H; Tanner, R; Vanhavere, F

2007-05-22

135

Electronic neutron personal dosimetry with superheated drop detectors.  

PubMed

The prototype of an electronic personal neutron dosemeter based on superheated drop detectors is presented. This battery operated device comprises a neutron sensor, bubble-counting electronics and a temperature controller ensuring an optimal dose equivalent response. The neutron sensor is a 12 ml detector vial containing an emulsion of about 50,000 halocarbon-12 droplets of 100 microns diameter. The temperature controller is a low-power, solid-state device stabilising the emulsion at 31.5 degrees C by means of an etched foil heater. The microprocessor controlled counting electronics relies on a double piezo-electric transducer configuration to record bubble formation acoustically via a comparative pulse-shape analysis of ambient noise and detector signals. The performance of the dosemeter was analysed in terms of the requirements presently developed for neutron personal dosemeters. The detection threshold is about 1 microSv, while the personal dose equivalent response to neutrons in the thermal to 62 MeV range falls within a factor 1.6 of 13 bubbles per microSv. PMID:11586744

d'Errico, F; Apfel, R E; Curzio, G; Nath, R

2001-01-01

136

Dose assessment of aircrew using passive detectors.  

PubMed

Radiation exposure of aircrew is a serious concern which has been given special emphasis in the European Council directive 96/29/Euratom. The cosmic ray induced neutron component can contribute more than 50% to the biologically relevant dose at aviation altitudes. Various computational approaches to route dose assessment, e.g. CARI, are in use nowadays and are compared with experimental data. Measurements of aircrew exposure usually involve extensive instrumentation in order to cover the whole particle spectrum and energy range present inside aircraft. Due to their small size and easy handling, thermoluminescence dosemeters represent an appropriate alternative. Previous measurements onboard aircraft applying the high-temperature ratio method with LiF:Mg,Ti dosemeters for the determination of an 'averaged' linear energy transfer of mixed radiation fields demonstrate the ability of this method to evaluate the dose equivalent, according to the Q(LETinfinity) relationship proposed by the ICRP. Measurements with CaF2:Tm dosemeters are currently in progress and are discussed here. PMID:12382932

Hajek, M; Berger, T; Schöner, W; Summerer, L; Vana, N

2002-01-01

137

Bonner sphere neutron spectrometry at spent fuel casks  

NASA Astrophysics Data System (ADS)

For transport and interim storage of spent fuel elements from power reactors and vitrified highly active waste (HAW) from reprocessing, various types of casks are used. The radiation exposure of the personnel during transportation and storage of these casks is caused by mixed photon-neutron fields and, frequently, the neutron dose is predominant. In operational radiation protection, survey meters and even personal dosemeters with imperfect energy dependence of the dose-equivalent response are used, i.e. the fluence response of the devices does not match the fluence-to-dose equivalent conversion function. In order to achieve more accurate dosimetric information and to investigate the performance of dosemeters, spectrometric investigations of the neutron fields are necessary. Therefore, fluence spectra and dose rates were measured by means of a simple portable Bonner multisphere spectrometer (BSS). The paper describes briefly the experimental set-up and evaluation procedure. Measured spectra for different locations, types of casks and inventory are discussed. The spectra provide a basis to determine dose rates and other integral quantities with higher accuracy and for choosing suitable area monitors, respectively, to establish correction factors applied to the dosemeter reading.

Rimpler, Arndt

2002-01-01

138

Chemical dosimetry system for criticality accidents.  

PubMed

Ruder Boskovi? Institute (RBI) criticality dosimetry system consists of a chemical dosimetry system for measuring the total (neutron + gamma) dose, and a thermoluminescent (TL) dosimetry system for a separate determination of the gamma ray component. The use of the chemical dosemeter solution chlorobenzene-ethanol-trimethylpentane (CET) is based on the radiolytic formation of hydrochloric acid, which protonates a pH indicator, thymolsulphonphthalein. The high molar absorptivity of its red form at 552 nm is responsible for a high sensitivity of the system: doses in the range 0.2-15 Gy can be measured. The dosemeter has been designed as a glass ampoule filled with the CET solution and inserted into a pen-shaped plastic holder. For dose determinations, a newly constructed optoelectronic reader has been used. The RBI team took part in the International Intercomparison of Criticality Accident Dosimetry Systems at the SILENE Reactor, Valduc, June 2002, with the CET dosimetry system. For gamma ray dose determination TLD-700 TL detectors were used. The results obtained with CET dosemeter show very good agreement with the reference values. PMID:15353694

Miljani?, Saveta; Ilijas, Boris

2004-01-01

139

Megavoltage Beam Properties Affecting Patient Dose in Radiation Therapy.  

NASA Astrophysics Data System (ADS)

Certain properties of megavoltage beams have remained of concern in radiation therapy. This investigation is directed towards a better characterization of the problems presented by contaminant electrons in these photon beams, by their spectral distribution and by their interaction in a specific target tissue where heterogeneity poses a particular clinical problem. Two megavoltage beams, a ^{60}CO and a 6 MV, are studied. The energy spectrum modified by passing through the collimator is measured using a direct scintillation spectroscopy technique. The electron component is revealed using a sweeping magnet. A specially built pancake charged particle detector makes it possible to measure the fluence and the dose of the contaminant electrons directly. The sweeping magnet is used in the further investigations of these electrons. Dose perturbations at interfaces between surgical steel implants and tissue are analyzed using 20 ?m thick TL dosemeters. The various factors affecting the relative magnitudes of these dose perturbations are discussed. Results show that direct scintillation spectroscopy provides an adequate first measure of the collimator produced energy spectrum. The general applicability of charge detector in the explicit measurement of the fluence and the dose of the contaminant electrons is demonstrated. A gradient effect is observed when the detector is used in conjunction with the sweeping magnet. A 50% contribution to the total patient surface dose by secondarily produced radiation in the machine head assemblage is observed at large field sizes. A maximum dose enhancement of 42% at stainless steel/tissue equivalent material interface is measured using the micron thick TL dosemeters. This enhancement is of sufficient magnitude to produce unacceptable radiation sequelae. The measurements allow the design of clinically acceptable techniques. The dosemeters proved to be of dimension and sensitivity appropriate for precise, and accurate measurement of dose perturbation at interfaces due to metal implants.

Ikoro, Nnaemeka C.

1988-08-01

140

Ambient Dose Equivalent measured at the Instituto Nacional de Cancerologia Department of Nuclear Medicine  

SciTech Connect

Ambient dose equivalent values were determined in several sites at the Instituto Nacional de Cancerologia, Departmento de Medicina Nuclear, using TLD-100 and TLD-900 thermoluminescent dosemeters. Additionally, ambient dose equivalent was measured at a corridor outside the hospitalization room for patients treated with {sup 137}Cs brachytherapy. Dosemeter calibration was performed at the Instituto Nacional de Investigaciones Nucleares, Laboratorio de Metrologia, to known {sup 137}Cs gamma radiation air kerma. Radionuclides considered for this study are {sup 131}I, {sup 18}F, {sup 67}Ga, {sup 99m}Tc, {sup 111}In, {sup 201}Tl and {sup 137}Cs, with main gamma energies between 93 and 662 keV. Dosemeters were placed during a five month period in the nuclear medicine rooms (containing gamma-cameras), injection corridor, patient waiting areas, PET/CT study room, hot lab, waste storage room and corridors next to the hospitalization rooms for patients treated with {sup 131}I and {sup 137}Cs. High dose values were found at the waste storage room, outside corridor of {sup 137}Cs brachytherapy patients and PET/CT area. Ambient dose equivalent rate obtained for the {sup 137}Cs brachytherapy corridor is equal to (18.51{+-}0.02)x10{sup -3} mSv/h. Sites with minimum doses are the gamma camera rooms, having ambient dose equivalent rates equal to (0.05{+-}0.03)x10{sup -3} mSv/h. Recommendations have been given to the Department authorities so that further actions are taken to reduce doses at high dose sites in order to comply with the ALARA principle (as low as reasonably achievable).

Avila, O. [Instituto Nacional de Investigaciones Nucleares, AP 18-1027, 11801, DF (Mexico); Torres-Ulloa, C. L. [Instituto Nacional de Investigaciones Nucleares, AP 18-1027, 11801, DF (Mexico); Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, AP 70-542, 04510, DF (Mexico); Medina, L. A. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP 20-364, 01000, DF (Mexico); Unidad de Investigacion Biomedica en Cancer INCan-UNAM, Av. San Fernando 22 C.P. 14080 (Mexico); Trujillo-Zamudio, F. E. [Instituto Nacional de Cancerologia (INCan), Av. San Fernando 22, C.P. 14080 (Mexico); Gamboa de Buen, I. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, AP 70-543, 04510 DF (Mexico); Buenfil, A. E.; Brandan, M. E. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP 20-364, 01000, DF (Mexico)

2010-12-07

141

Ambient Dose Equivalent measured at the Instituto Nacional de Cancerología Department of Nuclear Medicine  

NASA Astrophysics Data System (ADS)

Ambient dose equivalent values were determined in several sites at the Instituto Nacional de Cancerología, Departmento de Medicina Nuclear, using TLD-100 and TLD-900 thermoluminescent dosemeters. Additionally, ambient dose equivalent was measured at a corridor outside the hospitalization room for patients treated with 137Cs brachytherapy. Dosemeter calibration was performed at the Instituto Nacional de Investigaciones Nucleares, Laboratorio de Metrología, to known 137Cs gamma radiation air kerma. Radionuclides considered for this study are 131I, 18F, 67Ga, 99mTc, 111In, 201Tl and 137Cs, with main gamma energies between 93 and 662 keV. Dosemeters were placed during a five month period in the nuclear medicine rooms (containing gamma-cameras), injection corridor, patient waiting areas, PET/CT study room, hot lab, waste storage room and corridors next to the hospitalization rooms for patients treated with 131I and 137Cs. High dose values were found at the waste storage room, outside corridor of 137Cs brachytherapy patients and PET/CT area. Ambient dose equivalent rate obtained for the 137Cs brachytherapy corridor is equal to (18.51+/-0.02)×10-3 mSv/h. Sites with minimum doses are the gamma camera rooms, having ambient dose equivalent rates equal to (0.05+/-0.03)×10-3 mSv/h. Recommendations have been given to the Department authorities so that further actions are taken to reduce doses at high dose sites in order to comply with the ALARA principle (as low as reasonably achievable).

Ávila, O.; Torres-Ulloa, C. L.; Medina, L. A.; Trujillo-Zamudio, F. E.; de Buen, I. Gamboa; Buenfil, A. E.; Brandan, M. E.

2010-12-01

142

Dose received by occupationally exposed workers at a nuclear medicine department  

NASA Astrophysics Data System (ADS)

Personal Dose Equivalent (PDE) values were determined for occupational exposed workers (OEW) at the Nuclear Medicine Department (NMD) of "Instituto Nacional de Cancerología" (INCan), Mexico, using TLD-100 thermoluminescent dosemeters. OEW at NMD, INCan make use of radiopharmaceuticals for diagnosis and treatment of diseases. Radionuclides associated to a pharmaceutical compound used at this Department are 131I, 18F, 68Ga, 99mTc, 111In and 11C with main gamma emission energies between 140 and 511 keV. Dosemeter calibration was performed at the metrology department of "Instituto Nacional de Investigaciones Nucleares" (ININ), Mexico. Every occupational worker used dark containers with three dosimeters which were replaced monthly for a total of 5 periods. Additionally, control dosemeters were also placed at a site free of radioactive sources in order to determine the background radiation. Results were adjusted to find PDE/day and estimating annual PDE values in the range between 2 mSv (background) and 9 mSv. The mean annual value is 3.51 mSv and the standard deviation SD is 0.78 mSv. Four of the 16 OEW received annual doses higher than the average +1 SD (4.29 mSv). Results depend on OEW daily activities and were consistent for each OEW for the 5 studied periods as well as with PDE values reported by the firm that performs the monthly service. All obtained values are well within the established annual OEW dose limit stated in the "Reglamento General de Seguridad Radiológica", México (50 mSv), as well as within the lower limit recommended by the "International Commission on Radiation Protection" (ICRP), report no.60 (20 mSv). These results verify the adequate compliance of the NMD at INCan, Mexico with the norms given by the national regulatory commission.

Ávila, O.; Sánchez-Uribe, N. A.; Rodríguez-Laguna, A.; Medina, L. A.; Estrada, E.; Buenfil, A. E.; Brandan, M. E.

2012-10-01

143

Bayesian methods for chromosome dosimetry following a criticality accident.  

PubMed

Radiation doses received during a criticality accident will be from a combination of fission spectrum neutrons and gamma rays. It is desirable to estimate the total dose, as well as the neutron and gamma doses. Present methods for dose estimation with chromosome aberrations after a criticality accident use point estimates of the neutron to gamma dose ratio obtained from personnel dosemeters and/or accident reconstruction calculations. In this paper a Bayesian approach to dose estimation with chromosome aberrations is developed which allows the uncertainty of the dose ratio to be considered. Posterior probability densities for the total and the neutron and gamma doses were derived. PMID:12862245

Brame, R S; Groer, P G

2003-01-01

144

Computed Tomography: Image and Dose Assessment  

NASA Astrophysics Data System (ADS)

In this work an experimental evaluation of image quality and dose imparted during a computed tomography study in a Public Hospital in Mexico City is presented; The measurements required the design and construction of two phantoms at the Institute of Physics, UNAM, according to the recommendations of American Association of Physicists in Medicine (AAPM). Image assessment was performed in terms the spatial resolution and image contrast. Dose measurements were carried out using LiF: Mg,Ti (TLD-100) dosemeters and pencil-shaped ionisation chamber; The results for a computed tomography head study in single and multiple detector modes are presented.

Valencia-Ortega, F.; Ruiz-Trejo, C.; Rodríguez-Villafuerte, M.; Buenfil, A. E.; Mora-Hernández, L. A.

2006-09-01

145

Measurement of dose-width product in panoramic dental radiology.  

PubMed

The National Radiological Protection Board has recommended the introduction of dose-width product (DWP) for the measurement of patient dose in panoramic dental radiology. The present work describes a method for measuring DWP using a pencil ionization chamber. The technique was tested on five panoramic dental units; the reproducibility of the method was 5.7%. In order to test the method, DWP was also assessed using thermoluminescent dosemeters and film. The results obtained agreed within 8.6% with those obtained using the pencil ionization chamber method. The proposed method appears to be simple and precise. PMID:12642282

Isoardi, P; Ropolo, R

2003-02-01

146

Cooling rate effects in thermoluminescence dosimetry grade lithium flouride. Implications for practical dosimetry.  

PubMed

A systematic investigation of the effects of cooling rates in the range of 10(-1) to 2 X 10(5) degrees C min-1 applied to TLD-700, LiF thermoluminescence dosemeters has shown that the 'transfer sensitivity' effect observed by Booth, Johnson and Attix (1972) is only of importance for cooling rates greater than 10(3) degrees C min-1. Although it is concluded that for practical dosimetry purposes the effect may be ignored it is not clear why Booth et al. observed such large changes and until this discrepancy is explained it is recommended that a low temperature pre-irradiation anneal should be used. PMID:1267932

Mason, E W; McKinlay, A F; Clark, I

1976-01-01

147

Uncertainties in external dosimetry: analytical vs. Monte Carlo method.  

PubMed

Over the years, the International Commission on Radiological Protection (ICRP) and other organisations have formulated recommendations regarding uncertainty in occupational dosimetry. The most practical and widely accepted recommendations are the trumpet curves. To check whether routine dosemeters comply with them, a Technical Report on uncertainties issued by the International Electrotechnical Commission (IEC) can be used. In this report, the analytical method is applied to assess the uncertainty of a dosemeter fulfilling an IEC standard. On the other hand, the Monte Carlo method can be used to assess the uncertainty. In this work, a direct comparison of the analytical and the Monte Carlo methods is performed using the same input data. It turns out that the analytical method generally overestimates the uncertainty by about 10-30 %. Therefore, the results often do not comply with the recommendations of the ICRP regarding uncertainty. The results of the more realistic uncertainty evaluation using the Monte Carlo method usually comply with the recommendations of the ICRP. This is confirmed by results seen in regular tests in Germany. PMID:19942627

Behrens, R

2009-11-26

148

Monte Carlo-derived TLD cross-calibration factors for treatment verification and measurement of skin dose in accelerated partial breast irradiation  

NASA Astrophysics Data System (ADS)

Monte Carlo simulation was employed to calculate the response of TLD-100 chips under irradiation conditions such as those found during accelerated partial breast irradiation with the MammoSite radiation therapy system. The absorbed dose versus radius in the last 0.5 cm of the treated volume was also calculated, employing a resolution of 20 µm, and a function that fits the observed data was determined. Several clinically relevant irradiation conditions were simulated for different combinations of balloon size, balloon-to-surface distance and contents of the contrast solution used to fill the balloon. The thermoluminescent dosemeter (TLD) cross-calibration factors were derived assuming that the calibration of the dosemeters was carried out using a Cobalt 60 beam, and in such a way that they provide a set of parameters that reproduce the function that describes the behavior of the absorbed dose versus radius curve. Such factors may also prove to be useful for those standardized laboratories that provide postal dosimetry services.

Garnica-Garza, H M

2009-03-01

149

Results of measurements on shuttle missions to the ISS of the neutron component of the radiation field  

NASA Astrophysics Data System (ADS)

Secondary neutrons can be a major contributor to dose equivalent and effective dose inside a spacecraft for the altitude range and inclination of the International Space Station. The exact proportion is very dependent on the amount of shielding of the primary galactic cosmic radiation and trapped particles, but is likely to lie in the range of 10 60%. Neutron personal dosemeters of simple design, processed using simple techniques developed for routine personal dosimetry, have been used to determine the neutron component, including the neutron-like interactions of high energy protons. For the etch regime employed, the combination of high LET threshold (there is little response below a restricted LET200 in PADC of 30 40 keV/?m) and poor angle dependence of response to high-energy charged particles results in a much reduced overall response of the neutron dosemeter to the HZE component of the field in spacecraft and no response to protons of energy greater than about 1 MeV. A correction of 10 20% is necessary to account for the detector HZE response. Alternatively, an additional chemical etch can be carried out which allows discrimination.

Bartlett, D. T.; Hager, L. G.; Tanner, R. J.

150

Doses to skin during dynamic perfusion computed tomography of the liver.  

PubMed

Many new computed tomography (CT) techniques have been introduced during the recent years, one of them being CT-assisted dynamic perfusion imaging (perfusion CT, PCT). Many concerns were raised when first cases of deterministic radiation effects were reported. This paper shows how radiochromic films can be utilised as passive dosemeters for use in PCT. Radiochromic dosemeters undergo a colour change directly and do not require chemical processing. Prior to their use, they need to be calibrated. Films are placed on top and on the right side of the patient and exposed during the procedure. Readout is performed using a densitometer. Results show that average local skin doses are 0.51±0.07 and 0.42±0.04 Gy on top and on the lateral side of the patient, respectively. Results of the patient dosimetry (local skin doses) are consistent. This is due to the fact that each patient had the same CT protocol used for imaging (120 kV, 60 mA and C(vol) of 247.75 mGy). Radiochromic films designed for interventional radiology can be effectively used for local skin dose measurements in perfusion CT. Dose values obtained are below the threshold needed for deterministic effects (erythema, hair loss, etc.). These effects might happen if inappropriate CT protocol is used; one that is usually used for routine imaging. PMID:22728469

Beganovic, Adnan; Sefic-Pasic, Irmina; Skopljak-Beganovic, Amra; Kristic, Spomenka; Sunjic, Svjetlana; Mekic, Amra; Gazdic-Santic, Maja; Drljevic, Advan; Samek, Davorin

2012-06-22

151

Quality assurance evaluation of spot scanning beam proton therapy with an anthropomorphic prostate phantom.  

PubMed

Objective: The purpose of this study was to evaluate spot scanning proton therapy with an anthropomorphic prostate phantom at the Proton Therapy Center of The University of Texas MD Anderson Cancer Center at Houston, TX (PTCH). Methods: An anthropomorphic prostate phantom from the Radiological Physics Center (RPC), The University of Texas MD Anderson Cancer Center, Houston, TX, was used, which contained thermoluminescent dosemeters and GAFCHROMIC(®) EBT2 film (ISP Technologies, Wayne, NJ). The phantom was irradiated by the Hitachi synchrotron (Hitachi America, Ltd, Tarrytown, NY), and the results were compared between the treatment planning system (TPS) and RPC measurements. Results: RPC results show that the right/left, inferior/superior and posterior/anterior aspects of the coronal/sagittal and EBT2 film measurements were within ±7%/±4?mm of the TPS. The RPC thermoluminescent dosemeter measurements of the prostate and femoral heads were within 3% of the TPS. Conclusion: The RPC prostate phantom is a useful mechanism to evaluate spot scanning beam proton therapy within certain confidence levels. Advances in knowledge: The RPC anthropomorphic prostate phantom could be used to establish quality assurance of spot scanning proton beam for patients with prostate cancer. PMID:24049129

Iqbal, K; Gillin, M; Summers, P A; Dhanesar, S; Gifford, K A; Buzdar, S A

2013-09-18

152

Personal dosimetry for interventional operators: when and how should monitoring be done?  

PubMed Central

Objective Assessment of the potential doses to the hands and eyes for interventional radiologists and cardiologists can be difficult. A review of studies of doses to interventional operators reported in the literature has been undertaken. Methods Distributions for staff dose to relevant parts of the body per unit dose–area product and for doses per procedure in cardiology have been analysed and mean, median and quartile values derived. The possibility of using these data to provide guidance for estimation of likely dose levels is considered. Results Dose indicator values that could be used to predict orders of magnitude of doses to the eye, thyroid and hands from interventional operator workloads have been derived, based on the third quartile values, from the distributions of dose results analysed. Conclusion Dose estimates made in this way could be employed in risk assessments when reviewing protection and monitoring requirements. Data on the protection provided by different shielding and technique factors have also been reviewed to provide information for risk assessments. Recommendations on the positions in which dosemeters are worn should also be included in risk assessments, as dose measurements from suboptimal dosemeter use can be misleading.

Martin, C J

2011-01-01

153

The new EC technical recommendations for monitoring individuals occupationally exposed to external radiation.  

PubMed

The purpose of the European Commission technical recommendations (TR) for monitoring individuals occupationally exposed to external radiation is to provide guidance on those aspects of the implementation of the European Union Parliament and Council Directives directly related to individual monitoring of external radiation, and to encourage harmonisation thereof. They are mainly aimed at the management and staff of IM services but also at manufacturers, laboratories supplying type-testing services, national authorities trying to harmonise approval procedures, and government bodies to harmonise regulations and guidance. The TR main topics are: objectives and aims of IM for external radiation; dosimetry concepts; accuracy requirements; calibration, type testing and performance testing; approval procedures; quality assurance and quality control; and dose record keeping. Attention is paid to particular aspects, such as wide energy ranges for the use of personal dosemeters, pulsed fields and non-charged particle equilibrium; and use of active personal dosemeters. The TR give proposals towards achieving harmonisation in IM and the eventual mutual recognition of services and of dose results. PMID:20959338

Alves, J G; Ambrosi, P; Bartlett, D T; Currivan, L; van Dijk, J W E; Fantuzzi, E; Kamenopoulou, V

2010-10-19

154

A TLD dose algorithm using artificial neural networks  

SciTech Connect

An artificial neural network was designed and used to develop a dose algorithm for a multi-element thermoluminescence dosimeter (TLD). The neural network architecture is based on the concept of functional links network (FLN). Neural network is an information processing method inspired by the biological nervous system. A dose algorithm based on neural networks is fundamentally different as compared to conventional algorithms, as it has the capability to learn from its own experience. The neural network algorithm is shown the expected dose values (output) associated with given responses of a multi-element dosimeter (input) many times. The algorithm, being trained that way, eventually is capable to produce its own unique solution to similar (but not exactly the same) dose calculation problems. For personal dosimetry, the output consists of the desired dose components: deep dose, shallow dose and eye dose. The input consists of the TL data obtained from the readout of a multi-element dosimeter. The neural network approach was applied to the Harshaw Type 8825 TLD, and was shown to significantly improve the performance of this dosimeter, well within the U.S. accreditation requirements for personnel dosimeters.

Moscovitch, M.; Rotunda, J.E.; Tawil, R.A.; Rathbone, B.A.

1995-12-31

155

Thermoluminescence characteristics of flat optical fiber in radiation dosimetry under different electron irradiation conditions  

NASA Astrophysics Data System (ADS)

Thermoluminescence (TL) flat optical fibers (FF) have been proposed as radiation sensor in medical dosimetry for both diagnostic and radiotherapy applications. A flat optical fiber with nominal dimensions of (3.226 × 3.417 × 0.980) mm3 contains pure silica SiO2 was selected for this research. The FF was annealed at 400°C for 1 h before irradiated. Kinetic parameters and dosimetric glow curve of TL response were studied in FF with respect to electron irradiation of 6 MeV, 15 MeV and 21 MeV using linear accelerator (LINAC) in the dose range of 2.0-10.0 Gy. The TL response was read using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader used includes; initial preheat temperature of 80°C, maximum readout temperature is 400°C and the heating rate of 30°Cs-1. The proposed FF shows excellent linear radiation response behavior within the clinical relevant dose range for all of these energies, good reproducibility, independence of radiation energy, independence of dose rate and exhibits a very low thermal fading. From these results, the proposed FF can be used as radiation dosimeter and favorably compares with the widely used of LiF:MgTi dosimeter in medical radiotherapy application.

Alawiah, A.; Intan, A. M.; Bauk, S.; Abdul-Rashid, H. A.; Yusoff, Z.; Mokhtar, M. R.; Wan Abdullah, W. S.; Mat Sharif, K. A.; Mahdiraji, G. A.; Mahamd Adikan, F. R.; Tamchek, N.; Noor, N. M.; Bradley, D. A.

2013-05-01

156

Interim status report of the TMI personnel-dosimetry project  

SciTech Connect

The current 2-chip TLD personnel dosimeter in use at Three Mile Island (TMI) has been shown inadequate for the anticipated high beta/gamma fields during TMI recovery operations in some areas. This project surveyed the available dosimeter systems, set up an Idaho National Engineering Laboratory (INEL) prototype system, and compared this system with those commercial systems that could be made immediately available for comparison. Of the systems tested, the new INEL personnel dosimeter was found to produce the most accurate results for use in recovery operations at TMI-2. The other multiple-chip or multiple-filter systems were found less desirable at present. The most prominent deficiencies in the INEL dosimeter stem from the fact that it lacks a completely automated reader and its x-ray and thermal neutron responses require additional development. A automated prototype reader system may be in operation by the end of CY-1981. Three alternatives for operational dosimetry are discussed. A combination of a modified version of the presently used Harshaw 2-chip dosimeter and the INEL dosimeter is recommended.

Rich, B.L.; Alvarez, J.L.; Adams, S.R.

1981-06-01

157

Catalytic hydrogenation of coal-derived liquids. Interim report, September-November 1981  

SciTech Connect

An experimental study was completed to determine the optimum relationship between temperature and space velocity for our hydrotreating-hydrocracking catalyst developed for the denitrogenation of Solvent Refined Coal (SRC-II). The temperature range was 350 to 500/sup 0/C, LHSV was 0.25 to 2.5 and the throughput was held constant at 4500 ml/60 ml of catalyst. The surprising result is that 500/sup 0/C and 1.25 LHSV is the best condition. Conditions were finally found under which a commercially available catalyst will give acceptable denitrogenation of SRC. It is Harshaw's HT400 E 1/32'' and the unique factor is to add 1.5 volume percent of water to the SRC feed. When operated in this manner, the catalyst gave <0.3 wt % nitrogen in the product for 140 hours, was regenerated and did even better. Without water addition, specification denitrogenation was obtained for only forty hours. The hydrotreating-hydrocracking catalyst that we have developed has demonstrated hundreds of hours of use and dozens of regnerations, both in batch and trickle bed reactors. This appears to be an economically attractive way to convert solvent refined coal into an acceptable feedstock for a conventional petroleum refinery and thus permit coal to reduce somewhat the burden on petroleum for transportation grade fuels.

Berg, L.; McCandless, F.P.

1981-12-01

158

Climax spent fuel dosimetry. Short term exposure, 8 March 1983  

SciTech Connect

The second short-term exposure (performed 8 March 1983) in Hole CFH3 at the Climax Spent Fuel Test site is described. These short-term (1 hour long) exposures are intended to provide an independent measurement of the exposure rate at the wall and the 0.51-m and 0.66-m locations. Only CaF{sub 2} TLD`s were used in the second short-term exposure. Harshaw chips were cut to 0.32 x 0.18 x 0.09 cm size and aged by several exposure/readout/bakeout cycles until all odd chips were weeded out and the remaining chips exhibited stable sensitivities. Exposure at Climax was done by removing the existing long-term dosimetry strings and inserting identical strings using the CaF{sub 2} TLD`s in the stainless steel holders. The first short-term exposure produced absorbed doses as high as {similar_to}000 rads-LiF. The linearity corrections determined for the CaF{sub 2} TLD`s at these exposure levels were {similar_to}2%. The present post-exposure calibration method used calibration doses very close to those encountered in the field.

Quam, W.; DeVore, T.

1984-06-01

159

Response of thermoluminescent dosimeters to photons simulated with the Monte Carlo method  

NASA Astrophysics Data System (ADS)

Personal monitors composed of thermoluminescent dosimeters (TLDs) made of natural fluorite (CaF2:NaCl) and lithium fluoride (Harshaw TLD-100) were exposed to gamma and X rays of different qualities. The GEANT4 radiation transport Monte Carlo toolkit was employed to calculate the energy depth deposition profile in the TLDs. X-ray spectra of the ISO/4037-1 narrow-spectrum series, with peak voltage (kVp) values in the range 20 300 kV, were obtained by simulating a X-ray Philips MG-450 tube associated with the recommended filters. A realistic photon distribution of a 60Co radiotherapy source was taken from results of Monte Carlo simulations found in the literature. Comparison between simulated and experimental results revealed that the attenuation of emitted light in the readout process of the fluorite dosimeter must be taken into account, while this effect is negligible for lithium fluoride. Differences between results obtained by heating the dosimeter from the irradiated side and from the opposite side allowed the determination of the light attenuation coefficient for CaF2:NaCl (mass proportion 60:40) as 2.2 mm-1.

Moralles, M.; Guimarães, C. C.; Okuno, E.

2005-06-01

160

Pore structure characterization of catalyst supports via low field NMR  

SciTech Connect

The pore structures of two types of catalyst support material were studied: {gamma}-alumina and silica aerogel. The alumina samples were commercial catalyst supports made in 1/8 inch diameter pellet form by Harshaw Chemical. Aerogels were prepared by forming a gel in a two-step, base-catalyzed process using TEOS, followed by supercritical drying to form the aerogel. Two different aerogels were made, one undergoing the drying process immediately after gel formation (non-aged), and the other being aged in the gel state for two weeks in a basic solution of 0.1 molar NH{sub 4}OH at 323 K before being supercritically dried (aged). The aging process is believed to alter the aerogel pore structure. The pore size distribution of the alumina material was determined via NMR and compared to results obtained by mercury intrusion and nitrogen adsorption/condensation techniques. The pore size distributions of the two aerogel samples were measured via NMR and nitrogen adsorption/condensation; the material was too compressible for porosimetry.

Smith, D.M.; Glaves, C.L.; Gallegos, D.P. (Univ. of New Mexico, Albuquerque (USA))

1988-09-01

161

Measurement of radon exhalation rate and soil gas radon concentration in areas of southern Punjab, Pakistan.  

PubMed

Plastic track detectors were used to measure the radon concentration and exhalation rate from the soil samples. The samples were collected from areas of southern Punjab, Pakistan. In a laboratory experiment, passive alpha dosemeters were installed inside cylindrical bottles containing the soil samples. The radon concentrations and the radon exhalation rate were found in the ranges of 34 +/- 7 to 260 +/- 42 Bq m(-3) and 38 +/- 8 to 288 +/- 46 mBq m(-2) h(-1), respectively. The on-site measurements of radon in the soil gas were also carried out in these areas using a scintillation alpha counter. The concentration of radon in the soil gas was found in the range of 423 +/- 82-3565 +/- 438 Bq m(-3). PMID:20385542

Mujahid, S A; Hussain, S; Ramzan, M

2010-04-12

162

Somatic aberration induction in Tradescantia occidentalis by neutrons, x- and gamma-radiations. I. Dosimetry.  

PubMed

The dosimetry is described for an investigation of the induction of somatic aberrations in Tradescantia occidentalis by substantially mono-energetic neutrons in the energy range 100 keV to 15 MeV, by 200 keV X-rays and cobalt-60 gamma-radiation. Spectrometry was carried out for both neutrons and X-rays. Neutron fluence was measured by uranium fission chambers. Two types of ionization chamber were employed for dose measurement. One chamber was manufactured of CH-plastic and filled with acetylene and the other of graphite and filled with carbon dioxide. Dosimetry for X- and gamma-radiation was by means of lithium fluoride thermoluminescent dosemeters calibrated against a Victoreen ionization chamber. PMID:1084865

Dennis, J A; Delafield, H J; Peaple, L H; Boot, S J

1976-04-01

163

Dose response of xylitol and sorbitol for EPR retrospective dosimetry with applications to chewing gum.  

PubMed

The purpose of this investigation was to study the radiation-induced electron paramagnetic resonance signal in sweeteners xylitol and sorbitol for use in retrospective dosimetry. For both sweeteners and chewing gum, the signal changed at an interval of 1-84 d after irradiation with minimal changes after 4-8 d. A dependence on storage conditions was noticed and the exposure of the samples to light and humidity was therefore minimised. Both the xylitol and sorbitol signals showed linearity with dose in the measured dose interval, 0-20 Gy. The dose-response measurements for the chewing gum resulted in a decision threshold of 0.38 Gy and a detection limit of 0.78 Gy. A blind test illustrated the possibility of using chewing gums as a retrospective dosemeter with an uncertainty in the dose determination of 0.17 Gy (1 SD). PMID:22908355

Israelsson, A; Gustafsson, H; Lund, E

2012-08-19

164

External dosimetry in the aftermath of a radiological terrorist event.  

PubMed

This paper reviews external dosimetry in emergency preparedness planning for a potential terrorist release of radioactive material in a densely populated area. The radiation dose received by response workers and members of the public is needed to understand health risks. The existing framework for dosimetry of routinely occupationally exposed workers is not directly applicable to all emergency workers who would respond to a radiological terrorist event. Emergency preparedness plans incorporate various old and new dosimetry technologies, including quartz fibre electrets, electronic dosemeters, personnel badges and wallet cards. Environmental monitoring and dose calculations are the usual methods for determining public dose. However, during the late-phase response, after removable contamination has been eliminated, it may be easier and more straightforward to provide individual dosimetry for members of the public who may be moving through a city with varying contamination areas. Doing so could allow resumption of normal activities earlier and promote confidence in reusing the site. PMID:16606662

Klemic, Gladys A; Bailey, Paul D; Miller, Kevin M; Monetti, Matthew A

2006-04-10

165

Radionuclide neutron sources in calibration laboratory--neutron and gamma doses and their changes in time.  

PubMed

The calibration laboratory, having standard neutron fields of radionuclide sources, should perform regular measurements of fields' parameters in order to check their stability and to get knowledge of any changes. Usually, accompanying gamma radiation is not of serious concern, but some personal dosemeters, old neutron dose equivalent meters with scintillation detectors and the dose meters of mixed radiation require the determination of this component. In the Laboratory of Radiation Protection Measurements in the Institute of Atomic Energy, Poland, the fields of radionuclide neutron sources (252)Cf, (241)Am-Be and (239)Pu-Be were examined for nearly 20 y. A number of detectors and methods have been applied for the determination of neutron ambient dose equivalent rate and for the determination of neutron and gamma dose components. This paper presents the recent results of measurements of gamma and neutron dose and dose equivalent, compared with the results accumulated in nearly 20 y. PMID:17513855

Józefowicz, K; Golnik, N; Tulik, P; Zielczynski, M

2007-05-19

166

Comparing Geant4 hadronic models for the WENDI-II rem meter response function.  

PubMed

The WENDI-II rem meter is one of the most popular neutron dosemeters used to assess a useful quantity of radiation protection, namely the ambient dose equivalent. This is due to its high sensitivity and its energy response that approximately follows the conversion function between neutron fluence and ambient dose equivalent in the range of thermal to 5 GeV. The simulation of the WENDI-II response function with the Geant4 toolkit is then perfectly suited to compare low- and high-energy hadronic models provided by this Monte Carlo code. The results showed that the thermal treatment of hydrogen in polyethylene for neutron <4 eV has a great influence over the whole detector range. Above 19 MeV, both Bertini Cascade and Binary Cascade models show a good correlation with the results found in the literature, while low-energy parameterised models are not suitable for this application. PMID:22972796

Vanaudenhove, T; Dubus, A; Pauly, N

2012-09-12

167

Characterisation of bubble detectors for aircrew and space radiation exposure.  

PubMed

The Earth's atmosphere acts as a natural radiation shield which protects terrestrial dwellers from the radiation environment encountered in space. In general, the intensity of this radiation field increases with distance from the ground owing to a decrease in the amount of atmospheric shielding. Neutrons form an important component of the radiation field to which the aircrew and spacecrew are exposed. In light of this, the neutron-sensitive bubble detector may be ideal as a portable personal dosemeter at jet altitudes and in space. This paper describes the ground-based characterisation of the bubble detector and the application of the bubble detector for the measurement of aircrew and spacecrew radiation exposure. PMID:16987919

Green, A R; Bennett, L G I; Lewis, B J; Tume, P; Andrews, H R; Noulty, R A; Ing, H

2006-01-01

168

Dose evaluation in criticality accident conditions using transient critical facilities fueled with a fissile solution.  

PubMed

Neutron dose measurement and evaluation techniques in criticality accident conditions using a thermo luminescence dosemeter (TLD) was studied at the Transient Experiment Critical Facility (TRACY) of Japan Atomic Energy Research Institute (JAERI). In the present approach, the absorbed dose is derived from the ambient dose equivalent measured with a TLD, using the appropriate conversion factor given by computation. Using this technique, the neutron dose around the SILENE reactor of the Institute for Radioprotection and Nuclear Safety (IRSN) of France was measured in the Accident Dosimetry Intercomparison Exercise (June 10-21, 2002) organized by OECD/NEA and IRSN. In this exercise, the gamma dose was also measured with a TLD. In this report, measurements and evaluation results at TRACY and SILENE are presented. PMID:15353695

Nakamura, T; Tonoike, K; Miyoshi, Y

2004-01-01

169

Long-term measurements of H*(10) at aviation altitudes in the northern hemisphere.  

PubMed

Monitoring the radiation field at aviation altitudes is achieved by the dosemeter system piDOS installed in a passenger aircraft. The basic detector is a 2 in. tissue-equivalent proportional counter (TEPC) mounted in a cabin-baggage-sized aluminium suitcase. The entire system was characterised in neutron and photon reference fields from which two calibration factors were determined according to the splitting of the measured dose deposition spectrum yd(y) into low-LET and high-LET regions. A total of 255 flights in the northern hemisphere was analysed. The dependencies of the ambient dose equivalent rates on altitude, latitude and solar activity have been determined. These new data extend the data base used in Germany for the validation of program codes to calculate the radiation exposure of air crew members. PMID:16698966

Wissmann, F

2006-05-12

170

Monte Carlo validation of the irradiator parameters of the Portuguese gamma irradiation facility after its replenishment.  

PubMed

In December 2003 the irradiator of the Portuguese (60)Co irradiation facility, UTR, was replenished. Monte Carlo simulation studies were used to characterize the facility. Comparison of simulation results with experimental measurements were useful in estimating where the source elements were positioned and what the total activity was. For this purpose the MCNPX code was used. From the experimental point of view ionization chambers and PMMA dosemeters were used. The results indicate that the geometry of the irradiator used for simulation studies shows a shift on the vertical dimension relative to the actual geometry of approximately 8cm, but with reduced influence on the irradiation process. Considering the uncertainties of the experimental and simulated approaches the activity of the irradiator stated by supplier has been confirmed. PMID:19879768

Portugal, Luis; Cardoso, João; Oliveira, Carlos

2009-09-19

171

Measurement of the neutron and gamma doses accumulated during commercial jet flights from sydney to several major destinations in the northern and southern hemispheres.  

PubMed

As recommended by the ICRP, the European Union (EU) agreed to abide by mandatory monitoring of radiation doses to crew during civil aviation flights operated by the airlines of the EU member states. A large number of measured and theoretically predicted values for the in-flight radiation doses of northern hemisphere flight routes are available. On the other hand very few data have been published for the southern hemisphere. This paper will present the results of Australian domestic and intemational return flight routes originating from Sydney. The paper also presents results of trans-hemisphere air traffic routes. Neutron and gamma doses were measured using superheated bubble dosemeters and semiconductor detectors respectively. Based on our measurements a method is suggested whereby aircrew may share their personal radiation burden by flight crew hemisphere exchange. PMID:12382933

Mukherjee, B; Cross, P; Alsop, R

2002-01-01

172

Development of a neutron personal dose equivalent detector.  

PubMed

A new neutron-measuring instrument that is intended to measure a neutron personal dose equivalent, H(p)(10) was developed. This instrument is composed of two parts: (1) a conventional moderator-based neutron dose equivalent meter and (2) a neutron shield made of borated polyethylene, which covers a backward hemisphere to adjust the angular dependence. The whole design was determined on the basis of MCNP calculations so as to have response characteristics that would generally match both the energy and angular dependencies of H(p)(10). This new instrument will be a great help in assessing the reference values of neutron H(p)(10) during field testing of personal neutron dosemeters in workplaces and also in interpreting their readings. PMID:17545659

Tsujimura, N; Yoshida, T; Takada, C; Momose, T; Nunomiya, T; Aoyama, K

2007-06-02

173

Argentine intercomparison programme for personal dosimetry.  

PubMed

An Intercomparison Programme is being carried out in Argentina for individual monitoring services. The programme was designed to test, on a voluntary basis, the performance of the laboratories that provide individual monitoring services for X and gamma radiation fields in the range from low-level dose up to 100 mSv. Irradiations were performed in full accordance with ISO 4037-3 recommendations by the Regional Reference Centre for Dosimetry (CRRD), belonging to Atomic Energy Commission (CNEA) and the Physical Dosimetry Laboratory of the Nuclear Regulatory Authority (ARN). At the same time, several items have been asked to each participant pertaining to the action range, the detectors' characteristics, the laboratory procedures, the existence of an algorithm and its use for the dosemeter evaluation. In this study the evolution of the laboratories' performance throughout the programme, based on ISO 14146 acceptance criteria, is shown. PMID:17848382

Gregori, B N; Papadópulos, S B; Saraví, M; Kunst, J J

2007-09-11

174

Determination of environmental radioactivity (238U, 232Th and 40K) and indoor natural background radiation level in Chennai city (Tamilnadu State), India.  

PubMed

An extensive study on the determination of the natural radioactivity ((238)U, (232)Th and (40)K) levels in soil samples of Chennai city, India has been undertaken and the results of the same are compared with the levels reported in other Indian cities as well as other parts of the world. The radioactivity content in the soil samples, the absorbed dose rate, annual effective dose equivalent, radium equivalent activity, internal and external hazard indices were calculated and compared with UNSCEAR 2000 recommended values. In addition to the above, mapping of indoor natural background gamma radiation levels has been made using thermo luminescent dosemeters throughout Chennai city and the same are reported. PMID:22847868

Babai, K S; Poongothai, S; Punniyakotti, J

2012-07-29

175

Simulated workplace neutron fields  

NASA Astrophysics Data System (ADS)

The use of simulated workplace neutron fields, which aim at replicating radiation fields at practical workplaces, is an alternative solution for the calibration of neutron dosemeters. They offer more appropriate calibration coefficients when the mean fluence-to-dose equivalent conversion coefficients of the simulated and practical fields are comparable. Intensive Monte Carlo modelling work has become quite indispensable for the design and/or the characterization of the produced mixed neutron/photon fields, and the use of Bonner sphere systems and proton recoil spectrometers is also mandatory for a reliable experimental determination of the neutron fluence energy distribution over the whole energy range. The establishment of a calibration capability with a simulated workplace neutron field is not an easy task; to date only few facilities are available as standard calibration fields.

Lacoste, V.; Taylor, G.; Röttger, S.

2011-12-01

176

[Radon in workplaces, a review].  

PubMed

Radon is a chemical radioactive element. It occurs naturally as the decay product of radium; it's responsible for the majority of the mean public exposure to ionizing radiation. It is often the single largest contributor to an individual's background radiation dose, and is the most variable from location to location. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as attics, and basements. Breathing in radon is a cause of lung cancer. In Italy, high levels of radon should be found in underground spaces such as wineries, historical buildings, hot springs or mushrooms farms, and it's a hazard all this workplaces. To ensure the health and safety of employees and others who have access to their work environment, the occupational physician can program inexpensive surveys (with dosemeters) and develop an information plan. PMID:21438274

Di Loreto, G; Sacco, A; Felicioli, G

177

Determination of quality parameters from statistical analysis of routine TLD dosimetry data.  

PubMed

Following the as low as reasonably achievable (ALARA) practice, there is a need to measure very low doses, of the same order of magnitude as the natural background, and the limits of detection of the dosimetry systems. The different contributions of the background signals to the total zero dose reading of thermoluminescence dosemeter (TLD) cards were analysed by using the common basic definitions of statistical indicators: the critical level (L(C)), the detection limit (L(D)) and the determination limit (L(Q)). These key statistical parameters for the system operated at NRC-Negev were quantified, based on the history of readings of the calibration cards in use. The electronic noise seems to play a minor role, but the reading of the Teflon coating (without the presence of a TLD crystal) gave a significant contribution. PMID:16709715

German, U; Weinstein, M; Pelled, O

2006-05-18

178

Monoenergetic fast neutron reference fields: I. Neutron production  

NASA Astrophysics Data System (ADS)

Monoenergetic neutron reference fields are required for the investigation of the energy-dependent response and the calibration of neutron detectors and dosemeters for various applications ranging from nuclear physics and nuclear data measurements to radiation protection. In a series of two separate publications the metrological aspects of the production and the measurement of fast neutrons are reviewed. In this first part, requirements for the nuclear reaction used to produce the neutron field as well as methods for target characterization and the general layout of reference facilities are discussed. The second part will focus on the most important techniques for field characterization. This includes the determination of the neutron fluence as well as the spectral neutron distribution and the determination of the fluence of contaminating photons.

Nolte, Ralf; Thomas, David J.

2011-12-01

179

Monoenergetic fast neutron reference fields: II. Field characterization  

NASA Astrophysics Data System (ADS)

Monoenergetic neutron reference fields are required for the calibration of neutron detectors and dosemeters for various applications ranging from nuclear physics and nuclear data measurements to radiation protection. In a series of two separate publications the metrological aspects of the production and measurement of fast neutrons are reviewed. In the first part, requirements for the nuclear reactions used to produce neutron fields as well as methods for target characterization and the general layout of reference facilities were discussed. This second part focuses on the most important techniques for field characterization and includes the determination of the neutron fluence as well as the spectral neutron distribution and the determination of the fluence of contaminating photons. The measurements are usually carried out relative to reference cross sections which are reviewed in a separate contribution, but for certain conditions 'absolute' methods for neutron measurements can be used which are directly traceable to the international system of units (SI).

Nolte, Ralf; Thomas, David J.

2011-12-01

180

Eye lens dosimetry: task 2 within the ORAMED project.  

PubMed

The ORAMED (Optimization of RAdiation protection for MEDical staff) project is funded by EU-EURATOM within the 7° Framework Programme. Task 2 of the project is devoted to study the dose to the eye lens. The study was subdivided into various topics, starting from a critical revision of the operational quantity H(p)(3), with the corresponding proposal of a cylindrical phantom simulating as best as possible the head in which the eyes are located, the production of a complete set of air kerma to dose equivalent conversion coefficients for photons from 10 keV to 10 MeV, and finally, the optimisation of the design of a personal dosemeter well suited to respond in terms of H(p)(3). The paper presents some preliminary results. PMID:21335629

Gualdrini, G; Mariotti, F; Wach, S; Bilski, P; Denoziere, M; Daures, J; Bordy, J-M; Ferrari, P; Monteventi, F; Fantuzzi, E

2011-02-20

181

Intercomparison of dosimetry systems based on CaF2:Mn TL detectors.  

PubMed

The responses of readings by the TL dosimetry system MR200 TL developed in-house and used at JSI and the TOLEDO TL system used at RBI are compared. Ten measurements at different doses ranging from 0.01 mSv to 5 Sv were carried out. A set of 36 dosemeters with three pellets of CaF2:Mn were irradiated in radiation fields of 137Cs and 60Co. Analysis of the measured results shows that at doses below 0.1 Sv, readers' outputs do not differ >5% from each other. At doses >1 Sv, the results obtained by the MR200 reader must be corrected with a known factor. Finally, the reproducibility of the results from the MR200 was tested. PMID:16735564

Zorko, B; Miljani?, S; Veki?, B; Stuhec, M; Gobec, S; Ranogajec-Komor, M

2006-05-30

182

Depth dose distribution measurement on the Foton-M2 bio-satellite by TLD technique  

NASA Astrophysics Data System (ADS)

In the framework of “Biology and Physics in Space” project of the European Space Agency (ESA), a returning satellite, Foton-M2, carried an open-to-space sample holder outside of the satellite body, called as BIOPAN-5, loaded with exo-biological experiments and dosemeters for RAdiation DOsimetry (RADO). One of the RADO experiments (Teflon TLD) was dedicated to dose distribution measurements of the cosmic radiation by thermo-luminescent (TL) technique. It was found that the maximum surface absorbed dose rate, averaged over the first ˜8 mg/cm2 thickness, was ˜2 Gy/d and showed a location dependence due the shading effect of the satellite construction elements. The dose rate decreased nearly by 3 orders of magnitude below 500 mg/cm2.

Fehér, I.; Pálfalvi, J. K.

2008-09-01

183

The use of gel dosimetry to measure the 3D dose distribution of a 90Sr/90Y intravascular brachytherapy seed.  

PubMed

Absorbed dose distributions in 3D imparted by a single (90)Sr/(90)Y beta particle seed source of the type used for intravascular brachytherapy were investigated. A polymer gel dosimetry medium was used as a dosemeter and phantom, while a special high-resolution laser CT scanner with a spatial resolution of 100 microm in all dimensions was used to quantify the data. We have measured the radial dose function, g(L)(r), observing that g(L)(r) increases to a maximum value and then decreases as the distance from the seed increases. This is in good agreement with previous data obtained with radiochromic film and thermoluminescent dosemeters (TLDs), even if the TLDs underestimate the dose at distances very close to the seed. Contrary to the measurements, g(L)(r) calculated through Monte Carlo simulations and reported previously steadily decreases without a local maximum as a function of the distance from the seed. At distances less than 1.5 mm, differences of more than 20% are observed between the measurements and the Monte Carlo calculations. This difference could be due to a possible underestimation of the energy absorbed into the seed core and encapsulation in the Monte Carlo simulation, as a consequence of the unknown precise chemical composition of the core and its respective density for this seed. The results suggest that g(L)(r) can be measured very close to the seed with a relative uncertainty of about 1% to 2%. The dose distribution is isotropic only at distances greater than or equal to 2 mm from the seed and is almost symmetric, independent of the depth. This study indicates that polymer gel coupled with the special small format laser CT scanner are valid and accurate methods for measuring the dose distribution at distances close to an intravascular brachytherapy seed. PMID:19242054

Massillon-Jl, G; Minniti, R; Mitch, M G; Maryanski, M J; Soares, C G

2009-02-25

184

An investigation of gamma background radiation in Hamadan province, Iran.  

PubMed

The general population, everywhere in the world is exposed to a small dose of ionising radiation from natural sources. Stochastic effects such as cancer and genetic disorders are caused when living creatures are exposed to low doses. In Iran, it is measured in some cities, especially in high-background areas such as Ramsar, but so far there is no measurement in the Hamadan province. Hamadan is located in the west of Iran. Measurements were performed using a RDS-110 survey meter, CaSO(4):Dy thermoluminecense dosimetries (TLDs) and a Harshaw 4000 TLD reader. To estimate the dose rate  outdoors, four stations along the main directions (north, south, west and east) and one in the town centre were selected. Mean annual X and gamma equivalent dose in Hamadan province are 1.12±0.22  and 1.66±0.07 mSv, which related to RDS-110 survey meter and TLDs measurements, respectively. The TLDs and RDS-110 results are representative of the external photon radiation doses for the selected monitoring locations and for those locations for the hours during which the measurements were taken, respectively. Maximum and minimum of external photon radiation doses are related to Hamadan and Kaboudar-Ahang towns, respectively. According to the results of the study, it seems that the annual X and gamma equivalent dose in Hamadan province exceeded the global mean external exposure amounts by the UNSCEAR, and further studies are needed to measure internal exposures to determine the total environmental radiation level in  Hamadan province. PMID:22570508

Rostampour, Nima; Almasi, Tinoosh; Rostampour, Masoumeh; Mohammadi, Mohammad; Ghazikhanlou Sani, Karim; Khosravi, Hamid R; Pooya, S Mehdi Hosseini; Golzar, Bahman; Jabari Vesal, Naghi

2012-05-07

185

The development, characterization, and performance evaluation of a new combination type personnel neutron dosimeter  

SciTech Connect

A new combination type personnel neutron dosimeter has been designed and developed at the Oak Ridge National Laboratory. The combination personnel neutron dosimeter (CPND) consists of a Harshaw albedo neutron thermoluminescent dosimeter and two bubble detectors. The CPND was developed with the aim of having crude neutron spectrometric capability, universal applicability, better angular response, and an improved lower limit of detection (LLD). The CPND has been well characterized in the following areas: reusability, linearity, LLD, detection capability in mixed neutron-gamma fields, angular dependence, and neutron energy dependence. The characterization was accomplished with irradiations using a {sup 238}Pu-Be source, a {sup 252}Cf(D{sub 2}O) source, a {sup 252}Cf source, a {sup 252}Cf(PE) source, monoenergetic neutrons from accelerator and reactor filtered beams, {sup 137}Cs, and X-rays. Optimum signal readout procedures, signal processing techniques, routine operational usage, and neutron dose equivalent evaluation algorithms for the CPND were developed. Various reference spectra were developed to evaluate the performance (mainly the spectrometric and the dose equivalent measurement capabilities) of the CPND. The performance of the CPND was evaluated by in-situ tests in radiation fields existing in the working environment at ORNL. The spectra in these areas were measured previously with a calibrated Bonner multisphere spectrometer. The CPND also was tested with laboratory radioisotopic sources in single-source and multi-source exposure situations. Finally, the CPND was tested by participating in the fourteenth Personnel Dosimetry Intercomparison Study. The results of the tests mentioned above demonstrated that the CPND meets the ambitious design purposes.

Liu, Chweijeng.

1989-01-01

186

Theoretical and practical implications of the effects of temperature during irradiation and during pre- and post-irradiation storage on the response of thermoluminescence dosimeters  

SciTech Connect

Experiments have been conducted to determine the applicability of the Randall-Wilkins theory for describing the behavior of CaF/sub 2/:Mn thermoluminescence dosimeters (Harshaw TLD-400 chips). Results were obtained for four different conditions: irradiation followed by storage, irradiation after storage, irradiation both preceded and followed by storage, and continuous simultaneous irradiation and storage. The experiments were performed for storage intervals of approximately 1, 2, 3, 5, 6 and 7 days at five different storage temperatures: -25, +20, +65, +150 and +175/sup 0/C. The results indicate fading that is described not by the Randall-Wilkins theory but rather as a linear function of the logarithm of the storage time. While the results suggest that the trapping efficiency is independent of temperature, they do demonstrate a small decrease in TL response with storage time prior to irradiation which is independent of temperature and time (>17 hours) and hence probably not dosimetric in origin but perhaps optically related. Glow curve analyses support the concept of a band of traps rather than a single trap. The overall results are compared to other data available in the literature most of which is for room-temperature storage. These data, for storage periods ranging from minutes to one year, can also be described as a linear function of the logarithm of the storage time and are remarkably consistent when uniformly normalized. Although peripheral experiments revealed problems associated with self-irradiation as well as a decline in sensitivity with use, the stability experiment results verify the highly favorable stability properties of CaF/sub 2/:Mn for widespread application.

Gail de Planque, E.

1984-01-01

187

Improving neutron dosimetry using bubble detector technology  

SciTech Connect

Providing accurate neutron dosimetry for a variety of neutron energy spectra is a formidable task for any dosimetry system. Unless something is known about the neutron spectrum prior to processing the dosimeter, the calculated dose may vary greatly from that actually encountered; that is until now. The entrance of bubble detector technology into the field of neutron dosimetry has eliminated the necessity of having an a priori knowledge of the neutron energy spectra. Recently, a new approach in measuring personnel neutron dose equivalent was developed at Oak Ridge National Laboratory. By using bubble detectors in combination with current thermoluminescent dosimeters (TLDs) as a Combination Personnel Neutron Dosimeter (CPND), not only is it possible to provide accurate dose equivalent results, but a simple four-interval neutron energy spectrum is obtained as well. The components of the CPND are a Harshaw albedo TLD and two bubble detectors with theoretical energy thresholds of 100 key and 1500 keV. Presented are (1) a synoptic history surrounding emergence of bubble detector technology, (2) a brief overview of the current theory on mechanisms of interaction, (3) the data and analysis process involved in refining the response functions, (4) performance evaluation of the original CPND and a reevaluation of the same data under the modified method, (5) the procedure used to determine the reference values of component fluence and dose equivalent for field assessment, (6) analysis of the after-modification results, (7) a critique of some currently held assumptions, offering some alternative explanations, and (8) thoughts concerning potential applications and directions for future research.

Buckner, M.A.

1993-02-01

188

[The application of non-annealing thermoluminescent dosimetry (TLD)].  

PubMed

Conventional use of Thermoluminescence (TL) in radiation dosimetry is very time-consuming. It requires repeating the procedures of preheating and annealing. In an attempt to simplify these procedures, we conducted an experiment of non-annealing TL dosimetry. This article reports the experiment's results. We adopted Lithium Fluoride (LiF) chip (TLD-100) in polystyrene under the exposure of Co-60, and the result was taken by HAR-SHAW-4000 TL reading system. The TL response was analyzed, including linearity, reproducibility and fading test. Because non-annealing TL response was greatly influenced by residual electron, TLD calibration curves were separated into two parts: (1) high dose region (HDR, 50-1500 cGy); (2) low dose region (LDR, 0-50 cGy). When TL dosimeters were exposed to a single high does (about 500 cGy), the HDR could be reproduced within 3% and fit a good linearity. For LDR, we had to give up the tail of glow curve in the high temperature region. We could then get good linearity and reproducibility. Furthermore, fading of non-annealing was apparently larger than annealing. We could control the fading of non-annealing was apparently larger than annealing. We could control the fading influence within 1% by taking the TL reading one hour after exposure. On the other hand, a combination of photon and electron exposure was also performed by non-annealing TL dosimetry. The results were compatible with Co-60 exposure in the same system. PMID:8339153

Wu, J M; Chen, C S; Lan, R H

1993-06-01

189

Mixed field peronnel dosimetry: Part 1, High temperature peak characteristics of the reader-annealed TLD-600  

SciTech Connect

The high temperature peaks (TL peaks 6--7) of TLD-600 are known to have higher responses to high LET radiation than to low LET radiation. These high temperature peak characteristics were studied for the automatic reader-annealed Harshaw albedo neutron TLD. The high temperature peaks response is linear for neutrons over the dose equivalent range tested (0.05--3 mSv of a {sup 252}Cf source moderated by a 15 cm radius polyethylene sphere), but is supralinear above 20 mSv of {sup 137}Cs photons. The peaks ratio (peaks 6--7/peaks 3--5) of TLD-600 is 0.15 for neutrons of any incident energy, 0.01 for {sup 137}Cs gammas, and 0.02 for M-150 x-rays. Based on the high temperature peak characteristics, a mixed field neutron-photon personnel dosimetry methodology using a single TLD-600 element was developed. The dosimetric method was evaluated in mixed {sup 238}PuBe + {sup 137}Cs fields with four neutron-gamma dose equivalent ratios, and the neutron, photon and total dose equivalent estimations are better than 20% except in one case. However, it was found that the neutron and photon dose equivalent estimations are sensitive to the neutron and photon peaks ratios, depending on the neutron-photon dose equivalent ratio and the neutron source in the mixed field. Therefore, a successful use of this method requires knowledge of the photon and neutron energies in the mixed field. 13 refs., 6 figs., 2 tabs.

Liu, J.C. (Stanford Linear Accelerator Center, Menlo Park, CA (USA)); Sims, C.S. (Oak Ridge National Lab., TN (USA))

1991-02-01

190

Past and future application of solid-state detectors in manned spaceflight.  

PubMed

The radiation exposure in space missions can be reduced by careful mission planning and appropriate measures, such as provision of a radiation shelter, but it cannot be eliminated. The reason for that is the high penetration capability of the radiation components owing to their high energies. Radiation is therefore an acknowledged primary concern for manned spaceflight and is a potentially limiting factor for long-term orbital and interplanetary missions. The radiation environment is a complex mixture of charged particles of solar and galactic origin and of the radiation belts, as well as of secondary particles produced in interactions of the galactic cosmic particles with the nuclei of atmosphere of the earth. The complexity even increases by placing a spacecraft into this environment owing to the interaction of the radiation components with the shielding material. Therefore it is a challenge to provide for appropriate measurements in this radiation field, coping with the limited resources on experiment power and mass. Solid-state dosemeters were already chosen for measurements in the first manned flights. Thermoluminescence dosemeters (TLDs) and plastic nuclear track detectors (PNTD) especially found a preferred application because they are light-weighted, need no power supply and they are tissue-equivalent. Most of the data available until 1996 were gathered by using these passive detectors; this especially holds for heavy ion particle spectra. The systems, supplemented by converter foils or fission detectors and bubble detectors, provide information on dose, particle flux-, energy- and linear energy transfer spectra of the ionising radiation and neutron fluxes and doses. From 1989, silicon detectors were used for dose and flux measurements and later on for particle spectrometry. Silicon detectors were demonstrated as a powerful tool for the description of space radiation environment. Optical simulated luminescence (OSL) detectors have now been introduced as a new system in space research. Both, OSL and superheated drop detectors are candidates for personal dosimetry systems. The article will summarise past results, and results of measurements performed recently on the ISS, and conclude with future aspects. PMID:16766573

Reitz, Guenther

2006-06-09

191

Personal Dose Equivalent Conversion Coefficients For Photons To 1 GEV  

SciTech Connect

The personal dose equivalent, H{sub p}(d), is the quantity recommended by the International Commission on Radiation Units and Measurements (ICRU) to be used as an approximation of the protection quantity Effective Dose when performing personal dosemeter calibrations. The personal dose equivalent can be defined for any location and depth within the body. Typically, the location of interest is the trunk where personal dosemeters are usually worn and in this instance a suitable approximation is a 30 cm X 30 cm X 15 cm slab-type phantom. For this condition the personal dose equivalent is denoted as H{sub p,slab}(d) and the depths, d, are taken to be 0.007 cm for non-penetrating and 1 cm for penetrating radiation. In operational radiation protection a third depth, 0.3 cm, is used to approximate the dose to the lens of the eye. A number of conversion coefficients for photons are available for incident energies up to several MeV, however, data to higher energies are limited. In this work conversion coefficients up to 1 GeV have been calculated for H{sub p,slab}(10) and H{sub p,slab}(3) using both the kerma approximation and by tracking secondary charged particles. For H{sub p}(0.07) the conversion coefficients were calculated, but only to 10 MeV due to computational limitations. Additionally, conversions from air kerma to H{sub p,slab}(d) have been determined and are reported. The conversion coefficients were determined for discrete incident energies, but analytical fits of the coefficients over the energy range are provided. Since the inclusion of air can influence the production of secondary charged particles incident on the face of the phantom conversion coefficients have been determined both in vacuo and with the source and slab immersed within a sphere in air. The conversion coefficients for the personal dose equivalent are compared to the appropriate protection quantity, calculated according to the recommendations of the latest International Commission on Radiological Protection (ICRP) guidance.

Veinot, K. G.; Hertel, N. E.

2010-09-27

192

The Development, Characterization, and Performance Evaluation of a New Combination Type Personnel Neutron Dosimeter  

NASA Astrophysics Data System (ADS)

A new combination type personnel neutron dosimeter has been designed and developed at the Oak Ridge National Laboratory (ORNL). The combination personnel neutron dosimeter (CPND) consists of a Harshaw albedo neutron thermoluminescent dosimeter (two pairs of TLD-600/TLD-700) and two bubble detectors (one BD-100R and one BDS-1500 from Bubble Technology Industries, Canada). The CPND was developed with the aim of having crude neutron spectrometric capability, universal applicability, better angular response, and an improved lower limit of detection (LLD). The CPND has been well characterized in the following areas: reusability, linearity, lower limit of detection (LLD), detection capability in mixed neutron-gamma fields, angular dependence, and neutron energy dependence. The characterization was accomplished with irradiations using a ^{238} Pu-Be source, a ^{252} Cf(D_2O) source, a ^{252}Cf source, a ^ {252}Cf(PE) source, monoenergetic neutrons from accelerator and reactor filtered beams, ^ {137}Cs, and X-rays. Optimum signal readout procedures, signal processing techniques, routine operational usage, and neutron dose equivalent evaluation algorithms for the CPND were developed with the goals of having the best precision and accuracy as well as being convenient to use. Various reference spectra were developed to evaluate the performance (mainly the spectrometric and the dose equivalent measurement capabilities) of the CPND. The performance of the CPND was evaluated by in-situ tests in radiation fields existing in the working environment at ORNL. The spectra in these areas were measured previously with a calibrated Bonner multisphere spectrometer. The CPND also was tested with laboratory radioisotopic sources in single-source and multi-source exposure situations. Finally, the CPND was tested by participating in the fourteenth Personnel Dosimetry Intercomparison Study. The results of the tests mentioned above demonstrated that the CPND meets the ambitious design purposes. Because of its 4 -interval spectrometric capability and high sensitivity, the CPND can be used, without prior knowledge of the spectrum or calibration in the field, to provide accurate dose equivalent estimates. The results of the detailed characterization and performance tests showed that the new CPND is an excellent personnel neutron dosimeter.

Liu, Chwei-Jeng

193

A national programme for patient and staff dose monitoring in interventional cardiology.  

PubMed

A national programme on patient and staff dose evaluation in interventional cardiology made in cooperation with the haemodynamic section of the Spanish Society of Cardiology has recently been launched. Its aim is to propose a set of national diagnostic reference levels (DRLs) for patients as recommended by the International Commission on Radiological Protection and to initiate several optimisation actions to improve radiological protection of both patients and staff. Six hospitals have joined the programme and accepted to submit their data to a central database. First to be acquired were the quality control data of the X-ray systems and radiation doses of patients and professionals. The results from 9 X-ray systems, 1467 procedures and staff doses from 43 professionals were gathered. Provisional DRLs resulted in 44 Gy cm(2) for coronary angiography and 78 Gy cm(2) for interventions. The X-ray systems varied up to a factor of 5 for dose rates in reference conditions. Staff doses showed that 50 % of interventional cardiologists do not use their personal dosemeters correctly. PMID:21733862

Sánchez, R; Vano, E; Fernández, J M; Sotil, J; Carrera, F; Armas, J; Rosales, F; Pifarre, X; Escaned, J; Angel, J; Diaz, J F; Bosa, F; Saez, J R; Goicolea, J

2011-07-05

194

Dose distribution for dental cone beam CT and its implication for defining a dose index  

PubMed Central

Objectives To characterize the dose distribution for a range of cone beam CT (CBCT) units, investigating different field of view sizes, central and off-axis geometries, full or partial rotations of the X-ray tube and different clinically applied beam qualities. The implications of the dose distributions on the definition and practicality of a CBCT dose index were assessed. Methods Dose measurements on CBCT devices were performed by scanning cylindrical head-size water and polymethyl methacrylate phantoms, using thermoluminescent dosemeters, a small-volume ion chamber and radiochromic films. Results It was found that the dose distribution can be asymmetrical for dental CBCT exposures throughout a homogeneous phantom, owing to an asymmetrical positioning of the isocentre and/or partial rotation of the X-ray source. Furthermore, the scatter tail along the z-axis was found to have a distinct shape, generally resulting in a strong drop (90%) in absorbed dose outside the primary beam. Conclusions There is no optimal dose index available owing to the complicated exposure geometry of CBCT and the practical aspects of quality control measurements. Practical validation of different possible dose indices is needed, as well as the definition of conversion factors to patient dose.

Pauwels, R; Theodorakou, C; Walker, A; Bosmans, H; Jacobs, R; Horner, K; Bogaerts, R

2012-01-01

195

Thermoluminescence properties of Li2CO3-K2CO3-H3BO3glass system co-doped with CuO and MgO.  

PubMed

The thermoluminescent properties of boric glass modified with lithium and potassium carbonates (LKB) and co-doped with CuO and MgO are reported for the first time. Two techniques are applied to investigate the effect of dopants and co-dopants on the thermal stimulation properties of LKB. The induced TL glow curves of a CuO-doped sample are found to be at 220°C with a single peak. An enhancement of about three times is shown with the increment of 0.1 mol % MgO as a co-dopant impurity. This enhancement may contribute to the ability of magnesium to create extra electron traps and consequently the energy transfer to monovalent Cu(+) ions. LKB:Cu,Mg is low Z material (Zeff=8.55), and observed 15 times less sensitive than LiF: Mg, Ti (TLD-100). The proposed dosemeter showed good linearity in TL dose-response, low fading and excellent reproducibility with a simple glow curve, and thus, can be used in the radiation dosimetry. PMID:23193136

Alajerami, Yasser Saleh Mustafa; Hashim, Suhairul; Ramli, Ahmad Termizi; Saleh, Muneer Aziz; Kadni, Taiman

2012-11-28

196

The effects of high ambient radon on thermoluminescence dosimetry readings.  

PubMed

The effect of a high level of ambient (222)Rn gas on thermoluminescence dosemeters (TLDs) is examined. Groups of LiF:Mg,Ti and CaF(2):Dy TLDs were exposed to (222)Rn under controlled environmental conditions over ?7 d using a luminous (226)Ra aircraft dial. LiF:Mg,Ti TLDs were tested bare, and both types were tested mounted in cards used for environmental dosimetry and mounted in cards enclosed in plastic badges. A passive continuous radon monitor was used to measure the (222)Rn level in the small chamber during the experiments. The data were analysed to determine the relationship between the integrated (222)Rn level and the TLD response. Although both LiF:Mg,Ti and CaF(2):Dy TLDs showed a strong response to (222)Rn, the badges prevented measurable radon detection by the TLDs within. The TLDs were not used to directly measure the radon concentration; rather, a correction for its influence was desired. PMID:21177272

Harvey, John A; Kearfott, Kimberlee J

2010-12-20

197

Monitoring of radon gas in caves of the Yorkshire Dales, United Kingdom.  

PubMed

A number of vocational training courses are held in caves in the Yorkshire Dales region of the United Kingdom. The instructors and students involved in these courses have the potential to be exposed to enhanced levels of radon ((222)Rn) and its progeny as a result of their occupations. A prior radiological risk assessment for the training courses recommended that an environmental monitoring programme be carried out to establish the radon concentrations in the caves, and that the caving instructors wear personal radon dosemeters. Radon gas concentrations varied seasonally, being at their highest in summer and their lowest in winter. The lowest result was 40  Bq m(-3) recorded in Lower Longchurn cave during winter, whilst the highest result was 4440  Bq m(-3) recorded in Crackpot cave during the summer. As the individuals involved in the caving are entering atmospheres with radon gas concentrations in excess of 400  Bq m(-3), the Ionising Radiation Regulations 1999 (GB Parliament 2000 Ionising Radiations Regulations 1999 (London: Stationary Office) SI 1999/3232) apply. A system of work is therefore in place to control exposure to radon. This system of work stipulates an initial dose investigation level of 1 mSv, a second dose investigation level of 2 mSv and an annual dose limit of 6 mSv. The highest annual dose recorded to date is 2.2 mSv, although the average (median) annual dose is only 0.5 mSv. PMID:20826896

Langridge, D; Stokes, R P; Jackson, C P

2010-09-08

198

Measurements of X ray absorbed doses to dental patients in two dental X ray units in Nigeria.  

PubMed

Measurements of absorbed doses from radiographic examinations to various anatomical sites in the head and neck of patients with an average age of 45 years using intra-oral dental radiography have been carried out. LiF (TLD-100) dosemeters were used for the measurements of the absorbed dose. The measured absorbed doses to the various anatomical sites in the two units are reported, discussed and compared with results from the literature. Quality control measurements were also performed using a Victoreen quality control test device on the X ray units. The tube voltage accuracies for the two units were found to be within acceptable limits (less than +/- 10%). On the other hand the exposure time accuracies for these units have large deviations (>20%). These results and those that have been reported in the literature may be an indication that high patient doses are common in most dental X ray centres and countries. As a result of this, regular compliance and performance checks of dental diagnostic X ray equipment are essential in order to ensure proper performance and to minimise unnecessary patient and operator doses. PMID:12474946

Ogundaret, F O; Oni, O M; Balogun, F A

2002-01-01

199

Seasonal variation of indoor radon-222 levels in dwellings in Ramallah province and East Jerusalem suburbs, Palestine.  

PubMed

This study presents the seasonal variations of indoor radon levels in dwellings located in the Ramallah province and East Jerusalem suburbs, Palestine. The measurements were performed during the summer and winter of the year 2006/2007 using CR-39 solid-state-nuclear-track detectors. The total number of investigated buildings is 75 in summer and 81 in winter. A total number of 142 dosemeters are installed in dwellings for each season for a period of almost 100 d. The radon concentration levels in summer varied from 43 to 192 Bq m(-3) for buildings in the Ramallah province and from 30 to 655 Bq m(-3) for East Jerusalem suburbs. In winter, the radon concentration levels are found to vary from 38 to 375 Bq m(-3) in the Ramallah buildings and from 35 to 984 Bq m(-3) in East Jerusalem suburbs. The obtained results for radon concentration levels in most places are found to be within the accepted international levels. PMID:21335630

Leghrouz, Amin A; Abu-Samreh, Mohammad M; Shehadeh, Ayah K

2011-02-20

200

Physician-received scatter radiation with angiography systems used for interventional radiology: comparison among many X-ray systems.  

PubMed

Radiation protection for interventional radiology (IR) physicians is very important. Current IR X-ray systems tend to use flat-panel detectors (FPDs) rather than image intensifiers (IIs). The purpose of this study is to test the hypothesis that there is no difference in physician-received scatter radiation (PRSR) between FPD systems and II systems. This study examined 20 X-ray systems in 15 cardiac catheterisation laboratories (11 used a FPD and 9 used an II). The PRSR with digital cineangiography and fluoroscopy were compared among the 20 X-ray systems using a phantom and a solid-state-detector electronic pocket dosemeter. The maximum PRSR exceeded the minimum PRSR by ~12-fold for cineangiography and ~9-fold for fluoroscopy. For both fluoroscopy and digital cineangiography, the PRSR had a statistically significant positive correlation with the entrance surface dose (fluoroscopy, r = 0.87; cineangiography, r = 0.86). There was no statistically significant difference between the average PRSR of FPDs and IIs during either digital cineangiography or fluoroscopy. There is a wide range of PRSR among the radiography systems evaluated. The PRSR correlated well with the entrance surface dose of the phantom in 20 X-ray units used for IR. Hence, decreasing the dose to the patient will also decrease the dose to staff. PMID:22117021

Chida, Koichi; Morishima, Yoshiaki; Inaba, Youhei; Taura, Masaaki; Ebata, Ayako; Takeda, Ken; Shimura, Hirotaka; Zuguchi, Masayuki

2011-11-23

201

Characteristics of the neutron field of the facility at DIN-UPM.  

PubMed

A new source facility (241Am-Be) has been installed in a bunker-type room of large dimensions. To characterise the neutron fields in the facility, detailed calculations have been made with MCNP-4C, showing the different components of the neutron radiation reaching the reference points (direct, inscattered, backscattered). The contribution from neutrons scattered in the walls to the total ambient dose equivalent remains reasonably low (<10%) in the reference points. Additionally, spectra measurements have been performed with a Bonner spheres spectrometer with a 6LiI(Eu) scintillator (0.4 phi x 0.4 cm2), UTA4 response matrix and BUNKIUT unfolding code. The calculated and experimentally obtained spectra are compared, with small differences found in the epithermal and thermal region, attributable to the concrete composition used in the calculations. The H*(10) rate has been determined from the spectra, and then compared to the reading of an active dosemeter (LB6411), with differences found lower than 8%. PMID:15353625

Gallego, E; Lorente, A; Vega-Carrillo, H R

2004-01-01

202

An assessment of lead eyewear in interventional radiology.  

PubMed

The International Commission on Radiological Protection (ICRP) has recently issued a proposal to reduce the occupational eye dose limit from 150 to 20 mSv. A series of experiments has been performed to determine the level of protection from scattered radiation afforded to the interventional radiology operator by protective lead glasses, taking into account variation in operator position and angle of head rotation. The lenses of the glasses have a lead equivalence of 0.75 mm lead with 0.5 mm lead present in the side shields. Our results have led us to propose the use of a general dose reduction factor of 5 when using eyewear with this lead equivalence and construction. We have also concluded that the forehead of the wearer provides the most robust position to site a dosemeter that will be used to estimate the dose to both eyes as part of a personal monitoring regime. We have confirmed that backscatter from the head itself is the limiting factor for the dose reduction potential of lead eyewear. PMID:23803599

McVey, S; Sandison, A; Sutton, D G

2013-06-27

203

Organ and effective doses from verification techniques in image-guided radiotherapy.  

PubMed

The purpose of this work was an evaluation of organ doses and effective doses from three verification techniques in Image-Guided Radiotherapy: from kilovoltage (kV) cone beam computed tomography (CBCT) scans, from two orthogonal kV images and from two orthogonal megavoltage (MV) images for two different treatment sites: pelvis and head and neck (H&N). For comparison reasons, organ doses and effective doses from prostate and H&N radiotherapy were also evaluated. Measurements of organ doses were performed in a male anthropomorphic Rando phantom by means of thermoluminescent dosemeters. In this investigation, measured organ doses from one CBCT scan, from two MV images and from two kV images of pelvis represent typically 1-6, 1-10 and 0.05-1 %, respectively, of organ doses resulting from one fraction of prostate radiotherapy. The maximum effective doses from CBCT scans, kV images and MV images of pelvis are 5.6, 0.8 and 11.9 mSv, respectively. PMID:21816726

Dufek, V; Horakova, I; Novak, L

2011-08-04

204

Tests of shielding effectiveness of Kevlar and Nextel onboard the International Space Station and the Foton-M3 capsule.  

PubMed

Radiation assessment and protection in space is the first step in planning future missions to the Moon and Mars, where mission and number of space travelers will increase and the protection of the geomagnetic shielding against the cosmic radiation will be absent. In this framework, the shielding effectiveness of two flexible materials, Kevlar and Nextel, were tested, which are largely used in the construction of spacecrafts. Accelerator-based tests clearly demonstrated that Kevlar is an excellent shield for heavy ions, close to polyethylene, whereas Nextel shows poor shielding characteristics. Measurements on flight performed onboard of the International Space Station and of the Foton-M3 capsule have been carried out with special attention to the neutron component; shielded and unshielded detectors (thermoluminescence dosemeters, bubble detectors) were exposed to a real radiation environment to test the shielding properties of the materials under study. The results indicate no significant effects of shielding, suggesting that thin shields in low-Earth Orbit have little effect on absorbed dose. PMID:20364264

Pugliese, M; Bengin, V; Casolino, M; Roca, V; Zanini, A; Durante, M

2010-04-03

205

Novel shielding materials for space and air travel.  

PubMed

The reduction of dose onboard spacecraft and aircraft by appropriate shielding measures plays an essential role in the future development of space exploration and air travel. The design of novel shielding strategies and materials may involve hydrogenous composites, as it is well known that liquid hydrogen is most effective in attenuating charged particle radiation. As precursor for a later flight experiment, the shielding properties of newly developed hydrogen-rich polymers and rare earth-doped high-density rubber were tested in various ground-based neutron and heavy ion fields and compared with aluminium and polyethylene as reference materials. Absorbed dose, average linear energy transfer and gamma-equivalent neutron absorbed dose were determined by means of LiF:Mg,Ti thermoluminescence dosemeters and CR-39 plastic nuclear track detectors. First results for samples of equal aerial density indicate that selected hydrogen-rich plastics and rare-earth-doped rubber may be more effective in attenuating cosmic rays by up to 10% compared with conventional aluminium shielding. The appropriate adaptation of shielding thicknesses may thus allow reducing the biologically relevant dose. Owing to the lower density of the plastic composites, mass savings shall result in a significant reduction of launch costs. The experiment was flown as part of the European Space Agency's Biopan-5 mission in May 2005. PMID:16717109

Vana, N; Hajek, M; Berger, T; Fugger, M; Hofmann, P

2006-05-22

206

Geant4 simulation of the CERN-EU high-energy reference field (CERF) facility.  

PubMed

The CERN-EU high-energy reference field facility is used for testing and calibrating both active and passive radiation dosemeters for radiation protection applications in space and aviation. Through a combination of a primary particle beam, target and a suitable designed shielding configuration, the facility is able to reproduce the neutron component of the high altitude radiation field relevant to the jet aviation industry. Simulations of the facility using the GEANT4 (GEometry ANd Tracking) toolkit provide an improved understanding of the neutron particle fluence as well as the particle fluence of other radiation components present. The secondary particle fluence as a function of the primary particle fluence incident on the target and the associated dose equivalent rates were determined at the 20 designated irradiation positions available at the facility. Comparisons of the simulated results with previously published simulations obtained using the FLUKA Monte Carlo code, as well as with experimental results of the neutron fluence obtained with a Bonner sphere spectrometer, are made. PMID:20511404

Prokopovich, D A; Reinhard, M I; Cornelius, I M; Rosenfeld, A B

2010-05-28

207

41Ca - a possible neutron specific biomarker in tooth enamel  

NASA Astrophysics Data System (ADS)

The measurement of long-lived radionuclides, produced by neutrons originating from the atomic-bomb explosions, offers the possibility to reconstruct neutron fluences to which survivors in Hiroshima and Nagasaki were exposed. The long-lived radionuclide, 41Ca (T1/2=103000 years), is suggested here as a means for a retrospective determination of thermal neutron fluences, directly within the human body of a survivor. As proper material tooth enamel is proposed. The 41Ca signal in tooth enamel may be correlated with the exposure to A-bomb induced thermal neutron fluences, provided the natural background level of 41Ca/Ca is significantly lower. Therefore, tooth samples of unexposed survivors of the A-bomb explosions have been examined by means of accelerator mass spectrometry, in order to quantify the natural background level of 41Ca/Ca. Measured 41Ca/Ca ratios were confirmed to be as low as about 2×10-15. Thus, the A-bomb induced additional signal should be detectable for survivors at epidemiological relevant distances. Since tooth enamel had already been used as a dosemeter for gamma radiation from the A-bomb explosion, the detection of 41Ca in tooth enamel would allow, for the first time, an assessment of both, ?-ray and neutron exposures in the same biological material.

Wallner, A.; Arazi, A.; Faestermann, T.; Knie, K.; Korschinek, G.; Maier, H. J.; Nakamura, N.; Rühm, W.; Rugel, G.

2004-08-01

208

Radiation measurements around X-ray cabinet systems.  

PubMed

Security personnel who operate X-ray units for the control of hand luggage and personal items at airports are generally not under dosimetric surveillance. A significant increase in the number of inspected items per passenger, due to rigorous air traffic security measures, raises a question of extended exposure of these workers to scattered X-ray radiation. A new approach to investigating directions of breaches of scattered X-ray radiation in the area near to an X-ray cabinet system, which is based on using active electronic dosemeters is presented. Influence of the increase in the number of inspected items in time on the dose rate is described. Time-dependent dose rates have showed a very good correlation with passengers undergoing security control prior to boarding an airplane. Measurements confirmed that an increase in the dose rate, coinciding with rush hours, was caused by scattered radiation passing through incompletely closed lead curtains. It is found that the doses at the entrance to the inspection tunnel are 50% higher than those at the exit, which is a consequence of inherent operational characteristics of X-ray cabinet systems. PMID:22302108

Suric Mihic, M; Vucic, Z; Prlic, I; Lulic, I; Mestrovic, T

2012-02-01

209

Microdosemeter instrument (MIDN) for assessing risk in space.  

PubMed

Radiation in space generally produces higher dose rates than that on the Earth's surface, and contributions from primary galactic and solar events increase with altitude within the magnetosphere. Presently, no personnel monitor is available to astronauts for real-time monitoring of dose, radiation quality and regulatory risk. This group is developing a prototypic instrument for use in an unknown, time-varying radiation field. This microdosemeter-dosemeter nucleon instrument is for use in a spacesuit, spacecraft, remote rover and other applications. It provides absorbed dose, dose rate and dose equivalent in real time so that action can be taken to reduce exposure. Such a system has applications in health physics, anti-terrorism and radiation-hardening of electronics as well. The space system is described and results of ground-based studies are presented and compared with predictions of transport codes. An early prototype in 2007 was successfully launched, the only solid-state microdosemeter to have flown in space. PMID:21199825

Pisacane, V L; Dolecek, Q E; Malak, H; Cucinotta, F A; Zaider, M; Rosenfeld, A B; Rusek, A; Sivertz, M; Dicello, J F

2011-01-02

210

Neutron dose distribution at the GSI fragment separator.  

PubMed

GSI is operating a facility for the production of rare isotopes. Nuclei are produced by fragmentation or fission of the impinging heavy ions with energies of approximately 1 GeV per nucleon. The major part of the primary beam and the produced nuclei is deposited in the components of the Fragment Separator (FRS) and generates neutron radiation. Thermoluminescence dosemeters (TLDs) (6LiF/7LiF pairs in PE spheres) were exposed in neutron fields produced by uranium beams with energies between 100 and 1000 MeV per nucleon during an irradiation period in the year 2002. Two-dimensional dose distributions are obtained using these TL measurements in combination with model calculations. The applied model describes the dose distribution as a superposition of dose patterns of 20 single sources equally distributed along the FRS. The single source distribution is based on a measured double differential neutron distribution for a 1 GeV per nucleon uranium beam. PMID:15353740

Fehrenbacher, G; Festag, J G

2004-01-01

211

Neural network modelling of dose distribution and dose uniformity in the Tunisian Gamma Irradiator.  

PubMed

In this paper an approach to model dose distributions, isodose curves and dose uniformity in the Tunisian Gamma Irradiation Facility using artificial neural networks (ANNs) are described. For this purpose, measurements were carried out at different points in the irradiation cell using polymethyl methacrylate dosemeters. The calculated and experimental results are compared and good agreement is observed showing that ANNs can be used as an efficient tool for modelling dose distribution in the gamma irradiation facility. Monte Carlo (MC) photon-transport simulation techniques have been used to evaluate the spatial dose distribution for extensive benchmarking. ANN approach appears to be a significant advance over the time-consuming MC or the less accurate regression methods for dose mapping. As a second application, a detailed dose mapping using two different product densities was carried out. The minimum and maximum dose locations and dose uniformity as a function of the irradiated volume for each product density were determined. Good agreement between ANN modelling and experimental results was achieved. PMID:23633649

Manai, K; Trabelsi, A

2013-04-29

212

Radiation damage induced by krypton ions in sintered alpha-Al2O3.  

PubMed

Alpha-alumina is a useful thermoluminescence (TL) dosemeter. The knowledge of its behaviour under irradiation is thus of primary importance. The purpose of this paper is to characterise the radiation damage produced by swift krypton ions using various experimental methods, namely TL, optical absorption, fluorescence and electron paramagnetic resonance (EPR). After ion irradiation, the TL intensity is shown to decrease, whereas the optical absorption rises in the whole studied wavelength range. These two phenomena seem to be related to one another. Furthermore, optical absorption measurements highlight the appearance of new absorption bands probably owing to oxygen vacancies. Induced defects are also observed in the EPR spectra of irradiated pellets. They are likely related to electronic holes trapped on oxygen ions. The concentration of these defects increases with ion fluence and fluorescence measurements indicate that some pre-existing defects such as F2(2+) centres follow the same trend up to approximately 4.1 x 10(13) ions cm(-2). PMID:16644989

Dalmasso, C; Iacconi, P; Beauvy, M; Lapraz, D; Balan, E; Calas, G

2006-04-27

213

Quality assurance of environmental gamma radiation monitoring in Slovenia.  

PubMed

Environmental gamma radiation monitoring established in Slovenia consists of a network of multifunctional gamma monitors (MFMs) based on pairs of Geiger-Müller counters and a network of measuring sites with high-sensitive thermoluminiscence dosemeters. The measuring points are evenly spread across Slovenia, located at the meteorological stations and more densely on additional locations around the Krsko NPP. The MFM network has a 2-fold function with one sensor used for the purpose of early warning system in near surroundings of the NPP and the other, more sensitive, for natural radiation monitoring. The paper summarises activities to establish quality assurance of the environmental gamma radiation measurements in Slovenia, with a critical view of the results in comparison with the international standards and recommendations. While the results of linearity and energy dependence tests were satisfying, on-field intercomparison showed that the inherent signal of one of the monitors (MFM) has to be taken into account in the range of environmental background radiation. PMID:16410289

Stuhec, M; Zorko, B; Miti?, D; Miljani?, S; Ranogajec-Komor, M

2006-01-12

214

An evaluation of in-plane shields during thoracic CT.  

PubMed

The object of this study was to compare organ dose and image quality effects of using bismuth and barium vinyl in-plane shields with standard and low tube current thoracic CT protocols. A RANDO phantom was scanned using a 64-slice CT scanner and three different thoracic protocols. Thermoluminescent dosemeters were positioned in six locations to record surface and absorbed breast and lung doses. Image quality was assessed quantitatively using region of interest measurements. Scanning was repeated using bismuth and barium vinyl in-plane shields to cover the breasts and the results were compared with standard and reduced dose protocols. Dose reductions were most evident in the breast, skin and anterior lung when shielding was used, with mean reductions of 34, 33 and 10 % for bismuth and 23, 18 and 11 % for barium, respectively. Bismuth was associated with significant increases in both noise and CT attenuation values for all the three protocols, especially anteriorly and centrally. Barium shielding had a reduced impact on image quality. Reducing the overall tube current reduced doses in all the locations by 20-27 % with similar increases in noise as shielding, without impacting on attenuation values. Reducing the overall tube current best optimises dose with minimal image quality impact. In-plane shields increase noise and attenuation values, while reducing anterior organ doses primarily. Shielding remains a useful optimisation tool in CT and barium is an effective alternative to bismuth especially when image quality is of concern. PMID:23460031

Foley, S J; McEntee, M F; Rainford, L A

2013-03-03

215

Radiation Exposure to Patient and Staff in Hepatic Chemoembolization: Risk Estimation of Cancer and Deterministic Effects  

SciTech Connect

The purpose of the study was to determine the risks of radiation-induced cancer and deterministic effects for the patient and staff in transarterial chemoembolization (TACE) of hepatocellular carcinoma (HCC). Sixty-five patients with HCC underwent the first cycle of TACE. Thermoluminescence dosemeters and conversion factors were used to measure surface doses and to calculate organ doses and effective dose. For the patient, the risk of fatal cancer and severe genetic defect was in the magnitude of 10{sup -4} and 10{sup -5}, respectively. Five patients showed surface doses over the first lumbar vertebra exceeding 2000 mSv and 45 patients showed doses over the spine or the liver region above 500 mSv. The risk of fatal cancer and severe genetic defect for the radiologist and assistant was in the magnitude of 10{sup -7} to 10{sup -8}. They could exceed the threshold for lens opacity in the case of more than 490 and 1613 TACE yearly for a period of many years, respectively. Radiation dose could lead to local transient erythema and/or local depression of hematopoiesis in many patients after TACE. For the radiologist and assistant, risk of fatal cancer and genetic defect and lens opacity might arise when they perform interventions such as TACE intensively.

Hidajat, Nico, E-mail: nico.hidajat@gmx.de; Wust, Peter; Felix, Roland; Schroeder, Ralf Juergen [Charite Campus Virchow-Klinikum, Humboldt-University of Berlin, Department of Radiology (Germany)

2006-10-15

216

Dosimetric characterization of a brachytherapy source for gynaecological applications  

NASA Astrophysics Data System (ADS)

In this work Monte Carlo calculations and experimental measurements of dose rate in water per unit air-kerma strength, ?/Sk, of a low dose rate Amersham CDCS.J 137Cs source are reported. The Monte Carlo calculations included a detailed simulation of the geometric structure of the source embedded in a water medium. The experimental procedure included the construction of a lucite phantom with the same geometric characteristics as the one used in the simulation. Dose measurements were performed using high spatial resolution RadioChromic dye film and TL dosemeters for short and large distances from the source, respectively. The comparison between simulated and reported values in the literature of ?/Sk for the same source are of 1.0% in average [1]. The differences between the TL measurements and the simulation also are of 1% in average, while the difference between the MC and the RadioChromic film are larger, particularly when the RadioChromic film received doses smaller than 7 Gy. .

Rodríguez-Villafuerte, M.; Arzamendi, S.; Díaz-Perches, R.

2001-10-01

217

Radiation protection in fixed PET/CT facilities--design and operation  

PubMed Central

We describe the design of a fixed positron emission tomography (PET)/CT facility and the use of a simulated instantaneous dose-rate plot to visually highlight areas of potentially high radiation exposure. We also illustrate the practical implementation of basic radiation protection principles based on the use of distance and shielding and the minimisation of time spent in hot areas. Staff whole body doses for 4 years are presented with results of an optimisation study analysing the dose arising from the different phases within each study using direct reading dosemeters. The total whole body dose for all staff for each patient fell from 9.5 ?Sv in the first full year of operation to 4.8 µSv in 2008. The maximum dose to an individual member of staff per patient decreased over the same period from 3.2 to 0.9 µSv. The optimisation study showed that the highest dose was recorded during the injection phase.

Peet, D J; Morton, R; Hussein, M; Alsafi, K; Spyrou, N

2012-01-01

218

A study of environmental radioactivity measurements in the Samsun province, Turkey.  

PubMed

This study was concerned with the measurement of natural and artificial radionuclides in soil samples and indoor radon concentrations in the Samsun province, Turkey. In soil samples, the values of individual mean activity of (226)Ra, (232)Th, (40)K and (137)Cs radionuclides were found to be 31, 22, 341 and 16 Bq kg(-1), respectively. The radiological parameters, such as the absorbed dose rate in air, the annual effective dose (AED) and excess lifetime cancer risk, were calculated. Indoor radon measurements were carried out with CR-39-based radon dosemeters at 127 dwellings in the Samsun province. The mean annual (222)Rn activity was found to be 106 Bq m(-3) (equivalent to an AED of 1.88 mSv). The seasonal variation of (222)Rn activity shows that maximum levels are observed in the winter, while minimum levels are observed in the summer. The mean lifetime fatality risk for the studied area was estimated at 1.45×10(-4). The results obtained did not significantly differ from those obtained in other parts of the country. PMID:22619352

Kucukomeroglu, B; Maksutoglu, F; Damla, N; Cevik, U; Celebi, N

2012-05-22

219

Eye lens dosimetry in interventional cardiology: results of staff dose measurements and link to patient dose levels.  

PubMed

Workers involved in interventional cardiology procedures receive high eye lens dose if protection is not used. Currently, there is no suitable method for routine use for the measurement of eye dose. Since most angiography machines are equipped with suitable patient dosemeters, deriving factors linking staff eye doses to the patient doses can be helpful. In this study the patient kerma-area product, cumulative dose at an interventional reference point and eye dose in terms of Hp(3) of the cardiologists, nurses and radiographers for interventional cardiology procedures have been measured. Correlations between the patient dose and the staff eye dose were obtained. The mean eye dose was 121 µSv for the first operator, 33 µSv for the second operator/nurse and 12 µSv for radiographer. Normalised eye lens doses per unit kerma-area product were 0.94 µSv Gy?¹ cm?² for the first operator, 0.33 µSv Gy?¹ cm?² for the second operator/nurse and 0.16 µSv Gy?¹ cm?² for radiographers. Statistical analysis indicated that there is a weak but significant (p < 0.01) correlation between the eye dose and the kerma-area product for all three staff categories. These values are based on a local practice and may provide useful reference for other studies for validation and for wider utilisation in assessing the eye dose using patient dose values. PMID:23152146

Antic, V; Ciraj-Bjelac, O; Rehani, M; Aleksandric, S; Arandjic, D; Ostojic, M

2012-11-14

220

Low-dose radiation hyper-radiosensitivity in multicellular tumour spheroids  

PubMed Central

Objective We propose and study a new model aimed at describing the low-dose hyper-radiosensitivity phenomenon appearing in the survival curves of different cell lines. Methods The model uses the induced repair assumption, considering that the critical dose at which this mechanism begins to act varies from cell to cell in a given population. The model proposed is compared with the linear-quadratic model and the modified linear-quadratic model, which is commonly used in literature and in which the induced repair is taken into account in a heuristic way. The survival curve for the MCF-7 line of human breast cancer is measured at low absorbed doses and the uncertainties in these doses are estimated using thermoluminiscent dosemeters. Results It is shown that these multicellular spheroids present low-dose hyper-radiosensitivity. The new model permits an accurate description of the data of two human cell lines (previously published) and of the multicellular spheroids of the MCF-7 line here measured. Conclusion The model shows enough flexibility to account for data with very different characteristics and considers in a faithful way the hypothesis of the repair induction.

Guirado, D; Aranda, M; Ortiz, M; Mesa, J A; Zamora, L I; Amaya, E; Villalobos, M; Lallena, A M

2012-01-01

221

The MATROSHKA Experiment - First Mission Results  

NASA Astrophysics Data System (ADS)

MATROSHKA is an ESA multi-user experiment unit on the International Space Station ISS for studies of depth dose distribution of the different components of the orbital radiation field at different sites of the organs, occurring in astronauts being exposed during an EVA. To accomplish that, the facility comprises an anthropomorphic phantom to simulate the human body, active and passive detectors for space radiation dosimetry, data acquisition and processing electronics and the overall mechanical housing and support structure for the MATROSHKA components. The development and manufacture was under ESA contract by DLR, Institute for Aerospace Medicine with sub-contractors Kayser Italia (Livorno) and DTM (Modena). MATROSHKA was launched within PROGRESS on January 29, 2004 and mounted shortly afterwards outside the Russian Zvezda Module of the Station. The time of outside exposure during this mission phase was 539 days. After that, the facility was returned into the Station for passive sensor exchange. After the first passive detector set was returned to ground with Soyuz for on-ground evaluation the facility is further used inside the station during two follow-on project phases. The MATROSHKA experiment delivered a unique set of data results from the evaluation of numerous detectors, such as Thermoluminescence detectors, plastic nuclear track detectors and silicon dosemeters. This paper intends to give besides a short overview of the instrumentation used inside the MATROSHKA facility selected results from the first exposure and describes the determination of organ dose equivalents from these results

Reitz, Guenther

222

The MATROSHKA Facility - History and science overview  

NASA Astrophysics Data System (ADS)

The ESA MATROSHKA facility was realized through the German Aerospace Center DLR Cologne as main contractor On the 29th of January 2004 the facility was launched with a Russian PROGRESS vehicle to the International Space Station It was installed outside the Russian segment Zvezda on the 26th February 2004 and remained there until August 2005 and simulates as exact as possible an astronaut during an extravehicular activity EVA The MATROSHKA facility basically consists of a human phantom a Base Structure and a Container The container as well as the phantom is mounted to the base structure which serves as a footprint for the human phantom The container is a Carbon Fiber structure and forms with the Base Structure a closed volume that contains a dry oxygen atmosphere and protects the phantom against e g space vacuum space debris solar UV and material off-gassing It acts also as a simulation of the space suit The phantom body is made of commercial phantom parts well introduced in the field of radiotherapy It consists of 33 slices composed of natural bones embedded in tissue equivalent plastic of different density for tissue and lung The Phantom slices are equipped with channels and cut-outs to allow the accommodation of active and passive dosemeters temperature and pressure sensors The radiation experiments accommodated in the facility are performed under leadership of DLR in a cooperation of more than 15 research institutes from all over the world The MATROSHKA experiments represent therefore the currently biggest international

Reitz, G.; Berger, T.

223

Evaluation of the peripheral dose to uterus in breast carcinoma radiotherapy.  

PubMed

The absorbed dose outside of the direct fields of radiotherapy treatment (or peripheral dose, PD) is responsible for radiation exposure of the fetus in pregnant women. Because the radiological protection of the unborn child is of particular concern in the early period of the pregnancy, the aim of this study is to estimate the PD in order to assess the absorbed dose in the uterus in a pregnant patient irradiated for breast carcinoma therapy. The treatment was simulated on an Alderson-Rando anthropomorphic phantom, and the radiation dose to the fetus was measured using an ionisation chamber and thermoluminescence dosemeters. Two similar treatments plans with and without wedges were delivered, using a 6 MV photon beam with two isocentric opposite tangential fields with a total dose of 50 Gy, in accordance with common established procedures. Average field parameters for more than 300 patients were studied. Measurements showed the fetal dose to be slightly lower than 50 mGy, a level at which the risk to the fetus is uncertain, although several authors consider this value as the dose threshold for deterministic effects. The planning system (PS) underestimated PD values and no significant influence was found with the use of wedge filters. PMID:12382793

Martín Rincón, C; Jerez Sainz, I; Modolell Farré, I; España López, M L; López Franco, P; Muñiz, J L; Romero, A M; Rodríguez, R

2002-01-01

224

Computation of cross sections and dose conversion factors for criticality accident dosimetry.  

PubMed

In the application of criticality accident dosemeters the cross sections and fluence-to-dose conversion factors have to be computed. The cross section and fluence-to-dose conversion factor for the thermal and epi-thermal contributions to neutron dose are well documented; for higher energy regions (>100 keV) these depend on the spectrum assumed. Fluence is determined using threshold detectors. The cross sections require the folding of an expected spectrum with the reaction cross sections. The fluence-to-dose conversion factors also require a similar computation. The true and effective thresholds are used to include the information on the expected spectrum. The spectra can either be taken from compendia or measured at the facility at which the exposures are to be expected. The cross sections can be taken from data computations or analytic representations and the fluence-to-dose conversion factors are determined by various standards making bodies. The problem remaining is the method of computation. The purpose of this paper is to compare two methods for computing these factors: analytic and Monte Carlo. PMID:15353697

Devine, R T

2004-01-01

225

Dosimetry of BNCT beams with novel thermoluminescent detectors.  

PubMed

In the dosimetry of boron neutron capture therapy (BNCT) beams, thermoluminescent (TL) detectors are typically applied in phantom measurements to determine the spatial distribution of the gamma ray and neutron dose. Pairs of 6LiF and 7LiF are applied to discriminate between the thermal neutron and gamma ray field components, exploiting the high cross section for (n,alpha) reaction of 6Li. At the Institute of Nuclear Physics (INP) in Kraków (Poland) a prototype TL-based measuring set has been constructed and tested. This set consists of a miniature TL detector (of 2 mm diameter and 0.4 mm thickness) placed inside a miniature container made of non-thermoluminescent 6LiF. The outer dimensions of the set are 4.5 mm diameter and 1.4 mm thickness, enabling its application in place of a thermoluminescence dosemeter pellet in typical phantoms. The detector sets were tested in the BNCT beam of the Studsvik reactor. By exploiting the ratio of TL signals of the unshielded and shielded detectors, it was possible to estimate the contributions of the thermal and epithermal components of the neutron field. PMID:15353719

Bilski, P; Budzanowski, M; Ochab, E; Olko, P; Czopyk, ?

2004-01-01

226

Radioactivity concentrations and dose assessment for soil samples around nuclear power plant IV in Taiwan.  

PubMed

Activity concentrations and distributions of natural and man-made radionuclides in soil samples collected around nuclear power plant IV, Taiwan, were investigated for five years to assess the environmental radioactivity and characterisation of radiological hazard prior to commercial operation. The activity concentrations of radionuclides were determined via gamma-ray spectrometry using an HPGe detector. Data obtained show that the average concentrations of the (238)U and (232)Th series, and (40)K, were within world median ranges in the UNSCEAR report. The (137)Cs ranged from 2.46 +/- 0.55 to 12.13 +/- 1.31 Bq kg(-1). The terrestrial absorbed dose rate estimated by soil activity and directly measured with a thermoluminescence dosemeter (excluding cosmic rays), and the annual effective doses, were 45.63, 57.34 nGy h(-1) and 57.19 microSv, respectively. Experimental results were compared with international recommended values. Since the soil in this area is an important building material, the mean radium equivalent activity, external and inhalation hazard indices and the representative level index using various models given in the literature for the study area were 98.18 Bq kg(-1), 0.27, 0.34 and 0.73, respectively, which were below the recommended limits. Analytical results demonstrate that no radiological anomaly exists. The baseline data will prove useful and important in estimating the collective dose near the new nuclear power plant under construction in Taiwan. PMID:18714131

Tsai, Tsuey-Lin; Lin, Chun-Chih; Wang, Tzu-Wen; Chu, Tieh-Chi

2008-08-20

227

Extremity exposure in nuclear medicine: preliminary results of a European study.  

PubMed

The Work Package 4 of the ORAMED project, a collaborative project (2008-11) supported by the European Commission within its seventh Framework Programme, is concerned with the optimisation of the extremity dosimetry of medical staff in nuclear medicine. To evaluate the extremity doses and dose distributions across the hands of medical staff working in nuclear medicine departments, an extensive measurement programme has been started in 32 nuclear medicine departments in Europe. This was done using a standard protocol recording all relevant information for radiation exposure, i.e. radiation protection devices and tools. This study shows the preliminary results obtained for this measurement campaign. For diagnostic purposes, the two most-used radionuclides were considered: (99m)Tc and (18)F. For therapeutic treatments, Zevalin(®) and DOTATOC (both labelled with (90)Y) were chosen. Large variations of doses were observed across the hands depending on different parameters. Furthermore, this study highlights the importance of the positioning of the extremity dosemeter for a correct estimate of the maximum skin doses. PMID:21233097

Sans Merce, M; Ruiz, N; Barth, I; Carnicer, A; Donadille, L; Ferrari, P; Fulop, M; Ginjaume, M; Gualdrini, G; Krim, S; Mariotti, F; Ortega, X; Rimpler, A; Vanhavere, F; Baechler, S

2011-01-12

228

LET and dose dependence of TLD-100 glow curve after exposure to intermediate-energy ions.  

PubMed

We present results from measurements performed with low fluences (10(5)-10(6) cm(-2)) of 15, 25 and 40 MeV u(-1) carbon, 25 MeV u(-1) oxygen and 40 MeV u(-1) neon ions incident on TLD-100 chips. Dosemeters were arranged individually or in stacks in front of the beam, allowing the study of various linear energy transfer (LET) values simultaneously. The thermoluminescence (TL) total signal is observed to be a linear function of deposited energy. To assess the contribution to the glow curve from the high-temperature peaks, two methods were studied: ratios of peak heights (peak 7 with respect to peak 5), and ratios of areas of the deconvoluted high-temperature peaks with respect to peak 5. The ratios were evaluated as a function of dose, showing in both methods a dependence on LET and ion identity. Some of the studied ions show these ratios to be independent of dose, up to 500 mGy, while for other ions, departures from linearity up to 4.5% +/- 2.5% per 100 mGy are observed at 500 mGy. These results show that, in general, the incident radiation LET is not a parameter that can be deduced from the glow curve. PMID:16565204

Massillon-Jl, G; Gamboa-deBuen, I; Brandan, M E

2006-03-24

229

Strict X-ray beam collimation for facial bones examination can increase lens exposure  

PubMed Central

Objectives It is well accepted that collimation is a cost-effective dose-reducing tool for X-ray examinations. This phantom-based study investigated the impact of X-ray beam collimation on radiation dose to the lenses of the eyes and thyroid along with the effect on image quality in facial bone radiography. Methods A three-view series (occipitomental, occipitomental 30 and lateral) was investigated, and radiation doses to the lenses and thyroid were measured using an Unfors dosemeter. Images were assessed by six experienced observers using a visual grading analysis and a total of 5400 observations were made. Results Strict collimation significantly (p<0.0001) reduced the radiation dose to the lenses of the eyes and thyroid when using a fixed projection-specific exposure. With a variable exposure technique (fixed exit dose, to simulate the behaviour of an automatic exposure control), while strict collimation was again shown to reduce thyroid dose, higher lens doses were demonstrated when compared with larger fields of exposure. Image quality was found to significantly improve using strict collimation, with observer preference being demonstrated using visual grading characteristic curves. Conclusion The complexities of optimising radiographic techniques have been shown and the data presented emphasise the importance of examining dose-reducing strategies in a comprehensive way.

Powys, R; Robinson, J; Kench, P L; Ryan, J; Brennan, P C

2012-01-01

230

Synthesis and characterisation of BaSo4:Eu thermoluminescence phosphor.  

PubMed

Polycrystalline powder samples of BaSO(4) doped with Eu(2+) were prepared by solid-state reaction in different reducing atmospheres. Photoluminescence (PL), thermoluminescence (TL), TL kinetic and dosimetric studies have been carried out in this phosphor. The TL glow curve of BaSO(4):Eu(2+) showed only a single peak at 513 K unlike other phosphors and the TL intensity is about three to four times higher than that of CaSO(4):Dy, which is currently used as the radiation dosemeter for personnel monitoring in India. The TL dose response of the phosphor was found to be linear up to the dose range of 10(3) Gy beyond which saturation sets in. PL and TL spectra showed the characteristic emission of Eu(2+) ion. The TL parameters such as trap depth (E) or the energy required to release the electron or hole from the trap, frequency factor (s) and the order of kinetics (b) are determined by different methods such as isothermal decay, initial rise and variable heating rate. PMID:22223718

Annalakshmi, O; Jose, M T; Madhusoodanan, U

2012-01-05

231

A preliminary comparison of total skin electron treatment techniques to demonstrate the application of a mid-torso phantom for measurement of dose penetration  

PubMed Central

Objectives In the UK, the treatment of patients with mycosis fungoides using total skin electron (TSE) beam therapy is undertaken using a number of different irradiation techniques. As part of a review of these techniques, a comparative set of measurements would be useful to determine how the techniques differ in terms of dose distribution. A dose penetration intercomparison method that could be used as part of such a study is presented here. Methods The dose penetrations for six treatment techniques currently or recently used in four centres in the UK were measured. The variation of dose with skin depth was measured in a WT1 solid water mid-torso phantom. The phantom is portable and suitable to be used in all the techniques. It is designed to hold four small radiochromic film dosemeters to investigate the variation in dose around the mid-torso. For each treatment technique, the phantom was irradiated using the clinical set-up. Results The phantom performed well and was able to measure dose penetration and the uniformity of penetration for several treatment techniques. Conclusion These preliminary results demonstrate that there is some variation in dose distribution between different TSE treatment techniques and that the phantom could be used in a more comprehensive intercomparison. The results are not intended to demonstrate comprehensively the range of penetration that can be achieved in clinical practice as, for one of the treatment techniques, the penetration is customised for the extent of the disease.

Baugh, G; Al-Alawi, T; Fletcher, C L; Mills, J A; Grieve, R J

2011-01-01

232

Neutron measurements in a Varian 2,100C LINAC facility using a Bonner sphere system based on passive gold activation detectors.  

PubMed

The use of high-energy linear electron accelerators (LINACs) for medical cancer treatments is widespread on an international scale. The associated bremsstrahlung X rays may produce neutrons as a result of subsequent photonuclear reactions with the different materials constituting the accelerator head. The generated neutron field is highly variable and depends strongly on the beam energy, on the accelerator shielding, on the flattering filter as well as on the movable collimators (jaws) design and on the irradiation field geometry. An estimate of this photoneutron component is, thus, of practical interest to quantify the radiological risk for the working staff and patients. Due to high frequency electromagnetic fields, and also to the presence of abundant leaked and scattered photons in these installations, measurements of the corresponding neutron fields by active dosemeters are extremely difficult. A modified version of the Bonner sphere system, based on passive gold activation detectors, has been used to perform neutron measurements at two points in a Varian 2,100C LINAC facility. A home-made unfolding procedure (CDM) has been utilised to determine the neutron spectra present at the measurement points. Results indicate that the giant dipole resonance process is the most adequate model to explain neutron production in the LINAC and that a thermal component is present at the measurement points. PMID:17525060

Fernández, F; Domingo, C; Amgarou, K; Castelo, J; Bouassoule, T; Garcia, M J; Luguera, E

2007-05-24

233

Radiation dose reduction to the critical organ with bismuth shielding during endovascular coil embolisation for cerebral aneurysms.  

PubMed

This study evaluated certified dose reduction with bismuth shielding during an endovascular coiling procedure for cerebral aneurysms using a thermoluminescent dosemeter-100 H. A total of 60 patients were enrolled in the study and randomised into two groups (shielding group and unshielded group). In the unshielded group, the total dose-area product was 286.46 Gy cm(2), the fluoroscopy time was 61.57 min and the procedure time was 96.57 min. In the shielding group, those values were 256.36 Gy cm(2), 51.10 min and 91.00 min, respectively. The reductions in the organ-equivalent doses in the right eye, left eye and thyroid were 32.9 % (11.43 mSv), 28.9 % (17.58 mSv) and 68.1 % (20.48 mSv), respectively. The reductions in the relative organ doses were 21.6, 20.8, and 64.4 %, respectively. Bi shielding was feasible and effective for dose reduction during this neurointerventional procedure. PMID:23531557

Han, Su Chul; Kwon, Soon Chan

2013-03-26

234

Influence of background exposure on detection and determination limits for a TL dosimetry system based on LiF:Mg,Cu,P(GR-200A).  

PubMed

Thermoluminescence dosemeters are widely used to monitor personal doses. For these low dose range applications, it is important to determine the detection limit L(D) and the determination limit L(Q) of the dosimetric system. The influence of background exposure on these limits for LiF:Mg,Cu,P(GR-200A) based TL dosimetry was investigated. Both the conventional analysis and the glow curve analysis methods were used to determinate these limits. The detection limit L(D) was compared with the recording level and the investigation level. A systematic error can occur in the occupational dose evaluation when the detection limit L(D) is more than the recording level. It was found that the L(D) of the dosimetric system-based LiF:Mg,Cu,P(GR-200A) was less than the recording level for exposure time tau > or = 10 days considering an annual dose limit of 1 mSv for the public recommended in ICRP Publication 60. PMID:12382732

Tang, K Y; Liu, B X; Zhu, H Y; Wang, Y C; Shen, W X

2002-01-01

235

Determination of ionisation chamber collection efficiency in a swept electron beam by means of thermoluminescent detectors and the "two-voltage" method.  

PubMed

Two methods for determining the collection efficiency of a 0.6 cm3 thimble ionisation chamber exposed to the swept electron beam of a linear accelerator Therac 20 Saturne (CGR MeV) have been compared. In one method the chamber signal has been compared to that of simultaneously exposed thermoluminescent LiF dosemeters (TLD), in the other the "two-voltage" method of Boag, adapted for swept beams, has been used. By variation of the electron energy between 20 and 13 MeV, of the focus-skin-distance (FSD) between 200 and 100 cm and of the monitor rate between 400 monitor units (m.u.) and 100 m.u. per minute, different values could be produced for the peak charge density M. The collection efficiency of the chamber, operating at a standard voltage of 250 V, decreases from 0.99 to 0.84 for a charge density increasing from 0.3 X 10(-4) C/m3 to 7.5 X 10(-4) C/m3, respectively. The maximum deviation observed between the TLD and the "two-voltage" method adopted for similar M is never more than 2% and mostly smaller than 1%. It can be concluded that, under the present experimental conditions, the calculated ionisation chamber collection efficiency is confirmed by the experimental method using TL dosimetry. PMID:3925506

Van Dam, J; Rijnders, A; Ang, K K; Mellaerts, M; Grobet, P

1985-06-01

236

Personal dose equivalent conversion coefficients for electrons to 1 Ge V.  

PubMed

In a previous paper, conversion coefficients for the personal dose equivalent, H(p)(d), for photons were reported. This note reports values for electrons calculated using similar techniques. The personal dose equivalent is the quantity used to approximate the protection quantity effective dose when performing personal dosemeter calibrations and in practice the personal dose equivalent is determined using a 30×30×15 cm slab-type phantom. Conversion coefficients to 1 GeV have been calculated for H(p)(10), H(p)(3) and H(p)(0.07) in the recommended slab phantom. Although the conversion coefficients were determined for discrete incident energies, analytical fits of the conversion coefficients over the energy range are provided using a similar formulation as in the photon results previously reported. The conversion coefficients for the personal dose equivalent are compared with the appropriate protection quantity, calculated according to the recommendations of the latest International Commission on Radiological Protection guidance. Effects of eyewear on H(p)(3) are also discussed. PMID:21715410

Veinot, K G; Hertel, N E

2011-06-29

237

Observation of Radiation Environment on ISS during Solar Particle Event in March 2012  

NASA Astrophysics Data System (ADS)

The Liulin-5 charged particle telescope observes the radiation conditions in the spherical tissue-equivalent phantom of MATROSHKA-R international project on the International Space Station (ISS) since June 2007. In this paper attention is drawn to the results from measurements of the radiation parameters during the Solar Particle Event (SPE) occurred 7-8.03.2012. During that SPE the solar particles penetrated the ISS orbit at high geographic latitudes in the regions of the south and north Earth magnetic poles and at 3< L they caused particle flux and dose rates increase in all three detectors of Liulin-5, located at 40, 60 and 165 mm depths along the phantom's radius. The maximum flux at 40 mm depth observed outside the inner radiation belt in the region of South Atlantic Anomaly (SAA) during that SPE reached 7.2 part/cm2.s and the dose rate reached 107.8 µGy/hour. The total dose outside SAA received during the SPE was 259.9 µGy. Compared are the dose rates, particle fluxes, deposited energy spectra, linear energy transfer spectra, obtained radiation quality factors and dose equivalent values during the SPE and during quite conditions. Compared are data from Liulin-5 charged particle telescope and from other particle and radiation detectors in space during that SPE. Compared are the results from radiation measurements on ISS during SPE of March 2012 and data from SPE radiation environment investigations on Mir manned space station in 1989-1993 time periods, conducted with Liulin type dosemeters.

Semkova, Jordanka; Dachev, Tsvetan; Koleva, Rositza; Maltchev, Stephan; Bankov, Nikolay; Benghin, Victor; Shurshakov, Vyacheslav; Petrov, Vladislav; Drobyshev, Sergey

2013-04-01

238

Organ doses from prostate radiotherapy and associated concomitant exposures.  

PubMed

In addition to the therapeutic exposure, a course of radiotherapy will involve the additional (concomitant) irradiation of the patient using CT, simulator or portal imaging systems, for localization of the target volume and subsequent verification of treatment delivery. The number of concomitant exposures is likely to increase as the developing technical capabilities for conformal, image-guided radiotherapy make target and critical organ definition an increasingly important aspect of radiotherapy. Estimation of doses and risks to critical organs in the body from all sources is thus necessary to provide the basis for adequate justification of the exposures as required by ICRP. In this paper, doses to selected organs and tissues for which ICRP have identified fatal cancer probabilities have been measured using a realistic anthropomorphic phantom loaded with thermoluminescent dosemeters and irradiated using a treatment protocol for radical radiotherapy of the prostate. Independently, doses to the same organs and tissues have been measured from concomitant CT and portal imaging exposures given for localization and verification purposes. Although negligible in comparison with the target dose, realistic numbers of concomitant exposures give a small but significant contribution to the total dose to most organs and tissues outside the target volume. Generally, this is in the range 5-10% of the total organ dose, but can be as high as 20% for bone surfaces. These data may be used to estimate concomitant doses from any combination of CT and portal imaging and may help in the justification process, especially when additional verification exposures may be required during treatment. PMID:16714751

Harrison, R M; Wilkinson, M; Shemilt, A; Rawlings, D J; Moore, M; Lecomber, A R

2006-06-01

239

Replacement tissue-equivalent proportional counter for the International Space Station.  

PubMed

The tissue-equivalent proportional counter (TEPC)-based dosemeters used on the International Space Station have exceeded their planned useful lives, and are scheduled to be replaced with the new units taking advantage of improved technology. The original TEPC detectors used cylindrical geometry with field tubes to achieve good energy resolution and minimum sensitivity to noise created by vibration. The inside diameter of these detectors is 5.1 cm. The new detectors developed for this application produce the resolution and vibration resistance of the cylindrical detector with the isotropic response and compact size of a spherical detector. The cathode structure consists of conductive tissue-equivalent plastic A-150 layers separated by thin polyethylene layers perpendicular to the anode. Each conductive layer is held at the electrical potential needed to produce uniform electric field strength along the anode wire, and thus the same gas gain for electrons produced in different portions of the spherical volume. The new design contains the whole preamplifier inside the vacuum chamber to reduce electronic noise. Also the vacuum chamber has a novel design with a 0.020-inch-thick aluminium wall to allow a total wall thickness of 0.5 g cm(-2), which is typical of the shielding provided by a space suit. This feature will allow measuring the dose on the astronauts' skin due to low-energy electrons and protons produced during solar events. The vacuum chamber has a new bayonet clamping system that reduces the total detector weight to less than half that of the old TEPC. PMID:21115447

Perez-Nunez, D; Braby, L A

2010-11-28

240

Measurements of long-term external and internal radiation exposure of inhabitants of some villages of the Bryansk region of Russia after the Chernobyl accident.  

PubMed

A Nordic-Soviet programme was initiated in 1990 to evaluate the external and internal radiation exposure of the inhabitants of several villages in the Bryansk region of Russia. This area was one of the number of areas particularly affected by the nuclear accident at the Chernobyl Nuclear Power Plant in 1986. Measurements were carried out yearly until 1998 and after that more irregularly; in 2000, 2006 and 2008 respectively. The effective dose estimates were based on individual thermoluminescent dosemeters and on in vivo measurements of the whole body content of (137)Cs (and (134)Cs during the first years of the programme). The decrease in total effective dose during the almost 2 decade follow-up was due to a continuous decrease in the dominating external exposure and a less decreasing but highly variable exposure from internal irradiation. In 2008, the observed average effective dose (i.e. the sum of external and internal exposure) from Chernobyl (137)Cs to the residents was estimated to be 0.3mSv y(-1). This corresponds to 8% of the estimated annual dose in 1990 and to 1% of the estimated annual dose in 1986. As a mean for the population group and for the period of the present study (2006-2008), the average yearly effective dose from Chernobyl cesium was comparable to the absorbed dose obtained annually from external exposure to cosmic radiation plus internal exposure to naturally occurring radionuclides in the human body. Our data indicate that the effective dose from internal exposure is becoming increasingly important as the body burdens of Chernobyl (137)Cs are decreasing more slowly than the external exposure. However, over the years there have been large individual variations in both the external and internal effective doses, as well as differences between the villages investigated. These variations and differences are presented and discussed in this paper. PMID:21906781

Bernhardsson, C; Zvonova, I; Rääf, C; Mattsson, S

2011-09-08

241

Validation of a Monte Carlo simulation for dose assessment in dental cone beam CT examinations.  

PubMed

A Monte Carlo (MC) simulation for calculating absorbed dose has been developed and applied for dental applications with an i-CAT cone beam CT (CBCT) system. To validate the method a comparison was made between calculated and measured dose values for two different clinical protocols. Measurements with a pencil CT chamber were performed free-in-air and in a CT dose head phantom; measurements were also performed with a transmission ionization chamber. In addition for each protocol a total number of 58 thermoluminescence dosemeters (TLD) were packed in groups and placed at 16 representative anatomical locations of an anthropomorphic phantom (Remab system) to assess absorbed doses. To simulate X-ray exposure, a software application based on the EGS4 package was applied. Dose quantities were calculated for different voxelized models representing the CT ionization and transmission chambers, the TLDs, and the phantoms as well. The dose quantities evaluated in the comparison were the accumulated dose averaged along the rotation axis (D(i)), the volume average dose,D(vol) for the dosimetric phantom, the dose area product (DAP) and the absorbed dose for the TLDs. Absolute differences between measured and simulated outcomes were ? 2.1% for free-in-air doses; ? 6.2% in the 5 cavities of the CT dose head phantom; ? 13% for TLDs inside the primary beam. Such differences were considered acceptable in all cases and confirmed the validity of the MC program for different geometries. In conclusion, the devised MC simulation program can be a robust tool to optimize protocols and estimate patient doses for CBCT units in dental, oral and maxillofacial radiology. PMID:21807542

Morant, J J; Salvadó, M; Casanovas, R; Hernández-Girón, I; Velasco, E; Calzado, A

2011-07-31

242

Techniques for measurement of dose width product in panoramic dental radiography.  

PubMed

Dose width product (DWP) is the quantity recommended for assessment of patient dose for panoramic dental radiography. It is the product of the absorbed dose in air in the X-ray beam integrated over an exposure cycle and the width of the beam, both measured at the receiving slit. A robust method for measuring the DWP is required in order to facilitate optimization of practices and enable comparison of dose levels at different centres. In this study, three techniques for measuring the DWP have been evaluated through comparison of results from 20 orthopantomographic units. These used a small in-beam semiconductor detector and X-ray film, a pencil ionization chamber and an array of thermoluminescent dosemeters (TLDs). The mean results obtained with the three techniques agreed within +/-6%. The technique employing a pencil ionization chamber of the type used for dose assessment of CT scanners is the simplest and most reliable method. The in-beam detector and film method has larger errors both from positioning the radiation detector and from measurement of X-ray beam width, which should be the full width at half maximum obtained from a scan of the film optical density. The TLD array method was accurate, but more time consuming to carry out. The mean DWP for the units studied was 65 mGy mm and the mean dose-area product was 89 mGy cm2. The DWP for 30% of the units tested exceeded the diagnostic reference dose of 65 mGy mm, recommended by the National Radiological Protection Board. PMID:16489195

Doyle, P; Martin, C J; Robertson, J

2006-02-01

243

Occupational radiation doses to the extremities and the eyes in interventional radiology and cardiology procedures  

PubMed Central

Objectives The aim of this study was to determine occupational dose levels in interventional radiology and cardiology procedures. Methods The study covered a sample of 25 procedures and monitored occupational dose for all laboratory personnel. Each individual wore eight thermoluminescent dosemeters next to the eyes, wrists, fingers and legs during each procedure. Radiation protection shields used in each procedure were recorded. Results The highest doses per procedure were recorded for interventionists at the left wrist (average 485 ?Sv, maximum 5239 ?Sv) and left finger (average 324 ?Sv, maximum 2877 ?Sv), whereas lower doses were recorded for the legs (average 124 ?Sv, maximum 1959 ?Sv) and the eyes (average 64 ?Sv, maximum 1129 ?Sv). Doses to the assisting nurses during the intervention were considerably lower; the highest doses were recorded at the wrists (average 26 ?Sv, maximum 41 ?Sv) and legs (average 18 ?Sv, maximum 22 ?Sv), whereas doses to the eyes were minimal (average 4 ?Sv, maximum 16 ?Sv). Occupational doses normalised to kerma area product (KAP) ranged from 11.9 to 117.3 ?Sv/1000 cGy cm2 and KAP was poorly correlated to the interventionists' extremity doses. Conclusion Calculation of the dose burden for interventionists considering the actual number of procedures performed annually revealed that dose limits for the extremities and the lenses of the eyes were not exceeded. However, there are cases in which high doses have been recorded and this can lead to exceeding the dose limits when bad practices are followed and the radiation protection tools are not properly used.

Efstathopoulos, E P; Pantos, I; Andreou, M; Gkatzis, A; Carinou, E; Koukorava, C; Kelekis, N L; Brountzos, E

2011-01-01

244

Guidance on individual monitoring programmes for radioisotopic techniques in molecular and cellular biology.  

PubMed

The radioisotope techniques used in molecular and cellular biology involve external and internal irradiation risk. The personal dosemeter may be a reasonable indicator for external irradiation. However, it is necessary to control the possible internal contamination associated with the development of these techniques. The aim of this project is to analyse the most usual techniques and to establish programmes of internal monitoring for specific radionuclides (32P, 35S, 14C, 3H, 125I and 131I). To elaborate these programmes it was necessary to analyse the radioisotope techniques. Two models have been applied (NRPB and IAEA) to the more significant techniques, according to the physical and chemical nature of the radionuclides, their potential importance in occupational exposure and the possible injury to the genetic material of the cell. The results allowed the identification of the techniques with possible risk of internal contamination. It was necessary to identify groups of workers that require individual monitoring. The risk groups have been established among the professionals exposed, according to different parameters: the general characteristics of receptor, the radionuclides used (the same user can work with one, two or three radionuclides at the same time) and the results of the models applied. Also a control group was established. The study of possible intakes in these groups has been made by urinalysis and whole-body counter. The theoretical results are coherent with the experimental results. They have allowed guidance to individual monitoring to be proposed. Basically, the document shows: (1) the analysis of the radiosotopic techniques, taking into account the special containment equipment; (2) the establishment of the need of individual monitoring; and (3) the required frequency of measurements in a routine programme. PMID:14526986

Macías, M T; Navarro, T; Lavara, A; Robredo, L M; Sierra, I; Lopez, M A

2003-01-01

245

Study on radionuclides in granite quarries of Bangalore rural district, Karnataka, India.  

PubMed

Studies on natural radiation levels and radionuclides were carried out extensively in the environment of granite quarries of Kanakapura, Ramanagara Taluks and Bidadi Hobli in Bangalore rural District and Bangalore city. The indoor and outdoor gamma exposure rate in air was measured using an environmental dosemeter, and it is converted into absorbed dose using suitable conversion factor. The activity concentrations of natural radionuclides in rock samples and also in soil samples were measured using an HPGe gamma-ray spectrometer. The results reveal that the activity concentrations of (226)Ra, (232)Th and (40)K in rocks are found to be vary from 32.2 to 163.6, 128.3 to 548.6 and 757.4 to 1418.4 Bq kg(-1), respectively, with corresponding arithmetic mean values of 93.2, 306.2 and 1074.4 Bq kg(-1). Activity concentrations of (226)Ra, (232)Th and (40)K in soil samples were found to vary from 32.4 to 55.2, 39.9 to 214.3 and 485.4 to 1150.2 Bq kg(-1), respectively, with corresponding arithmetic mean values of 40.7, 93.1 and 750.4 Bq kg(-1). The average activity levels of all these radionuclides are above the global average. This is consistent with the geological and geo-chemical significance of the rocks of the area under investigation. The results of these systematic investigations are discussed in detail and compared with the literature values represented for other environments. PMID:18682406

Ningappa, C; Sannappa, J; Karunakara, N

2008-08-04

246

Irradiation of members of the general public from radioactive caesium following the Chernobyl reactor accident: Field studies in a highly contaminated area in the Bryansk region, Russia  

NASA Astrophysics Data System (ADS)

From 1990 to 1998, estimations of the effective dose due to irradiation from 137Cs and 134Cs were carried out for inhabitants in rural villages in the Bryansk region, Russia. The villages, situated about 180 km from the Chernobyl power plant received deposition of 137Cs in the range 0.9-2.7 MBq m-2 due to the accident in 1986. The body burden of 137,134Cs was estimated from measurements of the urinary concentration of caesium radionuclides, together with in vivo measurements using a portable detector. The external effective dose was estimated from measurements with thermoluminescent (TL)-dosemeters worn by the participants during one month each year. In a case study, the changes in biokinetics of 137Cs during pregnancy was investigated in a woman with an unintended intake of 137Cs via mushrooms grown in the area. During pregnancy the biological half-time of caesium was 54% of that before pregnancy. The ratio of the 137Cs concentration in breast milk (Bq L-1) to that in the mother's body (Bq kg-1) was 15% one month after the child was born. The body burden of 137Cs in the Russian individuals calculated from urine samples showed a good agreement with the body burden estimated from in vivo measurements in the same individuals. Normalisation of the caesium concentration in the urine samples by the use of potassium or creatinine excretion introduced systematic differences and a larger spread in the calculated values of the 137Cs body burden as compared with calculations without normalisation. The yearly effective dose to inhabitants in the Russian villages varied between 1.2 and 2.5 mSv as a mean for all villages between 1991 and 1998 and the internal effective dose was 30-50% of the total effective dose. The external effective dose decreased on average 15% per year, while the internal effective dose varied, depending to a great extent on the availability of mushrooms. The cumulated effective dose for a 70-year period after the accident was calculated to be 100 mSv assuming that the effective dose will decrease by only the physical decay of 137Cs (2% per year) after 1998. Individuals may receive considerably higher effective doses, up to 0.5 Sv during a life-time considering the large spread in dose values among individuals.

Thornberg, Charlotte

247

Mammography dosimetry using an in-house developed polymethyl methacrylate phantom.  

PubMed

Phantom-based measurements in mammography are well-established for quality assurance (QA) and quality control (QC) procedures involving equipment performance and comparisons of X-ray machines. Polymethyl methacrylate (PMMA) is among the best suitable materials for simulation of the breast. For carrying out QA/QC exercises in India, a mammographic PMMA phantom with engraved slots for keeping thermoluminescence dosemeters (TLD) has been developed. The radiation transmission property of the developed phantom was compared with the commercially available phantoms for verifying its suitability for mammography dosimetry. The breast entrance exposure (BEE), mean glandular dose (MGD), percentage depth dose (PDD), percentage surface dose distribution (PSDD), calibration testing of automatic exposure control (AEC) and density control function of a mammography machine were measured using this phantom. MGD was derived from the measured BEE following two different methodologies and the results were compared. The PDD and PSDD measurements were carried out using LiF: Mg, Cu, P chips. The in-house phantom was found comparable with the commercially available phantoms. The difference in the MGD values derived using two different methods were found in the range of 17.5-32.6 %. Measured depth ranges in the phantom lie between 0.32 and 0.40 cm for 75 % depth dose, 0.73 and 0.92 cm for 50 % depth dose, and 1.54 and 1.78 cm for 25 % depth dose. Higher PSDD value was observed towards chest wall edge side of the phantom, which is due to the orientation of cathode-anode axis along the chest wall to the nipple direction. Results obtained for AEC configuration testing shows that the observed mean optical density (O.D) of the phantom image was 1.59 and O.D difference for every successive increase in thickness of the phantom was within±0.15 O.D. Under density control function testing, at -2 and -1 density settings, the variation in film image O.D was within±0.15 O.D of the normal density setting '0' and at +2 and +1 density setting, it was observed to be within±0.30 O.D. This study indicates that the locally made PMMA TLD slot phantom can be used to measure various mammography QC parameters which are essentially required for better outcomes in mammography. PMID:22232773

Sharma, Reena; Sharma, Sunil Dutt; Mayya, Y S; Chourasiya, G

2012-01-09

248

Evaluation of factors to convert absorbed dose calibrations from graphite to water for the NPL high-energy photon calibration service  

NASA Astrophysics Data System (ADS)

The National Physical Laboratory (NPL) provides a high-energy photon calibration service using 4-19 MV x-rays and 60Co ?-radiation for secondary standard dosemeters in terms of absorbed dose to water. The primary standard used for this service is a graphite calorimeter and so absorbed dose calibrations must be converted from graphite to water. The conversion factors currently in use were determined prior to the launch of this service in 1988. Since then, it has been found that the differences in inherent filtration between the NPL LINAC and typical clinical machines are large enough to affect absorbed dose calibrations and, since 1992, calibrations have been performed in heavily filtered qualities. The conversion factors for heavily filtered qualities were determined by interpolation and extrapolation of lightly filtered results as a function of tissue phantom ratio 20,10 (TPR20,10). This paper aims to evaluate these factors for all mega-voltage photon energies provided by the NPL LINAC for both lightly and heavily filtered qualities and for 60Co ?-radiation in two ways. The first method involves the use of the photon fluence-scaling theorem. This states that if two blocks of different material are irradiated by the same photon beam, and if all dimensions are scaled in the inverse ratio of the electron densities of the two media, then, assuming that all photon interactions occur by Compton scatter the photon attenuation and scatter factors at corresponding scaled points of measurement in the phantom will be identical. The second method involves making in-phantom measurements of chamber response at a constant target-chamber distance. Monte Carlo techniques are then used to determine the corresponding dose to the medium in order to determine the chamber calibration factor directly. Values of the ratio of absorbed dose calibration factors in water and in graphite determined in these two ways agree with each other to within 0.2% (1? uncertainty). The best fit to both sets of results agrees with values determined in previous work to within 0.3% (1? uncertainty). It is found that the conversion factor is not sensitive to beam filtration.

Nutbrown, R. F.; Duane, S.; Shipley, D. R.; Thomas, R. A. S.

2002-02-01