[en] The Human Monitoring Laboratory's portable whole body counter has been calibrated using Monte Carlo simulations. The validity of the calibrations was checked by measuring a 95-percentile man phantom distributed by the International Atomic Energy Agency as part of an international In Vivo intercomparison exercise. The agreement between the predicted activity of 137Cs and 60Co and the amounts that were measured in the Human Monitoring Laboratory's fixed whole body counter was 4%. A function was also found that related counting efficiency to photon energy and size of the phantom (or person) being measured. The accuracy of this function was in the range of 8% to -9%. Finally, some retrospective design was performed using a combination of Monte Carlo simulations and measured background data to show that the optimum configuration for the portable whole body counter would have been two detectors that were 9.2 cm in diameter and 12.7 cm thick instead of the current configuration: upper detector, 7.6 cm in diameter and 7.6 cm thick; lower detector, 9.2 cm in diameter and 12.7 cm thick. The modified portable whole body counter would have a minimum detectable activity that was lower than the original design by 13% - 23%, in the range 126 keV to 2,754 keV, for the Reference Male phantom. (Author) 11 refs

[en] A study of an aboriginal community was conducted to determine if kidney function had been affected by the chronic ingestion of uranium in drinking water from drilled wells whose uranium concentrations varied from <1 to 1,418 ppb. This non-invasive study relied on the measurement of a combination of indicators of kidney function and markers for cell toxicity measured in urine samples collected from 39 females and 15 males. Ages ranged from 12 to 73 years. Correlation of uranium excreted in urine with bio-indicators at p≤0.05 indicates interference with the kidney's reabsorptive function. Because of the community's concerns regarding cancer incidence, cumulative radiaiton doses were also calculated using uranium intake in drinking water over the preceding 15-year period. the average dose was 0.2 mSv and the highest dose, 1.7 mSv with the risk of cancer from the former being 1.4 in 100,000 while that from the latter in 12 in 100,000. Both would be difficult to detect in the community studied (population: 1,480). (Author) 28 refs

[en] Three sizes of the St Petersburg phantom have been compared to six sizes of BOMAB phantoms measured by a virtual whole-body counter similar to the one in use in the Human Monitoring Laboratory using Monte Carlo simulations. The previously published data comparing the St Petersburg Reference Man sized phantom with a similar sized Bottle Manikin Absorber Phantoms (BOMAB) phantom at 662 keV is supported; however, the simulations also show that the smaller sized St Petersburg phantoms do not agree well with smaller BOMAB phantoms. It is concluded that the St Petersburg phantoms are system dependent meaning that all sizes of the St Petersburg phantoms should be experimentally compared over a wide photon energy range against corresponding BOMAB phantoms to validate their use for calibrating whole-body counters. (authors)

[en] The sliced Bottle Manikin Absorber (BOMAB) phantom was originally proposed as an alternative to a commercially available phantom, but it suffers from the disadvantage of containing over 160 sources that need to be manufactured; however, it was found that the number of slices could be reduced substantially and that two slices in the sliced phantom gave the same performance characteristics over a wide energy range as a conventional BOMAB phantom for a particular counting system. This work explores the adaptability of this phantom to another counting geometry. The response of the Human Monitoring Laboratory's whole-body counter measuring this phantom with a decreasing number of planar sources has been modelled using MCNP5 over a wide energy range (122-2754 keV). It was found that the best agreement was obtained when the phantom contained 10 sources, 1 in the mid point of each section. As this is a different result from a previous finding, any other counting geometry will have to be assessed to determine the optimum loading if the sliced phantom is to be used. Also, it is clear that this type of phantom cannot be used for an intercomparison that will encounter different counting geometries, unless it contains a full loading of sources. (authors)

[en] A new stand has been designed to support the Bottle Manikin Absorber Phantoms when the phantoms are counted in the vertical position in a whole-body counter. The stand previously used by the Human Monitoring Laboratory was constructed from metal and was heavy to transport and making height adjustments to accommodate different phantom sizes was very time consuming. The new stand is constructed from lightweight plastic materials and allows easy height adjustments to accommodate different phantom sizes while supporting the weight of the phantoms. The stand was evaluated inside a whole-body counter at a nuclear-generating station and met all operational requirements for accessibility and ease of use. (authors)

[en] This work is the result of a collaboration between the Working Group WG7 Internal Dosimetry of EURADOS (European Dosimetry Radiation Group, www.eurados.org) which is coordinated by CIEMAT, and the organization USTUR (U.S. transuranium and Uranium Registries) to carry out an international intercomparison in-vivo measurement and simulation using Monte Carlo methods, measurement of Am-241 in the bone of a mannequin leg with germanium detectors.

[en] When measuring the internally deposited activity in the bone of a subject, the placement of the detector is critical. This study reports the simulated counting efficiencies for three counting geometries, the skull, knee and shin, using 13 different voxel phantoms. It shows that the range of counting efficiencies for a given geometry is large for the studied phantoms, especially at low energies. Skull counting offers higher efficiency for low energies such as the 17 keV compared to knee counting or shin counting, but this advantage disappears when the energy is higher such as at 185 keV. This work also shows that the calibration phantom may greatly impact the accuracy of the activity estimate in bone counting, with uncertainties increasing greatly as the photon energy is reduced. Estimating the activity of a radionuclide in bone from direct counting has large uncertainties, and the dose calculated from a skeleton measurement would need careful analysis and, if possible, supporting data from other bioassay measurements. (authors)

[en] The National Internal Radiation Assessment Section (NIRAS), which operates the Canadian National Calibration Reference Centre for Bioassay and In Vivo Monitoring, has field deployable equipment for emergency response. A substantial part of this tool kit is a set of portal monitors that can be used to quickly screen people into the 'uncontaminated' and the 'contaminated'. The former term refers to a person who has <60 kBq (empirical practical detection limit) of activation/fission products and the latter group is contaminated by that amount or more. Recent field work has shown that one type of the NIRAS's portal monitors can be alarmed at significant distances if the level of contamination is high enough. The other types, which do not initiate a count until either an infra-red beam is broken or a proximity detector is activated, do not alarm but their background will be raised and this causes other problems. This paper proposes a method of group monitoring to help speed up the process of screening a large number of potentially contaminated persons using portal monitors. In short, the group of potentially contaminated persons will be kept isolated from the portal stations. Depending on a real-time estimate of the percentage of contaminated persons in the crowd, groups of persons will be selected for screening. The hypergeometric distribution has been used to decide on the sampling group size with an expectation that 90% of the time no contaminated person will be present in the group. Once removed from the main waiting area, the group will be pre-screened and then, depending on the result, sent to the appropriate portal. It is anticipated that this will greatly speed up processing as it substantially reduces the transit time. Transits times have also been estimated in addition to the number of personnel required to run all of NIRAS's field deployable equipment. (authors)

[en] Highlights: • Presentation of an intercomparison exercise on Monte Carlo modelling of anthropomorphic voxel phantoms. • An idealized ground-contamination photon exposure scenario was proposed. • Thirteen participants submitted organ and effective dose rates for comparison against verified reference solutions. • Effective dose rates appeared to agree with the reference value in five of the cases. • In only one of those cases was similar agreement also demonstrated in the evaluation of all requested organ dose rates. • Orders-of-magnitude differences in doses were seen for some of the participants. • The overall observations and conclusions from the exercise are summarized and discussed. An intercomparison exercise is described that examines Monte Carlo modelling of anthropomorphic voxel phantoms in an idealized ground-contamination photon exposure scenario. Thirteen participants calculated and submitted organ and effective dose rates for comparison against a set of verified reference solutions. The effective dose rates are shown to agree with the reference value to within reasonable statistical uncertainties in five of the cases, though in only one of those was similar agreement also demonstrated in the evaluation of all requested organ dose rates. Orders-of-magnitude differences in doses are seen for some of the other participants, both internally within their own dataset and also relative to the reference solutions. Following limited feedback and suggestions from the organizer, up to two sets of revised solutions were resubmitted by some of the participants; these generally exhibited improved agreement, though not always. The overall observations and conclusions from this intercomparison exercise are summarized and discussed.

[en] This study develops and compares different, increasingly detailed anatomical phantoms for rainbow trout (Oncorhynchus mykiss) for the purpose of estimating organ absorbed radiation dose and dose rates from "1"3"1I uptake in multiple organs. The models considered are: a simplistic geometry considering a single organ, a more specific geometry employing additional organs with anatomically relevant size and location, and voxel reconstruction of internal anatomy obtained from CT imaging (referred to as CSUTROUT). Dose Conversion Factors (DCFs) for whole body as well as selected organs of O. mykiss were computed using Monte Carlo modeling, and combined with estimated activity concentrations, to approximate dose rates and ultimately determine cumulative radiation dose (μGy) to selected organs after several half-lives of "1"3"1I. The different computational models provided similar results, especially for source organs (less than 30% difference between estimated doses), and whole body DCFs for each model (∼3 × 10"−"3 μGy d"−"1 per Bq kg"−"1) were comparable to DCFs listed in ICRP 108 for "1"3"1I. The main benefit provided by the computational models developed here is the ability to accurately determine organ dose. A conservative mass-ratio approach may provide reasonable results for sufficiently large organs, but is only applicable to individual source organs. Although CSUTROUT is the more anatomically realistic phantom, it required much more resource dedication to develop and is less flexible than the stylized phantom for similar results. There may be instances where a detailed phantom such as CSUTROUT is appropriate, but generally the stylized phantom appears to be the best choice for an ideal balance between accuracy and resource requirements. - Highlights: • Computational models (phantoms) are developed for rainbow trout internal dosimetry. • Phantoms are combined with empirical models for "1"3"1I uptake to estimate dose. • Voxel and stylized phantoms predict similar organ radiation doses from "1"3"1I uptake. • Direct and indirect approaches to calculating organ dose are compared. • The voxel phantom is more accurate, but requires more resource dedication to develop