Kevin Capello

Uranium in Drinking Water: Renal Effects of Long-Term Ingestion by an Aboriginal Community

ABSTRACT The authors conducted a study of an aboriginal community to determine if kidney func-tion had been affected by the chronic ingestion of uranium in drinking water from the communitys drilled wells. Uranium concentrations in drinking water varied from < 1 to 845 ppb. This nonin-vasive study relied on the measurement of a combination of urinary indicators of kidney function and markers for cell toxicity. In all, 54 individuals (12–73 years old) participated in the study. Correlation of uranium excreted in urine with bio-indicators at p ≤.05 indicated interference with the kidneys reabsorptive function. Because of the communitys concerns regarding cancer incidence, the authors also calculated cumulative radiation doses using uranium intake in drinking water over the preceding 15-year period. The highest total uranium intake over this period was 1,761 mg. The risk of cancer from the highest dose, 2.1 mSv, is 13 in 100,000, which would be difficult to detect in the community studied (population size = 1,480). This study indicates that at the observed levels of uranium intake, chemical toxicity would be a greater health concern than would radiation dose.

Tools for creating and manipulating voxel phantoms.

The National Internal Radiation Assessment Sections Human Monitoring Laboratory (HML) has purchased and developed a number of in-house tools to create and edit voxel phantoms. This paper describes the methodology developed in the HML using those tools to prepare input files for Monte Carlo simulations using voxel phantoms. Three examples are given. The in-house tools described in this paper, and the phantoms that have been created using them, are all publically available upon request from the corresponding author.

The StandFast whole body counter: efficiency as a function of BOMAB phantom size and energy modeled by MCNP5.

The StandFast whole body counter has been modeled using Monte Carlo simulations to examine the effect of phantom size, photon energy, and position of the phantom within the counting enclosure on the counting efficiency. The first geometry, the manufacturer’s recommended positioning, was found to have the higher counting efficiencies and the most dependence on phantom size. The second position, where the phantom is at the back of the counting enclosure, had lower counting efficiencies, and hence higher minimum detectable activities, by a factor of between 1.3 to 2.1 when compared with the first geometry; however, for emergency response where accuracy is to be preferred over sensitivity, this geometry would be the better choice. A unified calibration equation was also developed for the StandFast so that it is possible to predict the counting efficiency as a function of photon energy and size to within 11%.

The HML's new voxel phantoms: two human males, one human female, and two male canines.

Abstract The Human Monitoring Laboratory (HML) has created five new voxel phantoms that can be used for Monte Carlo simulations. Three phantoms were created from computer tomography image sets that were obtained from facilities in Italy and the USA: a human male and the male canines. Two other phantoms were constructed from commercially available software that is used to demonstrate human anatomical features: a human male and a human female. All the voxel phantoms created by the HML that are described in this note are available at no cost to interested researchers.

Sensitivity of portable personnel portal monitors: potential problems when dealing with contaminated persons.

Health physicists are usually concerned with small amounts of radioactivity and strive to develop techniques to measure them; however, following a terrorist attack involving radioactive materials the converse might be the case, and exposed persons may be heavily contaminated. The Human Monitoring Laboratory (HML) has field tested its Portable Personnel Portal (P3) monitors using sources up to 1,700 MBq (47 mCi) to determine the alarm distance as a function of activity. The results show that the P3 monitors are highly sensitive, so much so that siting will be a problem for multiple units if multiple alarms are to be avoided. Building materials will shield the monitors allowing units to be placed closer together than in the open where there is no shielding, but windows and doors reduce shielding and complicate the siting of multiple units. In either situation, careful prior thought should be given to siting the monitors and the logistics of crowd control techniques.

Voxel phantoms: the new ICRP computational phantoms: how do they compare?

AbstractTwo new voxel phantoms, ICRP Adult Female (AF) and ICRP Adult Male (AM), have been compared with BOMAB (BOttle Mannikin ABsorber) phantoms and other voxel phantoms of similar size (NORMAN and VIP-Man) using Monte Carlo simulations to assess their counting efficiencies in a whole body counter. The results show that the ICRP phantoms, compared with NORMAN and VIP-Man, had counting efficiencies that ranged from 3% to 59% higher over the energy range 122 keV to 1,836 keV, a trend that is also exhibited by the comparable BOMAB phantoms. A comparison of all the voxel phantoms’ results to those of the BOMAB phantom corresponding to reference man shows that the NORMAN and VIP-Man have mostly lower counting efficiencies, whereas the ICRP phantoms have higher counting efficiencies than the PM (Phantom Male) BOMAB phantom. This could be due to differences in the internal structure of each of the voxel phantoms. As expected, the ICRP AF (female voxel) had the highest efficiency due to being the smallest of all the phantoms.

Evaluation of a commercial software package's ability to calibrate an in vivo counter for emergency response.

AbstractA commercial detector calibration package has been assessed for its use to calibrate the Human Monitoring Laboratory’s Portable Whole Body Counter that is used for emergency response. The advantage of such a calibration software is that calibrations can be derived very quickly once the model has been designed. The commercial package’s predictions were compared to experimental point source data and to predictions from Monte Carlo simulations. It was found that the software adequately predicted the counting efficiencies of a point source geometry to values derived from Monte Carlo simulations and experimental work. Both the standing and seated counting geometries agreed sufficiently well that the commercial package could be used in the field.

EFFECT OF MASS, AT A FIXED HEIGHT, ON THE COUNTING EFFICIENCY OF A BOMAB PHANTOM IN THREE TYPES OF WHOLE BODY COUNTER MODELED BY MCNP5

Using demographic data, a series of BOMAB phantoms were developed to study the effect of size, at a fixed height, of a BOMAB phantom using Monte Carlo simulations in three different whole body counting systems: the HMLs scanning detector whole body counter, a FastScan whole body counter, and a StandFast whole body counter. The latter has had two counting geometries simulated—one for the recommended position, and another simulating a constant detector-to-front-of-phantom distance. The six phantom sizes corresponded to the following masses: 48 kg, 73 kg, 98 kg, 123 kg, 148 kg, and 173 kg. The effect of size varies with photon energy, as might be expected, and at any given energy is an exponential function of the mass. An equation has been found that fits most cases very well and is still good in poorer cases. Persons lighter in mass than the normal calibration phantom (73 kg) will have their body burdens overestimated by as much as a factor of 1.3, depending on mass, photon energy, and counting geometry. Conversely, heavier individuals will have their body burdens underestimated by as much as a factor of 1.9, depending on mass, photon energy, and counting geometry.

A FIELD DEPLOYABLE HIGH-RESOLUTION URINE GAMMA ANALYZER

The Human Monitoring Laboratory has extended the use of its portable whole body counters to portable gamma spectrometers for urinalysis. The protocol tested measured a 120-mL sample in a polypropylene sample container for 5 min. Minimum detectable activities were estimated for 241Am, 57Co, 137Cs, and 60Co. The former is 113 Bq per sample, and the latter three are between 27–29 Bq per sample. Assuming an intake 5 d before the measurement, and all other parameters as default, the committed effective doses are 517 Sv, 76 &mgr;Sv, 402 &mgr;Sv, and 1.5 mSv, respectively. Clearly, this instrument can be used as a field deployable gamma spectrometer for urinalysis for activation and fission products, but actinides (and other low energy photon emitters) remain problematic.

The LLNL voxel phantom : Comparison with the physical phantom and previous virtual phantoms

The Human Monitoring Laboratory has created a voxel phantom from computer tomography scans of the Lawrence Livermore National Laboratory (LLNL) torso phantom for use in Monte Carlo simulations. The voxel phantom has been compared to the previously developed mathematical phantom using Monte Carlo simulations and both virtual phantoms have been compared to physical measurement of the LLNL phantom. The voxel phantom agreed well with the others, except at very low photon energies (i.e., 17.5 keV), with predicted counting efficiencies being within 2% of the counting efficiencies from the other two phantoms at 59.5 keV and above. The mathematical phantom performs similarly to the voxel phantom, but much faster, so it is an excellent alternative if computer power is lacking. The voxel phantom of the LLNL phantom is available from the authors, on request.