Comparison of Natural Background Dose Rates for Residents of the Amargosa Valley, Nv, to Those in Leadville, Co, and the States of Colorado and Nevada

Abstract

-In the latter half of 2005, the U.S. Environmental Protection Agency (USEPA) published a Proposed Rule (40 CFR Part 197) for establishing a dose rate standard for limiting radionuclide releases from the proposed Yucca Mountain high-level radioactive waste repository during the time period from lo4 to lo6 years after closure. The proposed standard was based on the difference in the estimated total dose rate from natural background in the Amargosa Valley and the "average annual background radiation" for the State of Colorado. As defined by the USEPA, ''natural background radiation consists of external exposures from cosmic and terrestrial sources, and internal exposures from indoor exposures to naturallyoccurring radon." On the basis of its assessments, the USEPA estimated that the difference in the dose rate in the two identified areas was 3.5 mSv y-l. The purpose of this review was to provide an independent evaluation and review of this estimate. One of the first observations was that, because site-specific dose rate measurements for the Amargosa Valley "were not available," the dose rates for various sources of natural background in that area, used by the USEPA in its assessment, were based on modifications of the average values for the State of Nevada. A second observation was that the conversion factor applied in estimating the dose rates due to exposures to indoor radon and its decay products was a factor of 2 higher than the currently accepted value. Further review revealed that site-specific data for many natural background sources in the Amargosa Valley were available. One particularly important observation was that about 91% of the residents of that area live in mobile homes which, due to their construction and design, have indoor radon concentrations comparable to, or less than, those outdoors. For that reason, alone, the USEPA estimate of the average dose rate for residents of the Amargosa Valley, due to indoor radon, was not valid. For purposes of the comparisons in this paper, site-specific dose rates were estimated for all major natural background sources of exposure to residents of the Amargosa Valley, and those in Leadville, CO. The latter community was selected for comparison because of its altitude (3,200 m) and accompanying high cosmic radiation dose rate, and the fact the size of its population is comparable to that of Amargosa Valley. For completeness, similar comparisons of the estimated dose rate in the Amargosa Valley to those for residents of Leadville, CO, the States of Colorado and Nevada. The estimated dose rates in Leadville, the State of Colorado, and the State of Nevada, were higher than those in the Amargosa Valley by 4.09,2.62, and 1.01 mSv y-', respectively. Associated uncertainties were 1 highest for the estimated dose rates due to exposures to radon and its decay products. The overall uncertainty in the dose estimates, including the errors in the radon dose coefficient, could be as high as 142%.

ICRP Publication 130: Occupational Intakes of Radionuclides: Part 1

“…Sampling protocols can be designed to minimise the sampling uncertainty, as shown by Sun et al. (1993) for plutonium urinalysis and Moeller and Sun (2006) for indoor radon exposure. In-vivo measurements can be performed in different geometries (whole-body measurements, and organ- or site-specific measurements such as measurements over the lung, thyroid, skull, liver, or a wound). Each type of geometry needs specialised detector systems and calibration methods.…”

“…Sampling protocols can be designed to minimise the sampling uncertainty, as shown by Sun et al. (1993) for plutonium urinalysis and Moeller and Sun (2006) for indoor radon exposure.…”

“…This introduces additional sources of Type B uncertainty relating to biological (inter-and intrasubject) variability and sampling procedures, which may well be greater than the uncertainty in the measured sample activity. Sampling protocols can be designed to minimise the sampling uncertainty, as shown by Sun et al (1993) for plutonium urinalysis and Moeller and Sun (2006) for indoor radon exposure.…”

Lauriston S. Taylor Lecture: Yucca Mountain Radiation Standards, Dose/Risk Assessments, Thinking Outside the Box, Evaluations, and Recommendations

“…In a subsequent Proposed Rule, U.S. NRC (2005) concurred with the U.S. EPA recommendations, and specifically stated that it supports the use of the "recommendations and guidance from ICRP Publications 60 through 72" as well as "the use of current dosimetry." Facilitating compliance with this guidance is the fact that the recommendations in ICRP Publications 60 through 72 have been incorporated into Federal Guidance Report (FGR) No.…”

Radionuclide contents and physico-chemical characterization of solid waste and effluent samples of some selected industries in the city of Lagos, Nigeria

“…Using equation (5) and the average absorbed dose rate of 94 nGy h -1 and taken into account the fact that the average person spends 20% of his/her time outdoors (UNSCEAR, 2000;Moeller and Sun, 2006), the average outdoor effective dose rate due to gamma exposure from these waste materials in the city would be 0.12 mSv y -1 . This value is less than the recommended limit of 1 mSv y -1 for the members of the public (UNSCEAR, 2000; Abbadey and El-Arabi, 2006).…”