SENSITIVITY ANALYSES OF THE STANDARDS FOR THE PROPOSED YUCCA MOUNTAIN REPOSITORY???A REVIEW, EVALUATION, AND COMMENTARY

The standards and regulations for the proposed Yucca Mountain high level radioactive waste repository, which were developed and promulgated by the U.S. Environmental Protection Agency and the U.S. Nuclear Regulatory Commission, respectively, are complex and challenging. A major reason is that they are divided into three parts, an Individual Protection Standard, a Human Intrusion Standard, and multiple Ground Water Protection Standards. Because the individual parts are not fully integrated, the one that controls under a specific set of circumstances depends on the radionuclide being evaluated, its mechanisms of transport, its avenues of intake, and differences in the specified limits. Although the coefficients in Federal Guidance Report (FGR) No. 11 are being used to estimate the doses, other sources (for example, Title 10, CFR, Part 20, and/or FGR No. 13) may deserve consideration. Since the regulations specify that the reasonably maximally exposed individual is an adult, this leaves unanswered the estimated doses to other age groups, such as infants and adolescents. Summarized in this paper are comparisons of the dose coefficients for different age groups, as well as evaluations of the sensitivity of effective and organ dose estimates for adults, depending on the source of the coefficients. All the latter analyses were based only on the consumption of ground water. While the dose estimates are different, depending on the sources of the coefficients, this was not unexpected. What these evaluations demonstrate is the caution that must be exercised to ensure that a full range of considerations is taken into account in interpreting the outcome of the dose assessments being made with respect to the proposed repository.