Entergy Nuclear/Pilgrim Station

Current regulatory practice from the NRC lists Regulatory Guide 1.109 (RG-1.109) as the only recognized methodology for calculating dose impact from effluent releases of radioactivity. This approach utilizes dose conversion factors (DCFs) that were derived primarily from ICRP-2 methods. However, the dose limits presented in the revised 10CFR20 assume that at the low doses associated with public exposure, only stochastic effects (i.e., effective whole body dose equivalent ) are applicable. Annual limits of intake, derived air concentrations, and effluent concentration limits in Appendix B to 10CFR20 are all based on ICRP-30 methodologies. This presentation discusses some of the impacts of using dose conversion factors from ICRP-26/30 in RG-1.109 effluent dose calculations.

Dose calculations were performed for a representative set of nuclides using DCFs obtained both from RG-1.109 and the EPA’s Federal Guidance Reports 11 and 12. In most cases, DCFs from ICRP-26/30 are a factor of about 2 times higher than RG-1.109, and in one case, over 20,000 times higher. Only in a limited number of cases were DCFs from RG-1.109 higher. Doses resulting from ground deposition, inhalation, and ingestion were calculated for each set of DCFs. Ground plane deposition dose dominated the total dose contribution from all pathways calculated in this assessment. Overall, total doses calculated using ICRP-26/30 factors were an average of 2 times higher than corresponding Regulatory Guide 1.109 doses.