Application for approval of derived authorized limits for the release of the 190-C trenches and 105-C process water tunnels at the Hanford Site: Volume 1 - Dose assessment and results

As part of environmental restoration activities at the Hanford Site, Bechtel Hanford, Inc. (BHI) is conducting a series of evaluations to determine appropriate release conditions for specific facilities following the completion of decontamination and decommissioning (D and D) projects. The release conditions, with respect to the residual volumetric radioactive contamination, are termed authorized limits. The report that follows provides the necessary evaluations for the 190-C Trenches and 105-C Process Water Tunnels to serve as the technical basis for a request for approval of authorized limits of residual radioactive contamination levels associated with these facilities. Based on the results of these evaluations, it is determined that: (1) individual doses potentially associated with the proposed release of these facilities (isolated below grade) will be less than 1 mrem/y (based on the results of a conservative radiation exposure scenario analysis conducted using both RESRAD-BUILD and the residential scenario developed to support the revised US Nuclear Regulatory Commission (NRC) policy on decommissioning), (2) the collective doses that could potentially result associated with the proposed release will be far less than 10 person-rem, and (3) because of the small quantity of residual radioactive contamination associated with these facilities, the limited recharge that occurs at the Hanford Site, and estimated results from a conservative ground water screening model (associated with the NRC residential scenario), release of these facilities poses no significant threat to ground water resources. Further, because of the low radiation doses estimated for these facilities, additional evaluation of the as low as reasonably achievable (ALARA) considerations are not justified; the ALARA review supports the release of these facilities without further cleanup or delay