Evaluation of Groundwater Impacts to Support the National Environmental Policy Act Environmental Assessment for the INL Remote-Handled Low-Level Waste Disposal Project

Schafer, Annette ; Rood, Arthur S. ; Sondrup, A. Jeffrey

Idaho National Laboratory

关键词: Radioactivity;    Radiation Protection;    Transport;    Waste Forms;    Half-Life;   

DOI  :  10.2172/1032018
RP-ID  :  INL/EXT-10-19168 rev 3
RP-ID  :  DE-AC07-051D14517
RP-ID  :  1032018

美国|英语

来源: UNT Digital Library

【 摘 要 】

Groundwater impacts have been analyzed for the proposed remote-handled low-level waste disposal facility. The analysis was prepared to support the National Environmental Policy Act environmental assessment for the top two ranked sites for the proposed disposal facility. A four-phase screening and analysis approach was documented and applied. Phase I screening was site independent and applied a radionuclide half-life cut-off of 1 year. Phase II screening applied the National Council on Radiation Protection analysis approach and was site independent. Phase III screening used a simplified transport model and site-specific geologic and hydrologic parameters. Phase III neglected the infiltration-reducing engineered cover, the sorption influence of the vault system, dispersion in the vadose zone, vertical dispersion in the aquifer, and the release of radionuclides from specific waste forms. These conservatisms were relaxed in the Phase IV analysis which used a different model with more realistic parameters and assumptions. Phase I screening eliminated 143 of the 246 radionuclides in the inventory from further consideration because each had a half-life less than 1 year. An additional 13 were removed because there was no ingestion dose coefficient available. Of the 90 radionuclides carried forward from Phase I, 57 radionuclides had simulated Phase II screening doses exceeding 0.4 mrem/year. Phase III and IV screening compared the maximum predicted radionuclide concentration in the aquifer to maximum contaminant levels. Of the 57 radionuclides carried forward from Phase II, six radionuclides were identified in Phase III as having simulated future aquifer concentrations exceeding maximum contaminant limits. An additional seven radionuclides had simulated Phase III groundwater concentrations exceeding 1/100th of their respective maximum contaminant levels and were also retained for Phase IV analysis. The Phase IV analysis predicted that none of the thirteen remaining radionuclides would exceed the maximum contaminant levels for either site location. The predicted cumulative effective dose equivalent from all 13 radionuclides also was less than the dose criteria set forth in Department of Energy Order 435.1 for each site location. An evaluation of composite impacts showed one site is preferable over the other based on the potential for commingling of groundwater contamination with other facilities.