Paper No. 6
Presentation Time: 1:30 PM-5:30 PM
GEOLOGIC, HYDROLOGIC AND GEOCHEMICAL FEATURES, EVENTS AND PROCESSES (FEPS) THAT COULD AFFECT WASTE ISOLATION AT THE PROPOSED YUCCA MOUNTAIN REPOSITORY: U.S. NUCLEAR REGULATORY COMMISSION'S (NRC'S) RISK-INSIGHTS BASELINE STUDY
The NRC staff has developed insights into the significance of geologic, hydrologic and geochemical features (e.g., hydrologic properties of unsaturated zone; quantity and chemistry of seepage water; transport distance in saturated alluvium; ash production by an eruption), events (e.g., infiltration; climatic change; faulting; igneous activity; transient percolation; seismic loading) and processes (e.g., matrix diffusion; colloidal transport) that could either affect a large number of radioactive-waste disposal packages, or significantly affect radionuclide releases from waste packages, or could significantly affect the transport of radionuclides through the geosphere and biosphere at Yucca Mountain, Nevada (YM). The significance to waste isolation of natural system FEPs is based upon review of and experience with total system performance assessments, subsystem analyses, auxiliary calculations. These analyses estimate the capability of the site to isolate waste. Integrity of waste packages, slow releases of radionuclides from degraded waste packages, and long travel times due to expected pathway characteristics contribute to waste isolation. The geologic, hydrologic and geochemical FEPs that result in a significant impact on waste isolation capability and associated with the dose-based performance criteria (regulations in Title 10 of U.S. Code of Federal Regulations, Part 63, "Disposal of High-Level Radioactive Wastes in a Proposed Geologic Repository at Yucca Mountain, Nevada"), help focus the NRC staff's review of the U.S. Department of Energy's potential license application to construct a high-level radioactive waste repository at YM.
The NRC staff views expressed herein are preliminary and do not constitute a final judgment or determination of the matters addressed or of the acceptability of a license application for a geologic repository at Yucca Mountain.