Disposal of high-level nuclear waste above the water table in arid regions

Abstract

Locating a repository in the unsaturated zone of arid regions eliminates or simplifies many of the technological problems involved in designing a repository for operation below the water table and predicting its performance. It also offers possible accessibility and ease of monitoring throughout the operational period and possible retrieval of waste long after. The risks inherent in such a repository appear to be no greater than in one located in the saturated zone; in fact, many aspects of such a repository's performance will be much easier to predice and the uncertainties will be reduced correspondingly. A major new concern would be whether future climatic changes could produce significant consequences due to pogsible rise of the water table or increased flux of water through the repository. If spent fuel were used as a waste form, a second new concern would be the rates of escape of gaseous iodine129 and carbon-14 to the atmosphere. * * * Such a system would be above, rather than below, the regional water table, and if properly engineered. should remain dry at least much of the time. It would have the advantages of greater ease of construction, greater distance from the [Columbia] river, easier retrieval of waste canisters if this should prove 'As knowledge of the Y u m Marntain site grew. some members of a Peer Review COmmiUee. made up of representatives from universities and indushy, raised questions as to the possible utilization of potential hmt rccks in theunsakatedme. In February 1982. several scientists of the U S Geological Survey (USGS). in a letter to the Department of Energy F'mgram Manager for the Nevada Nuclear Waste Storage Investigations Program.. sd the hydrogeologic eonditions that should be present in the unsaturated m e beneath Yucca Mountain and concluded that they should provide a very favorable envirmment for waste disposaL At about the same time, the USGS sent a letter to the Nuclear Regdatay Commission (NRC) suggesting how NRCpropased rule 10 CFR Part 60. which was specificaUy limited to repe3itories in the saturated m e , might be modiKed to include t h m in the UP sahrrated m e A subsequent draft of 10 CFR Part 60 covm both m e s .

End of FY10 report - used fuel disposition technical bases and lessons learned : legal and regulatory framework for high-level waste disposition in the United States.

“…Spengler et al 1979 Repository moved to unsaturated zone (1982) Roseboom 1983 1982 volcanism consequences Link et al 1982 PA-84 Sinnock et al 1984NWPA Environmental Assessment (1986 [1981][1982][1983][1984] Heater tests in G-Tunnel at NTS (1980NTS ( -1989 Zimmerman and Finley 1987 Bomb pulse 36 Cl measured in boreholes (1993) Fabryka-Martin et al 1993 CSNF release measured in batch tests (1987)(1988)(1989)(1990) Site characterization performs two functions: (1) it provides information to demonstrate understanding of the behavior of the natural barriers of the disposal system; and (2) it provides information for the performance assessment, which uses scientific information to analyze the potential behavior of the waste in the engineered barriers and natural barriers in order to assess the compliance of a disposal system with regulatory requirements.…”

“…Walker 2009, Vandenbosch andVandenbosch 2007 In 1982, the USGS had identified several advantages for using the unsaturated zone at Yucca Mountain. Advantages cited included Roseboom 1983 (1) a highly porous, low permeability layer above the host layer and thus high capillarity to diminish percolation; (2) mineable but fractured tuff host rock layer to rapidly pass percolation; (3) zeolitics in nonwelded Calico Hills layer below the host layer to adsorb radionuclides; (4) passive ventilation of the repository to keep waste cool; (5) backfilling of drifts unnecessary; (6) sealing of shafts unnecessary; (7) long retrieval period because repository does not flood; (8) most waste would not contact water in the unsaturated zone since openings typically block flow; and (9) many exploratory holes could be drilled without compromising repository. Other advantages included (10) good thermal characteristics to conduct heat from the waste and (11) absence of significant economic resource deposition concurrent with tuff deposition.…”

Status of understanding of the saturated-zone ground-water flow system at Yucca Mountain, Nevada, as of 1995

“…He pointed out that groundwater movement in the unsaturated zone can be extremely slow, and disposal of waste in the unsaturated zone could provide long-term isolation. Another investigator (Roseboom, 1983) pointed out that an unsaturated-zone repository might eliminate many technical problems that could result from disposal in the saturated zone. He also argued that the waste in the unsaturated zone could be fully retrievable for a long period of time.…”

Analogues to features and processes of a high-level radioactive waste repository proposed for Yucca Mountain, Nevada

“…A letter from the U.S. Geological Survey (USGS) to the DOE alludes to data from other parts of the Nevada Test Site (NTS). In it, Roseboom (1983) specifically referred to experience with tunnels in the unsaturated zone beneath Rainier Mesa on the NTS to point out that such tunnels, in spite of intense fracturing and moderate infiltration, are generally dry except for water-bearing fractures that generally drain quickly once intersected by a tunnel. Note that these features make the tunnels in Rainier Mesa less than ideal as an analogue to Yucca Mountain.…”