The Waste Isolation Pilot Plant A Potential Solution for the Disposal of Transuranic Waste (1996) / Chapter Skim
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4 ENGINEERING TO IMPROVE PREDICTED REPOSITORY PERFORMANCE
4 ENGINEERING TO IMPROVE PREDICTED REPOSITORY PERFORMANCE
Pages 47-57
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From page 47... ...
Development of the disturbed rock zone (DRZ) and the associated floor uplift will create a sink for any brine flowing into the room, while simultaneously raising the waste drums above the brine, thus minimizing any immersion of the drums were liquid brine to be present.
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From page 48... ...
the rooms will probably retain significant local permeability, these materials can be isolated from each other by effective room and pane} seals. There seems to be no reason why such seals cannot be designed to be as effective as shaft seals.
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From page 49... ...
The field extraction methods currently used in New Mexico potash mines result in substantial ground deformation, both above and below the mined-out horizon, and surface subsidence. The ground deformation and subsidence over the mined-out area involve fracturing of the overlying strata, such as the Culebra Dolomite and the Dewey Lake Red Beds.
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From page 50... ...
Further, it is feasible, probably with no major increase in cost, to design the repository so that waste containers avoid contact with brine, thereby essentially eliminating gas generation, and to ensure that waste panels are isolated from each other effectively by seals that are comparable in permeability (Io-'6 m2) to shaD seals.
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From page 51... ...
These PA calculations are based on the assumption that there are no designed seals in any of the underground excavations. Thus, shaft seals alone are sufficient to prevent radionuclide release for the undisturbed case.
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From page 52... ...
In designing the seal system, it is necessary to Incorporate features that effectively will prevent vertical flow of fluid both within the shaft itself and within an annular region extending about one-half to one shaft radius from the shaft wall into the rock. Within this region, referred to as the DRZ, the initially intact, essentially Impermeable salt has been fractured as a consequence of rock stress changes introduced by the process of excavation and by the continuing changes that have occurred over the decade or so since Me WIPP shaRs were excavated (Figure 4.3~.
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From page 53... ...
Shaft station monolith FIGURE 4.2 Arrangement of the WIPP shaft sealing system. Source: Department of Energy ( 1995d, Figure 2-1,
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From page 54... ...
Source: RE/SPEC calculations done under contract to the Sandia WIPP Shaft Sealing Program, in RST Calculation File 325/]
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From page 55... ...
compacted clay in the WIPP shaDs as a function of time and depth. Source: RE/SPEC calculations done under contract to the Sandia WIPP Sha:Pc Sealing Program, in RST Calculation Files 325/11/03, 325/11/04, and in RE/SPEC External Memorandum RSI(RCO)
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From page 56... ...
However, the reality of salt creep is indisputable; salt around the shah definitely will flow to seal in the shaft plug and reheal the disturbed rock zone. Because DOE proposes to use compacted crushed salt as the shaft seal material, this too should reconsolidate eventually to a density and impermeability comparable to that of intact salt.
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From page 57... ...
As discussed at the beginning of this chapter, with careful room and panel seal designs, it should be possible to inhibit room-room hydrologic communication. Whether or not ~nBc seals contribute to the overall isolation capability of the repository depends on the credence given to the human intrusion scenarios that must be examined according to 40 CFR 194.
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