Projected expansion of nuclear power beyond the year 2014 will result in the need for commercial spent nuclear fuel (CSNF) management options in addition to the currently legislated CSNF storage capacity at the proposed Yucca Mountain geological repository. At present, 70,000 MTHM of storage capacity has been authorized, with a projection that 63,000 MTHM would be used for CSNF. This report extends preliminary analyses of the maximum physical capacity of the Yucca Mountain repository, presented in EPRI report 1013523. EPRI is confident that at least four times the current CSNF limit (~260,000 MTHM) and possibly upwards of nine times the limit (~570,000 MTHM) could be emplaced with additional site characterization.
The purpose of the analyses presented in this report is to confirm the feasibility, performance, and robust safety of expanded Yucca Mountain capacity options. The analyses also provide an initial cost basis by which to compare these expanded capacity options with alternative management approaches, such as a second repository, extended interim storage, or reprocessing.
The report presents the results of analyses in four areas:
Thermal, hydrological, and mechanical analyses involving comprehensive fracture-matrix interaction and application of three-dimensional models to the Yucca Mountain site
Ventilation and mining technology suitable for expanding the capacity at Yucca Mountain
Long-term performance and safety of an expanded capacity repository at Yucca Mountain
Cost analysis of expanding the CSNF capacity at Yucca Mountain
ResultsEPRI has taken the lead in examining Yucca Mountain expansion options for CSNF disposal, focusing on three key strategies, as follows:
Option 1: Expanding the current line-load/high-temperature operating mode (HTOM) design over the maximum rock area at Yucca Mountain considered suitable for spent fuel disposal by the DOE Yucca Mountain Project
Option 2: Constructing a multi-level set of emplacement drifts in which the exact same geometrical configuration of emplacement drifts of the line-load/HTOM design would be built at three different levels
Option 3: Constructing a single-level repository by grouping three emplacement drifts (grouped drift), in which two additional emplacement drifts would be positioned at 20-m horizontal offsets on either side of each of the currently planned drifts
Option 1 can be combined with Option 2 or 3 to provide for even greater Yucca Mountain capacity.
This report is organized as follows. Section 2 presents the results of comprehensive two-dimensional and full three-dimensional models to analyze thermal, hydrological, and mechanical effects of Options 2 and 3, which were formerly evaluated using simple one- and two-dimensional models. Impacts on the spatial and temporal redistribution of water vapor and condensed water are evaluated, with particular emphasis on how liquid water, initially driven away by radiogenic heating, eventually condenses and drains around but not through the emplacement tunnels. Possible coupling among thermal, hydrological, and mechanical processes during the initial thermal heating period are also analyzed. Section 3 explores the engineering feasibility of constructing multiple emplacement drifts for Options 2 and 3, with a discussion of impacts on ventilation. The potential impacts on long-term safety from positioning multiple emplacement drifts within the existing disposal blocks at Yucca Mountain are discussed in Section 4. A preliminary cost analysis is presented in Section 5 to provide an initial basis for comparing expanded capacity options with other waste management approaches. Section 6 provides a summary of results and recommendations based on the reported analyses.
Application, Value and Use
The advantage of the proposed expansion designs examined in this report is that DOE can proceed without delay into licensing with its current design for the first 70,000 MTHM of high-level waste and CSNF disposal. Concurrent R&D would establish the technical bases necessary for future repository expansion.
If all U.S. operating commercial nuclear reactors each operated for a total of 60 years, approximately 140,000 MTHM of CSNF would be available for disposal, including the existing CSNF from reactors previously shut down. This analysis shows that it is possible for the Yucca Mountain repository to store not only all of the waste from existing U.S. nuclear power plants, but also waste produced from a significantly expanded U.S. nuclear power plant fleet for at least several decades. Even if the United States decides to close the nuclear fuel cycle by introducing reprocessing along with the use of advanced reactors, Yucca Mountain could, if necessary, serve as the only CSNF and high level radioactive waste repository needed for at least several decades into the future, if not longer. This potential for expanded Yucca Mountain capacity would allow time for the necessary R&D to accomplish a full-scale and economically competitive closed fuel cycle.