Generic repository design concepts and thermal analysis (FY11).

Abstract

(U)Reference concepts for geologic disposal of used nuclear fuel and high-level radioactive waste in the U.S. are developed, including geologic settings and engineered barriers. Repository thermal analysis is demonstrated for a range of waste types from projected future, advanced nuclear fuel cycles. The results show significant differences among geologic media considered (clay/shale, crystalline rock, salt), and also that waste package size and waste loading must be limited to meet targeted maximum temperature values. TABLES Executive SummaryIn this study, the UFD R&D Campaign has developed a set of reference geologic disposal concepts for a range of waste types that could potentially be generated in advanced nuclear FCs. A disposal concept consists of three components: waste inventory, geologic setting, and concept of operations. Mature repository concepts have been developed in other countries for disposal of spent LWR fuel and HLW from reprocessing UNF, and these serve as starting points for developing this set. Additional design details and EBS concepts will be considered as the reference disposal concepts evolve.The waste inventory considered in this study includes: 1) direct disposal of SNF from the LWR fleet, including Gen III+ advanced LWRs being developed through the Nuclear Power 2010 Program, operating in a once-through cycle; 2) waste generated from reprocessing of LWR UOX UNF to recover U and Pu, and subsequent direct disposal of used Pu-MOX fuel (also used in LWRs) in a modified-open cycle; and 3) waste generated by continuous recycling of metal fuel from fast reactors operating in a TRU burner configuration, with additional TRU material input supplied from reprocessing of LWR UOX fuel.The geologic setting provides the natural barriers, and establishes the boundary conditions for performance of engineered barriers. The composition and physical properties of the host medium dictate design and construction approaches, and determine hydrologic and thermal responses of the disposal system. Clay/shale, salt, and crystalline rock media are selected as the basis for reference mined geologic disposal concepts in this study, consistent with advanced international repository programs, and previous investigations in the U.S. The U.S. pursued deep geologic disposal programs in crystalline rock, shale, salt, and volcanic rock in the years leading up to the Nuclear Waste Policy Act, or NWPA (Rechard et al. 2011). The 1987 NWPA amendment act focused the U.S. program on unsaturated, volcanic rock at the Yucca Mountain site, culminating in the 2008 license application. Additional work on unsaturated, crystalline rock settings (e.g., volcanic tuff) is not required to support this generic study. Reference disposal concepts are selected for the media listed above and for deep borehole disposal, drawing from recent work in the U.S. and internationally. The main features of the repository concepts are discussed in Section 4.5 and summarized in Table ES-1. Temperature histories at the waste packag...

Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

“…A small proportion of the REEs in SNF (HLW) are represented by short-lived isotopes (half-life T 1/2 up to 10 years: 144 Ce, 147 Pm, 154 Eu, 155 Eu) and medium-lived radionuclides (T 1/2 less than 100 years: 151 Sm). The decay of these REE radionuclides makes the main contribution to the heat released by SNF in the first few years after its removal from a nuclear reactor [18,19] (Tables 1 and 2, Figure 1). 2.…”

“…Table 2. The contribution of radionuclides to the heat released by spent fuel from a PWR reactor with a burn-up of 40 (a) and 60 (b) GW × d/t, in the range from 1 year to 500 years [18,19].…”

“…Figure 1. Contribution of decay of radionuclide groups to the heat released by spent fuel from a PWR reactor (burnup 60 GW × d/t) over 1 year to 10 9 years (see open access Refs [18,19]…”

Cross-disciplinary Reactor-to-Repository Framework for Evaluating Spent Nuclear Fuel from Advanced Reactors

“…For the repository design, we considered the clay repository design reported in Atz ( 14) and Hardin et al (47). It is a horizontal disposal, with the initial drift spacing of 30 m. The containers with SNF are inserted into carbon steel overpacks and surrounded by bentonite buffer material.…”