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vertically or horizontally inside a thick reinforced concrete structure. These reinforced concrete structures, which are typically 2.5 feet thick for vertical systems and 3 feet thick for horizontal systems, provide shielding from radiation and protect the canister. The total weight of current dry storage systems (canister and concrete structure) is typically between 160 and 180 tons (320,000–360,000 pounds). After an initial period of cooling in wet storage (generally at least five years), dry storage (in casks or vaults) is considered to be the safest and hence preferred option available today for extended periods of storage (i.e., multiple decades up to 100 years or possibly more). Unlike wet storage systems, dry systems are cooled by the natural circulation of air and are less vulnerable to system failures. Nevertheless, it is important to emphasize that spent fuel pools are essential to operating a nuclear power plant given the need to be able to cool newly discharged fuel in a water-filled pool close to the reactor core. Pools are also advantageous for the transfer of spent fuel into and out of casks. In the United States, pools remain the dominant form of storage for spent fuel at still-operating reactor sites (pools are currently also used for at-reactor and consolidated storage in other countries, including France, Russia, and Sweden). Currently, less than one-fourth of the nation’s commercial spent fuel stockpile is being stored in dry casks, although the Electric Power Research Institute (EPRI)
Cumulative SNF (MTU)
projects this fraction will grow steadily in coming years and that all operating power reactors will have dry storage facilities in operation by 2025.66 Figure 15 shows EPRI’s projection for the expected amount and distribution of commercial spent fuel in dry versus wet storage over the next several decades.67 While current storage arrangements have been judged adequately safe and secure by the relevant regulatory authorities—in fact, as discussed in chapter 3, the NRC in 2010 updated its “Waste Confidence Decision” to state that at-reactor or away-from-reactor spent fuel could be stored safely for up to 60 years after the termination of an operating reactor’s license (with extensions up to 60 more years)68—it is clear that today’s institutional arrangements and storage technologies were not designed for the lengthy storage timescales that now appear inevitable for at least some portion of the nation’s spent fuel inventory. Assuring safe and secure storage of SNF and HLW over extended periods of time will require continued public and private efforts—including efforts by the NRC, DOE, and industry organizations such as EPRI —to conduct rigorous research and oversight and continuously incorporate lessons learned from new developments or events. For example, it will be important to continue exploring fuel degradation mechanisms in dry storage, particularly since many current safety assessments are based on an examinations of fuel with lower burnup than is now “standard” and do not account for storage times of the Figure 15. EPRI Projection of Cumulative length now being contemplated. Further Spent Nuclear Fuel from Commercial research may identify unanticipated Nuclear Power Plants in Pool Storage problems with extended fuel storage (e.g., and Dry Storage, 2010–2060 unexpected corrosion rates) and will help ensure that problems are detected and 140,000 appropriately mitigated if they emerge. 2010: 65,000 MTU discharged Given the history of the U.S. waste 2025: 96,000 MTU discharged 120,000 management program, it is perhaps not 2050: 133,000 MTU discharged surprising that the need for extended Dry storage at <70 sites by 2030 100,000 storage has come to symbolize the program’s larger failure to perform so 80,000 far. Nonetheless we find that developing POOL STORAGE Estimated dry storage IN VE NTORY 60,000 extended storage capacity, if approached systems*: in a way that maximizes its system 2010: ~1,400 loaded 40,000 2025: ~3,700 loaded benefits, could strengthen the U.S. waste 2050: ~9,500 loaded D RY STORAGE management program as a whole. 2075: ~10,800 loaded INV EN TORY 20,000 First, having extended storage capability preserves options and enhances 0 flexibility while other elements of a 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 comprehensive waste management Aug 2010, Energy Resources International, Inc. system—including options for the final B l u e R i bb o n C o m m i s s i o n o n A m e r i ca’ s N u c l e ar F u t u r e
