Extended storage

billion range.233 Today, most countries expect implementation periods for their repository programs of at least four to six decades. In Finland, Sweden and France, implementation schedules are expected to be shorter because the sites for the disposal programs have already been selected. However, even in these countries, neither timetables nor effective costs are set in stone. Thus, interim storage of spent fuel and HLW will continue for many decades up to more than 100 years and even longer.

EXTENDED STORAGE

This approach across countries will result in the further construction of extended interim storage capacities and their operation for a very long time (from many decades to 100 years or more). This discussion already took place in the 1980s and 1990s, above all in the US in connection with Negotiated Monitoring Retrievable Storage (NMRS) or the concepts of the Away From Reactor AFR234 and in Great Britain with extended storage over periods of 100 to 300 years.235 The strategy of “Away-from-Reactor-Storage” was also brought up again by the Blue Ribbon Commission (2012) in the US.236 The integrity and retrievability of spent fuel (and HLW) over such storage periods is thus a growing challenge, as is the task of monitoring and maintenance. The goal is to keep options open for further waste management paths and their requirements such as transport, conditioning, and packaging. In consequence, there is a great need for research, for example on the long-term behavior of fuel, degradation mechanisms, and other knowledge gaps.

The integrity and retrievability of spent nuclear fuel and other high-level waste over long storage periods is a growing challenge, as is the task of monitoring and maintenance. The goal is to keep options open for further waste management paths and their requirements such as transport, conditioning, and packaging.

The international subcommittee of the Electric Power Research Institute (EPRI) Extended Storage Collaboration Program (ESCP) identifies in a report technical data gaps for dry storage facilities, especially concerning the degradation of cladding and welded canisters.237 The EPRI report also shows that countries have specific problems depending on their respective dry storage system and the overall situation. Other topics concerning spent fuel management in the long term are data provision and documentation, the handling of damaged spent fuel, and the influence of burn-up and fuel type (uranium or MOX). Solutions are needed for questions like: Which safety requirements for long-term storage are needed? How long is high-level waste safely manageable? Which type of infrastructure (incl. hot cells) is needed in the long term? How and how long can or should expertise be preserved?

233 Buser, M. 2016b “Kosten nukleare Entsorgung Schweiz: eine erste Evaluation des Systems der Kostenberechnung,” (Costs of Nuclear Waste for Switzerland: A primary evaluation of the system of calculating costs) Report for Greenpeace Switzerland, January 2016, viewed 2 August 2019, http://m.greenpeace.org/switzerland/Global/switzerland/publications/ce_various/2016/Buser_Sammelmappe.pdf. 234 Shrader-Frechette, K. 1993, Burying Uncertainty, Risk and the Case Against Geological Disposal of Nuclear Waste, University of California Press, pp. 218.ff. 235 Nirex Ltd. 2004, Literature Review of Approaches to Long-Term Storage of Radioactive Waste and Materials, Nirex Report N/107, July 2004 236 Blue Ribbon Commission 2012, Report to the Secretary of Energy, January 2012 237 Electric Power Research Institute 2012, “International Perspectives on Technical Data Gaps Associated

With Extended Storage and Transportation of Used Nuclear Fuel” International Subcommittee Report,

Extended Storage Collaboration Program

KEY CHALLENGES OF EXTENDED STORAGE

The growing inventories and risks puts pressure on governments in countries that use nuclear energy to better manage the gap between interim storage and the realization of underground repositories or equivalent solutions.238 A number of key issues for storage management are up for discussion in the future. They concern for instance a general safety analysis of the worldwide storage policies in respect to wet-storage in ponds and dry storage in vaults or other sites as well as a general risk assessment on the worldwide spread of interim storage facilities and over storage periods exceeding 100 years. For wet storage subcriticality over such storage times must be addressed, as well as the whole range of ageing and degradation mechanisms of the stored spent fuel (also in dry casks). In view of the long storage periods, particular attention must be paid to socio-political and economic factors that would increase “the risk that adequate maintenance and security at storage sites” could end before the waste is removed.239

Finally, the longer-term storage of low- and intermediate-level (LILW) waste is to be addressed. While fewer safety problems emerge during the interim storage of LILW, individual waste categories pose special challenges here as well, both in terms of their handling and the associated risks in closed facilities. The IAEA requires that “under conditions of long term storage awaiting disposal, the package must successfully maintain its characteristics under two very different environments”; if this cannot be guaranteed, further problems may arise, for instance when the repository operator refuses to receive waste that does not comply with the requirements of the Waste Acceptance Criteria (WAC) “as directed by the operator’s license conditions.”240 Therefore, safety authorities such as the French ASN have recently been advising the repository operator to look into and provide a solution for these questions.241

238 Buser, M. 2019, Wohin mit dem Atommüll? (Where to put the nuclear waste?), Rotpunkt, pp. 204-206. 239 Holt, M. 2009, pp. 23 240 IAEA 1998, Interim Storage of Radioactive Waste Packages, Technical Report Series N° 390, International Atomic

Energy Agency, pp. 11-13, viewed 24 August 2019, https://www-pub.iaea.org/MTCD/Publications/PDF/TRS390_scr.pdf 241 Autorité de sûreté nucléaire (French nuclear safety authority) 2017, French National Plan for the Management of Radioactive Materials and Wastes 2016-2018, 30 December, viewed 2 August 2019, http://www.french-nuclear-safety.fr/Information/Publications/Others-ASN-reports/French-National-Plan-forthe-Management-of-Radioactive-Materials-and-Waste-for-2016-2018