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This paper describes and discusses the major challenges of spent fuel management in Germany after the phase-out of nuclear electricity generation was decided in 2011 and a new repository siting procedure was implemented in 2013. Consequences from those decisions which were legally founded by amendments of the German Atomic Energy Act (AtG) result in the need to transfer all remaining spent fuel from limited reactor operation (last reactor shutdown until the end of 2022) into casks for subsequent dry interim storage on-site. Storage licenses are generally issued site-specific considering specific dual purpose casks (DPC) and their inventories and they are generally limited to 40 years so far. But the need for extending the interim storage period in the future has become obvious. Even though, this may not be an issue to be solved already today questions about additional safety demonstrations will arise as soon as licenses need to be extended. Certainly, these questions will ask for reliable data about the long term performance and safety of structures, systems, and components, e. g. the long term performance of cask components and materials like bolted closure systems including metal seals, or fuel rod behaviour concerning cladding materials under stress and temperature conditions. In case of dual purpose casks for storage and transportation this includes aspects on how to demonstrate transportability during or after several decades of interim storage. Long term investigations often require plenty of time and therefore need to be initiated timely.
This presentation addresses safety aspects concerning dual purpose casks for transportation and storage of spent fuel and high level radioactive waste. The long term performance of casks and their safety relevant components like sealed lid systems and the long term performance of cask internals, especially spent fuel assemblies are discussed. Transportation after interim storage is another key issue and due to the fact of delayed disposal projects current interim storage periods need to be extended causing additional safety demonstration needs for longer periods of time. Regarding this situation present BAM research activities in this area and their preliminary outcomes are presented.
This presentation starts with a brief overview about the current situation of spent nuclear fuel and high level waste storage in Germany followed by a discussion of the expected timeline towards final disposal. Furthermore an overview is presented about research programmes for radioactive waste disposal and also extended interim storage issues due to the delay of the national repository siting procedure. In the second part of the presentation BAM research activities related to extended interim storage are addressed. This includes the status and preliminary results of proactive R&D projects concerning metal seals, degradation effects of polymers used as neutron shielding materials and finally elastomer seals.
Bisherige Betriebserfahrungen und Erkenntnisse lassen die grundsätzliche Eignung der Transport- und Lagerbehälter auch über 40 Jahre hinaus erwarten.
Eine Verlängerung der genehmigten Zwischenlagerdauer erfordert eine Neugenehmigung. Hierbei sind die zu diesem Zeitpunkt sicherheitstechnisch relevanten Eigenschaften der tatsächlich vorhandenen Inventare und Behälter zu berücksichtigen.
Sicherheitstechnische Nachweise sind auf Grundlage belastbarer Daten und Erkenntnisse zu führen. Diese müssen rechtzeitig verfügbar sein (z.B. Betriebserfahrungen oder zusätzliche F&E-Programme z.B. zu Behälterdichtsystemen oder Inventarverhalten).
Alterungsmanagementprogramme und periodische Sicherheits-überprüfungen während der Zwischenlagerung haben sowohl für die verlängerte Zwischenlagerung als auch für nachfolgende Transporte eine erhebliche Bedeutung.Die Schaffung eines spezifischen Regelwerks für die verlängerte Zwischenlagerung von Transport- und Lagerbehältern und deren nachfolgendem Abtransport unter Berücksichtigung der Anforderungen aus beiden Verwendungsbereichen erscheint sinnvoll.
Eine verlängerte Zwischenlagerung dient ausschließlich der Überbrückung bis zur Endlagerung. Hierbei sollten die bestehenden Behälter und Inventare frühzeitig in die Überlegungen zur Definition von Anforderungen für die Endlagerung einbezogen werden.
Die internationalen Entwicklungen und Untersuchungen im Bereich der längerfristigen Zwischenlagerung sollten zur Nutzung von Synergieeffekten weiter verfolgt, ausgewertet und mitgestaltet werden.
This presentation addresses the current German policy in nuclear waste management and illustrates significant changes throughout the last decades. With the reset of the high level waste repository siting process in 2013 the need for extending interim storage beyond initial license periods will become a future challenge. For that purpose knowledge needs to be enhanced and data gaps need to be closed timely. In addition, international collaboration in R&D and regulatory improvements are explained.
Integration across storage, transportation and disposal – important elements of the German program
(2016)
This presentation addresses the following issues. Unexpected changes in national nuclear policy have significantly affected spent fuel management strategies.
The initial German spent fuel and HLW disposal concept has been delayed and finally “reset” by federal law in 2013. Repository site selection criteria and procedures will be defined by the Disposal Commission’s report end of June 2016. Final site selection should be finished by 2031.
The consistent German concept of dry interim storage in dual purpose casks has proven to be a safe and secure spent fuel management strategy.
The need for the extended interim storage of spent fuel and HLW casks towards disposal implicates additional challenges for the nuclear waste management strategy in Germany.
Recently, governmental research programs have been adjusted to address technical and scientific issues also in the predisposal area.
Interim storage, subsequent transportation, and final disposal are closely linked. Integrated approaches concerning waste package designs and operations are supposed to be beneficial for the establishment of efficient long-term spent fuel and HLW management strategies.
The Bundesanstalt für Materialforschung und –prüfung (BAM) and Sandia National Laboratories (SNL) entered into a Memorandum of Understanding (MOU) in September 2012 to foster technical collaborations in the areas associated with the backend of the commercial nuclear fuel cycle. Specifically, the focus is on packaging, transportation, and storage of commercial spent nuclear fuel. The institutes meet about twice each year, alternating between institutes. This provides the opportunity for staff members from the host organization more exposure to technical issues that are of concern internationally and to collaborate with technical experts working on similar problems.
Since 2012, the focus of the meetings has been on technical issues associated with extended dry storage and subsequent transportation of commercial spent fuel. Topics range from hydride effects on cladding integrity, spent fuel response during Normal Conditions of Transport (NCT), finite element analyses of fuel and cask response to accident conditions, bolt and seal behavior over extended periods of time, and corrosion associated with bolts, metallic seals, and stainless steel canisters.
This MOU has provided an effective leverage for technical collaboration. For example, SNL is funding (through DOE), Savannah River National Laboratories (SRNL) to look at bolt and seal degradation issues. SRNL has an MOU with BAM to collaborate on bolt and seal degradation during extended storage. Likewise, Sandia and BAM are collaborating with the EC Joint Research Center on an International Nuclear Energy Research Initiative (I-NERI) to investigate spent fuel behavior when subjected to mechanical loadings. This important work will provide insight into failure mechanisms, as well as spent fuel release fractions, given a breach of the cladding wall.
This presentation provides an overview of high ranked technical issues associated with extended storage and subsequent transportation, as well as the work underway at BAM and SNL that are addressing these issues.