Nuclear Fuel Cycle and Materials
Management of Spent Fuel from Power Reactors
Providing Technical Guidance on Good Practices for Long Term Storage of Spent Fuel
1. Data Requirements and Maintenance of Records for Long term Management of Spent Fuel
The growing inventory of spent fuel in the majority of Member States, without predictable agenda for ultimate management of the downstream, has given rise to a continuing requirements for longer-term storage as well as needs for additional storage facilities, pending retrievability as an assumed condition for the future. In view of these trends, keeping good track of the information on the spent fuel has been gaining more and more importance as required for long-term management spent fuel.
The objective of this task is to provide a guidance on the data that should be recorded and maintained to support the safe handling and treatment of such fuel in the future. Such need for spent fuel information management exist as a requirement in national laws or international convention. This may additionally assist regulatory authorities and help to provide assurance to the public of the nuclear industry's ability to deal with spent-fuel arisings in an acceptable fashion such that the issue is not seen as an impediment to the continued use and development of nuclear power. Another objective is to describe those issues in terms of data parameters suitable for use in database systems that could be operated either by utilities or on a national basis. As a first stage in the implementation of these objectives, the various stages in the spent-fuel-management routes from discharge from the reactor through to conditioning for disposal, refabrication or reprocessing are identified.
The general content for the guidance has been formulated through a couple of consultancy meetings in the previous years. A Technical Meeting was held 30 June - 3 July 2003 to review the current status of Member States and and a consultancy meeting was held 24-28 April 2004 to elaborate a TECDOC on the subject. The TECDOC was issued in November 2006 as TECDOC-1519, "Data Requirements and Maintenance of Records for Spent Fuel Management". A Technical Meeting is planned for May 2008 to address spent fuel data management for long term storage of fuel.
2. Economics of Spent Fuel Storage
Economics is one of the key factors for consideration in the selection and implementation of a storage system especially for AFR storage which are usually designed as an independent facility from the nuclear power plants. With expanding requirement and market for spent fuel storage, interest in economic aspect has been rapidly growing in recent years in an increasing number of Member States. There has been little literature, however, which would provide comprehensive guidance on the economic aspect of spent fuel storage, the only one among the IAEA publication has been being the Technical Report Series No.361, "Cost Analysis Methodology of Spent Fuel Storage" (1994).
This task aims to review and revise the past TRS-361 with a view to provide the interested readers with informed guidance on economics as an important factor for consideration in spent fuel storage project. A TM was held in September 2002 where discussions were held on such issues as factors affecting the economics of spent fuel storage and cost considerations in spent fuel storage projects, as well as methodologies for economic analyses, for more comprehensive scope of the revisional work. Consultancy meetings were held 28-30 April 2003 and 4-7 October 2004 to advance work on the technical report revision on this topic. A Draft of the TRS is being finalized for publication in 2008.
3. Remote Technology Applications in Spent Fuel Management
Remote systems feature is an integral part of facilities for work to be carried out inside shielding and/or containment engineered to protect workers and the environment from hostile sources like spent nuclear fuel. Remote systems technology has been extensively applied to a variety of work in spent fuel management facilities with such benefits as dose reduction to workers, enhancement of operational performance or reliability, saving of labour costs, etc.
In recognition of the essential role of remote technology in spent fuel management, several technical documents have been published with information on various technical experiences in remote technology applications to spent fuel management. The first of this series , Remote Technology Related to the Handling , Storage and Disposal of Spent Fuel (IAEA-TECDOC-842), which was based on proceedings of a Technical Committee Meeting held in Alburquerque, New Mexico, 5-8 December 1994. Another publication, Remote Technology in Spent Fuel Management(IAEA-TECDOC-1061) was issued in 1999 based on the proceedings of an Advisory Group Meeting held in Vienna, 22-25 September 1997.
As a regular extension of the past efforts, an updated technical document entitled "Remote Technology Applications in Spent Fuel Management" (TECDOC-1433) was issued in 2005 to provide an overview of remote technology applications to spent fuel management by compiling the information collected from a couple of consultancies and other related literature. It was noted from the survey that the potential for future applications has significantly risen with the anticipation for repository construction in several countries (e.g. US, Finland) and in research and development of innovative nuclear systems to be launched in the context of sustainable development of nuclear energy by such international initiatives as INPRO and Gen IV.
4. Selection Criteria for AFR Storage Facilities
The importance of AFR storage for spent fuel management has been growing in many Member States. In the near term, additional storage facilities will be required for more and more reactor sites, the past efforts to extend the storage capacities of AR pools by higher density methods having almost been used up leaving little technical leeway for further squeezing. In the longer term, the number of reactors with lifetime operation to retirement will multiply and their decommissioning will require relocation of the spent fuel to an AFR if no other provision is available by that time. For the countries with "wait and see" policy, the step to AFR storage will sooner or later be inevitable for their spent fuel management, if the current circumstance continues for long term. Under these circumstances, some of the Member States have already implemented AFR storage and a growing number of Member States are taking actions or contemplating towards AFR storage.
Looking at the technological trend for AFR storage, there is a conspicuous tendency toward dry storage in recent years, although wet storage in pool is still predominant world-wide. Several different options are available for dry storage of spent fuel and a dozen of vendors offer commercial packages to the prospective market. There are a variety of factors to be considered in selecting an option or service and careful assessment of relevant criteria would be essential in setting up successful plan for implementation of AFR storage.
This task would be the first kind of systematic effort addressing the issue, although some of the related topics have been discussed in some related publications, such as TECDOC-759 "AFR Storage Concepts and Their Implementation" (1994), and TRS-240, "Guidebook on Spent Fuel Storage" (1991) . A TECDOC-1558 on "Selection of Away from Reactor Facilities for Spent Fuel Storage" was published in 2007.
5. Spent Fuel Inventories and Management
One of the essential requirements for spent fuel management activities is availability of reliable, timely data on spent fuel. It is not a trivial deal, however, to set up and maintain a database for large amount of spent fuel with updated information on inventories, characteristics, locations, and projections. Systematic collection and analyses of spent fuel data on the international level is further complicated by the fact it is dependent on multiple national inputs. The IAEA has been a major source of information on related data and is a logical choice to develop a database to provide useful data to Member States and other organizations as needed.
The purpose of this task is to review current status and to establish an enhanced database on global spent fuel data management. An update of the compiled data is being incorporated in the NFCIS database of the IAEA.
6. Long Term Storage of Spent Nuclear Fuel
A co-ordinated research programme on the safety of storage of spent fuel was conducted from 1994 to 1997. To address new trends several meetings were held until 2000. The results are published in TECDOC 1293. Three safety publications were published earlier: "Design of Spent Fuel Storage Facilities" Safety Series No 116; :"Operation of Spent Fuel Storage Facilities" Safety Series No 117; :"Safety Assessment for Spent Fuel Storage Facilities" Safety Series No 118.
This topic was also explored during a technical meeting organized by the IAEA and held in Ljubljana, Slovenia, from 18-21 October 2004. Senior representatives from regulatory and implementation authorities in Bulgaria, Croatia, the Czech Republic, Hungary, Lithuania, Romania, Slovakia, Slovenia, and the Ukraine explored the topic provisions for long term storage of spent power reactor fuel by focusing on the evolution of national approaches, operational considerations, and cooperative initiatives. The participants advised the Agency of a number of recommendations for future related activities, and notably concluded that significant progress had been made in these countries over the last few years in making provision for interim spent fuel Storage.
One of the recommendations from the October 2004 technical meeting in Ljubljana was that the IAEA should organize a technical meeting focused on handling of damaged spent fuel. Accordingly, the IAEA convened a meeting to focus on the technical aspects of handling damaged spent fuel at its headquarters in Vienna 6-9 December 2005 as discussed below.
7. Handling of Damaged Spent Fuel
Nineteen representatives from thirteen countries participated in a Technical Meeting on Handling of damaged spent fuel held from 6-9 December 2005 at IAEA headquarters in Vienna. Participants from Bulgaria, Chile, Czech Republic, France, Germany, Hungary, India, Italy, Lithuania, Slovenia, Ukraine, UK, and USA reviewed current status of related experience and practices as well as definitions and criteria for damage, and then three working groups developed recommendations associated with the handling of damaged spent fuel. The meeting Chairs summary emphasized that damage is not an intrinsic property of the fuel. Depending on its functional requirements, fuel considered damaged for one phase may not be considered damaged in a subsequent phase.
Results from this meeting were used in a smaller consultants meetings held September 2006 and December 2007 in Vienna to produce a technical document on this topic to be issued in 2008.
8. Spent Fuel Performance Assessment and Research
Spent fuel storage technology (particularly dry storage) is undergoing evolution, new fuel and material design changes are coming on stream and target burnups are increasing. As a consequence, the IAEA initiated in 1997 a Co-ordinated Research Project (CRP) on spent fuel performance assessment and research (SPAR). The final report of the SPAR project 1997-2001 was published as TECDOC-1343 in March 2003.
Spent fuel dry cask storage facility.
Building on results from preceding CRPs reported in TECDOCs 1343 (SPAR), 944, 673, and 414 (the BEFAST series), the IAEA has initiated a 'SPAR-II' CRP (2004-2008) to develop a technical knowledge base on long term storage of power reactor spent fuel through evaluation of operating experience and research by participating Member States. Specific research objectives include: fuel and materials performance evaluation; surveillance and monitoring programmes; and collection/exchange of relevant experience from participating countries. Expected research results include: a survey of research activities; operating experience; results from surveillance and monitoring programmes; and country-specific clarification of how the specifications for subsequent conditioning for reprocessing or disposal impact spent fuel storage requirements.
Representatives from 13 organizations met at the European Commissions Joint Research Centre in Karlsruhe 6-10 June 2005 to exchange information on the SPAR-II research proposals and project structure, to review the status of national activities in the area of long term spent fuel storage, and to discuss plans for subsequent documentation of SPAR-II results. Meeting results included a preliminary table of contents for the expected CRP technical document, a matrix identifying contributors to the principal TECDOC topics, as well as a number of general conclusions based on participant presentations and subsequent discussions. Participants also had the opportunity to tour the ZWILAG interim storage facility in Wuerenlingen as well as the ECs laboratory facilities at their Institute for Transuranium Elements in Karlsruhe, Germany.
Following the first research coordination meeting (RCM) held in Karlsruhe in June 2005, a smaller consultants meeting was held in November 2005 in Erlangen, Germany, to discuss plans for the second RCM as well as plans for documenting SPAR-II results. Meeting participants developed a skeleton draft of the technical document as well as an initial draft agenda for the second RCM.
The second SPAR-II RCM was hosted in Japan by their Central Research Institute of Electric Power Industry (CRIEPI) and the Japan Nuclear Energy Safety (JNES) Organization from 6 to 10 November 2006. Seventeen representatives from 14 organizations participated in the meetings in Tokyo, as well as a tour to the Akagi test center in Gunma prefecture on 8 November to tour relevant facilities including CRIEPI's cask testing capability. RCM discussions focused on status updates regarding national activities as well as a review of work since the 2005 RCM relevant to subsequent documentation of SPAR-II results. Based on the results of a May 2007 consultants meeting in Vienna, the third and final RCM will be held in Hungary in mid 2008.
9. Implementation of Burnup Credit in Spent Fuel Management
A Technical Meeting was convened on Requirements, Practices and Developments in Burnup Credit Applications in Madrid, Spain, from 22 to 26 April 2002. The purpose of this meeting was to explore the progress and status of international activities related to the burnup credit applications for spent nuclear fuel. This meeting was the third major meeting on the uses of burnup credit for spent fuel management systems held by IAEA. The proceedings of the Madrid meeting was issued as TECDOC-1378 in 2003. The proceedings of a 1997 AGM were published as IAEA-TECDOC-1013, the proceedings of a 2000 TCM as IAEA-TECDOC-1241.
The Fourth Major IAEA Technical Meeting on Burnup Credit Applications was held in London, 29 August 2 September 2005. Sixty participants from 18 countries reviewed advances in applications of burnup credit (BUC) to enhance spent fuel transportation, storage, reprocessing, and disposition. Six sessions of technical presentations were followed by four working groups (calculations, validation, compliance, regulation) and a final panel discussion among the working group co-chairs. The meeting chair concluded that the meeting represented an encouraging step forward in application of BUC based on the technical presentations and the working group discussions. The meeting proceedings were completed in 2006 and issued in 2007 as TECDOC-1547.
As recommended in the London meeting, the IAEA initiated plans for the next technical meeting on burnup credit by holding a programme planning meeting in Vienna September 2007. Tentative plans were set to hold a technical meeting on advances in burnup credit applications for spent fuel storage, transport, reprocessing, and disposition in Spain 21-24 April 2009.
10. Influence of High Burnup and MOX Fuel on Spent Fuel Management
Presently and in future a wider variety and increasing number of fuel of different designs will be discharged from Nuclear Power Reactors: MOX fuel, high burnup fuel over 50 MWd/kg HM and fuel designed for advanced reactor operations. In order to ensure appropriate and safe storage technology it is essential that the knowledge is available of the influence of such fuel designs on storage technology.
Spent fuel storage and transport cask, inside view.
IAEA-TECDOC1293 Long Term Storage of spent nuclear fuel- survey and recommendations Final Report of a co-ordinated research project 1994-1997, published in May 2002 is containing valuable information on related issues.
Consultancies were held from December 2002 to October 2006 on the "influence of high burnup and MOX fuel on spent fuel management". Objectives were to lay the foundation for a technical document (TECDOC) in 2007. The major findings are:
ISSUES OF GENERAL NATURE: The time frame for spent fuel storage (SFS) has expanded considerably during the years. This is mainly due to decisions pending for final disposition of the spent fuel. Furthermore it is widely believed that there is no need for immediate actions for the latter. SFS allows for appropriate time for technology development. A usual period considered today ranges from 30 years on, like in Russia. License applications for 40-50 years SFS are regular, as in Germany. The Netherlands is envisaging 100 years for the SFS in an away from reactor (AFR) facility to be built. Experience with wet storage amounts to about 30 years, with dry storage of fuel assemblies (FA) in casks to about 15 years. New technologies are applied such as usage of concrete as construction material for casks. Thus the issue of safe storage over extended period of time has emerged. Furthermore new technology development already employed needs consideration. That applies to increasing use of MOX fuel, higher burnup fuel (also for MOX) and including higher initial enrichment and advanced reactor operation, which all aim at more economical use of nuclear power.
WET STORAGE: In general considered not to pose problems, can be easily surveilled, defects discovered, low thermal loads on cladding material and fuel matrix, corrosion control by means of appropriate pool water chemistry, etc.
DRY STORAGE: High burnup fuel and MOX fuel influence dry storage of spent fuel. The main impacts are an increase in decay heat and neutron source strength, an increased fission gas pressure in the fuel rods and some influence on fuel cladding creep and the fuel cladding strain capability. All these factors have to be considered carefully when evaluating the dry storage behaviour of spent fuel.