Nuclear Fuel Cycle and Materials
Management of Spent Fuel from Power Reactors
Promoting technologies and strategies for spent fuel management1. Operation and maintenance of spent fuel storage and transportation casks and containers
The role of casks, which has been essential for transportation of radioactive materials to the service of nuclear industry, is now expanding in particular with the applications in dry storage of spent fuel for a growing number of nuclear power plant sites. The dry storage of spent fuel in casks has begun to be recognized by more and more utilities as an effective and flexible option for interim storage of spent fuel. The recent trend shows a predominant majority of utilities prefer casks for additional storage options.
The increasing use of casks for spent fuel storage also raises an issue of longer term consideration for the optimisation of the overall operation by standardization of inner containers for accommodating various characteristics of spent fuel as required for compatibility of interface between different stages of the spent fuel management.
In addition to the long experiences accumulated in spent fuel transportation, industrial practice has also been accumulating in the use of casks for storage, both with dedicated or dual purpose ones, in an increasing number of Member States.
The objective of this task is to collect information on the industrial practices or research results associated with the use of cask and containers for spent transportation and storage and, if possible, to identify major issues to be considered for such projects.A first consultancy meeting was held 28-30 October 2002, a Technical Meeting (TM) was held 13-16 October 2003, and a second consultancy meeting was held 24-26 May 2004. The TECDOC was issued in January 2007 as techical document entitled Operation and Maintenance of Spent Fuel Storage and Transportation Casks/Containers (IAEA-TECDOC-1532).
2. Spent fuel treatment
Spent fuel treatment is the key technical component in the back-end of the nuclear fuel cycle which has an important implication for sustainable development of nuclear energy at longer term. As an option for spent fuel management, reprocessing has become a mature industry since several decades and a survey on the status and trend on reprocessing was published as a technical document Status and Trends on Spent Fuel Reprocessing (IAEA-TECDOC-1103, 1999).
In addition to the conventional technologies for separation of fissile materials for recycle into nuclear power reactors, attention is drawn to some advanced or alternative technical concepts which have recently gained growing interest in some Member States in search of potential solutions to future challenge of spent fuel management issues at longer term. In the IAEA context, the INPRO as an international initiative for study on the innovative nuclear power and fuel cycle systems project has been launched with a focused view on emerging technologies.
With a view to update of the previous publication, an Advisory Group Meeting on the Spent Fuel Treatment was held in 2000 followed by a couple of consultancy meetings, from which an updated draft was elaborated with expanded scope of work of including among others an additional section on emerging technologies. TECDOC-1467, Status and Trends in Spent Fuel Reprocessing, was issued in September 2005.
As a follow-on activity to the latter TECDOC, a consultancy was held in December 2004 to plan a technical meeting in the Republic of Korea in October 2005 to exchange views on spent fuel treatment options and applications. This Technical Meeting was held 17-20 October 2005 in Daejeon, Republic of Korea, attended by some 30 participants from 14 countries. The purpose of this meeting was to review technologies for spent fuel treatment options and applications and discuss associated issues with a view to prepare a technical document that could enhance information exchange and knowledge management for Member States.
The results of the October 2005 meeting were reviewed during a consultancy meeting held 2-5 October 2006 and in April 2007 the document was prepared for review by IAEA Publications Committee.
3. Optimization Strategies for Cask Design and Container Loading in Long Term Spent Fuel Storage
Cask designers currently face a number of new challenges including storage of high burnup fuel with correspondingly higher enrichments, the use of MOX fuel, and obtaining regulatory approval for the use of burnup credit. Optimization of cask loading might have different meanings from the views of the cask vendor, the cask owner, the cask operators, the institution having the ultimate responsibility for the storage, the Licensing and Supervisory Authority. Optimization is a part of the design process in which the combination of application objectives, regulatory limits and design margins are innovatively addressed and judiciously balanced in the final design. A primary result of a successful design optimisation is a cask of superior assembly and burnup/age capacity that minimizes the total number of required cask loadings. An equally important and parallel benefit is that this process also results in reduced radiation exposure, thereby contributing significantly to ALARA objectives. In this sense, both cask designers and regulators have the common ultimate goal of improving cask performance, and thus of facilitating the optimisation process.
Spent fuel cask storage.
A Consultancy was held on in November 2002 to identify and discuss issues, and elaborate findings and problem definitions. A Technical Meeting held in March 2003 reviewed the results of the Consultancy and expanded on the main issues, with two working groups focusing on views from both implementers and regulators. Following a consultancy meeting held in June 2004, the technical document on this topic was issued in December 2006 as a technical document Optimization Strategies for Cask Design and Container Loading in Long Term Spent Fuel Storage (IAEA-TECDOC-1523).
4.Technical Co-operation Project on the 'Study of Burnup Credit Technology (BUCT) for Criticality Safety Analysis in NPP Spent Fuel Storage and Transport'
China is at the beginning of an expanding employment of Nuclear Power Reactors. Nevertheless spent fuel storage capacity at the NPPs in operation could soon be exhausted. Moreover the transport distances to the newly to be built away from reactor interim storage facility will be large. Therefore economical solutions are sought which fulfil ALARA criteria. The application of burnup credit is being investigated. To this end a technical co-operation project with the China Institute of Atomic Energy (CIAE) in Beijing was coordinated by the IAEA from 2002 to 2005 involving scientific visits expert missions, equipment procurement, and fellowships.
5. Technical Co-operation Project on 'Spent Fuel Management in Pakistan'
Assistance was requested in 2004 by Pakistan for development of a national system for radioactive waste management including spent fuel storage. An urgent component of the requested assistance was to provide an additional spent fuel storage facility at Kanupp plant, a small CANDU plant built in 1971, where the spent fuel at reactor (AR) pool was projected to overflow within a few years.
From a conclusion drawn from review of the situation at the site, an AFR pool was recommended as an interim storage solution, with a capacity to accommodate spent CANDU fuel arising from the lifetime operation of the Kanupp plant which was recently extended to 2017 (projected 40,000 bundles total).
Actions were taken for the assistance, throughout 2005, including organizing a TC meeting held in July in Bucharest to get the design concept reviewed by international experts appointed by the Agency, which was a good opportunity to identify techncal issues to be resolved. A later visit to AFR pool storage at Bohunice in Slovakia, initiated by the TO, was another occasion to provide solutions to some of the questions pending from the review meeting. While some issues still remain to be resolved before finalizing the design, the AFR facility design incorporates significant improvements with respect to the earlier design.
The design work is reported to be progressing in preparation for licensing construction of the AFR facility.