The original basis for closing the nuclear fuel cycle was reprocessing with the recycling of separated plutonium in fast reactors. To date the use of fast reactors has been limited and a complete recycled nuclear energy sustainability using this technology remains a long term goal. For a number of countries, an alternative fuel cycle based solely on the use of thermal reactors and the direct disposal of their spent fuel in a deep geological repository has been adopted (open cycle), while other countries keep the fuel cycle option open to be implemented in the future.

Currently, there are no operating disposal facilities for spent fuel and there is also limited reprocessing capability worldwide, resulting both in spent fuel accumulating in storage facilities and storage periods being extended (in some cases) beyond the originally designated time frame. This, however, requires ensuring that the safety functions are still met, that the knowledge of the condition and behaviour of the spent fuel and systems, structures and components (SSCs) of storage systems is maintained and that capabilities to design, monitor, mitigate and replace storage systems are developed and sustained over several decades.

The main objective of this Coordinated Research Project (CRP) was to support and share improvements in the nuclear power community’s technical basis for LWR spent fuel management licences as dry storage durations extend. This included considering the “gap analysis” performed in some countries to identify gaps in existing knowledge with relation to long term storage and transportation of spent fuel. The technical areas addressed within this CRP were mainly related to: (1) potential degradation mechanisms in metal casks and concrete overpacks like stress corrosion cracking, (2) long term integrity and performance of the fuel cladding, (3) thermo-mechanical behaviour of the metal seals in the long term, (4) long term gamma and neutron shielding capability and (5) review of past and ongoing Demonstration Programmes.

A major achievement of this CRP was the establishment of a worldwide network of experts working on research projects to demonstrate the long term performance of spent fuel in dry storage systems. For each technical topic addressed in this CRP, main conclusions have been drawn, including information on the development of specific monitoring and inspection techniques as well as future opportunities for closing relevant data gaps. The studies conducted during this CRP were performed over relatively short periods of time as compared to actual spent fuel storage durations, but the demonstration tests allowed conclusions drawn from small scale tests to be validated.

This CRP has also contributed to the transfer of knowledge to other parties including countries new to nuclear power. The work performed has provided data to partially close many of the data gaps identified. At the same time, scientific and engineering efforts should be continued to increase the body of knowledge under the established international framework.

Researchers from Argentina, France, Germany, Japan, Lithuania, Pakistan, Poland, Slovenia, Spain, the UK and the USA participated in this CRP.

The results of the four-year CRP will be published in an IAEA TECDOC.

For more information, please see the CRP description:

http://www.urlse.cn/projects/crp/t13014

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