IAEA ACTIVITIES RELATED TO BURNUP CREDIT

The most common assumption used in criticality safety analysis of spent nuclear fuel from power reactors is that spent fuel has the same reactivity as unburned fuel. This approach is typically known as the \"fresh fuel\" assumption and results in significant conservatism in the calculated value of the system reactivity. Current calculation methods have made possible taking credit for the reactivity reduction associated with fuel burnup, hence reducing the analysis conservatism while maintaining an adequate criticality safety margin. Spent fuel management is a common and costly activity for all operators of nuclear power plants. Implementing burnup credit offers the possibility to reduce fuel cycle costs, given the number of Member States dealing with increased spent fuel quantities and extended durations. In 1997, the IAEA initiated a task to monitor the implementation of burnup credit in spent fuel management systems, to provide a forum to exchange information, to discuss the matter and to gather and disseminate information on the status of national practices of burnup credit (BUC) implementation in Member States. The IAEA started this active program with a meeting in 1997 exploring worldwide interest in using BUC in spent fuel management systems. A second meeting was held in Vienna in 2000 followed by a third meeting in Madrid in 2002 on requirements, practices, and developments in BUC applications. Following recommendations of the Madrid meeting encouraging the IAEA to continue this effort, the Agency held a fourth technical meeting on burnup credit applications in London in 2005. This paper highlights spent fuel management trends and related IAEA activities as context for focusing on the results of the Agency’s meeting held in London in September 2005 to address advances in applications of burnup credit. Sixty participants from 18 countries addressed calculation methodology, validation and criticality safety criteria, procedural compliance with safety criteria, benefits of BUC applications, and regulatory aspects in BUC. This meeting encouraged the Agency to continue its activities on burnup credit, given the number of Member States having to deal with increased spent fuel quantities and extended durations. A fifth major meeting on burnup credit is planned for April 2009.