Safe long term operation of water moderated reactors: The need to index, integrate and implement existing international databases

In response to an increasing number of nuclear installations pursuing extended operations beyond their initial design life, the IAEA recently initiated an Extrabudgetary Programme on Safety Aspects of Long Term Operation of Water-Moderated Reactors (SALTO EBP) to assist Member States to reconcile related processes, establish a general framework and provide a forum to develop international consensus on long term operation (LTO). The IAEA Programme and the paper address periodic safety reviews (PSR) and different approaches to ensuring adequate safety margins, regulatory approaches for LTO, balancing power uprates versus maintaining safety margins, and the need to address the monitoring, mitigation, replacement and ageing management programmes of active and passive systems, structures and components. The SALTO EBP addresses concepts such as life cycle management, obsolescence management, preconditions for LTO, ageing management, life extension and licence renewal under the rubric of 'long term operation'. Mandated to look for cross-cutting LTO similarities, the SALTO EBP is divided into four Working Groups with a focus on indexing, integrating and implementing the great wealth of existing international databases to ultimately create a 'living' guidance document, regularly updated with new lessons learned from all Member States to ensure that major safety issues are addressed. One such database, now being revised and expanded to a relational database format, is the Generic Ageing Lessons Learned (GALL) Report that catalogues plant structures and components; lists the materials, environments, ageing effects and mechanisms; and documents Nuclear Regulatory Commission evaluation of existing plant programmes that can mitigate or manage these ageing effects. With continuing long term support, this Programme can create an International GALL (IGALL) database that Member States can use to evaluate the safety of nuclear plant LTO. Due to the variability of Member States laws and regulations, IGALL may be supplemented by national or regional documents that address specific regulatory environments. (author)