EU Clearinghouse on Operational Events for Nuclear Power Plants - International Operational Experience on In-Core Fuel Related Events

A detailed report on fuel related events reported to the IRS database operated by the IAEA has been prepared in the IE-JRC under the European Network on Nuclear Power Plant Operational Experience Feedback (Eu Clearninghouse on NPP OEF) activity. This paper focuses on the main phenomena causing actual or potential fuel failure during in-core operation to identify the remedial actions taken and the significant lessons learned. The use of higher enrichment and higher burnup fuel, mixed cores with assemblies of different designs, more challenging core power management, and shorter outages has derived in the need to carefully consider the performance and safety of the fuel materials and designs under these conditions. A great effort has been put to improve the design and manufacture of the fuel assemblies, which has allowed for a better performance and higher operational margins, in spite of the more demanding operational conditions. The result of these counteracting trends is that fuel performance has improved significantly over the years, but there are still some concerns which need to be addressed, like debris and grid to rod fretting, overpower, and corrosion. The most recurrent causes of fuel related events were design deficiencies and human errors but the improved designs and operational strategies widely spread also as operational experience feedback have demonstrated to be very effective in reducing the frequency of in-core fuel related events. Some of the main phenomena important in the past are no longer a concern. Operational and surveillance practices, like Foreign Material Exclusion, coolant chemistry control, and actions to enhance human performance need to be further enhanced. Systematic inspection of fuel assemblies and close monitoring of the operation would allow to detect potential failures in advance. Additionally fuel design and manufacture shall continue improving to cope in particular with fretting and corrosion. Finally, the exchange of operational experience has demonstrated a fundamental tool to enhance fuel safety.

MARTIN RAMOS Manuel;  NOEL Marc;  BRUYNOOGHE Christiane; 

2010-10-13

WILMINGTON PUBL

JRC58201

0029-5507,