3. DESCRIPTION
During a fuel crud removal operation on the Paks-2 unit on 10 April 2003 several fuel assemblies were severely damaged. The assemblies were being cleaned in a special tank of the Paks Nuclear Power Plant, Hungary under deep water level in a service pit connected to the spent fuel storage pool. The first sign of fuel failures was the detection of some fission gases released from the cleaning tank. Later visual inspection revealed that most of the thirty fuel assemblies suffered heavy oxidation and fragmentation. The first evaluation of the event showed that the severe fuel damage happened due to inadequate cooling.
The Paks-2 event was discussed in various committees of the OECD Nuclear Energy Agency (OECD/NEA) and of the International Atomic Energy Agency (IAEA). Recommendations were made to undertake actions to improve the understanding of the incident sequence and of the consequence this had on the fuel. It was considered that the Paks-2 event may constitute a useful case for a comparative exercise on safety codes, in particular for models devised to predict fuel damage and potential releases under abnormal cooling conditions and the analyses on the Paks-2 event may provide information which is relevant for in-reactor and spent fuel storage safety evaluations.
The OECD-IAEA Paks Fuel Project was established in 2005 as a joint project between the IAEA and the OECD/NEA. The IAEA provided financial support to the operating agent (Hungarian Academy of Sciences KFKI Atomic Energy Research Institute (AEKI)) and reviewed the progress of the project within the framework of the TC Project, RER9076 "Strengthening Safety and Reliability of Fuel and Material in Nuclear Power Plants".
Thirty organizations from sixteen countries participated in the project. The following participants performed analyses of the event using numerical models based on a common database:
AEKI (Hungary)
BME NTI (Hungary)
GRS (Germany)
IRSN (France)
IVS (Inzinierska vypoctova spolocnost ) (Slovak Republic)
Kurchatov Institute (Russian Federation),
SUEZ - TRACTEBEL ENGINEERING (Belgium)
US NRC (United States of America)
VEIKI (Hungary)
VTT (Finland)
VUJE (Slovak Republic)
