On the 10th April 2003 severe damage to fuel assemblies took place during an incident at Unit 2 of Paks nuclear power plant in Hungary. The assemblies were being cleaned in a special tank below the water level of the spent fuel storage pool in order to remove crud buildup. That afternoon, the chemical cleaning of assemblies was completed and the fuel rods were being cooled by circulation of spent fuel storage pool water. The first sign of fuel failure was the detection of some fission gases released from the cleaning tank during that evening. The cleaning tank cover locks were released after midnight and this operation was followed by a sudden increase in activity concentrations. The visual inspection revealed that all 30 fuel assemblies were severely damaged. The first evaluation of the event showed that the severe fuel damage happened due to inadequate coolant circulation within the cleaning tank. The damaged fuel assemblies were removed from the cleaning tank in 2006 and are stored in special canisters in the spent fuel storage pool of the Paks nuclear power plant. The event was reported to the IAEA and classified as a Level 3 (severe) incident on the International Nuclear Event Scale (INES). The IAEA sent an expert review mission to investigate the incident in June 2003. First information on the Paks-2 incidents was provided to the NEA Committee on the Safety of Nuclear Installations (CSNI) in its June 2003 meeting, two months after the incident. At that time the CSNI requested the NEA secretariat to co-ordinate actions with Hungarian and Russian parties aimed at assessing the extent to which possible fuel investigations would benefit the nuclear community while helping to clarify the conditions experienced by the fuel during the incident. As a first step in this direction, a meeting was organised in Budapest on 18 August 2003 under the auspices of the NEA. Visual examinations of the damaged assemblies as well as analyses were presented on that occasion.