On 26 October 2013 NRG reports that the of concentration Uranium-235 in one of the liquid waste tanks in the Molybdenum Production Facility (MPF) appears to be higher than allowed according to the license. Therefore, a criticality incident could not be excluded. The MPF has twelve storage tanks for liquid uranium-containing waste: six for highly radioactive waste and six for waste with a lower activity. The waste is temporarily stored in the tanks awaiting transport to the Dutch processor of radioactive waste, COVRA. After discovery of the deviation in the Uranium-235 content, NRG has suspended all activities in the facility. Further analysis afterwards showed that although the amount of Uranium-235 in the tank was higher than expected, it was within the limits of the license, so safety with regard to criticality was ensured.
NRG has performed an in-depth root-cause analysis of the deviation. This showed deficiencies in the sampling and analysis procedure of the composition of the waste and the residue in the tanks. It also showed that the risk of criticality was insufficiently covered by risk assessments and measures and that the consequences of deviations from normal operations were insufficiently taken into account.
NRG has taken measures to prevent reoccurrence of the event. Also NRG has started cleaning all waste tanks before they are put into use again. Furthermore, NRG has initiated a large scale improvement program on technology, safety systems and the organization. On 19 April 2014 NRG has resumed operation on the first of the two production lines of the MPF.
Location: Molybdenum Production Facility / Petten Event date: Sat, 26-10-2013