On 19 February 2013 NRG reports the discovery of a deficiency in the safety evaluation of the primary reactor drain line of the High Flux Reactor (HFR). It was found that the possible failure of the primary drain line of the reactor was not considered in this safety analysis.
In the event of rupture of the primary drain line the resulting leakage rate exceeds the rate covered by the safety analyses. Uncontrollable draining of the reactor vessel might occur and subsequent fuel damage within 30 minutes can not be excluded. Due to the omission in the safety analyses no safety provisions were defined and implemented to prevent this.
Since the reactor was already in shut down condition when the omission was detected, no immediate actions were required. NRG has since modified the lay out and technical provisions related to the primary drain line. This has resulted in the reduction of the possible leak rate in case of pipe rupture. The pipe rupture scenario is now covered by the safety analyses.
Event date: Tue, 19-02-2013