6 May (NucNet): An incident in the reactor hall of unit 4 of Hungary’s Paks nuclear power plant during a refuelling outage has been provisionally rated as level 2 on the International Nuclear Events Scale (INES).
Staff were evacuated from the reactor hall after the incident on 4 May 2009 as a precautionary measure. However, none of the staff were exposed to radiation in excess of the daily permitted limit and there was no external release.
The incident occurred when a self-powered neutron detector (SPND) was being transported from the reactor to the high-activity waste storage pit. A wire rope that was attached to the grab carrying the SPND broke inside the four-metre long tubular bio-shield in which the SPND was enclosed.
The SPND and grab fell onto the working area below, which was covered with protective material. As a result of the fall, the bio-shield container bent and tilted onto the decontamination tank for control-rod drivers. There was no damage to other equipment.
However, the incident led to increased radiation in the reactor hall. The dose rate measured at one metre from the SPND container tube exceeded 50 millisieverts per hour (mSv/h) and the incident area in the reactor hall was cordoned off.
NucNet has confirmed that the SPND has since been transferred to the service pool of an adjacent unit where it will remain until final disposal. Outage works at unit 4 have resumed and are proceeding as scheduled.
- by John Shepherd
>>Related reports in the NucNet database (available to subscribers)
Hungary’s Paks Plant Reports Increased Nuclear Generation (World Nuclear Review No. 10, 7 March 2008)
Hungary’s Parliament Paves Way To Build New Reactor Unit (News No. 33, 31 March 2009)