An incident during refuelling at unit A of British Energy's (BE's) Heysham 1 plant has been given a final rating of level two on the International Nuclear Event Scale (INES).
The incident occurred on 11 March during a routine outage. Following removal of a new fuel assembly, a refuelling machine inserted a plug into a buffer store tube. When the machine tried to move away, the grab failed to disengage from the plug, due to failure of a drive coupling. Part of the plug then dropped into the tube. Refuelling was suspended immediately.
The rating for the incident was upgraded from a provisional rating of level one on grounds of "procedural and safety culture deficiency aspects", according to a report by BE to the IAEA.