A problem triggered by a pipe rupture at Bulgaria’s Kozloduy nuclear power plant on 10 May has been given a provisional rating of level 2 on the IAEA’s International Nuclear Event Scale.
A report issued by the Bulgarian nuclear safety authority said that, during a refuelling outage at unit one, a steam generator blowdown pipe ruptured during decontamination of the steam generator’s secondary side. Some of the chemical solution used in the process spilled into the steam generator’s compartment and reached the emergency boron tank, polluting the contents.
It should have been possible to deliver boron solution into the primary circuit and spent fuel pool. However, the safety authority said operational limits and conditions were exceeded because the emergency boron tank was not available.
The cause of the pipe rupture has not yet been identified.