Germany German regulators have recommended to the Reactor Safety Commission (RSK) that the primary piping systems in all German BWRs be examined in detail for signs of damage from hydrogen explosions after it had been discovered that Brunsbüttel had probably suffered from an explosion at least 10 years ago, which has gone undetected until now.

Brunsbüttel has been shut since March of this year after a hydrogen explosion was found to have ruptured a pipe last December (see NEI July 2002, p4) in an auxiliary primary cooling system. Experts that have been investigating the incident have since located a bulge in another pipe in the same system.

The two situations (one explosion, and one suspected explosion) both affect piping filled with primary steam at ambient conditions in a spray system which injects coolant into the top of the core during shutdown. The bulge was found in a section somewhat lower down than last December’s explosion, which was close to the top of the vessel. There is a “very strong suspicion” that the bulge was also caused by a hydrogen explosion.

The bulge was discovered only after the piping system had been thoroughly inspected following orders from the Ministry of Finance and Energy (MFE). The MFE had ordered the unit to be shut down for checks, and as a result, had found the ruptured pipe less than 3m from the pressure vessel.