Cause of drop in pressure in KKP 1 containment dome discovered and resolved

Karlsruhe. Today saw the end of an extensive program of investigation in Block 1 of the Philippsburg nuclear power station (KKP 1), which systematically sought the cause of the drop in pressure in the containment dome that was determined last week.

The cause of the drop in pressure was some measuring pipe connections on the local pressure display in the area of the block's subsidiary gate lock, which had been swapped out during works on the plant. This had resulted in a leak between the containment dome and the void (known as the "Ringspalt") between the containment dome and the metal shell that encloses it. Due to the leak, non-radioactive, nitrogen-containing air was able to penetrate into the Ringspalt.

The leak has been stopped. The operator will analyse this event in detail, using a procedure that has been approved by the regulatory authority, to ascertain how it came about.

The drop in pressure was determined during the restart process after completion of the annual inspection through the operational monitoring that is intended for this purpose, after the containment dome had been filled with nitrogen in accordance with the usual routine. EnBW had already reported this drop in pressure last Friday, the 6th of June 2008.