A 1978 blizzard was the cause of cracks found in the containment building wall of the 913 MWe Davis-Besse nuclear power plant in Ohio.
There was a lack of an exterior weatherproof coating on the shield building, said plant owner FirstEnergy Nuclear Operating Co. (FENOC).
Moisture associated with the blizzard of January 1978 migrated into the concrete, froze and expanded, causing the tight, subsurface cracks in the containment building, FENOC said in its Root Cause Analysis Report. Officials discovered the cracks during a reactor head replacement outage in the fall of 2011.
The report said the cracking occurred following the blizzard’s combination of extreme weather conditions, which included three days of driving rain before a drastic temperature drop and intense winds.
The report also concluded the structural integrity of the shield building remains intact, and the building is able to perform its safety function. FENOC will apply a weatherproof coating to protect the exterior walls, perform additional inspections to verify the cracks have not spread and develop a long-term building monitoring plan.