In a report submitted to the Nuclear Regulatory Commission Tuesday, FirstEnergy Nuclear Operating Co. pinned the root cause of shield building cracks at its Davis-Besse nuclear plant on a lack of weatherproofing.
The structural integrity of the Ohio reactor’s shield building, which is not part of its primary containment system, remains intact, according to the root cause evaluation now under review by federal regulators. To protect it, FENOC said the company would add a weatherproof coating, the lack of which allowed moisture from a 1978 blizzard to penetrate the concrete.
“The root cause report concludes that the cracking occurred following the blizzard’s combination of extreme weather conditions, which included three days of driving rain preceding a drastic temperature drop to around 0 degrees Fahrenheit and intense winds throughout the storm,” read a FENOC release.
Crews discovered hairline wall and subsurface cracks in the shield building during a reactor pressure vessel head replacement last fall. Experts from the NRC determined the building was safe, and the 913 megawatt Babcock & Wilcox pressurized water reactor was placed back into service in December.