Routine inspections of the concrete shield building at FirstEnergy Nuclear Operating Co.’s (FENOC) Davis-Besse Nuclear Power Station conducted to date have confirmed that the building continues to maintain its structural integrity and ability to safely perform its functions.
The current inspection incorporates high-definition camera technology for examination inside of the building’s walls through a series of inspection ports – or core bores. The improved camera provides greater clarity and mobility than previously available equipment.
Since the start of the inspection, 43 of the shield building’s 82 core bores have been examined, with the remaining examinations expected to be complete in the next several weeks. The improved camera has identified three very tight, subsurface pre-existing cracks in the building that were not visible with previous inspection technology. These inspections also have found that in three locations, cracks initially identified in 2011 appear to have propagated.
The 2½ -foot thick reinforced concrete shield building provides biological shielding and protection from natural phenomenon including wind and tornados. The building surrounds a 1½-inch carbon steel vessel containing the nuclear reactor.
The initial cracks in the shield building were discovered in October 2011 when the building was opened to install a new reactor head. Extensive analysis conducted at the time determined that the building’s structural integrity was not affected. Subsequently, the shield building was painted with a protective coating, and a long-term inspection program was established to ensure continued safe function of the building.