Routine inspection of the concrete shield building at FirstEnergy Nuclear Operating Company’s (FENOC) Davis-Besse Nuclear Power Station has identified three very tight, subsurface cracks. However, FENOC has confirmed that the building continues to maintain its structural integrity and ability to safely perform its functions.

The inspections, which are being carried out using high-definition camera technology, also found that in three locations, cracks initially identified in 2011 appear to have propagated a small amount.

"The improved camera provides greater clarity and mobility than previously available equipment," FENOC said.

The utility, which operate the 890 MW pressurized water reactor, has inspected 43 of the shield building’s 82 core bores (inspection ports). The remaining inspections are expected to be completed in the next "several weeks," it said.

"Analysis of all inspection results to date confirms the 2011 conclusion that the shield building’s structural integrity is not impacted by the presence of these tight cracks. The robust building continues to function safely and reliably," said Davis-Besse Site Vice President Ray Lieb.

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 reactor.

Photo: Davis-Bess (Source, FENOC)