Davis Besse back on line

Tuesday, 6 December 2011 FirstEnergy's Davis Besse pressurized water reactor has come back to power operation, having had the head of its reactor pressure vessel replaced. The unit was announced as being at 23% power on 6 December and expected to reach its 900 MWe maximum within days. The major maintenance was required after cracking from stress corrosion was discovered last year around the vessel head penetrations where control drive mechanisms rods enter the vessel from above. This discovery prompted FirstEnergy to bring forward a replacement program that had previously been slated for 2014. It contracted Areva to make the new vessel head using "an enhanced material" for the vessel head penetrations that is less susceptible to cracking. The reactor unit received a new control system at the same time.