news blog from Marianela

UPDATE 1-FirstEnergy finds cracks at Ohio nuclear reactor

* Cracks not like Progress Florida Crystal River reactorBy Scott DiSavinoNEW YORK, Oct 17 (Reuters) - FirstEnergy has discovered small cracks in a concrete shield building at the Davis-Besse nuclear power plant in Ohio, which was shut for a reactor vessel head replacement, a spokesman for the Ohio-based energy company said Monday.”We don’t believe there will be a problem with the schedule to replace the vessel head. Engineers are conducting a thorough investigation of the cracks. We should have an answer later this week,” FirstEnergy spokesman Todd Schneider told Reuters.The cracks were minor and there was no chance of radiation leakage, FirstEnergy said. Also, fuel had been removed from the reactor as the company prepared to replace vessel head.Schneider was quick to point out that the cracks were different than the concrete problems with the containment dome at Progress Energy’s Crystal River nuclear plant in Florida, which shut in September 2009.At Crystal River, workers discovered a gap in the concrete containment dome while working to replace the steam generators. The plant is not expected to return until at least 2014.FirstEnergy discovered the cracks about a week ago and the NRC sent a concrete expert to join other NRC personnel that were already overseeing the vessel head replacement, said U.S. Nuclear Regulatory Commission spokeswoman Viktoria Mitlyng.She said the NRC would review any findings FirstEnergy’s engineers come up with.The “microcracks” at 879-megawatt Davis-Besse were barely visible, said Schneider. They were discovered while workers were cutting away the concrete with pressurized water to access the vessel head.The shield building is a 250-foot (76.2 meters) tall structure and has two-and-a-half-foot thick concrete surrounding a steel containment structure. The steel containment surrounds the pressurized water reactor’s vessel and steam generators and is designed to keep radioactive materials within the reactor in case of an accident.Davis-Besse is in Oak Harbor about 120 miles (193 km) north of Columbus, the state capital, and can generate enough power for more than 800,000 Ohio homes.THIRD VESSEL HEADThis is Davis-Besse’s third reactor vessel head.Schneider said the discovery of the cracks has not impacted the work schedule but he could not say when the reactor was expected to return to service. He did note the outage was expected to last longer than a typical refueling outage.The reactor shut on Oct. 1. A typical refuel lasts about four weeks. Electricity traders guessed Davis-Besse would return after about six weeks in the middle of November.The company was moving forward with the head replacement work, Schneider said. It will next cut the steel reinforcement bars that support the concrete in the shield building before cutting through the inner steel containment structure.The concrete shield building and steel containment structure, which are separated by at least a few feet, do not have doors big enough for the reactor vessel head, which is nearly 17 feet in diameter and weighs more than 82 tons (74,389 kilograms), FirstEnergy said.It cost FirstEnergy about $600 million to replace the first vessel head ($300 million) and buy replacement power ($300 million) after workers in 2002 discovered borated water, which acts as the reactor coolant, leaked from a control rod drive mechanism and ate a six inch hole in the first vessel head. The plant did not return to service until 2004.In 2010 during a scheduled refueling outage, the company found small cracks in the control rod nozzles and decided to replace the second vessel head. Schneider said this head replacement project would cost about $115 million.