Davis Besse reactor head nozzle modifications complete

Oak Harbor, Ohio, June 4, 2010 — Davis-Besse Nuclear Power Station officials told the Nuclear Regulatory Commission that modifications to the reactor head control rod drive mechanism nozzles are complete and the plant will be ready to return to operations in July.

Modifications of 24 of the 69 nozzles having small cracks were completed during the past two months using methods including robotic welding.

The flaws were identified during a comprehensive inspection of the reactor head as part of a scheduled refueling outage that began February 28, 2010.

Davis-Besse nuclear power plant has been operating since 2004 with an unused, replacement reactor head obtained from a cancelled Midland, Michigan, plant.

An extensive investigation by Davis-Besse plant engineers indicated that elevated reactor head temperatures accelerated the cracking of the nozzle material.

This material is known industry-wide to be more susceptible to stress cracking. To impede future nozzle cracking, plant operators will lower the temperature of the reactor core by reconfiguring the fuel assemblies and shorten the next operating cycle.

During the planned 2012 outage, the nozzles will undergo more intensive inspections and testing. A new reactor head, with nozzles made of a different alloy that is less susceptible to cracking, will be installed in 2014.

Work activities scheduled to be completed before restart include: reassembly of the reactor head components, reload fuel assemblies and other restart readiness testing.

The NRC Special Inspection Team continues to monitor activities related to the nozzle modifications.

Davis-Besse is part of FirstEnergy Nuclear Operating Company (FENOC), a subsidiary of Akron, Ohio-based FirstEnergy Corp.

 

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