Nuclear power reactor modifications made at Davis-Besse

6 April 2010-- Modifications to control rod drive mechanism nozzles at the 908 MW Davis-Besse Nuclear Power Station in Ohio began March 12 after several cracks were found in them. The nuclear power plant has been shut down since Feb. 28 for scheduled refueling and maintenance.

A team of 80 contract engineers and technicians are making modifications on 16 of the 69 nozzles on the reactor head. The process involves removing the lower half of each affected nozzle and re-welding the remaining section to provide structural integrity. The contractor team has made similar modifications at other U.S. nuclear power plants.

Following this work, additional evaluation and testing will be conducted on the remaining nozzles. This testing is expected to begin in May and take approximately two weeks. The initial nozzle inspection process included ultrasonic testing, liquid dye penetrant examinations and two separate visual inspections.