Department of energy's annealing prototype demonstration projects

One of the challenges utilities face in addressing technical issues associa ted with the aging of nuclear power plants is the long-term effect of plant operation on reactor pressure vessels. These vessels are exposed to neutro ns during the operation of a reactor. For certain plants, this exposure can cause embrittlement of some of the vessel welds, which can shorten the use ful life of the vessel. This reactor pressure vessel embrittlement issue ha s the potential to affect the continued operation of a number of US pressur ized water reactor plants. However, the properties that are degraded by lon g-term irradiation can be recovered through a thermal annealing treatment o f the vessel steel. Although a dozen Russian-designed and several US milita ry vessels have been successfully annealed, US utilities concluded that an annealing demonstration using a US reactor pressure vessel was a prerequisi te before annealing a licensed US nuclear power plant. In May 1995, the Dep artment of Energy and Sandia National Laboratories initiated a program to e valuate the feasibility of annealing US licensed plants using two different heating technologies. One team completed its annealing prototype demonstra tion in July 1996, using an indirect gas-fired furnace at the uncompleted P ublic Service of Indiana's Marble Hill nuclear power plant in southern Indi ana. The second team's annealing prototype demonstration using a direct hea t electrical furnace at the uncompleted Consumers Power Company's nuclear p ower plant at Midland, Michigan, was scheduled to be completed in early 199 7, but has now been delayed indefinitely. This paper describes the Departme nt of Energy's annealing prototype demonstration program and the results to date for each project. (C) 1999 Elsevier Science S.A. All rights reserved.