Put recent experience to work in nuclear welding repairs

The winding down of US nuclear-plant construction for what may well be the rest of this century has been accompanied by an inevitable upsurge in the maintenance effort needed for existing and soon-to-appear nuclear units. There are several distinct areas of interest here for nuclear piping. Intergranular stress-corrosion cracking (IGSCC) in boiling-water reactor (BWR) plants is one highly visible example. Ordinary wear and tear on piping and valves, however, brings serious problems in nuclear power plants. This is because of environmental constraints, with heat and radiation calling for attention, and also because of close clearances, heat-treating requirements, inspection needs, and cleanliness demands for piping interior surfaces. Often, a balance must be struck between theoretical desired conditions and the realities of power generation. The reduction in the required number of snubbers and restraints on piping in the past few years is an example of this. Sometimes, however, it is a better understanding of actual need that leads to the loosening of restrictions. The new welding repairs to piping may be examples of this. New tools, new techniques, and new analyses are all helping to reduce nuclear-plant maintenance costs, keep availability high, and in some cases even make continued operation of the units possible. The recent American Welding Society conference in Knoxville, Tennessee, on maintenance welding in nuclear plants provided a broad range of state-of-the-art technology in the field, plus indications of what is needed or can be expected in the immediate future