Alternate weld repair technique for nuclear reactor components

The need to make in-service weld repairs on a nuclear reactor pressure vessel may arise in future years. This possibility may develop as a result of radiation-induced loss of fracture toughness in the pressure vessel material and/or service-induced fatigue crack growth of existing flaws. At present an ASME Code acceptable procedure - the half bead technique - exists for making such a weld repair without the use of a post-weld heat treatment (stress relief). In practice, however, this technique may not meet expectations based on theory alone. In response to this need, a research program has been initiated to investigate weld repair for reactor pressure vessels and, as its primary objectives, will define an alternative repair procedure that will be superior to the half bead technique with regard to ease of implementation and service suitability of the resulting repair, obtain quantitative data on the material properties and residual stress distribution of repair welds made with both the half bead technique and the alternative (new) procedure and compare the service suitability of weld repairs made with the two techniques in heavy section steel reactor pressure vessel nozzles. Progress towards achieving each of these objectives will be reviewed. (author)