Stresses due to pressure and repeated thermal cycling cause progressive material damage during the operation of LWR components and piping systems. Task 1 of Phase II focuses on the resolution of issues related to the proposed elastic-plastic fracture mechanics methods used to include environmental and aging effects in the fatigue life evaluation methods. The revised methodology will then be used to develop new curves for A106 material. An optional Task 2 is also described. It extends the application of the method to include weldments containing code acceptable imperfections and residual stresses. Modifications to the methodology of Task 2 based on the results: of Task 1 will be resolved prior to initiation of Task 2.
Anticipated Results:The evaluation method research product to be developed in this Project will provide a key element of the technical and Code bases for extending the safe useful life of aged LWR plants. The inclusion of environmental effects and weldments in the evaluation method, qualified by hardware operating experience. will give utilities a means of quantifying the safe remaining life of billions of dollars worth of aged nuclear components and piping.
