Measurement of residual stress in fuel cladding tubes by x-ray method

It is difficult to predict the residual stress distribution in FBR or LWR fuel cladding tubes using computer code or mechanical methods. In order to measure these stresses by X-ray method, the characterization of X-ray diffraction and optimum condition for stress measurement are investigated. Following conclusions are obtained: (1) The (211) CrK_α and (213^-3) CuK_α reflections are most suitable for the stress analysis of 316 stainless steel and Zircaloy-2 fuel cladding tubes, respectively. (2) Comparison between strain measured by X-ray and strain measured by strain gage shows good agreement in elastic region for both materials. (3) In order to obtain accurate results, it needs to remove surface more than 3 μm by electropolishing or acid etching. (4) There exists compressive residual stress in typical FBR fuel cladding tubes, and TIG welding of end plug induces additional compressive stress in welded portion or heat affected zone. (5) Residual stress distributions in Zircaloy-2 cladding tube deformed locally by the out-of-pile simulation tests, are obtained by the application of X-ray method. (author)