Studies on the inspection methods of small-sized stainless steel tubes for fuel cladding

The cladding tubes for fuel element require more precise dimensions and more integral material than ordinary. Therefore, it is needed to have the practical method to inspect efficiently the dimensions and material integrity of these tubes. As a part of the series of manufacturing study of the fuel rods using UO₂ pellets with stainless steel cladding, we have developed some inspection methods for the tubes. To measure the outside and inside diameters, the airmicrometer apparatus was applied. Eddy current instruments for nondestructive testing were applied to check the material integrity, and moreover, by hydrostatic test at high temperature, the pressure resistant properties of tubes were ascertained for internal and external pressure. This report describes the actually applied methods and the results measured by them. The specimens, the material of which was AISI type 304 L stainless steel and the size of which was 8.56 mm O.D. and 7.50 mm I.D., were supplied by four tube manufacturers. Three of them were Japanese and one was Superior Tube Co. in U.S.A. The results of this investigation have indicated that some Japanese tubes are comparable to the reactor grade tube of Superior Tube Co. (author)