Optimized Ring Tensile Test Method and Hydrogen Effect on Mechanical Properties of Zircaloy Cladding in Hoop Direction

Abstract

Data pertaining to the mechanical properties of the fuel cladding in the hoop direction are required for the analysis of high burn-up fuel behavior under reactivity-initiated accident (RIA) conditions. In the present study, by minimizing undesirable effects of friction and bending, the ring tensile test method was optimized to obtain precise data pertaining to the mechanical properties of the fuel cladding in the hoop direction. The optimized specimen has a single gauge section and is stretched using the tooling consisting of two half-mandrels. The gauge section is set on top of a half-mandrel; this arrangement is unique in comparison with other methods. Using the optimized test method, the mechanical properties of the prehydrided Zircaloy-4 cladding in the hoop direction were evaluated as functions of hydrogen concentration and test temperature. When the hydrogen concentration is below 500 ppm, the decrease in ductility due to hydriding is relatively small at all test temperatures. When the hydrogen concentration is above 600 ppm, the ductility in the tests at 300K remarkably decreases due to hydriding, while the hydrogen effect decreases in magnitude in the tests above 473 K.