New Techniques for the Testing of Cladding Material under RIA Conditions

Two new mechanical tests, rapid heating and loading (RHL) and modified burst, have been developed to evaluate cladding properties under RIA heating and loading conditions. The RHL test was designed to evaluate cladding ductility changes due to temperature increases during a RIA. A series of RHL tests were conducted using pre-hydrided and irradiated cladding. The test samples were heated to different target temperatures from ambient to 350oC and simultaneously loaded to failure within 70 ms. Both non-irradiated and irradiated material test results conclusively show ductility is immediately recovered as the temperature is increased. A brittle-toductile transition, between 75oC and 100oC, was observed for both non- and irradiated Zircaloy-2 materials. The instantaneous ductility recovery also suggests that rapid heating should not be required in the evaluation of ductility degradation due to hydrides under RIA loading conditions. A modified burst test was developed to mechanical simulate the loading conditions of a RIA. The test uses a driver tube with a gauge section and loading is provided via a piston/cylinder arrangement which allow for greater control of the sample deformation. The configuration allows for total control of the pressure pulse duration as well as desired diameter deformation. A number of tests have been conducted using cold-worked, cold-worked and hydrogen charged, and irradiated cladding material. The test results verify ductility recovery as observed in the RHL test and post-test measured plastic strain at failure is comparable and consistent with NSRR test results at ambient and elevated temperatures. (author)