Influence of precipitated hydride on the fracture behavior of zircaloy fuel cladding tube

Ln order to clarify the influence of precipitated hydride on the fracture b ehavior of Zircaloy cladding tubes, the stress-strain distribution of the c ladding was estimated by finite element method (FEM) analysis. The mechanic al properties of a-phase of zirconium and zirconium hydride required for th e analysis were examined by means of an ultrasonic pulse-echo method and a tensile test. It was found from the analysis that the non-hydrided cladding has the highest equivalent plastic strain at the inner surface of the clad ding, suggesting that the fracture initiated at the inner surface of the cl adding. Since the hydride accumulated layer located in the outer surface of the hydrided cladding fails at a lower internal pressure, the crack appear s to initiate at the outer surface of the cladding. The fracture behavior e stimated from the stress states of the hydrided cladding was in good agreem ent with the experimental results obtained by pulse irradiation tests of th e Nuclear Safety Research Reactor (NSRR) and high-pressurization-rate burst tests in the Japan Atomic Energy Research Institute (JAERI).