Combined effects of radiation damage and hydrides on the ductility of Zircaloy-2

• Published in: Nuclear engineering and design 1998-09, Vol.185 (1), p.33-49
• Main Authors: Wisner, S.B., Adamson, R.B.
• Format: Article
• Language: English
• Subjects: Applied sciences; Composition effects; Ductility; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fractography; Hydrides; Hydrogen embrittlement; Installations for energy generation and conversion: thermal and electrical energy; Neutron irradiation; Nuclear reactors; Precipitation (chemical); Radiation damage; Strain rate
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/S0029-5493(98)00155-1

Interest remains high regarding the effects of zirconium hydride precipitates on the ductility of reactor Zircaloy components, particularly in irradiated material. Previous studies have reported that ductility reductions are much greater at room temperature compared to reactor component temperatures. It is often concluded that the effects of irradiation dominate the ductility reduction observed in test specimens, although there is no consensus as to whether hydriding effects are additive. Many of the tests reported in the literature are difficult to interpret due to variations in test specimen geometry and material history. In this paper, we present the results of an experimental program aimed at clearly describing the combined effects of irradiation and hydriding on ductility parameters under conditions of a realistic test specimen design and well characterized hydride content, distribution and orientation. Experiments were conducted at 295 and 605 K, respectively on Zircaloy-2 tubing segments containing 10–800 ppm hydrogen and neutron fluences between 0–9×10 25 n m −2 ( E>1 MeV). Tests utilized the well proven localized ductility specimen which applies plane strain tension in the hoop direction of the tubing segment. In all cases, hydrides were also oriented in the hoop or circumferential direction and were uniformly distributed across the tubing wall. Results indicate that at 605 K, the ductility of irradiated material was almost independent of hydride content, retaining above 4% uniform elongation and 25% reduction in an area for the highest fluences and hydrogen contents. Even at 295 K, measurable ductility was retained for irradiated material with up to 600 ppm hydrogen. In the paper, results of fractographic analyses and strain rate are also discussed. We conclude that at reactor component operating temperatures, radiation damage controls the ductility of Zircaloy-2 for conditions of these tests up to hydride levels of at least 800 ppm, and probably much higher. At room temperature the effect of hydride content and radiation damage appear to be additive.