Effects of Zr-hydride distribution of irradiated Zircaloy-3 cladding in RIA-simulating pellet-clad mechanical interaction testing

• Published in: Nuclear engineering and technology pp. 246 - 252
• Main Authors: Per Magnusson, Anna-Maria Alvarez Holston, Katja Ammon, Guido Ledergerber, Marcus Nilsson, David Schrire, Klaus Nissen, Jonathan Wright
• Format: Journal Article
• Language: English
• Published: 한국원자력학회 01.03.2018
• Subjects: 원자력공학
• ISSN: 1738-5733; 2234-358X

A series of simulated reactivity-initiated accident (RIA) tests on irradiated fully recrystallized boilingwater reactor Zircaloy-2 cladding has been performed by means of the expansion-due-to-compression(EDC) test method. The EDC method reproduces fuel pelleteclad mechanical interaction (PCMI) conditionsfor the cladding during RIA transients with respect to temperature and loading rates by out-of-pilemechanical testing. The tested materials had a large variation in burnup and hydrogen content (up to907 wppm). The results of the EDC tests showed variation in the PCMI resistance of claddings withsimilar burnup and hydrogen content, making it difficult to clearly identify ductile-to-brittle transitiontemperatures. The EDC-tested samples of the present and previous work were investigated by lightoptical and scanning electron microscopy to study the influence of factors such as azimuthal variation ofthe Zr-hydrides and the presence of hydride rims and radially oriented hydrides. Two main characteristicswere identified in samples with low ductility with respect to hydrogen content and test temperature:hydride rims and radial hydrides at the cladding outer surface. Crack propagation and failuremodes were also studied, showing two general modes of crack propagation depending on distributionand amount of radially oriented hydrides. It was concluded that the PCMI resistance of irradiatedcladding under normal conditions with homogenously distributed circumferential hydrides is high, withgood margin to the RIA failure limits. To further improve safety, focus should be on conditions causingnonfavorable hydride distribution, such as hydride reorientation and formation of hydride blisters at thecladding outer surface. KCI Citation Count: 0