The irradiation effects on zirconium alloys Gh. Negut a, * , M. Ancuta a , V. Radu a , S. Ionescu a , V. Stefan a , O. Uta a , I. Prisecaru b , N. Danila b a Institute for Nuclear Research Pitesti, Campului Str., 1, Mioveni P.O. Box 78, 0300 Pitesti, Romania b University Politehnica Bucharest, Bucharest, Romania Abstract Pressure tube samples were irradiated under helium atmosphere in the TRIGA Steady State Research and Material Test Reactor of the Romanian Institute for Nuclear Research (INR). These samples are made of the Zr–2.5%Nb alloy used as structural material for the CANDU Romanian power reactors. After irradiation, mechanical tests were performed in the Post Irradiation Examination Laboratory (PIEL) to study the influence of irradiation on zirconium alloys mechanical behaviour. The tensile test results were used for structural integrity assessment. Results of the tests are presented. The paper presents, also, pressure tube structural integrity assessment. Ó 2007 Elsevier B.V. All rights reserved. PACS: 28.20.Fc; 28.41.Qb; 28.50.Dr; 46.50.+a; 61.80.Lj; 62.20.Fe; 62.20.Mk; 68.35.Gy 1. Introduction The reactor irradiation of zirconium alloys leads to degradation of their mechanical properties as a result of fast neutron action. Any irradiation induced defect isolated in the lattice, which does not adhere to the dislocation loops, influences mac- roscopic dimensional parameters, e.g. material form and volume changes. The observation of dimen- sional changes of the Cernavoda CANDU fuel channels and their pressure tubes as well as the detection of defects induced during normal opera- tion were performed by in-service inspection accord- ing to Canadian standards [1,2]. During the last planned outage [3,4], an inspection of Cernavoda NPP Unit 1 was performed for the following purposes: (a) pressure tube inside diameter measurements, (b) gap between pressure tube and calandria tube measurements, (c) tube sagging measurements, (d) fuel channels elongation, (e) pressure tubes defects detection and charac- terization. In service inspections in some Canadian reactors reveal the following types of flaws after periods of operation [5–7]: (1) scratches due to fuel bundles, (2) pitting corrosion, 0022-3115/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2007.01.160 * Corresponding author. Tel.: +40 248 213400; fax: +40 248 262449. E-mail address: joenegut@yahoo.com (Gh. Negut). Journal of Nuclear Materials 362 (2007) 300–308 www.elsevier.com/locate/jnucmat