Diffusion of deuterium in Zr-2.5Nb alloy under neutron irradiation

Pressure tubes of cold-worked Zr-2.5Nb (Zr-2.5 wt% Nb) material are used in the core of CANDU (R)(1) reactors to contain the fuel bundles and the heavy water (D(2)O) heat transport fluid. Deuterium diffusion in unirradiated Zr-2.5Nb pressure tube material has been measured both in and out of neutron flux to determine the magnitude of any irradiation effects. The measurements were carried out at about 530 and 580 K using the U-2 Loop of NRU reactor at the Chalk River Laboratories. The results show that deuterium diffusion in Zr-2.5Nb pressure tube material during irradiation at a fast neutron flux of similar to 5 x 10(17) nm (2)s (1) is not significantly different from that measured in the absence of neutron flux. This supports the use of deuterium diffusivities determined from out-reactor tests for modeling deuterium mobility in unirradiated pressure tubes and other reactor core components made from zirconium alloys. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.