It was recalled that neutron irradiation damage in zirconium alloys consisted mainly of a high density of small prismatic dislocation loops. During post-irradiation heat treatment, thermal annealing of loops occurred. This phenomenon was investigated by transmission electron microscopy and microhardness tests. It was shown that the loop density decreased while their mean size increases. Furthermore it was demonstrated that only vacancy loops remained in the material after long-term annealing at high temperatures. A mechanism based upon vacancy diffusion was proposed to explain the loop evolution during annealing. A cluster dynamic model, originally developed to compute the evolution of the microstructure under irradiation, was adapted to the modelling of the annealing for zirconium alloys. This physically based model reproduces the loop size and density evolution during a large variety of heat treatments and also provides a better understanding of the mechanisms involved in the loop recovery.

Experimental Study and Numerical Modelling of the Irradiation Damage Recovery in Zirconium Alloys. J.Ribis, F.Onimus, J.L.Béchade, S.Doriot, A.Barbu, C.Cappelaere, C.Lemaignan: Journal of Nuclear Materials, 2010, 403[1-3], 135-46