The behaviour of control rod absorber under irradiation

Increase of rod diameters and cracking of PWR control rod claddings may occ ur in operation. Ln order to understand the contribution of the absorber pr operties to this damage, EDF and FRAMATOME launched a programme of examinat ions concerning the silver-indium-cadmium alloy constituting the absorber b ars. Density measurements and microstructural investigations such as microg raphy, microanalysis were carried out in the EDF Hot Laboratory, Xray diffr action was performed by CEA. The results show that transmutations induce ch emical modifications inside the fee alloy and, further, formation of an hcp phase similar to the zeta phase of the silver alloys. The chemical and cry stallographic changes account for the major part of the absorber swelling. (C) 1999 Elsevier Science B.V. All rights reserved.