Absence of voids in fast neutron irradiated zirconium by small angle neutron scattering

Abstract

The aim of this research was to resolve a difference of opinion in the literature on the presence of voids in fast neutron irradiated zirconium. There is a great interest in the study of zirconium, since zirconium and its alloys are used extensively in modern power reactors, for example in the fuel rods as a containment material for enriched uranium. A polycrystalline sample of zirconium was irradiated in the HERALD reactor at 40°C with 10²⁰ fast neutrons per cm^?2. The neutron scattering from irradiated and unirradiated standard samples was studied over a wide Q range from 0.001 to 1.12 Å^?1 on a D11 Spectrometer at the ILL (France). The defect cross-section (the difference between the scattering of the standard zirconium crystal and irradiated crystal) was nearly flat as a function of Q (momentum transfer vector) with an average value of 8.5 mb/Str/atom. This indicates a point defect concentration of about 1.8%. Thus the absence of any small angle (Q dependent) defect scattering indicates that large damage regions (e.g. voids) are not produced in zirconium by fast neutron irradiation.