Oscillating Structure of Thermal Annealing of Radiation Damage revealed by Neutron Diffraction

Abstract

I HAVE reported the fine structure of the isothermal annealing curves of neutron irradiated solid compounds in a series of publications^1–9. The structure was confirmed later by others^10–12. An oscillating structure was always found for the isotherms, irrespective of the chemical constitution of the lattice and the nuclear events which produced the recoil radionuclides. The phenomenon thus seems to be based on some general property of a radiation damaged lattice. I now describe similar annealing behaviour for radiation damage detected physically, using the neutron diffraction method with irradiated single crystals of compounds similar to those studied already by radiochemical means. Tri-ethylenediamine, cobalt nitrate and chloride in the form of single crystals were reactor irradiated for 1 h in a position where the neutron thermal and fast flux were 4.18 × 10¹² and 2.6 × 10¹¹ neutrons cm⁻² s⁻¹ respectively. The absorbed gamma dose was about 30 Mrads. After irradiation the single crystal was oriented to give an intense diffracted neutron beam at the MAN neutron spectrometer of the 1 MW nuclear reactor. The diffraction spectrum for a particular lattice plane was taken before and after reactor irradiation. The maximum was shifted about 0.15 of a degree and the new peak was used to examine the variation in the intensity; the shape of the peak did not change during annealing.