Radiation damage in magnesium oxide. I. Dose dependence of reactor damage

The kinetics of saturation of F + centre production have been studied in MgO after reactor irradiation. Although both vacancy and interstitial clusters are formed at high neutron dose, saturation does not result from clustering but is more probably caused by spontaneous recombination of vacancies and interstitials when these are separated by less than 18 nearest-neighbour distances. The production of interstitials and vacancies during irradiation results in growth of both the macroscopic and unit-cell dimensions of the crystals. Comparison of these changes suggest that below about 3*10 19 nvt Frenkel defects are formed. At the lowest doses (<3*10 17 nvt) the mean dilatation per Frenkel pair is estimated to be approximately 8 atomic volumes. At high doses (about 3*10 19 nvt) Frenkel defects migrate to form interstitial clusters. Since this corresponds to the conversion of Frenkel defects to Schottky defects, the mean dilatation per interstitial decreases from approximately nine atomic volumes to one atomic volume.