Study of metastable states of the precipitates in reactor steels under neutron irradiation

The Lifshitz - Slezov theory is applied to study the metastable statesof the matrix damage clusters, MDs, and the copper enriched clusters, CECs, in neutron irradiated steels. It was found that under irradiation conditions the CECs are at the Ostwald stage for a neutron fluence of about 0.0002 dpa. The time dependence of number density, MDN, is determined by summarizing all differential equations of the master equation for MDs with neglecting of dimmers concentration in comparison with concentration of the single vacancies and subtraction of the number CECs that replace the MDs, namely vacancy clusters, due to the diffusivity of copper and other impurity atoms to them. For binary Fe-0.3wt%Cu under neutron irradiation with dose 0.026, 0.051, 0.10 and 0.19 dpa the volume content of the precipitates from the SANS experiment is found to be about 0.229, 0.280, 0.237 and 0.300 vol% respectively. The volume fraction of CECs in these samples is 0.195 vol% and the calculated volume fraction of MDs is 0.034, 0.085, 0.042 and 0.105 vol% for doses 0.026, 0.051, 0.10 and 0.19 dpa respectively.