STUDY OF THE ANNEALING EFFECT ON THE DEFECT STRUCTURE OF NEUTRON IRRADIATED PURE IRON BY THE CLUSTER DYNAMICS METHOD

Abstract

For WWER-1000 reactors, which are the basis of Ukraine's nuclear energy, to date, the possibility of restoring irradiated vessel steel has not been fully studied, in particular, temperature-time annealing regimes have not been developed. This article is devoted to this problem. The effect of annealing on the evolution of defect clusters formed in commercially pure iron C <30 ppm), which was irradiated in a Belgian reactor BR2 at 300 ° C with neutrons with a flux of 1.39 × 10⁻⁷ dpa / s   (9×10¹⁷n/м²/с, E > 1 МеВ) to a dose of 0,026 dpa (1,7 ×10¹⁹n/м², E > 1МеВ), has been studied by cluster dynamics method. The temperature and annealing time varied in the range (300 ⁰С-500 ⁰С) and (2 hours -1 day), respectively. The cluster dynamics master equation was written as a system of ordinary differential equations with respect to the numerical density of isolated vacancies (V) and interstitials (SIA) and their clusters (VC) and (SIAC), assuming that only V and SIA are mobile. Formation energies, migration energies, pre-exponential coefficients for V and SIA, vacancy and interstitial dimers binding energies, V-SIA recombination radius were preliminarily determined from the best coincidence between computer simulation data and experimental data. A conclusion was made about the optimal temperature and duration of annealing to restore the defect structure of neutron irradiated pure iron.