The early stages of void and interstitial loop evolution in pulsed fusion reactors

Abstract

A hierarchy of rate equations describing the concentrations of small voids and interstitial loops is used to analyze the effects of radiation pulsing on the early stages of void and interstitial loop evolution. The number of necessary rate equations for the complete description of the clustering process is found to be dependent upon the irradiation time and is obtained by solving an atom conservation equation. Irradiation environments representative of Magnetic Confinement Fusion Reactors of the tokamak-type, Pulsed Heavy Ion Accelerators and Inertial Confinement Fusion Reactors (ICFR's) are considered in this study. At the same average damage rate, it is shown that the high instantaneous atom displacement rate, such as in Pulsed Accelerators or ICFR's, produces high density void and loop clusters of small average sizes. The implications of point defect clustering under pulsed conditions on void nucleation and the embrittlement of the first wall material are discussed.