Modelling of Inert Gas Bubble Behaviour During Annealing of Irradiated Molybdenum

By theoretically studying the gas bubble evolution in Mo doped with heavy inert gas (Xe) a bimodal size distribution in a broad temperature region (1473-1973K) is predicted. For Mo implanted with helium, the size distribution is typical and has only a single peak. A modelling of gas porosity development was carried out using the assumption that the basic mechanism of bubble nucleation and growth is the collision and coalescence of randomly migrating bubbles. An analysis of the calculation results leads to a conclusion that the major cause of the formation of the bimodal size distribution is the existence of a deep bubble mobility minimum for Mo doped with heavy inert gas. The proposed mechanism of bimodal size distribution formation is supported by results obtained by Rest and Birtcher for Ni implanted with heavy inert gases.