The embrittlement of reactor pressure vessel steels is a dynamic process involving the production and removal of crystal defects. Thus, the level of embrittlement is expected to depend on the damage rate, irradiation temperature and time.

A model is being developed at the University of Virginia to predict these processes for irradiation conditions typical of those in research reactors and commercial power reactor pressure vessels. The model assumes that three defect types are responsible for the embrittlement. The rate of production of the defects is dependent upon the neutron flux, but may be stablized by some elements, such as copper and nickel. The annealing of each defect depends on its diffusion rate and time. The model exhibits the proper trends with variations in the irradiation time, temperature and damage rate when compared to experimental data.