Both the intergranular and intragranular segregation of phosphorus may significantly contribute to irradiation embrittlement of reactor pressure vessel steels. The modeling of phosphorus radiation-induced segregation at cylindrical (dislocations), spherical (precipitates and voids) and flat (sample surfaces, grain boundaries) point defect sinks has been carried out in order to compare the kinetics and extent of segregation at various point defect sinks. Dilute Fe-P alloys relevant to model and VVER-440 pressure vessel steels were considered.
It is shown that the time to reach steady state phosphorus concentration near dislocation or precipitate is much less than that near grain boundary. Although the steady state phosphorus concentration near dislocations or precipitates is much less than that near grain boundary, a “fast” phosphorus segregation at these sinks may lead to decreasing the free phosphorus content in the matrix and to reducing its subsequent accumulation on grain boundaries at high densities of internal sinks. A more significant effect on the kinetics of grain boundary phosphorus segregation could be caused by the contribution of precipitates to point defect sink strength.