The intergranular segregation of P atoms in steel is a major cause of nuclear pressure vessel (NPV) steel embrittlement. In this thesis, we have employed a range of computer simulation techniques to investigate radiation events, which take place in the NPV and their effect on the segregation of P atoms to the grain boundaries (GBs). Radiation events were simulated in a perfect bcc Fe lattice using the classical molecular dynamic technique. We have tested two recently developed interatomic potential models, a the second nearest-neighbour modified embedded atom method (2NN MEAM) and a new EAM potential against a conventional EAM potential for the simulation of displacement cascades. Radiation simulations in the energy range of 0.2–2 keV showed that the ballistic and the annealing phase of the cascade were sensitive to the interatomic potential employed. However, the number of Frenkel pairs produced was predicted to be similar by the three potentials, with slightly fewer for the new EAM potential.