An exact expression for the elastic self energy of a semicircular dislocation loop at free surface is derived based on the elastic continuum dislocation theory.

The results show that dislocation loop groups are the typical dislocation morphologies of the creep deformation structure in the alloy.

The results show that the dislocation loops with b=1/3[111] are vacancy typed, the forming reason is that during the process of plasma nitriding the continuous bombardment of high energy ions lead to the formation of a great deal of point defects vacancies, Some of vacancy flakes are formed by gathering of the vacan.

The results show that the dislocation loops with b=1/3[111] are vacancytyped, the forming reason is that during the pro-cess of plasma nitriding the continuous bombardment of high energy to the formation of a great many point defects-vacancies, go on vacancy flakes are formed by gathering many vacancies, and fin.

A large number of sqaure dislocation loops and helical dipoles have been found.

The simulations showed that dislocation loops emerged in the right and left of the left void,however,dislocation loops emerged only in the right of the right void when the two voids were set along the shock wave in the direction.

The results indicate that dislocation loops nucleate and grow up on the dislocations and other sites in 1# CLAM steel during irradiation.

The results indicate that a lot of voids and dislocation loops form by irradiation.