The diffusion of He and the formation of He bubbles in stainless steel, under atomic displacement conditions at room temperature to 600C, were studied theoretically by using standard rate equations. A dissociative mechanism which involved self-interstitial and He replacement was assumed to control the He diffusion and bubble formation. Numerical analysis showed that the temperature dependence of the effective He diffusion coefficient, the number-density and mean bubble radius could be divided into 2 distinct regimes; with a transition at about 300C. The effective He diffusion coefficient, the number-density and the mean bubble radius exhibited a weak temperature dependence in the low-temperature regime, but they changed suddenly with temperature in the high-temperature regime. The results were in qualitative agreement with the results of experimental studies of He diffusion and bubble formation in He-implanted stainless steel. However, the discrepancy between the absolute values of the number-density and the mean bubble radius, for the theoretical and experimental studies, indicated that He diffusion and bubble formation might be controlled by athermal mechanisms in the low-temperature regime.

Diffusion and Agglomeration of Helium in Stainless Steel in the Temperature Range from RT to 600C. C.H.Zhang, K.Q.Chen, Z.Y.Zhu: Nuclear Instruments & Methods in Physics Research B, 2000, 169, 64-71