INFLUENCE OF BORON-GENERATED HELIUM ON THE SWELLING OF NEUTRON-IRRADIATED V, V-5CR AND V-5FE

The effect of He on dimensional stability of V, V-5Cr and V-5Fe alloys has been studied using the B doping technique. The addition of 5 wt% Cr to pure V leads to a significant increase in neutron-induced swelli ng at 600 degrees C, Although the swelling of V-5Cr increases strongly with irradiation temperature, the influence of Cr is reversed at lowe r temperatures, with pure V swelling more than V-5Cr. The use of B add itions to generate relatively large amounts of He in V, V-5Cr and V-5F e leads to a very complex swelling response, depending on the B level and the irradiation temperature. At 520 degrees C, B addition is found to increase the cavity density, However, the most pronounced response occurs in V-5Cr at 600 degrees C, where B levels of 100 appm or great er cause a significant reduction in swelling. The complexity of swelli ng response is thought to result from the competition between He effec ts and the separate chemical effects of B and Li, each of which may ex hibit its own dependence on irradiation temperature.