The Impact of D-- exp 3 He Fusion Reactors on Waste Disposal

The suggestion that the surface of the moon may be mined for exp 3 He to be used as a fuel in terrestrial fusion reactors has recently been made. A fusion reactor based on the D-- exp 3 He reaction would have the advantage that most of the power produced would be in the form of charged non-radioactive particles. However, secondary D--D and D--T reactions also occur. A study is made of the consequences of the radioactivity induced by the neutrons from these reactions with respect to waste disposal. A generic first wall and shield 0.4 m thick consisting of 7% structure, 73% H sub 2 O and 20% void was used as a test case. The structural materials considered were two austenitic stainless steels (PCA and Tenelon), two ferritic alloys (HT-9 and a low activity modification of HT-9), and a vanadium alloy (V15Cr5Ti). The results of the calculations show that, for operation at a fusion power loading of 1 MW/m exp 2 for a 30 year reactor lifetime, Tenelon, the low activity HT-9 and the V alloy meet surface waste disposal requirements consistent with those published in the US Code of Federal Regulations (10CRF61). If 5% boron is added to the water to suppress (n, gamma ) reactions, HT-9 and PCA structures are acceptable. Calculations of a first wall and shield designed for a 600 MW reactor D-- exp 3 He operating at a fusion power loading of 2.94 MW/m exp 2 indicate that Tenelon may be used as structure and meet waste disposal requirements after 30 years of operation. It is concluded that the use of a D-- exp 3 He cycle allows surface burial of activated reactor components and results in a significant reduction in the volume of waste. 11 ref.--AA