Activation Analysis for the Cavity of the PROMETHEUS ICF Design

Activation analysis for the cavity of the PROMETHEUS ICF design, which uses a wetted first wall protection scheme, has been performed. It has been found that the PROMETHEUS cavity produces about 0.9 Ci/W of thermal power at shutdown after the full 30 years operation, which is about the same amount of radioactivity of other ICF and MCF fusion designs with low activation materials. It was possible, however, to reduce the radioactivity inventory level in the shield by one to three orders of magnitude by introducing a new shield design that uses B₄C, Pb, SiC and water instead of using the conventional concrete shield. Furthermore, the effect of using the spherical and cylindrical modeling on the prediction of radioactivity in the first wall has been studied. It has been found that the cylindrical model with a point neutron source at the center of the cylinder reduces the radioactivity of the short half-life products to about 80% of the values that would be obtained by using purely spherical modeling. Finally, the ²¹⁰Po problem associated with the use of lead has been analyzed. It is shown that ²¹⁰Po produced from neutron interactions with lead is more important than that produced from the bismuth impurity (40ppm) existing in lead if the machine is operated over ∼1 year.