New Approach to Neutron-Induced Transmutation, Radioactivity and Afterheat Calculations and Its Application to Fusion Reactors

抄録

A new method and an accompanying computer code CINAC have been developed for the calculation of neutron-induced transmutation, radioactivity and afterheat. In the method, the generation and depletion of nuclides during and after reactor operation are described in a matrix form in which the arrangement of nuclides is determined systematically. The solutions are obtained by an eigenvalue analysis of the matrix without any time steps or iterative schemes which would increase the computational time. The method can treat any type of activation chains equally, and it gives analytical solutions for linear chains. The CINAC code, coupled with the radiation transport codes ANISN and DOT3.5, can also calculate the dose distribution at any time after shutdown in a one- or two-dimensional geometry of fusion reactors. Two calculations were carried out using CINAC to confirm its validity. The results were compared to those calculated by the THIDA code system which is based on a matrix exponential method. The new method was 50 times faster than the latter, while the discrepancy between them was 4% at the most.