ACTYS-1-GO: A faster and accurate algorithm for multipoint nuclear activation calculations

This article reports a relatively fast and accurate algorithm to solve large sized nuclear activation problems in one single run. The present algorithm reads material definition and neutron flux spectra generated by transport codes for complex geometries and then performs activation calculation based on the common parameters of the problem. The mathematical and computational details of simultaneous multipoint activation problem are presented along with the solution strategies. The present algorithm speeds up such calculations by generating a common coefficient matrix for a compact subset of the problem, depending upon one or more radiological results expected from the analysis and then removing the sparsity of the cross-section matrix. The algorithm is implemented in a computer code named 'ACTYS-1-GO'. All the above steps and the implementation details are summarized in this article. A detailed validation of the code is also presented. Computational performance comparison for fusion-relevant problems has been carried out with the sequential use of activation code FISPACT and 'Fornax' module of Attila computer code.