JSIR2S code system for delayed radiation field calculations

The JSIR2S is a decay radiation field calculation Python based code coupling a modified version of a Monte Carlo particle transport code MCNP v6.1, isotopic inventory activation and transmutation code FISPACT-II and a code for beta decay electron and positron emission spectra calculations BetaShape. The code works by superimposing a rectangular mesh over problem geometry and implements a so-called cell-under-voxel approach, where inventory calculations are treated separately for each cell of the superimposed mesh voxel. Secondary radiation fields of all the delayed particles included in the FISPACT-II calculations can be calculated. Secondary particle emission spectra are characterized by continuous spectra for electrons and positrons from β decay, and exact line spectra for other particles and reactions. An application of the JSIR2S code to the ITER computational shutdown dose rate benchmark is presented and calculated shutdown dose rates compared with other R2S and D1S based systems. The shutdown dose rates are in good agreement.