Development of Radiation Sources for Nuclear Analysis Beyond ITER Bio-Shield: SRC-UNED Code

ITER reference MCNP models are the portentous result of years of geometric modelling, and they share the bio-shield as the natural boundary for practical reasons. Models representing the Tokamak, or fractions of it, end in the bio-shield. Those representing the Tokamak Complex start in the bio-shield. Nuclear analysis beyond the bio-shield is of high relevance to forecast radiation conditions for electrical and electronic equipment, as well as for human intervention, affecting both economics and safety. Nevertheless, it presents a challenge when dealing with the plasma radiation source: the radiation source is not contained in the MCNP model under study. Coupling both simulations inside and outside the bio-shield is one solution. But standard options offered by MCNP, including SSW/SSR and SDEF cards, show relevant limitations. We present a methodology overcoming the MCNP limitations to transfer the plasma radiation information at the bio-shield. It is based on grouping the pointwise information stored in WSSA files to build piecewise probability distributions (PPDs). One or more PPDs are later processed by an MCNP source subroutine coded ad hoc to sample them as the radiation source. Successful and noticeable applications to ITER are shown.