In the design of fusion reactors, determining radiation levels due to neutrons and photons (gammas) throughout the reactor and its surroundings is important. Radiation transport codes need to have accurate cross-section libraries in order to produce accurate results. The Fusion Evaluated Nuclear Data Library (FENDL) is an international effort coordinated by the International Atomic Energy Agency, Nuclear Data Section, that assembles a collection of the best nuclear data for fusion applications. In the current FENDL-3.1d data library, neutron cross sections for 65 of the 180 isotopes present in the library come from ENDF/B-VII.1.

Monte Carlo–based neutronics calculations using cross-section libraries from FENDL (versions 2.1 and 3.1d), ENDF/B (versions VII.1 and VIII.0), and candidate new evaluations for key structural elements/isotopes such as iron and chromium were performed. The calculations were performed in reactor-relevant models including a one-dimensional (1-D) cylindrical model of ITER, a three-dimensional (3-D) computer-aided design (CAD)–based model of ITER, and a 3-D CAD-based model of the U.S. Fusion Energy System Studies Fusion Nuclear Science Facility (FNSF).

The results show that neutron fluxes calculated with different cross-section libraries can be as much as 12% higher and as much as 8% lower than those calculated with the reference cross-section library (FENDL-2.1). Nuclear heating calculated with different cross-section libraries can be as much as 14% higher and as much as 8% lower than those calculated with the reference cross-section library. Iron displacements per atom calculated with different cross-section libraries can be as much as 9% higher and as much as 9% lower than those calculated with the reference cross-section library. Helium production calculated with different cross-section libraries can be as much as 19% higher and as much as 2% lower than those calculated with the reference cross-section library. Tritium production in the ITER 1-D model’s nonbreeding regions calculated with different cross-section libraries can be as much as 246% higher and as much as 5% lower than those calculated with the reference cross-section library. The tritium breeding ratio in the FNSF 3-D model calculated with different cross-section libraries averaged 1% higher at the inboard and 1.4% higher at the outboard than those calculated with the reference cross-section library.