Foundations and impact of evaluated nuclear data on fusion reactor design

We present an overview of the use of evaluated nuclear data in radiation transport simulations for fusion reactor design and discuss the impact of different types of data on analysis results and uncertainty quantification. Accurate neutron and photon cross sections form the foundation of radiation‐transport simulations used to predict shielding performance, nuclear heating, activation, and tritium breeding. To validate and extend these data, integral benchmarks—such as critical assemblies, mock‐up assemblies with representative materials, and fusion‐relevant irradiation experiments—provide end‐to‐end tests of library performance under realistic applications. However, most of the nuclear data validation efforts to date have understandably focused on critical systems. Nuclear responses relevant to fusion systems require further attention due to the higher neutron energies, additional reaction channels, and the importance of anisotropic fluxes in transport simulations for fusion reactor design. This talk discusses the important differences from a nuclear data perspective between the simulation of fission and fusion systems and highlights weak spots in evaluated nuclear data libraries for fusion applications including high energy cross sections, secondary particle energy-angle spectra, and covariance data. Pathways for improving these issues are presented along with facilities capable of addressing them.