Azimuthal flux distribution measurements around fuel rods in reduced-moderation LWR lattices

•We have measured azimuthal flux distribution by activation foil method.•Experiment analyses were carried out by using the MVP code with JENDL-3.3.•The results of the analyses approximately agree with the measurement results.•The measurements are useful for the validation of an advanced fuel design method.

An advanced analysis method named “micro reactor physics approach” was proposed, and the approach is needed for future reactor design considering the neutron behavior in fuel pellets. In order to validate the approach, neutron flux distribution measurements in a fuel pellet should be required. We have measured azimuthal flux distribution of fuel rods in Toshiba Nuclear Critical Assembly (NCA). A foil activation method with metallic foils was used for the measurement. Measured values were analyzed by a continuous energy Monte Carlo code MVP with the JENDL-3.3 library. The measurements are useful for the validation of an advanced fuel design method considering the neutron behavior in fuel pellets.