MOCUM solutions and sensitivity study for C5G7 benchmark

This work uses the 2-D C5G7 benchmark to verify the accuracy and efficiency of the MOCUM code, a parallel neutronics program based on the method of characteristics (MOC) for arbitrary core geometries. Compared to references, MOCUM keff, assembly and pin power maximum percentage errors are 0.02%, −0.06%, and 0.64%, respectively. The parallel algorithm achieves speed-ups of more than 17 times, compared to the calculation speed using one thread. The sensitivity study of various MOC parameters reveals that the C5G7 benchmark problem requires 48 or more azimuthal angles. The strong flux gradient and the heterogeneous effects demand fine unstructured meshes to yield accurate flux solution. The simulation uses 258 million zones with an average mesh size of 0.016 cm2. The investigation of the polar angle quadrature indicates that Leonard polar angle performs slightly better and more than three polar angles are not necessary. In addition, parameter sensitivity study shows that coarse parameters are prone to introduce error to the neutron flux but not keff.