Development and verification of multigroup advanced semi analytic nodal method solver for HTGR analysis with MHTGR-350

This study introduces the multigroup advanced semi-analytic nodal method (A-SANM) tailored for the high-temperature gas-cooled reactor (HTGR) analysis. The A-SANM has been crafted specifically for reactors with hexagonal geometries, such as the Vodo-Vodyanoi energetichesky reactor (VVER) and HTGR. A triangular node was constructed with a 12-term basis to delineate the flux by integrating both the polynomial and hyperbolic functions. The multigroup calculation kernel of this approach was embedded in the nodal diffusion code, RAST-V. To evaluate the computational efficiency of the A-SANM, we employed the MHTGR-350 benchmark. This benchmark, associated with a modular high-temperature gas-cooled reactor, was established by the OECD/NEA under the NGNP Project in 2021. In this study, we conducted the Phase I calculations to evaluate the performance of the neutronics code. Key parameters including the multiplication factor, rod worth, and axial and radial power distributions were meticulously assessed. When juxtaposed with the Monte Carlo code MCS, the A-SANM exhibited a deviation of –97 pcm. Differences in the axial and radial power were ± 4 and ± 3 %, respectively. Furthermore, the rod worth discrepancy was –6 pcm when set against the MCS. In summary, this study effectively elucidates the potential and precision of the multigroup A-SANM for the HTGR evaluations.