Marvin: A parallel three-dimensional transport code based on the discrete ordinates method for reactor shielding calculations

Abstract

Marvin is a parallel three-dimensional discrete ordinates (SN) code dedicated for reactor shielding calculations. It employs the multi-group and SN approximations to discretize the energy and angular variables, respectively. Multiple discretization methods, namely weighted diamond difference, theta-weighted diamond difference and step-characteristic, have been implemented to discretize the spatial variables. The within-group transport equation is solved by the source iteration or Krylov subspace solvers, both of which employ the Koch-Baker-Alcouffe (KBA) algorithm to parallelize the transport sweep process. The upscattering in the thermal energy range is treated with thermal upscattering iteration scheme. The code design of Marvin features the mixed programming model and a three-layer architecture design. Two benchmark problems devised from realistic reactor core configurations, namely the VENUS-3 and HBR-2 problems, were calculated to evaluate the correctness, accuracy and parallel computing performance of Marvin. The calculation results were compared against TORT solutions as well as measured data. The validation results indicate that: Marvin is properly implemented and can faithfully produce solutions to the reactor shielding problems; the computing efficiency of Marvin can be significantly enhanced via the KBA parallel transport sweep algorithm.