A vectorized and parallelized assembly transport method for nuclear reactor core analysis.

Abstract

The purpose of this study is to develop an accurate and cost effective methodology for solving the neutron transport equation in X-Y geometry. The proposed methodology is based on the integral transport equation. A new transfer probability method has been developed which removes the modelling limitations of the collision probability method encoded in the CPM-2 computer code. These limitations, infinite lattice geometry and isotropic scattering, inhibited the use of CPM-2 for global reactor calculations. The method is based on the use of collision, escape and transmission probabilities, together with linearly anisotropic scattering, for the assembly level calculations. The double $P\sb0$ or $P\sb1$ expansion of the angular flux on the assembly boundaries has been utilized. One of the primary objectives of this thesis has been to develop an accurate and efficient parallel-vector transport algorithm which can utilize advanced supercomputer architectures. The original CPM-2 transport algorithm has been successfully vectorized and parallelized with an order of magnitude reduction in CPU time, and a factor of 20 reduction in wallclock time. With the new parallel/vector transfer probability method (for isotropic scattering), the total CPU time has been reduced by a factor of 40, and the total wallclock time by a factor of 50. The transfer probability calculation is two orders of magnitude faster than the collision probability matrix calculation in the original code, with a factor of 400 reduction in wallclock time. The transmission probability method has been successfully applied to the standard BWR and PWR assemblies. The numerical results compare well with the TWODANT and CPM-2 reference solutions with isotropic scattering, and the TWODANT reference solutions with linearly anisotropic scattering.