A whole-core coarse mesh neutron transport method in 2D cylindrical (R, theta) geometry

In this paper, the hybrid stochastic deterministic coarse mesh radiation transport method COMET is extended to 2D cylindrical geometry for whole-core neutronics calculations. To facilitate the extension new functions in cylindrical geometry were developed for expanding the incident angular flux on the (r, Θ) surfaces. The new COMET method is tested in a set of simplified pebble bed reactor cores in 2D (r, Θ) geometry, consisting of an inner reflector, an annular fuel region, a controlled outer reflector. The comparisons indicate that COMET achieves an accuracy close to the Monte Carlo method (MCNP), with computational efficiency for core calculations that is at least 3 orders of magnitude faster than that of MCNP when a precomputed response library with a 4th order expansion in space and a 2nd order expansion in the polar and azimuthal angles is used.