Publications

Computationally optimized multi-group cross section data collapsing using the YGROUP code

Yi, C.; Sjoden, G.; Mattingly, John K.; Courau, T.

A multi-group cross section collapsing code, YGROUP, has been developed to speed up deterministic particle transport simulations by reducing the number of discrete energy groups while maintaining computational transport accuracy. The YGROUP code leverages previous studies based on the "contributon" approach to automate group selection. First, forward and adjoint deterministic transport calculations are performed on a smaller problem model, or on one section of a large problem model representative of problem physics using a fine group structure. Then, the calculated forward flux and adjoint function moments are used by YGROUP to collapse the fine group cross section library and generate a problem-dependent broad group cross section library. Finally, the broad group library is used for new transport calculations on the full scale/refined problem model. YGROUP provides several weighting options to collapse the cross section library, including flat, flux, and contributon (the product of forward flux and scalar adjoint moments). Users can also specify fine groups in specific energy ranges of interest to be reserved after collapsing. YGROUP also can be used to evaluate the Feynman-Y asymptote characterizing neutron multiplicity.