PHYSOR 2018: Reactor Physics paving the way towards more efficient systems Cancun, Mexico, April 22-26, 2018
The Macro Level Grid scheme for the efficient application of the subgroup method is presented, that employs the number density consideration factor (NDCF) and the temperature consideration factor (TCF) for the treatment of non-uniform number densities and temperature distributions in a core. This scheme provides efficient resonance treatment in direct whole core calculations of power reactors that involve thermal feedback and isotopic depletion. The new method solves the subgroup fixed source problem only 8 times per energy group with 8 macroscopic subgroup levels, regardless of the number of resonance isotopes in the problem
of interest. The escape cross section of each isotope is obtained by interpolation using the precalculated ones with the specified macro level grid. This scheme turns out to be superior to the conventional scheme in terms of computing time and accuracy. More than 30% of the computing time for fixed source problems is saved with negligible reactivity errors of about a few pcm, whereas the conventional one has consistent reactivity errors of about +60 ~ +100 pcm for the regular uranium fuel problems. Moreover, it turns out that the new method provides high accuracy even for very heterogeneous mixed oxide assembly problems with significantly shortened times
