Dual Reference Perturbation Method for Fast Loading Pattern Evaluation

As an effort of fast evaluation of fuel assembly (FA) loading patterns (LP) during an LP optimization process, the hybrid harmonics and linearization perturbation (HHLP) method of combining a low order harmonics expansion and local perturbation terms was proposed by Zhang et al. Despite the excellent results obtained from HHLP, there are some drawbacks needing improvements. The major drawback is that the accuracy of HHLP is dependent on the reference LP. If the selected reference LP is unreasonable, the results of HHLP can be trustable even for benign LPs. The other important problem is that the accuracy deteriorates for cores having strongly absorbing fuel assemblies such as MOX fuels. As a way to overcome these drawbacks, we propose a dual reference perturbation (DRP) method that does not require any elaborate reference LP nor low order higher harmonics expansion. The fast LP evaluation model can be eventually used as a screening tool in the case that the full 3-D nodal calculations are to be performed in the LP optimization