Competitive resonance interference models in direct whole core transport code nTRACER

The capability of nTRACER was enhanced with WIMS IAEA library using the equivalence theory and Dancoff correction method based on the resonance integral data. The background XSs, for the heterogeneous system, incorporating the shadowing effects, are evaluated by the enhanced neutron current method. The effective XSs are generated using the Resonance Integral (RI) data by interpolating for background XSs and temperatures. The conventional method, which augments the background XS with average absorption XSs of all other resonant isotopes in the mixture, is used for treating the resonance interference in mixed resonant absorbers. A lot of methods are being developed for the resonance self-shielding in mixed absorbers, but still there exists some inadequacy in the XSs evaluation. The most accurate method is solving the UFG slowing down equation, but at the cost of huge computational burden. On the other hand, the conventional method is the simplest and easy to implement, but it has drawback, that it can't correctly estimate the cross sections in mixed absorbers because it adds the absorption XS. The resonance interference treatment methods are studied and implemented in nTRACER and checked the capacity to improve the overlap effects for multiple resonant isotopes. In XST method, the XSs are improved a lot as compared to conventional method, but still there exists discrepancy in the lower energy range. This method is very fast having no burden during execution