On the treatment of resonance cross sections in thermal reactor lattices using the WIMSD/4 transport lattice code

This paper discusses the mathematical models and methods used for calculating resonance cross sections in the resonance region of the neutron energy spectrum. Particular attention has been paid to the treatment outlined in the WIMSD/4 version of the WIMS lattice transport code. The significance of the resonance integral evaluation needed for computing the effective group resonance cross sections is also presented. The resonance treatment was applied to the Ghana Research Reactor-1 fuel lattice to compute the resonance escape probability, Dancoff factors, flux depression factors corrected for resonance absorption to the removal cross sections and the evaluated correct-ion factors in the 13 resonance energy groups of the WIMSD/4 lattice code. The application shows that the resonances for the n*fission (or Nu*Fission) cross sections are higher than for absorption cross-sections with the resonance energy spectrum for resonance absorbers U235 and Pu239. The Dancoff factor increased by a nominal 0.9 % across the resonance energy range. Journal of Applied Science and Technology (JAST) , Vol. 5, Nos. 1 & 2, 2000, pp. 1 - 1