A Method of Calculating Resonance Absorption in a Circularized Cell

A method of calculating resonance absorption in a rod in a two-region circularized cell is developed. The method uses space-and lethargy-dependent neutron sources and, thus, includes overlapping and interference effects. An energy range of interest is divided into extremely narrow intervals of equal lethargy width. For each interval, the source distribution in each region is taken to be a three-term polynomial. By using this form for the source and the assumption that neutrons enter the rod isotropically, we obtain the reaction rates and the flux distribution for the interval. The reaction rates are used to obtain resonance integrals; the flux distribution is used to get the source distribution for lower energies. Calculations of the errors introduced into the resonance integral of the two closely spaced ²³²Th resonances by the assumption of flat sources are given, as well as calculations of the effects of interference in UO₂-ThO₂ mixtures, which lie within the errors of the experimental results obtained by Foell.