Equivalence Resonance Integrals for Lattices of Annular Absorber Rods

Resonance integrals for lattices of annular rod absorbers can be accurately determined by ordinary equivalence relation procedures. This is demonstrated for water lattices of annular uranium rods whose inner cylindrical zone is either a void or is water filled. The equivalence cross section, needed to enable the use of tabulated homogenous integrals, is given by a formula recently developed. There are three parameters in the formula that need estimation: a Dancoff factor for the lattice, the probability of neutrons entering the inner rod zone to collide there, and a Bell factor. Ways and means to estimate these parameters are discussed and demonstrated. The interpolation of resonance integrals from entries in existing tables of homogenous integrals is performed with an accurate technique. Results of the equivalence-based calculations are compared with results by the integral transport RABBLE code.