Disadvantage Factor in a Cell with Thin Moderator

Abstract

A monoenergetic disadvantage factor is introduced by extending the method of Amouyal & Benoist^(1)∼(3) so as to permit the treatment of a cell with thin moderator. To take into account the flux depression in a fuel rod, the blackness of the fuel rod is introduced into the calculation as in the paper by Amouyal et al. The Wigner-Seitz equivalent cylindrical cell method is incorrect for closely packed lattices. To cover this shortcoming, an extended Dancoff factor is introduced to take into account the interference among fuel rods. This factor can be easily calculated in a homogeneous system, and so no consideration is necessary to account for the shadowing effect by other fuel rods. The result obtained is similar to that from the collisionprobability method but can be calculated more easily. And improvement over the Amouyal-Benoist method is thus obtained.