HEURISTIC DERIVATION OF ROSSI-ALPHA FORMULA WITH DELAYED NEUTRONS ANDCORRELATED SOURCE

Formulae of neutron correlation measurements, such as Feynman- and Ros si-alpha, have been derived in the past by the master equation method or the joint detection probability method. Generally speaking, the mas ter equation method is rigorous in the sense. that all elementary proc esses can be taken into account, but its manipulations are complicated and elaborate. On the other hand, the method of joint detection proba bility is heuristic, but several kinds of formulae can be easily deriv ed from it. It seems that these methods are complementary. Recently in order to develop a method for evaluating subcriticality in the accele rator driven subcritical reactors, we derived the Feynman-alpha formul a with a correlated neutron source and delayed neutrons based on the m aster equation method. In this paper, based on a heuristic method, we have derived the joint detection probability including one group of de layed neutrons and a correlated neutron source, which is valid in deep subcritical systems. Then, as an application of this joint probabilit y, the Rossi-alpha formula with delayed neutrons and a correlated neut ron source has been derived. (C) 1998 Elsevier Science Ltd. All rights reserved.