A Study on the Space and Energy Dependent Reactor Kinetics, with Direct Physical Interpretation of the Effective Neutron Lifetime and Criticality Factor

Abstract

First, the concept of neutron importance is introduced. It is assumed that each of the neutrons produced by fission in a chain reactor possesses an importance proportional to the number of its descendants. Secondly, on the basis of the law of conservation, a transport equation of the neutron importance is derived. Then, the effective neutron lifetime is defined as the mean interval of successive fission events in the course of the importance transport. The consistent definition of the criticality factor is the neutron multiplicity during the effective neutron lifetime so defined. After defining the basic reactor kinetics parameters, such as the effective neutron lifetime and criticality factor, the persistent time behavior of nuclear chain reactors has been investigated. The kernel form reactor equation is used because of its physical intelligibility. The formulas obtained are applicable to any reactor, provided that the neutron flux and its adjoint function is known either analytically or numerically.