Effect of Delayed-Neutron Mode on the Determination of the Prompt-Neutron Decay Constant in Pulsed-Neutron Measurements

An improved data processing method is developed for pulsed-neutron measurements in a multiplying medium. The characteristic feature of the method is to determine the value of the prompt-neutron decay constant a as accurately as possible by removing the delayed-neutron decay component from the raw experimental data. The delay ed-neutron decay component is estimated to be the deviation of the response of a one-point reactor from a single exponential decay for repeated pulsed-neutron bursts. It is obtained by taking account of the first and second post-neutron bursts. From the application of the method to some test data provided by calculation and to experimental data from pulsedneutron experiments in the Semi-Homogeneous Ex-periment it is found that the usual data processing method, disregarding the slowly decaying delayedneutron mode, should underestimate the value of a by ∼4% in a near-critical multiplying medium having a neutron lifetime of ∼1 msec.