Calculation of the prompt neutron decay constant for the KUCA facility driven by a stationary or pulsed external neutron source

Abstract

ABSTRACT In this study, the I-4 configuration of the KUCA facility, as one of the subcritical experimental benchmarks, was examined using computer simulations and experiments. This configuration has all control rods withdrawn. Two different external neutron sources have been analyzed: a pulsed neutron source generated from protons interactions with target materials and a californium neutron source. The two neutron sources have similar spatial effects because the californium neutron source has been located at the position of the proton beam target. Different methods have been applied to calculate the prompt neutron decay constant (alpha) including: the count rate as a function of time fitting, the Rossi, the Feynman, the Cross-Power Spectral Density (CPSD), the Auto-Power Spectral Density (APSD), and the Maρta methods. The input data for these methods consist of the detector timestamps, which can be obtained experimentally using neutron detectors operating in pulse mode or by MCNP fixed-source simulations. The CPSD, the APSD, the count rate fitting, and Maρta methods do not require the detector timestamps since these methods use the average number of neutron counts over some time bins. These averages can be obtained experimentally using detectors operating in the current mode or by MCNP fixed-source simulations.