Static and Kinetic Experiments on Accelerator-Driven System with 14MeV Neutrons in Kyoto University Critical Assembly

Abstract

In preparation for connecting a Fixed Field Alternating Gradient (FFAG) accelerator atthe Kyoto University Critical Assembly (KUCA), static and kinetic experimental and numerical analyses of Accelerator-Driven System (ADS) are envisaged. Improvement of source multiplication by the implementation of a neutron guide is expected to affect the characteristics of the ADS core. The effects on reactivity and neutron flux distribution are investigated by measurements of the subcriticality and the reaction rate distributions of indium wire, respectively, using the KUCA core and the current 14MeV pulsed neutron generator. A comparison of the results of static measurements with those of calculations provides an estimation of MCNP-4C3 precision with JENDL-3.3 and ENDF/B-VI.2 for the basic research on ADS with 14 MeV neutrons at KUCA. The neutron guide has proved to be experimentally effective in improving external source when it is extended into the fuel region. Since the reactivity range of the actual ADS operation is expected to be around 3%Δk/k, the validity of both measurements and calculations has been demonstrated up to 6%Δk/k for the current KUCA cores. The prompt neutron decay constant is obtained by the pulsed neutron method, and subcriticality by the area ratio method, using an optical fiber detection system developed at KUCA. The optical fiber detector has been assessed as a promising original tool for the measurements of the subcriticality and prompt neutron decay constant, through ADS kinetic experiments with 14MeV neutrons.