Accuracy of reaction rates in the accelerator-driven system with 14 MeV neutrons at the Kyoto University Critical Assembly

Abstract

Reaction rate experiments on the accelerator-driven system (ADS) are conducted by combining a critical assembly of a solid-moderated and -reflected core with a pulsed neutron generator. Neutrons (14 MeV) generated from the accelerator are injected into a subcritical system and the reaction rates are measured by the foil activation method to obtain neutronic spectrum data. The numerical calculations are executed by MCNPX with ENDF/B-VI.8, JENDL-3.3 and JENDL/D-99 libraries to evaluate the reaction rates of activation foils set in the center of the core. For the ADS experiments with 14 MeV neutrons, the C/E values between the experiments and the calculations are found to be well within the relative difference of about 30% in all foils up to subcriticality 1.05 %Δk/k. The reaction rates don't depend on the subcriticality level in cases of 115 In, 56 Fe (purity 99.99%), 27 Al, whereas subcriticality dependence is observed in 93 Nb. In the critical experiments carried out in the A, B and C cores, special mention should be made of the remarkable effect of the composition rate of 56 Fe material. Thus a remarkable improvement is observed in the accuracy of experimental and numerical reaction rates, demonstrating the importance of material impurity

Power spectral analysis for a thermal subcritical reactor system driven by a pulsed 14 MeV neutron source

“…The numerator of the first term is the same as that of Equation (30), while the numerator of the second term contains not only α 1 instead of α 0 but also two values of the higher eigenfunction at two detector positions. No systematical deviation of this fitted curve from the point data can be observed.…”

“…In the preparation for connecting the proton-beam accelerator at KUCA, a series of static and kinetic experiments [25][26][27][28][29][30] on ADS with 14 MeV neutrons have been conducted. These experiments have been carried out in several solid-moderated and -reflected cores.…”

Determination of prompt-neutron decay constant from phase shift between beam current and neutron detection signals for an accelerator-driven system in the Kyoto University Critical Assembly

“…A wide variety of reactor physics experiments on an ADS using the pulsed spallation neutrons is now in progress [10,11]. In the preparation for connecting the proton-beam accelerator at KUCA, a series of static and kinetic experiments on an ADS with pulsed 14 MeV neutrons has been conducted [12][13][14][15][16][17][18][19][20]. As a basic study for online monitoring of the subcriticality in the operation of an ADS, various Feynman-α and power spectral analyses for a subcritical reactor system driven by a pulsed 14 MeV neutron source have been performed.…”

Development of the active neutron-based interrogation system with D-D neutron source for the detection of special nuclear materials

“…The core is composed of highly enriched uranium fuels and 14MeV pulsed neutrons by D-T reactions are injected into the fuels with use of a Cockcroft-Walton type accelerator installed in the KUCA as shown in Figs. 4 and 5[10]. By using this accelerator, production pulse neutron period and pulse width are arbitrarily altered according to experimental conditions.…”