Reaction Rate Analyses for an Accelerator-Driven System with 14 MeV Neutrons in the Kyoto University Critical Assembly

Self Cite

At the National Cancer Center, proton irradiation experiments have been conducted using the cyclotron accelerator to measure the neutron spectrum by the foil activation method. The experimental results demonstrate that high-energy neutrons are bombarded by injecting high-energy protons onto the tungsten target. The agreement between the results of the experiments and the MCNPX calculations with ENDF/ B-VI is around 20% in the relative difference of the C/E (calculation/experiment) values in some of the 209 Bi(n, xn) 210Àx Bi reactions. Here, the activation foil 209 Bi is useful in obtaining experimental neutron spectrum information on nuclear spallation reactions of the tungsten target by the high-energy protons ranging between 150 and 235 MeV. The current experimental data could contribute to evaluating the accuracy of the numerical simulation methodology of reaction rates and the uncertainties of cross sections of 209 Bi, as experimental benchmarks.

Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Reaction Rate Analysis of Nuclear Spallation Reactions Generated by 150, 190, and 235MeV Protons

Pyeon

Shiga

Abe

et al. 2010

Self Cite

“…Since the fitted Equation (11) is tied down at the origin, it is expected that the fitting may be hardly influenced by these background data. Table 5 summarizes the reactivities obtained by the beam trip experiments, where the counting for the integral of Equation (14) was terminated at 300 s after beam trip operation. As the errors of these results of the LSIKM, only the statistical uncertainties originated from the least-squares fit were employed.…”

Section: Fit To Uncorrelated Peaks Pulse Repetitionmentioning

confidence: 99%

“…A wide variety of reactor physics experiments on 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 ADS with pulsed 14 MeV neutrons has been conducted [12][13][14][15][16][17][18][19]. As a basic study for on-line monitoring of the subcriticality in operation of ADS, various power spectral analyses for a subcritical reactor system driven by a pulsed 14 MeV neutron source were carried out [19].…”

Section: Introductionmentioning

confidence: 99%

Measurement of large negative reactivity of an accelerator-driven system in the Kyoto University Critical Assembly

Sakon

Hashimoto

Maarof

et al. 2013

Self Cite

Large negative reactivity of a subcritical system driven by a pulsed 14 MeV neutron source has been measured in the Kyoto University Critical Assembly. The subcriticality of the accelerator-driven system (ADS) ranged in effective multiplication factor roughly from 0.98 to 0.92, which corresponded to an operational range of an actual ADS proposed by Japan Atomic Energy Agency. As the measurement technique, pulsed neutron method, power spectral analysis for pulsed neutron source, accelerator-beam trip method were employed. From neutron count decay data obtained by the pulsed neutron experiment, not only the promptneutron decay constant of fundamental mode but also a higher spatial mode could be derived. The subcriticality was also determined from the fundamental decay constant. The measured cross-power spectral density consisted of a familiar correlated reactor-noise component and many uncorrelated delta-functionlike peaks at the integral multiple of pulse repetition frequency. The fundamental prompt-neutron decay constant, i.e., the subcriticality determined from the latter uncorrelated peaks was consistent with that obtained by the above pulsed neutron experiment. However, the magnitude of the former correlated component was reduced with an increase in the subcriticality and eventually this component became almost white at deeply subcritical state ranging in the multiplication factor under 0.95. Consequently, the determination of the decay constant from the correlated component was impossible under such a subcritical state. As data analysis method for the beam trip experiment, both the conventional integral count method and the least-squares inverse kinetics method (LSIKM) were employed. The LSIKM analysis led to the consistent subcriticality with that obtained by the pulsed neutron experiment, while the integral count method significantly underestimated the subcriticality. This underestimation originated from a residual background count, which was maintained after the beam trip. The LSIKM was mostly not influenced by such a slight count rate.

“…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.…”

Section: Description Of Kuca Facilitymentioning

confidence: 99%

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

Sakon

Hashimoto

Sugiyama

et al. 2013

Self Cite

A series of power spectral analyses for a thermal subcritical reactor system driven by a pulsed 14 MeV neutron source was carried out at Kyoto University Critical Assembly (KUCA), to determine the promptneutron decay constant of the accelerator-driven system (ADS). The cross-power spectral density between time-sequence signal data of two neutron detectors was composed of a familiar continuous reactor noise component and many delta-function-like peaks at the integral multiple of pulse repetition frequency. The prompt-neutron decay constant inferred from the reactor noise component of the cross-power spectral density was consistent with that obtained by a pulsed neutron experiment. However, the reactor noise component of the auto-power spectral density of each detector was hidden by a white chamber noise in the higher-frequency range and this feature resulted in a considerable underestimation of the decay constant. For several runs with a low pulse-repetition frequency, furthermore, we attempted to infer the decay constant from point data of the delta-function-like peaks. The analysis for a run under a slightly subcritical state resulted in the consistent decay constant; however, those for other runs under significantly subcritical states underestimated the decay constant. Considering the contribution of a spatially higher mode to the point data, the above underestimation was solved to obtain the consistent decay constant. While the Feynman-α formula for a pulsed neutron source is too complicated to be fitted directly to variance-to-mean ratio data, the present analysis on frequency domain is much simpler and the conventional formula based on the first-order reactor transfer function is available for fitting to power spectral density data.