Determination of Subcritical Reactivity of a Thermal Accelerator-Driven System from Beam Trip and Restart Experiment

Taninaka, Hiroshi; Hashimoto, Kazuo; Pyeon, Cheol Ho; Sano, Tadafumi; Misawa, Tsuyoshi; Unesaki, Hironobu; Sugiyama, Wataru; Ohsawa, Takaaki

doi:10.3327/jnst.48.873

Cited by 7 publications

(7 citation statements)

References 22 publications

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“…The LSIKM leads to the consistent reactivity with that obtained by the pulsed neutron experiment, while the integral count method significantly underestimated the negative reactivity. In a previous experiment at a slightly subcritical range in effective multiplication factor over 0.98, this underestimation was scarcely observed [16]. This is because the integral of Equation (14) is much larger than background counts for several hundred seconds.…”

Section: Fit To Uncorrelated Peaks Pulse Repetitionmentioning

confidence: 91%

“…The detailed description on the theory of these methods and the application to beam trip experiment was given by Taninaka et al [16]. Here, the theory and the application are briefly described.…”

Section: Accelerator-beam Trip Experimentsmentioning

confidence: 99%

“…The prompt-neutron decay constant could be determined from the former correlated component and the latter uncorrelated peak points, respectively, and these decay constants were consistent with that obtained by a pulsed neutron experiment. As another basic study for a calibration and an inspection of on-line monitoring system, a deterministic technique based on acceleratorbeam trip or restart operation was proposed to obtain the subcriticality of ADS and the applicability was experimentally demonstrated [16]. The above experiments have been confined to a slightly subcritical range in effective multiplication factor (k eff ) over 0.98.…”

Section: Introductionmentioning

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%

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

Sakon

Hashimoto

Maarof

et al. 2013

Journal of Nuclear Science and Technology

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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.

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Section: Fit To Uncorrelated Peaks Pulse Repetitionmentioning

confidence: 91%

Section: Accelerator-beam Trip Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Sakon

Hashimoto

Maarof

et al. 2013

Journal of Nuclear Science and Technology

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“…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

Journal of Nuclear Science and Technology

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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.

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

Pyeon

Takemoto

Yagi

et al. 2012

Annals of Nuclear Energy

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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

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Determination of Subcritical Reactivity of a Thermal Accelerator-Driven System from Beam Trip and Restart Experiment

Cited by 7 publications

References 22 publications

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

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

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

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

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