The variance-to-mean ratio in subcritical systems driven by a spallation source

Pázsit, Imre; Yamane, Yoshihiro

doi:10.1016/s0306-4549(97)00117-5

Cited by 46 publications

(13 citation statements)

References 9 publications

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“…Here we have used the notation r 2 = d 2 r/dX 2 | X=1 for the second factorial moment [15]. The objective now is to solve (16) and (17) by Laplace trans-form methods and we find the transformed identity as,…”

Section: A Two-point Variance To Mean Formulamentioning

confidence: 99%

Two-point theory for the differential self-interrogation Feynman-alpha method

et al. 2012

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A Feynman-alpha formula has been derived in a two region domain pertaining the stochastic differential self-interrogation (DDSI) method and the differential die-away method (DDAA). Monte Carlo simulations have been used to assess the applicability of the variance to mean through determination of the physical reaction intensities of the physical processes in the two domains. More specifically, the branching processes of the neutrons in the two regions are described by the Chapman -Kolmogorov equation, including all reaction intensities for the various processes, that is used to derive a variance to mean relation for the process. The applicability of the Feynman-alpha or variance to mean formulae are assessed in DDSI and DDAA of spent fuel configurations.

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Section: A Two-point Variance To Mean Formulamentioning

confidence: 99%

Two-point theory for the differential self-interrogation Feynman-alpha method

et al. 2012

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“…Therefore, previous studies on subcriticality monitoring have been concentrated on the improvement of the variance-to-mean (Feynman-α) method [9]. At the beginning, some authors [10][11][12][13] improved the conventional Feynman-α method to include the multiplicity of a spallation neutron source under a direct-current-mode operation of the accelerator, and they indicated that the spallation neutron source enhanced the correlation amplitude Y defined as the variance-to-mean ratio -1. Following the above studies, the formulae for a pulsed-current-mode operation of the accelerator, which was one of the candidates for practical ADS operation, were derived [14][15][16][17][18].…”

Section: Introductionmentioning

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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“…At the beginning, some authors [9][10][11][12] improved the conventional variance-to-mean (Feynman-) method 13) to include the multiplicity of spallation neutron source under direct-current-mode operation. Following these studies, the formulae for pulse-mode operation that is one of the candidates for practical ADS were derived.…”

Section: Introductionmentioning

confidence: 99%

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

Taninaka

Hashimoto

Pyeon

et al. 2011

Journal of Nuclear Science and Technology

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An experimental technique based on an accelerator-beam trip or restart operation is proposed to determine the subcritical reactivity of an accelerator-driven system (ADS). Applying the least-squares inverse kinetics method to the data analysis, the subcriticality can be inferred from time-sequence neutron count data after these operations. A series of beam trip and restart experiments with 14 MeV neutrons were carried out in a thermal ADS of Kyoto University Critical Assembly (KUCA), to demonstrate the applicability of the proposed technique. The subcriticalities evaluated using neutron counters far from the DT target were consistent with those obtained in a previous pulsed neutron experiment. However, a counter placed close to the target significantly overestimated the subcriticality. The present technique is expected to be available for subcriritcality measurement at startup and shutdown of various ADSs.

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The variance-to-mean ratio in subcritical systems driven by a spallation source

Cited by 46 publications

References 9 publications

Two-point theory for the differential self-interrogation Feynman-alpha method

Two-point theory for the differential self-interrogation Feynman-alpha method

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

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

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