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Yamane, Yuichi
Journal of Nuclear Science and Technology, 59(11), p.1331 - 1344, 2022/11
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)The reactivity was estimated from a time profile of neutron count rate or a simulated data in a quasi-steady state after sudden change of reactivity or external neutron source strength. The estimation was based on the equation of power in subcritical quasi-steady state. The purpose of the study is to develop the method of timely reactivity estimation from complicated time profile of neutron count rate. The developed method was applied to the data simulating neutron count rate created by using one-point kinetics code, AGNES, and Poisson-distributed random noise and to the transient subcritical experiment data measured by using TRACY. The result shows that the difference of the estimated and reference value was within about 5% or less for (
-1) for simulated data and within about 7% or less for 
-1.4 and -3.1 for the experimental data. It was also shown that the possibility of the reactivity estimation several ten seconds after the status change.
Yamane, Yuichi
Journal of Nuclear Science and Technology, 57(8), p.926 - 931, 2020/08
Times Cited Count：1 Percentile：11.8(Nuclear Science & Technology)An equation of power in subcritical quasi-steady state has been derived based on one-point kinetics equations for the purpose of utilizing it for the development of timely reactivity estimation from complicated time profile of neutron count rate. It linearly relates power, 
, to a new variable 
, which is a function of time differential of the power. It has been confirmed by using one-point kinetics code, AGNES, that the calculated points (
) are perfectly in a line described by the new equation and that points () calculated from transient subcritical experiments by using TRACY made a line with a slope indicated by the new equation.
Nakajima, Ken; Yamamoto, Toshihiro; Miyoshi, Yoshinori
Journal of Nuclear Science and Technology, 39(11), p.1162 - 1168, 2002/11
Times Cited Count：8 Percentile：47.85(Nuclear Science & Technology)A modified quasi-steady-state method has been developed to evaluate the mean power during a nuclear excursion in fissile solution. The original method used the critical equation based on the one-group theory to calculate the reactivity. However, the one-group approximation reduces the calculation accuracy and the geometrical buckling used in the critical equation is not applicable to complex geometries. Then, we have modified the method to use the feedback coefficients of reactivity. Although the modified method requires an external calculation to obtain the feedback coefficients, it is applicable to complex geometries and gives more accurate results than the one-group approximation. Moreover, a new method to calculate the boiling power has been developed. using the experimental data of a supercritical experiment facility, SILENE. Experimental analyses were conducted to validate the new method for supercritical xperiments using CRAC and TRACY. The results showed good agreements with the experiments.
