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This paper presents numerical experiments on reactivity measurement by the inverse kinetics method in the subcritical domain or at low power. The increase in the fluctuation of the neutron signal at low power levels will cause difficulties in the evaluation of reactivity. And the effect of direct emission from the external neutron source to the detector may not be neglected at lower power. Two cases are discussed: a large reactivity change as in a rod drop experiment and the reactivity change when the neutron signal is affected by direct emission from the neutron source. These cases have been studied with numerical simulations, and optimal ways to evaluate the reactivity under such conditions have been discussed.

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SUMMARYThe battery energy storage system (BESS) is prospective energy storage in the smart grid, and the hybrid energy storage system (HESS), using two different kinds of battery, is also being studied to achieve better performance and the lower cost than the single-battery-type BESS. However, the cost issue has not yet been evaluated explicitly. On the other hand, BESS has been studied and offers promise for ancillary service, although HESS has not been applied to frequency control in power systems. This paper focuses on the application of HESS to frequency control and its economic analysis. In this paper, the important battery characteristics in the application to a power system are introduced and two kinds of HESS are evaluated in terms of their cost when applied to frequency control. In addition, the cost HESS is used for peak shift as well as frequency control is analyzed. C⃝