Reactivity control system conceptual design options for the SP-100 space reactor

A reactivity method (the two frequency one detector system (TFODS)) was experimentally verified on the AGN-201M thermal reactor to obtain the absolute steady state reactivity, and demonstrate the feasibility of acquiring the transient reactivity. The results of this method were extrapolated and used, along with other reactivity methods to conceptually design the real-time reactivity (and power control) system for the SP-100 space power reactor. A detailed description of the TFODS hardware and software is given. The TFODS obtains the absolute and net reactor reactivity by manipulating the frequency domain components inherent in the neutron detector current signal. The ratio of the average high frequency to the average low frequency components (empirically set) is used to determine the reactivity. The TFODS was successfully used to determine an unknown AGN-201M steady state reactivity, with a relative error of 18%. The TFODS transient curves as a function of reactivity are apparently different from the steady state reactivity curves. The transient curves are also a function of the rate of reactivity insertion. Two conceptual design options are presented for the reactivity (and power) control systems (RCS) of the SP-100 space nuclear reactor