The kinetics of a flux-trap cylindrical reactor system were studied both theoretically and experimentally. A state-variable approach was used to develop a twenty-fourth-order model describing neutron and temperature kinetics in 14 regional system components. The modified Mikhailov method was used to determine the stability of the model. The reactor system was studied using step testing and pseudorandom multifrequency binary sequence testing procedures with a small-computer based instrumentation system. Measurements were made at powers of 1, 2.5, and 4 MW. The frequency response analysis of the system model compared favorably with experimental observations.