Analysis of dynamic perturbations in the RA-2 zero power reactor

Transfer function measurements were conducted in the RA-2 zero power reactor assembly using the cross-correlation technique of noise analysis. Perturbations found in the experimental curves did not allow an accurate evaluation of the prompt-neutron decay constant, α_c. The source of these perturbations was found to arise from mechanical vibrations transmitted to the control rods. Dynamically stimulated oscillations induced in both a control rod and small piece of cadmium were analyzed. Their behaviour as compared with results from a reactor model developed from both analog and digital computations; a strong distortion in the power spectral density was found for the control rod oscillation. Reactor responses to sinusoidal reactivities of various amplitudes (0·05–3·00 dollars) and frequencies (0·01–100 Hz) were computed. The inverse problem, i.e., predicting reactor input from a given output, was also studied. Both calculated and measured power spectral densities are shown.