The measurement of reactivity using algorithms derived from the dynamic period equation

Two algorithms, inverse dynamics and the hybrid method, have been developed for the measurement of reactivity. The basis of each is the dynamic period equation which gives the instantaneous reactor period as a function of both the rate of change of reactivity and the reactivity. Both methods are rigorous. Inverse dynamics uses the dynamic period equation to determine the rate of change of reactivity; the reactivity is then found by integration. The hybrid method applies simultaneously both the standard and the alternate forms of the dynamic period equation, thereby solving directly for the reactivity. Both techniques have been tested on the 5-MWt MIT Research Reactor. The results of the experimental evaluation are presented together with an assessment of their utility of the algorithms