Reactor Kinetics Quarterly Progress Report for January-March 1957

Investigation of the energy coefficient of radiolytic gas production for the KEWB I reactor as a function of core temperature shows the coefficient to be independent of temperaturc above about 30 C. The temperature coefficient of reactivity is found to increase markedly with temperature and reach a value of 0.031%/ C at 90 C with a core pressurc of 71 cm Hg. A void coefficient of reactivity was determined in the certral exposure tube of the reactors and is related to the void coefficient derived from the temperature coefficient measurements. Investigations of the transient power oscillations show a decrease in the period of oscillation and an increase in the damping of the oscillation with increasing reactivity input. An evaluation of the ''boron-bubble'' experiment and its extension to more complex geometries was made in conaection with the determination of ''absolute reactivity.'' This study indicated a possible solution to the difficulties involved in the experimental determination of the absolute reactivity as contrasted with the reactivity in dollars observable in kinetic experiments. A method was devised for determining the transfer function of a reactor from power fluctuations during steady operation by treating the fluctuations as the response of the system to an inherent random or stochastic driving force. A power series solution of the one-group reactor kinetics equations was obtained for the rcactivity as a prescribed cubic function of time. (For preceding period see NAASR-2134.) (auth