Calculation of kinetic parameters of Caliban metallic core experimental reactor from stochastic neutron measurements

Several experimental devices are operated by the Criticality and Neutron Science Research Department of the CEA Valduc Laboratory. One of these is the metallic core reactor Caliban. Knowing the fundamental kinetic parameters of the reactor is very useful, indeed necessary, to the operator. The purpose of this study was to develop and perform experiments allowing to determinate some of these parameters. The prompt neutron decay constant and particularly its value at criticality can be measured with reactor noise techniques such as the interval-distribution, the Feynman variance-to-mean, and the Rossi-α methods. By introducing the Nelson number, the effective delayed neutron fraction and the average neutron lifetime can also be calculated with the Rossi-α method. Subcritical, critical, and even supercritical experiments were performed. With the Rossi-α technique, it was found that the prompt neutron decay constant at criticality was 6.02 × 10⁵ ± 9%. Experiments also brought out the limitations of the used experimental parameters.