Correction of the Reactivity Measured by ORUK Technique

Corrections of the reactivity values obtained by means of the ORUK (inverse solution of kinetic equations) technique are presented taking into account the changes in the neutron flux form function and the efficiency of neutron detectors when negative reactivity is inserted into the critical multiplying system. The form function and efficiency were assumed to be proportional to the neutron detector signal normalized to the integral functional of neutron flux in the core volume. The ratio of the steady-state normalized signals before and after the insertion of the negative reactivity is the correction factor to the measured value of reactivity. Two approaches to estimation of the correction to the results of reactivity measurements at the critical assemblies of RBMK are considered: the mean measured signal of many in-core detectors or the calculated values of neutron power and spectral projection amplitude of the neutron field are used to normalize and correct the signals of a few detectors. In both the cases, owing to the correction, the spread of the values of reactivity measured by different detectors was multiply reduced as compared with the results of ORUK with integral signals.