OPERATIONAL CONTROL ROD REACTIVITY WORTHS FROM OBSERVED HEAT GENERATION RATES

Control rod reactivity worths can be determined with reasonable accuracy from estimates of the neutron absorption rate in the rods and evaluation of the change in reactor leakage rate on rod withdrawal. In the Hanford reactors these values are found from measured control rod heat generation and reactor flux distribution data. This calibration technique can also be applied to reactors without separate rod-cooling systems. The neutron absorption rate in the rods is obtained from rod surface foil activation or activation of the rods themselves. The change in reactor leakage upon rod insertion is found with theoretical determinations of the unperturbed flux distribution andd the flux distribution after insertion of an equivalent control region. (auth)