A Measurement Method for Effective Delayed Neutron Fraction

A method was presented for measurement of effective delayed neutron fraction βeff by coupling experiment with theoretical calculation. In the experiment the reactor critical status was defined,and the subcritical reactivity under subcritical status, by using βeff as unit, was measured. With theoretical calculations, effective multiplication factor keff under critical status was calculated, and the deviation of the calculated results was evaluated. Then, keff under subcritical status was calculated and also revised with the deviation as same to critical status. So the reactivity under subcritical status was evaluated. Comparing the experimental result with the calculated result, βeff was defined. Since the reactor status was defined by experiments, the calculated keff under the status was little dependent on the theoretical models which described the reactor status. The results show that the accuracy of the measured βeff is higher than previous measurements. (authors)