Experimental Study of Neutron Initiation Probability at CFBR-II with Pulsed Neutrons

Based on a new experimental method implemented for validating neutron initiation probability, a set of burst initiation probability experiments (128 bursts) that were initiated by simultaneously injecting pulsed neutrons just as the reactor achieves the prompt supercritical state of 0.042 $ has been carried out at the CFBR-II (Chinese Fast Burst Reactor–II). The experimental configuration and procedures remained the same throughout the entire set of experiments. Based on the measured data, each burst was tallied by judging whether or not the burst was initiated by the pulsed neutrons. With the injection of pulsed neutrons (the equivalent strength of the neutrons is 1230), the tallies of the burst initiated by pulsed neutrons were 44, and hence, the experimental result of initiation probability is 0.344, which is 27% more than the theoretical calculation result of 0.271. Some factors that influence the experimental results are discussed. The discrepancy is attributed mainly to neutrons that are scattered and returned from the environment during the injection of pulsed neutrons and the statistical deviation.