Measurement of the Neutron Activity of a exp 252 Cf Source Relative to the Average Number of Prompt Neutrons Emitted Per Fission for the Spontaneous Fission

摘要

A method was developed for measuring the absolute neutron activity of a large exp 252 Cf source. The neutron counting assembly is composed of eight BF3 counters mounted in a large tank filled with water which is used as a moderator. The detection efficiency is determined using a low activity exp 252 Cf source. The method is based on the identification of every fission event, followed by the counting of the fission neutrons detected by the BF3 counters during a time interval equal to the maximum neutron lifetime in the moderator. The efficiency is thus obtained relative to the average number of prompt neutrons emitted per exp 252 Cf spontaneous fission which is commonly used as a standard. The measurement accuracy is estimated to be of the order of 1%. (Atomindex citation 11:555188)