Study on the effect of moderator of the proportional Boron-lined counter on the neutron detection efficiency

The proportional boron-lined counter as a common source-range detector is widely used in reactor monitoring, which has high detection efficiency for thermal neutron. The detection efficiency of the proportional boron-lined counter for fast reactor monitoring can be improved by using proper moderator. The relative detection efficiency and absolute detection efficiency of the proportional boron-lined counter in different thickness of the moderator for mono-energy neutrons of different energy were simulated by using MCNP, the tend-line of the relative detection efficiency and absolute detection efficiency were obtained. Also the detection efficiency of selected proportional boron-lined counter to the typical neutron spectrum of the fast reactor was simulated, and then the optimized moderator was designed. It would have some degree of guiding significance to design the nuclear measurement system of the fast reactor. (authors)