PNNL

Abstract

The decreasing supply of 3He is stimulating a search for alternative neutron detectors; one potential 3He replacement is 10B-lined proportional counters. Simulations are being performed to predict the performance of systems designed with 10B-lined tubes. Boron-10-lined tubes are challenging to model accurately because the neutron capture material is not the same as the signal generating material. Thus, to simulate the efficiency, the neutron capture reaction products that escape the lining and enter the signal generating fill gas must be tracked. The tube lining thickness and composition are typically proprietary vendor information, and therefore add additional variables to the system simulation. The modeling methodologies used to predict the neutron detection efficiency of 10B-lined proportional counters were validated by comparing simulated to measured results. The measurements were made with a 252Cf source positioned at several distances from a moderated 2.54-cm diameter 10B-lined tube. Models were constructed of the experimental configurations using the Monte Carlo transport code MCNPX, which is capable of tracking the reaction products from the (n,10B) reaction. Several different lining thicknesses and compositions were simulated for comparison with the measured data. This paper presents the results of the evaluation of the experimental and simulated data, and a summary of how the different linings affect the performance of a coincidence counter configuration designed with 10B-lined proportional counters.