Year
2011
Abstract
Users have identified the problem that demand for 3He gas has far exceeded gas supplies and is projected to continue because of the reduced supply from the decay of tritium. It is essential to find replacement neutron detectors functioning as well or better than the 3He gas based detectors. Precision Data Technology’s (PDT) new patent pending Boron-10 (10B) hybrid systems are an effective solution for the important radiation portal monitoring industry needs including large scale systems. For decades, gas proportional detectors using 10B lining on the inner walls have been available. The neutron self-shielding in the 10B in the wall lining is mitigated by the hydrogen in the HDPE plates that continuously convert fast neutron to thermal neutrons. Monte Carlo MCNP simulations help optimize the thickness of the 10B wall deposit. This new narrow plate design (~ 5mm-thick) minimizes the parasitic loss of thermal neutrons to hydrogen capture because the 10B capture reactions are dominant. Preliminary MCNP calculations identifies optimum 10B deposit thickness and increases in efficiency as a function of the number of boron coated plates. As expected, the efficiency increases with the number of plates in a non-linear fashion in that the 6 plate design has 3x the efficiency of the 1 plate design. This is a result of the thermal-neutron self-shielding in the multiple 10B layers. However, the internal hydrogen innovation significantly reduces the problem by scattering neutrons into the thermal-energy region throughout the volume of the detector. The charged particle absorption loss in escaping from the 10B deposit was calculated using the MCNP code that tallied both the alpha particles and the Li-7 ions. The absorption losses for the charged particles are independent of the number of plates. Whereas, the thermal-neutron self-shielding in the 10B increases as the number of plates increase. Of particularly interested is this new technology’s implementation is the reduced manufacturing expenses hence a realized cost effective solution for efficient 10B detector systems as a 3He replacement. PDT’s new 10B detector system consists of a fully integrated hermetically, including supporting electronics, sealed systems intended for common industrial neutron assay for harsh environments.