Detection sensitivity comparison of centrifugally tensioned metastable fluid detector vs Ludlum-42-49B (TM) for shielded & unshielded neutron source configurations

This paper presents results of neutron detection sensitivity between a similar to 2.5 kg, non-borated Centrifugally Tensioned Metastable Fluid Detector (CTMFD) as compared to a commercial state of the art moderated, 4.5 kg He-3 based Ludlum (42-49B (TM)) neutron detector of similar form factor. The study used: a collimated 1 Ci plutonium-beryllium (alpha, n) neutron source emitting 2.2 x 10(6) n/s. Water, concrete and lead shielding materials of thicknesses ranging from none to up to 0.3 m were used. The CTMFD as deployed was configured for detection of fast energy neutrons. Monte Carlo N-Particle Transport (MCNP) code-based simulations were conducted to account for 3-D effects and for computing cpm/mrem/h sensitivity estimates. At 0.6 MPa (6 bar) negative pressure (Pneg) state, and without benefiting from detecting epithermal neutrons, the CTMFD was found to offer up to similar to 5 + times higher cpm/mrem/h sensitivity vs the Ludlum-42-49B. At Pneg similar to 1.1 MPa (11 bar) the gain exponentially rises to similar to 100x higher for the CTMFD vs Ludlum-42-49B.