Development of a light-weight portable neutron survey meter

Abstract

A light-weight portable neutron survey meter was developed using a mixed organic gas counter for dose management at nuclear power plants and accelerator facilities. This survey meter, NSN31041, is ~2 kg in weight and W160×H250×L300 mm(3) in size, which is capable of measuring neutron ambient dose equivalent rate from thermal to 15 MeV neutrons. The neutron energy response of the survey meter is evaluated using continuous energy neutron sources of (252)Cf, (241)Am-Be, thermal neutrons generated from a graphite pile loading a (252)Cf source, concrete-moderated neutrons of (241)Am-Be source and D(2)O-moderated neutrons of (252)Cf source. The measured response data show very good agreement with neutron ambient dose equivalent within a 50 % deviation.

A compact DD neutron generator–based NAA system to quantify manganese (Mn) in bonein vivo

“…In this project, the neutron yield was calculated based on MC simulations and NSN3 neutron detector results. From the previous work of Nunomiya et al (2011), we can confirm that this neutron detector is accurate at measuring dose from neutrons with energy ranging from 400 keV to 10 MeV, but can largely underestimate the neutron dose from 8 keV to 250 keV. With one side of the shielding open, the major contributor of the neutron dose was from 2.45 MeV neutrons (accounting for over 90% of the total neutron spectrum, as per the simulation).…”

“…This neutron survey meter uses mixed methane and nitrogen gas to measure fast neutrons based on elastic scattering reactions and thermal neutrons based on 14 N(n,p) reactions. The neutron ambient dose equivalent can then be obtained, taking into account the ICRP 74 (ICRP, 1997) neutron flux-to-dose equivalent rate conversion factors (Nunomiya et al, 2011). The NSN3 dosimeter’s mono-energetic and continuous energy response is within 50% difference from thermal to 15 MeV neutrons.…”

A Dosimetry Study of Deuterium-Deuterium Neutron Generator-based In Vivo Neutron Activation Analysis

“…Its design gamma rejection is such that at a gamma dose rate of 0.1 Sv h −1 , the NSN3 displays an apparent neutron dose rate of 0.01 mSv h −1 . Its design responses for both dose and angular response (all design neutron energies) were found to be ±25% (Nunomiya et al 2011). To measure ambient neutron dose equivalent, the NSN3 is placed outside the entirety of the moderator and shielding and used as a survey meter to obtain dose rates where the subject's trunk would be located during an IVNAA measurement.…”

Improvements to the Leake neutron detector III: Increased sensitivity and compliance with ANSI and IEC standards

“…Nunomiya et al [16] have developed a light weight meter, NSN31041, using a mixed organic gas counter, with no polyethylene moderator, that has a very low weight of 2 kg and can measure neutron ambient dose equivalent from thermal to 15 MeV. The meter measures fast neutrons above several hundred keV using elastic scattering of hydrogen and slow neutrons using the 14 N(n,p) 14 C reaction in the mixed organic gas counter: the signals are obtained from the protons produced in both cases.…”