Abstract
Boron-coated straw (BCS) detectors can be easily and economically manufactured in large volumes, to replace <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> He-based detector modules in Radiation Portal Monitors (RPMs). A neutron detector module (NDM) design based on BCS detectors is presented, maintaining the outer dimensions of the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> He-based NDM in current installations. Multiple (up to 95) BCS detectors are distributed in an array, within a high-density polyethylene moderator block. Each BCS detector is 4.43 mm in diameter, 200 cm long, and individually sealed inside an aluminum tube just large enough to contain the thin walled straw. Straws are organized into 5 rows at different depths within the moderator. The response of five production NDM units to a neutron and gamma source are presented, together with environmental testing aimed to simulate operating conditions encountered in typical RPM applications. The mean neutron absolute efficiency measured at 2 m among 4 units was 3.55±0.06 cps/ng for a moderated <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">252</sup> Cf source, and 3.13±0.08 cps/ng for an unmoderated source. The mean gamma-ray efficiency measured was 1.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> for an exposure rate of 20 mR/hr, and 1.4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> for 50 mR/hr. The background rate was 2.5 cps at sea level in Houston for all units. Environmental tests showed stable operation over the temperature range from -40°C to +49°C, and during an 18 hour soak at 40°C and 98% relative humidity. Advanced capabilities of the NDM include coincidence/multiplicity counting for characterization of spontaneous fission sources, and encoding of the location of neutron interactions along the depth of the NDM.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
