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Neutron and Gamma Area Monitoring System Installed at Research Reactor
Posted on January 21st, 2016

A 25 channel area monitoring system was recently installed by RSCS at the Rhode Island Nuclear Science Center’s research reactor.  The system includes 11 neutron radiation area monitors (DRM-2EN), 11 gamma radiation area monitors (DRM-2E), 2 noble gas continuous air monitors (NGM-209M), and 1 particulate continuous air monitor (ABPM-209M).  All channels were supplied by Mirion Technologies. 

The neutron measurements are supplied with a newly designed DRM-2EN monitor using an external proton-recoil scintillator detector, manufactured by Ludlum (Model 42-41 Prescila probe).  All channels use microprocessor-based technology combined with telemetry for data transmission via the Mirion WRM2 wireless network for system integration with other existing detectors and sensors throughout the facility.

The DRM family of instruments are known for highly stable and accurate dose rate measurements of gamma radiation. This latest DRM-2EN model incorporates a Prescila probe to provide real time neutron measurements at the site.  The Prescila probe has a sensitivity of approximately 350 cpm per mrem/h (AmBe).  It detects neutrons with energies from thermal to 100 MeV, providing dose rate measurements from 0 mRem/h to 1,000 mRem/h. As both gamma and neutron radiation emissions are present at this research reactor, gamma rejection from the neutron channel is critical for the successful operation of the system.  Testing confirmed that gamma rejection is approximately 400 cpm (i.e. < 2 mRem/hr) when exposed to 100 mR/h gamma.  In addition, the angular dependence of the Prescila probe is within 15% across its’ specified neutron energy response range, making it useful for area monitoring applications.

This new DRM-2EN system is ideal for any environment where neutron dose is of concern, including reactors, cyclotrons and accelerators. 

To learn more about the Mirion Technologies DRM family of instruments, please click here.

For more information on the Ludlum Measurements Prescila probe, please click here.

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