Performance of a EJ309 organic liquid scintillation detector pedestrian radiation portal monitor prototype at the 2nd SCINTILLA benchmark campaign

Year
2014
Author(s)
S. D. Clarke - Department of Nuclear Engineering & Radiological Sciences, University of Michigan
S. D. Clarke - Department of Nuclear Engineering & Radiological Sciences, University of Michigan
S. A. Pozzi - Department of Nuclear Engineering & Radiological Sciences, University of Michigan
S. A. Pozzi - Department of Nuclear Engineering & Radiological Sciences, University of Michigan
M. Paff - Department of Nuclear Engineering and Radiological Sciences, University of Michigan
M. Paff - Department of Nuclear Engineering and Radiological Sciences, University of Michigan
P. Peerani - Joint Research Centre, Ispra, Italy
P. Peerani - Joint Research Centre, Ispra, Italy
M. Ruch - Department of Nuclear Engineering and Radiological Sciences, University of Michigan
M. Ruch - Department of Nuclear Engineering and Radiological Sciences, University of Michigan
A. Sagadevan - Department of Nuclear Engineering and Radiological Sciences, University of Michigan
A. Sagadevan - Department of Nuclear Engineering and Radiological Sciences, University of Michigan
Abstract
The University of Michigan has developed a pedestrian radiation portal monitor (RPM) prototype incorporating eight 7.62 cm diameter by 7.62 cm length EJ309 organic liquid scintillation detectors. The excellent pulse shape discrimination of these detectors enables the RPM to trigger an alarm on user-defined net gamma and neutron count rate thresholds (five s over background). Radionuclide identification is achieved through a least squares regression comparison of the approximately 3 s measured photon pulse height distributions with longer hard-coded spectra of a library of radionuclides. These 3 s pulse height distributions consist solely of Compton scattering contributions and have poor counting statistics. Nevertheless, by applying weighting masks, noise suppression, operating some detectors at higher/lower gains, and several other techniques, excellent identification capability has already been demonstrated. The system can reliably identify 137Cs, 57Co, 60Co, 241Am, 226Ra and 133Ba (source strengths vary from ~5-50 µCi) at 100 cm source to RPM distance. The RPM will not false alarm on neutrons due to misclassification when a 20 µSv/h gamma effective dose is applied. It can also detect with high probability a ~20,000 n/s 252Cf source shielded by 8 cm of high density polyethylene at a 100 cm source to RPM distance. The SCINTILLA project is a consortium of European research laboratories and companies with a vested interest in alternative RPM designs, especially in light of the 3He crisis. The annual benchmark campaign at the European Commission Joint Research Centre in Ispra, Italy, provides developers of prototype RPMs the opportunity to test their designs on static and moving (1.2 m/s for pedestrian RPM) sources in a purpose-built facility for their gamma and neutron response characteristics, ability to perform radionuclide identification including special nuclear material and their susceptibility to false alarms. The benchmark campaign is scheduled for February 2014, yet aforementioned preliminary tests with sources available at the University of Michigan exhibited positive and encouraging results for the prototype RPM.