Particle Detection - A New Mindset MACTEC's Detector Research and Testing Facility

Alejandro U. Lopez, Michael R. Marcial, and Michael P. McDonald, MACTEC Development Corporation, Grand Junction, CO

ABSTRACT:

MACTEC Development Corp. was contacted by a client with a unique radiological point source contamination problem. The client specified a need for an open-land survey system that could effectively detect discrete point sources of 137Cs with an activity of 105Bq in real time buried to a minimum depth of 100 millimeters in beach sand. In an effort to reduce research and development costs, MACTEC constructed a research and testing facility to develop, demonstrate, and document a successful radiological point source detection system. The facility was designed to accommodate the multitude of critical variables associated with optimizing an open-land particle detection system including detector type and size, detector orientation, detector height from surface, depth of radioactive particle in beach sand, detector velocity, particle to detector geometry (off axis), and background radiation interference. This paper presents the processes involved in the design and construction of the Detector Research and Testing Facility, and the analytical data generated during the testing and optimization phases of the particle detection system. MACTEC successfully demonstrated the capabilities of the system by meeting and beating the identified specifications, while saving significant costs that would be incurred with a full-scale test deployment methodology.

 

INTRODUCTION

The capability to detect dispersed or diffuse environmental residual radioactivity in surface soils and sediment, is well understood within the Health Physics community, and many guidance and informational documents on this topic are available. For example, minimum detectable concentrations, detector survey movement rates, and detector to surface distances are all well understood and are easily determined by calculation for the soil or sediment survey at hand. When attempting to locate discrete particles of radioactive material in soil or sediment, especially in larger environmental settings (e.g., multiple acres of land surface), the well- understood dispersed residual radioactivity surveying methodology fails to adequately address several important issues.

 

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