Neutron standards and calibration services at the National Research Council Canada
Dr. John Paul Archambault | National Research Council CanadaEnoch ABC Ballroom
Neutron radiation is present in many laboratories and workplaces throughout Canada, such as nuclear power stations or radiation therapy clinics. Because radiation safety is of utmost importance to all users of these facilities, the National Research Council of Canada (NRC) offers a service to calibrate neutron survey meters. Neutron survey meters measure the ambient equivalent dose due to neutron radiation fields and are typically composed of a thermal neutron detector surrounded by a polyethylene shell. The shell is designed to moderate the neutron field, slowing down fast neutrons for detection in the thermal neutron counter. Neutron survey meters are calibrated at the NRC in a low-scatter laboratory using a well-characterised americium-beryllium (AmBe) neutron source. The large laboratory minimizes the effects of air-and room-scattered neutrons and enables the determination of a calibration coefficient which is independent of the facility characteristics. The presentation will cover the production of neutron radiation by an AmBe source and how the NRC determines the output of its neutron sources used in the survey meter calibrations. The unique, low-scatter neutron facility will also be described. This will be followed by a summary of how typical neutron survey meters are designed to work and an outline of the strategies and procedures the NRC uses during calibrations. Finally, the information typically found in a calibration report will be provided. The NRC calibration procedures adhere to ISO-8529: Neutron Reference Radiations Fields, the documents which guide the strategies for calibrating neutron survey meters and throughout the presentation, particular sections of the ISO-8529 documents will be highlighted by subject for easy reference.