Dose calibration of Health Canada's Fixed Point Surveillance system for environmental radiation monitoring in terms of air kerma and H*(10).

The environmental radiation exposure in Canada has been monitored since 2002 by Health Canada's Fixed Point Surveillance network. The network consists of over eighty 7.6 cm × 7.6 cm sodium iodide spectrometers, and routinely reports to the public the environmental gamma radiation level throughout Canada. This paper describes the latest dose calibrations to air kerma and ambient dose equivalent for the future upgraded network. The calibration curves were developed using Monte Carlo techniques and further optimized via experiments in various reference fields. The dose calibration was validated over a wide range of gamma energy, dose measurement range, and angle of incidence under laboratory conditions. In environmental monitoring situations, the angular distribution of radiation exposure was analytically calculated by assuming a semi-infinite plume source, semi-infinite planar source, and infinite volume sources for the respective exposure scenarios of radioactive plume, ground contamination, and soil source. By coupling the resultant radiation angular distribution with detector's angular variation on dose response, the overall accuracy of dose measurement in each of these environmental scenarios was estimated. The accuracy is expected to be within ±3.7% for plume radiation, -5.6% for 137Cs ground contamination, and 0% to -17.1% for soil radioactive sources. The under-estimation for soil sources is mainly caused by absorption of radiation in the electronic system underneath the crystal.

Calibration of Radiation Portal Monitors for Characterization of Historic Low-level Radioactive Waste.

Radiation portal monitors are large-volume radiation detectors typically positioned along roadways, railways, and pedestrian portals. They are typically used for the detection of radioactive material where no such material is expected. Applications include monitoring vehicles and personnel exiting nuclear facilities, at the entrance to steel and scrap metal facilities, and at international borders. As part of the Port Hope Area Initiative, the Port Granby Project involves the relocation of approximately 450,000 m of historic low-level radioactive waste, located at an existing site on the shoreline of Lake Ontario in Southeast Clarington, to a new, engineered aboveground mound. Ongoing maintenance and monitoring will continue for hundreds of years after the facility is capped and closed. The waste is transported from its current location about 700 m to the new facility using trucks. Each truck passes through a radiation portal monitor when travelling between the waste location and waste storage facility (both directions; empty and full). The radiation portal monitors have been calibrated to provide an estimate of the total radioactivity being deposited into the new waste facility. This paper describes the methodology and results of the calibration.

Airborne spectrometry: extraction of low energy γ-rays using two or three spectral windows.

Airborne γ-ray spectrometry with NaI(Tl) is a recognized tool for emergency mapping. The maps produced usually look for natural isotopes ((40)K, (238)U, (232)Th) and (137)Cs due to the Chernobyl accident. Nowadays a new thematic emerges as nuclear materials tracking. Such materials emitting at low energies require new algorithms and a new method is presented here based on counts observed in two or three spectral windows. Since altitude is an important factor to be taken into account, an improvement is proposed to follow flight altitude changes. An extension to medium energies is proposed and compared to windows methods and to peak detection.