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A historic data set containing unpublished measurements of 137 Cs (radiocesium) in 238 pooled samples of pectoral muscle from 1892 birds representing 37 species was analyzed in order to determine if (i) birds were contaminated due to global weapons fallout and/or the Chernobyl accident, (ii) to understand baseline 137 Cs levels in birds across the country by examining potential effects of trophic position and geophysical region, and (iii) to determine if the harvested birds were safe to eat. Current work is taking advantage of this data set to improve capabilities to assess the impacts of releases of radionuclides on food chains of species harvested as country food. Samples obtained from 173 locations across Canada (including locations in the Arctic), mostly during the fall hunting seasons between 1989 and 1995, were analyzed by gamma spectrometry and decay-corrected for the date of collection. Various methods of correlating measurements with environmental 137 Cs levels and species' habits were explored in order to determine environmental radiological transfer factors. All 137 Cs measurements in the samples were much lower than the Health Canada (2018) guidance level for 137 Cs (1000 Bq kg -1 ); therefore, there was no evidence of a human health risk with respect to radiocesium. Environmental transfer factors for six different foraging groups were determined., (Crown Copyright © 2020. Published by Elsevier Ltd. All rights reserved.)

Concern from northern communities following the Fukushima Daiichi nuclear accident of March 2011 has prompted a reassessment of the safety of their traditional foods with respect to radioactivity levels. To this end, a study was conducted to measure the levels of radionuclides in Arctic caribou (Rangifer tarandus) and beluga (Delphinapterus leucas). The main radionuclide of concern is cesium-137, which is easily transferred through the lichen-caribou food chain. Previous studies have been conducted on the cesium-137 levels in Canadian caribou herds from 1958 to 2000, allowing researchers to determine the amount of cesium-137 in caribou specifically attributable to atmospheric weapons testing and the Chernobyl nuclear accident in 1986. In this study, samples of lichens, mushrooms, caribou, beluga and beluga prey collected before and after the Fukushima accident were analyzed for radioactivity levels. Samples were processed and measured using gamma ray spectroscopy to identify the radionuclides present and determine the radioactivity concentration. Both calibration standards and Monte Carlo simulations were used to determine the efficiency of the detectors for the samples, taking into account differences in individual sample sizes as well as matrices. In particular, a careful analysis of the atomic composition of lichens and mushrooms was performed to ensure the efficiencies for these sample types were correct. A comparison of the concentrations from before and after the accident indicated that there was no increase in radioactivity as a result of the atmospheric plume from the Fukushima accident. Some cesium-137, likely attributable to fallout from atmospheric weapons testing of the 1950s and 1960s (since there was no cesium-134 measured in the samples), was measured in the post Fukushima caribou and beluga whale samples; however, this amount was determined to be insignificant for any radiological concern (9.1 ± 1.8 and 0.63 ± 0.23 Bq kg -1  ww respectively). The activity concentrations of cesium-137 was about 200 times smaller than that of natural radioactive potassium in the beluga samples. Both the caribou and beluga results showed that these foods continue to be a healthy food choice for northern Canadians with respect to radioactivity, and this result has been communicated to the nearby northern communities and stakeholders., (Copyright © 2016. Published by Elsevier Ltd.)

Since 2001 a real-time radiation monitoring network of Canadian nuclear facilities and major population centres has been implemented for response to nuclear incidents including a possible terrorist attack. Unshielded NaI(Tl) spectroscopic detectors are employed to measure gamma radiation from airborne radioactivity and radioactivity deposited on the ground. These detectors are composed of a standard 3''x3'' cylindrical NaI(Tl) spectrometers with data storage and integrated telemetry. Some of the detectors have been deployed in the Ottawa Valley near Chalk River Laboratories and Ottawa, which has a complex radioxenon environment due to the proximity of nuclear power reactors, and medical isotope facilities. Although not a health threat, these releases have provided an opportunity for the Canadian Meteorological Centre and the Commissariat à l'Energie Atomique to validate their meteorological models. The meteorological models of the two organizations are in good agreement on the origin and the source terms of these releases.

In preparation for verification of the Comprehensive Nuclear-Test-Ban-Treaty, automated radioxenon monitoring is performed in two distinctive environments: Ottawa and Tahiti. These sites are monitored with SPALAX (Systeme de Prelevement d'air Automatique en Ligne avec l'Analyse des radioXenons) technology, which automatically extracts radioxenon from the atmosphere and measures the activity concentrations of (131m,133m,133,135)Xe. The resulting isotopic concentrations can be useful to discern nuclear explosions from nuclear industry xenon emissions. Ambient radon background, which may adversely impact analyser sensitivity, is discussed. Upper concentration limits are reported for the apparently radioxenon free Tahiti environment. Ottawa has a complex radioxenon background due to proximity to nuclear reactors and medical isotope facilities. Meteorological models suggest that, depending on the wind direction, the radioxenon detected in Ottawa can be characteristic of the normal radioxenon background in the Eastern United States, Europe, and Japan or distinctive due to medical isotope production.

A new technique, full neutrino momentum reconstruction, is used to set limits on the admixture of heavy neutrinos into the electron neutrino. We measure coincidences between nuclear recoils and positrons from the beta decay of trapped radioactive atoms and deduce the neutrino momentum. A search for peaks in the reconstructed recoil time-of-flight spectrum as a function of positron energy is performed. The admixture upper limits range from 4 x 10(-3) to 2 x 10(-2) and are the best direct limits for neutrinos (as opposed to antineutrinos) for the mass region of 0.7 to 3.5 MeV.

A worldwide monitoring system for radioactive aerosols is being implemented for verification of the Comprehensive Test Ban Treaty. These 80 stations will detect airborne radioactivity not only from nuclear explosions but also from other anthropogenic and natural sources. A prototype unit has been in operation since April 1996 in Vancouver, British Columbia, Canada. It is a very sensitive system and reports clear signals for natural radioactivity, including cosmogenic 7Be, and the decay products from soil exhalation of 220Rn (thoron). In addition, there have been frequent detections of anthropogenic nuclides, probably coming from three distinct facilities-a medical isotope production center, a major university hospital, and a particle accelerator laboratory--all between 1 and 2 km away from the monitoring station. This experience is discussed to sensitize health physicists to the potential uses of this publicly available information.