| Title | Tomographic reconstruction of a spatially-extended source from the perimeter of a restricted-access zone using a SCoTSS compton gamma imager |
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| Author | Murtha, N J ;
Sinclair, L E; Saull, P R B; McCann, A; MacLeod, A M L |
| Source | Journal of Environmental Radioactivity vol. 240, 106758, 2021 p. 1-10, https://doi.org/10.1016/j.jenvrad.2021.106758 |
| Image |  |
| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20210069 |
| Publisher | Elsevier |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Subjects | Health and Safety; Science and Technology; Radiation; Security |
| Illustrations | images; schematic diagrams; photographs; tables; spectra |
| Program | Canadian Hazard Information Service Nuclear Emergency
Response |
| Released | 2021 12 01 |
| Abstract | It is a standard procedure in many countries that response to a nuclear or radiological accident or incident would involve mobile aerial- or ground-based survey with highly sensitive gamma-ray detectors
to map the distribution of radioactivity. There may however arise situations in which ground- or air-based detectors are not able to access an area to survey for radioactive materials, therefore technologies and techniques that can estimate the
position and activity of radioactive materials from a distance are under development. Tomographic reconstruction methods, well-known in medical physics, permit the reconstruction of an N-dimensional map or image, from a number of N-1-dimensional
cross-sectional images, or back-projections. We are investigating a tomographic reconstruction method to reconstruct the radioactivity distribution within a restricted-access zone using measurements from a Compton gamma imager placed at several
locations around the perimeter of the zone. In this work an extended source of La-140 with an activity of 35 GBq was deposited within a 500 m by 500 m zone that was surveyed from the perimeter at six locations using a Silicon photomultiplier-based
Compton Telescope for Safety and Security (SCoTSS) gamma imager. The reconstructed Compton images from multiple viewpoints were then projected back into the zone to reconstruct the distribution of La-140 within it. This tomographic method
reconstructed high intensity along the known location of the La-140 source, suggesting that the method is able to localize the radioactive material. A simple fit to measured counts using a point-source approximation of the source distribution yielded
a strength estimate of (7 ± 2) GBq at time of deposition, a reasonable result given the presence of soil and snow attenuation. Our method provides an expedient estimate of the distribution of radioactivity using tomographic techniques. It may be used
to inform decisions made on the scene in urgent situations where the distribution of radioactivity must be reconstructed from a distance. |
| Summary | (Plain Language Summary, not published)
We made a camera for gamma radiation. We used this camera to measure a radioactive source from several positions on the perimeter of a restricted-access
zone. Using a technique similar to medical computed-tomography scans, we could reconstruct the distribution of the radioactivity inside the restricted-access zone. |
| GEOSCAN ID | 328320 |
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