Observing Radioactivity in a Cloud Chamber 1954 Chalk River Canada

The cloud chamber is a particle detector used for detecting ionizing radiation. In its most basic form, a cloud chamber is a sealed environment containing a supersaturated vapor of water or alcohol. When a charged particle (for example, an alpha or beta particle) interacts with the mixture, it ionizes it. The resulting ions act as condensation nuclei, around which a mist will form (because the mixture is on the point of condensation). The high energies of alpha and beta particles mean that a trail is left, due to many ions being produced along the path of the charged particle. These tracks have distinctive shapes (for example, an alpha particle's track is broad and shows more evidence of deflection by collisions, while an electron's is thinner and straight). To build your own cloud chamber, visit http://teachers.web.cern.ch/teachers/document/cloud-final.pdf . This is clipped from the 1954 episode Hidden Power, from the On the Spot television series from the 1950s. The episode is a visit to the Chalk River NRX Canadian atomic energy plant, showing research in the peacetime application of nuclear energy. At the time of its construction it was Canada's most expensive science facility and the world's most powerful nuclear research reactor. NRX experienced one of the world's first major reactor accidents in December 1952 when the NRX reactor underwent a violent power excursion that destroyed the core of the reactor, causing some fuel melting. The entire film is available at the US National Archive in College Park, Maryland and describes NRX, the atomic reactor, and shows investigations of the production of radioactive isotopes and their use in such fields as industry, medicine and forestry. NRX was a heavy water moderated, light water cooled, nuclear research reactor at the Canadian Chalk River Laboratories, which came into operation in 1947. The NRX operated for 45 years, being shut down permanently in 1993. It is currently undergoing decommissioning at the Chalk River Laboratories site.

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