The below is part three of a five-part series detailing the history of Canada’s nuclear industry written by Michael Alexander Sinclair. It was originally submitted as an essay on November 15, 2017 for Ryerson University’s HST 701: Scientific Technology & Modern Society, and has since been modified for publication onto the Mackenzie Institute website.
The National Research eXperimental, NRX, reactor first achieved criticality on July 22, 1947. Located on the same site as ZEEP, it was another heavy water moderated reactor designed to use natural uranium fuel. In comparison to the moderate single watt ZEEP however, NRX was capable of producing up to 42 Megawatts (MW) and produced the a scientific term used to describe the number of neutrons traveling through a specific area in a specific amount of time, which allowed Canadian scientists to conduct research not possible anywhere else in the world. This major scientific achievement was essential for Canada to research nuclear fuels, materials, and components for the future CANDU reactors.
Shortly after NRX was commissioned, another even more important research reactor was built, again at the Chalk River site. The National Research Universal (NRU) reactor went critical on November 3, 1957, and was capable of outputting up to 135 MW, which was over three times more power output than the NRX. Originally designed to use heavy water moderation with natural uranium, it was later converted to use highly-enriched uranium in 1964, and then again converted to use low-enriched uranium in 1991. At the time of its construction, nothing in the world could compare to the NRU in terms of size, power, flexibility, and the way that it met the needs of industry, medicine and scientific research at the same time. It was a major research catalyst, which brought Canada to the leading edge of international science, and not just in nuclear applications. NRU, in conjunction with NRX, yielded results in metallurgy, solid state physics, chemistry, biology, electronics, and information technology. Due to the fact that neutrons do not have any charge, they are a valuable tool capable of creating images of the interior structures of materials as they can penetrate even dense materials. By measuring how neutrons scatter as they pass through materials, internal images can be produced. This type of imaging is called neutron spectroscopy, a term coined by the scientific field’s pioneer, Canadian physicist Bertram Brockhouse who was awarded the 1994 Nobel Prize in physics for his fundamental research at Chalk River in neutron scattering. Some of the vast amounts of materials studied in NRU are metals, bio-membranes, plastics, composites, minerals, glasses, semi-conductors, ceramics and even ice. It has also served industrial manufacturers as the neutron imaging can be used to check for internal stresses or cracks in things such as critical pipe welds, jet turbine blades, and car engines. Measurements made in NRU have even helped to determine why some structural failures occurred including the space shuttle Challenger accident of 1986.
The neutron spectroscopy methods and technology developed at Chalk River has led to the development of the Canadian Institute for Neutron Scattering (CINS), an organization of scientists with over 400 members across Canada as well as 22 other countries. The CINS supports 35 Canadian universities as well as industrial sectors including aerospace, automotive, biotech, mining, oil and gas, and electronics manufacturers in the research of advanced materials including alloys, membranes, nano-structures, superconductors, and corrosion at interfaces. The research conducted within NRU has developed Canadian expertise in the development of new materials for industrial, medical and scientific purposes.
NRU was, of course, also a critical part of developing CANDU reactors, especially due to its for experiments. The cylindrical tank, composed of aluminum, that contains NRU’s core is 3.7 metres tall with a diameter of 3.5 metres. The core consists of 227 vertical lattice sites, only half of which contains control rods and enriched uranium fuel bundles, leaving the other half for irradiation tests and other experiments. This is in addition to two high pressure and high temperature experimental loops and six neutron beam tube facilities. The ability to perform full scale fuel tests under active power reactor conditions allowed Canadians to accurately predict how their fuel designs would work within CANDU reactors. This allowed researchers to better predict how designs would perform in real life situations and increased the safety with which nuclear reactors could be designed and operated.
Even to this day, NRU’s capability to perform full scale fuel tests is something not easily reproduced in other research reactors across the globe. The Halden research reactor located in Norway operated under the Nuclear Energy Agency (NEA), a specialized branch of The Organization for Economic Co-operation and Development (OECD), for example can only perform partial tests that are then fleshed out with computer simulations. The flexibility provided by NRU’s design allowed complementary experiments to be performed that were particularly important in predicting how reactors behave as they age. The Osiris research reactor in France, as another example, can perform some of these tests, but not all of the essential experiments required to confidently predict aging reactor conditions. NRX was shut down in 1992, and NRU currently resides in a safe shutdown state, no longer actively operating as of March 2018. The achievement of building globally renowned, unique research reactors and the resulting research and development born from them that has affected so many important scientific fields are yet more great contributions to the world from the Canadian nuclear industry. However, it would be impossible to ignore the larger contribution to the world from these reactors: the production of life-saving medical isotopes.
Stay tuned for part four of five coming soon.