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In the mid-1980s AECL (Atomic Energy of Canada Ltd.), originally as part of a joint project with Los Alamos National Laboratory, developed a design for a small, passively-cooled nuclear power supply called the "Nuclear Battery". The project's initial mandate was to supply compact energy systems for the unattended short-range radar stations in the new North Warning System (NWS), but this was cancelled due to a mismatch between projected development schedule and deployment requirements. AECL continued the development with a new goal of an air-independent auxiliary power source for Diesel submarines, as part of the Canadian Submarine Acquisition Project (CASAP). When CASAP opted for full-powered nuclear submarines of conventional design, AECL again refocused its development program - this time towards a more powerful model that could supply local-area electricity or high-grade steam. (Note: the federal government eventually cancelled CASAP.)
The term "Nuclear Battery" was chosen to highlight the passive and solid-state features of the concept, and distinguish it from conventional water-cooled reactor design. The core features a block of graphite filled with about five hundred fuel rods, and penetrated by heat pipes that passively remove heat to a secondary working fluid. Heat from nuclear fission is conducted through the graphite to the heat pipes, where it evaporates a primary working fluid that flows up the heat pipe and out of the core. At this point the primary fluid gives up its energy to the secondary fluid, condenses, and flows back into the core. This process in entirely passive (i.e., does not require pumping and external energy).
The fuel consists of "TRISO" coated fuel particles (20%-enriched UO2 "kernels" 0.5 mm in diameter, coated with layers of graphite, pyrolytic carbon, SiC ceramic, and a second layer of protective pyrolytic carbon - final outer diameter is 0.9 mm). The TRISO design was developed for the high-temperature gas-cooled reactors (HTGRs) and demonstrated in the Ft. St. Vrain reactors in the USA, and in the AVR and THTR reactors in West Germany. These tiny particles were embedded in a solid graphite rod that served as moderator and conduction medium to the surrounding graphite block (and thence to the heat pipes).
The reference design for the Nuclear Battery could produce 600 kWe net electricity via a Rankine cycle engine coupled to the heat pipes, and this production could continue uninterrupted (without refuelling) for 15 years. Alternatively, the unit could produce high-pressure steam at 2400 kW for that length of time. The overall dimensions of the reference unit were 2.5 m in diameter, and 2m high.
Source: K.S. Kozier and H.E. Rosinger, The Nuclear Battery: A Solid-State, Passively-Cooled Reactor for the Generation of Electricity and/or High-Grade Steam Heat, AECL Report AECL-9570, 1988.
See also an editorial by the author.
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Imagine digging down two kilometres into the Canadian Shield, to get a better look at the sun. That is the aim of the Sudbury Neutrino Observatory (SNO).
The sun, and all stars in the universe, are powered by nuclear fusion, the process of joining light nuclei (e.g. hydrogen) together, with a net release of energy (as opposed to nuclear fission, the splitting of heavy nuclei (e.g. uranium) with a net release of energy). Scientists have attempted to describe the incredibly complex, multi-stage fusion process that rages beneath the sun's surface. One prediction of these theories is the release of neutrinos as a "by-product" of the fusion process, at the rate of 200 trillion trillion trillion (2x1038) per second. Since neutrinos can travel through almost anything put in their way, here on earth we should see streams of neutrinos coming from the sun's general direction. Past experiments around the world have detected these neutrinos, but in smaller amounts than the theories predict - a "neutrino deficit".
This is where the SNO project comes in. In order to study neutrinos in an environment free of interfering cosmic ray radiation, a huge neutrino detector was built almost two kilometres underground in an off-shoot of a nickel mine in the Canadian Shield near Sudbury, Ontario. Within a 22-metre underground cavity, a 12-metre diameter acrylic (plastic) sphere contains over 1000 tonnes of heavy water on loan from Atomic Energy of Canada Ltd. (AECL). Of the trillions of neutrinos that will pass through the heavy water each day, about 20 will interact with the molecules of heavy water and create a brief (and faint) flash of light. These light flashes will be picked up by an array of 10,000 photocells surrounding the acrylic sphere.
This is an important experiment that will hopefully answer many questions about not only the inner workings of our own sun, but the origins and makeup of the universe itself. The official opening of SNO was April 29, 1998. For more information, several participating organizations have created websites, with diagrams and other interesting material:
| LATEST NEWS:
Monday, June 18, 2001:
The SNO researchers announced, a little over three years after the
official opening, the first official results of their experiment. The SNO
study has shown that there is no discrepancy in the quantity of neutrinos
reaching the earth; rather, the type of neutrinos created in the Sun have
a mass and can change from one variety to another along the journey to
Earth.
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Canada has been a world-leader in the medical applications of nuclear energy since the start of its nuclear program. Canada pioneered the Cobalt-60 cancer therapy technology that became standard medical practice throughout the world (the first Cobalt-60 cancer therapy was administered at the Royal Victoria Hospital in London, Ontario on October 27, 1951), and has also been involved in the development of accelerator-based cancer therapy technology. Currently, about 85% of the world's medical and industrial Cobalt-60 is produced in Canada. The medical-use Cobalt-60 is produced in the NRU research reactor at AECL's Chalk River Laboratories, while industrial-use Cobalt-60 is produced in selected CANDU power reactors (in these units some adjuster rods are made of Cobalt-59 for this purpose). Furthermore, over half the Cobalt-60 therapy machines and medical sterilizers in the world were built in Canada, treating over 16 million patients yearly.
Canada is also a leader in the production of medical isotopes, including being the largest supplier of technetium-99m (derived from molybdenum-99), the most commonly-used medical isotope. Production is by AECL in the NRU reactor; this is then shipped to MDS Nordion, a global supplier of radiopharmaceuticals based in Kanata, Ontario (near Ottawa). There are more than 4000 Mo-99 treatments daily in Canada, and 40,000 daily in the US. Canada nominally produces about 30-40% of the global supply of Mo-99.
History
The use of radioactive sources to treat disease and other afflictions can be traced to the first discovery of radioactivity. For the first half of the 20th century, radium (a decay product of uranium) was particularly popular as a "cure-all" substance, beginning shortly after its discovery by Marie Curie in 1898. Radiotherapy did, in fact, produce real results in the treatment of localized tumours, and the science behind the phenomenon gradually gave it credibility as a valid tool in the fight against cancer. Following WWII, the development of powerful research reactors introduced for the first time the possibility of creating significant quantities of radioactive isotopes for science, medicine and industry. Canada's leadership in this field began at this same time with the start-up of NRX, for several years the world's most powerful and flexible research reactor. In 1945 Dr. J.S. Mitchell and other scientists at the NRC's Montreal Laboratory in Canada recognized the cancer-fighting potential of cobalt-60 (discovered in 1936 by Glenn T. Seaborg and John Livingood at the University of California - Berkeley). This isotope was an early contender for the new medical wonders that were expected to emerge from the NRX reactor, then two years from completion. It was clear to Mitchell and others that radium's days as the "cure-all" radioisotope were soon over. Radioisotopes were high priority for NRX once it started up in 1947. The first shipment of radioisotopes (cerium-144) was made to the University of Saskatchewan on October 31, 1947, three months after startup. By 1949, routine shipments of iodine-131 were being made to pharmaceutical companies, along with phosphorous-32 and sulfur-35 to university labs. A total of sixty different isotopes were in production at Chalk River, and hundreds of shipments had been made to two dozen research institutions in Canada and elsewhere. This included many orders for cobalt-60 at "moderate" strength (500-1500 mCi or 18-55 GBq). The real promise of cobalt-60, however, meant being able to create it at thousands of times greater strength and concentration, which would allow its powerful beams of radiation to be focussed onto deep-seated tumours – as yet unreachable by radioisotopes. In 1950, two requests for cobalt-60 of such high specific activity (in terms of absolute activity generally greater than 1000 curies or 37,000 GBq), came from two research teams: one under Dr. Harold E. Johns of the University of Saskatchewan, and one under Roy Errington of the Commercial Products Division (CPD) for Eldorado Mining and Refining Ltd. in Port Hope, Ontario. Shipments of the cobalt-60 sources were made in August 1951. The Eldorado CPD unit (built by Canadian Vickers of Montreal) treated its first patient (and the world's first) at Victoria Hospital in London, Ontario on October 27, 1951. The University of Saskatchewan unit (built by Acme Machine and Electric Company) treated its first patient at the University Hospital a couple of weeks later on November 8, 1951. Since 1949, Chalk River had actually been distributing all of its commercial cobalt-60 through Eldorado CPD. Eldorado had become a crown corporation during WWII, but began as a private gold mining company in 1927. Since the mid-1930s Eldorado had mainly been refining radium at its Port Hope plant, after its president Gilbert LaBine discovered uranium at Great Bear Lake in the Northwest Territories (radium is a decay product of uranium). In 1951 Chalk River's distribution deal with Eldorado CPD was extended to all isotopes generated in NRX, and in 1952 Eldorado CPD was transferred to Atomic Energy of Canada Ltd. (AECL), another crown corporation created that same year. In 1955 AECL's CPD consolidated its Chalk River and Port Hope operations at Tunney's Pasture in Ottawa, and by the mid-1960s the operation was producing about 100 cobalt-60 cancer therapy machines per year. Fuelling this increase in production was Chalk River's new NRU reactor (started in 1957), many times the power of NRX and designed, among other things, to produce isotopes as efficiently and quickly as possible. In 1972 AECL CPD, during an extended outage of the NRU reactor to replace its vessel, used the McMaster University Reactor (2-5 MW) to develop a process for extracting molybdenum-99 from irradiated fuel rods. When the NRU came back on-line in 1974 this process moved back to Chalk River Laboratories, where it has dominated the world of medical isotope supply ever since. Molybdenum-99 (commonly referred to as "Moly-99") decays with a 66.7-hour half-life to technetium-99m, which has a 6-hour half-life. Tc-99m is today the "workhorse" of nuclear medicine, used in almost 50,000 treatments daily around the world, and much of that at one time was supplied by the NRU reactor at Chalk River. Due to its short half-life, it was shipped along with its parent radionuclide, Mo-99, in "Tc-99m generators" (also called Tc-99m "cows") which were "milked" by technicians at hospitals to extract a required quantity of Tc-99m. The broad-based attraction of Tc-99m as a radiopharmaceutical lies partly in its relatively short 6-hour half-life (ideal for clinical applications) and its reasonably-energetic gamma ray emission (140 keV — powerful enough for external imagery without causing undue internal risk). Of key importance, however, is Tc-99m's decay by pure gamma emission. Most gamma-emitting radionuclides simultaneously emit short-range beta radiation that can cause complications with sensitive internal body tissues, but Tc-99m, as a metastable isomeric nuclide, emits zero beta particles. In addition to molybdenum-99 and cobalt-60, the NRU reactor produced xenon-133 (a direct byproduct of the moly-99 extraction process), as well as carbon-14, iridium-192, iodine-125, and iodine-131. In the 1970s and 1980s, as demand grew for "low-specific-activity" (LSA) cobalt-60 used for food irradiation (see related FAQ), sterilization, and other industrial purposes, AECL CPD contracted several CANDU utilities in Canada to irradiate cobalt in the adjuster rods of their reactors, a practice that continues today. The "cobalt" adjuster rods are manufactured with stable cobalt-59 in an arrangement designed to be neutronically equivalent to the stainless steel adjusters normally used in CANDU reactors. Since CANDU adjuster rods remain in-core most of the time (mainly for flux shaping and available Xe-override), this "bakes" the cobalt-59 in a high neutron flux for approximately two years. The first Co-60 was discharged from a CANDU reactor in 1974. In the early 1970s AECL CPD manufactured two Radioisotope Thermoelectric Generators (RTGs), which used the energy of cobalt-60's radioactive decay to generate electricity for remote applications. One RTG was installed in a lighthouse in Brockville, Ontario, and the other was used to power a weather station in Resolute, Northwest Territories. In 1978 AECL CPD (which since the late 1960s was known simply as "Commercial Products", and was soon to be renamed "Radiochemical Company", but for simplicity will continue to be referenced here as "AECL CPD") began investigating cyclotron-produced radioisotopes. Cyclotrons can make radioisotopes with different characteristics than those produced in a reactor; in particular the former tend to be proton-rich while the latter are neutron-rich. Processing facilities were constructed at the large TRIUMF cyclotron lab at the University of British Columbia (Vanvouver) in 1980, with production of iodine-123 planned initially. Hospitals shipments of radiopharmaceuticals generated in TRIUMF began in 1982-3, and AECL CPD became a leading global supplier of both the newer cyclotron-based and older reactor-based radioisotopes. Radioisotopes generated at the TRIUMF facilities include palladium-103, strontium-82, thallium-201, indium-111, gallium-67, cobalt-57, and iodine-123. Following the final shutdown of the NRU reactor in 2018, the main Canadian role in reactor-based medical radioisotope production shifted to the research reactor at McMaster University, which today produces iodine-125, lutetium-177, and rhenium-186. The Tc-99m supply disappeared from Canada's role after the NRU shutdown, but production of this important isotope in the Darlington CANDU reactors is being planned. In the late 1960s AECL CPD relocated to its present site in Kanata in the west end of Ottawa. In 1988 AECL CPD, which by the late 1960s had been relocated to modern facilities in Kanata in Ottawa's west end, was sold off as two separate companies: Nordion International handled the nuclear medicine business, and Theratronics International handled the radiotherapy business. Finally, in 1998 MDS Inc. purchased both companies, now operated under "MDS Nordion". In 2014 MDS Nordion was acquired by Sotera Health, and in 2018 the medical isotope business was sold off. The technical advantage of the NRX (and later NRU) reactor, the foresight of Canadian pioneer scientists, and the partnership of Canadian government and medical research community, conspired to place Canada continuously at the forefront of nuclear medicine development since the end of WWII. Although it evolved in parallel with other developments in the nuclear industry in Canada, including nuclear power, it can rightly be considered a "by-product" of the nuclear power industry since a significant portion of its supply infrastructure (Chalk River Laboratories, and the CANDU power plants performing cobalt irradiations) depended primarily upon that sector.References...
- "Canada Enters the Nuclear Age", Atomic Energy of Canada Limited, 1997.
- W. Eggleston, "Canada's Nuclear Story", Clarke, Irwin & Company Limited, Toronto, 1965.
- S. Fedoruk, "The Growth of Nuclear Medicine", Proceedings, Special Symposium: 50 Years of Nuclear Fission in Review, Canadian Nuclear Association & Canadian Nuclear Society, 1989.
- P. Gardner and A. Fong, "MDS Nordion and TRIUMF: Over 20 Years of Successful Collaboration", TRIUMF Financial Report 2001-2002.
- "Nuclear Isotopes", Ontario Power Generation website
- G.R. Malkoske, J. Slack, J.L. Norton,"Cobalt-60 Production in CANDU Power Reactors", Proceedings: 23rd Annual CNS Conference, Toronto, June 2002.
- "The Technetium-99m Generator", "Brookhaven History", Brookhaven National Laboratory website.
| MAPLE Isotope Reactors:
At the turn of the century AECL was constructing two new MAPLE isotope-production reactors (see related FAQ) that were intended to
replace the NRU's medical isotope production capability. By 2008 commissioning excercises had taken the MAPLE core to high power (8 MWth) and successfully tested many of the systems, including the safety shutdown system under conditions such as loss of power regulation. However, several first-of-a-kind technical issues significantly delayed the commissioning process, including regulatory concern over the power coefficient of the MAPLE core (discovered during commissioning to be small but positive).
On Friday, May 16, 2008, AECL announced that it had halted the development of the two MAPLE reactors at Chalk river Laboratories, citing future costs, risks, and changing market conditions beyond AECL's control. Instead, medical radioisotope production at AECL would continue for the forseeable future to utilize the NRU reactor at Chalk River Laboratories, and development resources would be focussed on both extending the life of that facility, and developing a mutually satisfactory plan with AECL's main medical radiosisotope custormer, MDS Nordion.
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| NRU Crisis - December 2007:
In December 2007 Canadian Parliament, in an unprecedented move, passed emergency legislation to return the NRU reactor to service after a lengthy shutdown, motivated by a siginificant shortage of Technetium-99m (Tc-99m) and other radioisotopes for nuclear medicine procedures world-wide (see related FAQ). The NRU was taken offline on November 18 by AECL when the crown corporation discovered that NRU was out of compliance with its operating license, due to certain safety upgrades not being installed. The upgrades improved the safety of the reactor by making it more resilient to major earthquakes; however, the matter leading to the reactor shutdown is an issue of license compliance and not safety: The NRU reactor met the safety requirements of its license (from the federal regulator, the Canadian Nuclear Safety Commission, CNSC) prior to August 2006, and during the first 49 years of its operation, but not the additional seismic-related safety requirements of its August 2006 operating license. In particular the reactor met the pre-2006 requirements for sufficient backup power supply to its cooling pumps (in the event of a loss of primary power supply), but not the more stringent post-2006 requirements for seismic qualification.
NRU was restarted on December 16, 2007. The issue led to the firing of the President of the CNSC in January 2008. All seismic safety upgrades were completed in the NRU by February 2008.
More info:
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Food Irradiation is a process for killing micro-organisms in food using radiation. When applied in prescribed doses to certain food products, the process reduces the risk of spoilage or poisoning, without altering the products' taste, texture, odour, or nutritional value. Food Irradiation has been approved for use in 40 countries, and is endorsed by health organizations such as the UN World Health Organization, the American Medical Association, the Institute of Food Technologists, the Science Council of Canada, Health and Welfare Canada, and the USA Food and Drug Administration.
Food Irradiation has certain advantages over conventional food preservation techniques. It doesn't leave additives in the product, as some chemical preservatives do. Fruits and vegetables retain their taste, texture, and nutritional value, unlike the results of conventional heating, freezing, additives, drying or powdering. It is proven effective in neutralizing common food-borne pathogens such as Campylobacter (for which it is the only known control in poultry meat), Cryptosporidium, E. Coli (for which it is the most effective control in ground beef), Listeria, Salmonella, and Toxoplasma.
As with the sterilization by radiation of medical and pharmaceutical products, which is common practice, Food Irradiation does not leave residual radioactivity in the treated product. The radiation is simply energy that passes through the food, kills bacteria and other micro-organisms, and dissipates. The only residual products are small amounts of food molecules within the food that have been altered by the passing energy. However, these "radiolytic products" have been tested by the FDA in the United States, and found to be the same or similar to the processing byproducts found in foods that have not been irradiated [1]. There is no food preservation process that does not leave traces of its use.
The radiation used to irradiate food can be in the form of X-rays, high-energy electrons, or gamma rays from Cobalt-60 or Cesium-137. Canada is a world leader in industrial irradiation technology, including being the largest global supplier of irradiators. Cobalt-60 is produced commercially in selected CANDU reactors (see related FAQ).
In Canada the following food items have been approved for irradiation: potatoes (sprout inhibition), onions (sprout inhibition), wheat and wheat flour (disinfestation), spices (decontamination), dried vegetable seasonings (decontamination), herbs (decontamination), and mangoes. The following food items are currently being reviewed in Canada for irradiation: chicken, red meat, shrimp, citrus, small fruits, fresh figs and dates, dried fruits and dried vegetables. [source: MDS Nordion]
Further information on Food Irradiation in Canada is available on the MDS Nordion website.
[1] "FDA Announces Approval of Meat Irradiation," Nuclear News, 40, 1, p.55, 1998 January.
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Fusion is a form of nuclear energy with the potential to liberate massive amounts of heat by forcing atomic nuclei together (fusion), rather than splitting them apart (fission). One of the most efficient fuels for fusion power is a mix of heavy hydrogen isotopes - deuterium and/or tritium - implying that ordinary water would become a primary fuel source (deuterium can be extracted from ordinary water - see related FAQ - while tritium can be bred directly from lithium by the fusion process itself). Aside from an abundant fuel source, fusion holds the additional promise of relatively clean operation, and relatively short-lived radioactive waste production.
Currently the science and technology of fusion power is in a highly developmental stage around the globe, largely due to the extreme conditions required to make fusion viable. Since the temperatures needed to bring hydrogen nuclei together are typical of those found on the Sun, a remarkable feat of engineering is required to both contain and control the fuel, as well as extract useful energy. The most promising concept is "magnetic confinement", which suspends the hot hydrogen fuel (in the form of an ionized plasma at such temperatures) within a strong magnetic field. The popular apparatus for achieving this confinement is a toroidal structure called a tokamak.
The cost of a comprehensive fusion research and development program exceeds the capabilities of most countries, including Canada. However, Canada is able to contribute to the greater international effort through its experience and expertise in the area of fusion fuels. This is because fusion fuels are, coincidentally, also associated with Canada's CANDU nuclear fission industry. Deuterium is the main component of heavy water, while tritium is a natural byproduct of fission in a heavy-water reactor like the CANDU design. This country has much to offer, therefore, in the area of the production, handling, and characterization of two of fusion's essential ingredients.
The bulk of Canadian fusion fuels research was conducted, until the loss of federal funding in 1997, under the Canadian Fusion Fuels Technology Project (CFFTP). Canada also had two experimental tokamaks, the tokamak de Varennes, operated until recently by the privately-funded Centre Canadien de Fusion Magnetique (CCFM) in Quebec, and the STOR-M tokamak still operated by the University of Saskatchewan.
The Next Step: Iter
Additionally, Canada was, until 2004, a partner in the Iter Project ("Iter", pronounced "eater", is Latin for "the way"), a multi-billion-dollar international proposal to build a prototype fusion reactor. Iter will demonstrate all the essential components, systems, and processes used in a full scale demonstration fusion power reactor. The subsequent demonstration step is scheduled to follow the Iter program, by about 2040.
The main players in the Iter project are the Japan, Russia, the
European Community (EU), the United States, South Korea, India, and China.
The benefits of locating ITER within Canada (the proposed site was next to the Darlington Nuclear Power complex on the shore of Lake Ontario about an hour east of Toronto, Ontario) included the availability of abundant real estate near a major workforce market, an existing service, electrical, and waste-management infrastructure on an existing licensed nuclear site, and a plentiful supply of fuel on-site – obviating the requirement to transport tritium. These advantages led to significant projected cost savings (measured in billions of dollars) if Iter had been sited in Canada.
Canada withdrew its participation in the Iter Project in 2004, after escalation of the competitor siting bids left Canada's bid in a non-competitive position. Canada's bid had been co-ordinated by Iter Canada, a consortium of private sector, labour, and government organisations.
In 2005 a decision was made to site ITER in Cadarache, in the south of France. Construction will continue for ten years, and operation is expected to last thirty years. The total cost of construction, operation, and decommissioning would be about €10 billion.
Further Reading...
- The Quest for Fusion Energy - a backgrounder prepared by the Toronto Branch of the Canadian Nuclear Society.
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