People working in the Canadian nuclear industry, past and present, are quite familiar with heavy water, or deuterium oxide as it is technically known. Deuterium is actually quite abundant on earth – the only problem is that in nature it is quite dilute. Typically, the ratio of deuterium to normal hydrogen in water is 145 parts per million. That means Lake Superior alone contains the equivalent of approximately 1,800,000,000,000 liters of heavy water, and even the average human body (~40 liters of water) contains around 6 grams of deuterium.
US scientist and Nobel laureate Harold Urey discovered deuterium in 1931. Lew Kowarski and his colleagues at the College de France (Paris) recognized the great advantage of using heavy water as a moderator for nuclear reactors in late 1939. One problem, however, was the scarcity of high-purity heavy water, which until then was simply a research curiosity. Only one source was available, a Norsk-Hydro hydroelectric plant at Vemork, Norway. German scientists working on nuclear weapons research also recognized the value of this material, so the French planned to purchase the existing world supply (about 165 liters, 185.5 kg) and whisk it to Paris.
Norway was still a neutral country in early 1940, so the “Deuxième Bureau de l’État-major general”, the French external military intelligence agency, sent “Monsieur Jacques Allier [who] is empowered by the Prime Minister to negotiate with the party holding the material that is the object of his mission to assure for France the availability of the largest quantities thereof”. The general manager of Norsk Hydro Axel Aubert “decided to lend free of charge the entire stock of 185.5 kilos to the French government; after the end of the war, it would have the choice of either purchasing or returning it”.
Allier pretended to load the heavy water on a flight from Oslo to the still-neutral Netherlands; the flight was forced to land in Hamburg, by the Luftwaffe. However, the heavy water was actually flown from Oslo to Scotland; it arrived at the College de France on 1940 March 18, three weeks before Norway was invaded. Several movies and books have described later Allied attempts to sabotage heavy water production at the Norsk-Hydro facility, to prevent the Germans from acquiring a supply for their reactor research programs. The Free-Norwegian commando operations were spectacularly successful.
After France was invaded in May 1940, the Norsk-Hydro heavy water was hurriedly shipped to Cambridge University in the UK. In 1943 it travelled to Canada and was used in small-scale experiments at Montreal and Chalk River, and presumably in the start up of ZEEP. Additional heavy water was urgently needed, but Canadian authorities discovered that the USA had secretly paid for Cominco to set up a plant in Trail, B.C., and had contracted for the entire output of the newly-constructed plant. In the end, this did not end up as a major problem as the USA supplied Canada with its initial needs.
The need for a Canadian source of heavy water became more urgent as AECL and Ontario Hydro began to build its fleet of CANDU reactors in the 1960s. An influential federal cabinet minister, Allan MacEachen, was able to convince his cabinet colleagues that the best place to build heavy water production facilities was in his home province of Nova Scotia. Two plants were built there but quickly encountered a number of unforeseen problems. Only through the efforts of a Chalk River team led by Alistair Miller and Howard Rae were they eventually able to produce a significant supply.
Ontario Hydro, anxious about the problems at the Nova Scotian plants, built its own large heavy water facilities at the Bruce site on Georgian Bay. Th two large units greatly eased both the Canadian and the export supply concerns. As the slowdown in nuclear plant construction began to take hold in the 1980s, the need for heavy water decreased; after building up a significant inventory, all the plants in Canada were shut down.
About this time, new uses for heavy water appeared. The Sudbury Neutrino Observatory (SNO) proposed to use heavy water as the detection material for settling a long-standing neutrino mystery. They approached AECL for the loan of many tonnes of the material and, with the enthusiastic response of Ara Mooradian of AECL, the SNO was able to borrow 1000 tonnes for their successful experiments; this led to the awarding of the Nobel Prize in Physics to ex-AECL physicist Art McDonald.
Two additional industrial applications of heavy water also surfaced around that time. One is in the manufacture of fiber optics. During manufacture of the glass fibers, a small amount of water ends up in the material and unfortunately one of the hydrogen absorption bands interferes with and limits the band width of the fibers. Removing the “protium” and replacing it with deuterium fixes the problem.
The second application is in the manufacture of silicon chips for electronic circuits. The chips tend to degrade with time and have in the past had the surface “pacified“ with an exposure to hydrogen to improve lifetimes. Preliminary results suggested that using deuterium to replace the normal hydrogen might further improve the lifetimes. The result was a spectacular success with a lifetime improvement of greater than ten. Details of the chemistry are not yet fully understood.
The Society for the Preservation of Canada’s Nuclear Heritage welcomes visitors to its artifacts collection. Included in the collection are several small samples of heavy water as well as models and documentation on the production of the material. Contact one of the Society Board or info@nuclearheritage.com to arrange a personal, family or group tour.
