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The Lucknow Sentinel, 2014-03-26, Page 1616 Lucknow Sentinel • Wednesday, March 26, 2014 aiji,eIs nwmo Ay' nwmo NUCLEAR WASTE SOCIETE DE GESTION MANAGEMENT DES DECHETS ORGANIZATION NUCLEAIRES Protecting People and the Environment: The Multi -Barrier System The long-term management of Canada's used nuclear fuel involves the development of a deep geological repository. It is a multiple -barrier system designed to safely contain and isolate used nuclear fuel over the long term. The design is based on the use of multiple durable barriers, including hundreds of metres of rock. This long-term management plan emerged from more than 30 years of scientific and technical studies conducted in Canada and internationally. Most countries with nuclear power programs have selected the deep geological repository as their preferred approach for managing used fuel; two countries (Sweden and Finland) have identified sites and are in the early stages of licensing. Q What is the multiple -barrier system? A. A series of engineered and natural barriers will work together to contain and isolate used nuclear fuel from people and the environment. Each of these barriers provides a unique level of protection. Barrier 1: The Used Nuclear Fuel Pellet — Used nuclear fuel is in the form of a ceramic pellet. It does not readily dissolve in water. Barrier 2: The Fuel Element and the Fuel Bundle — Sealed tubes contain the fuel pellets; these are called fuel elements. The tubes are made of a corrosion -resistant metal called Zircaloy. • Barrier 3: The Used Nuclear Fuel Container — Used fuel bundles will be placed into specially designed containers to contain and isolate the fuel. The container is designed with an inner supporting structure such as thick steel for mechanical strength, and an outer corrosion -resistant layer such as copper to withstand the mechanical, hydraulic and geochemical conditions in the deep underground environment. Barrier 4: Bentonite Clay, Backfill and Seals — In the repository, each container will be surrounded by bentonite clay, a natural material proven to be an effective sealing material. As placement rooms are filled with containers, they will be backfilled and sealed. The access tunnels and shafts will be backfilled and sealed only when the community, the NWMO and regulators agree that it is appropriate, and postclosure monitoring will then be implemented. • Barrier 5: The Geosphere — The repository will be approximately 500 metres underground. It will be excavated within a suitable sedimentary or crystalline rock formation. The geosphere forms a natural barrier of rock, which will protect the repository from disruptive natural events, including ice ages, and human intrusion. It will also maintain favourable conditions for the container and seals, as well as limit movement of radionuclides to protect people and the environment in the event that engineered barriers fail. Q Is there evidence from nature to indicate that this approach can work over very long times? A. The most important evidence will be from the site itself. Detailed field investigations involving geophysical surveys, characterization of the existing environment, drilling and sampling of boreholes, field and laboratory testing, and monitoring activities will be conducted during site characterization to affirm the suitability of the site. In particular, evidence will be sought that conditions at the site have been stable with little to no groundwater movement for millions of years at repository depth. There are also several locations where high levels of natural radioactivity have been contained for millions of years by the surrounding geology. These natural systems provide strong evidence supporting the concept of a deep geological repository. One location is the Cigar Lake uranium deposit in Saskatchewan. This deposit is one billion years old and is buried 450 metres below the surface, surrounded by a layer of naturally occurring clay. This clay layer has effectively contained the radioactive components from the uranium deposit. Dr. Paul Gierszewski is the Director of Safety and Licensing at the Nuclear Waste Management Organization. Prior to joining the NVVMO, he was with Ontario Power Generation, where he was responsible for maintaining and improving safety assessment system models for deep geological repositories. Dr. Gierszewski has a bachelor's degree in Engineering Science from the University of Toronto and doctorate in Nuclear Engineering from the Massachusetts Institute of Technology in Boston. He is a registered Professional Engineer in the Province of Ontario. For more information, please visit: www.nwmo.ca/backgrounders "Ask the NVVMO" is an advertising feature published regularly in this and other community newspapers to respond to readers' questions about Canada's plan for managing used nuclear fuel over the long term and its implementation. The Nuclear Waste Management Organization welcomes your questions. Please forward your questions to askthenwrno@nwmo.ca.