CANDU is a pressurized heavy water reactor (PHWR) that uses heavy water (deuterium oxide – D2O) as a moderator and coolant, and natural uranium as its fuel. At distances of two or three kilometres, depending on wind velocity, the cloud would begin to disperse (the dispersal zone could extend to distances of several hundred kilometres) and radioactive materials would be deposited on the ground. Subsequently, the major contributor to the radiation field is caesium-134 with a half-life of two years. This estimate is based on failure rates in the high pressure piping of the primary heat transport system being 10 times higher than has been assumed, and also on the fact that the availability of the Pickering ECCS [EMERGENCY CORE COOLING SYSTEM] has been demonstrated to be 10 times lower than postulated by the designers. No control rods are required, therefore, control is much easier than other types. A recent review of operational safety by a team from the International Atomic Energy Agency (IAEA) has confirmed that retraining is not up to the same standards as initial training, and that the AECB should establish requirements in this area. Void Coefficient of Reactivity and CANDU Reactors - Duration: 1:46. • CANDU reactors are exceptionally safe: the safety systems are independent from the rest of the generating station and each safety component has three backups. Weather conditions can also be a significant variable. The AECB believes the resources it seeks is consistent with these views. Gentilly-1 was a prototype CANDU-BWR reactor with features intended to reduce its cost and complexity. The CANDU 3 design is a single-loop pressurized heavy water reactor rated at 450 MWe with two steam generators and two heat transport pumps connected in series. The CANDU (Canada Deuterium Uranium) is a Canadian pressurized heavy-water reactor design used to generate electric power. See full listing on the Participants' page. The risks from western nuclear power plants, in terms of the consequences of an accident or terrorist attack, are minimal compared with other commonly accepted risks. Flux Tilts — The flow of neutrons can vary beyond the specified limits in various sections of the reactor core, leading to … The passive features of the CANDU reactor design have a beneficial effect in that they delay the progression of severe accidents, thereby providing an opportunity for operator actions to stabilize the plant and mitigate the consequences. This submission addresses in part, the response to that strategy. Measures which have been taken subsequently have resulted in design target levels being achieved. A Level I PSA models accident sequences up to the point at which the reactor core either reaches a stable condition or becomes severely damaged, releasing large … x��\Y�$�q���\�����x����-sJ�Gee�o�_$��' �$���Gd~Q�3\Q$@�+��8�����ϓ��s�����w/~���O��"?����?���y'�����?|w�ooi`�ߦ�y{��^�Ӷm������q���_-�w��{���{?��l��G��eY��/��_������o��f54�La�b��-u^����O�g�W��F�Z��^�Y촭~^hڇuZְ9|�~{�yzh�1��4U�~�Nj��v��5ǰm�o��&�[��/a�ެ�����O�����_i�jö�?�S�)�����@W0�
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�Iz��%���Sz��A-� v�'蓾�%�i�{&:�4��}Fg7�Y��6��. However "safe" does not mean "risk-free". New reactors designs have redundancy and passive design features to ensure the ability to contain, control and cool the reactor, even in the event of a severe natural event. %�쏢 The focus will be to ensure that … Safety is designed in from the start. . COG also has Supplier and Small Modular Reactor Vendor Participant programs. Chairman: Arthur Porter. CANDU stations use experts in health physics, radiation protection, shielding, and environ-mental safety to ensure that reactor operations comply with Canadian regulations in a safe and controlled manner. The AECB has concluded that operation of the Bruce A station during 1987 was only marginally satisfactory and that significant improvements were necessary. Chapter 14 Nuclear Reactor Materials (pdf 1.2Mb) by Dr. Derek H. Lister and Dr. William G. Cook, as of 2017.04.12 Three of the major areas of uncertainty are: Conference Shatilla, Youssef. Despite the problems discussed in this document the AECB still concludes that nuclear power plants are acceptably safe. Furthermore, the designers contend that the cooling system embedded in the reactor floor combined with an external water source, which could be hooked up manually, would be able to cope with the residual heat. It is generally agreed that the greatest threat to health in the event of a major reactor accident is the considerable quantity of the radio-isotope iodine-131 (with a specific activity of 120,000 curies/gram, and a half-life of 8.2 days) which would be released to the atmosphere. For a given release of radioactive material from the plant, the predicted radiation dose to an individual at the plant exclusion boundary could easily vary by a factor of ten or more depending on the assumptions that are made with respect to the prevailing weather conditions and therefore the dilution of radioactive materials in the atmosphere. It was then predicted that the molten core, consisting of a mixture of molten uranium oxide, stainless steel, zirconium, and other core structural materials, could melt through the bottom of the 20 cm thick steel reactor vessel and through the 3.69 metre thick concrete base slab of the containment structure. By 1993, two thirds of Ontario's electrical power will be generated by nuclear energy. 4 vgs 2004/04/02 Pg 4 Pre-Licensing Experience, CANDU 9 • CANDU 9 – a large CANDU based on Bruce/Darlington core in single unit containment • Detailed pre-licensability review in Canada in early 1990s − 2 years, >200 formal documents • Review of design requirements, design methods, safety analysis, probabilistic safety analysis, QA, decommissioning, … . The Chernobyl reactor was a RBMK type. The purpose of the ECCS [EMERGENCY CORE COOLING SYSTEM] is to remove the heat from the core as rapidly as possible. Fuel-related R&D activities that would contribute to a better characterization of safety margins in aging CANDU reactors will also be briefly discussed. It is owned and operated by New Brunswick Power. Evidence to support the Edwards/Torrie position, which is available in the Pickering Safety Reports, indicates that there were in fact (if the commissioning period is included) six loss of regulation accidents within four years. There is a fourth factor which would affect the radiation dose to people; protective actions such as evacuation of the affected populace or distribution of tablets of a stable iodine compound. The last seven CANDU reactors have been built on budget and on or ahead of schedule Advanced safety features that go above and beyond In this chapter, the concepts of biological effects, radiation … The unit at Pickering was improved upon to produce the CANDU-6 design, starting up in the early 1980s. At Bruce, because there are two independent shutdown systems (i.e. Advanced CANDU Reactor Licensing .ppt Rev. - The fuel bundles are inserted in horizontal fuel channels, each typically housing 12 fuel bundles. Despite its smaller size, the Pickering station powers up to 2.5 million households. The task is overwhelming the AECB. • CANDU reactors are equipped with protection systems which detect an emergency situation and actuate the safety system(s). Final Report, Select Committee on Ontario Hydro Affairs future AECL projects and lastly to gain insights into the design of the fully developed reactor products: CANDU 6 and CANDU 9. This compares very unfavourably with the design target of one in 100 years. The assumption is made that there would not be any evacuation of people or distribution of tablets despite the fact that the release of radioactive materials are assumed to continue for many days. 0 17 Analysis Philosophy λ In past safety analysis performed for CANDU reactors, a conservative approach is used λ That is, the assumptions and methodology applied in a particular analysis is … During refurbishment, the reactor is defueled, drained of coolant and some of the normally inaccessible systems are opened to allow parts to be inspected and replaced, if necessary. This paper presents a new concept for a CANDU-based fast irradiation reactor that is horizontal in orientation, with individual pressure tubes running the entire … CANDU reactors can accept a variety of fuels. A large volume of water contained in the calandria vault that surrounds the reactor core provides the second passive heat sink and can further slow down … The major concerns in considering a LOCA [LOSS-OF-COOLANT ACCIDENT] are the radiation doses which would be received by an individual living near the plant boundary and the total radiation dose to all the people in the vicinity of the plant. iii) the weather conditions which prevail at the time of the accident. But both Ontario Hydro and AECL have stressed that, in their opinion, even in the highly improbable event of a core meltdown, the containment system would hold. ECCS . . Gentilly-2 and Other CANDU reactors; Emergency Electrical Power; Steam Line Accidents; Pressure Tube Ruptures; Pressure Relief Valves ; The Containment System; Citations from Official Documents; References; 1. The major advantage of this reactor is that the fuel need not be enriched. Severe accidents: Accident conditions more severe than a design basis accident and involving significant core degradation. CANDU reactors were first developed in the late 1950s and 1960s by a partnership between Atomic Energy of Canada Limited (AECL), the Hydro-Electric Power Commission of Ontario, Canadian General Electric, and other companies. AECL and Ontario Power Generation Inc., in co-operation with Fauske and Associates Inc., have developed the MAAP4 CANDU code for severe core damage accident analysis in a CANDU reactor. For the most part this is made up of fission products, many of which are short lived and usually very radioactive, and the actinides (e.g. As a result, the marketability of the CANDU-3 may be prejudiced as it relies on "up front" licensing to reduce its capital costs to make it competitive. Many Canadians are not prepared to accept assurances of safety that are not demonstrable and transparent. Given the potential consequences of severe accidents everything possible should be done in order to increase the confidence in the AECB's judgment by improving the depth and breadth of its technical evaluations and inspections. In the event of a CANDU reactor coolant voiding, the positive void reactivity feedback will … Although no such major accident has ever occurred anywhere on earth, it is assumed that if a substantial quantity of radioactivity were to be released to the atmosphere, the radioactivity would collect in a "cloud" and would be carried down wind. NRX (National Research Experimental) was a heavy-water-moderated, light-water-cooled, nuclear research reactor at the Canadian Chalk River Laboratories, which came into operation in 1947 at a design power rating of 10 MW (thermal), increasing to 42 MW by 1954.At the time of its construction, it was Canada's most expensive science facility and the world's most powerful nuclear research reactor. 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