Next Generation of CANDU Reactors Designed to Meet New Realities of the Electricity Marketplace, speaker saysby Michael Stephens
Speaking at last Wednesday's CNS seminar in Deep River, Jerry began by pointing to the major upheavals going in the current energy market. Prices for oil and gas are surging. The United States is stepping back from its Kyoto commitment to control its greenhouse gas emissions. Experience with market deregulation in California and Alberta has been painful. This new, unpredictable and more fluid situation presents new opportunities for nuclear power if the economics and product are right. AECL is developing the next generation of the Candu reactor design to be ready when the call comes.
Nuclear power already has several powerful arguments in its favour. It is the largest proven non-carbon energy source available. It has essentially zero air emissions, and is sustainable because it uses small amounts of a plentiful fuel. The volumes of waste it generates are small, and technologies are in hand to dispose of it. In Finland the first agreement has been signed with a community interested in hosting a fuel disposal facility.
However, to succeed in the new marketplace, nuclear power must also be price competitive. The current AECL Candu reactor design is competitive with other existing nuclear options, but its competitors are steadily moving ahead to improve their offerings. The Next Generation Program is aimed at having an innovative, economical Candu design ready for projects later this decade.
The Candu concept has long been recognized as having several unique characteristics that offer unrivalled flexibility and potential for further development: a modular core using horizontal fuel channels that can accept new fuels and fuel cycles; fuel in bundles that are simple, compact and economical; the ability to refuel the reactor while it is operating; the moderator being separate in its own cool, low pressure system; and efficient use of neutrons and the fuel, too.
The Next Generation Program is looking to profit from this flexibility in many ways. Fuel can be made with slightly enriched uranium and the CANFLEX fuel bundle design so even more energy can be extracted from each fuel bundle. Fueling adjacent fuel channels from opposite ends would mean power can be generated more evenly across the reactor core. Fuel channels with simpler, more compact end fittings could be located closer together. This would make it possible to use a smaller core. Using light water as the coolant would cut down on the amount of expensive heavy water needed. Using higher coolant and turbine pressures and temperatures would improve the efficiency of generating electricity. Safety could be improved by incorporating more passive heat sinks around the reactor. The reactor control system could be made "smarter" so the reactor could run itself more. Construction costs and schedule could be reduced by using 3-D computer-assisted design tools, and by designing the reactor so it can be prefabricated in modules to be assembled at the reactor site.
The Next Generation team has prepared a preliminary design for a single-unit 650 MW reactor (about 10% smaller than a Candu 6 reactor). The layout and configuration of the reactor building and equipment are similar to the Candu 6. Design choices have been made that are well on the way to achieving the target of a reactor that costs 40% less to build than a Candu 6. If a series of such reactors is built, the cost target should be met, and the construction of each reactor should take only 48 months (as compared to 72 months for the Qinshan reactors). Initial safety studies focussing on the design innovations have confirmed that large safety margins will be maintained. Probabilistic methods have been used to assess the value to safety of including several passive heat sink systems.
The next steps involve seeking input from potential future customer utilities to optimize the design concept to meet their requirements. Further design studies will focus on constructability, operability and plant life. Safety studies to be performed at the Chalk River and Whiteshell Laboratories will examine things like the detailed reactor physics, the materials to be used for pressure tubes and feeders, and the thermalhydraulics of the coolant and moderator systems. A business plan for an implementation project will be developed, and prelicensing preparations will start.
Jerry's presentation was followed by a lively, penetrating question and answer session.
This is the last of the seminars organized this spring by the CNS Chalk River Branch. We will be co-sponsoring and advertising the summer series of seminars presented by the Deep River Science Academy.