The Nuclear Reactor Designs
Under Review by the U.S.
The growing attractiveness of nuclear power plants as an alternative to burning fossil fuels, coupled with generous federal tax credits and loan guarantees for new reactor construction, has led to a sharp increase in applications to build new nuclear plants in the United States. The Nuclear Regulatory Commission is now reviewing the following five new reactor designs.
The Evolutionary Power Reactor
(EPR) is a 1,600-megawatt pressurized water reactor — U.S. reactors now average about 1,000 megawatts — built by France’s Areva. It has redundant active safety systems, such as backup pumps for emergency cooling in the event of an accident; a double-walled containment building; and a “core catcher” to contain and cool a melting reactor core in the event of a severe accident. Although there initially was much interest in this design, only one U.S. utility, Constellation Energy, is still actively seeking approval to build the EPR at its Calvert Cliffs site in Maryland. (An Areva EPR reactor project in Finland has encountered major construction problems, delays, and large cost overruns. Problems have also been reported at another EPR project in France.) British and Finnish safety officials have raised concerns about the EPR’s control and instrumentation systems that monitor the reactor’s temperature, pressure, and power output levels. British authorities noted the systems are “overly complex” and may not perform as designed. Areva says British and Finnish officials have since expressed confidence in the company’s ability to design safe control and instrumentation systems.
The Advanced Passive 1000
(AP1000) is at the moment the most popular design, with seven utilities indicating an interest in building 14 AP1000 pressurized water units. The manufacturer, Westinghouse Electric Company, a subsidiary of Toshiba, boasts that the AP1000’s simple engineering and passive safety systems are its selling points. The NRC has raised concerns about the ability of the AP1000 containment building, which protects the reactor core, to withstand severe weather conditions or earthquakes, forcing Westinghouse to make major changes in the structure, delaying certification and adding to its cost.
The U.S. Advanced Pressurized Water Reactor
(US-APWR) is a design built by Mitsubishi Heavy Industries of Japan. The largest of the new designs, at 1,700 megawatts, the reactor contains an active core cooling system with backup systems and a large water storage tank inside the containment building for release in the event of an accident. The Japanese government may assist U.S. utilities with financing if they select this reactor design.
The Economic and Simplified Boiling Water Reactor
(ESBWR) is a joint venture between GE Energy and Hitachi. It features a passive, gravity-driven cooling system in the containment building. During review of the ESBWR, engineers at the NRC have raised many questions about safety features, in part because components of the design have never been tested on a large scale. Among the issues: Will the passive cooling system be able to deliver water in quantities and locations needed during a severe accident? In May, Dominion Resources Inc. abandoned its plans to build an ESBWR at its North Anna, Va., site and instead chose Mitsubishi’s US-APWR. Dominion is the third large nuclear utility to drop plans to build the ESBWR.
The Advanced Boiling Water Reactor
(ABWR) is the only new design with a proven track record; several are already operating in Japan. It has an active safety system. Both Toshiba and Hitachi have built the reactors, based on a GE Energy design, and the U.S. vendor will be GE-Hitachi. At present, only NRG Energy has expressed interest in this design for its South Texas reactor, although a $4 billion jump in the estimated cost of the project caused one backer, CPS Energy, owned by the city of San Antonio, to dramatically scale back its stake. The Japanese government and a Tokyo utility may become investors in the Texas project.
— Susan Q. Stranahan
Go back to the article, “The Nuclear Power Resurgence: How Safe Are the New Reactors? ”
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