Friday, November 13th, 2009
Like any renaissance the nuclear industry’s rebirth is not just about money. It’s about new ideas. Since the 1990s, four new reactor designs have been approved with a handful of others on deck.
The new plans aim to improve safety, reduce construction costs and extend the life of the plant. Based on information the companies supplied to the Nuclear Regulatory Commission, officials say they’ve taken advantage of a great deal of operating experience to improve safety.
“When you have advances in technology you are able to improve on what’s already acceptable. So as we go through our analyses of these new designs, we will do our homework to ensure that these designs at least meet our requirements and if we come to the conclusions they go beyond what our requirements are, that’s fine,” said NRC spokesperson Scott Burnell.
Doing their homework means the staff will take up to five years to review a design.
Some of the requirements they’ll examine include safety regulations imposed after the Three Mile Island accident in 1979.
To understand the new technologies, it’s necessary to grasp the basics of nuclear power generation. Put simply, when the uranium atoms in a nuclear reactor core split, heat is given off. That heat converts water surrounding the fuel tubes to steam, and the steam turns the turbines, and thereby generates electricity.
Companies building nuclear plants today have incorporated the hard lessons of Three Mile Island into the designs, Burnell said.
In the event of an overheated reactor, the Westinghouse AP 1000 and GE-Hitachi Economic Simplified Boiling-Water reactors have emergency safety features that can cool the reactor for 72 hours without any human intervention, according to the companies. The systems rely on natural forces to cool the reactor: Gravity pulls water held in reserve tanks down to the overheating reactor while steam is condensed back into water.
At present, some of the safety features require tweaking. In October, the NRC determined "the proposed design of the [AP 1000] shield building will require modifications in some specific areas to ensure its ability to perform its safety function."
The Westinghouse shield building is supposed to support an emergency cooling water tank, and also serve as a barrier to keep severe weather and aircraft out and radiation released during normal operation in.
The NRC staff is still waiting for Westinghouse's detailed submittal on design changes and testing for the AP 1000 shield building, according to Burnell.
The Westinghouse and GE Hitachi designs, along with Areva’s EPR and Mitsubishi’s Advanced Pressurized Water Reactor, are expected to have a 60-year life span. Plans show each of the designs can be constructed in about 36 to 46 months, operate on uranium dioxide fuel, and require refueling every 12 to 24 months.
The reactors' generating capacities differ: The designs are expected to produce enough electricity for between 650,000 and about 1 million average homes. Experts say these “Generation III plus” designs generate electricity more efficiently than the original plants because safety concerns dictated a more conservative approach in the early designs.
Although the new designs have yet to be approved in the United States, there are proposed locations for where they would be built. Though the NRC is currently reviewing an amendment to Westinghouse’s reactor design, seven sites in Alabama, Georgia, Florida, North and South Carolina have filed applications to build it. Two other sites, one in Michigan and another in Virginia, have opted for the GE-Hitachi design. Proposed locations for the Areva design include Missouri, New York, Maryland and Pennsylvania while the Mitsubishi design may find a home in Texas.
The Nuclear Regulatory Commission also expects to begin reviewing designs for new “advanced reactors” as soon as 2011. The Energy Department is working with General Atomics on designs for its Next Generation Nuclear Plant. General Atomic’s helium reactor has the potential to operate with 50 percent more efficiency because gas turbines are more efficient than steam turbines. But the waste generated by a gas-cooled reactor is greater, according to an Energy spokesperson.
The future of nuclear power plants may not be one-size-fits-all. The electrical output of Toshiba's Super Safe, Small and Simple reactor is less than one percent of its larger counterparts, but it won’t require refueling over its 30-year life span. Experts say the reactor could operate on reprocessed spent fuel from existing nuclear plants. The town of Galena, Alaska plans to build the design.
Toshiba isn’t the only company thinking small. Hyperion has plans for a 25-megawatt electric Power Module that is about the size of a hot tub. Like the Toshiba design, the Power Module is expected to be used in remote locations.
Other potential technologies include alternatives to uranium fuel. Thorium fuel, which unlike uranium can’t be reprocessed to make plutonium for nuclear weapons, has been used internationally and its development is a priority for the Nuclear Power Corporation of India . Thorium fuel has been used in Colorado’s Fort Saint Vrain and Pennsylvania’s Peach Bottom reactors, but no designs currently before the NRC run on combination fuel. The Energy Department says developing replacements for uranium is not a priority at this time, because the United States has access to abundant uranium supplies.