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Sustainable doesn't mean stagnant

June 2011

Facing issues of global warming, rising carbon emissions, and increasing dependence on foreign oil, the United States is looking to nuclear power as a key player in the sustainable energy mix of the future.

With the largest nuclear fleet in the world, the United States produces one-quarter of the world's nuclear generation—more than Russia, China, France or the United Kingdom. For the past 30 years, utilities have been adding more generating capacity to their power plants to increase power output without having to build expensive new plants. The increase in power, referred to as a power up-rate, is achieved primarily by adding more fissile Uranium-235 isotope to the fuel and optimizing the reactor core design. These changes enable the reactor to produce more thermal energy, and therefore more steam, driving a turbine generator to produce electricity.

Eliminating the fuel design bottleneck

To achieve even higher power levels, researchers now are turning their attention to advanced fuel designs. Pacific Northwest National Laboratory is developing a new metal fuel for light water reactors intended to safely increase the power output of the existing fleet of reactors anywhere from 5 to 10 percent, depending on the original reactor design. The United States currently has 104 nuclear reactors. Increasing the power-producing ability of each by 10 percent, would be like adding eight to 10 new reactors to the fleet at a fraction of the cost of building new plants. This new additional power would be enough to heat approximately 9 million homes.

Benefits of metal fuels

PNNL's new metal fuel concept uses higher density fuel. The metal fuel has better thermal conductivity than the current standard, uranium-oxide, which results in much lower fuel operating temperatures. The combination of these effects is a fuel which can, in theory, operate at higher power densities and lower temperatures than uranium-oxide.

Although fuel rod recycling is not yet practiced on a large scale, it will be necessary if nuclear power is to be sustainable. Metal fuel can make recycling less expensive. Recycling metal fuel requires much smaller facilities than those used for recycling uranium-oxide fuel thereby reducing capital costs. And metal fuel recycling can be done without producing the large amounts of liquid waste that uranium-oxide recycling does.

Drawbacks of metal fuels

Historically, metal fuels have been shown to have poor irradiation stability—in other words, the metal would swell when irradiated, causing the cladding that surrounds the fuel to rupture. Metal fuels also have lower resistance to corrosion than uranium oxide fuels.

PNNL's contribution

Because of the significant benefits metal fuels offer, PNNL is taking a new look at their use in light water reactors, which comprise all of our country's commercial power reactors. Our focus is to resolve the metal swelling issues and enhance the corrosion resistance of metal fuel. More precisely, PNNL will evaluate novel geometries, alloying additives, and corrosion prohibitors in a uranium-molybdenum alloy to improve the desired characteristics.

Irradiation testing of fuel specimens in the Advanced Test Reactor at Idaho National Laboratory is currently planned for the second half of 2012.


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