Fission--at the root of it

Nuclear power is not going away any time soon, but will it thrive in the future? This slideshow will show new nuclear reactor designs to improve safety and lower costs. All of them have one thing in common: nuclear fission, or splitting radioactive elements like uranium to set off a chain reaction. Splitting atoms gives off heat, which plant operators use to make steam and turn a turbine to generate electricity.

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Photo by: Martin LaMonica/CNET / Caption by:

Nuclear reactor

Before getting into new designs, take a look at today's reactor designs, which date from the 1960s. The nuclear fuel, often uranium oxide, is packaged as long, thin rods. Dozens of rods are fitted into an assembly at the center of the reactor. Water is circulated through the reactor to capture the heat and make steam. The Nuclear Regulatory Commission recently approved the Westinghouse AP1000 design, which stores cooling water above the reactor in the case of an accident. Using gravity and convection, the plant's core can continue being cooled for three days in the case of a loss of power.

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Photo by: Nuclear Energy Institute / Caption by:

Underground reactor

Here's a picture of the Advanced Light Water Reactor from Babcock & Wilcox, a third-generation reactor designed for modularity to lower costs. It has passive safety systems, meaning it can cool itself without operators in an accident and can operate for four years without refueling. As the picture shows, the reactors would be placed underground as a safety measure against attack. By going with a smaller reactor, able to generate 180 megawatts of electric power, companies like Babcock & Wilcox say they can get reactors operating within a few years, which helps lower costs and financial risk.

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Photo by: Babcock & Wilcox / Caption by:

NuScale modular reactor

NuScale Power is another startup with a modular design geared at bringing down nuclear power costs. Seen here is what a 540 megawatt electric plant, built around 12 of its smaller modular reactors, would look like. The design can withstand natural disasters, such as floods and earthquakes, according to the company. By placing the reactors in 4 million gallons of water, they have 30 days worth of cooling water in the case of a shutdown.

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Photo by: NuScale Power / Caption by:

Fourth generation

Hyperion Power Generation has another fourth-generation reactor design licensed from Los Alamos National Laboratory. Rather than using circulating water to cool reactors and spent fuel pools, the Hyperion design is cooled with liquid lead bismuth. Even with a loss of power, the natural convection would allow the reactor rods to cool without human intervention. These 25-megawatt plants would be used to replace diesel generators in remote locations, such as mining operations or islands.

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Photo by: Hyperion Power Generation / Caption by:

Traveling wave reactor

TerraPower is another fourth-generation reactor design which would use the spent fuel from existing nuclear power plants. The idea is that a single reactor would have 60 years worth of fuel and so would never require refueling. Bill Gates and Nathan Myhrvold are investors, giving this company a relatively high profile among nuclear startups. One of the most important tools that today's nuclear companies have are supercomputers that can simulate how things work.

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Photo by: TerraPower / Caption by:

Spent fuel pool

Last year's earthquake and tsunami in Japan knocked out power to cool the three reactors at the Fukushima Daiichi plant and its spent fuel pools like these at a U.S. plant. One of the first Nuclear Regulatory Commission recommendations issued in response to the Fukushima disaster was better monitoring of spent fuel pools.

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Photo by: Martin LaMonica/CNET / Caption by:

Dry cask storage

After spent fuel rods have cooled off enough, they can be taken out of cooling pools for long-term storage. Because there are not central repositories for long-term spent fuel storage, utilities now store spent fuel at power plants. One method is encasing the rods in dry casks such as these.

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Photo by: Nuclear Regulatory Commission / Caption by:
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