Friday, March 15, 2013

MIT Scientists Develop Nuclear Waste Reactor

The biggest complaints about nuclear power are its safety and its waste.Two MIT Ph.D. students are developing a nuclear reactor that combats both of those concerns. Their Waste Annihilating Molten Salt Reactor (WAMSR) runs on nuclear waste from other plants. Current nuclear waste takes hundreds of thousands of years to lose its radioactivity. The pair's new reactor would expend about 98% of the waste's remaining energy, which would reduce the decay time to only a few hundred years. Leslie Dewan and Mark Massie founded Transatomic in 2011, and are working on a prototype. They hope to have the working model ready by 2015, and have the new reactors operational by 2030. 
The technology actually dates to the 1950s. Oak Ridge National Laboratory developed the molten salt reactor, but light-water reactors became the preferred choice in the United States. Dewan and Massie have retooled the reactor so that it is "fuel agnostic," and can run on uranium or thorium. The nuclear waste is dissolved into a liquid, which can stay in a reactor longer and generate more energy. And there is plenty of nuclear waste laying around, waiting to be utilized. The world produces about 9,000 metric tons of nuclear waste per year. The U.S. accounts for 2,000 of those metric tons, which it stores in depositories like Yucca Mountain. Transatomic says it can take the roughly 270,000 metric tons of nuclear waste worldwide, and turn it into enough energy to power the entire world for 72 years, even accounting for increased demand. 

The WAMSR is also safer than conventional light-water reactors. There are two "loops" to the design. The primary loop contains the molten salt and nuclear waste. The molten salt mixture's high boiling point provides a fail-safe. If the mixture becomes too hot, it expands and keeps the fuel atoms too far away from each other to continue the reaction. And unlike light-water reactors, the mixture is under low pressure so there is less wear and tear on the machinery. A second loop filled with steam adjoins the primary loop. The steam is heated and spins a turbine, just like a conventional reactor. A WAMSR plant would also be safe if it lost power, which is what happened in Fukushima. The WAMSR has an electrical "freeze valve" at the bottom of the primary loop. The valve is a block of electronically frozen salt mixture. If the power goes out, the block melts and the molten salt pools into a container below, where it will cool into a solid in a few days.

The technology's still far off, but solutions like the WAMSR could help nuclear power make a resurgence. Transatomic and similar companies, like Flibe Energy, are just starting out, but they could have a big impact on world energy. We'll keep an eye out.

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