Wednesday, July 27, 2011

Bill Gates' TerraPower On Track for 2016 Build, 2020 Startup

The radical new nuclear reactor design being financed by Bill Gates, is in the middle of intensive design changes to make the reactor easier to build. Most of the design and engineering is taking place in the US. The company will need to find a building site overseas, due to the US Nuclear Regulatory Commission's obstinate inability to approve new reactor builds and licenses within the United States. More from Technology Review (h/t Brian Wang)
In the new design, the reactions all take place near the reactor's center instead of starting at one end and moving to the other. To start, uranium 235 fuel rods are arranged in the center of the reactor. Surrounding these rods are ones made up of uranium 238. As the nuclear reactions proceed, the uranium 238 rods closest to the core are the first to be converted into plutonium, which is then used up in fission reactions that produce yet more plutonium in nearby fuel rods. As the innermost fuel rods are used up, they're taken out of the center using a remote-controlled mechanical device and moved to the periphery of the reactor. The remaining uranium 238 rods—including those that were close enough to the center that some of the uranium has been converted to plutonium—are then shuffled toward the center to take the place of the spent fuel.

...In this system, the heat is always generated in about the same area within the reactor core—near the center. As a result, it's easier to engineer the systems to extract and use the heat to generate electricity.

One challenge with this design is ensuring that the steel cladding that contains the fuel in the fuel rods can survive exposure to decades of radiation. Current materials aren't good enough: for one thing, they start to swell, which would close off the spaces between the fuel rods through which coolant is supposed to flow. To last 40 years, the materials would need to be made two to three times more durable, Terrapower says.

The company is using computer models to anticipate how currently available materials would change over time, and is developing reactor designs that anticipate these changes. For example, if it's known that a material would swell in the conditions inside the reactor, the spaces between the fuel rods would be designed to accommodate this swelling, says Doug Adkisson, director of operations at Terrapower.

Terrapower has also developed designs for a passive cooling system. Like many other advanced reactor designs, Terrapower's uses molten sodium metal as the coolant. Sodium takes much longer to boil than water, which gives plant operators more time to respond to accidents. It would also be possible to use natural convection and air cooling in the event of a power outage—coolant wouldn't have to be continuously pumped into the reactor, as was the case at Fukushima. One danger of using sodium, however, is that it reacts violently when it's exposed to air or water.

Terrapower's next steps include finalizing the design and finding partners to build the plants. It's been in talks with organizations in China, Russia, and India. Gilleland says the company expects to have an announcement about partners within the next few months. _TechnologyReview
After all the work and investment done in the US, the company will be forced to go to China, Russia, or India to build an actual demonstration plant. Just one of many signs that the US government is bloated and sclerosed almost beyond repair, unless drastic changes are made.



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