The new reactor is expected to save money not only because it can be built in a factory rather than on site but also because it adds safety features—which could reduce the amount of steel and concrete needed to guard against accidents—and because it runs at atmospheric pressure rather than the high pressures required in conventional reactors.
A conventional nuclear power plant is cooled by water, which boils at a temperature far below the 2,000 °C at the core of a fuel pellet. Even after the reactor is shut down, it must be continuously cooled by pumping in water. The inability to do that is what caused the problems at Fukushima: hydrogen explosions, releases of radiation, and finally meltdown.
Interview with Transatomic Power CEO Wilcox at ThoriumMSR
WAMSR is similar in many ways to the Molten Salt reactor built in th1960s but WAMSR is a factor 20 smaller due to changes in materials, geometry and spectrum. The technical approach Transatomic Power is using will work for uranium or thorium. The first product is the simpler case, which is for burning uranium, either fresh, low-enriched uranium or in the form of spent fuel. A future version could use Thorium.
If using fresh fuel, WAMSR is likely to receive UF6 gas. If using spent fuel, WAMSR would have a mechanical process to remove casings but otherwise dissolve the entire spent fuel uranium oxide directly into the salt.
The WAMSR will operate at about 700 Celsius.
Transatomic Power's Waste-Annihilating Molten Salt Reactor -- WAMSR -- can convert the high-level nuclear waste produced by conventional nuclear reactors each year into $7.1 trillion of electricity. At full deployment, our reactors can use existing stockpiles of nuclear waste to satisfy the world’s electricity needs through 2083.
Conventional nuclear reactors can utilize only about 3% of the potential fission energy in a given amount of uranium before it has to be removed from the reactor. Our design captures 98% of this remaining energy.
Using molten salt as the coolant solves some of these problems. The salt, which is mixed in with the fuel, has a boiling point significantly higher than the temperature of the fuel. The reactor has a built-in thermostat—if it starts to heat up, the salt expands, spreading out the fuel and slowing the reactions. That gives the mixture a chance to cool off. In the event of a power outage, a stopper at the bottom of the reactor melts and the fuel and salt flow into a holding tank, where the fuel spreads out enough for the reactions to stop. The salt then cools and solidifies, encapsulating the radioactive materials. “It’s walk-away safe,” says Dewan, the company’s chief science officer. “If you lose electricity, even if there are no operators on site to pull levers, it will coast to a stop.”
The new design improves on the original molten-salt reactor by changing the internal geometry and using different materials. Transatomic is keeping many of the design details to itself, but one change involves eliminating the graphite that took up 90 percent of the volume of the Oak Ridge reactor. The company has also modified conditions in the reactor to produce faster neutrons, which makes it possible to burn most of the material that is ordinarily discarded as waste. A conventional reactor produces about 20 metric tons of high-level waste a year, and that material needs to be stored for 100,000 years. The 500-megawatt Transatomic reactor will produce only four kilograms of such waste a year, along with 250 kilograms of lower-level waste that has to be stored for a few hundred years.
The company’s next step is raising $5 million to run five experiments to help validate the basic design. Russ Wilcox, Transatomic’s CEO and the former CEO of E Ink, estimates that it will take eight years to build a prototype reactor—at a cost of $200 million.
A Nuclear Regulatory Commission Spokesman says that when the detailed plans are submitted that the NRC will take at least 5 years to review the plans.
SOURCES - MIT Technology Review, Transatomic Power, Thoriummsr
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