BC: DANCING UP THE ENERGY DENSITY CURVE
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MSRs were developed at Tennessee’s Oak Ridge National Laboratory in the early 1960s and ran for a total of 22,000 hours between 1965 and 1969. “These weren’t theoretical reactors or thought experiments,” says engineer John Kutsch, who heads the nonprofit Thorium Energy Alliance. “[Engineers] really built them, and they really ran.” Of the handful of Generation IV reactor designs circulating today, only the MSR has been proven outside computer models. “It was not a full system, but it showed you could successfully design and operate a molten-salt reactor,” says Oak Ridge physicist Jess Gehin, a senior program manager in the lab’s Nuclear Technology Programs office.
One pound of thorium produces as much power as 300 pounds of uranium--or 3.5 million pounds of coal.The MSR design has two primary safety advantages. Its liquid fuel remains at much lower pressures than the solid fuel in light-water plants. This greatly decreases the likelihood of an accident, such as the hydrogen explosions that occurred at Fukushima. Further, in the event of a power outage, a frozen salt plug within the reactor melts and the liquid fuel passively drains into tanks where it solidifes, stopping the fission reaction. “The molten-salt reactor is walk-away safe,” Kutsch says. “If you just abandoned it, it had no power, and the end of the world came--a comet hit Earth--it would cool down and solidify by itself.”
Although an MSR could also run on uranium or plutonium, using the less-radioactive element thorium, with a little plutonium or uranium as a catalyst, has both economic and safety advantages. Thorium is four times as abundant as uranium and is easier to mine, in part because of its lower radioactivity. The domestic supply could serve the U.S.’s electricity needs for centuries. Thorium is also exponentially more efficient than uranium. “In a traditional reactor, you’re burning up only a half a percent to maybe 3 percent of the uranium,” Kutsch says. “In a molten-salt reactor, you’re burning 99 percent of the thorium.” The result: One pound of thorium yields as much power as 300 pounds of uranium--or 3.5 million pounds of coal.
Because of this efficiency, a thorium MSR would produce far less waste than today’s plants. Uranium-based waste will remain hazardous for tens of thousands of years. With thorium, it’s more like a few hundred. As well, raw thorium is not fissile in and of itself, so it is not easily weaponized. “It can’t be used as a bomb,” Kutsch says. “You could have 1,000 pounds in your basement, and nothing would happen.”
One nuclear plant provides the energy equivalent of 1,200 windmills or 20 square miles of solar panels.Without the need for large cooling towers, MSRs can be much smaller than typical light-water plants, both physically and in power capacity. Today’s average nuclear power plant generates about 1,000 megawatts. A thorium-fueled MSR might generate as little as 50 megawatts. Smaller, more numerous plants could save on transmission loss (which can be up to 30 percent on the present grid). The U.S. Army is interested in using MSRs to power individual bases, Kutsch says, and Google, which relies on steady power to keep its servers running, held a conference on thorium reactors last year. “The company would love to have a 70- or 80-megawatt reactor sitting next door to a data center,” Kutsch says.
Even with military and corporate support, the transition to a new type of nuclear power generation is likely to be slow, at least in the U.S. Light-water reactors are already established, and no regulations exist to govern other reactor designs. Outside the U.S., the transition could come more quickly. In January the Chinese government launched a thorium reactor program. “The Chinese Academy of Sciences has approved development of an MSR with relatively near-term deployment--maybe 10 years,” says Gehin, who thinks the Chinese decision may increase work on the technology worldwide. Even after Fukushima, “there’s still interest in advanced nuclear,” he says. “I don’t see that changing.”
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You may as well ask, "Why are there no Sony Betamax VCR's on the market?" MSR technology and nuclear engineering became like "Sony Betamax" and VCR technology. Today MSR technology is nowhere to be found in nuclear engineering textbooks and labs.
Basically Alvin Weinberg (head of the MSRE project at Oak Ridge) was fired for insisting on safer, and more efficient designs for nuclear reactors. This was a politically incorrect attitude when the head of the AEC believed he already had the final answers to safety documentation and safety procedures (via U.S. Navy reactor programs). He had a plan to fill the world with fast breeder reactors, not thermal (molten salt) reactors.
Alvin was deemed irrelevant and out of touch with reality. MSR development was set on a shelf, and inertia kept it there until 25 Jan 2011 when the Chinese Academy of Science (CAS) announced their own development program. Reps from the CAS visited Oak Ridge Labs last Fall (2010) to make a reality check, and have now decided to eat our collective lunch by going after the IP and patent rights to molten salt reactors. This is a true "sputnik moment."
The most impressive response to the Chinese challenge has been the founding of Flibe Energy [...] www.flibe-energy.com [...] by Kirk Sorensen, with the blessing of his former employer, Teledyne-Brown Engineering, where he was Chief Nuclear Technologist for the last year or so. Flibe's goal is to have a functional, pilot-design Lithium-Flouride-Thorium Reactor (LFTR) on line by 1 Jun 2015, the 50th anniversary of the first MSR achieving criticality at Oak Ridge. Flibe will take the proven MSR theories and designs of 1965-1969 to commercial reality.
This agressive development program will succeed by using Computer Aided Design (CAD) programs that were non-existent in 1965; off-the-shelf pumps and plumbing; radiochemical synthesis via SCADA and Chemistry Process Control Units (CPCU) (also new since 1965); tapping private venture capital; and enlisting a staff of dedicated, enthusiastic professional engineers, IT, and business folks.
The rest of the world can go their merry way, boiling water, risking explosions, and straining to create designs using solid-fuel thorium. Flibe Energy will create a better way to "burn" all the HEU, spent fuel rods, Pu239, and 99% of the thorium fuel, then reduce the storage/disposal problems by a factor of 1,000 with LFTR's.
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Molten Salt Reactors, as the second page describes, does not use water in the plant at all, not even for cooling.
This means the reactor can be placed practically anywhere, even potentially deep underground. Though for transmission losses, being close to where the energy is used is always better, unless superconducting transmission lines can be built.
The most promising MSR design uses Thorium Tetrafluoride as fuel, which was even tested in Oak Ridge back in the 60's when they tested the MSR. This design is called LFTR, or Liquid Fluoride Thorium Reactor.
The molten salt fuel loop is self-regulating, and can not melt down and technically, it is already molten, which is the whole point.
As the temperature in the reactor increases, the liquid fuel expands, causing less fuel to be in the reactor, thus slowing down the rate of fission.
In reverse, the lower temperature it is, the tighter it contracts, causing the rate of fission to increase.
This means it can adjust to the changing demand from the power grid.
So there is no need to actively cool the reactor, since the design will not overheat.
The liquid fuel cycle means that the reactor fuel can be processed on the fly, removing fission product that impede the continuation of the fission.
It also means you can continuously refuel it, meaning that it can potentially run for decades without ever shutting down because it ran out of fuel.
And as it was described in the article, there the passive "walk away" safety system using the freeze plug.
This was routinely used in the Oak Ridge MSR experiment, where they would literally shut off the power to the reactor on Friday, letting the fuel pour in to the drain tank, built for maximizing passive cooling, where it would cool and solidify during the weekend.
On Monday they would just turn on heaters around the tank, and then pump it back in to the reactor and continue.
This is the most robust safety system there is, because it is based on the laws of physics, namely gravity.
Also because of the use of this system, any fission product in the fuel that has not been removed during normal operation at the time of shutdown, will be trapped in the fuel when it solidifies, bonded with fluoride, waiting to be removed once the plant starts again.
The future of nuclear energy is the designs that use liquid thorium fuels, as it is the fact that the fuel now is solid that it can melt down, and current reactors are not designed for molten fuel.
And the thorium fuel cycle is also much, much more proliferation resistant.
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