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You can build a car with three or four wheels. But mostly, you would want to do so with four for stability and marketplace acceptance. Basically, you need a wheel at each corner, after which you can do what you like. Flexibility comes in how you use the vehicle.
For nuclear power, the reverse of that truism applies. There are many, many ways of building a reactor and fueling it. But its purpose is singular: to make electricity. And making electricity is done in the time-honored way, using steam or gas to turn a turbine attached to a generator.
Around the world, some 460 reactors are electricity makers. Even allowing for events like the tsunami which struck Fukushima Daiichi, they are statistically the safest and most reliable electricity makers.
Yet they are large and built one at a time; one-offs, bespoke. They rely predominantly on two variations of a technology called “light water,” originally adapted from the U.S. Navy. This has left no room for other designs, fuels and materials.
Now there is a new movement to design and build smaller reactors that are not as wedded to the light water technology, although that is still in the game.
The U.S. Energy Information Administration calculates the demand for electricity will double by 2050, which means that the demand for nuclear-generated electricity with its carbon-free attributes should soar.
To understand the heft of a nuclear plant, which range from about 900 to 1,600 megawatts of electrical output (MWe), one needs a visual comparison. Most of the windmills that are now seen everywhere generate 1 MWe, or a little more when the wind is blowing. So it takes 1,000 or more windmills to do the job of just one nuclear power plant. That stark fact is why China, in environmental crisis, has the world’s largest nuclear construction program.
But the days of the behemoth light water reactor plants may be numbered.
The challenge comes from what are known as small modular reactors (SMRs), rated at under 300 MWe. Stimulated by a total of $452 million in matching funds from the U.S. Department of Energy, the race is on for these smaller reactors. Call them the new, improved, front-wheel drive reactors.
The future for these is so alluring that eight U.S.-based manufacturers are competing for seed funding from the DOE for reactors that range in size from 10 MWe up to 265 MWe. Other countries are also revved up including Argentina, China, India, Japan, Korea, Russia and South Africa.
Whatever the design, one of the big advantages the new entrants will have is that they will be wholly or partly built in factories, saving money and assuring quality. Some designs, like those of Babcock & Wilcox (which won the first round of funding) and Westinghouse, are sophisticated adaptations of light water technology.
Others, like General Atomics’ offering, called the Energy Multiplier Module, or EM2, are at the cutting-edge of nuclear energy. It relies on a high operating temperature of 850 degrees Centigrade to increase efficiency, reduce waste, and even to use nuclear waste as fuel. It is designed to work for 30 years without refueling, relying on a silicon carbide fiber ceramic that will hold the fuel pellets.
“The ceramic does not melt and if it is damaged, the material tends to heal itself,” says John Parmentola, senior vice president at General Atomics, which developed the Predator unmanned aerial vehicle and the electromagnetic launch system for aircraft carriers, which replaces the steam catapult.
Others designs include thorium fuel instead of uranium, the use of molten salt as a moderator and coolant. Three of them, including General Atomics' design, are so-called fast reactors, where a moderator is not used to slow down the neutrons as they collide with the target atoms. Think fission on steroids.
It is as though nuclear designers have thrown off the chains of legacy and are free to dream up wondrous new machines, similar to the start of the nuclear age. — For the Hearst-New York Times Syndicate
This is good, but misses key points…
a) SMRs will not be adequate solutions. If power needs indeed double, and we now only meet <20% of needs via nuclear, then the 400+ large nuclear plants worldwide will need to become 4000. Trying to deploy SMRs to meet that is impossible. The Russians are deploying 300MWe barges for Siberian coastal develoipment alone and are offering developing countries nuclear plants that will be built & run by Russia, si9mply selling electricty to the country. some of these may be SMRs, but the "S" is the most important letter to grasp.
b) Fast reactors need far more fuel than moderated (thermal) ones because the probability of an atom being hit by a fast neutron as ~1/25 that for a thermal one. This is fine for consuming spent fuel, which is ~94% U238, but it also means the reactor's security must be higher, since it's breeding Plutonium from U238 and fissioning that new Pu.
c) The molten-salt reactor provides excellent, passive safety as well as the ability to use fast or thermal neutron reactions, the latter allowing Thorium as the cheap abundant 'fuel' and avoiding Pu production.
d) Neither the SMR or the MSR are 'new'. Nor are fuel 'pebbles'.The need in 1980 was 1GWe coming on line each week. http://tinyurl.com/6xgpkfa This would have avoided our climate threats, but Nixon, Carter… fumbled on funding what JFK started. http://tinyurl.com/73p7ler and http://www.thoriumremix.com SMRs won't do more than nibble at our troubles.
e) The fundamental problem is >500 billion tons of fossil carbon already converted to $ in combustion-industry accounts. That carbon, emitted as CO2, is now in air & seas, both changing climate and ocean chemistry. The latter is only years away from a true tipping point, which cannot be recovered from if crossed — that's what "extinction" means. So we actually need even more than double present power in order to fabricate the materials needed for world ocean chemistry protection. We are in deed naive and have been fools…
http://www.the-weinberg-foundation.org/2013/09/09/the-many-ways-that-molten-salt-reactors-can-fight-the-other-co2-scourge-ocean-acidification/
Our problems include our faddishness, like the SMR uber alles naivete. We need to go back to the 1960s wisdom & hard work that got us the MSR, the IFR and Moon landings.