small modular reactor

The Rare Promise of Thorium Reactors

August 24, 2015 by Llewellyn King 4 Comments

By Llewellyn King

If you want to design a new automobile, there are choices, but there are also parameters. For example, you would be advised to start with four wheels on the ground. You could design it with three, but the trade-offs are considerable.

When it comes to designing a new nuclear reactor for generating electricity, there are no such absolutes. A nuclear reactor only needs a safe nuclear reaction and the ability to harness the resulting heat. That means that nuclear reactors can be configured in all kinds of ways with considerable variety in the design of the fuel, the size of the reactor, the cooling system and the moderator (usually water).

Not only can the configuration of the fuel vary with differing results, but the fuel also can vary. It can be, for example, the intriguing metal thorium, which is plentiful in nature. It is fertile but not fissile, which means it takes uranium or plutonium to get a nuclear reaction going. When that happens, a thorium reactor appears to have advantages, from the availability of the fuel to the safety of the reactor.

Yet most of the world’s commercial civilian reactors – more than 400 — have just one basic design: uranium-fueled light water. The moderator is water.

Adm. Hyman G. Rickover, the father of the nuclear Navy, favored this technology. Recognizing that left to their own devices, nuclear engineers would come up with dozens of reactors, and would stymie the effort get industry off the ground, Rickover pushed light water. The admiral was a man who got what he wanted. So the light water reactor (LWR) became the world standard with some national exceptions.

Canada developed a very successful reactor that uses natural uranium, but requires heavy water: water with an extra hydrogen atom. Britain built two different reactor designs, the Magnox and the Advanced Gas Reactor, but finally has come around to the light water reactor. The Soviet Union went ahead with its own designs, including the disastrous Chernobyl design.

Although LWR construction steams ahead in China, and more hesitatingly elsewhere, there is a sense that it is time for change. Time to look at other designs and fuels.

In the United States, the Department of Energy has stimulated interest in a new generation of small modular reactorsand some ideas, which got pushed aside by light water technology, are doggedly holding on and even fighting back. Among these are various gas reactor concepts and fast reactors, where the neutron flux is not slowed down and which can do amazing things, including burning a certain proportion of nuclear waste.

The molten salt thorium reactor continues to have its advocates, although this technology is not included in DOE’s small modular reactor program. It is not a new idea, but it is one that has been given short shrift from the nuclear establishment in recent years. Promising work on it was done at the Oak Ridge National Laboratory in Tennessee in the 1960s, under the legendary scientist and laboratory director Alvin Weinberg. He died in 2006, and I was lucky to have known him.

Proposed thorium molten salt research reactor. Source: Thorium Energy Alliance

When I attended the Thorium Energy Alliance annual conference, held in Palo Alto, Calif., this year, I felt I had stumbled into an old-fashioned revival meeting. They are believers. Work on thorium-fueled reactors is ongoing in China, India and Russia.

But the best hope for thorium future may not lie in the nuclear sphere at all. It may rest with rare earths, and the global appetite for these in a high-tech world. A simple way to understand rare earths is that in technology they are great multipliers, making products in consumer electronics, computers and networks, communications, electricity generation, health care, advanced transportation, and across a wide range of defense materiel, more effective. With a small application, say to the turbine in a wind generator, the efficiency may increase several times.

Rare earths — which are not really rare at all — are found in conjunction with thorium, often in phosphate mining. When the world gets serious about the rare earths supply, it has to get serious about thorium, especially in the United States.The Thorium Energy Alliance would like to see thorium put into a national stockpile, so that it is available when the pendulum in reactor design swings to thorium, and that becomes the future.

Can the 17 rare earth elements become the thorium reactor’s enabler? Some devoutly believe so. — For the InsideSources news service.

The Coming Carbon Composite Revolution

September 6, 2013 by White House Chronicle 1 Comment

The other day I was musing over how materials throughout history have improved our lives. Take the ordinary candle, which is made of beeswax. It helped us overcome our fear of the dark. The candle provided a totally new capability: People had a portable light source to allow them to see and read anywhere they wanted.

Today we have hand-held devices that not only enable us to read anywhere we want, but also access reading material anywhere it is available in the world. We owe this revolution to ordinary beach sand, which is a source of silicon that makes digital circuits work.

And the remarkable materials of history do not end here. For example, corn provides the basis for biodegradable plastics, and we have even invented flexible concrete that widens its application.

Materials are fundamental to revolutions that improve our lives.

A new emerging class of materials, carbon composites, is revolutionizing the performance of mobile platforms. Carbon fibers, which are thin and flexible like ordinary sewing thread, can dramatically reduce weight, and therefore vehicle fuel consumption, but at the same time provide greater safety because of their toughness.

Defense systems, like the Predator Unmanned Air Vehicle, pioneered the path to exploiting these materials. The X43 scram jet, at nearly 10 times the speed of sound, set the world airspeed record through the use of carbon composites. We are now seeing the emergence of these materials in the Boeing Dreamliner and automobiles like the Chevy Corvette.

Quite remarkably, you can form a new ceramic material from combining beach sand and carbon, like that contained in soot.

As the ancients understood, ceramics can withstand very high temperatures because they do not melt like metals. There are many advantages to high-temperature, high-strength materials:

1. They are the basis of ceramic brakes that resist wear, even at very high temperatures where metals fatigue.

2. They enable the Space Shuttle to withstand intense heat loading upon reentry in the atmosphere.

3. They can also improve engine efficiency; with a properly chosen medium, you can store large amounts of high-temperature heat. You can then use that high-energy medium to drive mechanical devices, like turbines, to produce high-speed motion and with it electricity at high efficiency.

One such ceramic material, silicon carbide, can withstand temperatures of over 2,000 degrees centigrade without loss of strength — metals exhibit fatigue at 700 degrees centigrade. Its properties suggest some important safety applications, such as replacing the metal tubing that surrounds nuclear fuel in light water reactors.

Silicon carbide can also withstand the intense neutron environment in a nuclear reactor over long periods of time, because it has the remarkable property of self-healing. It repairs itself like living cells.

These properties have inspired engineers at General Atomics to develop a new nuclear reactor concept with potentially far-reaching performance advantages. This reactor, Energy Multiplier Module (EM squared), is the smallest-size, highest-efficiency and highest-power small modular reactor in the world. Because the fuel surrounded by silicon carbide tubing can withstand high temperatures (more than 2 ½ times that of current reactors) and transfer its heat to a high-capacity medium, like helium, the reactor system can achieve 53 percent efficiency, nearly twice that of other small modular reactors.

Since the fuel contained by the silicon carbide tubing can stay in the reactor for longer periods of time (nearly seven separate fuel loadings of current reactors), there is much less waste; in fact, 80 percent less waste. And because the fuel and silicon carbide can withstand much higher temperatures, the safety margins are potentially much better.

Like any new technology that can dramatically improve performance, there are economic benefits. We can reduce the price of electricity by 40 percent relative to current reactors. This puts the price of nuclear-generated electricity within the energy mix in the United States. It also makes such reactors much more competitive in international markets.

This innovation comes at a time when nuclear energy has reached a crossroads. So we have a choice: Embrace new technology, as we have in the past, to improve performance, or continue to look in the rear-view mirror with ideas that just hold back human progress.

John Parmentola is senior vice president of General Atomics, a San Diego-based nuclear physics and defense technology company.

The Scramble for a New Nuclear Reactor

August 24, 2013 by White House Chronicle 1 Comment

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

The Scramble for a New Nuclear Reactor

August 24, 2013 by White House Chronicle 1 Comment

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.

But the days of the behemoth light water reactor plants may be numbered.