Cold fusion ‘breakthrough’ heralds clean nuclear power

NUCLEAR scientists will this week announce they may have achieved a controlled form of cold fusion, a technology that potentially offers humanity a limitless source of clean energy.

The researchers are to publish evidence suggesting they have successfully fused the nuclei of hydrogen atoms, so recreating the processes that take place within the sun.

Until now the only way to achieve fusion has been through nuclear weapons or in vast experimental machines that cost billions of pounds. Both depend on generating extremely high temperatures.

However, the latest research, by scientists at the American government’s Oak Ridge National Laboratory and the University of Michigan, was done on a laboratory bench using relatively simple and cheap equipment at room temperature.

The study echoes the work of Professor Martin Fleischmann and Stanley Pons who, in 1989, announced they had achieved cold fusion at Southampton University but were ridiculed when no one could repeat their work.

Fleischmann and Pons made what many now see as a fatal mistake when they released their results at a press conference rather than having them scrutinised by other scientists before publication in an academic journal.

It is understood that Rusi Taleyarkhan from Oak Ridge, Fred Becchetti from the University of Michigan and their collaborator, Robert Nigmatulin, of the Russian Academy of Sciences, have repeated their work and subjected it to extensive peer review.

If confirmed, the discovery could rank among the most important since the dawn of the nuclear age. The scientists are, however, extremely cautious at this stage, saying only that they have detected all the signs of fusion rather than categorically confirming it.

Their technique uses pressure waves to generate tiny bubbles in a solution of acetone that has been infused with deuterium, a “heavy” form of hydrogen extracted from sea water.

At the heart of most hydrogen atoms is a nucleus comprising a single proton. Deuterium atoms, however, have an additional particle, a neutron. This makes them roughly twice as heavy and slightly unstable.

Physicists have long known that smashing two deuterium atoms together can fuse them into tritium, a third form of hydrogen with a proton and two neutrons. This fusion releases vast amounts of energy. This was the principle used to create the hydrogen bomb in 1945, but ever since then scientists have been struggling to find a way to control the process.

In the latest technique, the sound waves create bubbles that expand with explosive force. As the wave passes, the bubbles implode, generating extremely high temperatures. This process is known as sono-luminescence after the flashes of light emitted.

Until recently scientists could generate only temperatures of tens of thousands of degrees, far short of the sun’s 10m Celsius. This appears to have been solved by “hitting” the bubbles with another sound wave that compresses them so rapidly that temperatures soar and the deuterium fuses.

An insider said the researchers had detected “promising signs of fusion” including the creation of tritium and, crucially, the emission of neutrons. The researchers believe the neutrons have energy levels consistent with those that would be emitted by deuterium fusion.

This would enable them to escape the fate of Fleischmann and Pons, whose readings of neutrons enabled them to claim they had achieved fusion. It later emerged that these neutrons could have been the results of contamination.

Neil Turok, professor of theoretical physics at Cambridge University, said the results, if confirmed, were extremely exciting: “Cold fusion has a bad history but these laboratories are among the best in the world and they will have taken every precaution to get it right.”

The research has major implications for other fusion projects. Britain already hosts the Jet project at Culham in Oxford, where a machine has been built to research sustainable nuclear fusion reactions.

This weekend it emerged that Culham had scrapped its own research into sono-luminescence and other low-tech forms of fusion after a report from Thornton Greenland, a former senior scientist, suggesting it was unlikely ever to work.

Greenland said: “I thought there was too little evidence to show it would work, but this suggests I was wrong.”

Recently, Lord Sainsbury, the science minister, committed Britain to joining an international project to build a £2 billion fusion machine called Iter, Latin for “the Way”.

Even this, however, will be able to sustain fusion reactions for only 16 minutes. A proper fusion reactor capable of producing power is thought to be 30-50 years away.

Fleischmann, who now lives near Salisbury, still believes his results were correct although he regrets allowing colleagues to press him into publicising them before he was ready.

He said: “I hope they have achieved it. If they have, I hope people are ready for it this time.”

PUTTING NUCLEAR WASTE TO WORK
A humble lawnmower engine–and a junked one at that–has pointed the way toward a novel solution for disposing of nuclear waste. If it works as well as its developer expects, it might even turn nuclear power into an energy source an environmentalist could love. Okay, maybe not love, but at least learn to live with.
The idea revolves–literally–around a new type of reactor. Called a Nuclear Powered Turbo-Reciprocating Engine (NPTRE), it runs on a mix of "fresh" and "spent" nuclear fuel.
The NPTRE is the brainchild of Claudio Filippone, an electrical engineer who, after working with leading automakers, started on a new tack by enrolling in the University of Maryland's graduate program in nuclear engineering. Before long, he decided that the familiar piston engine just might hold the key to safely disposing of the world's growing stockpiles of radioactive waste.
There are several types of radioactive waste, ranging from gloves worn by nuclear medicine technicians to underground tanks bubbling with millions of gallons of lethal leftovers from the Manhattan Project and Cold War bomb-building. But the big problem, both in terms of waste volume and radioactive content, is created by the fuel removed from commercial power plants when they are shut down for refueling once every 18 to 24 months (the refueling cycle for nuclear submarines is more frequent). Each time this is done, a portion of the nuclear fuel in the core of the reactor is removed and placed in a "spent fuel pool" near the reactor.
Fresh reactor fuel contains mostly natural uranium (U-238), enriched with between 2% and 4% neutron-emitting U-235 uranium isotope. "The splitting of the U-235 and U-238 produces fission fragments which will transform their kinetic energy into heat and continue decaying through radioactive processes," explains Filippone.
Depending upon the power-plant design, the heat created in the fissioning chain reaction produces steam or boiling water, which in turn drives a turbine connected to electric generators. The fission fragments, although radioactive, produce too few fast-moving neutrons to continue to support fission. When this happens, the fuel is considered spent–even though it still contains a large amount of U-238.
Because some of the material in spent fuel remains radioactive for thousands of years and can also be used in making nuclear weapons, the law requires that spent fuel be stored in a permanent repository. By 2020, the Department of Energy estimates, 85,000 tons of spent fuel will have accumulated. A repository to hold it still hasn't opened, so it is backing up in the local pools.
This is where the NPTRE comes in. It would allow fuel to remain in nuclear plants, where the radiation it releases can be put to work. The NPTRE's basic mechanical operation would be familiar to anyone who has changed a lawnmower spark plug. In the NPTRE, the piston is pushed by a small volume of liquid water that is quickly converted–flashed–into a large amount of superheated steam. This phase change occurs when the piston is at top dead center (TDC) and immediately after liquid water has been squirted into a specially shaped heat cavity. The steam, which now occupies more volume due to its expansion, drives the piston down.
Heat to flash the water into steam is produced by a nuclear reaction that begins when a small amount of U-235 embedded in the piston enters a section of the reactor surrounding the cylinder head.
The NPTRE actually is made of two reactors placed one on top of the other. The one that influences the piston when it is at TDC creates a chain reaction that takes place in "new"–U-235-enriched–fuel surrounded by a water-moderated reactor, the top reactor. The moderator slows the neutrons coming off the piston and the surrounding cylinder, so they can be captured, and absorbed, by uranium atoms, which then split apart to sustain the chain reaction.
As the piston travels down the cylinder, it exits the water-moderated reactor and enters a second reactor. This one is filled with spent–U-235-depleted–fuel moderated by graphite. Graphite has special neutron-scattering characteristics that make a sustained nuclear chain reaction almost possible in the spent fuel. "However, by itself, the spent fuel and graphite combination cannot sustain a usable fission reaction," explains Filippone. "They need a little something extra."
That something extra comes in the form of neutrons emitted from the radioactive piston. As it approaches bottom dead center (BDC), it adds enough neutrons to support a pulsed chain reaction in the lower reactor. It produces a small amount of additional heat, which can be circulated through a heat exchanger or directly into the top reactor, and later used to spin a turbine.
Nothing lasts forever. Eventually, the amount of U-235 in the piston decreases to the point where it produces an insufficient number of neutrons to continue the chain reaction. "However, we're talking about extending the lifetime of the fuel and its permanence in the reactor-shielded environment, perhaps as many as four to seven times longer than the current utilization," says Filippone.
And that's not all. When all of the heat and motion is accounted for, the NPTRE will achieve a thermal efficiency of 56%. By comparison, a conventional reactor operates with a thermal efficiency of 30% to 33%.
Filippone is confident about the system's high efficiency because in order to convince his Ph.D. committee that his idea would work he built a prototype. The piston and cylinder were scavenged from a junked lawnmower engine, and the high-pressure water injector is a modified 8-cylinder Oldsmobile diesel pump.
To simulate the heat released when the piston reached TDC, he used a heating element and a fast-switching electric power supply. The prototype worked and he received his doctorate. Looking at Filippone's handiwork, a member of his dissertation committee remarked that the NPTRE looked like something out of the pages of Popular Mechanics–which of course it now is.
Although the Department of Energy has expressed interest in funding more research, Filippone is realistic about NPTRE's prospects. However, he believes that even if no NPTRE is ever built, the research that went into the project will produce dividends. The heart of the system–the intricate heat cavity that flashes water into steam–can coax higher efficiency from any type of heat engine. Including those that just putter along, cutting grass.

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