Posts Tagged ‘heavy water’

Cold Fusion made the cover of
Time magazine’s May 1989 issue.

In the spring of 1989, Stanley Pons and Martin Fleishmann, in partnership with the University of Utah, claimed that they were able to create a fusion reaction in a test tube at room temperature. By the first week of May, 1989, the news had made the cover of Business Week, Time and Newsweek—the first time the same story had been on the cover of all three magazines since the Kennedy assassination. Clearly this was big news. There was a tremendous desire for this to be true: The Chernobyl disaster was still fresh in people’s minds having occurred a year previously, and the day after the press conference the Exxon Valdez oil spill occurred. People wanted to believe in the possibility of a cheap and abundant source of energy that didn’t create greenhouse gasses or radioactive waste.

But before we get into the specifics of what happened, lets review what nuclear fusion is and how it works. Fusion is when two smaller atoms fuse together to make a larger atom. The most common form is hydrogen fusion, where two hydrogen atoms combine to form a helium atom, releasing massive amounts of energy in the process. This is what occurs in our Sun and in most stars. The benefit of fusion compared to its nuclear cousin, fission, is that it does not create any radioactive waste products. The downside is that it is much more difficult to create and contain. Hydrogen fusion itself can happen in several different ways, depending on the various isotopes involved. 99.98% of hydrogen has a nucleus with only a single proton (1H). Deuterium (2H) is a stable isotope that contains one proton and one neutron in its nucleus and tritium (3H) is an unstable isotope that contains one proton and two neutrons. The process that fuels our sun combines deuterium and tritium to make helium.

Deuterium fusion: two deuterium atom fuse to create helium 4, releasing energy in the process, which then either ejects a proton to create tritium, or ejects a neutron to create helium 3, releasing more energy in either case. (Neutrons are shown in blue and protons are shown in red.)

The nuclear process that was put forth as the mechanism for cold fusion used deuterium only, produced by running an electric current through heavy water (D2O). This causes the water molecules to split, liberating deuterium. The electrode in their experiment was made of palladium, which would then absorb the deuterium gas. Palladium has the uncommon ability to absorb up to 900 times its own volume of hydrogen at room temperature. The claim was that as the palladium absorbed the heavy hydrogen, its temperature shot up, and according to Fleishmann and Pons, created a net surplus of energy. So much energy, in fact, that during one experiment the water burned a hole in the beaker, the lab table it was sitting on top of and the floor below it.

Sounds great, right? Energy so cheap it wouldn’t even be worth metering. But shortly after their press conference, problems began to develop. The first problem was that they were not able to propose a mechanism for how fusion could occur at room temperature. In order to fuse atoms, one must overcome the substantial electrostatic force when you try and bring two positively-charged nuclei close enough together so that the strong nuclear force will be able to act upon them. Normally it would require temperatures in excess of 120 million °C. To say that the deuterium gas is compressed 900 times by a palladium electrode isn’t going to even get you close. Consider, for example, the planet Jupiter which has a layer of hydrogen near its core that is believed to be in excess of 30,000 °C and pressure tens of thousands of times greater than normal atmospheric pressure on Earth, yet this is not enough to fuse hydrogen which is why the gas giant is a planet and not a star.

Another problem was that their experiment was set up to measure heat and not the by-products of nuclear fusion, specifically neutrons, gamma rays, helium and tritium. In the following weeks, several labs were announcing that they could reproduce parts of the experiment, but not all. The Department of Energy could not reproduce the results. And despite all the claims, in the end there was never any solid evidence for the production of helium, gamma rays or neutrons. A few labs found small amounts of tritium, but not enough to be more than what could be explained by contamination. These labs were in the business of measuring nuclear products and thus had plenty of sources of possible contamination—something very difficult to avoid when you are looking for such low levels in the first place.

It turns out that data had been altered before going to congress to appeal for funding. A graph had been fudged to match expected results. By May 1989, the gig was up. The American Physical Society held a session on cold fusion, at which many reports of failed experiments were heard. At the session’s end, eight of the nine leading speakers said they considered the initial Pons and Fleischmann claim dead. Steven Koonin of Caltech called the Utah report a result of “the incompetence and delusion of Pons and Fleischmann” which was met with applause. Physics Today, in a 2005 report, stated that new reports of cold fusion were still no more convincing than 15 years previous. Its a good reminder that we must always rely on the scientific method to arrive at the truth.

1) True or false: Palladium is able to absorb up to 800 times its own volume of hydrogen.

2) Which of the following is not a by-product of fusion?
a) heat  b) neutrons  c) helium  d) heavy water

3) _________ is a stable isotope of hydrogen.
a) protium  b) deuterium  c) tritium  d) helium

4) In order to fuse two positively-charged nuclei, you must overcome a substantial _______ force.
a) strong  b) electrostatic  c) gravitational  d) nuclear5) What does science rely on to arrive at the truth?


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