Last week in Part I of this three column series, I discussed the science of cold fusion. I had been considering writing about cold fusion for some time. Then last month the U.S. patent office issued a patent for a fluid heater to Italian inventor Andrea Rossi that, as we will discuss further below, purports to be running on cold fusion. So I figured the time was right.
From time to time, the topic I choose to write about has a pre-existing community of people who care about it passionately. This is certainly true for cold fusion. After publishing Part I, I received correspondence and comments from across the United States and Europe. Many of the comments were quite informative, so I hope that this trend continues. Since this series is bringing new people into the discussion, I thought it would be helpful to clarify my goals for Common Science®. Each week, I try to write a compelling column on a technical subject for non-scientists while attempting to constrain the length such that it can be read over a leisurely cup of coffee. (Note, you may need to drink rather slowly this week.) So I wanted to extend a warm welcome to the visitors from the cold fusion community and also manage expectations on the level of technical detail to follow.
Before proceeding with a discussion of the history of efforts to achieve cold fusion, I need to cover three additional aspects of the scientific background, hydrogen isotopes, the generation of hydrogen gas by electrolysis, and the decomposition of a hydrogen molecule (H2) into two hydrogen atoms. Our focus on hydrogen stems from the fact that essentially all work on cold fusion, experimental or theoretical, involves either a hydrogen fusing with itself or with some other atom.
As shown in the figure above, the nucleus of a hydrogen atom can have zero, one, or two neutrons. These variations of hydrogen are called isotopes and they are central to the story of cold fusion. Different isotopes of an atom all have the same chemical properties; meaning that they participate in chemical reactions in the same way, but their nuclei have different weights. Usually an isotope is referred to by the sum of the neutrons and protons in its nucleus. However, in the case of hydrogen, scientists have given its isotopes special names. Thus, we call these hydrogen isotopes, hydrogen, deuterium, and tritium. Often times, particularly in the discussion of fusion, deuterium and tritium are designated as D and T, respectively. Most hydrogen atoms on the earth have no neutrons in their nuclei while a few have one (deuterium). Tritium is an unstable isotope of hydrogen and is therefore extremely rare in nature but can be produced in a lab or power plant if desired. If a water molecule (H2O) contains at least one deuterium or tritium, it is referred to as “heavy” water.
In order to have hydrogen available for fusion, it’s convenient to start with hydrogen gas (H2). H2 refers to a molecule consisting of two hydrogen atoms that are sharing electrons. It can be produced in a variety of ways, but the pathway of interest for this discussion is via the electrolysis of water.
The picture above shows a simple electrolysis device. Electric current comes in through the anode, passes through the salt (electrolyte) solution and then exits out the cathode. As this proceeds, some of the water is converted into hydrogen (H2) and oxygen (O2). If some of the water molecules contained deuterium (D) then so would some of the hydrogen gas you produce. Before a molecule of hydrogen (H2) can participate in fusion, cold or hot, it needs to be decomposed into two individual hydrogen atoms. This is a simple chemical process that does not require any special technology or extreme temperatrus so I will not elaborate on this aspect of the process any further.
The importance of hydrogen isotopes in the cold fusion story arises from the structure of helium. All helium atoms have two protons, that’s what makes them helium, and over 99.99% of them have two neutrons in their nuclei. Since this isotope of helium has two protons and two neutrons, it is designated as 4He. (I apologize for all of the nomenclature this week, but there really is no avoiding it.) There are at least three ways to construct 4He from hydrogen. The most straightforward approach is to fuse together two deuterium isotopes. You can also make 5He, a helium isotope with three neutrons and two protons, by fusing tritium and deuterium. However, 5He is not stable and shortly after being formed, ejects a neutron to become 4He. Please note that those ejected neutrons will come up again later. The third pathway, which occurs in the ultrahigh temperature environment of the sun but is generally not proposed as a viable cold fusion pathway, is to construct a 4He from four hydrogen atoms with no neutrons in their nuclei during which two of the protons are converted to neutrons via a quantum mechanical process that I will not discuss here. With that background in hand, let’s move on to the history of cold fusion.
In the mid 1800’s, Scottish chemist Thomas Graham was studying the absorption of gases by metals at University College of London. He found that metals such as nickel and palladium could absorb many times their volume of hydrogen gas. At the atomic scale, the atoms in the metal do not touch one another in the traditional sense, but rather hold each other at a distance based on their electrostatic charges. Since hydrogen is very small, it can worm its way into the spaces between the metal atoms. Much of the focus of cold fusion over the years has been on the behavior of hydrogen atoms entrapped within metals. Therefore, I’ll mark Thomas Graham’s paper from 1869 demonstrating that palladium metal can absorb 650 times its volume in hydrogen as the beginning of the cold fusion story.
During the 1920’s, two scientist from Austria (Paneth and Peters) reported that by passing electricity through palladium that has been infused with hydrogen that they has caused some of the hydrogen to fuse into helium. Later, they determined that they could not be certain that the helium they measured was not from background contamination – there is some helium in the air – and retracted their paper.
In 1927, a Swedish researcher (J. Tanberg) applied for a patent for system similar to the one used by Paneth and Peters that he claimed produced both helium and heat. Tanberg’s patent application was denied since he could not explain the mechanism by which the heat and helium were produced.
Developments on the cold fusion front went quiet until 1989 when Martin Fleishman and Stanley Pons of the University of Utah announced that they had achieved cold fusion. Their apparatus was similar to the electrolysis picture above. They used palladium as the cathode so that it would both produce and absorb hydrogen and carefully measured the temperature of the system. Passing electricity through the apparatus introduces a known amount of heat. Their hope was to measure additional heat generation, presumably from fusion.
Fleishman and Pons reported periodic spikes that they observed periodic spikes of heat generation and their claims created a worldwide sensation. By 1989, the scientific knowledge of fusion had advanced quite a bit. Therefore, if Fleishman and Pons were correct, scientist expected that, along with helium and heat, neutrons, tritium, and gamma rays would also be produced in predictable ratios.
Following Fleishman and Pons’ announcement, laboratories around the world raced to try to reproduce their results. While some researcher reported possible generation of heat and others production of neutrons, most were unable to reproduce the results. Fleishman and Pons’ work was discredited and many people accused them of perpetrating a hoax. Part of the fall out from this episode is that the term “cold fusion” has fallen out favor. Work in this arena, which has continued ever since, is now referred to as low energy nuclear reactions or LENR.
Before discussing Rossi’s fluid heater, we need to return to the science of fusion for a moment. Most of the focus of fusion research has been on the hydrogen to helium route, but there are other possible combinations. Hydrogen could fuse with some other type of nucleus and convert into a heavier element. For example, if hydrogen fused with boron, which has five protons in its nucleus, it would make carbon that has six. In addition, both nuclear fission and fusion, can involve a corollary process known as neutron capture. Recall that if a deuterium and tritium fuse to form a helium atom, a neutron is emitted. This neutron can be absorbed by the nucleus of some other atom, thereby creating heavier isotope. Both processes described in this paragraph release heat.
Andrea Rossi has not disclosed many aspects and details regarding the construction and operation of his fluid heater, a practice that has helped to fuel skepticism regarding his claims. We do know that the fluid heater uses of water, nickel, lithium, and lithium aluminum hydride powder. The process is initiated by applying electric power that we can assume is creating hydrogen via electrolysis. The key element of Rossi’s claims, similar to previous researchers, is the generation of heat by the device beyond what can be explained by the power input for the electrolysis. Based spent fuel tests, which are in dispute, it is possible that some nickel in the device was converted to heavier isotopes suggesting that neutron capture had occurred. In addition, some data, also in dispute, suggests that some of the nickel had been converted to copper, which would be indicative of hydrogen fusing with nickel. Rossi states that he nickel in the device must be replaced periodically. The fact that the activity of the nickel is used up over time is consistent with neutron capture and/or hydrogen-nickel fusion being sources of heat generation in the device.
In Part I of this series, I told you I would come back this week and comment on what I considered to be a “flaw” in Rossi’s device. In retrospect, “shortcoming” would have been a better word choice. Based on the correspondence I received from the LENR community, I believe that I created an expectation that I would be delving into the physics of the device and attempting to refute some quantum physics related aspect of the process. In fact, what I was attempting to foreshadow was, that whatever the merits or flaws of Rossi’s device, it is not performing cold fusion in the commonly conceived manner of hydrogen being used to create helium. Therefore, rather than being a clean and nearly infinite source of energy based on water, Rossi’s device seems to be dependent on one-time use of nickel. While this would not detract from any potential scientific achievements, this approach brings along some extra baggage such as the need to mine nickel as fuel. Next week I’ll conclude this series with my thoughts on Rossi’s device and the implications of cold fusion for the future.
Jeff Danner talked about this column on WCHL with Aaron Keck.
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Endnote
This section is not necessary for the general thread of the series, but is available if you have time for a second cup of coffee. There is another entire branch of research in this field that includes similar levels of passion and controversy; fusion using magnetically confined plasma.
In 1952, mankind demonstrated that we could orchestrate the hydrogen to helium fusion process on a large-scale by detonating a hydrogen bomb. Since that time, there have been many efforts to run this process in a controlled fashion. We can already run the atomic bomb process in a controlled manner in a nuclear power plant. So the idea that we could also run a controlled version of a hydrogen bomb does not seem so far fetched. Generally speaking, the process involves heating hydrogen isotopes with electricity and microwaves to generate a high-temperature plasma. Since hydrogen isotopes carry an electric charge, they can confined with a high-strength magnetic field.
When a high enough temperature is achieved in the plasma, fusion occurs and among the products are high-energy neutrons. Since the neutrons lack electric charge, they are not contained by the magnetic field. This escaping flux of high-energy neutrons is the heat source of this process.
Much of the criticism of this process comes from skepticism that these high-energy neutrons can be safely contained after they are released from the plasma. If they cannot be, then they will destroy the rest of the equipment used in the process including the magnets used to create the magnetic field.
The latest effort in this arena is the International Thermonuclear Experimental Reactor (ITER) currently being constructed in the south of France. Construction of this apparatus began in 2013. As of now, expenditures have reached $14 billion, three times the estimated cost. The current projection is that the device will be on line by 2027.
There is considerable debate and tension between researchers in the LENR and ITER communities. The LENR community suggests that the ITER will never be safe or economically viable. Thus, the resources devoted to ITER are being wasted and should be diverted to LENR. Researchers in the ITER community point out that there are no doubts that fusion is occurring in their process and that all they need to do now is work out the engineering details. The other key point made by ITER researchers, which I will address in Part III of this series, is that while the currently known laws of physics are consistent with the ITER process they indicate that LENR is impossible.
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