Return to the clickable list of items
126) Reactions or contamination, that is the question.
Ludwik Kowalski (1/24/2004)
Department of Mathematical Sciences
Montclair State University, Upper Montclair, NJ, 07043
In an earlier unit I provided a brief description of sophisticated tools often used by those who demonstrate cold fusion alchemy. Except for a mass spectrometer, used to demonstrate changes in isotopic compositions, my familiarity with these tools is very limited. They are mostly used by chemists and material scientists. In this unit I want to describe another method, called “nuclear activation analysis” (NAA), with which I am very familiar. I will do this before describing an interesting paper of an American researcher, T. O. Passell. The author concludes, by using the NAA method, that the isotopic composition of palladium powder, after it was used to generate a lot of excess heat, is not the same as it was before the powder was exposed to deuterium. He also argues that nuclear reactions other than D+D fusion might be significant contributors to excess heat.
Nuclear activation analysis
Suppose you want to verify a claim that a very small amount of gold, for example, 0.0001% of the total mass of a 5 grams coin consists of gold. The NAA method seems to be ideal to show that 5 micrograms of gold (plus or minus 0.1 or so, depending on specific limitations) is indeed present. As a preliminary step you exposed a pure gold sample to a flux of neutrons for certain amount of time. The sample becomes gamma-radioactive and you use a gamma ray spectrometer to see the characteristic peak. That is your preliminary calibration. Knowing the number of counts under the peak and the mass of the pure gold sample you can calculate what to expect, under identical irradiation conditions, from the same amount of gold in the coin. If the characteristic obtained from the coin is, for example, ten times weaker than from the calibration sample then you know that the coin contains only 0.5 micrograms of gold.
I am skipping many details that become important when the issues of the accuracy (absolute error) and precision (random error) is addressed. The important point is that, gold is a monoisotopic element and the amount of 197Au is essentially the same as the total amount of that substance. Many chemical elements are mixtures of several isotopes; the relative amount of each isotope in a mixture is a well known number. That number does not change by more than a fraction of a percent when samples of different origin are compared. The isotopic composition of Pd, for example, no matter where it was found on earth, is approximately as follows:
102Pd 0.96%
104Pd 10.97%
105Pd 22.23%
106Pd 27.33%
108Pd 26.71%
110Pd 11.81%
Deviations from the above average percentages do exist but they are, most often, at the level of very small fractions of one percent. It turns out that some isotopes are much easier to identify, by the NAA method, than others. Unlike traditional mass spectroscopy, the NAA method is not universal, it is suitable for some isotopes and much less suitable for others. In many cases the NAA is much more sensitive (allows to determin smaller quantities) than mass spectroscopy. The interesting thing about isotopic compositions is that they are essentially the same in all minerals containing that metal, for example, in rocks from Australia, Brazil, China or Denmark. It is also the same in palladium extracted from see water or found lunar rocks. In natural palladium the number of atoms of 108Pd over the number of atoms of 110Pd, for example, is always 0.442. But that ration is very different in palladium extracted, for example, from spent fuel of a nuclear reactor. Passell analyzed palladium after it was used in a cold fusion experiment. The atomic ratio, 108Pd/110Pd, in that palladium, turned out to be 0.477 instead of 0.442. That is a very convincing indication that some kind of nuclear reactions did occur during the experiment.
Passell’s two reports
Thomas O. Passell is research-oriented scientist (Ph.D. from the University of California at Berkeley) whose most recent report has been presented at the 10th International Cold Fusion Conference, (August, 2003). That report can be downloaded from <http://www.lenr-canr.org/iccf10/iccf10.htm> His older report (8th International Conference on Cold Fusion, Italy, 2000).is also worth reading; it can be downloaded from the library at <http://www.lenr-canr.org>.
In the older report one reads that “samples of particulate Pd weighing from 5 to 16 milligrams each were sent to the University of Texas for NAA.(7). All elements susceptible to NAA at a flux of 1012 n/cm2-sec under an irradiation of 3 hours were detected by means of their emitted gamma rays as detected in an intrinsic germanium crystal operated at 77°K.” So much for the general methodology. The neutron flux and the irradiation time are variables which could optimized for specific isotopes.
The purpose was to study chemical composition of trace elements, not to study their isotopic compositions, as in the most recent report. This is reflected in the title of the older report: “Trace elements added to palladium by exposure to gaseous deuterium.” Here is how the motivation was described by the authors of this paper. “To confirm or refute the suspicion of a possible nuclear reaction producing the excess heat, trace element changes were measured in particulate Pd exposed to very high deuterium pressures generated in the hollow core of cylindrical Pd cathodes in a series of experiments by Arata and Zhang.(l) Independently in a completely different type of experiment, Mo, Cai, Wang, Wang, and Li reported observations of increased zinc for Pd exposed to hydrogen and deuterium gas.(6) In addition they reported observing an altered ratio of Zn-64 to Zn-68 relative to that of naturally occurring zinc. They speculated that the extra zinc observed may have been produced by some nuclear process induced by the hydrogen or deuterium on the Pd metal surface, since it was unlikely that contamination by handling or experimental processes would have given zinc with an altered relative abundance of Zn-64 and Zn-68.”
The authors obtained three samples of palladium powder used by Arata and Zhang to generate excess heat [see item #23 on my CF site] plus one sample removed from the powder before it was inserted into the cold fusion apparatus. The chemical compositions of the first three samples were then compared with the composition of the fourth (virgin) sample. Increases in the amount of some elements, including iridium, gold and zinc, have been observed. Before jumping to a conclusion that the elements are produced through nuclear reactions, the authors write: “The conventional explanation for such increases is the cathodic deposition of electrolyte impurities on the cathode surface. However, all these samples were protected from the electrolyte inside the gas-pressure-tight hollow core of the cylindrical cathode. The only remaining possibility of contamination would be in the process of cathode preparation. . . . It is possible that the high temperatures experienced by the welded region could have vaporized various impurities in the Pd and the vapors carried down for deposition on the Pd powder. While this scenario is plausible for the relatively volatile zinc, it is less likely for gold and iridium. For example, zinc has a boiling point of 907°C, whereas iridium and gold have boiling points of 4800°C and 2600°C respectively.”
Due to experimental difficulties, the authors failed to confirm that the isotopic composition of zinc in the first three samples is different from that in the last sample. They were able to measure the amount of 64Zn only; the amount of 68Zn could not be determined. In the discussion of the results the authors speculate that the only exothermic “nuclear reaction capable of producing Zn-64 is the fission of palladium isotopes or proton capture in impurity copper. . . .” After providing an argument against the second possibility they write: “We are thus left with the possibility of Pd fission, a process giving about 20 to 30 Mev per fission (10-15 Mev per fission product atom). . . . The proof of a nuclear source for the increased zinc (and possibly other multi-isotope elements), will be resolved by NAA or other methods that show the isotopic abundance ratios to be significantly different from those found naturally. Otherwise, a contamination source is indicated. The small increases in iridium and gold in the active samples relative to the virgin sample find no ready explanation.”
I suppose that Dr. R. Park, an expert in surface science, read the report of Arata and Zhang before writing the “woodoo science” book (published in 2000). How does he distinguish real scientists from charlatans? But let me move to the most recent paper (2003) of Passell. I know that organizers of the 10th International Cold Fusion Conference, at which that paper was presented, personally invited Dr. Park to attend. Why did he, the official spokesman for APS (American Physical Society), decline the offer? Questions of that kind are always in my mind when I read good cold fusion papers. But that is not science. I do not know whether or not cold fusion claims are valid. But I am convinced that many cold fusion researcher are not charlatans and that their recent findings should be evaluated by appointed experts. Most of us are not equipped to conduct cold fusion experiments; that is why an authoritative evaluation would benefit all science teachers.
The title of the new paper of Passell is “110Pd/108Pd Ratios and Trace Element Changes in Particulate Palladium Exposed to Deuterium Gas.” The authors found that in palladium exposed to the deuterium gas (to produce excess heat in the cold fusion experiment of Ararta and Zhang) the 110Pd/108Pd ratio was 0.477 instead on 0.422. The 8% change in the isotopic composition of Pd is very significant. Unfortunately, a possible confirmation or refutation of changes in the isotopic composition of a trace element silver is only mentioned as work in progress. Interesting information on changes in the amounts of 109Ag, 59Co, 64Zn, 191Ir and 197Au is also provided by the author. Here are the last two sentences from his last paper. “Probably the greatest revelation in this work is the possibility that trace elements may be significant participants in nuclear reactions in solids such as Pd so that focusing entirely on D+D fusion is not necessarily the only path forward in understanding these phenomena. Of course it is possible that some of the variations in impurity levels is simply random differences within a non-homogeneous batch of powdered Pd. Iridium and gold may be in this category, since no easy explanation for their changes have been found.”
Comments
1) The NAA method is highly reliable; it has been used for decades in many applications. But it is not a universal method, like traditional mass spectroscopy. It is highly suitable for some isotopes and not suitable for others, even when only one chemical element is involved.
2) I suppose that NAA, when applicable, is much more sensitive than mass spectroscopy. That is why it should be used in the analysis of trace elements. But for the analysis of a main component in a sample, such as palladium, mass spectroscopy would be be more desirable that NAA. Why was the indirect NAA method chosen instead of the universal method of traditional mass spectroscopy? Probably because NAA is Passell’s specialty.
3) Isotopic ratios of NAA are less informative than actual amounts of substances expressed in arbitrary units. We do not know if a change in the 110Pd/108Pd is due to an increase of 108Pd or in a decrease in the 110Pd. Traditional mass spectrometry would clarify this issue.
4) By using the AAA method Passell observed a large increase in the amount of 64Zn. Such increase should not be identified with the increase of the total amount of zinc because 64Zn is only one of several stable isotopes. The identification would only be justifiable if the isotopic composition of Zn was the same in all four samples.
5) Traditional mass spectroscopy, of very high resolution, was an essential part of the methodology of Arata and Zhang. They used it to distinguish 4He from D2. I am surprised by the absence of references to studies conducted by traditional mass spectroscopy. Does it mean that nobody tried to compare isotopic compositions of Pd (before and after it was used in cold fusion experiments) by traditional mass spectrometry? It is hard for me to imagine that this was not done; an examination of a bulk element, in this case palladium, is usually easier than an examination of trace elements in it.
6) A panel of experts (appointed, for example, by the National Academy of Science, to investigate cold fusion claims) would have to decide on which experiments to focus. My recommendation would be
a) Arata and Zhang excess heat experiment with the follow up mass spectroscopic
analysis of the bulk Pd and trace elements. Also a detailed chemical analysis of
the so-called “impurities.”
b) Jones’s experiments on neutrons and charged particles. (10th International Cold
Fusion Conference, August, 2003).
c) Karabut’s experiment in which generation of excess heat was accompanied
by generation of radioactive reaction products.
d) Iwamura experiment (10th International Cold Fusion Conference, August, 2003).
Fortunately, the authors of papers in which many essential CF experiments are described are still alive. The authors should be invited to repeat the experiments in front of critical experts appointed by the Academy. How else can the unhealthy situation (that resulted from the press release in March of 1989) be resolved?