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315) A new effect or contamination?

Ludwik Kowalski; 11/23/2006
Department of Mathematical Sciences
Montclair State University, Upper Montclair, NJ, 07043




This unit is based what was described in unit #314. Critics will suspect that what is attributed to a new nuclear effect might be due to presence of alpha radioactive substances in the electrolyte. San Diego team is fully aware of this and the issue has been addressed by them, as reported by Steven Krivit. The strongest argument they presented was the disappearance of emission when an external electric or magnetic field is applied to the cell. This topic is worth thinking and speculating about. It will certainly become an issue after the San Diego paper is published. How easy would it be to show, by using CR-39 chips, that the initial concentration of alpha radioactivity (pCi/L) was indeed too low to produce as many tracks as actually observed? I just realized that the method I was recommending (on the CMNS list) is impractical. In fact, I recommended two methods, as shown below:

“I hope that those who read unit #314 noticed that my numerical examples about alpha activities in the electrolyte were based on the exaggerated initial concentration (10 pCi/L) in the electrolyte. I hope the electrolyte will be shown to be practically non-radioactive. But this might call for keeping a CR-39 suspended in the liquid for two or three months. A faster way to eliminate suspicions (that codeposited radioactivity is responsible for the tracks) would be to run the electrolysis, without an external field, for several hours. Then to remove the cathode and expose it to CR-39. If the initial pCi/L is very small then the number of tracks on the chip should be essentially the same as on a chip, from the same stack, that was kept in a vacuum during the same time. Oriani would probably use a pre-counted CR-39 chip; in that way the answer would be more precise (smaller random error).”

The principle behind the first method is simple. Suspend the CR-39 chip in the liquid whose pCi/L is known and count the number of tracks per cm^2. That would establish a relation between the track density, D1, and the pCi/L. Then suspend another chip in the liquid X and measure the track density D2. If D2=D1, when the exposure times are identical, then both pCi/L are also the same. If D2=0.1*D1, for the same exposure time, then the pCi/L of X is ten times smaller than the known concentration in the standard liquid. The same conclusion would be reached if, in order to obtain D2=D1 the exposure time of the second chip had to be ten times longer. For a much smaller D2, the D2=D1 would be possible only after very long exposures. The numerical illustration below, also posted on the CMNS list, shows why this simple method becomes impractical when concentrations of alpha radioactivity become less than 10 pCi/L.

Let us see if 2 or 3 months was a good guess. I will assume that the CR-39 (area=1cm^2) has already been etched and pre-counted. One side showed 6 preexisting tracks and another showed 4 (due to exposure to cosmic rays during the long storage, etc.). I select the side which has only 4 tracks and expose it to water for 100 days. I will ignore the other side. Suppose that after 100 days in water I find 40 new tracks. What was the radioactivity concentration in pCi/L?

To answer this question approximately I will make the following assumptions:

a) Alpha radioactivity was due to an isotope whose half-life is much longer than 100 days. In other words, the activity is constant.
b) The range of alpha particles in water is 0.05 mm.
c) The layer of water from which alpha particles can reach the detector is 0.05 mm thick. (The rule of thumb is "as many mg/cm^2 as MeV")
d) From all particles emitted in my layer only 10% produce tracks.

The assumption (d) can be justified as follows. 50% of particles are emitted away for CR-39. About 80 % of the remaining particles will be either absorbed in the 0.05 mm layer or reach the detector at too large angle of incidence. If these assumptions are justified then the following reasoning applies:

e) Since 40 tracks were found then 400 alpha particles were emitted.
f) What was the volume of my layer? It was 1(cm^2)*0.005 (cm)=0.005 cm^3 = 5*10^-6 liters.
g) Activity was 400 decays in 5*10^-6 L. This translates into 8*10^7 decays per liter in 100 days (or 8640000 s) or 9.2 decays per liter per second.
h) By definition, 1 Ci is 3.7*10^10 decays per second. Thus 9.2 translates into 250 pCi.

Conclusion: To produce 40 tracks in 100 days the activity would have to be 250 pCi/L. To detect 2.5 pCi/L, and to get 40 tracks, the CR-39 would have to stay in water for 100*100=10000 days, or about 27 years. . . .

It has already been shown (see above) that the concentration D2=10 pCi/L (for 222Ra, 238U, etc.) could cover the cathode surface with the amount of radioactivity emitting 32000 alpha particles in ten days. The result would be 8000 if D2 were 2.5 pCi/L. Would this be considered negligible in comparison with the number of alpha particles attributed to the San Diego effect? I cannot answer this question because I do not know how to estimate the total number of alpha particles attributed to that effect. It is desirable to have D2<0.25 pCi/L but that would call for exposures longer then 270 years.

And what about my “faster method” suggested above? Only an electrochemist can tell if the basic assumption of that method is realistic? The assumption is that atoms, such as Ra, U, in water are ionized. I think they are. That is why I expected them to migrate to the cathode surface rapidly. Several hours is reasonably short in comparison with ten days. This suggests a way to make the first method practical, even when initial concentrations of alpha-radioactivity are very low. I mention this in
a reply to a message posted on our restricted list this morning.

On Nov 23, 2006, at 5:06 AM, Michel Jullian wrote:

1) "SPAWAR effect" sounds fine, I can't understand why Ludwik dislikes it.

I will stop using the Frapa-Stanila label, at least for a while and see how others refer to the new effect.

2) Ludwik don't you agree any more that Pam's observation of "no external field --> no tracks" rules out the codeposited radioactivity artifact?

I think that the absence of tracks, when the external EM field is removed, is a very powerful argument against alpha radioactive contaminants. But I would very much like to see another, equally powerful argument.

3) It occurred to me that all imaginable artifacts associated with direct contact between the cathode wires and the CR39 material (thermal effects discussed in Steve's Galileo project FAQ, my mechanical puncturing hypothesis...) could be ruled out by interposing a thin layer of waterproof and ultra low density material such as expanded polystyrene: this would be transparent to alphas wouldn't it? (low g/cm3)

I think it is a good idea for arguing that mechanical effect are not responsible for observed tracks. But I saw too many CR-39 chips to worry about this. On the other hand, reporting that such check was actually performed, and showing real numbers, would help to establish credibility.

4) I convinced myself last night, by playing with numbers, that measuring specific alpha-activity in the electrolyte, at the level above 100 pCi/L, is feasible, provided one is willing to wait at least a month or two. Specific alpha-activities of 1 pCi/L, or less, cannot be measured in the same way. But then I realized that there is a way around. Suppose we place an open 10 L container with water to be tested, into an oven where the temperature is 97 C. How long would it take to reduce the volume of water to 0.1 cm^3? (I am trying to avoid the "escaping droplets" ambiguity we discussed in a different context.) This would increase the initial concentration, for example, from 0.1 pCi/L (that we hope for) to 1000 pCi/L. Measuring 1000 pCi/L is not at all difficult.

Again, I would like to know what chemists think about such evaporative leveraging. I already asked this question here, several days ago, but no one replied. Is it reasonable to assume that most radioactive atoms will remain in water? I believe so, especially when there is no boiling. In any case, reporting that the initial specific alpha-activity was found to be less than 0.1 pCi/L would also add credibility to the discovery of a new nuclear effect. What else can be done, to promote credibility?

5) Suppose we wait till all water is evaporated. Then nearly all (?) radioactive atoms (responsible for 10*1000=10000 pCi) will be in a very thin layer. The 10000 pCi refers to 370 alpha particles per second (or 1330000 per hour). Suppose the area of the source is 100 cm^2. Put a 1 cm^2 chip (or, more preferably, a Si detector) on top of the remaining layer. How many tracks will be formed in each hour? The source activity would be 13300 alphas per hour and the counting rate would be ~13300/10=1330 per hour. The factor of 10 is probably exaggerated, to account for particles that are not intercepted by a 1 cm^2 detector. But it is prudent to be pessimistic in rough estimations.

The situation can be improved considerably. It is silly to throw away 99% of the source area (by using only 1 cm^2). Radioactive atoms, initially distributed over the 100 cm^2 bottom, can probably be forced to move to a much smaller area, for example, 1 cm^2. I am thinking about dissolving the deposits first and then evaporating water in a tiny beaker. That would increase the counting rate to more than 1330*100=133000 per hour. Yes, I know that it is much easier to speculate than to perform experiments. But I do have some experience with such things; and I am trying to be useful.

I hope the reader of this unit would not object if I make a little digression. I want to tell a real story; it should explain why I am so much preoccupied with the issue of contamination. I was working on my doctoral project in Orsay, France. The topic was “Fission induced by protons of 156 MeV.” One day, it was probably in 1961, I received a phone call from our librarian, Mme Vergne. She said she had an American visitor who keeps telling her things she does not understand. It is something about fission. She had other things to do and she wanted me to take Bob Walker, a researcher from General Electric Laboratory, from her. That is how I met the coauthor of the famous book about solid state track detectors. He wanted to show us how tracks, due to fission fragments, could be detected in mica.

Mica was used in the same way in which CR-39 chips are used today, except that it had to be etched in hydrofluoric acid. The CR-39 chips are very useful when one wants to count rare alpha particles in presence of abundant beta and gamma rays. In the same way, mica is an ideal detector when one wants to eliminate the effect of alpha particles and protons. I quickly learned the technique and it was later put to good use. Those who might be interested in details can refer to "Fission and Complete-fusion Probabilities as a Function of Angular Momentum ...", in Physical Review C, 1974, 10, 200. Examining pieces of natural mica, found in different places, I was fascinated by tracks they always display. Tracks in mica are due to spontaneous fission of isotopes of uranium, thorium, etc. Sometimes rivers of tracks could be seen under the microscope, showing how water, containing fissionable isotopes was sipping through the tiny cracks in the crystalline mineral. It was fascinating to think that some of latent tracks were formed hundreds of million years ago, waiting to be etched and observed. I know that water always carry elements like U and Th, in trace concentrations. And I would not be surprized to learn that Pu, and other man-made elements, are also present. OK, that is the end of my personal story.
P.S.
Replying to my request for permission to quote, Michel wrote: “my suggestion was meant to rule out ‘all imaginable artifacts associated with direct contact’, not just mechanical, it could be thermal or electrical or whatever one could come up with.” Hmm, all imaginable? OK, I know what he had in mind. Yes, as many reasonable objections as possible, should be anticipated and addressed. Contamination with alpha-radioactive substances is likely to be one of them. Convincing critical thinkers that chemical processes can occasionally trigger nuclear processes will not be easy, even after the San Diego effect is recognized as universally replicable. Theoretical considerations, based on reproducible data, will become essential ammunition at the next stage.

Appended on 11/27/06
In a message posted on 11/27/06 one CMNS researcher suggested a cell whose bottom would be a very thin metallic foil -- sufficienntly thin to pass alpha particles. That would be a cathode. A detector of particles would be placed below the cathode, rather than in the electrolyte. I think that a foil transparent to alpha particles would not be strong enough to support a column of the electrolyte. That was the essence of my reply. But then I added: “About one year ago, in Oriani's lab, we were performing experiments with a glass cell that had no glass at the bottom, only a Ni foil. That was our cathode; the Pt anode was suspended above the cathode. But the Ni foil was much thicker than the range of alpha particles. The CR-39 chips were placed below the cathode, during the electrolysis. The most surprising was that the number of tracks, accumulated in two two or three days, were larger that the background. Contamination of electrolyte with alpha radioactivity, if any, could not be blamed for the effect. I do not know what was the final verdict; the results have not been published by Oriani.

I tried to replicate his results at home but no definite conclusion was reached. I did observe the effect on several occasions but results were not reproducible. I started to suspect that static charges on CR-39 surfaces (that could possibly be created by removing the protecting plastic) attracted positive alpha-radioactive ions. Such ions are always present in air. I already mentioned that, in most basements, dust removed from a TV screen is alpha radioactive. This can be checked by using a Geiger counter with a sufficiently thin window. Leave the TV on for a week or two and then remove as much dust as you can with a small piece of wet paper towel. This of course does not imply that my results were affected by static charges as large as those on TV screens. But it is better to be prudent; it easy to remove cahrges by squeezing the unwrapped CR-39 chip beween wet fingers.

I shared my suspicion with Oriani and he said that simple precautions will be undertaken to be sure that CR-39 surfaces do not remain charged. Did this eliminate the effect? I do not know. Most recently Oriani was studying cathodes after the electrolysis. CR-39 chips were applied to surfaces that were wet during the electrolysis, as described here in one of his recent messages. Oriani’s results are shown in unit #314 at my CMNS website.”

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