Search for {sup 3}He and {sup 4}He in Arata-Style Palladium Cathodes II: Evidence for Tritium Production

• Published in: Fusion science and technology 2001-09, Vol.40 (2)
• Main Authors: Clarke, W. Brian, Oliver, Brian M., McKubre, Michael C. H., Tanzella, Francis L., Tripodi, Paolo
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACTIVATION ENERGY; ANODES; ATOMS; CATHODES; DIFFUSION; ELECTROLYSIS; ELECTROLYTES; EV RANGE; GAS ANALYSIS; HEATING; HEAVY WATER; HELIUM 3; HELIUM 4; MASS SPECTROMETERS; PALLADIUM; THERMONUCLEAR REACTIONS; TRITIUM; TRITIUM OXIDES
• ISSN: 1536-1055; 1943-7641
• DOI: 10.13182/FST01-A190

Measurements have been made of {sup 3}He, {sup 4}He, and {sup 3}H in a sample containing 2.7% of the gas from the interior of an Arata-style hollow palladium electrode charged with {approx}5 g Pd-black that had undergone electrolysis in D{sub 2}O as a cathode for 90 days and then as an anode for a further 83 days. There is no evidence for the much larger amounts of {sup 4}He observed by Arata and Zhang in similar experiments. However, a very large concentration has been found of {sup 3}He, 2.3 {+-} 0.5 x 10{sup 12} atoms/cm{sup 3} standard temperature and pressure that apparently can all be attributed to the decay of tritium produced during electrolysis. No direct production of {sup 3}He can be specified, a result that is also different from the conclusions of Arata and Zhang. The {sup 3}He and tritium measurements and the results of a gas analysis using a Finnigan-type mass spectrometer show that at the end of the anodic electrolysis, the electrode void contained 5.8 {+-} 0.7 x 10{sup 13} atoms tritium in the gas phase as HT, DT, and T{sub 2}, and 1.7 {+-} 0.3 x 10{sup 15} atoms tritium in the aqueous phase as HTO, DTO, and T{sub 2}O. At this stage, the gas phase pressure was {approx}18.8 atm in a free volume of 0.6 cm{sup 3}, and the total mass of water was {approx}5.7 mg. The gas phase tritium value is viewed as a lower limit for gaseous tritium produced inside the electrode because some of that tritium must have been removed into the D{sub 2}O electrolyte during the anodic episode.The {sup 3}He and {sup 4}He measurements were also made in the two samples of the Pd-black and in sections cut from the walls of both Pd electrodes. The H{sub 2}O electrolyzed samples did not show any evidence of unusually high {sup 3}He and/or {sup 4}He, but all the D{sub 2}O electrolyzed samples showed clear evidence of {sup 3}He from tritium decay. A stepwise temperature heating experiment performed with a 24.9-mg sample of the D{sub 2}O Pd-black showed that the diffusion process for {sup 3}He can be described by an equation of the form D = D{sub 0} exp(-U/kT) with an activation energy U of 1.1 eV. It is also apparent that the {sup 3}He from tritium is quantitatively retained in the Pd-black at room temperature.