Search for super(3)He and super(4)He in Arata-style palladium cathodes II: Evidence for tritium production

• Published in: Fusion science and technology 2001-09, Vol.40 (2), p.152-167
• Main Authors: Clarke, WBrian, Oliver, Brian M, McKubre, Michael CH, Tanzella, Francis L, Tripodi, Paolo
• Format: Article
• Language: English
• Subjects: Activation energy; Cathodes; Electrodes; Electrolysis; Isotopes; Mass spectrometers; Palladium; Pressure effects; Tritium
• ISSN: 1536-1055

Measurements have been made of super(3)He, super(4)He, and super(3)H in a sample containing 2.7% of the gas from the interior of an Arata-style hollow palladium electrode charged with [similar to]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 super(4)He observed by Arata and Zhang in similar experiments. However, a very large concentration has been found of super(3)He, 2.3 plus or minus 0.5 x 10 super(12) atoms/cm super(3) standard temperature and pressure that apparently can all be attributed to the decay of tritium produced during electrolysis. No direct production of super(3)He can be specified, a result that is also different from the conclusions of Arata and Zhang. The super(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 plus or minus 0.7 x 10 super(13) atoms tritium in the gas phase as HT, DT, and T sub(2), and 1.7 plus or minus 0.3 x 10 super(15) atoms tritium in the aqueous phase as HTO, DTO, and T sub(2)O. At this stage, the gas phase pressure was [similar to]18.8 atm in a free volume of 0.6 cm super(3), and the total mass of water was [similar to]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 super(3 )He and super(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 super(3)He and/or super(4)He, but all the D sub(2)O electrolyzed samples showed clear evidence of super(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 super(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 super(3)He from tritium is quantitatively retained in the Pd-black at room temperature.