NEUTRON AND TRITIUM EVIDENCE IN THE ELECTROLYTIC REDUCTION OF DEUTERIUM ON PALLADIUM ELECTRODES

A Fleischmann and Pons type experiment was carried out for approximately 3 months in a ten-cell electrochemical system. All the cells were connected in series, and electrolysis was performed in galvanostatic mode at a maximum current of 2.5 A, corresponding on the average to 500 mA/cm2. In this experiment, all cathodes were made of palladium, and the anodes were made of platinum. In nine cells out of ten, the cathodes were shaped into parallelepipeds (25 x 5 x 5 mm3) by high-vacuum sintering according to a previously reported procedure. The starting material for all these electrodes was palladium sponge powder. The tenth cathode was made of 32 short 0.5-mm-diam palladium wires, gold welded together at one end. A similar concentration of screw dislocations was produced in each wire. Three different groups of sintered cathodes were used in the experiment, corresponding to three different sintering procedures. Nine cells contained 0.2 M LiOD in D2O as electrolyte. The tenth cell, containing a sintered cathode, was in 0.2 M LiOH in H2O. Measurements of neutrons, tritium in the solution and in the recombined gases, gamma rays, and electrode temperature were carried out. When the current density reached the highest values, a marked increase of the neutron detector count rate with respect to the background level (2 count/h) was observed. The emissions occurred in bursts. This behavior was observed for approximately 10 days but only when the current density was set at > 320 mA/cm2. In the first part of that period, an excess of tritium with respect to the expected value calculated for the electrolytic enrichment was found in three cells out of nine (one of the cells was in light water). This excess was about twice the amount expected with respect to the enrichment and about four times the initial tritium content in the heavy water (267 decay/min.ml). The other cells, including the one in light water, did not show any excess tritium, the value of which was in good agreement with the calculated value. Some aspects concerning the thermal behavior of the electrodes are also discussed.