"There was an immediate rush to reproduce the Pons and Fleischmann experiments. A few experimenters reported success, many others failure. Even those who reported success had difficulty reproducing their results. Furthermore, no one was seeing the expected fusion products. The three known D + D reactions are:
D + D --> H + T (two deuterium nuclei yield a hydrogen nucleus and tritium, a heavy hydrogen isotope containing two neutrons) or
D + D ---> n + 3He (yielding a neutron and helium 3, a light isotope of helium), or
D + D ---> 4He + gamma (yielding normal helium 4 and a gamma ray).
"The first two reactions are equally probable, and if one watt of nuclear power were produced, the neutron and tritium production would be easy to measure. But they could not be detected; if they were present at all, it was only at an extremely low level. The third D + D reaction normally proceeds much more slowly than the first two. Some experiments eventually did report helium 4 production, although great care must be used to avoid contamination by trace amounts of helium normally present in the air. This led many cold fusion researchers to postulate that somehow the third fusion reaction was catalyzed in the palladium. Moreover, it was necessary to postulate the suppression of the gamma radiation, which was never observed. There is no widely accepted theory that might explain such effects, however. Therefore, most of the scientific community concluded that the 'Pons and Fleischmann effect' was experimental error.
"Even so, several laboratories continued cold fusion experiments. Excess power remained small and sporadic. If some of the recent reports of new work can be verified, however, the years of effort might be paying off. Pons and Fleischmann now report excess powers of 100 watt (150 percent of the input power) sustained over a 30-day run. The Pons and Fleischmann technique calls for about 20 days of electrolytic conditioning, after which the cell is allowed to heat to boiling for the power run. This technique was reportedly reproduced by a separate group under G. Lonchampt, with support by the French Atomic Energy Commission and in consultation with Pons. Other groups in Japan and Italy are beginning to report excess powers in the 30 to 100 percent range. Experimental results of this magnitude are far beyond ordinary chemistry and point toward the possible existence of some new effect. It might not be 'cold fusion' at all. Whether the effect is a new kind of chemical reaction, a new pathway for nuclear reactions, or something either more surprising or more mundane will only be known after more research.
"Different techniques have been tried to produce cold fusion, including electrical discharges, ultrasound and hydrogen in ceramic electrolytes. Here I will highlight only electrolysis using nickel cathodes in alkali salt solutions in ordinary, light water. These cells are much cheaper than ones using heavy water and palladium. The most impressive excess power to date from this class is reported by James Patterson and his company, Clean Energy Technologies (CETI), in the U.S.
"There are tantalizing new hints about possible products from nuclear reactions. Tadahiko Mizuno's group at the University of Hokkaido in Japan analyzed the components of a Pd-heavy water cell before and after an extended run at high temperature. They reported low concentrations of a range of heavy elements, including calcium, titanium, chromium, manganese, iron, cobalt, copper and zinc. George Miley of the University of Illinois, working with Patterson cells and either nickel or layered nickel-palladium cathodes, also reported a wide range of medium and heavy elements. Similar, but less detailed, results have been related by a few other groups. Production of such heavy nuclei is so unexpected from our present understanding of low-energy nuclear reactions, that extraordinary experimental proof will be needed to convince the scientific community. All available analytical techniques will have to be applied and the results reproduced. CETI recently started lending Patterson cells to independent laboratories to speed up research.