Deuterium pilots new hydrogen technology

Abstract

The heavy water used in CANDU reactors has required extensive research into isotope separation methods. Many of these involve hydrogen and so expertise has developed in a number of areas of application to hydrogen technology. From work done at CRNL in the 1970s, a wetproofed catalyst has been developed to allow the exchange of hydrogen isotopes between liquid water and hydrogen. One consequence is a process for by-product separation of heavy water that may be economically very attractive if hydrogen is produced in sufficient quantity. Alternative applications of the catalyst give hydrogen-water exchange the premier position as the basis of a process for the 1990s to extract heavy water. Megawatts of electrolytic cells have been used for many years at CRNL to upgrade heavy water. However, new applications of the catalyst have required innovations in electrolytic cell design. This work, some of it performed in collaboration with industry, includes (a) reduced cell inventory of water, and (b) greater leak-tightness of cells required to contain heavy water with a tritium content. In some applications, hydrogen had to be reconverted to water and early difficulties with recombination led to development of a variant of the wetproofed catalyst able to recombine hydrogen and oxygen in the presence of liquid water. This appears to be a broadly applicable technology since the hydrogen needs no dilution before recombination and liquid water flowing over the catalyst provides simple, direct cooling.