The possible separation of deuterium of tritium from hydrogen using laser radiation pressure

This report considers a method of isotope separation using infrared lasers which exploits particular features of both the molecules involved and the laser system. The method has been found to be uncompetitive for heavy water production but could possibly be suitable for the separation of tritium. It is almost certainly not useful for U235 separation. The advantage of using the infrared spectral region in any laser isotope separation process is that the selective absorption of laser light by molecules containing one of the isotopes of one of the component atoms is easiest there; the vibrational frequencies excited are determined directly by the isotopic masses. Selective absorption by hydrogen, deuterium or tritium containing molecules such as H2O, HDO and HTO is particularly easy. The infrared region is also particularly favourable for the technique of successive, coherent absorption of many photons by a given molecule, which makes feasible the separation of molecules containing different isotopes by radiation pressure, this is the direct momentum transfer from a laser beam to a beam of molecules. The laser requirements for this process have been analysed and are not impossibly difficult, though no suitable lasers exist right now. However, the throughput of an HDO plant based on molecular beams has also been calculated, and it seems likely that a single laser, with an equivalent continuous power of 15W, could produce only about 2 kgram of D2O per year. Apart from capital charges even the energy requirements of the laser and the gas pumps which are required will together cost several times the value of product D2O, so that a more detailed evaluation as a method of producing D2O is not worthwhile. These arguements do not necessarily apply for separating the much higher valued tritium fuel for fusion reactors, where the modularity of the laser process and the small amount of material involved in the plant are advantages. (author)