An apparatus for the purification of radon

by H. C. Sutton

Institution: University of Canterbury
Department: Chemistry
Year: 1947
Record ID: 1301840
Full text PDF: http://hdl.handle.net/10092/9069


As is well known, radium has been used for many years as a source of gamma radiation for therapeutic use. The method consists in placing needles of radium in suitable positions on and around the cancerous growth; dosage being controlled by the radium content of each needle, and its time of application. Such operations are extremely dangerous, in that the needles are small and easily lost; yet the radium decays very slowly so that the intensity of radiation emitted by the needles remains almost constant. The high cost of such needles also limits their use. An alternative method of gamma ray therapy utilises needles of radon, the radioactive gas which is the first decay product of radium. Radon has a half life period of 3.825 days, compared with that of radium, of 1580 years. Consequently its activity is appreciable only over its first few days, having fallen to one per cent of its initial value in 25 days. The danger factor is thereby largely eliminated, since lost radon needles would be quite safe, even if still inside that patient, after a month or so. Moreover, the dosage can be arranged so that the needles are left permanently in the patient, the dose integrating to the required amount in infinite time. In some cases, where the tumour is rather inaccessible, this method is very convenient. A further advantage of radon lies in the fact that it is a gas, and can therefore be compressed to small sources of any required shape or size. Thus the radium from which it is prepared is rendered many times more useful, all types of needle being available from a common source. This extends its use to many cases not otherwise capable of treatment, as it will be appreciated that the cost of a complete stock of all types of radium needles is prohibitive. The more so, so many of them would remain out of use for years.