Preparation of radioactive gaseous standard

To prepare a radioactive gaseous standard it is necessary on the one hand to put into a sealed vial a well defined quantity of the gas concerned, and on the other hand to measure its specific activity. The determination of the quantity of gas which constitutes the standard implies accurate measurements of volume, temperature and pressure. To measure the specific activity, the method of compensated internal gas counters is used. The final accuracy on the specific activity of this standards is better than 0.8 per cent. The validity of the method used for the measurements was checked by measuring the specific activity of the tritiated hydrogen extracted from a tritiated-water standard. (authors)