The effect of radiological protection standards on the uranium market

On the basis of concrete results obtained in the CEA's uranium mines over a period of 15 years, the authors determine to what extent the costs of radiological protection affect the price of uranium. The principles on which radiological protection is organized in the CEA mines are mentioned. Emphasis is placed on the precautions which have to be taken in order to ensure that radioactivity measurements are representative despite the extreme complexity and the variability of conditions in the workings. A description is given of the way in which the operation of the ventilation system is varied on the basis of radioactivity measurements as the workings are extended. The authors conclude that in the CEA mines, where the uranium content in the ores frequently exceeds one per cent, it is possible to ensure that the current standard is actually adhered to and that nevertheless the cost of radiological protection remains marginal. In the second part of the paper the possible effects of increasing the stringency of the standards are examined. The considerations are based on several thousands of measurements carried out in various workings and galleries. It is shown that the correlation between radon concentration and ore content is weak. It is pointed out that the state of equilibrium of radon daughters in the workings is of the order of 0.2 rather than the 0.5 assumed in the standard. On this basis the mean level of actual exposure, in total alpha energy, is of the order of 20% of the value 1.3 x 105 MeV α/litre, the level of the most highly exposed worker being 80% of that value. In addition, it is shown that with simple improvements to the design of the ventilation circuits and elementary precautions it is often possible to ''rejuvenate'' the radon in the workings and influence still further the state of equilibrium of the daughters. Finally, preliminary results obtained in the experimental mine at La Crouzille indicate that the radon concentration can be further influenced by subjecting the mine to an overpressure. In these circumstances it would appear that the careful application of existing methods should make it possible to tolerate a moderate increase in the rigour of the standards. The sensitivity of the cost of radiological protection to various factors is investigated. It is concluded that the introduction of slightly stricter standards - by a factor of three, for example - would in the short term have only a slight effect on the price of uranium from existing mines, and this effect would undoubtedly be absorbed in future mines, provided that operations were geared to these new standards from the outset. In the long term the uranium market would not be affected and the effect on world reserves would be negligible. On the other hand, stricter standards going beyond a certain threshold might make mining impossible and reduce world reserves to the amounts obtainable by quarrying