Le radon dans les stations thermales: Une source d'exposition aux rayonnements ionisants

Abstract

It is a widely recognized fact that 222Rn is the prime source of exposure to natural radiation as far as the population as a whole is concerned. The European Community has identified some groups of employees to be exposed to natural radiation in its 1996 Euratom directive. Such groups include people who work more particularly in thermal spas. Average Rn-levels, ranging from hundred to several tens of thousands becquerel per liter, are found in thermal groundwater. The gazeous character of 222Rn and its slight solubility lead it to desorb easily from water on coming in contact with the air. The Rn concentration in the air of spas depends on a combination of 2 factors: de-emanation of radon from water and ventilation. The average Rn activity concentration values cover a wide range, depending on the different occupationally-defined site. The highest values are found in water therapy rooms (∼kBq m-3) technical installations and thermal gallery (up to 102 kBq m-3). Foreign estimations of the annual occupational dose to the staff show that radon exposure can achieve several ten millisievert. The few French studies made on this subject confirm those high values of effective dose received by workers. It is necessary, therefore, to consider radon as an important source of occupational exposure in thermal spas. © 2003 EDP Sciences.