NORM used in French Industrial Facilities: Uranium and Thorium Series Activity Concentrations and Associated Occupational Exposures

According to Council Directive 96/29 Euratom, handling or storage of NORM has to be considered from the radiological protection point of view. This directive has been implemented in French regulations by, in particular, the Ministerial Order of 25 May 2005 related to activities involving NORM that is not used for its radioactive properties. It imposes a requirement for radiological characterization of materials and for assessments of the effective dose received by workers. ASN and IRSN have already reviewed 90 studies which provide information about activity concentrations of materials and occupational exposure of nine different types of industrial facility. These data show that activity concentrations vary considerably, according to the type of material and industrial activity. Waste generally contains the highest activity concentration of radionuclides of natural origin. Activity concentrations in raw materials and products sometimes exceed the criterion recommended by the IAEA for the regulation of NORM. The activity concentrations of 226Ra and its daughters in waste or of 210Pb and its daughters in ash and dust related to high temperature processes are sometimes greater than the activity concentrations of the other radionuclides of the 238U series. Concerning occupational exposure, doses reported by operators range from <1 to 82 mSv/a. Based on the feedback from French industries, the following conclusions can be drawn: assessments are still expected for some industries; about 15% of calculated doses are greater than the effective dose limit of 1 mSv/a for the public and need further examination; the highest doses correspond to the production of thorium compounds; external and internal exposure are often of the same order of magnitude; some types of industrial facility currently not covered by the French ministerial order, such as paper mills, are affected by the NORM issue. (author)