IRSN, the Institute for Radiological Protection and Nuclear Safety, is today publishing the results of a study commissioned by COGEMA in 2004. It covers uranium mines operated in Northern Niger by COMINAK, Compagnie Minière d'Akouta (Akouta Mining Company), and SOMAIR, Société des Mines de l'Aïr (Aïr Mining Company), both COGEMA subsidiaries. For this study, IRSN was required to provide COGEMA with an assessment of the radioactivity monitoring system in the environment around the operated sites plus an assessment of the dosimetric impact on the population from the mining activities. The impact from the recovery of contaminated rebars by local populations is also addressed.
IRSN used two main sources of information for the study: data assembled during a mission carried out by its experts from 10 to 15 May 2004 at the COMINAK and SOMAIR sites and the contents of files about these sites provided by COGEMA.
Conclusions on the environment radioactivity monitoring system
The monitoring system set up by COGEMA around the two mining sites is consistent overall with standards applied in France to monitor the radiological impact of uranium residue storage facilities. Certain paths towards improvement merit exploration, however. It is important in particular to :
- investigate the exposure of certain groups settled or working in the immediate vicinity of the mining installations, which is impossible to assess directly under the existing monitoring system
- introduce specific monitoring of exposure by children, with particular emphasis on certain products that are consumed in priority by this age group (camel's and goat's milk);
- to adapt or complete the monitoring of wind-induced radioactivity dispersion by selective measurements at points chosen according to the various wind speeds and the location of potential sources of radionuclide resuspension.
Conclusions on the dosimetric impact on populations living close to the sites
Using available data, IRSN assessed the doses likely to be received by the local populations through radioactive substances being dispersed through the environment by the mining activities. Eight population groups were studied (four for each site). They were located at environmental monitoring points and chosen to represent the diverse exposure conditions. Five localities were therefore retained to assess the exposure of nomadic populations staying sporadically on the site and three to assess the exposure of sedentary populations settled in urban areas. Two age groups were studied for each group: adults and children between 2 and 7 years old. Doses expressed in milliSievert per year (mSv.year-1) are assessed by taking into account all the exposure paths to sources of radiation emitted by the mine operations. The calculated exposures are in order of or lower than 0.5 mSv.year-1 (French regulations set the exposure limit for the general public from all nuclear activities at 1 mSv.year-1 (Article R.1333-8 of the Public Health Code)) for five out of the eight groups studied. They are in the order of 0.5 to 0.8 mSv.year-1 for the other two groups. Lastly, they exceed 1 mSv.year-1 for the group living at the Akokan police station, where radon inhalation (a radioactive gas emitted by the ground) represents the bulk of the calculated dose. A mine ventilation shaft near the police station is more than likely the explanation for the presence of this gas in this location. IRSN suggests the following given the results :
- undertaking a fuller measurement campaign to assess the exposure level accurately and realistically
- ascertaining the source of the radon concentrations
- if appropriate, taking measures to limit the exposure of people concerned.
Conclusions on the recovery of contaminated rebars
The IRSN mission carried out on the site in May 2004 confirmed the presence of contaminated rebars on the mine sites and in Arlit market. An initial assessment based on assembled data and conservative hypotheses shows that the impact could be in the order of 1 mSv.year-1 for the exposure of a scrap metal dealer. Although no emergency measures are required to counteract this impact, COGEMA should nevertheless :
- make sure that the rebar control systems are effective and strictly applied before the rebars are returned to the public domain.
- instigate the recovery of contaminated rebars already in the public domain.
Download the IRSN report in French (PDF file)