INTERNATIONAL STANDARDS ON FOOD AND ENVIRONMENTAL RADIOACTIVITY MEASUREMENT FOR RADIOLOGICAL PROTECTION: STATUS AND PERSPECTIVES.

Radiological protection is a matter of concern for members of the public and thus national authorities are more likely to trust the quality of radioactivity data provided by accredited laboratories using common standards. Normative approach based on international standards aims to ensure the accuracy or validity of the test result through calibrations and measurements traceable to the International System of Units. This approach guarantees that radioactivity test results on the same types of samples are comparable over time and space as well as between different testing laboratories. Today, testing laboratories involved in radioactivity measurement have a set of more than 150 international standards to help them perform their work. Most of them are published by the International Standardization Organization (ISO) and the International Electrotechnical Commission (IEC). This paper reviews the most essential ISO standards that give guidance to testing laboratories at different stages from sampling planning to the transmission of the test report to their customers, summarizes recent activities and achievements and present the perspectives on new standards under development by the ISO Working Groups dealing with radioactivity measurement in connection with radiological protection.

Study on transfers of uranium, thorium and decay products from grain, water and soil to chicken meat and egg contents.

Activity concentrations of the uranium and thorium series radionuclides were determined in chicken meat and eggs as well as in soil, water and other dietary intakes of poultry at five sites of the French territory. These data allow the calculation of transfer coefficients which enrich the database given by the technical report series no. 472 of the IAEA. In egg contents, the highest activity concentrations (in mBq kg(-1) fresh weight) are for (226)Ra, ranging between 136 and 190 and are much lower for uranium (between 0.51 and 1.30 for (238)U). In chicken meat, (238)U activity concentration is higher than in egg contents and ranges between 1.7 and 9.7. Concerning (232)Th, its activity concentration is lower than uranium and ranges between 0.5 and 4.9. Daily ingested activity concentration by the animals was assessed taking into account the activity concentrations measured in the grains, in the soil and in the drinking water. The activity concentration in grains and the daily intakes allow the calculation of concentration ratios and transfer coefficients for chicken meat and egg contents. In chicken meat the transfer coefficients (d kg(-1)) range between 0.0018 and 0.0073 for (238)U and between 0.0008 and 0.0028 for (232)Th. In egg contents they range from 0.00018 to 0.0018 for (238)U and are much higher for radium isotopes (0.10-0.23 for (226)Ra and 0.07-0.11 for (228)Ra).

Actinides and decay products in selected produce and bioindicators in the vicinity of a uranium plant.

Cypress needles collected at the edge of the Malvési uranium facility (SW France) exhibit enhanced activities of actinides and some decay products (uranium, americium, plutonium, (230)Th, (226)Ra) compared to a remote site. These enhanced activities resulted from the release of U via smokestacks and passive release from former artificial ponds located inside the nuclear site. Enhanced activities are also observed in selected produce (wheat, lettuce, fruits) sampled from the edge of the site. However, excess actinides measured in wheat grains in 2007 are inconsistent with the activities and the uranium ratio measured in the soils. This result suggests that the studied annual crops were contaminated mainly through the short-term release of airborne actinides, and that other transfer pathways, such as, uptake through the roots or adhesion of soil particles, were negligible.

International standardisation work on the measurement of radon in air and water.

Radon is considered to be the main source of human exposure to natural radiation. As stated by the World Health Organization, the exposure due to the inhalation of indoor radon is much greater than the one via the ingestion of water as radon degasses from water during handling. In response to these concerns about the universal presence of radon, environmental assessment studies are regularly commissioned to assess the radon exposure of public and workers. The credibility of such studies relies on the quality and reliability of radon analysis as well as on the sample representativeness of the radiological situation. The standard-setting approach, based on consensus, seemed to lend itself to a settlement of technical aspects of potential comparison. At present, two Working Groups of the International Standardization Organization are focussing on drafting standards on radon and its decay products measurement in air and water. These standards, which aim for a set of rigorous metrology practices, will be useful for persons in charge of the initial characterisation of a site with respect to natural radioactivity as well as to those performing the routine surveillance of specific sites.

Isotopic evidence of natural uranium and spent fuel uranium releases into the environment.

Uranium and plutonium isotopes were measured in soils, sediments and waters in an area subject to the past and present discharges from the uranium conversion plant of Malvési (France). The isotopes (236)U and (239)Pu are well known activation products of uranium and they prove to be powerful tracers of spent fuel releases in soils and sediments. On the other hand (234)U and (238)U activities measured in waters can be used to distinguish between releases and background uranium sources. Such findings contribute to improve the monitoring of the actinides releases by nuclear fuel facilities (mining sites, conversion, enrichment and fuel plants, reprocessing plants).