How it is monitored
Monitoring of the environmental radiological status is carried out more particularly in the vicinity of nuclear installations, but it is also carried out throughout France.
Consequently, different monitoring networks have been deployed to collect regular and precise measurements:
- Sampling networks in the environment (air, water, soil and foodstuffs to be analyzed a posteriori by the laboratory)
- Continuous radioactivity monitoring networks which provide real-time transmission and processing of the measurement results, and also have an alert function in case of an unusual peak in measured radioactivity.
Nuclear facilities under close monitoring
A monitoring ensured by the operators, regulated by the ASN...
In the vicinity of nuclear facilities, French regulations require operators to monitor the effluent discharged by their installations and the environment around their installations, both inside and outside nuclear sites.
Radioactivity measurements of the samples taken for this monitoring, must be carried out by approved laboratories. This monitoring is generally carried out as close as possible to the potential sources of accidental release.
Under close monitoring are : nuclear installations, related to or involved in the industrial stages of electricity production (old uranium mining sites, manufacturing factories, sites for enrichment or reprocessing of nuclear fuels, nuclear power plants, treatment centers, nuclear waste storage facilities), nuclear research centers, and military ports with nuclear naval bases.
This global monitoring organization placed under the nuclear operators’ responsibility, constitutes the main source of measurement data, making it possible to know the radiological status of the environment around the nuclear facilities.
... and supplemented by IRSN
IRSN conduct a regular monitoring around nuclear sites, complementary to that set up by nuclear operators, via its own monitoring networks. The measurement data collected are also fed into the RNM network.
A monitoring covering the whole country
Beyond the close watch of the facilities, a widened monitoring makes it possible to know the radiological status of the environment.
Cette surveillance est réalisée par de nombreux acteurs : l’IRSN, les directions ministérielles et les services de l’État en charge de contrôles sanitaires, des associations…
IRSN collect data on the French environmental radioactivity in metropolitan France and DROM-COM via radio-ecological studies carried out on request from nuclear operators, from public authorities or from representatives of civil society (CLI, communities, associations, etc.), or via its own study and research programs.
The ministerial and governmental bodies in charge of health inspections have a general mission of sanitary control of foodstuff and animal meats, which requires the search for hazardous chemical, physical and biological agents, including search for radioactive substances.
For example, the Directorate-General on Food Safety (DGAL) carry out a plan annually to monitor the possible contamination of foodstuffs (milk and dairy products, eggs, meat, fish, and seafood) by radionuclides. The objective of this plan, set up after the Chernobyl accident (and revised in 2008), is to ensure that there is no contamination of any food produced in the neighborhood of nuclear facilities.
The Directorate General for Competition, Consumer Rights and the Protection against Fraud (DGCCRF) carry out equivalent monitorings on vegetable foodstuffs.
The Directorate-General for Health (DGS) and the Regional Health Agencies (ARS) organize the monitoring of water quality (drinking water, recreational water, domestic hot water, bottled water, wastewater ...).
As for the Associations, the Association for Radioactivity Monitoring in Western France (ACRO) conducts regular monitoring of radioactivity in the environment throughout the Seine-Normandy basin, and also conduct investigations in other places on request from citizens, from environment protection associations or from Local Information Commissions and Committees (CLI). Not to mention members of the national network of physico-chemical air quality (ALQA) measurements are equipped with automatic sensors for continuous measurement of atmospheric radioactivity.
This set of measurements, also fed into the RNM database, gives an overview of the territory radioactivity level in various environmental compartments and foodstuff.
FROM SAMPLING TO MEASUREMENT: C14 ACTIVITY IN MILK
The measurement of C14 in biological samples requires complex and delicate methods which are used both for the carbon-14 dating technique and for the quantification of the carbon-14 activity of an environmental sample.
Once the sample has been taken in the field (1), it must be quickly packaged to avoid any degradation, then sent to the laboratory to undergo various treatments. Lyophilization of milk (2) allows better combustion of the sample.
After weighing (3), the sample of freeze-dried milk undergoes combustion (4) which transforms the carbon into CO2. From the collected CO2, a stepwise chemical operation to synthesize Benzene (C6H6) is carried out (5). In this liquid form, the carbon-14 content of the sample will be measured by liquid scintillation (6).
Several months may be needed from collection to restitution of the radioactivity measurement.
Sample of milk from a producer/grower of a geographical zone, selected for its representativeness
Milk is lyophilized to decrease sample volume and facilitate its combustion
The weighing should be as precise as possible to determinate the 14-carbon activity in the sample
Carbon present in sample is converted in CO2 by oxydative combustion
BENZENE SYNTHETIS FROM CO2
Carbonic gas chemically reacts with lithium to create lithium carbide
10 Li + 2 CO2 → Li2C2 + 4 Li2O
Which reacts with water to constitute acetylene (C2H2)
Li2C2 + 2 H2O → C2H2 + 2 LiOH
Benzene is then generated by trimerization of acetylene
3 C2H2 → C6H6
Synthetized benzene is measured by liquid scintillation. A « scintillating » liquid, which reacts with benzene, is added, then each sample are counted few hours. Carbon-14 activity is at last determinated by comparison with a reference sample