INSTITUT DE PROTECTION ET DE SÛRETÉ NUCLÉAIRE

IPSN To know booklets Radioecology and understand the evolution of radioactivity in the environment. The use of nuclear energy in both military and civil applications has led scientists to study the fate of radioactive products called "radionuclides" (see P. 21) released in the environment since the beginning of the 1940s. This concern has given birth to an ecological discipline - radioecology.

Both natural and artificial radionuclides can be found throughout the environment. All you need to know about radioecology

1 What is radioecology? Radioecologists seek to understand the evolution of radionuclides in the environment and to collect data to predict their dosimetric impact.

2 Radioecology in the world and in France Studies on radioecology have been developed from 1940 up to the present day in parallel with military and civil nuclear activities.

3 Origins of radionuclides Weapons testing, accidents at facilities, controlled waste have released artificial radionuclides into the environment which are added to natural-occurring radionuclides.

4 Radioecology tools Measurements on samples taken in the field and laboratory work are the basis for development of software programmes used to predict dosimetric impact.

5 Marine radioecology Radioecologists carry out assessments on the effects of dumping waste from nuclear facilities at sea.

6 Radioecology of inland waters Liquid radioactive waste produced by nuclear facilities located along rivers is discharged into fresh water.

7 Land radioecology The radionuclides in the land ecosystem affect human health mainly through the food chain: plants animals meat or milk.

8 Radioecological studies in the field Around a nuclear power station - Radioactivity levels are regularly controlled in the different environments to measure the radioecological impact caused by waste from the power station.

9 Radioecological studies in the field The Nord-Cotentin Radioecology Group - In Nord-Cotentin, an inventory of radioactive waste from a fuel reprocessing plant was conducted. Mercantour workshop zone - In the Mercantour area, a "workshop zone" was created to trace the migration of the caesium-137 released in May 1986 after the Chernobyl accident.

10 A permanent observatory and instant information

1 11 What is radioecology?

The purpose of radioecology is to detect the presence of radionuclides in the environment, to research their origins and to understand their process of transfer and their concentration in ecosystems.

Its aim is to evaluate the impact of both natural and artificial radioactivity on the environment (radioecological impact) and on the population (dosimetric impact) (see P. 21). These studies are based on the same approach as those relating to other chemical polluting agents such as heavy metals (lead, zinc, etc.) or nitrates.

Given the presence of radionuclides in all ecosystems and the complexity of the transfer processes, radioecologists work in three main environments in the biosphere: the marine aquatic environment, the inland aquatic environment and the land environment.

From the picture … Air, land, water Radionuclides are scattered into the air and water, settle and living organisms, on the soil and sediments, migrate into the food chains … including human beings, make up and thus can affect man. the biosphere which can be subdivided into ecological units gas effluents called "ecosystems". A river, a lake, an ocean, a mountain chain, a tropical forest, a town or a desert liquid effluents are ecosystems. transfers breathing

nutrition meat - milk - vegetables 2 … to the model … The environment can be depicted by a series of boxes through which radionuclides circulate. Radioecologists seek to measure the concentration of the radionuclides in each box and understand their transfer mechanisms.

Wet and dry deposits Atmosphere

Sediments Soils Drainage migration Deposits Irrigation Water Root transfers

Plants

Nutrition

Animals

… to predict the dosimetric impact Radioecology provides data used in calculating the dosimetric impact. Whether the waste be controlled or accidental, radioecology helps provide answers to potential questions from public authorities, the nuclear industry, the media or the public at large.

3 2 Radioecology in the world and in France

The term "radioecology" first appeared in 1935 but only became widely used during the 1950s. It probably emerged from the combination of "radioactivity" and "ecology". The first radioecological work was published in Geneva in 1955 during the first international meeting on the use of nuclear energy in the Pacific.

Significant events in the world … and in France

1940-1950 • First nuclear weapons tests • Divergence of ZOE reactor • Nuclear explosions at Hiroshima (Fontenay-aux-Roses - 1948) and Nagasaki

••••••••••••••••••• •••••••••••••••••••••••••••• 1950-1960 • Use of radionuclides in biology • Creation of an "ecology" group and agriculture at CEA • Kyshtym accident in the USSR • Beginning of scientific and at Windscale in Great Britain publications

••••••••••••••••••• •••••••••••••••••••••••••••• 1960-1970 • First international congress on • Creation of radioecological laboratories radioecology in the USA (1961) at CEA • Radioecology congress organised • First congress organised by Vienna Agency (IAEA – 1966) in France (Cadarache, 1969)

••••••••••••••••••• •••••••••••••••••••••••••••• 1970-1980 • Oil crisis, rise of nuclear energy • First reference states before • Accident at Three Mile Island installation of nuclear power in the USA stations (Bugey, Fessenheim)

••••••••••••••••••• •••••••••••••••••••••••••••• 1980-1990 • Accident at Chernobyl in Ukraine • Experimental studies (1986) on the effects of an accident on the environment: RESSAC programme (Cadarache)

••••••••••••••••••• •••••••••••••••••••••••••••• 1990-2001 • Development of studies • Study of the impact on the storage of radioactive waste of the Chernobyl accident (Vosges, Mercantour, Corsica)

4 The two main public bodies involved in the field of radioecology in France are IPSN and OPRI (Office de protection contre les rayonnements ionisants). IPSN carries out radioecological studies in the framework of its activities in research and assessment. Its department for the protection of the environment is organised around themes of study and has several sites.

•Radioecological studies on the Atlantic seaboard La Hague Octeville •Experimental radioecology Le Vésinet Fontenay-aux-Roses Saclay Orsay •Modelling and validation of transfers Angers of radionuclides in the environment

•Organisation of environmental data

•Studies and intervention relating to radon and atmospheric contaminants Avignon Agen Cadarache • Inland radioecological studies and research on the Mediterranean Toulon

Location of IPSN laboratories ( • ) Themes of the radioecological and OPRI agencies ( • ). studies developed at IPSN.

OPRI is responsible for the supervision and regulatory control of radioactivity in the environment. It manages several warning networks which allow the authorities to react immediately should abnormal radioactivity levels be detected in France.

5 3 Origins of radionuclides

Humans are continuously exposed to both natural and artificial radiation.

Natural radioactivity Of the 340 different atoms (more precisely called "nuclides") found in nature, 70 are radioactive. These radionuclides (see P. 21) can be found throughout the environment … including in the human body.

Sample Activity (roughly speaking) Predominant radionuclide Outside air between 1 and 100 Bq/m3 radon-222 Air inside houses between 10 and 10,000 Bq/m3 radon-222 Sedimentary land 1,000 Bq/kg uranium-238, thorium-232 and their daughter products, potassium-40 Granite 3,000 Bq/kg uranium-238, thorium-232 and their daughter products, potassium-40 Seawater 13 Bq/l potassium-40 Mineral water between 2 and 4 Bq/l potassium-40 Milk 80 Bq/l potassium-40 Potato 150 Bq/kg Humans 120 Bq/kg potassium-40 and carbon-14

Artificial radioactivity Of the more than 2,000 1. Atmospheric tests of nuclear weapons nuclear weapons tests At the time of the explosions, radionuclides (tritium, carried out throughout the world, 423 took place ruthenium-106, caesium-137, strontium-90…) were in the atmosphere propelled into the upper atmosphere and then settled on the between 1945 and 1981 (USA: 193, USSR: 142, continents and oceans in a relatively uniform manner. Over a France: 45, period of 35 years these atmospheric tests released a quantity Great Britain: 21, China: 22). of radionuclides equivalent to 500 times the waste from the Chernobyl accident.

6 Three accidents 2. Accidents at nuclear plants released significant When the Chernobyl accident occurred, radionuclides were quantities of radionuclides deposited over the entire European continent (iodine-131, into the environment: caesium-137, caesium-134, ruthenium-106 …). Windscale (Great Britain, 1957), Kyshtym (Russia, 1957) and Chernobyl (Ukraine, 1986). 3. Controlled nuclear industrial waste Nuclear facilities (nuclear power stations, fuel reprocessing plants) are authorised to release radionuclides into rivers or the sea (liquid effluents) or the air (gas effluents).

Principal radionuclides… in liquid effluents in gas effluents

Nuclear reactor tritium, cobalt-60, manganese-54 krypton-85, xenon-133, silver-110, antimony-124, iodine-131, iodine-131, tritium, caesium-137 carbon-14

Reprocessing plant tritium, caesium-137, ruthenium-106, tritium, krypton-85, strontium-90, antimony-125, iodine- xenon-133, iodine-129, 129, carbon-14 carbon-14

4. Fall of satellites Several satellites powered by a nuclear source have fallen. In 1964, the re-entry of a satellite into the atmosphere over the Indian Ocean scattered plutonium-238 across the world. Traces of this radionuclide were found on French territory.

7 4 Radioecology tools

Measuring instruments are used to determine the exact concentrations of radionuclides in samples taken in the field (for example, from a potato and the soil in which it is grown). It is extremely difficult, however, to determine on site the mechanisms of transfer (how the potato absorbs the radionuclides by drawing from the earth's reserves). That is why radioecologists conduct experimental work in laboratories. The aim is to construct radionuclide transfer models capable of quickly predicting the impact of radioactive contamination in a given area by using a restricted number of radioactive measurements from samples taken in the field.

Determination of mechanisms to be studied

Laboratory Field Reconstructing Taking samples simplified ecosystems Measuring contamination (Bq) Understanding transfer MEASURING mechanisms MODELLING

Validation Formulation by comparing measurements of experimental against predictions results computation tools Evaluation of the radioecological (Bq) and dosimetric (Sv) impact PREDICT

8 Measuring the samples The samples taken are analysed in specialised facilities capable of measuring radionuclides, even if there is only a trace, from any environment: air, water, land, sediments, plants, living organisms. To facilitate the measuring, radioecologists choose substances in the field which fix the radionuclides (such as sediments) or species called "bioindicators" which

Measuring concentrate the radionuclides (as in the case of mosses, in shielded lichens, mussels, oysters…). underground room.

Experimental work and modelling In order to understand the transfer mechanisms, radioecologists reconstruct simplified ecosystems in the laboratory. They contaminate cultures with various radionuclides by changing the nature of the soil and the climatic conditions. This work results in the development of models simulating Cultures the transfer of radionuclides between the different parts in the laboratory. of the environment.

Software for predicting dosimetric impact Radioecologists build computation tools based on both measurement results and transfer models which take into account local ecological conditions. In the event of accidental release of radionuclides into the environment, these tools predict the dosimetric impact on the population groups affected and provide invaluable technical assistance to the "crisis managers".

9 5 Marine radioecology

Marine radioecology studies the evolution of radioactive levels in the open sea and in coastal areas. It conducts expert assessments on the effects of waste released into the sea from nuclear facilities. Naturally-occurring radioactivity in the sea is around 13,000 Bq/m3, basically due to potassium-40. Artificial radioactivity is added to this, caesium-137 being one of the main elements.

Irish English Sea Channel 55 10

2,5 3,3 2,5 5,4 3,0 2,0 2,6 2,4 1,5 2,9 1,9 2,5 2,3 Estimate of the mean distribution 0,1 0,7 0,8 0,4 of the caesium-137 concentration in Bq/m3.

The oceans are contaminated in a relatively uniform manner by fallout from atmospheric nuclear weapon testing. Seas which are not very deep and estuaries are subject to more pronounced contamination due to the release of waste from the fuel reprocessing plants of Sellafield (Great Britain) into the Irish Sea and La Hague (France) into the English Channel. These discharges have been decreasing sharply for more than ten years.

10 Radionuclide transfers Radionuclides are spread by currents. They fix themselves to particles suspended in water which gradually settle on the seabed and are stored in sediments which may contain radioactivity levels 100 to 10 million times higher than that of seawater. Through physiological processes such as water filtering, marine organisms can accumulate certain radionuclides with a concentration factor of 5 to 100,000 compared to seawater. The bioindicators used are, for example, algae of the Mussels. fucus species, oysters, mussels, scallops, crab or lobster.

51 7500 Great Britain 6500 5500 4500 3500 2500 50 1750 1300 1150 English Channel 1050 950 La Hague 850 49 750 France 650 550 Atlantic 450 Ocean 350 + : Measurement points 250 48 150 -6 -5 -4 -3 -2 -1 0 1 2 Tritium Bq/m3

Distribution of tritium in the English Channel (measuring campaign carried out in 1994). Certain radionuclides released into the sea represent remarkable tools for oceanographers. For example, by tracing tritium, one of the radionuclides found in the waste released from the La Hague plant, calculations revealed that water took 110 to 152 days to flow from La Hague to the Straits of Dover. 11 6 Radioecology of inland waters

Bodies of fresh water that receive liquid radioactive waste from nuclear facilities and laboratories (research centres, hospitals) form a group of ecosystems studied in radioecology.

La Hague Chooz Meuse Rhin Seine Cattenom Storage centre Manche Moselle Fessenheim

Nogent-sur-Seine Storage centre Aube

Saint-Laurent Dampierre Chinon Belleville

Civaux

Loire Bugey Vienne Saint-Alban

Rhône

Le Blayais Cruas Golfech Tricastin Garonne

Marcoule

In France, 15 nuclear sites out of 19 and various facilities concerning the fuel cycle are located along rivers. The others are on the Channel or the North Sea coast. EDF nuclear power plants

Fuel reprocessing plants

Storage centres for radioactive waste 12 Radionuclide transfers The same radionuclide concentration phenomena occurring in the marine ecosystem are also found in fresh waters. But the concentration factors in the living organisms differ between fresh water and seawater. The presence of heavy metals (zinc, lead, and others) in the waterways also modify the intensity of radionuclide fixation. The bioindicators used are molluscs such as the Asian Asian clams. clam and the Zebra mussel which are very plentiful together with water mosses.

A living organism's radioactivity results from a balance between contamination and decontamination . Contamination occurs through the ingestion of water and food. Decontamination is due to the physical decay of the radionuclides and their biological elimination.

Example of an inland water ecosystem studied in the laboratory.

Laboratory experiments are essential to understanding transfer mechanisms. Here one can evaluate the importance of each parameter: the type and chemical nature of the radionuclide, the mixture of contaminants (radioactive or not), the temperature and pH of water, etc. Hydrobiology experimental hall (Cadarache). 13 7 Land radioecology

The land ecosystem is complex: the environments (soil, surface water, underground water), the topography (plains, mountains), the vegetation (grassland, cultivated areas, forests) and the food chains (plant and animal) are extremely varied. The contamination of the land ecosystem is usually due to atmospheric deposits. When the Chernobyl accident occurred, the contaminated air masses travelled thousands of miles. Large disparities exist in the surface activities (in Bq/m2) inside a country or a region: the radionuclides present in the atmosphere settle gradually according to the vagaries of the wind - deposits are more concentrated during rainy periods 1 , when encountering a relief 2 or high vegetation 3 .

1

2

3

14 Radionuclide transfers Radionuclides deposited by wind gusts or rain directly 1 1 contaminate plant leaves ( . The radionuclides then migrate to the earth (2 , followed by transfers towards the roots (3)3 . The principal bioindicators studied are mosses and lichens. Certain animals become contaminated by the ingestion of plants; the most common food chain is:

2

grass -> cow -> meat and milk.

3 The effects of atmospheric pollution vary notably with the seasons, as the radionuclides can settle on cultivated or uncultivated agricultural land, on seedlings or ripe vegetation, while the cows are in a cowshed or grazing outside.

Taking samples in the field. Culture in the laboratory. One of the experiments for the study of radionuclide transfer involves taking a block of earth in the field and placing it in a laboratory under controlled climatic conditions. Here one can observe various cultures (corn, vines, beans…) which can be contaminated at different stages in their growth.

15 8 Radioecological studies in the field

In-field studies trace radioactivity levels in space and time. Whether they involve a nuclear power station, a fuel reprocessing plant or an area affected by deposits from Chernobyl, these studies follow the same scenario:

•Define the scope of the study.

•Define the local ecosystem: topography, hydrology, demography, type of soil, cultivation and animal raising, meteorology.

•Define the population reference groups (see P. 21).

•Determine the environments and the species to be taken from the ecosystem.

•Choose the locations and frequency of sample taking.

•Take the samples and store them.

•Measure the radioactivity, register the results in a database, interpret the results.

•Publish the results.

16 Around a nuclear power station Before startup of a nuclear power station, a reading of the radioactivity levels of the water, soil, plants and food products is carried out in a circle of some 8 to 25 miles around the site. This is the radioecological zero point which serves as a reference.

Sediments are taken from the Fish are often caught using bank using a "Berthois cone". electric fishing methods. It is thrown out then brought back, scraping the bottom.

Aquatic plants are collected Agricultural products are then washed carefully. selected after a food survey.

Subsequently, an annual follow-up and an assessment every ten years provides a precise measurement of the radioecological impact of the power station's waste and its evolution over time.

17 9 Radioecological studies in the field

The Nord-Cotentin Radioecology Group In 1997 the Ministers for the Environment and Health decided to create a Nord-Cotentin Radioecology Group, whose mission was to take an inventory of radioactive waste from the nuclear plants in Nord-Cotentin (mainly the fuel reprocessing plant at La Hague) and to assess the doses received by the population as well as the risks associated with leukaemia. Over fifty specialists from extremely different fields participated in the group's work; research and assessment bodies, control bodies, operators, information commissions, experts from associations and foreign institutes. Two complementary methods were implemented. One relied on the knowledge of wastes and on the models of radioactivity transfer to human populations, while the other consisted in collecting the results of more than 500,000 existing radioactivity measurements from the different components of the environment so as to verify the validity of the models for the population. It was thus possible to Limpets estimate the doses and associated risks from knowledge of are very plentiful on rocks where people the environmental contamination and the living habits of gather them at low tide. the population groups concerned. Knowledge of their radioactivity level can be used to evaluate the doses received by people who eat them.

Bq/kg

4 Evolution of the concentration

of caesium-137 2 in limpets.

18 1978 1988 1998 The Mercantour workshop zone In the days following the Chernobyl accident, the passage of contaminated air masses over the French Alps during heavy snowfalls led to contaminated snow being deposited at high altitude. A study has been carried out in the Mercantour mountains (Southern Alps) to produce a map of the soil radioactivity. A workshop zone of 1.35 km2 was first chosen between the Isola 2000 station and the Lombarde pass. Measurements of caesium-137 showed evidence of important differences in surface activity depending on the type of soil. Whereas the average is approximately 10,000 Bq/m2, areas of concentration of more than 100,000 Bq/m2 were found in basins in the grasslands and at the foot of larch forests where the spring firn fields linger.

Partial view of the workshop zone above Isola 2000. Observations made in this zone have traced the migration of caesium-137 deposited in May 1986 and led to a cartographic model which links the surface activities to the type of soil (scree, forest, grassland) and to the topography (slope, basin). Through extrapolation, the model can also be used to study vast mountain areas and to identify the "trouble spots" where the concentrations of caesium-137 resulting from the Chernobyl accident can be found. 19 10 A permanent observatory and instant information

www.ipsn.fr/opera The Permanent Environmental Radioactivity Observatory (OPERA) monitors radioactivity levels in the environment in France. It is supported by a network of over 30 stations throughout the country (including Papeete and Saint-Denis de la Réunion) that are representative of the main environments. This tool offers a significant means of informing the public, which has Caesium-137 immediate access to the results. activity in atmospheric 1000000 aerosols (mBq/m3) Chernobyl 100000 observed in french sampling stations. 10000 Atmospheric nuclear weapon testing The peak in 1998 1000 is due to the accidental Algeciras incineration 100 of a caesium-137 10 source in a steel plant in Algeciras. 1

0,1

1960 1970 1980 1990 2000 For further information Bibliographical references Histoire de l'écologie 285 p., 1988, PUF, P. Acot.

Dictionnaire encyclopédique de l'écologie et des sciences de l'environnement 822 p., 1993, Ediscience international, Paris, F. Ramade.

The collection IPSN - EDP Sciences This collection includes several books on radioecology: the references can be found in the library section on the website www.ipsn.fr. 20 Useful definitions in radioecology Radionuclides atomic mass : 14 = 6 protons + 8 neutrons 14 atomic number : 6 protons 6 C Radionuclides are atoms with a radioactive nucleus. For example, carbon-14 is a radionuclide present in very small amounts in carbon. The symbolic representation of the nucleus is shown above, but it is generally written as 14C or carbon-14.

Radioecological impact The radioecological impact is determined by measuring the radioactivity of the different constituents that make up an environment, in other words the radionuclide concentration present in the environment. The unit of activity is a becquerel (Bq) which is equivalent to the decay of one radionuclide per second. In radioecology, activity is always expressed with respect to a volume, mass or surface area.

Bq/kg

Bq/l Bq/m2

Dosimetric impact The dosimetric impact is determined by evaluating the radiation to which a population group in exposed. It is expressed in sieverts (Sv). A sub-multiple, the millisievert (1 mSv = 0.001 Sv), is frequently used. Reference group A reference group is a group of people more specifically exposed to a source of radiation due to their geographical location, their way of life or their eating habits.

Photos by: Photothèque IPSN / Claude Cieutat D.R. - Campagne Campagne 21 IPSN: research and expertise The Institut de protection et de sûreté nucléaire (IPSN) carries out research and assessments to control nuclear risk and its effect on human health and the environment, covering such areas as safety of nuclear facilities, the protection of workers, the public, and the environment, and safety in transporting radioactive materials. Although it acts mainly for public authorities, it often works in partnership with its counterparts overseas. Radionuclides, both natural and artificial, can be found throughout the environment and can affect people, mainly through the food chains. The purpose of radioecology is to detect radionuclides, measure their concentration, understand their methods of transfer, and supply data that can be used to estimate the radiation IPSN received by the population.

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