I N S T I T U T D E P R O T E C T I O N E T D E S Û R E T É N U C L É A I R E

IPSNbooklets To know

and understand

the evolution

of radioactivity

in the environment.

Radioecology

Both natural and artificial radionuclides can be found throughout 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.

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

Radioecology in the world and in FranceStudies on radioecology have been developed from 1940 up to the present dayin parallel with military and civil nuclear activities.

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

Radioecology toolsMeasurements on samples taken in the field and laboratory work are the basisfor development of software programmes used to predict dosimetric impact.

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

Radioecology of inland watersLiquid radioactive waste produced by nuclear facilities located along riversis discharged into fresh water.

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

Radioecological studies in the fieldAround a nuclear power station - Radioactivity levels are regularly controlled in the differentenvironments to measure the radioecological impact caused by waste from the power station.

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

A permanent observatory and instant information

All you need to know about radioecology

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

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

Given the presence of radionuclides in all ecosystemsand the complexity of the transfer processes,radioecologists work in three main environments in thebiosphere: the marine aquatic environment, the inlandaquatic environment and the land environment.

From the picture …Radionuclides are scattered into the air and water, settleon the soil and sediments, migrate into the food chains …and thus can affect man.

What is radioecology?11

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Air, land, water and living organisms,including humanbeings, make up the biosphere whichcan be subdivided into ecological unitscalled "ecosystems".A river, a lake, an ocean, a mountainchain, a tropical forest,a town or a desert are ecosystems. breathing

nutritionmeat - milk - vegetables

liquid effluents

gas effluents

transfers

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… to the model …The environment can be depicted by a series of boxesthrough which radionuclides circulate. Radioecologistsseek to measure the concentration of the radionuclides ineach box and understand their transfer mechanisms.

… to predict the dosimetric impact Radioecology provides data used in calculating thedosimetric impact. Whether the waste be controlled oraccidental, radioecology helps provide answers topotential questions from public authorities, the nuclearindustry, the media or the public at large.

Wet and dry deposits

Nutrition

Roottransfers

DrainagemigrationDeposits Irrigation

Atmosphere

Water

Sediments Soils

Plants

Animals

Significant events

The term "radioecology" first appeared in 1935 but onlybecame widely used during the 1950s. It probablyemerged from the combination of "radioactivity" and"ecology". The first radioecological work was publishedin Geneva in 1955 during the first international meetingon the use of nuclear energy in the Pacific.

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Radioecology in the world and in France2

i n t h e w o r l d … a n d i n F r a n c e

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 laboratoriesradioecology 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)

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The two main public bodies involved in the field ofradioecology in France are IPSN and OPRI (Office deprotection contre les rayonnements ionisants). IPSNcarries out radioecological studies in the framework of itsactivities in research and assessment. Its department forthe protection of the environment is organised aroundthemes of study and has several sites.

OPRI is responsible for the supervision and regulatorycontrol of radioactivity in the environment. It managesseveral warning networks which allow the authorities toreact immediately should abnormal radioactivity levels bedetected in France.

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Location of IPSN laboratories ( ) and OPRI agencies ( ).

Fontenay-aux-RosesSaclay

Orsay

Octeville

Cadarache

Toulon

La Hague

AgenAvignon

Angers

Le Vésinet

•Radioecological studies on the Atlantic seaboard

•Experimental radioecology

•Modelling and validation of transfers of radionuclides in the environment

•Organisation of environmental data

•Studies and intervention relating to radon and atmospheric contaminants

• Inland radioecological studies andresearch on the Mediterranean

••

Themes of the radioecologicalstudies developed at IPSN.

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Origins of radionuclides3

Sample Activity (roughly speaking) Predominant radionuclide

Outside air between 1 and 100 Bq/m3 radon-222Air inside houses between 10 and 10,000 Bq/m3 radon-222Sedimentary 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-40Mineral water between 2 and 4 Bq/l potassium-40Milk 80 Bq/l potassium-40Potato 150 Bq/kgHumans 120 Bq/kg potassium-40 and carbon-14

Humans are continuously exposed to both natural andartificial radiation.

Natural radioactivityOf the 340 different atoms (more precisely called"nuclides") found in nature, 70 are radioactive. Theseradionuclides (see P. 21) can be found throughout theenvironment … including in the human body.

Artificial radioactivity1. Atmospheric tests of nuclear weaponsAt the time of the explosions, radionuclides (tritium,ruthenium-106, caesium-137, strontium-90…) werepropelled into the upper atmosphere and then settled on thecontinents and oceans in a relatively uniform manner. Over aperiod of 35 years these atmospheric tests released a quantityof radionuclides equivalent to 500 times the waste from theChernobyl accident.

Of the more than 2,000nuclear weapons testscarried out throughoutthe world, 423 took placein the atmospherebetween 1945 and 1981(USA: 193, USSR: 142,France: 45, Great Britain: 21, China: 22).

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

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2. Accidents at nuclear plantsWhen the Chernobyl accident occurred, radionuclides weredeposited over the entire European continent (iodine-131,caesium-137, caesium-134, ruthenium-106 …).

3. Controlled nuclear industrial wasteNuclear facilities (nuclear power stations, fuel reprocessingplants) are authorised to release radionuclides into riversor the sea (liquid effluents) or the air (gas effluents).

4. Fall of satellitesSeveral satellites powered by a nuclear source have fallen.In 1964, the re-entry of a satellite into the atmosphereover the Indian Ocean scattered plutonium-238 acrossthe world. Traces of this radionuclide were found onFrench territory.

Three accidentsreleased significantquantities of radionuclides into the environment:Windscale (Great Britain, 1957),Kyshtym (Russia, 1957) and Chernobyl(Ukraine, 1986).

computation tools Evaluation

of the radioecological (Bq)and dosimetric (Sv) impact

PREDICT

FieldTaking samples

Measuring contamination (Bq)

MEASURING

LaboratoryReconstructing

simplified ecosystemsUnderstanding transfer

mechanisms

MODELLING

Validationby comparing measurements

against predictions

Determinationof mechanismsto be studied

Formulationof experimental

results

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Radioecology tools4

Measuring instruments are used to determine the exactconcentrations of radionuclides in samples taken in thefield (for example, from a potato and the soil in which itis grown). It is extremely difficult, however, to determineon site the mechanisms of transfer (how the potatoabsorbs the radionuclides by drawing from the earth'sreserves). That is why radioecologists conductexperimental work in laboratories.The aim is to construct radionuclide transfer modelscapable of quickly predicting the impact of radioactivecontamination in a given area by using a restrictednumber of radioactive measurements from samples takenin the field.

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Measuring the samplesThe samples taken are analysed in specialised facilitiescapable of measuring radionuclides, even if there is only atrace, from any environment: air, water, land, sediments,plants, living organisms.To facilitate the measuring, radioecologists choosesubstances in the field which fix the radionuclides (such assediments) or species called "bioindicators" whichconcentrate the radionuclides (as in the case of mosses,lichens, mussels, oysters…).

Experimental work and modellingIn order to understand the transfer mechanisms,radioecologists reconstruct simplified ecosystems in thelaboratory. They contaminate cultures with variousradionuclides by changing the nature of the soil and theclimatic conditions.This work results in the development of models simulatingthe transfer of radionuclides between the different partsof the environment.

Software for predicting dosimetric impact Radioecologists build computation tools based on bothmeasurement results and transfer models which take intoaccount local ecological conditions.In the event of accidental release of radionuclides into theenvironment, these tools predict the dosimetric impact onthe population groups affected and provide invaluabletechnical assistance to the "crisis managers".

Measuring in shieldedundergroundroom.

Cultures in the laboratory.

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Marine radioecology5

Marine radioecology studies the evolution of radioactivelevels in the open sea and in coastal areas. It conductsexpert assessments on the effects of waste released intothe sea from nuclear facilities.Naturally-occurring radioactivity in the sea is around13,000 Bq/m3, basically due to potassium-40. Artificialradioactivity is added to this, caesium-137 being one ofthe main elements.

The oceans are contaminated in a relatively uniformmanner by fallout from atmospheric nuclear weapontesting. Seas which are not very deep and estuaries aresubject to more pronounced contamination due to therelease of waste from the fuel reprocessing plants ofSellafield (Great Britain) into the Irish Sea and La Hague(France) into the English Channel. These discharges havebeen decreasing sharply for more than ten years.

Estimate of the meandistribution of the caesium-137concentration in Bq/m3.

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Radionuclide transfersRadionuclides are spread by currents. They fix themselvesto particles suspended in water which gradually settle onthe seabed and are stored in sediments which maycontain radioactivity levels 100 to 10 million times higherthan that of seawater.Through physiological processes such as water filtering,marine organisms can accumulate certain radionuclideswith a concentration factor of 5 to 100,000 compared toseawater.The bioindicators used are, for example, algae of thefucus species, oysters, mussels, scallops, crab or lobster.

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Certain radionuclides released into the sea representremarkable tools for oceanographers. For example, bytracing tritium, one of the radionuclides found in thewaste released from the La Hague plant, calculationsrevealed that water took 110 to 152 days to flow from LaHague to the Straits of Dover.

Distribution of tritium in the English Channel(measuring campaigncarried out in 1994).

Mussels.

AtlanticOcean

France

English Channel

Great Britain

La Hague

+ : Measurement points

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Radioecology of inland waters6

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

Storage centre Manche

Nogent-sur-Seine

Chooz

Storage centre Aube

Cattenom

Fessenheim

DampierreSaint-Laurent

Chinon

Civaux

Belleville

Bugey

Saint-Alban

Tricastin

Marcoule

Cruas

Golfech

Le Blayais

La Hague

Garonne

Vienne

Seine

Meuse

Moselle

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Loire

EDF nuclear power plants

Fuel reprocessing plants

Storage centres for radioactive waste

In France, 15 nuclear sitesout of 19 and variousfacilities concerning the fuel cycle are locatedalong rivers. The others are on the Channel or the North Sea coast.

Radionuclide transfersThe same radionuclide concentration phenomenaoccurring in the marine ecosystem are also found infresh waters. But the concentration factors in the livingorganisms differ between fresh water and seawater. Thepresence of heavy metals (zinc, lead, and others) in thewaterways also modify the intensity of radionuclidefixation.The bioindicators used are molluscs such as the Asianclam and the Zebra mussel which are very plentifultogether with water mosses.

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

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Laboratory experiments are essential to understandingtransfer mechanisms. Here one can evaluate theimportance of each parameter: the type and chemicalnature of the radionuclide, the mixture of contaminants(radioactive or not), the temperature and pH of water, etc.

Asian clams.

Hydrobiology experimental hall (Cadarache).

Example of an inland waterecosystemstudied in the laboratory.

The land ecosystem is complex: the environments (soil,surface water, underground water), the topography(plains, mountains), the vegetation (grassland, cultivatedareas, forests) and the food chains (plant and animal) areextremely varied.The contamination of the land ecosystem is usually dueto atmospheric deposits. When the Chernobyl accidentoccurred, the contaminated air masses travelledthousands of miles. Large disparities exist in the surfaceactivities (in Bq/m2) inside a country or a region: theradionuclides present in the atmosphere settle graduallyaccording to the vagaries of the wind - deposits are moreconcentrated during rainy periods , when encounteringa relief or high vegetation .

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Land radioecology7

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Radionuclide transfersRadionuclides deposited by wind gusts or rain directlycontaminate plant leaves ( . The radionuclides then migrateto the earth ( , followed by transfers towards the roots (3).The principal bioindicators studied are mosses andlichens.Certain animals become contaminated by the ingestionof plants; the most common food chain is:

grass -> cow -> meat and milk.

The effects of atmospheric pollution vary notably withthe seasons, as the radionuclides can settle on cultivatedor uncultivated agricultural land, on seedlings or ripevegetation, while the cows are in a cowshed or grazingoutside.

One of the experiments for the study of radionuclidetransfer involves taking a block of earth in the field andplacing it in a laboratory under controlled climaticconditions. Here one can observe various cultures (corn,vines, beans…) which can be contaminated at differentstages in their growth.

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Taking samples in the field.Culture in the laboratory.

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Radioecological studies in the field 8

In-field studies trace radioactivity levels in space and time.Whether they involve a nuclear power station, a fuelreprocessing plant or an area affected by deposits fromChernobyl, 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 theecosystem.

•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.

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Around a nuclear power station Before startup of a nuclear power station, a reading of theradioactivity levels of the water, soil, plants and foodproducts is carried out in a circle of some 8 to 25 milesaround the site. This is the radioecological zero pointwhich serves as a reference.

Subsequently, an annual follow-up and an assessmentevery ten years provides a precise measurement of theradioecological impact of the power station's waste andits evolution over time.

Sediments are taken from thebank using a "Berthois cone".It is thrown out then broughtback, scraping the bottom.

Fish are often caught using electric fishing methods.

Aquatic plants are collected then washed carefully.

Agricultural products areselected after a food survey.

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Radioecological studies in the field 9

The Nord-Cotentin Radioecology GroupIn 1997 the Ministers for the Environment and Healthdecided to create a Nord-Cotentin Radioecology Group,whose mission was to take an inventory of radioactive wastefrom the nuclear plants in Nord-Cotentin (mainly the fuelreprocessing plant at La Hague) and to assess the dosesreceived by the population as well as the risks associatedwith leukaemia.Over fifty specialists from extremely different fieldsparticipated in the group's work; research and assessmentbodies, control bodies, operators, information commissions,experts from associations and foreign institutes.Two complementary methods were implemented. Onerelied on the knowledge of wastes and on the models ofradioactivity transfer to human populations, while the otherconsisted in collecting the results of more than 500,000existing radioactivity measurements from the differentcomponents of the environment so as to verify the validityof the models for the population. It was thus possible toestimate the doses and associated risks from knowledge ofthe environmental contamination and the living habits ofthe population groups concerned.

Limpets are very plentiful on rocks where peoplegather them at low tide. Knowledge of their radioactivitylevel can be used to evaluate the dosesreceived by people who eat them.

Evolution of the concentrationof caesium-137in limpets.

1978 1988 1998

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4

Bq/kg

The Mercantour workshop zoneIn the days following the Chernobyl accident, the passageof contaminated air masses over the French Alps duringheavy snowfalls led to contaminated snow being depositedat high altitude. A study has been carried out in theMercantour mountains (Southern Alps) to produce a mapof the soil radioactivity.A workshop zone of 1.35 km2 was first chosen betweenthe Isola 2000 station and the Lombarde pass.Measurements of caesium-137 showed evidence ofimportant differences in surface activity depending on the typeof soil. Whereas the average is approximately 10,000 Bq/m2,areas of concentration of more than 100,000 Bq/m2 werefound in basins in the grasslands and at the foot of larchforests where the spring firn fields linger.

Observations made in this zone have traced the migrationof caesium-137 deposited in May 1986 and led to acartographic model which links the surface activities to thetype of soil (scree, forest, grassland) and to thetopography (slope, basin).Through extrapolation, the model can also be used tostudy vast mountain areas and to identify the "troublespots" where the concentrations of caesium-137 resultingfrom the Chernobyl accident can be found. 19

Partial view of the workshopzone above Isola2000.

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A permanent observatory and instant information

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Bibliographical references

Histoire de l'écologie285 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: thereferences can be found in the library section on the websitewww.ipsn.fr.

For further information

www.ipsn.fr/operaThe Permanent Environmental Radioactivity Observatory(OPERA) monitors radioactivity levels in theenvironment in France. It is supported by a network ofover 30 stations throughout the country (includingPapeete and Saint-Denis de la Réunion) that arerepresentative of the main environments. This tool offersa significant means of informing the public, which hasimmediate access to the results.

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Algeciras

Caesium-137activity inatmosphericaerosols (mBq/m3)observed in frenchsampling stations.

The peak in 1998is due to the accidentalincineration of a caesium-137 source in a steel plant in Algeciras.

Photos by: Photothèque IPSN / Claude Cieutat D.R. - Campagne Campagne 21

Dosimetric impactThe dosimetric impact is determined by evaluating theradiation to which a population group in exposed. It isexpressed in sieverts (Sv). A sub-multiple, the millisievert (1 mSv = 0.001 Sv), is frequently used.

Reference groupA reference group is a group of people more specificallyexposed to a source of radiation due to their geographicallocation, their way of life or their eating habits.

Useful definitions in radioecologyRadionuclides

Radionuclides are atoms with a radioactive nucleus. Forexample, carbon-14 is a radionuclide present in very smallamounts in carbon. The symbolic representation of thenucleus is shown above, but it is generally written as 14C orcarbon-14.

Radioecological impactThe radioecological impact is determined by measuring theradioactivity of the different constituents that make up anenvironment, in other words the radionuclide concentrationpresent in the environment. The unit of activity is abecquerel (Bq) which is equivalent to the decay of oneradionuclide per second. In radioecology, activity is alwaysexpressed with respect to a volume, mass or surface area.

atomic mass :14 = 6 protons + 8 neutrons

atomic number :6 protons C

14

6

Bq/l

Bq/m

Bq/kg

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IPSN

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For further information,visit our website : www.ipsn.fr

IPSN: research and expertiseThe Institut de protection et de sûreté nucléaire (IPSN) carries outresearch and assessments to control nuclear risk and its effect onhuman health and the environment, covering such areas as safetyof nuclear facilities, the protection of workers, the public, and theenvironment, and safety in transporting radioactive materials.Although it acts mainly for public authorities, it often works inpartnership with its counterparts overseas.

Radionuclides, both natural and artificial, can be found throughoutthe environment and can affect people, mainly through the foodchains. 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 radiationreceived by the population.

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