Methodology for assessment of
exposures to people following
nuclear accidents
Gerhard Proehl

Radionuclides released during the Chernobyl accident(1 PBq = 1015 Bq)
Volatility

Radionuclide

Half-life

Activity released (PBq)

Noble gases

Kr-85
Xe-13310.7 a
5.3 d

33
6500

Volatile elements

Te-129m
Te-132
I-131
I-133
Cs-134
Cs-136
Cs-137

33.6
3,3
8.0 d
20.8 h2.06 a13.1 d
30 a

240
1150
1760
910
47
36
85

Intermediately volatile elements

Sr-89
Sr-90
Ru-103
Ru-106
Ba-14050.5 d29.1
39.3 d368 d12.7 d

115
10
> 168
>73
> 240

Non-volatile elements
and fuel particles

Zr-95
Mo-99
Ce-141
Ce-144
Np-239Pu-238
Pu -239
Pu-241
Pu-242
Cm-24264 d2.75 d32.5 d284 d2.35 d87.7 a24065 a14.4 a376000 a
18.1 a

84
>72
84
59
400
0.015
0.013
2.6
0.00004
0.4

Releases of radionuclides to the terrestrial
environment (IAEA 2006, IAEA 2015)
Radionuclide

Release (PBq)

I-131

Chernobyl(IAEA 2006)
1760

Fukushima(IAEA 2015)100-400

Cs-13447

8.3-50Cs-137

85

7-20

Sr-90

10

0.003-0.14

Xe-1336500

6000-12000

Comparison Fukushima – Chernobyl (same scale)

Fukushima compared to Chernobyl:
comparable Cs-deposition levels but over smaller area
Fukushima, 2013/12/17

After Vandenhove et al., 20124

Exposure to people from releases of radionuclides to theenvironment
4 Exposure pathways

Radioecological modelDose from radionuclides in the passing radioactive plume
Dose = Activity in air × time × dose coefficient × shielding factor(mSv)(Bq/m3)(d)(mSv/d per Bq/m²)

Radiation dose from radionuclides deposited on
groundDose = Activity on the ground × time × dose coefficient ×(mSv)(Bq/m²)(d)(mSv/d per Bq/m²)

shielding factor

Radiation dose from inhalation during the passage of the
plume
Dose = Time integrated activity in air × breathing rate (age) × Dose coefficient(mSv)(Bq × d/m³)(m3/d)(mSv/Bq)

Radiation dose due to intake of food
Dose = activity (food) × food intake × Dose coefficient(mSv)(Bq/kg)(kg/d)

Activity concentrations in food

• Pronounced time-dependence• Can be determined by monitoring• Can be predicted by means of radioecological models(mSv/Bq)

Dose coefficients
Convert activity [Bq] in the environment into dose [Sv]

Dose coefficients
External exposure from radionuclides in the passing plume− Convert activity per unit air volume (Bq/m3) to a dose rate (Sv/s per Bq/m3)− Semi-infinite cloud− No shielding

External exposure from radionuclides deposited on the ground− Convert activity per unit area (Bq/m2) to a dose rate (Sv/s per Bq/m2)− Infinite area
− No shielding

Inhalation− Convert activity per unit activity inhaled (Bq) to a dose (Sv/Bq)

Ingestion− Convert activity per unit activity ingested (Bq) to a dose (Sv/Bq)

Calculated by ICRP

− Published in a number of ICRP publications 56 (1990), 72 (1996) and 119 (2012)− Age-groups: 3 months, 1, 5, 10, 15 years, adults− Values are given for effective dose:
Weighted mean of doses over all tissues and organs

Biokinetic model for intake of radionuclides with food anddrinking water (simplified according to ICRP)
Activity in foodIngestion

Upper
gastrointestinal-tract
Resorption by blood

Organs and tissues

Excretion

Lower gastro-intestinal-tract

Excretion

Activity in foodstuffs as function oftime after an accident

Which factors are determining
activity in foods ?

Radiologicalcharacterization

Environmental
characterization

Radionuclides deposited
Deposition per unit area
Dry deposition or deposition with rain

Ability of soils to sorb/fix caesium
Agricultural practice (e.g. use of fertilizer)
Season of the deposition

Relevant food products• Plant foodstuffs− Cereals, tubers, vegetables, fruit• Feedstuffs− Pasture grass, cereals• Animal foodstuffs− Milk, beef, pork, chicken, eggs

• Food processing and culinary preparation−Milk => butter, milk => cheese−Cereals => flour−Cooking−Rinsing

Model processes and parameters• Key processes following direct deposition on the leaves (1st year)− Dry deposition of radionuclides to soil and vegetation− Interception of wet deposited radionuclides by vegetation− Weathering loss from vegetation− Transport of radionuclides in plants to the edible parts• Key processes following deposition on soil (following years)− Uptake of radionuclides by plants from soil
− Migration and fixation of radionuclides in soil
− Intake of radionuclides by domestic animals− Transfer of radionuclides to meat, milk and eggs
− Modification of activity in foods during processing and culinary
preparation.

Contamination routes for plant products
A Short-term
1 Direct deposition onto edible

parts of plants
2 Deposition onto leaves-> transport to the edible parts

B Long-term

3 Deposition on soil and uptake
through the roots
4 Resuspension of dust and redeposition on leaves and fruits

Direct deposition on the plant
Dry deposition

Interception• Radionuclides are removed fromthe atmosphere without involving
precipitation• Radionuclides in rainwater that do notreach the soil, but instead intercepted by
the leaves, branches of plants

Dry deposition depends onInterception depends on• Plant's development (leaf areaindex)• Chemical-physical form of
the radionuclide− Particles size
− Reactive gases• Elemental iodine• Sulphur dioxide• Meteorological conditions− Wet or dry surfaces• Plant's development(leaf area index)• Radionuclide and its chemical form
• Amount of precipitation

Dry deposition
Deposition =Time-integrated activity in air * deposition
velocity
Deposition velocity vg [m/s] =Activity deposited on the ground [Bq/m²]/
Time-integrated activity in air [Bq s/m³]− vg is determined in experiments
Deposition velocities− Particles• 1 µm• 10 µm− Reactive gases (I2, SO2):− Inert gases (CH3-I)≈ 0.001 m/s≈ 0.01 m/s≈ 0.01 m/s≈ 0.0001 m/s

Interceptionof wetdepositedradionuclides
by plants• An important process for contamination ofplants− Rainfall effectively removes radionuclides
from the atmosphere− => Rainfall during the passage of aradioactive plume will increase the total
deposition to the ground• Radioactivity deposited on the leaves are
effectively taken up• Radioactivity deposited on soil
− Readily sorbed to soil

• => Low uptake by plants− => Only relevant for long-lived radionuclides(T1/2 > 1 year)− => Loss of radionuclides to deeper soil layers

Interception fraction

Dependence of interception fraction on
amount of rainfall (Kinnersley et al., 1997)
0,4
Interception fraction decreases
with the amount of rainfall

0,3
0,2
0,1
0
0

5

10

Rainfall (mm)15Dependence of interception fraction on leaf areaindex (Hoffman et al. 1995)

Interception fraction

0.7

Interception fraction increases
with leaf area index

0.6
0.5
0.4
0.3
0.2
0.1
0.0
0

1

2

3

4

5

Leaf area index

67Interception depends on the chemical form (Hoffman
Mean of 5 plant species, 8.6 mm rain

2
1,5
1
0,5

cations

I-131

S-35

Ce-141

Sr-85

Cr-51

Be-7

0

Cd-109Mass interception fraction (m²/kg)

et al., 1995)

anions(mass interception fraction = interception fraction normalized to the biomass)

Seasonality of growth:
Development of
wheatContinuous change of plantmorphology during thegrowing period

Development of leaf area and biomass• Parallel developmentin the first stage of
growth• During maturing,biomass continues toincrease, whereas
leaf area declinesMÜLLER, H. PRÖHL, G., ECOSYS 87: A dynamic model for assessing radiologicalconsequences of nuclear accidents, Health Phys. 64 (1993) 232-252.

109Leaf area index

8
7
6
5
4
3
2

harvestsowing

1
0
0

50

100

150

200

250

300

350

Day of the year

Stylized developmentof leaf area index of
winter wheat• Slow development at the beginning of growth• Rapid growth in spring when temperatures increaseRainfall and interception
Fraction of activity retained by crops(interception) …
− … decreases with amount of rainfall− … increases with the development ofcrops− … highest during the peak season
Interception for Cs
1,000
0,900

Interception factor

Increase of deposition with increasing
rainfall (intensity)

0,800

Leaf
area
index

0,700

1
1,5

0,600

2
2,5

0,500

3

0,400

4

0,300

7

5

0,200
0,100
0,000
0,1

1

10
Rainfall (mm)100

Translocation

Active transport of elements in plants− Defines the amount of activity
transported from leaves to edible parts
Depends on− Element• Mobile elements (xylem + phloem)• Immobile elements (only phloem)− Stage of development• Pronounced seasonality• Foliar uptake may exceed root uptake byorders of magnitude

Mobile elements• Systemic transport in plants from theleaves to other plants organs and viceversa
− Transport in the phloem− Maximum of contamination of theedible part is some weeks before
harvest− Then, the physiological activity is high,which is the driving force for thetransport• Examples for mobile elements− Cs, K, Na, S, P, Cl, I, Mn, Zn

Immobile elements• No systemic transport from theleaves to the roots− Only transport in the xylem− Only external contamination ofedible parts• no translocation to potato
tubers• no contamination of grain
before the emergence of ears
• Examples for immobile elements− Sr, Ba, Ra, Ce, Pb, lanthanides,
actinides

Translocation factors for wheat and barley

Left: Total activity in grain [Bq/m2] per Total activity deposited on the plant [Bq/m2]
Right: Activity concentration in grain [Bq/kg] per Total activity deposited on the plant [Bq/m2]
Voigt, G, Proehl, G, and Mueller, H. Experiments on the seasonality of the cesium translocation in cereals, potatoes and vegetables. 1991.
Web. doi:10.1007/BF01210514

Calculation of foliar uptake

Activity in edible part of the plant =(𝐃𝐃𝐃𝐃𝐃𝐃 𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝𝐝 + 𝐖𝐖𝐖𝐖𝐖𝐖 𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃𝐃 ∗ 𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈𝐈 𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟) ∗ 𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓𝐓 𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟𝐟
𝐘𝐘𝐘𝐘𝐘𝐘𝐘𝐘𝐘𝐘

Example to calculate foliar uptake of Cs-137 by wheat
following wet and dry deposition
Dry deposition: 1000 Bq/m2 Cs-137• Translocation: Fraction of caesium which is transported from the leaves to the grain(@ 4-8 weeks before harvest): ~ 0.1• Activity(wheat) =𝑩𝑩𝑩𝑩

𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝒎𝒎𝟐𝟐∗ 𝟎𝟎.𝟏𝟏
𝟎𝟎.𝟓𝟓 𝒌𝒌𝒌𝒌/𝒎𝒎𝟐𝟐= 200 Bq/kg (dry deposition)

Wet deposition: 1000 Bq/m2 Cs-137• Interception: Fraction of activity deposited which is retained by the plant~ 0.1 for a rainfall of 10 mm (equivalent to 10%)• Translocation: 0.1• Yield: 0.5 kg/m2• Activity(wheat) =𝑩𝑩𝑩𝑩

𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏 𝒎𝒎𝟐𝟐 ∗ 𝟎𝟎.𝟏𝟏 ∗ 𝟎𝟎.𝟏𝟏
𝟎𝟎.𝟓𝟓 𝒌𝒌𝒌𝒌/𝒎𝒎𝟐𝟐= 20 Bq/kg (wet deposition @10 mm rain

Loss ofradionuclides
from plants due
to weathering• Post-deposition activity loss from plants− Rainfall, fog, foliar abrasion− Including the decrease of activity concentration
due to increase in biomass (growth dilution)• Influencing factors− Time after deposition• Loss rate declines with time after deposition− Age of plants• Higher for young plants− Rainfall, fog• Quantified by a weathering half-life− 14 days represents a reasonable value• γ-dose rate drops
from 26 → 6.5 µSv/hfrom 20 March → 1 June
• The decline of I-131 isfaster due to the shorter
half-life• The Cs-137 in the end of
the of the observation
period is due to uptake of
Cs-137 from soil

Cs-137 and I-131 activity in weed (leafy
vegetables) at 36 km NW from FDNPPWeathering half-lives (days) of selected elements andfor generic plant types

Radionuclide
uptakefrom soil

Long-term source of plantcontamination, depending on• Soil characteristics− Sorption capacity (Sand, loam and clay
content, Organic matter)− pH value− Redox potential (esp. iodine, plutonium)− Concentration of antagonists• Cs vs K, Sr vs Ca• Use of fertilizer• Depth of the roots• Chemical form of the deposit− Soluble vs inert particles• Time since the contamination− Progressing sorption, fixation andincorporation processes

Quantificationof the uptakeof radionuclides
from soil• Transfer factor soil-plant TF
TF= Activity in plant/Activity in soil
[Bq/kg fresh per Bq/kg dry]
• Aggregated transfer factor Tag
Tag =Activity in plant/Deposition to soil
[Bq/kg fresh per Bq/m²]= [m²/kg]
Tag is used when it is difficult to determine theaverage activity concentration in soil
− In forests− On natural land

Typical valuesfortransfer factors
soil-plant• Strontium:−0.1 - 1• Caesium−Well managed soils: 0.001 – 0.1−Organic, acid soils: 0.1-10• Technetium:− 0.1 – 10
• Iodine:− 0.001 - 1• Plutonium, americium :−0.00001 – 0.001• Pronounced variability, also on the samesiteTransferfactorssoil-plant• Advantages− Easy determination− Easy application in models• Disadvantage− Lumped parameter including all processes• Chemical forms of the contaminant• Soil properties are not considered− Large data bases are required to ensure
reasonable assessment

Estimation of root uptake of caesium
Root uptake:• Deposition:
10000 Bq/m2• Ploughing depth: 0.25 m• Soil density:
1400 kg/m3• =>𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷
10000 𝐵𝐵𝐵𝐵/𝑚𝑚2
Activity(soil) ==≈ 30 Bq/kg
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑∗𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 0.25 𝑚𝑚 ∗1400 𝑘𝑘𝑘𝑘/𝑚𝑚3• Transfer factor soil plant (TFsp): 0.01 Bq/kg plant per Bq/kg soil

• => Activity(plant) = Activity(soil) * TFsp = 30 Bq/kg * 0.01 Bq/kg plant p. Bq/kg soil ≈ 0.3 Bq/kg

Contamination
route

Dry
Deposition(1000 Bq/m2)

Wet deposition(1000 Bq/m2)
5 mm
rain

10 mm
rain

Root uptake

0.3

0.3

0,3

Foliar uptake

200

40

20

Comparison of foliar androot uptake of Cs-137• Radionuclides deposited on foliage are usuallyeffectively taken up• The activity levels in the edible part can be orders ofmagnitude higher than due to root uptake• For long-lived radionuclides, root uptake represents
a long-term source for the contamination of crops

Resuspensionof soil• Defines the flux of radionuclides
from soil to atmosphere• Depends on− Soil texture and humidity− Vegetation cover− Wind speed• Areas particularly affected byresuspension− Arid regions− In temperate climates,
resuspension during storms
may cause a relevant activity
loss from soil

Importance of resuspension• Resuspended soil may be redeposited on crops− Resulting contamination of plants is low− Contributes to the overall plant contamination only if root uptake is low• Factors causing higher resuspension− Important for canopies with low soil coverage− Primarily important for small soil particles (clay, silt, very fine sand)− Radionuclides may be enriched in the resuspendable fraction• Enrichment of caesium in fine soil fractions by a factor of 3

• Quantification as kg soil per kg plant− Same dimension as Transfer factor soil-plant− For temperate climates: 0.01-1 g soil per kg plant

Transfer toanimalproducts• Use of contaminated feedstuffs• Transfer to meat, milk, eggs

Simple model for the transfer to animal
products
Activity intake:Feedstuffs, inhalation

Metabolic model

Activity in meat, milk, eggs

AnimalFeedstuff

Intake rate (kg/d)

Cow

Grass/hay≈ 14

Sheep (lactating)

Grass/hay≈ 1.8

Grass/hay, maize

≈ 10

Pig

Cereals≈3

Lamb

Grass/hay≈1Hen, chicken

Cereals≈ 0.1

Beet (meat)

Feed intake ofdomestic animals• Feed intake is very variable• Type of feedstuffs used depends on theavailability of feedstuffs• The dry matter intake depends on milk yield,
age, growth of the animal, etc.

Simple model for the time-dependence of theactivity in animal products
Quantification• Transfer factor (steady state
conditions)• Biological half-lives

Transfer factors feed-animal products• Definition
TF feed-(meat/milk/eggs) [d/kg]== Activity(meat/milk/eggs) [Bq/kg] / Daily activity(animal) [Bq/d]− TF is defined for equilibrium conditions• Dependent on− Element− Chemical form
− Feeding diet, feeding status• Data base

− Acceptable data base for I, Sr, Cs to milk
− Poor data for most other elements/products− Dynamic needs improvement− Impact of stable elements, especially iodine is unclear

Typical values
for transfer
factors
feed-animal
products

Element

Milk
(d/L)

Beef
(d/kg)

Pork(d/kg)

Caesium

0.003

0.04

0.4

Strontium

0.001

0.0003

0.002

Iodine

0.003

0.001

0.003

Plutonium

5E-5

5E-5

3E-4

Biological half-lives for animal products
Element

Product

Fraction 1stcomponent

Half-life 1stcomponent

Fraction 2ndcomponent

Half-life 2ndcomponent

Caesium

Milk
Beef
Pork
Lamb, chicken
Eggs

0.8
1
1
1
1

1.5
50
35
20
3

0.3
-

15
-

IodineMilk, eggs
Meat, chicken

1
1

0.7
100

-

-

Plutonium

Milk, meat
Chicken, eggs

1
1

Years
25

-

-

Strontium

Milk
Meat
Chicken
Eggs

0.9
0.2
0.5
0.5

3
10
3
2

0.1
0.8
0.5
0.5

100
10
100
20

Model Description of the Terrestrial Food Chain and Dose Module FDMT in RODOS PV6.0 RODOS(RA3)-TN(03)06

https://resy5.iket.kit.edu/RODOS/Documents/Public/HandbookV6/Volume3/FDM_Terra.pdf

Seasonality of Cs-137 in milk following theChernobyl fallout in spring 1986
(UNSCEAR 2008, dairy farm near Munich, Germany)
Weathering loss
Growth dilution
Half-life: 14 days

Transition from winter tosummer feeding

Feeding of hay
prepared inspring/summer

30 April 1986

Food processing
and culinary
preparation• Crops can be directly ingested• Leafy vegetables:• Fruit vegetables (tomato, cucumber, etc.)• Fruit (peach, apples, pear, plum, etc.)• Products may be processed• Cereals -> bread• Milk -> butter, cheese• Quantification• Procession factor Fr• Fr = Activity(processed product)/Activity(raw product)

Processing factors for cereals, vegetables and milk
Raw product

Processed
product

Processing factor
Activity processed prod/Activity raw product
Strontium

Caesium

Iodine

Wheat

Flour
Bran

0.5
3.0

0.5
3.0

0.5
3.0

Rye

Flour
Bran

0.5
3.5

0.6
2.7

0.5
3.0

Spring barley

Beer

0.04

0.1

0.1

Potatoes

Peeled potatoes

0.8

0.8

0.8

Vegetables

Washing. removalof outer leaves

0.8

0.8

0.8

Milk

ButterCreamCheeseCheese

0.2
0.4
6.0
0.8

0.2
0.7
0.6
0.6

0.5
0.7
0.6
1.4

Model Description of the Terrestrial Food Chain and Dose Module FDMT in RODOS PV6.0 RODOS(RA3)-TN(03)06

https://resy5.iket.kit.edu/RODOS/Documents/Public/HandbookV6/Volume3/FDM_Terra.pdf

Processing factors for rice
Processing factor

Raw product

Processing

Brown rice

Milling to white rice

0.46±0.03

Washing0.96±0.03

White rice

Washing

0.58

Brown rice

Boiling rice after milling towhite rice and washing

0.13±0.01

White rice

Boiling rice after washing

0.27±0.02

Boiling rice noodle

0.33±0.07

Processing factor = Activity in processed product/Activity in raw productTagami et al., 2019For more
information:

Compilation ofparameters forenvironmental
transfer

Intake of radionuclides withfoodstuffs

Internal dose fromingestion:
Intake of activity
with all foodstuffs
considered− Ah(t) = human activity intake (Bq/d)−k= number of foodstuffs considered− Ck (t) = activity conc. of foodstuff k (Bq/kg)− Vk (t) = consumption rate (kg/d) of foodstuff kLifestyleWhichfactors are
determining
the intake ofradionuclides
with food• National, regional and individual
habits• Do people produce their own
food ?
• If yes, to which extent?

Origin of food
• Where does the food come from?
• From the region?
• From the own country?
• From global suppliers?

Factors determining the food intake after an accident
National
habitsAge,genderInformation on
food
contamination

Remediation

Food bans??
Intake of food bypeople??

Reaction of foodproducingcompanies

Regional
habitsIndividual
habitsUrban –rural
population

Level ofanxieties

Default food consumption (IAEA, 2001)

IAEA, Report SRS-19, 2001

Another example:
Age-dependent German consumption rates Vk as applied as default in FDMT

Result: time-dependent activity in foodstuffs
ECOSYS: Activity in foodstuffs
after deposition on 1st May

Activity in foodstuffs (Bq/kg)

1,0E+3leafy veget.
milk
pork
potatoes

1,0E+2

1,0E+1

1,0E+01,0E-1

1,0E-2
01. Apr02. Jul

02. Okt

02. Jan

04. AprTime

05. Jul05. Okt

Predicted doses via different exposure pathways following
the Chernobyl deposition (Southern Bavaria, Germany)

Integrated dose: contributions of exposure pathways

1,4E+00
1,2E+00

Dose in mSv

1,0E+00
8,0E-01
6,0E-01
4,0E-01

Total
Ingestion
Inhalation

2,0E-01

Cloud• No mitigating
actions

1day

1 weekSkin/clothes

2 weeks

1 month

6 months

1 year

2 years

Ground5 years

10 years

50 years• Intake of locally
produced food

70 years0Testing the model: Cs-137 whole body counting(near Munich)ECOSYS Model
Males BfS
Females BfS
Males GSF
Females GSF
Maximum
MinimumMüller, H, and Pröhl, G., The radioecological Model ECOSYS: Concept and Applications, Proc. Intern. Workshop on
Improvement of Environmental Transfer Models and Parameters, Tokyo, Japan, 5-6 February, 1996

• Input data

Improving
confidence inmodel results− Uncertainty increases with number ofsteps between input and endpoint− Prefer input data ‘closest’ to theendpoint• In-vivo measurements: Whole body,thyroid• Individual dosimeters− Temporal and spatial resolution in ofmonitoring data

• Model analysis− Comparison with real data
− Identification of sensitive assumption
and parameters− Systematic uncertainty analysis

Monitoring and models

Monitoring

Models• Providing measures results• Validate and calibrate models• But: How representative are measurements?
Do they always tell the “truth”?

• Understand measurements• Interpolation in time and space• Extrapolation to the future• Overcome data gaps

68

Decline of 137Cs-levels in food and waterFirst few weeks
Fast processes of sorption,
vertical migration, biologicaluptakeMore than 4-7 years
Slow desorption, vertical migration,
erosionUp to 4-7 years“Fixation”

Fish, UK Bq/kg

137

Cs activity concentration

Fish, Norway Bq/kg
Vegetation Bq/kg

10000

Water mBq/l

1000
100
10
1
1986

1990

1994

1998

The decline is much
faster than due to theradioactive decay only

Date
Smith, J.T. et al. (2000) Chernobyl’s legacy in food and water. Nature, 405.

Ecological half-life: 10.5 years
Effective half-life (including decay): 7.8 years

137Cs in wild boar collected in South Germany (1986 to 1999)

Time-dependence of 137Cs-TFs for brown and white rice in Japan
S. Fesenko, N. Sanzharova, K. Tagami: Evolution of plant contamination with time (IAEA-TECDOC 1616), 2009)

Plants and animal food products on
agricultural land
– 4 to 6 years

Summary of
ecologicalhalf-lives for
Cs

Pasture– In the first 5-6 a after deposition:
1 - 4 years– Afterwards: 5 - 15 years– Slower decline for vegetation on peat
and mineral soils low in clay minerals.
Forest products (Roe deer, deer, wild boar,
forest plants, berries, fungi (Middle Europe))– Average: 12 years– In some areas much longer