A COMPARISON OF REMEDIATION AFTER THE
CHERNOBYL AND FUKUSHIMA DAIICHI ACCIDENTS
B.J Howard
S. Fesenko

M. Balonov
G. Pröhl

S. Nakayama
For the first five years after both accidents(but not the emergency phase)

The accidents: Chernobyl USSR, 1986
• Unit 4• Atmospheric release (PBq)– 131I - 1760; 134Cs ~ 47, 137Cs ~ 85; 90Sr – 10

• Release pattern– Initial release with the thermal elevation;
10-day variable releases due to fire
• Atmospheric conditions– Variable wind direction; Complex multidirectional land deposition (dry and wet)

The accidents: Fukushima Daiichi, Japan, 2011
• Several Units• Atmospheric release (PBq)– 131I - 160; 134Cs and 137Cs ~12-16• Release pattern– Several initial releases due to venting
and hydrogen explosions;– Weeks of releases• Atmospheric conditions– Variable wind direction; Dispersion
toward the ocean (east) and only small
fraction was to land;– Dry and wet deposition (incl. snow);
Land deposition prevails in the northwest directionComparison of ground deposition 134Cs & 137Cs
Accident

Deposition to terrestrial and freshwater systems andaffected areas
137Cs
134Cs
Total deposition
to terrestrial andfreshwater
systems(PBq)

Area withdeposition> 100
kBq/m2(km2)

Total deposition
to terrestrial andfreshwater
systems(PBq)

Area withdeposition> 100
kBq/m2(km2)

Chernobyl

64 (Europe)

56000

35 (Europe)~30000Fukushima
Daiichi
Chernobyl/Fukushima
Daiichi

2-3 (Japan)~3000

2-3 (Japan)~3000~20~10

IAEA 2006 Chernobyl forum; Morino 2011 Geophys. Res. Lett. 38; Yasunari 2011 PNAS 108

The key affected areas

Comparison of the contaminated areas
FactorTimingPopulationintensity

Chernobyl
At start of growing season
Moderate, no pressure touse land
Flat, forested andagricultural

Fukushima Daiichi
Before growing season
High, pressure on available
land
Mountainous: forested slopes
and coastal catchments

Intensity ofagriculture

Low - medium

HighKey products

Milk, meat, grain, potatoes

Rice, fruit, leafy and root
crops, grain, flowers

Terrain

Lateral movement
Low
across landscapePotentially highChange in external dose with time
Gamma dose rates
continue to decline due tothe natural processes ofradioactive decay,
weathering and migrationFractional reduction in effective
external dose rate since 2012

1.2
1.0
0.8
0.6
0.4
0.20.02012

2013

2014

2015

Year
IAEA Fukushima Report - Technical volume 5/5 p 21

Comparison of internal exposure pathways

FactorChernobyl

Fraction of soils with highModerate to HighOM content
Very low to moderate
K fertiliser usage

Radiocaesium availability
Moderate to very highfor root uptake
Transfer to animal
products
Intake of local foodIntake of wild food

Fukushima Daiichi

LowHigh
Very low to moderate

Moderate to HighLow

High to very highModerate to very highLow
Low to moderateComparison of site specific contribution to dose2012

Contributions of ingestion for both Chernobyl and
Fukushima vary widely, in particular for Chernobyl
Fukushima data for Kawauchi Village, Fukushima Prefecture [Taira et al., 2014] .
Chernobyl: Average data for selected rural settlements affected by the Chernobyl
accident [Jacob et al., 2001]

Affected landscapes – focus of remediation
Chernobyl

Fukushima Daiichi

Collective and private farming,
agriculture, forests, uplands

Decision to remediateevacuated areas

Importance ofrice production
in paddy fields

Forestedcatchmentswith steepslopes

Goals of recovery
Reduction of dose - long term goal <1mSv/y at both sites
To enable residents of contaminated areas to return to anormal life
CHERNOBYL• Some hundred of thousands of people were living inareas with > 1 mSv/y• Need to remediate to reduce their effective dose rate
• Secondary concern to return people to evacuated areas

FUKUSHIMA DAIICHI• To re-establish an acceptable basis for a
fully functioning society in all affected areas• Revitalisation of all contaminated areas

Food standard limits – Chernobyl and Fukushima
Food Standard Limits Bq/kg fw
Chernobyl
Fukushima
Date
implemented
Estimated annual
effective dose(mSv)

30.05.1986

15.12.1987

22.01.1991

17.03.2011©

1.04.2012<50<8<5<5

<1500

100

Food category
General food
Meat and meatproducts
Eggs
Fish
Vegetables
BreadDairy products
Cattle milk/infant
foodMilk
Drinking water3700

1850-3000

740

37000
3700

1850
1850
740
370
370-1850

740
740
600
370
370-1850

370
370-18500

50
370-3700

370

370

200
200

10Remediation Action Levels• Specific actions applied to reduce environmental
contamination and radiation doses to peopleguided by derived ‘remediation action levels’.
• Radiological criteria– Dose cannot be easily measured, so “operationaleasily measurable quantities” are derived– ambient gamma dose rates (μSv/h)– deposited activity per unit area (Bq/m2)• Derived using models and assumptions aboutliving habits and about environmental behaviourof radionuclides.

Comparison of radiological criteria
FactorChernobyl

Fukushima Daiichi
Similarities
Long term goal of effective annual dose
1 mSv
Differences

Temporary permissiblelevels for effective
annual dose

1986 – 100mSv
1987 – 30 mSv
1988- 1989 – 25 mSv
1991- 1mSv

March 2011 – 5 mSv
Sep 2011 - 1 mSv

Ambient dose rate
µSv/h

2.2
corresponding to lifetime
additional dose of 350 mSv(applied in 1989)

0.19 (excl. naturalbackground)corresponding to annual
additional dose of 1 mSv

Changes with time infood standard limits

Down in CIS countries,
stable in EU countries

Down (decreasing)

0.19 µSv/h is about 50 kBq m-2 of 137Cs and about 20 kBq m-2 134Cs

Chernobyl designation of remediation areas
137Cs kBq/m2

DesignationBelow 37

Not contaminated37 - 185

Remediation for areas
with “sensitive soils”(eg. wet peat, acidsandy)

185 - 555

Remediation applied
for sandy soils andlight loam soils

555 - 1480

Full scale remediation>1480

No economic activity

Set definition of contaminated land at 37kBq/m2
Identified settlements where annual dose rate was > 1 mSv.
Izrael 1990

Fukushima designation of remediation areas
Special Decontamination Area (SDA)(Evacuated areas)

Intensive Contamination Survey Area(ICSA) (Not evacuated areas)

Coloured areas
were remediatedSDA 1 (Green) : additional exposure rate lower than 20 mSv/year (Evacuation orders
are ready to be lifted)
SDA 2 (Yellow): additional exposure rate between 20-50 mSv/year (Residents are notpermitted to live)
SDA 3 (Red): additional exposure rate higher than 50 mSv/year (Residents havedifficulties in returning for a long time)
ICSA: additional exposure rate higher than 1 mSv/yearComparison of remediation approach
AspectChernobyl

Fukushima Daiichi

Similarities
Restrictions and food monitoring
RadiologicalCriteria

Key focus
Remediated areas

Food standards, [RCs] soil, ambient dose rate
Decontamination of residential areas
Differences
External and internal dose
External dose
All settlements with average
individual dose > 1 mSv/yApproach

Risk based - averted dose,
optimisation taking accountof cost-benefit

CostForest

High
Optimisation, advice

ICSA and evacuated areas - SDA
1,2,3
Rapid implementation,
optimisation, social and cultural
influence, sufficient financial
resources available,high priority on dose reduction- even in less affected areas
Very highBorder decontaminationDecontamination Of Residential Areas
Removal of topsoil (5 cm) and surface deposits from houses,
gardens, roads

Chernobyl

Fukushima Daiichi

Dose rate map of a settlement before and after
decontamination (nSv/h)

Effectiveness of reduction of the external ambient dose rate :• 5-10 fold for early removal of surface deposits.
• 2-4 fold reduction thereafterRemedial measures applied - residential
Remediation measure
Decontamination of residential areas
High pressure water hosing
Removal of deposits from the roof,
gutters etc.
Wiping roofs and walls
Vacuum sanding
Topsoil removal
Removal of plants
Removal of deposits in road ditches
Decontamination of gardens/trees
Topsoil removal
Paring fruit trees
High pressure water hosing
MowingRemoving leaves

Chernobyl Fukushima
Daiichi
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Fukushima: environmental remediation
Farmland Pilot Projects• Removal of 4 cm of topsoil (4cm)• Removal of topsoil using soil hardener(2 cm)• Removal of grass and upper root-top
soil layer (3 cm) (for meadows).
• Deep ploughing• Draining suspended soil from paddies
Testing top soil removal after using soil hardener(Courtesy from MAFF-JAEA-NARO)

Comparison of agriculture remediation measures
Remediation measure

ChernobylFukushimaDaiichi

Remediation for animal products
Clean feeding
AFCF to animals
Live monitoring of domestic animals
Remediation of agricultural land
Radical improvement – ploughing, reseeding,additional fertilisation
Soil removal
Tillage reversal
Soil treatment with additional K and P
Soil amendment with liming
Application of sorbents and organic fertilisers
Drainage of wet peats
Paddy fields puddling and removal of suspended
sediment
Removal of plants
Soil hardening and removal

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Agricultural remediation - developments
ChernobylFukushima Daiichi• Clean feeding• Removal of plants, topsoil• Biological half lives• Live monitoring• Cs binders• Radical improvement• soil hardener• Draining suspended soil frompaddies• Deep ploughing• Treatment with extra K

Remediation of farmland - Fukushima
APPLICABILITY OF REMEDIATION MEASURES FOR FARMLAND (MAFF 2014)
Remediation measure

Enhanced use of K-fertilizer toreduce Cs-134/137 uptake
Reversal tillage to bury Cs13/137 (fields, rice paddies,grassland)
Soil suspension in water andremoval with extracted water(rice paddies)

Top soil removal (fields, ricepaddies, grassland)
Using an agent to solidify thesoil to allow removal ofradiocaesium from surface soil
Weed / Grass /pasture removalRadiocaesium activity concentration in soil (Bq/kg)< 50005000-10000 10000-25000>25000Forest remediation• Restrictions on– access, harvesting of food products, collection of firewood

Chernobyl- Optimisation approach• Local monitoring
Fukushima Daiichi• Remove surface material from 20 mborder
Site specific settlement information on:• Action level for use of wood for• Spatial variation in contamination
mushroom production• Which mushroom species to avoid• Where and when to collect wood, wild • Decision not to implement additional
measuresproducts and hunt game animals• Tree felling schedules

Waste generation and management
Chernobyl• Decontamination of ca. 1000 settlements andwaste buried nearby• Selection of remediation options which did notgenerate waste

Fukushima• Decontaminating ICSA and SDA• Huge generation of waste• High costs

Conclusions• For both accidents, the long term goal of remediation is anindividual additional annual effective dose of 1 mSv.
• The radiological consequences of the Fukushima Daiichi accident
for the public is much lower than that of Chernobyl, but the scaleof remediation activities is comparable– Radiological criteria for remediation applied in Japan are lower
than those applied in the USSR, and have therefore had
relatively higher associated costs– adoption of lower standard limits for food and otherremediation action levels in Japan– decision to remediate evacuated land in Japan• After Chernobyl weighting of averted dose versus remediation
costs was an important part of the remediation strategy. In Japan
remediation of affected districts was justified and implemented
based on radiological and/or social and cultural considerations.