specificity of decontamination and remediation · pdf filespecificity of decontamination and...

IAEAInternational Atomic Energy Agency

Specificity of decontamination and remediation

activities after accident

Sergey Mikheykin

D-R PMU, Kozloduy NPP site

[email protected]

Workshop on development of specific decontamination techniques for RBMK dismantlement and/or highly active material from contaminated areas from accident conditions,

Visaginas, Lithuania, 24-28.08.2015

IAEA

Definition

Any unintended event, including operating

errors, equipment failures

and other mishaps, the consequences or

potential consequences of which are

not negligible from the point of view of

protection or safety.

[IAEA SAFETY GLOSSARY. TERMINOLOGY USED IN NUCLEAR SAFETY

AND RADIATION PROTECTION. 2007 EDITION]

2IAEA Workshop, Visaginas, Lithuania on August 20-24, 2015

IAEA

Accidents/INES

3

Off Site Impact

On Site Impact

IAEA

Waste after accidents

4

The main differences in waste management system in normal

operation and after accident are wide spectrum of wastes

(liquid, solid: soil, concrete, metals, debris, vegetation etc) and

large volume of radioactive wastes. For severe accident and

cleanup, waste volumes are expressed in tens thousands or

even millions of m3.

Special RWM strategies needed to address accident and

cleanup waste due to the very large volumes, range of

activities, timeframe, etc.

IAEA Workshop, Visaginas, Lithuania on August 20-24, 2015

IAEA

EXAMPLES

5

Major accident

(INES Level 7):

Chernobyl

NPP,

Ukraine

1986 The releases from Unit 4 continued for 10 days, and included

radioactive gases, condensed aerosols and a large

amount of fuel particles. Area of more than 200 000 km2

Major accident

(INES Level 7):

Fukushima

Daiichi NPP,

Japan

2011 Tepco estimates published in May 2012 showed a total of about

1020 PBq released to the atmosphere over 12-31 March 2011

(after which very little was released). Apart from noble gases this

comprised 500 PBq iodine-131, 10 PBq Cs-137 and 10 PBq Cs-

134. In iodine-131 equivalent terms this comes to 500 + 400 + 40 =

940 PBq Iodine-131 released to atmosphere

Serious

accident (INES

Level 6)

Mayak

Reprocessing

plant

Kyshtym

USSR

1957 Some 15 000–20 000 km2 received contamination higher than 3.7

kBq/m2 of Sr-90. This delineated an area of approximately 1000

km2 that became known as the East Urals Radioactive Trace.

Accident with

wider

consequences

(INES Level 5):

Three Mile

Island TMI-2,

USA

1979 Approximately 2500 m3 of water with an activity of 1 TBq/m3 were

released into the auxiliary building, fuel handling building, service

building and diesel generator building.

Experiences and Lessons Learned Worldwide in the Cleanup and

Decommissioning of Nuclear Facilities in the Aftermath of Accidents,

IAEA Nuclear Energy Series, No. NW-T-2.7

IAEA

EXAMPLES

6

Accident with

local

consequences

(INES Level

4):

A-1 Jaslovské

Bohunice,

Slovakia

1977 Fuel integrity was lost as a result of two fuel loading events

resulting in extensive damage of fuel cladding and release of

radioactivity.

Serious

incident (INES

Level 3)

THORP

Reprocessing

Plant

Sellafield Ltd,

UK

2006 Following plant mass balance calculations, a pool of 83 m3 of

product liquor was discovered within the feed clarification cell of the

THORP reprocessing plant. No liquor was lost to the environment

and no persons were injured or contaminated following this event.

Incident (INES

Level 2)

Atucha NPP

Argentina

2005 Overexposure of a worker at a power reactor exceeding the annual

limit.

Anomaly

(INES Level

1):

(Reactor)

Mihama NPP

Japan

2004 A water pipe in a turbine building adjoining the Mihama 3 reactor

burst suddenly as workers prepared to conduct a routine safety

inspection. Though no radiation was released, the steam explosion

killed five plant workers and injured others.

Experiences and Lessons Learned Worldwide in the Cleanup and

Decommissioning of Nuclear Facilities in the Aftermath of Accidents,

IAEA Nuclear Energy Series, No. NW-T-2.7

IAEA

The principle events

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Event Plant Date Current Status

Windscale 1957 Care and Maintenance / Safe Enclosure

TMI -2 1979 Care and Maintenance / Safe Enclosure

Chernobyl 1986 Post Accident Clean up / Safe Enclosure

Fukushima 2011 Emergency Response / Stabilisation

Kyshtym 1957 Site Remediation

A1 Safe Enclosure / Decommissioning


IAEA

Differences

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## D&D Emergency

1 Facility is under regulation control within all

operation time

Lost control as result of accident

2 Records keeping, good knowledge about site No records, lack of information about present

status of contamination and infrastructure

3 Control to constructive materials, process and main

equipment

No control, partially demolished constructions and

shields

4 Operations in according with licensed

decontamination plan

Needs in quick responds, possibilities for untypical

solutions

5 Need development of Decontamination plan at 1-5

years before shutdown of facility

Decontamination plan developing AFTER accident

6 Standard management approaches Emergency management under pressing of time,

irradiation and “unknowns”, many “surprises”

7 Strong regulation control, strong implementation of

safety standards for operations

Possibility to change of safety limits

8 Work of professional teams (selected as result of

competition/tender process)

Needs in well - skilled personnel (radiophobia)

9 D&D activity should provide the owner of the

Facility

Owner may have no resources, needs in the

Governmental or International support


IAEA

Role

• Decontamination and remediation starting with the start

of post-accidental works. The role of these actions are

reduction of risk for personnel from

irradiation/inhalation and protection of environment

from the distribution of radioactive substances with

natural factors as wind and water streams (rain, snow

melting, groundwater streams).

• Decommissioning and site remediation after accident

are under strong pressure of irradiation, absence of full

information about present status of accidental site, time

pressure, absence of well skilled decontamination team

etc.

IAEA Workshop, Visaginas, Lithuania on August 20-24, 2015 9

IAEA

Phases of planning of post-accident

cleanup projects .

10

Post-Accident Cleanup Activities

Planning Phases for INES Scale 1-4 Planning Phases for INES Scale 5-7

Stabilize

Post-

Accident

Cleanup

Restore/

OperateCompletion Stabilize

Post-Accident Cleanup

Early Final After

Reactor control/Source Control X X

Decay heat removal NA X

Gain access & information for

stabilization

X X

Characterization O X O X X X

Facility condition assessment X O X

Fuel/Source condition

assessment

X X X

Enclosure Structures (large) NA X

Water storage If applies X O O

Gas and air processing and

release

If applies X

Water processing If applies X X O

Decontamination for access X X

Damaged fuel/source removal X X

Damaged fuel/source storage X X

Waste shipping & disposal X O O X O O

Decontamination for operation X NA

Return to operation X NA

Waste storage If applies X ?

Decontamination for cleanup X X

Establish completion conditions X X

IAEA

List of operations

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Criteria Subjects Criteria Statements

1. Structural and

Boundary Integrity

Structural and boundary integrity will be such that: 1) inspection personnel are safe, 2) contamination or hazardous materials remaining in the facility are contained, and 3) intrusion by unauthorized personnel, as well as animals and plants, are prevented.

1. Nuclear Materials Nuclear fuel and debris will be removed to the extent practical. Residual fissile material must be reduced to a level such that criticality cannot occur.

1. Hazardous Materials Hazardous materials and chemicals will be removed in accordance with environmental regulations. Fixed in place hazardous materials remaining in the facility will be contained in limited areas or stabilized to prevent release. The amount and location of remaining hazardous materials will be documented.

1. Process Systems and

Equipment

Process systems and equipment have been abandoned in place, isolated or sealed off for safety of future personnel, or removed where there is a compelling reason to do so.

1. Service and Utility

Systems and

Equipment

Only systems required to support the monitored storage state and maintain the stable condition are operational. Other utility systems will be abandoned in place, isolated or sealed off for safety of personnel, or removed where there is a compelling reason to do so.

1. Personnel Safety Inspection personnel are safeguarded by stable conditions, postings, and written procedures that have been established in accordance with standard procedures for radiological protection and industrial safety practice.

1. Waste and Liquid

Effluents

Waste will have been removed to the extent practical. Waste may remain if removal is with extreme difficulty. The only liquids remaining are minor quantities that cannot be readily removed with installed equipment.

1. Radiation Protection Established in accordance with standard procedures. In particular, the periodic inspection path will be subjected to ALARA review. Contamination remaining in the facility will be contained in limited areas or stabilized to prevent release.

1. Housekeeping &

Miscellaneous

Materials

Valuable materials will be removed. Trash and non-contaminated furniture, loose equipment, etc. will be removed.


IAEA

Specificity of RWM

12

IAEA

Approaches

• Chernobyl – Decontamination ASAP

• Fukushima – Decontamination ASAR

• TMI-2 – Removal of the fuel debris 1985-

1990.


IAEA

Specificity of decontamination

• Much of the past decontamination experience at nuclear facilities relates to

the cleanup of buildings, equipment and paved surfaces in or adjacent to

nuclear reactors and other facilities during normal operations or

decommissioning.

• Decontamination experience ranges from the cleanup of highly active

components or buildings in reprocessing plants or in other facilities after a

serious accident, to operations on slightly contaminated equipment or

buildings being released for unrestricted use.

14

Dynamics of self-decontamination of the region of the Fukushima-1 NPP

contaminated by radioactive substances can predict that the maximum dose rate in

the region of contamination will decrease to the background level in approximately

200 years.


IAEA

Preparation works

• Characterization/monitoring

• Development of decontamination strategy

• Installation of safety barriers and ventilation

• Equipment

• Organization of waste and personnel routes

• Team creation, training


IAEA

Decontamination in Chernobyl Area

• During large-scaled decontamination campaign in 1986-

1989 about one thousand of settlements were treated, tens

of thousand inhabited and social buildings, more than

thousand of agricultural farms.

• Depending of decontamination technologies the dose rate

over different plots was decreased by a factor of 1.5 to 15.

• Actual effectiveness of the annual external dose decrease

after upper soil layer removal usually was 10 to 20% for

average population ranging from about 30% for children

visiting kindergarten and schools to less than 10% for

outdoor workers (herders, foresters, etc.).16IAEA Workshop, Visaginas, Lithuania on August 20-24, 2015

IAEA


• 1. Removal of the upper 5-20 cm layer of soil (it depends

on the activity distribution in depth) in courtyards in front of

residential buildings, around public buildings, schools and

kindergartens, from roadsides inside a settlement.

• The removed most contaminated layer of soil gets placed

into the holes specially dug on the territory of a private

homestead land or on the territory of a settlement when

decontaminating the settlement as a whole. At that the

clean soil (sand) from the dug holes gets used for covering

decontaminated areas.

• Such technology excludes the formation of special burials

of radioactive waste.


IAEA


• 2. Deep ploughing of private fruit gardens’ territories or

removal of the upper 5-10 cm layer of the soil. If vegetable

gardens have been ploughed up many times, and in this

case the activity distribution in soil will be uniform in the

layer 20-30 cm deep

• 3. Covering the decontaminated parts with a layer of

«clean sand/soil», or, where possible, with a layer of

gravel to attenuate residual radiation (see item 1).

• 4. Cleaning the roofs or their replacement (the roof

decontamination should be done before decontaminating

the under spread surface).


IAEA

Achievable Decontamination Factors

for Various Urban Surfaces.

19

http://www-ns.iaea.org/downloads/rw/projects/emras-urban-decontamination-of-

settlements-golikov.pdf


IAEA

Decontamination 1986

20

IAEA

Decontamination 1986

21

IAEA

Fukushima - Land decontamination

22

House and garden (to reduce airborne dose rate)

• Lots of radioactivity has washed out from roofs.

• Dirt in ditch, moss and weed in surrounding area

have a higher radioactivity.

Road and street (to reduce airborne dose rate)

• Lots of radioactivity has washed out from the

pavement.

• Dirt and grass on a side soil and in ditch is

effective.


IAEA

Fukushima - Land decontamination

23

Farmland (to reduce the radioactivity)

5,000 Bq/kg is the upper limit for agricultural utilization.

Soft remediation method, i.e. plowing, rotary harrowing, is applied to relatively low

contaminated area.

Strong remediation method, i.e. top soil removal, replacement by fresh soil,


IAEA

Specially designed

removal equipment

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Soil treatment

IAEA

Remediation Technology

Test ConditionReduction of Cs Concentration

[Bq/kg]

Applicable Contamination Level [Bq/kg]

Surface soil removal Removal depth = ~4cm 10,370 → 2,599DF=4.0

10,000-25,000

Chemical fixation & Surface soil removal

Fixative = Mg compoundRemoval depth = ~3cm

9,090 → 1,671DF=5.4

> 25,000

Surface soil removal with Grass & Weed

Removal depth = ~3cm 13,600 → 327DF=42

> 25,000

Harrowing & muddy water drainage

15,254 → 9,689DF=1.6

5,000-10,000

Phytoremediation Plant = Sunflower Soil = 7,715Stem=52, Root=148 -

http://www.s.affrc.go.jp/docs/press/pdf/110914-06.pdf in Japanese

Farmland contaminated more than 5,000Bq/kg = 83km2

→ 3.0million tons of waste are generated by 5cm soil removal.

Demonstration test results for Remediation Technologies by MAFF* *: Ministry of Agriculture, Forestry and Fishers

25

http://www.s.affrc.go.jp/docs/press/pdf/110914-06.pdf

IAEA

Urban decontamination

26

Decontamination of settlements is one of the main

countermeasures to be applied to reduce external exposure of

the public and clean-up workers during the initial stage of the

response to a severe nuclear emergency.

IAEA

Decontamination of Houses

27

IAEA

Waste disposal


IAEAInternational Atomic Energy Agency

Radioactive waste management

flow sheets after accidents

IAEA

Contaminated Soil

Decontamination

(optionally)

Solidification (optionally)

Packaging

Removing from surface

Reuse

Reuse

Radiometric sorting

Storage


IAEA

Concrete

Radiometric separation

Solidification (optionally)

Packaging

Decontamination

(scrabbling etc.)

Reuse

Reuse

Crushing

Storage

IAEA

Metals

Melting (optionally)

Packaging

Decontamination

Reuse

Reuse

Fragmentation

Storage

IAEA

Sediments

Solidification

Packaging

Decontamination or

purification

Reuse

Storage


IAEA

Water

Solidification

Packaging

Purification

Pure Water Reuse

Storage

Sediments, resins, sorbents

Reuse

IAEA

Debris

Incineration

Sorting

Wood, organics

Storage

Plastic,

Protection clothes

Compaction

Cables

Solidification

PackagingPackaging

IAEA

Thank you!

36

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