© Nov. 2017 ANDES

Tokai 1 Decommissioning Experience

The Association for Nuclear Decommissioning Study

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Tadamichi Satoh

Nuclear Engineering & Services Co.

Association for Nuclear Decommissioning Study

2017 Sino-Japanese Workshop on NPP Decommissioning Technology

November14, 2017 @ Atomic Energy Council ３Ｆ

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Decommissioning Projects in Japan

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Progress of Japanese Decommissioning Projects

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1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050

Tokai-1

GCR

Fugen

ATR

Hmaoka-

１，２

BWR

Tsuruga-１

BWR

Mihama-

１，２

PWR

Genkai-１

PWR

Shimane-１

BWR

Ikata-１

PWR

Fukusima

Daiichi

BWR

? ?

SF ShipmentPreparation Peripheral Reactor Building

Removable of SF

Removable of Fuel-Debirs Decommissioning

DP

DP

DP

DP

DP

DP

DP

DP

DP：Approval of Decommissioning Plan

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Shooting date：Dec 2001(before removal of outdoor piping)

Tokai-1 Decommissioning Project~The First Decommissioning Project for

Commercial Reactor in Japan ~

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SPENT FUEL CARTRIDGE COOLING POND

REACTOR BUILDING

TURBINE HALL

PIPE BRIDGE

TURBINE

GENERATORTRANSFORMER

CONDENSER

COOLING

WATER

CULVERT

BASEMENT PILEBASEMENT STRUCTURE

BASEMENT PILE

STACK

CHUTE

CHARGE MACHINE BRIDGE

REACTOR

CORE

STEAM RAISING UNIT

BIOLOGICAL SHIELD WALL

REACTOR PRESSURE VESSEL

Moderator : Graphite

Coolant : Carbon dioxide Gas

Reactor vessel : Spherical shape, 18m diameter

Steam Raising Unit : 4 Units

Turbine Generator : 83 MWe × 2 Units

Operation term :1966～1998(for 31 years operation)

Defueling and shipment :1998.5.28～2001.6.21

Tokai-1 is the first commercial NPP in Japan

Reactor Type:Gas Cooled Reactor

Capacity :166 MWe

Fuel :Metal Natural Uranium with Magnox Cladding

Tokai-1 is the sole Magnox NPP in Japan

Tokai-1 is the oldest NPP in Japan

Unit cost became higher than LWRs

Jun.1996 Formal announcement for closure

Mar.1998 Permanent Shutdown

May.1998-Mar.2001 Defueling

Jun.2001 The last shipment of Spent Fuel

Oct.2001 Submitted the notification of decommissioning plan

Dec.2001 Commenced Decommissioning work

Outline of Tokai-1

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Project Mission

Tokai-1 project has important roles for;

Demonstrating the safe and economical decommissioning of commercial NPP

Establishing key technologies for the future LWRs decommissioning in Japan (Remote dismantling techniques & Waste management strategy)

Promoting rule making and realization of waste route

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Project strategy

All facilities will be removed. After decommissioning , the

land is to be reused for future nuclear power operation

Reactor structure will be dismantled after 10-year safe-

store

Conventional components will be removed during reactor

safe-store to utilize existing human resources

Project program is divided into 3 phases because of long

term project

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Waste disposal facility will be constructed prior

to reactor dismantling

If a disposal facility is not available, safe-store

period is to be extended

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JFY2001

02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17

Safe-Storage of Reactor Area

Remove Facilities except Reactor Area

Reactor Area Dismantling

Remove SRUs

Remove Facilities

from each Building

Reactor Dismantling

BuildingsDemolition

Remove Conventional Facilities e.g. turbine

First PhaseSecond Phase

Third Phase

Original Plan for Tokai-1 Decommissioning

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First phase: 5 years

1.Isolate reactor structure for safe store by valve out and plugging.

2.Drain and cleanup spent fuel cooling pond.

3.Remove components in turbine and reactor auxiliary buildings, including

the fuel charge and discharge machines.

123

33

3

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1.Remove 4 SRUs

2.Install Radwaste Treatment System

1

Second phase：5years

2

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Third phase (first step): 5years

Reactor structure is to be dismantled by remote

operation manipulators.

1.Withdraw reactor inserts and take out graphite blocks

2.Dismantle RPV and Internals

3.Remove activated concrete shielding structures

1

1

2

3

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Third phase(2nd step)：2 years

1. After final survey, demolish all building structures

except basements and underground structures.

2. Finally, adjust the land on ground level.

1

1

1

2

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Summary of First Phase

During the first five years of decommissioning programme,

JAPC got successful results

JAPC has managed each task as

scheduled and as budgeted

No serious trouble and accident

DIY policy enables JAPC to

accumulate practical know-how

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Item PlanActual

achievement

Manpower (man-day) 54,700 53,416

　Worker dose （man-mSv） 250 297

Amount of wasteand material（ton）

10,690 10,275

First phase (2001-2005) actual result

*Total amount to be arose from whole the decommissioning project: 196,600ton(Radioactive waste：68,000 ton、Non-radioactive waste：128,700 ton)

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Some additional slides will be presented in the presentation.

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JFY

2001020304050607080910 11 12131415 16 17 18 19 20 21 22 23 24 25

Safe-Storage of Reactor Area

Remove Facilities except Reactor Area

Reactor Area Dismantling

Remove SRUs

Remove Facilities from each Building

Reactor Dismantling

Current Plan for Tokai-1 Decommissioning

Remove Conventional Facilities e.g. turbine

BuildingsDemolition

First Phase

Second Phase Third Phase

８ Years Delay

1st SRU 2nd SRU

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Sequence

2.Remove gas duct

1.Remove peripheral equipment

3.Remove SRU

Specification of SRU

Number 4 units

Material Carbon steel

Height

Diameter

24.7 m

6.3 m

Weight

750 ton/unit・Shell

250 ton/unit･Tubes

500 ton/unit

No.1,2,3,4 completed

No.1,2,3,4 completed

No.1,2 completed

[2nd Phase] SRU Dismantling Concept

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Storage

【Work Image at Work area at third floor】Remote cutting sys（Manipulator arm）

〔Primary cutting〕 〔Tier transfer〕 〔secondary cutting〕

PreparationLarge jack installationRemote cutting sys

installation

Cutting & removalPrimary cutting（Divide tiers）Secondary cutting（Cutting into pieces）

Temporal pedestal &

Jack sys installation

Jack Down

（Tiers 1-9 removal)

Temporal pedestal &

Jack sys removal

Work area at

third floor

1st SRU Dismantling Method

Large Jack

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Concept of Waste Treatment & Disposal

Tunnel or silo(50m-100m underground)

Concrete pit(10m underground)

Trench

Recycle & Disposal

27,500

(1,600)

(12,800)

(13,100)

169,000Non-Radioactive

waste*

Cont

ainer

Interim site storage

[In site storage facility]

Pack

ing

Interim site storage

[In site storage facility]

Interim site storage［In-site］

Low Level wasteDisposal facility

TreatmentVolume reduction;Metal, concrete,graphite(Including melting& burning)Decontamination;metal

TreatmentVolume reduction;Metal, concrete,Decontamination;metal

This amount is after decontamination

*Including clearance waste

Graphite

Metal

Graphite

Metal

Concrete

Metal

Concrete

Metal

Concrete

Amount (t)

［Metal］ ・Recycle

［Concrete］・Gravel for landfill

Comparativelyhigh radioactivelevel(L1）

Comparativelylow radioactivelevel(L2）

Very lowRadioactive level

(L3）

Low level waste

Tunnel Silo

Cover soil

Cover soil

Waste

Type

L1

L2

L3

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Key Constraints in Japan

1. Decommissioning LLW disposal L1 waste : Regulatory standard is being developed.L2 waste : Current JNFL disposal facility is only for

operating waste.L3 waste : JAPC Tokai L3 disposal facility is under licensing

review. Each utility individually consider own L3 disposal.

2. Clearance of materialConditional release ⇒ Free releaseExcessive conservatism in verification measurement and

licensing review

3. Non-radioactive(NR) material in radiation control areaExcessive conservatism required for judgement(Required too much evidences, e.g. documents, records and

measurements)

4. Spent Fuel Paths

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Key Elements for Successful Decommissioning ~ Lessons Learned from Tokai-1 Project ~

1. Securing necessary funds- Exact cost estimation and its update- Understanding its uncertainties

2. Characterization! Characterization!!Characterization!!!- Developing radiological characterization by the

combination of calculation models and measurements- Review and analyze the results (cross-check) and update

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- On a room by room basisfocusing on materials (wastes).

•Don’t utterly trust ‘As built’ drawings•Review available documents, records and old photos•Perform interview of former or current workers•Address all the hazards (incl. non radiological one)•Focus on materials in each room,not on each components in each system

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- Database should be established which provide significant input into assess & decision on ;

•D&D techniques: decontamination processes, dismantling processes ( hands-on, semi-remote, fully remote ) and required equipment

•Radiological and industrial protection of workers, public, and environment

•Waste management, waste classification & its verification•Waste disposal and Recycling options•Cost estimations

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3. Downsizing of utilities- Early Establishment of Cold & Dark and Nuclear Island- Regarding systems and major equipment,

consider the following options:・Operable as is・Modified・Preserved for the future・New・Retired

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4. Waste Routes- Do not rush into showing ‘visible progress’ before waste routes are secured.

・Temporary space in working place ・Carrying routes ・Temporary area for waste storage & waste treatment, ・On site Interim storage facility ・Final disposal

- Maintain detailed and accurate records on the contents of waste packages

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5. Total optimization- Consider the overall optimization from Decontamination/Dismantling process to Waste treatment & conditioning / Disposal process“The next processes are our customers.”

6. Hands-on approach - Combination of low-tech and high-tech- In some cases, R&D and innovative technologies may increase Project Risks(cost)

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7. Project completion oriented management

- New and different management reflecting the need for greater emphasis on project management(different from operational phase where activities are generally routine

and well practiced by a stable work force)

- The management to be flexible and able to respond quickly to new situations

⇒ Vesting the local site management with a range of powers

(various new decommissioning activities may need closer day-to-day control or supervision)

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8. Change Culture and Mindset

・ Production oriented management VS Objectives Project completion oriented management objectives

・ Focus on functioning of systems VS Focus on management of material and radioactivity inventory (e.g. for waste minimization)

・ Reliance on permanent structures for the operating life of the facility VSIntroduction of temporary structures to assist dismantling

・ Predominant nuclear and radiological risk VS Reduction of nuclear risk, changed nature of radiological risk, significantly increased industrial risk

・ Low radiation/contamination levels relatively unimportant VS Low radiation/contamination levels important for material clearance

9. Dedicated Organization & Combination of Human Resources

- Different phases have different needs and therefore different knowledges, skills ( supply chains ) and leadership

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10. Incentive- Decommissioning is not the end, the importance of a future beyond decommissioning

11. Avoid Excessive Protection and Over-Regulation

12. Stakeholder Involvement- Communication with local community is important. It leads

to a successful decommissioning.

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Conclusions

・ Key points for the safe（安全）, smooth（順利）, and reasonable（合理的） decommissioning - Waste Management - Organization & Management- Culture & Mindset change

・ Non-technical factors are often more important than technological factors

・ Decommissioning is “Experience Engineering（経験工学）”Take lessons from one work (one project) to make improvement at the next.

・ International cooperation and exchange of decommissioning experience improve project efficiencies and improve safety.

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End of Presentation

Tadamichi Satoh

Secretary-General

The Association for Nuclear Decommissioning Study

Address:

401 Yoshida Bldg., Kudan-kita, chiyoda-ku,

Tokyo 102-0073 Japan

Phone: +81-3-6272-4150

Fax: +81-3-6272-4470

E-mail: satoh-sg@decomiken.org

URL: http://www.decomiken.org