International Workshop on Fukushima Decommissioning Research
24-26 May, 2019
J-Village, Fukushima, Japan

Robots Technology for Decommissioningof Fukushima Daiichi Nuclear Power Stations
26 May 2019

Tamio Arai

Vice PresidentInternational Research Institute for Nuclear Decommissioning (IRID)
Emeritus Professor, The Univ. of Tokyo
The results are obtained under the Subsidy Project of Decommissioning and Contaminated Water Management
granted by the Ministry of Economy, Trade and Industry.
Unauthorized copy and reproduction prohibited.

無断複製・転載禁止 技術研究組合 国際廃炉研究開発機構©International Research Institute for Nuclear Decommissioning

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Contents

 Robots in Fukushima Daiichi

 Missions depending on phases Failures & Countermeasures Requirements for Robots

 Fundamental requirements for robots
 Characteristics of robotics for NPP
 Fuel Debris Detection Technology

 Developed/-ing devices for decommissioningSequence of Fuel-debris retrieval
Fuel Debris Retrieval Technology
Subsystems of an investigating system
Required technology in robot system Design criteria for robots

2©International Research Institute for Nuclear Decommissioning

Robot technology for decommissioning The difficult targets are to retrieve fuel-debris
 to prevent leakage of radioactive substance to prevent re-criticality, under the sever conditions such as unknown, undefined environment
 high radiation level water, high humidity, existing hydrogen complicated obstacles
 large, and heavy mechanisms
 small experiences of operations

 Approach to R&D of robots

 to utilize knowledge of robotics
 to introduce the improvements
3©International Research Institute for Nuclear Decommissioning

Missions depending on phases
Phase
Phase 11: Emergent Situation: Cooling down of reactors
Phase
Phase 22: Stabilization: Containment and systems reconstruction for aftershocks
Phase
Phase 33: Decommission: Fuel removal

Uncertainty

by H. Asama

Uncertainty of objects & purposesby Y. Yokokohji
Phase 11: Emergent countermeasure
Phase
Phase 22: Investigation and appropriate measure
Phase
Existing devices
Phase 33: Full-scale development
Phase
Combination of
Development of devices suitable to the site
established technology

4©International Research Institute for Nuclear Decommissioning

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by courtesy of Prof. Asama

Phase 1

Procure off-the-shelf robots and equipment(for general purpose)

Remotely Controlled
Construction Machines

Brokk-90

QinetiQ Talon

Putzmeister
Concrete Pump Truck

QinetiQ Bob Cat
Honeywell
T-HAWK

iRobot Packbot

Brokk-330

iRobot Warrior

Hajime Asama
Copyright (c) Hajime Asama, Univ. of Tokyo. All rights reserved 20185

by courtesy of Prof. Asama

Phase 2Remodel developed system and technology

QuinceQuince 2

Quince 3
Gamma-ray
Measurement Robot

SakuraRosemary
FRIGO-MA

Quadruped Robot& Inspection Robot

JAEA-3

ASTACO-SORA

Survey Runner

MEISTeR
Inspection Robot
Of upper part of S/C

ROV

Manipulator
for Robot Set-up

Hajime Asama
Copyright (c) Hajime Asama, Univ. of Tokyo. All rights reserved 20186

by courtesy of Prof. Asama

Phase 3New development (for specific use)

Robot forDecontamination

Inspection robot
for high location

Robot for Measurementof S/C Water Level
PCV Inspection Robot
PMORPH

Water Surface
Inspection Robot
Inspection Robot for
Lower part of S/C

PCV Inspection Robot
Mini Mola Mola

PCV Inspection Robot
Scorpion Robot

Hajime Asama
Copyright (c) Hajime Asama, Univ. of Tokyo. All rights reserved 2018

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Failures

 Insufficient specification/Unknown environment Prototypes without improvement
 Operation errors
 Wire handling Lighting and vision Device failure: communication, malfunctions by radiation

Countermeasures

Failures & Countermeasures

 System management: collaboration among R&D+E&C teams
 Design: by frequent design reviews, risk assessment
 Simulations: to estimate effects, time, total quantity
 Mock-up: operation training, severe setting of environment
 Site measurement: point clouds of real environments
8©International Research Institute for Nuclear Decommissioning

by courtesy of Prof. Yokokohji

Lessons Learned from the ＴＭＩ AccidentSuccessful robots were






compact with simple function,easy-to-use and easy-to-maintain,
easy-to-modify according to the needsof the site
common mobile platform

High-function, large-sized robot
was not eventually used
 Development of new robots shouldbe planned carefully because thesituations on the site may change.
Mechano-Media
Kobe Univ.

Remote Reconnaissance Vehicle(RRV) 1 & 2Workhorse

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Contents

 Robots in Fukushima Daiichi

 Missions depending on phases Failures & Countermeasures Requirement for Robots

 Fundamental requirements for robots
 Characteristics of robotics for NPP
 Fuel Debris Detection Technology

 Developed devices for decommissioningSequence of Fuel-debris retrieval
Fuel Debris Retrieval Technology
Subsystems of an investigating system
Required technology in robot system Design criteria for robots

10©International Research Institute for Nuclear Decommissioning

Robots newly developed for Investigation of inside PCV

Two types of shape-changing, remote-controlled, crawler robots for investigation
Investigation of outside the pedestal (Unit 1)

Investigation of inside the pedestal (Unit 2)

When driving
the narrow part
狭隘部走行時DuringDuringinvestigation
investigation

Additional
lighting

Advancing
direction

Rear camera andlighting

Crawlers(two
Camera for guide pipe units)

Duringinvestigation

advancement

Shape changing

Front camera and lighting

CRD rail

Thermometer 調査時
DuringCrawler

investigation

Investigation of inside the pedestal (Unit 3)
Camera forinvestigation

Dosimeter

Driving
thruster

Up-downthruster
Front
camera

Light

11
11

○Hanging camera
on extension rod©International Research Institute for Nuclear DecommissioningSub-systems of robot technology
Operating
room

Brain
(Remote control)
Sensor(Camera, 3Dsensor)

Environment

Effector(Manipulators, Tools)

Obstacles

Objects

Mobility system

Measured data &Control signals
Power supply

PCV
Enclosure

RPV

Collection
deviceArm typeaccess equipment
Fuel debris

12©International Research Institute for Nuclear DecommissioningChallenges on Robotics for decommissioning High doze rate

 Weakness of Sensor-Brain-Effector system
 Radiation-hardened electronic devices
 Sufficient shields onto electronic devices
 Mechanism without electronic parts

 Prevention of contaminated parts

 Washable and fully covered wires, like robots for food industry

 Long/large in size and heavy in weight Low natural frequency of long beams, thus low controllability
 Encapsulations of devices become much larger and heavier
 Joining devices with heavy cells is required Mock-up needs space and cost
 Long turn-around time of improvement

 Undefined environment and objects

 No light, high humidity, many obstacles
 Unknown characteristics of handling objects

13©International Research Institute for Nuclear Decommissioning

Fundamental requirements for robots
 Great amount of debris and obstacles
 Large thus heavy machines
RadiationHigh Radiation resistance High Reliability, Maintainability, Easy-to-operate
For retrieval of fuel-debris,large & heavy robots are
required to cut and handle
debris and obstacles.

Investigation

Retrieval system fordebris & obstacles

Maintenance tasks maychange according to theretrieval devices, sensors.
The robots need to have
longer life-time.

Large

Low

Maintenance &Supporting work

Size
Small

14

Robots for investigation
are as small as it can go
through small
penetration, to prevent
radioactive leak.
©International Research Institute for Nuclear Decommissioning

Characteristics of mechanism
Characteristics of robots:• Large in size, heavy in weight• Low natural frequency at TCP
46m

Industrial robots
 Assembly robot: Reach 1.2m, Ratio≒0.21
Payload 10kg, Own weight 48kg
 Large-size robot: Reach 2.9m, Ratio≒0.20
Payload 600kg, Own weight 3,035kg,

4F

SF
P

11m

5.5m
Dry-well

20m

Torus.

*The robot working inside thePCV has the risk of stuck due tofailures. In view of such a risk,
robots should be designed with asize that can be rescuable.

Bent
pipe

34m

2F
1F

 Investigation arm: Reach 17.7m, Ratio≒0.052
Payload 54kg, Own weight 1,053kg
 Heavy handling robot: Reach 5m, Ratio≒0.125
Payload 100kg, Own weight 800kg

RPV
21m

46m

Robots for Fukushima *9m

Suppression
Chamber

15©International Research Institute for Nuclear DecommissioningPurpose of data sensing
Remote-control

High dose radiation

 to estimate and calibrate  to detect the leak out ofthe pose of sensors
radioactive substance to detect the motions
 to measure the amount offuel debris to excavate
 to introduce maximum
likelihood estimation
 to record the process offuel-debris retrieval
Position & 3D
Measurement
Radioactive
Sensing

SensorFusionActionInventory& History

Time-log &Space-map

16©International Research Institute for Nuclear Decommissioning

Strategies for Countermeasuresagainst Radiation7

by courtesy of Prof. Asama

Shielding– Shield by lead/steel/tungsten (not realistic)– Lead glass

Radiation-hardened devices/components– Radiation-hardened(resistant) Semiconductor– Camera tube(Hamamatsu Photonics) 2MSv dose
– Radiation-hardened Camera (SONY) 1000Sv dose

Robust design(Fault-tolerance/Maintainability)

Rad-Hard devices– Redundant and functionally degradable– Modular design and easy replace

Redundancy Exchangeability
Robustness Maintainability
Complexity
Weight-Size Constraints
Cable dis/connection

 Mechanical systems

 Wire-driven/Tendon-driven
 Hydraulic drive(Water)

17©International Research Institute for Nuclear Decommissioning

by courtesy of Prof. Gotoh

Development of radiation
tolerant image sensor

Photoconductor:

little degradation except coloring of glass30• Vacuum type flat image sensor
with 2D matrix electron source

20

10

See Y. Gotoh et al., FDR2019-1099

Y. Gotoh et al.,IVNC2016 p.20.

0
0.0

0.2

0.4

0.6

0.8

Changes in photovoltaic properties

Electron source (FEA):

little degradation of insulating layer
1010Current ( A )

10
10
10
10
10
10

−5

Spindt−type Ni FEA wR (w/o Focus)
100tip R
Anode
246kGy452kGy592kGy1236kGy

−6
−7
−8
−9

Gate

−10
−11
−12

Re=0
YZ140123B−D3−wR

10

Y. Gotoh et al., FDR2019-1099.

Y. Gotoh et al.,IVNC2016 p.20.

−13

0

20

40
60
Gate voltage ( V )80

Changes in current-voltage characteristics

Radiation-hardened mechanism Flexible Structure Arm (Muscular Robot)

 Control devices are located outside of the high radiation area,
and connected to the cylinder by a tube.
 Joint: 4 water hydraulic cylinders and springs

 Elongation of a cylindercauses the joint to bend Elasticity prevents
unexpected malfunction
caused by collision.
 Hitachi GE and Chugai
Technos have developed
five types of robots using
1 to 4 joints.

19©International Research Institute for Nuclear Decommissioning

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Contents

 Robots in Fukushima Daiichi

 Missions depending on phases Failures & Countermeasures Requirement for Robots

 Fundamental requirements for robots
 Characteristics of robotics for NPP
 Fuel Debris Detection Technology

 Developed devices for decommissioningSequence of Fuel-debris retrieval
Fuel Debris Retrieval Technology
Subsystems of an investigating system
Required technology in robot system Design criteria for robots

20©International Research Institute for Nuclear DecommissioningSequence of Fuel-debris retrieval
Collection, Transfer and Storage of Fuel Debris
Canister design
 High fuel exposure and enrichment → high reactivity
 MCCI → hydrogen generation caused by core concrete interaction
 Injecting sea water, melting cable → effects caused by salt and impurities
Transfer (Dry–side access method）
R/B
Maintenancecell
Storage cellfor fuel debris
retrieval

Carry-out
port(additional)

Transport cell

Fuel debris transportbuilding

Handling cell for astorage canister

Storagefacility

Unit canFuel debris
retrieval

Storing incanisterCanisterTransport cart

Washing acanister

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Transport cask

Storing canisterin a transport
cask

Trailer

Carrying out
a transport
cask©International Research Institute for Nuclear Decommissioning

Fuel Debris Retrieval Technology
A side access method(image)
Equipment cell

Equipment transfer cart

Biological shieldwall (BSW)

Wastes transfer cart

X-6 penetration

e.g. a robot arm

New
opening

Wastes transfer
systemNew
PCV
opening
Seal with BSW-PCV Sealing with the shielding wall
(BSW) and the primary
Equipment
containment vessel (PCV).
transfer system

PedestalPedestal opening

Unauthorized copy and reproduction prohibited.
©International Research Institute for Nuclear Decommissioning

22

e.g. cutting
technology (Chisel)©International Research Institute for Nuclear Decommissioning

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Total:3m40s

Fuel Debris Retrieval Technology: An example

23©International Research Institute for Nuclear Decommissioning

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Subsystems of an investigating system
Arm Type Access Device
 An arm type access device has been produced, which
can access on a wide range through a penetration (X-6)
of PCV.
 Total length of the arm: Approx. 22m
 An investigation device up to 10kg can be loaded.
Trolley

Boom

Telescopic arm

Tilt mechanism

Two-axis joint

Wand*

Mounted sensor at the tip of the arm*An alternative tool can be mounted.

24©International Research Institute for Nuclear DecommissioningSubsystems of an investigating system
Access Route of Arm Type Connecting structure of primary containment vessel (PCV)The connecting structure with thefollowing functions has beendeveloped.
 Remote-operated function withapproaching/attaching an existing
penetration flange Seismic resistance of graspingmechanism Confinement function
 Maintaining arm transmission

Non-metal bellows

Isolation valve
Extension tube
Arm enclosure

Arm

Isolation valve

X6 penetration
connection structure

X6 penetration flange

X6 penetration

Grasping mechanism

Connecting pipe

Grasping mechanism “closing”

Drive mechanism

X-6 penetration connecting structure
Unauthorized copy and reproduction prohibited.
©International Research Institute for Nuclear DecommissioningArmcleaning/drying
mechanism

25

Grasping mechanism “opening”©International Research Institute for Nuclear DecommissioningSubsystems of a retrieval system
Access Tunnel
 The access tunnel is required to connect a heavy-lift tunnel(approx. 800 ton) with PCV through the precise position control
system from outside the reactor building.
 Delivery technology for curved heavy-lift tunnel in narrow space
has been developed with the technology experienced in bridge
constructions.
Carry-in cell

Waste carry-out cell

Fuel debris retrieval cell
Maintenance cell

Fuel debris
carry-out cell

PCV
Access tunnel
Unauthorized copy and reproduction prohibited.
©International Research Institute for Nuclear Decommissioning

26©International Research Institute for Nuclear Decommissioning

Fuel Debris Retrieval Technology
Removing Interfering Objects(image) Various pumps and other structure must be removed.
 A large amount of rubbles have accumulated in the pedestal.
 Technology for removing the interfering objects has been developed.

画質アップ予定

Image of element test of removing interfering materials
Unauthorized copy and reproduction prohibited.
©International Research Institute for Nuclear Decommissioning

27©International Research Institute for Nuclear Decommissioning

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Removing Interfering Objects
at 10x speed/ total 1m22s

28©International Research Institute for Nuclear DecommissioningRequired technology in robot system
 Assembly/Disassembly Operation• Insertion, fitting• Holding parts• Simulator & VR
• Human interface• Team training Cutting/Coring/Separation• breaking fuel debris• Removing Interfering objects

 Investigation• Shape measurement• Radiation measurement• SLAM• Wire handling• Environment design• Power/Energy supply

Brain(Remote control)

Sensor(Camera, 3Dsensor)

Environment

Operatingroom

Effector(Manipulators, Tools)

Objects

Obstacles

Measured data &Control signals

Mobility system

Power supply

 Transportation• Long transportation of heavy cells in radiative env.
• Precise connection/mantling/dismantling

29©International Research Institute for Nuclear DecommissioningFour kinds of robots

RadiationHigh

 Investigation (remote control) Retrieval system (remote control + semi-automatic)
 Maintenance robots (remote control + automatic ) Mounting robots (remote control + semi-automatic)

Investigation

Retrieval system fordebris & obstacles

Mounting/Dismounting/Connecting robots

Large

Low

Maintenance &Supporting work

Size
Small

30

©International Research Institute for Nuclear Decommissioning

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Contents

 Robots in Fukushima Daiichi

 Missions depending on phases Failures & Countermeasures Requirement for Robots

 Fundamental requirements for robots
 Characteristics of robotics for NPP
 Fuel Debris Detection Technology

 Developed devices for decommissioningSequence of Fuel-debris retrieval
Fuel Debris Retrieval Technology
Subsystems of an investigating system
Required technology in robot system Design criteria for robots

31©International Research Institute for Nuclear DecommissioningReliability

When machines are large(ℓ),
its weight is in proportional to
３ and required torque ℓ.
４ℓ,
Therefore, largeness in size
causes various problems.

Low←

Machines for nuclear plants aredesigned as it works in slow,
secured motion.

→High

Design criteria for robots (1)Industrial robots and humanoids are
Low←
Flexibility
designed as intelligent and(Single-function)
adaptable as human to the change
Dedicated machineof requirements and environment.
Thus, higher flexibility is embedded.

→High(Multi-function)

When one ability must be improved, the other often turns worse. Bytaking zig-zag changes, both ability will be improved.

32©International Research Institute for Nuclear Decommissioning32

Machines in nuclear reprocessing plants
can be dedicated to a specialized task.
But decommissioning in Fukushima
Daiichi needs to have higher productivity
because of huge amount of fuel debris
and other structural materials.
To achieve it, machines should be rearranged and improved in good balanceof the three axes; reliability, flexibility
and productivity.
An initial machine should be simple
enough, then zig-zag improvement
must be introduced.
The effect of size and weightmust be taken into account.

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Low← Reliability→High

Design criteria for robots (2)Low←

Flexibility(Single-function)→High(Multi-functions)©International Research Institute for Nuclear Decommissioning

Summary Radiation-hardened devices are key issues
for robots for decommission.
 Size and weight cause various problems inremote control: long turn-around time of
improvement and cost.
 Training of operation teams is the mostimportant key for remote control.
 Balance of reliability, flexibility (multifunction), and productivity must be welldesigned in the development of robots.
©International Research Institute for Nuclear Decommissioning

Thank you for your kind attention
Decommissioning of Fukushima Daiichi NPP
is an epoch-making and historical project.
Let us watch, understand and memorize the project.

Tamio Araitamio-arai@irid.or.jp
無断複製・転載禁止 技術研究組合 国際廃炉研究開発機構©International Research Institute for Nuclear Decommissioning

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