Subsidy Project of Decommissioning and Contaminated Water Managementin the FY2015 Supplementary Budgets

Development of Technology for
Detailed Investigation inside PCV
Accomplishment Report for FY2017

April 20, 2018
International Research Institute for Nuclear Decommissioning (IRID)
All Rights Reserved.
International Research Institute for Nuclear Decommissioning©International Research Institute for Nuclear Decommissioning

1

Contents

1. Research Background and Purposes
1.1 Reason Why the Research Project is Needed
1.2 Application and Contribution of the Study Results
2. Implementation Items, Their Correlations, and Relations with Other Research
2.1 Implementation Items on the Research
2.2 Implementation Items and Relations with Other Research
2.3 Project Goals
3. Schedule and Project Organization
4. Implementation Details
4.1 Implementation Items and Results: Formulation of Investigation Plan and Development Plan
4.2 Implementation Items and Results: Establishment of Access Route into PCV through X-6
Penetration
4.3 Implementation Items and Results: Establishment of Access Route into PCV through X-2
Penetration
4.4 Implementation Items and Results: Access and Investigation Devices
4.5 Implementation Items and Results: Applicability Verification of Element Technologies
5. Overall Summary©International Research Institute for Nuclear Decommissioning1. Research Background and Purposes
1.1 Reason Why the Research Project is Needed[Background]
Investigations inside PCVs were performed in thefollowing government-led projects in the past: B1/B2
Investigations (Unit 1), A1/A2/A2’ Investigations (Unit 2),
and Unit 3 Investigation using a small ROV.
While valuable information was obtained by theseinvestigations, the size of the existing openings has
limited the scope of the investigation.

2

Primary containment
vessel(PCV)Reactor building
structure

Reactor pressure
vessel (RPV)

Pedestal

Equipment hatch[Objectives]
Following the aforementioned investigations, the detailed
investigation inside PCV (hereinafter referred to as the
Detailed Investigation) aims to re-examine and analyze
the needs first and to perform investigation and establish
relevant technologies necessary to meet such needs inorder to meet the requirements for fuel debris retrieval.
In the Detailed Investigation, the development will beadvanced while putting priorities on gathering information
for the pressing tasks required for fuel debris retrieval: thedetermination of fuel debris retrieval method, the detailed
design of retrieval devices, and the samplingtechnologies.

Existing opening(X-2 penetration)

Existing opening(X-6 penetration)

Scope of detailed investigation inside PCV(basement floor inside/outside the pedestal,
CRD system)[Outline of PCV cross-section andinvestigation points]©International Research Institute for Nuclear Decommissioning

3

1.2 Application and Contribution of the Study Results
FY2016-2017 Development of technology for investigation inside PCV

FY2017-2018* Development of technology for detailed investigation inside PCVFormulate investigation planand development plan

Develop the access andinvestigation devices(Project)

Verify the applicabilityof element technologies*Continuing using the FY2016
supplementary budget

On-site verification

Respective researches on detailed designs ofmethods and devices used for fuel debris retrieval(such as fuel debris retrieval, earthquake
resistance, repair, and criticality control)
Information for the determination of fuel debris
retrieval method, the detailed design of fueldebris retrieval devices, etc.

Research on
fuel debris sampling

Information necessary for the sampling
planning, etc.

©International Research Institute for Nuclear Decommissioning2. Implementation Items, Their Correlations, and Relations with Other Research
2.1 Implementation Items on the Research
Implementation items

Scope of development activities for FY2017

SectionnumberFormulation of the investigation Continuous review, materialization, and update of theplan and the development plan investigation plan based on the latest situation of the site

4.1

Establishment of access route
into PCV through X-6
penetration

Design, production, and a part of the in-plant verification
tests of full-scale prototypes for devices used to establish
access routes into the PCV

4.2

Establishment of access route
into PCV through X-2
penetration

Design, production, and a part of the in-plant verification
tests of full-scale prototypes for devices used to establish
access routes into the PCV

4.3

Narrowing down of access/investigation devices, and design,
production, and a part of in-plant verification tests of fullscale prototypes for said devices

4.4

A part of the verification testing for measurement technology
to be incorporated into the access/investigation devices

4.5

Access and investigation
devices
Applicability verification ofelement technologies©International Research Institute for Nuclear Decommissioning

45

2.2 Implementation Items and Relations with Other Research
Investigation outside the pedestalof Unit 1 (including on-site verification)[Development of technology for PCV investigation]

Investigation inside the pedestalof Unit 2 (including on-site verification)
Investigation inside the pedestalof Unit 3 (including on-site verification)

Planning and element test for basement floor
investigation/Development plan formeasurement devices, etc.

[Project items (FY2017-2018)]
Formulation of the investigation and development
plans• Update and materialization of the plan based on the latest
information on the inside of PCVs

Access and investigation devices• Narrowing down of the access devices• Detailed design, prototype production, and in-plant verification
tests of access/investigation devices

Applicability verification of element technologies• Verification of the measurement technology to be incorporated in theaccess/investigation devices

Establishment of access route into PCV
through X-6 penetration
Establishment of access route in Unit 2
Design, production, and unit function test of theisolated room, hatch opening mechanism, etc.

Establishment of access route in Unit 1
Conceptual design, basic plan, and element
test for the devices relevant to theestablishment of access routes into PCV

On-siteverification(Unit 1&2)
(Investigation to
be started in
FY2019)• in-plant verification of the isolated room, hatch opening mechanism,etc.
• Detailed design, prototype production, and in-plant verification testsof the connection with the investigation device

Establishment of access route into PCV
through X-2 penetration
Detailed design, prototype production, and in-plant verification
tests of devices for the establishment of access route into PCV©International Research Institute for Nuclear Decommissioning6

2.3 Project Goals
Implementation Details
Formulate investigation planand development plan

Establishment of accessroute into PCV through X-6
penetration

Target achievement indicators (FY2017-2018)

Units 1, 2

The investigation plan and the development plan shall be reviewed, materialized,
and updated based on the latest situation of the site.

Unit 3

The applicability of the devices developed for Units 1 and 2 to Unit 3 shall be
studied, and it shall be made clear whether a development issue exists.

Opening of the hatch

Design, full-scale prototype production, and in-plant verification tests shall becompleted for all devices relevant to the establishment of the access route into the
PCV.

Connection of new boundary The feasibility evaluation of the extension pipe shall be completed.

Establishment of access route into PCV through X-2
penetration

In the process of establishing the access route into the PCV, the design,
production, and in-plant verification tests of full-scale prototypes for all devices
relevant to the connection with the investigation device shall be completed.

Access and investigation devices

Access/investigation devices shall be narrowed down and the design, production,and in-plant verification tests of full-scale prototypes for all selected devices shallbe completed.

Applicability verification of element technologies

Verification tests of measurement technologies incorporated in theaccess/investigation devices shall be completed.

Development of a measurement
device using laser-based optical
The verification of the substitute mirror shall be completed.
cutting method applicable in
Candidates of substitute cameras shall be narrowed down before verifying them.
atmosphere, which can substitutethe one that went out of production
Mockup test plan

The rough design of the mockup test facility used for the test of the arm-typeaccess device shall be completed.

©International Research Institute for Nuclear Decommissioning3. Schedule and Project Organization (1/2)

7FY2018FY2017Items
Determine fuel debris retrieval policy
Grant decision (Apr 1(tentative))
Revise the implementation plan (establishment of access routes into PCVs)

Master Schedule

Prepare the areas

Tasks indicated bydash-dotted lines areout of the scope of thissubsidized project.

Formulate investigation plan anddevelopment plan

Hold point (narrowing down)

Hold point(materialization and update of the plan)

Materialize and update the investigation anddevelopment plans

Materialize and update the investigation anddevelopment plans

Detailed design 2Manufacturing and verification of prototypes (to be continued where necessary)
in-plant verification (as FY2017 activities)

Detailed design 1

DevelopmentofDevelopment ofaccess/invest
access/investig
igationation devices
devices andelementtechnologies: Achievement (thick
red line)

Detailed Investigation(to be continued where necessary)

in-plant verification (as FY2018 activities)

Establishmentof accessroute into PCV
through X-2
penetration

The work progress is indicated by thefollowing lines:: Plan (thin black line)

Establishment of access routes into PCVs

Detailed design 1

Establishmentof accessroute into PCV
through X-6
penetration

Determine fuel debris retrieval method for the
initial unit
FY2016 supplementary budget▽
Subsidized project to be completed(Mar 31)

FY2015 supplementary budget
Subsidized project to becompleted (Mar 31)(Note)
1) Black lines show implementation
items included in the grantapplication form.
2) Dash-dotted lines show
development items beyond thescope of this grant application asa reference.

Detailed design 2(to be continued where necessary)
Manufacturing and verification of prototypes(to be continued where necessary)
in-plant verification (as FY2017 activities)(to be continued where necessary)
in-plant verification (as FY2018 activities)[Arm-type devices]
Detailed design 1
Detailed design 2Manufacturing and verification of prototypes (as FY2017 activities)(to be continued where necessary)

Manufacturing and verification of prototypes (as FY2018 activities)

Access andinvestigation
devices

in-plant verification[Submersible-type device]
Detailed design 1
Detailed design 2(to be continued where necessary)(to be continued where necessary)
Manufacturing and verification of prototypes (as FY2017 activities)
Manufacturing and verification of prototypes (as FY2018 activities)(to be continued where necessary)

in-plant verification (as FY2017 activities)
in-plant verification (as FY2018 activities)

Applicability verificationof element technologies(to be continued where necessary)

Applicability verification (as FY2017 activities)

Applicability verification (as FY2018 activities)(to be continued where necessary)©International Research Institute for Nuclear Decommissioning

8

3. Schedule and Project Organization (2/2)
International Research Institute for Nuclear Decommissioning(IRID)• Formulation of overall plan and technical management• Coordination of technical management including progress of technicaldevelopment

Hitachi-GE Nuclear Energy, Ltd.

Toshiba Energy Systems &Solutions Corporation

Mitsubishi Heavy Industries, Ltd.

1) Formulate investigation anddevelopment plans

1) Formulate investigation anddevelopment plans

1) Formulate investigation anddevelopment plans2) Develop access/investigation
devices and element
technologya) Develop access/investigation
devices• Establish access route into
PCV through X-2 penetration• Access/investigation devicesb) Verify applicability of element
technology2) Develop access/investigation
devices and element
technologya) Develop access/investigation
devices• Establish access route into
PCV through X-6 penetration

2) Develop access/investigation
devices and element
technologya) Develop access/investigation
devices• Establish access route into
PCV through X-6 penetration• Access/investigation devicesb) Verify applicability of element
technology©International Research Institute for Nuclear Decommissioning9

4. Implementation Details
4.1 Implementation Items and Results: Formulation of Investigation and Development Plans (1/5)—Approach toward the update of the investigation plan—Interview survey
Selection of investigation
subjects
Target deadline forinvestigation
Priorities of investigation

1) Needs interview surveys conducted with relevant projects, the decommissioning company (TEPCO)
2) Subjects of the interview survey: investigation items, objectives, needs, deadlines (detailed design for debris
retrieval, license application, needs after the start of debris retrieval), examples of utilizing investigation outputs,
minimum requirements for the investigation

The objectives and needs of the investigation were examined, andinvestigation subjects relevant to TEPCO and the Detailed
Investigation were selected.
The target deadline of the investigation was identified, andinvestigation items that would provide information beneficial to thedetailed design of debris retrieval were extracted from the investigation
subjects.
The priority of the investigations was studied based on thecharacteristics of each unit.

IRID Head Officeconducted a review
from a comprehensive
perspective
and determined theinvestigation items.

Results of investigation item selection
Investigation for obtaining the information beneficial to the detailed design

Formulate investigation
plan

Presence/absenc
e of shell attack

Completed in FY2016

Depth of erosion bydebris/concrete
strength after being
subjected to thethermal history
caused by theaccident

PCV condition

Earthquake Criticality
Repairresistancecontrol

Investigation items by unit
Unit 1

Unit 2

1-2

Distribution of fuel debris flowed out of thepedestal (thickness, dispersion (boundary))















-

-

1-4

Fuel debris distribution in the pedestal (thickness,dispersion)



















1-5(1)

Shape of fuel debris on the basement floor







1-9

Surface (or internal) temperature of fuel debris on
the basement floor



-

-

-

1-10

Dose rate of fuel debris on the basement floor



-

-

-

Add. 1-12

Cooldown state of fuel debris on the basement
floor (presence/absence of areas exposed to air)

-



-



-

-

-

-

-























-

-

-

-

-

-

TEPCO




Unit 2

2-2

Damage by shell attack, leakage area

3-1

Erosion depth of the pedestal floor

3-2Erosion depth of the pedestal wall







3-4

Cracking or peeling of the inner and outerpedestal walls







4-2

Damage condition of CRD system (falling of
CRD housing, cooling water dripping)4-3

Deposit condition of fuel debris in the CRD
system (shape,
distribution)

5-2

Degradation condition of coating inside PCV

CRD system
condition

To be performed in FY2017(This Research Project)

Conditions
inside thereactorvessel

Unit 3MergedDebris distribution
inside/outside thepedestal

Debrisretrieval[Legend] : Information without which the plan becomes excessively conservative, : Information that has substitute methods, or information to be collected when or after deciding the method©International Research Institute for Nuclear Decommissioning4.1 Implementation Items and Results: Formulation of Investigation and Development Plans (2/5)

10Materialization and update of the investigation plan for Unit 1 (1/3)[Progress status] Based on the latest results of the investigation inside the PCVs of Units 1 and 3, whose damages are
assumed to be significant, a review was conducted on how to advance the investigation toward the fuel debris retrieval
while considering the presence of a large amount of deposits and fallen objects and the plan of the detailed investigationin Unit 1 was updated.
(a) Latest information on the inside of PCVs of Units 1 and 3, whose damages are assumed to be significant
Unit 1
Estimate diagram of fuel debris
distribution

Almost no fuel in the corearea

Investigation results inside PCV in Unit 1(B2)(1) A large amount of deposit was observed
outside the pedestal, and the height of thedeposit surface near the workers access
opening was approx. 1 m at the highest point.
(2) In the surface layer of the deposit, Cs-137
was found as the major nuclide, and Co-60
that is associated with fuel debris was notdetected.

The representative images obtained are below:

Shadow created by theapproaching measurement unit

Opening

Pedestal
Existing structure

Image near thelowest point
Image near the lowest point

Image near thelowest point

Image near the lowest point

Fallen object

Cross-section of PCV 1F
Fallen object

・The detailed measurement points
are currently being evaluated.

Most fuel has melted anddropped to the PCVImage near thelowest point

Image near the lowest point

Unit 3
Estimate diagram of fueldebris distribution

A part of the fuel debris
exists at the RPV bottom

Fuel possibly exists inthe core area

A part of the fuel debris
has dropped to the PCVInvestigation results inside PCV in Unit 3
1) The investigation revealed that, inside thepedestal, the support jig for the CRD housing
had been dropped or deformed, what appeared
to be solidified molten material had been
deposited, multiple structures and grating had
been damaged or fallen off, and pebble andsand deposits had been present.
2) Due to fallen objects, etc., the workers access
opening could not be located.

Control rod drive(CRD)
housing
Platform

Opening (Slot)
Workers access
opening
Basement floor©International Research Institute for Nuclear Decommissioning4.1 Implementation Items and Results: Formulation of Investigation and Development Plans (3/5)

11Materialization and update of the investigation plan for Unit 1 (2/3)(b) Summary of the Detailed Investigation of Unit 1 (on-site verification)*1
In Unit 1, a large amount of deposit has been found, and the CRD housing and in-core components have possibly fallen down;
therefore, the deposit and fallen objects need to be collected and removed at the time of (or before) the fuel debris retrieval. The onsite verification for the Detailed Investigation of Unit 1 aims to collect information regarding the review of means and facilities fordeposit collection, and the work plans for deposit collection, dismantling and removing the fallen objects, etc.

A

B

Required priority information
Outside pedestal Workers access opening(A in the figure)

Information regarding the review of means and facilities used for deposit collection(such as the amount and origin of the deposits), information regarding the plans fordeposit collection, dismantling and removal of fallen objects, etc. (such as thecondition under the deposits, dispersion of fuel debris)

Inside pedestal(B in the figure)

Information regarding the planning of deposit collection, fallen object dismantlement
and removal, etc. (information regarding the work space inside the pedestal and thecondition of the fallen CRD housing)A
Investigation methods• Visual observation• Measurement*2• Deposit sampling
・Visual observation(If the measurement device
can enter inside the pedestal,measurement will also be
performed.)*1: 3D mapping of the deposit surface, measurement of the deposit thickness, detection of fuel debris inside and under the deposit*2: This is included in the scope of the project “Development of technology for detailed investigation inside PCV” based on the FY2017©International Research Institute for Nuclear Decommissioning
supplementary budget, subsidies for the government-led R&D program on decommissioning and contaminated water management (on-siteverification of the technology for the Detailed Investigation on the premise of deposit management).

4.1 Implementation Items and Results: Formulation of Investigation and Development Plans (4/5)

Materialization and update of the investigation plan for Unit 1 (3/3)(c) Process flow from the Detailed Investigation of Unit 1 through the fuel debris retrieval• Is fuel debris contained in the deposit?
• What are the distribution and amount of the deposit?
• What are the origins of the deposit? Will the deposit increase?
• What method is used for deposit collection? Suction
technique?
• What method is used for separating the deposit from water?
and so on• Information that can be obtainedin the process of local removalof the deposit• Visual information under thedeposit(local)Operation during deposit removal[under review in relevant projects]

Existing
N/A• How has the fuel debris been dispersed under thedeposit?
• Any obstacles inside the D/W?
• What is the condition of the pedestal opening?
• What is the condition of the deposit and fallen objects
inside the pedestal? Is there a work space? and so on• Fuel debris shape• Fuel debris dispersion(condition under the deposit)
・Integrity of pedestal
・Falling of CRD housing• Is there cracking or peeling of the pedestal wall?
• Has the deposit entered the vent pipe side? and so on

Safety system,
Criticality control©International Research Institute for Nuclear Decommissioning

124.1 Implementation Items and Results: Formulation of Investigation and Development Plans (5/5)

13Materialization and update of the investigation plan for Unit 2➢➢➢

The A2/A2’ investigation confirmed that the grating had dropped and debris (partially including what appeared to be fuel debris)
had been deposited inside the pedestal. Based on the latest condition of Unit 2, the detailed investigation needs werereorganized, and the development plan for the arm-type access device and sensor is currently being updated.
In the current design of the arm-type access device, there is an issue in establishing a route through which the arm tip descends
to the pedestal bottom. Also, the accessibility of the workers access opening at the pedestal bottom needs to be reviewed andConfirmed to see whether deposit has flowed out of the pedestal through the opening.
To observe the damage condition of the CRD system (at the RPV bottom), development of a sensor system such as a camera
with wiper is considered necessary. In addition, a review is required to see if the presence/absence of deposit adhesion can beassessed.

Unit 2Developing an appropriate
route for descending of thearm-type access device isrequired.

Estimate diagram of fueldebris distribution

A part of the fueldebris exists at the
RPV bottom

CRD
Platform opening

Fuel possibly exists
in the core area.

A part of the fueldebris has dropped to
the PCV

The study on the investigation
method is required whether
debris has spread out throughthe workers opening.

A camera with wiper isrequired to observe thedamage condition of the
CRD system.

Results of the investigation inside the PCV in Unit 2 (A2)
1) Confirmed the falling or deformation condition of theplatform grating and multiple openings
2) Confirmed deposit at the bottom and attachment on the
CRD exchanger, etc.
3) Confirmed deposit near the workers opening at the bottom

Inside pedestal

Need to review amethod to investigate
whether deposit©International Research Institute for Nuclear
Decommissioning
Pedestalbottomadhesion exists

4.2 Implementation Items and Results: Establishment of Access Route into PCV through X-6 Penetration (1/3) 14

1) Opening the hatch
In order to establish a route for the investigation device to access through the X-6 penetration into the PCV in Unit 2, the hatch of theX-6 penetration will be opened remotely while securing the PCV boundary.

[Progress status] In this project, a part of the combination test was carried out using the prototype units including the isolated roomand the hatch opening mechanism, for which the unit function test was performed in the FY2017 project “Development of technology
for Detailed Investigation inside PCV.”(1) Confirmed the feasibility of the carrying-in/assembly/carrying-out of the isolated room (shown in the blue callout)(2) Operation confirmation test for the hatch opening mechanism, etc. inside the assembled isolated room (shown in the orange
callouts)
Isolated room
- Confirmed the feasibility of carryingin/assembly/carrying-out

Hatch opening mechanism- Confirmed the opening
operability, etc.

Assembled isolated
room

Image of the isolated room being
carried in

Hatch opening
mechanism

Isolated roomX-6
penetration

X-6
penetration

Hatch opening mechanism- Confirmed traveling performance,
etc.

X-6
penetration

Hatch opening
mechanism: Camera shooting
direction

for Nuclear Decommissioning
Rescue ©International Research InstituteRescuewire tool
wire tool4.2 Implementation Items and Results: Establishment of Access Route into PCV through X-6 Penetration (2/3) 15

2) Connection of new boundary (1/2)
Earthquake resistancea) Connection structure for X-6 penetration[Progress status]➢ The basic connection structure for the X-6 penetration was decided
applying the holding mechanism that was one of the outcomes of the
FY2016 project “Development of Technology for Detailed Investigation
inside PCV.”➢ Specifications necessary for short-period maintenance of the boundary
were developed.
➢ Strength evaluation and seismic evaluation were performed for theholding mechanism and confirmed that the strength and supporting force
were satisfactory.
(Operation test is scheduled for the next fiscal year.)➢ The large-diameter isolation valve (D 550 mm) was selected from themultiple forms.
➢ Task details were determined for the carry-in step and installation step,
respectively, and shielding design was studied based on the radiation
exposure evaluation.
Isolation
valve

Nonmetallic
bellows

DesignEquivalent to JSME
class 3,applied mutatis
mutandis

Welding procedure, welding andtesting

JIS

Isolation
valve
Extensionpipe

X-6 penetration flange

Arm enclosure

X-6
penetration
X-6 penetration
connection structure

Arm

Grippingmechanism

Connection
pipe body

Drive
mechanism

Plant
welding
sectionClass B

Gripping mechanism “Closed”

Armcleaning/drying
mechanism

Gripping mechanism “Open”

X-6 penetration connection structure©International Research Institute for Nuclear Decommissioning4.2 Implementation Items and Results: Establishment of Access Route into PCV through X-6 Penetration (3/3)162) Connection of new boundary (2/2)(b) Design of the extension pipe
[Progress status]➢ From the perspective of better installability, a new idea of adding an extension pipe to the arm-type access device was broughtup. Mainly as a shielding measure against direct gamma ray from the X-6 penetration, an additional shielding function of theextension pipe is expected to reduce workers’ exposure to radiation.
➢ The functional requirements of the extension pipe were set (such as the boundary, shielding, and traveling function), thestructure was studied, and the feasibility was evaluated.
➢ The set structure concept has mostly satisfied the functional requirements. Further materialization of the structure needs to bepromoted from now on.

CameraFlange connection
mechanism

Isolation
valve
Extensionpipe

X-6 penetration
flangeArm enclosure

X-6
penetration

Arm

X-6 penetration
connection structure

Shielding plate

Traveling wheels©International Research Institute for Nuclear Decommissioning4.3 Implementation Items and Results: Establishment of Access Route into PCV through X-2 Penetration (1/3)

17[Progress status]
Methods applied to the process starting from installing a new boundary through installing a guide pipe in the environment isolated
from the PCV were studied, and the detailed design and prototyping of the relevant devices were performed. Then, in-plantverification was started.
(a) Scope of development of methods and devices used for establishing an access route through the X-2 penetration
New boundary
pointsArrange the area and remove
obstacles

P/A room

Isolated
sectionConnection of new
boundary

P/A room

AWJ device
P/A room

Isolated
sectionP/A room

Drilling a hole throughthe outer door of the
airlock

BoringmachineP/A room
Isolated
sectionGuide pipe

Drilling a hole through theinner door of the airlock,etc.

Insertion
jig

Support jig
Closurelids

Insert the guide pipe

Cable drum

Detailed
investigation

Seal box

P/A room

Development scope of methods and devices used forestablishing an access route©International Research Institute for Nuclear Decommissioning4.3 Implementation Items and Results: Establishment of Access Route into PCV through X-2 Penetration (2/3)18(b) Illustrations and photos of in-plant verification of a method for establishing an access route
through X-2 penetration (1/2)
Using the devices designed for establishing the access route from the X-2 penetration to the basement floor of the PCV in Unit 1,
the work conditions were examined, and the methods (devices, work guidelines) and on-site operations for each work step were
Confirmed in the in-plant verification.

Figure 4.3-1 (1/2) Illustrations and photos of in-plant verification tests for establishing access route©International Research Institute for Nuclear Decommissioning4.3 Implementation Items and Results: Establishment of Access Route into PCV through X-2 Penetration (3/3)19(b) Illustrations and photos of in-plant verification of a method for establishing an access route through X-2 penetration (2/2)

Borehole in the innerdoor

Figure 4.3-1 (2/2) Illustrations and photos of in-plant verification tests for establishing access route
The work conditions were examined, issues in methods (devices, work guidelines) and on-site operations for each work step were extracted, andtheir measures were studied. Aiming at on-site verification, a mock-up test and training will be performed in the future as a government R&D
project.
©International Research Institute for Nuclear Decommissioning

4.4 Implementation Items and Results: Access and Investigation Devices (1/5) 20(1) Narrowing down the access/investigation devices
Narrowed results of access/investigation devices

Housing box forvarious sensors

Image of accessinto the pedestal

Image of access to theexterior of the pedestal

Vertical-turning slide arm: 4.5 m
Grating cutter(hydraulicdriven)

Sonar installation
pointsUnit 1

Unit 2

Not feasible (Use of X-6 penetration)
Due to the high-radiation environment,dose reduction or remote hatch opening
technology needs to be developed, andalso preparation is necessary todevelop a new route inside the reactor
building. This method would entail hugecosts and is highly unlikely to meet thedeadline of method decision.

Feasible (Use of X-6 penetration)
At the current stage, the technicalfeasibility has been verified for theestablishment of an access route.
The study process needs to be
shortened in order to meet thedeadline of method decision.

Simulation of measurement area
(in the case of measurement outside thepedestal)

Grating cutting

Investigation unit
(1) Scanning
ultrasonicrange finder
(2)
(3)

γ
dosimeter
Camera1-2/4 Measurement offuel debris height (1)Identification of debris
boundary(1)(2)(3)

1-2/4 Fuel debris dispersion
1-4 Erosion area on the pedestal’souter wall
2-2 Area in the PCV shell where debris
has reached
Near X-2
penetration(Basement route)

Route into thepedestal

Basic route[Scope of the government R&D
project]
All the steps up to in-plant verification
tests toward the on-site verification
were completed.

Feasible (Use of X-2 penetration)
This method will enable the access tothe point near the penetration andpossibly meet the deadline of method
decision.
[Scope of the government R&D project]
All the steps up to in-plant verification tests
toward the on-site verification werecompleted.

-• The investigation plan
was materialized andupdated based on thelatest on-site situation,
etc.
• The development plancompatible with theinvestigation plan was
also materialized andupdated.
For Unit 3, the applicabilityof the devices developed
for Units 1 and 2 for the
purpose of using it in Unit 3
was reviewed, and thepresence/absence ofdevelopment issues wasclarified.

Example ofroute toward
the outer wall

Jig to prevent
cable interference©International Research Institute for Nuclear Decommissioning

4.4 Implementation Items and Results: Access and Investigation Devices (2/5)(2) Arm-type devices (1/2)
 Boom arm

Main specifications[Progress status] Designing the prototype of the actual device
has been completed and manufacturing is underway.
➢ The basic structure was determined based on the multi-joint
robot arm technology employed in the JET fusion reactor.
➢ An expandable interface that enables the replacement of asensor and tool as well as cable installation on the outer side of
the arm was established.

✓

Mountable sensor: 10 kg or less✓

Mounted tools: Cutting and grasping tool,
Water jet cutting tool✓

Pressing force: 400 N✓

Arm length: 22 m✓

Access range: Approx. 70% overall✓

Positioning accuracy: ±100 mm✓

Repetition accuracy: ±100 mm✓

Accumulated dose: 1 MGy✓

Accessories: Camera, Lighting➢ The strength evaluation of arm materials, the element test ofcables, and the radiation resistance test of major materials were
performed and the main specifications of the arm were finalized.

➢ Planned the rescue measures of
evacuating the unit into the enclosure incase of a malfunction, by using only asound motor and separating the wand, orforced retrieval using a winch.

21

Trolley

Boom

Telescopic arm

Tilt
mechanism

Biaxial
joint
Wand*

Sensor mounted at the arm tip* a tool can be mounted instead©International Research Institute for Nuclear Decommissioning

4.4 Implementation Items and Results: Access and Investigation Devices (3/5)(2) Arm-type devices (2/2)

22 Arm enclosure[Progress status] Designing the prototype of the actual device
has been completed and manufacturing is underway

✓
✓
✓
✓

➢ Determined the main dimensions considering aboutcarrying in and installing it together with the arm as wellas presence of obstacles✓✓

Main material: Stainless steel
Design pressure: -5 to +10 kPaG (negative pressure while
the arm is housed)
Leakage rate: 0.05 vol%/hOuter plate: 10-mm thickness; Bottom plate: 25-mm
thickness
Weight: Approx. 14 tons
Accessories: Dual-arm manipulator for maintenance,
Gate valve, Camera, Lighting, Dosimeter➢ Designed the structure to ensure the sealability andevaluated its strength and seismic resistance➢ Designed the arrangement inside the enclosure thathouses the arm and the dual-arm manipulator for
maintenance➢ Organized the interface with the outsidewhile considering about carrying in/out thesensors and tools after use
2m

8.8 m

Service panels➢ Designed accessories taking theiroperation into consideration, such as
installing a gate valve on the enclosure
2.4 m

Gate
valve

Exit port for highradiation materials
Back panel

Entrance/exit
port for materials©International Research Institute for Nuclear Decommissioning

4.4 Implementation Items and Results: Access and Investigation Devices (4/5)(3) Submersible-type device (1/2)

23[Progress status] For the submersible boat, which would be lowered from the X-2 penetration down to thebasement and capable to move and take measurements in the broad area in the basement, the design scheduled
for fiscal year 2017 was completed based on the updates made to the investigation plan, and preparation wasstarted for design verification. Additionally, in-plant verification test (function test) including test of the installation
device was started.
P/A room(1) Inserting into the PCV(5) Introducing the investigation device to the basement(2) Bending the head(6) Retrieving the device while washing it (after the investigation)(3) Positioning the head(7) Attaching a fall prevention pin(4) Inserting the head 1(8) Retrieval

Cable drum

Investigation
deviceIsolation
valve

Installation
device(a) Prepare for installation(b) Install the device(c) Install the guide rings or perform
investigation(d) Retrieve the device

View from below

Figure 4.4(3)-1 Illustrations and photos of in-plant verification tests of installation device©International Research Institute for Nuclear Decommissioning

4.4 Implementation Items and Results: Access and Investigation Devices (5/5) 24(3) Submersible-type device (2/2)(a) Prepare for installation

ROV for installing guide rings•
Diameter:  25 cm•
Length: Approx. 1.1 m•
Thrust: 25 N or greater(b) Install the device(c) Install the guide rings or perform
investigation(a) Approaching the jet
deflector

Mock-up jet deflector

Guide ring(d) Retrieve the device
On the basement walkway

Basic clockwise travel route

Guide ring 1-4(a) Prototype boat for installing the guide rings

1.9 m(Water level at the timeof the B2 investigation)

2.1 m(Highest water level
expected)

Guide ring

Enlarged view ofguide ring(b) Installing the guide ring

NeodymiummagnetGuide ring

Boat

Guide ring 2

Guide ring(c) Passing through theguide ring

Mock-up jet deflector

Guide ring 1

Guide ring

Guide ring 3
Neodymiummagnetb) Photos of the guide ring installation testc) Steps for installing the guide rings

A. Illustration of traveling method
B. Photos of tests for traveling the broad basement areain the broad basement area
Figure 4.4(3)-2 Illustration and photos of tests for traveling the broad area using the element prototype©International Research Institute for Nuclear Decommissioning

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (1/12) 25
List of measurement technologies[Progress status] Based on the update results of the investigation plan, the measurement technologies were partiallymodified and the full-scale prototype of the measurement systems was manufactured. The applicability verification isscheduled for FY2018.
Measurement technologies (Bluefont: subject to applicability verification;
Underlined: revised from the original plan)

Ultrasonic sonar*

Arm-type (Unit 2)

3D mapping of fuel debris, etc. ->3D mapping of deposits

Submersible-type (Unit 1)

3D mapping of structures, etc. in the atmosphereArm-type (Unit 2)

Measurement of deposit thickness(Confirm the substance under the deposit)

Submersible-type (Unit 1)

Impact elastic wave ->Low-frequency ultrasonicsensor(Revised)

Measurement of remaining thickness of thepedestal wall

- (Only the measurement
technology is to be developed
according to the investigation
after the deposits are collectedfrom Unit 1)

Camera using the water-mirror
approach (development
suspended)

Observation of the fuel debris form under thedeposit- (The development will beresumed if local removal of
deposit is necessary.)

Gamma camera

Distribution of gamma dose rate (confirmation offuel debris distribution)

Arm-type (Unit 2)

CdTe semiconductor detector ->CdTe semiconductor detector+ B-10 detector (additional)

Identification of fuel debris ->Identification of fuel debris inside and under thedeposit

Submersible-type (Unit 1)

Optical cutting method

Radiationmeasurement
technologies

Subject to the combination testwith the access device

3D mapping of underwater fuel debris, etc.

Scanning ultrasonic range
finderTechnologies
for measuring
shapes/dimensions

Purpose of measurement(Underlined: revised from the original plan)

High-power ultrasonic sensor(additional)

Research Institutefor Nuclear
Decommissioning*: These technologies are being studied based on the latest results of©International
the investigation
insidethe
PCV of
Unit 2 (A2’)

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (2/12) 26(1) Technologies for shape/dimension measurement (i) Ultrasonic sonar

•
•
•
•

Sources

The main specifications of the sonar were formulated and the design was carried out.
In order to satisfy the weight limit, the design to separate the sonar from the gamma
camera was adopted.
Detailed designs of the outer shell, internal arrangement, and rotation mechanism werecarried out.
The existing sonar that had a track record of use under radiation environment was resized to meet the arm design.
A radiation-resistant sealing material was selected, and it was confirmed that the pressure
resistance of the sealing in rotation mechanism as well as the operational characteristicsof the rotation mechanism was maintained under the radiation environment.
The rotation mechanism has a common design for the sonar and gamma camera.

Rotationmechanism

Sonar

Cumulative irradiation dose did not cause
variation in the operational characteristics.

Rotationmechanism

Results of the radiation
resistance test
Items
Results

8.1[min]

Rotation period [min]

•
•

6.8
[min]

0
kGy

Cumulative irradiation dose [Gy]

13.8
kGy

Operational characteristics test of the rotation mechanism under theradiation environment

Rotationmechanism

Radiation resistanceat a cumulative doseof 10 kGy wasconfirmed by the test
in fiscal year 2017.

Sonar

Resistance to a
cumulative dose of 75
kGy was confirmed bya conventional test.

©International Research Institute for Nuclear Decommissioning

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (3/12) 27(1) Technologies for shape/dimension measurement (ii) Scanning ultrasonic distance meter(1/2)[Progress status] The full-scale prototype of the measurement system for 3D mapping was manufactured, and the sensor performance is being
tested. The combination test with the access device is scheduled for FY2018.
Cross-sections viewed from three
directions - 1 (X:1 Y:1 Z:1)
X axisSensor center (X,Y) = (0,0)

Z axis

Y axis

Y axisInvestigation unit (with embedded sensors)• Scanning ultrasonicrange finder• Water temperature gauge

Z axisX axisAngle ofincidence 47°

Sensor appearance

Image from the front

Scanning
ultrasonic range
finderUltrasonicbeam

Z axisAnchorDepositElectronic
scanning

Mechanical scanning

Measurement principle

PC(Operation and data
recording)
Ultrasonic device

Image from theside

Image from the topi) Measurement condition:
Z = 1820 mmii) Dimensions of simulated falling
object (magnet):⌀ 18 mm  H 18 mmiii) Cable length:
60 m (same specification with theactual device)

Confirmed that all the simulated
fallen objects were successfully
detected within the range of up
to the incidence angle of 50
and the focused beams wereoverlapped(a) Unit test 1: Verification of measurement pitch

Control driver

Scanning ultrasonicrange finder

X axis
Y axisConfirmed that the simulated deposit was
visually observed within the range of up to theincidence angle of 50° (beam path length ofapprox. 3 m)

Simulated deposit surface(coated surface)

Scanning ultrasonicrange finder

Mechanicalscanning

Water tankwall surface

Simulated deposit
surface

Simulateddeposit surface

Water tankwall surface(b) Unit test 2: Detection range for deposit©International Research Institute for Nuclear Decommissioning

Figure 4.5(1)(ii)-1 Configuration of 3D mapping system

Figure 4.5(1)(ii)-2 Example of unit test for the scanning ultrasonicrange finder

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (4/12) 28(1) Technologies for shape/dimension measurement (ii) Scanning ultrasonic distance meter(2/2)
Table 4.5(1)(ii)-1 Current overview of unit test results

Confirmed results

Measurable
range
Measurement
accuracy

Distance

500-3000 mm

Angle of incidence

within  50°

Notes

Vertical:  50 mm*

Height: 1.2 mm (RMSE); Distance (vertical): 2.0 mm(RMSE)

Horizontal: 200 mm*

Distance (horizontal): 6.2 mm (RMSE)

Effect of turbid water*: Accuracy demanded by
the potential users of thistechnology

Attenuation of −0.01 dB/m in turbid water withvisibility of 6 cm

Table 4.5(1)(ii)-2 Progress status of unit test and combination test (excluding the combination test to be performed at the mock-up facility)
Types

Unit test

Test in a situation where the measurement
system and the sensor designed for theactual device as well as the cables having
the specifications used for the actual
device (no combination) are connected

Evaluation items

Progress status

Confirm the measurable range (distance and angle ofincidence)
Confirm the measurement accuracy (height, distance(vertical), position (horizontal))Completed(Table 4.5(1)(ii)-1)

Effect of turbid water
Confirm the 3D profile display

Combination
test

Test with a combination of themeasurement system, sensor, and ROV
designed for the actual environment andunder the operation conditions for themeasurement

Confirm the measurement accuracy (interval and distance(vertical))*(*: including the effect of the ROV’s posture)

FY2018

Effect of electronic noise©International Research Institute for Nuclear Decommissioning

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (5/12) 29(1) Technologies for shape/dimension measurement (iii) Optical cutting method (1/2)[Progress status] Based on the A2 and A2’ investigation results, the environmental conditions were reviewed, and applicability ofeach constituent element is currently being verified. The device design was initiated (the target achieved). In FY2018, a part ofapplicability verification, detailed design, manufacture of the actual device, and accuracy test are scheduled.

➢

Environmental conditions based on the A2 and A2’ investigation results

Previously, 34 cameras were required, but now only one camera is expected to suffice.
Yet, limitation on use of the radiation-resistant camera is to be inspected in the radiation
resistance test.

Camera• Revision (easing) of the environmental conditions based on the A2 and A2’
investigation results• Radiation resistance test of the MEMS mirror (with increased performance)• Review of the camera (performance increase: 1.2[kGy] -> 30[kGy] (estimate))

Items

Dose rate[Gy/h]

Revised environmental conditions
Outside pedestal
InsideAbove
Underpedestalgrating
grating

Conventional conditions
Outside pedestal
InsideAbove
Underpedestalgrating
grating

Measurem
ents

8

80

--

--

80

--

Predicted

30

300

300

1,000

300

300

Approx.
0.6

Approx.
16.8

Approx.
8.7

Approx.
15.7

Approx.
16.4

Approx.
8.2

By
Requiredlocationradiation
resistance
Total
[kGy]
Number of cameras
requiredAir blower
Scanner head
(MEMS mirror mounted)
Tool plate

Approx. 26.1

Approx. 40.3

1 (≈26.1÷30)

34 (≈40.3÷1.2)

Appearance of the shape/dimension
measurement device using the opticalcutting method

Note that 1[MGy], the requirement for the arm-type device, is also required for the cables and optical fiber to be mounted on the arm-type device.
©International Research Institute for Nuclear Decommissioning

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (6/12) 30(1) Technologies for shape/dimension measurement (iii) Optical cutting method (2/2)➢•

Applicability verification
Applicability verification of the MEMS mirror (radiation
resistance test)
Irradiation dose rate: approx.
5.9 [kGy]
Light sheet angle (deg)Control current (mA)

Cumulative dose
(kGy)

• Verification of the ability of multi-source image fusion
using pixel data obtained from different view angles
It was confirmed that multi-source image fusion was successfully doneby utilizing the position/orientation information. The accuracy
verification will be performed using an actual device to be
manufactured in FY2018.
Measurement frommultiple positions
and orientations

No effect on the accuracy at the cumulative dose of
1 (MGy) or higher

MeasurementtargetMeasured data

• Verification of water surface detection capability
Difficult to detect the water surface

Due to the penetration
characteristics of laser, nosignificant difference wasobtained between thesubmerged and non-submerged
measurement objects, indicatingthat the detection of water
surface is difficult.
Study and verification of othertechniques is to be performed in
FY2018.

Height (m)No submergence

Height (m)Multi-source
image fusion

Image obtained bymulti-source image fusion(color-coded by height)
Partially submerged (bottom half)©International Research Institute for Nuclear Decommissioning

Height (m)4.5 Implementation Items and Results: Applicability Verification of Element Technologies (7/12) 31(1) Technologies for shape/dimension measurement (iv) High-power ultrasonic sensor (for measurement of deposit
thickness) (1/2)[Progress status] Based on the analysis and preliminary test, the detailed design of the full-scale prototype of the deposit thickness
measuring system was completed and production was started. The combination tests with the access device are scheduled for
FY2018.
Investigation unit (with embedded
sensors)• High-power ultrasonic sensor• Preamplifier• Water temperature gauge *2

Within 17 cm
diameter
Within 15 cm height
Approx. 7 kg weight

Sensor(illustrative)

B scope was obtained by the ROV
investigation.

Sensor(Comb-shaped scanning in
the X-Y plane)

A: Surface of 300 mm-thick deposit
B: Surface of 100 mm-thick deposit,
and the top surface of two
structures laid out in a “V” shape.

Z (depth)

appearance
Movement

C: Bottom

High-power
ultrasonic sensor

B scope

Ultrasonicbeam

Since sound travels indeposit and water at adifferent speed*, aheight gap was formed
between B1 and B2 aswell as among C1, C2,
and C3.

Z (depth)

Deposit
FallenobjectDebris - MCCI

Measurement principle

Control unit
C scopePC(Signalprocessing
software)(a) Test method
The V shape of thetwo structures wascaptured in the image.

Surface of 300
mm-thick deposit
Power amplifier (3ch)

60 m

60 m

Preamplifier(3ch)(c) Example of B and C scope images

Surface of 100 mmthick deposit

Equivalent to
100 mmthickness

Sound speed in the deposit = Sound speed correction coefficient(dependent on the particle size) * Sound speed in water (1500 m/s)*

Equivalent to
300 mmthickness

Sound speed
correction
coefficient

High-power
ultrasonic sensor* The sound speed in the deposit is 1.1 - 1.2 times greater than that in water.

Standard
deviation 0.02

Annular array

Manufacturing
underway

approx.⌀ 170 mm

Figure 4.5(1)(iv)-1 Configuration ofdeposit thickness measurement
system(b) 3D visualization results of the whole area

Particle size [um]*: The sound speed in deposit depends also on the frequency, and there is a correlation between the soundspeed correction coefficient and the standardized particle size (particle size/wavelength).

(d) Correlation between the speed ofsound and the particle size of the deposit©International Research Institute for Nuclear Decommissioning

Figure 4.5(1)(iv)-1 Example of preliminary test results

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (8/12) 32(1) Technologies for shape/dimension measurement (iv) High-power ultrasonic sensor (for measurement of deposit
thickness) (2/2)
Manufacturing of the prototype sensor for the actual device is underway. The unit test is scheduled to start in around May FY2018
and the combination test in around September FY2018.
Table 4.5(1)(iv)-1 Plan for unit test and combination test (excluding the combination test to be performed at the mock-up facility)
Items

Evaluation items
Confirm the noise level
Basic
performance

Confirm the spatial resolution (vertical/horizontal direction)
Confirm the accuracy in measuring the deposit thickness

Preliminary
test / Unit
test

Test in a situation where themeasurement system, thesensor, and the preamplifier
designed applicable to the realenvironment or equivalents aswell as the cables having thespecifications used for theactual device are connected asa minimum requirement.

Radiation
resistanceConfirm the radiation resistance of the preamplifier (effect on the longevity andwaveform)and select the elements of the operational amplifier
Confirm the radiation resistance of the sensor (effect on the longevity and waveform)

Environmental factors

Effect of the material and particle size distribution of the deposit on the sound speed
and its attenuation
Effect of air bubbles contained in the deposit(that are attributed to radiolysis of water) on the sound speed and its attenuation
Effect of the sensor orientation on the deposit thickness measurement

Operational
factors

Effect of acoustic noise caused by the rotation of the thruster

Effect of electrical noise caused by the operation of the motor

Combination
test

Test with a combination of themeasurement system, sensor,
preamplifier, and ROV designed
for the actual environment andunder the operation conditions
for the measurement

Confirm the basic performance under the operational conditions of the actual device©International Research Institute for Nuclear Decommissioning

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (9/12) 33(1) Technologies for shape/dimension measurement (v) Low-frequency ultrasonic sensor (for measurement ofremaining thickness of the pedestal wall)[Progress status] The prototype sensor for measuring the remaining pedestal thickness was manufactured, and the unit test isunderway. A method to discriminate bottom echoes, which corresponds to the echo signal from the erosion boundary of the pedestal
wall, from those from concrete aggregates is being studied.
Concrete wall

60-m cable
Ultrasonic sensor
Frequency: 100 kHz
Transducer diameter: ⌀ 70 mm

TransmitterReceiverAggregate echo
Bottom echo

Double probe
technique*1
Flaw detector(pulser andreceiver)60-m cable

Preamplifier

Path length 600 mm
Control PC
Measurement system(Data recording and processing
designed for the actualunit)
device (Plan)
Specifications of the low-frequency ultrasonic sensor
Items

Candidate sensor 1

Candidate sensor 2

Candidate sensor 3

Frequency

100 kHz100 kHz30 kHzOuter
dimensions⌀ 80 × 60 mm⌀ 48  60 mm⌀ 80  80 mm

Transducer
diameter⌀ 70 mm⌀ 40 mm⌀ 70 mmObjectives

Basic specifications*2(same as those used
for the preliminary test)

Miniaturizationaccording to theactual unit
environment*3

Improved
identifiability ofbottom echo*4

Test results using concrete specimen• While the wall thickness can be measured if bottom echoes are successfully
discriminated among all received echo signals, it was revealed that the received
echoes include other echoes (from the aggregate, etc.) in addition to bottom echoes.
• Hence, a method to improve the identifiability of the bottom echo was studied.
Averaging waveforms• Improvement of the S/N ratio will befacilitated by averaging the
waveforms recorded at various
locations so that aggregate echoes(noise), each of which has a different
propagation distance will be offset,
and also by emphasizing bottom
echoes (signal) having a uniform
propagation distance.

*1: Because the dead zone was large when a probe (single probe) was used in the
preliminary test, the double probe technique is basically used for the actual device.

Bottom echo
TX
5-mm
interval*2: In order for the ultrasonic wave to penetrate the aggregate and reach the bottom, the wavelength needs to begreater than the aggregate size. Since the maximum size of the aggregate used for the pedestal in Unit 1 exceeds
20 mm, the desirable ultrasonic wavelength will be at least 40 mm, and the frequency will be set at 100 kHz or
below(the speed of sound in concrete at 4000 m/s).
*3: In the case of Unit 1, the deposit of a thickness of about 20 cm or greater exists on the floor of the exterior of thepedestal, and it is necessary to locally remove the deposit to install a sensor near the base of the outer pedestal
wall for scanning. Therefore, the miniaturization of the sensor is studied to keep the removal area minimum. A
transducer with a smaller diameter may result in reduced sensitivity.
*4: Although the measurement accuracy would be lower than that of the basic specifications, this sensor may be able
to achieve better identifiability of the bottom echo; therefore, it was added as a candidate and will be comparedwith the basic specifications during the selection.

Fixed transmission G9-G10 all_ave
Aggregate echoRX

Sensor scanning
method by means ofwaveform averaging
Path length 600 mm(example) ©International Research Institute for Nuclear Decommissioning• Improved S/N ratio is expected by reviewing the measurement conditions andaveraging the waveforms.

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (10/12)34(2) Radiation measurement technology (i) Gamma camera➢ The main specifications of the gamma camera were
defined.
➢ The design separated the sonar from the gamma
camera was adopted to satisfy the weight limit.
➢ Detailed designs of the outer shell, internalarrangement, and rotation mechanism were carried out.
➢ A silicon diode detector was employed.
➢ Variation in the DC offset was dealt with by modifying
the operational amplifier in the preamplifier.
➢ The test confirmed that the dynamic range of thedetector satisfied the required level.

Collimator

Items

Results

Rotationmechanism

Radiation resistance at 10 kGy
was confirmed by the test in
fiscal year 2017.

Gamma
cameraDynamic range of 1-1000 Gy/h
was confirmed fiscal year 2017.

0°

Image
conversion
processing

Rotation angle of thecollimator

Rotationmechanism

Results of the radiation resistance test

100°
0°

180°

Rotation angle of the rotation mechanism

Detector

Gamma camera

Based on the test measurement data at 1000 Gy/h, the image was converted to the dose data distinguished by irradiation direction.
By overlapping it with the image of the actual environment, it was confirmed that the source locations could be identified. (The sametest was also performed at 1 Gy/h.)Results of the dynamic range confirmation©International Research Institute for Nuclear Decommissioning

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (11/12)35(2) Radiation measurement technology (ii) CdTe semiconductor detector + B-10 detector (for fuel debris detection) (1/2)[Progress status] Based on the analysis and preliminary test, the full-scale prototype of the fuel debris detection system wasdesigned and manufactured, and the unit test was started. The combination tests with the access device are scheduled for FY2018.
Power supply/signal
processing unit

Prototype winch

Cs-137 source
Measurement period: 1 minute
Bias voltage: 750 V
Gross count rate: 1.2 kcps

Cable (60 m)

Investigation unit (sensor-drop type)• Cable drum (winch)• Debris detection sensor

Water-seal container
CdTe detector

Debris detection sensor

ShieldCdTe semiconductor
detector

Co-60 source

Measurement period: 5 minutes
Bias voltage: 750 V
Gross count rate: 0.3 kcps

γ-ray source(a) Example of unit test results for CdTe semiconductor detector

B-10 detector
CollimatorThreshold level ofanalog signal

Measurement device (outside
the irradiation chamber)

Ionizationchamber

Composite cableWinch

Co-60 γ-ray
sourceNeutron + γ-ray

Counts [/ch]Improved
small-sized B10 detector

Preamplifier

Measurement
period: 2 minutes
NeutronPower supply/signal processing unit
Electric noise

HDPE container

Eu-154 γ-ray detector

Thermal neutron detector
B-10 detector

Collimator*Illustrative image

Tungsten shield with a collimator, and water-seal container

Scope of prototyping for FY2017

Figure 4.5(2)(ii)-1 Configuration of
detection system for fuel debris
inside and under the deposit

Analysis settings

Depositthickness

90 cm

Area
dimension

200 cm × 200 cm

Composition

Concrete

Moisturecontent

64% (volume ratio)

Density

1.5 g/cm3

Result of γ-ray transport
calculation

Analysis point

Uniformly distributed in
the deposit

Atmosphere

Water

Burnup5 GWd/t

Detection limit (approximate)
Uranium concentrationin the deposit sample

DepositResult of neutron transport
calculation

Sourcelocation

γ-ray count rate [cps]

CdTe semiconductor
detector(b) Example of unit test results for B-10 detector
Items

Analysis point
Deposit

Uranium concentration (wt%)
Thermal neutron
count rate [cps]ShieldPeak [channel]

Electric noise

Detection limit (approximate)
Uranium concentrationin the deposit sample

Uranium concentration (wt%)

Variation of count rate with the concentration of
uranium in the 90-cm-thick deposit(c) Example of detection limit study by analysis (Uranium equivalent: 5 GWd/t)©International Research Institute for Nuclear Decommissioning

Figure 4.5(2)(ii)-2 Example results of unit test and analysis of fuel debris detection system

4.5 Implementation Items and Results: Applicability Verification of Element Technologies (12/12)36(2) Radiation measurement technology (ii) CdTe semiconductor detector + B-10 detector (for fuel debris detection) (2/2)
Table 4.5(2)(ii)-1 Progress status of unit test and combination test (excluding the combination test to be performed at the mock-up facility)
Subjects
Unit test

CdTe
semiconductor
detector(incl. shield)

Items

Details

Progress

Connection check

Response measurement using a 60-m cableCompleted

Polarization effectUsing the measurement time as a parameter, measure the fluctuation of the full width at half
maximum and the peak position

Completed

Bias power control

Evaluate the method of controlling the bias power on/off for the reduction of polarization effectUndoneDetection efficiency

Response measurement using Eu-154, Cs-137, and Co-60 point sources, and the calculation of
detection efficiency

UndoneShield/collimator effectResponse measurement using Cs-137 and Co-60 point sources, and the calculation of detection
efficiency

UndoneOperational check underhigh radiation

Response measurement in a Co-60 irradiation chamber

UndoneConnection check

Response measurement using a 60-m cableCompleted

Operational check underhigh radiation

Neutron response measurement in a Co-60 irradiation chamber

Completed

Detection efficiency

Response measurement using a thermal neutron field

UndoneSystem operation check

Operational check by connecting each device (including the confirmation on the results ofimprovement)

Completed

Confirm on noise effectConfirm the effect of electrical noise during measurements (including the confirmation on the resultsof improvement)

UndoneIrradiation testwith mixed radiation sources

Response check under thepresence of Cs-137 in
water

Using a spent fuel assembly (max 70 Gy/h), Confirm the measurability of Eu-154 and neutron inwater.

UndoneCombination test

Confirm on electrical noise
effectMounting the improved small-sized B-10 detector on the ROV, evaluate the noise effect under theoperating conditions of the ROV during measurements.

UndoneB-10
detector

Combination test
using a water-seal container©International Research Institute for Nuclear Decommissioning37

4.5 Implementation Items and Results: Mock-up Test Plan
[Progress status]➢ To increase the reliability of the detailed investigation through the development of access/investigation
devices, the verification of the arm-type access device has been planned in a mock-up test using a test
facility that partly simulates the actual reactor structure.
➢ The mock-up test items were extracted and the outlines of the test content and test facility were reviewed.
➢ In the future, the test facility needs to be materialized as well as brushing up the test items and content.

Selected the test items based on the investigation
findings

Installation of investigation device

Removal of obstacles in X-6 penetration

Exchange of work tool/sensor,
etc. in the enclosure

Cutting the CRD rail

Cables, CRD rail, etc.

Reviewed the outlines of the test content and facility

Removal of obstacles in PCV
Grating, etc.

Cutting the grating

Access andinvestigation
devices

Installing the tip tool(inside the enclosure)
Investigation inside PCV using sensors

Scanning by a gamma sensor

Flow of the Detailed Investigation

Mock-up
PCV
Conceptual diagram of a test facility©International Research Institute for Nuclear Decommissioning5. Overall Summary

38(1) Formulation of investigation plan and development plan
• Based on the latest results of the Detailed Investigation in Units 1 and 3, whose damages are assumed to be significant, theapproach of the investigation toward the fuel debris retrieval was studied, and the investigation plan and development plan forthe detailed investigation in Unit 1 was updated.
• Based on the latest results of the Detailed Investigation of Unit 2 (A2’), the investigation plan and development plan for the
Detailed Investigation in Unit 2 is being updated.
(2) Establishment of access route(a) Establishment of access route into PCV through X-6 penetration• A part of in-plant verification (combination tests) of full-scale prototypes of the isolated room, hatch opening mechanism, etc.
were completed, and the design of the full-scale prototype of the penetration connection was completed. in-plant verification isplanned in the future.
• The design of the new boundary connection was completed and the conceptual study of the extension pipe is being
performed.
(b) Establishment of access route into PCV through X-2 penetration
Methods concerning the connection of a new boundary, the boring of the inner and outer door, etc. of the X-2 penetration, andthe installation of a guide pipe, all of which need to be implemented while the isolation from the PCV is maintained, were studied;the design and production of full-scale prototypes of devices for aforementioned work were performed; and in-plant verification
was started.
(3) Access and investigation devices• The full-scale prototype of the arm-type access device is being manufactured.
• The design work assigned in fiscal year 2017 for the full-scale prototype of the submersible-type access device was performed
according to the original plan and the preparation for design verification was started. Also, a part of the in-plant verification of
the installation devices was performed.
(4) Applicability verification of element technologies• The production of the full-scale prototype of the measurement system and unit performance tests were started.
• The verification of the substitute of a measurement device using laser-based optical cutting method applicable in atmospherewas performed. Only the radiation resistance test of the radiation-resistant camera is planned in FY2018.
• The applicability of element technologies are planned to be verified in FY2018 through combination tests with the accessdevice, etc.
(5) Mock-up test plan
©International Research Institute for Nuclear Decommissioning
Outlines of the mock-up test facility are being studied.