ReferenceJanuary 30, 2017

Tokyo Electric Power Company Holdings, Inc.

Pre-investigation results of the area inside the pedestal for the Unit 2 Primary Containment Vessel Investigation at Fukushima Daiichi Nuclear Power Station

1

The purpose of this investigation is to inspect the platform inside the pedestal, fuel debris fallen to the Control Rod Drive (CRD), and structures inside the pedestal.Today, preparatory investigation was conducted for X-6 penetration and CRD exchange rail which the self-propelled Scorpion robot will take to the pedestal.

1. Unit 2 Primary Containment Vessel investigation

Investigation area inside the pedestal

ＲＰＶ

X-6 penetration

Primary Containment Vessel (PCV)

Control Rod Drive (CRD) exchange rail

Pedestal openingPedestal

Platform

Control Rod Drive (CRD)

Basement floor

Today’s investigation area

About 7.2m

2

Step 1. Drilling device carried in Step 3. Drilling on X-6 penetration

Step 7. Investigation using self-propelled investigation device

Step 5. Pre-investigation inside pedestal using guide pipe

X-6 penetrationDrilling device Hole sawIsolation unit*

Drilling device X-6 penetrationIsolationDrilling device

X-6 penetrationShielding

Step 2. Drilling device set up

Self-propelled investigation device

*Combination of isolation and shielding

Clamp

Step 6. Obstacle removal device inserted*

Obstacle removal devicePan-tilt

camera

Step 4. Pre-investigation of X-6 penetration and CRD rail using guide pipe

Pan-tilt camera

X-6 penetration

CRD railX-6 penetration

CRD rail

Pedestal

*The device may not be inserted depending on the obstacle conditions.

3. Work steps for Unit 2 PCV investigation

3

自走式調査装置による調査概要

CRD rail Lifting balance Pedestal opening

Pedestal wall

Shooting range

Platform

Alternative shieldingControl Rod Drive (CRD)

Isolation valve Guide pipe (Φ110mm)

Pedestal

Inside of Primary Containment Vessel

X-6 penetration

Pan-tilt camera and lightsStep 4

3-1. Pre-investigation results for the area inside the pedestal

4

パンチルトカメラ・照明

天

TIP guiding pipe

CRD rail and platform opening

Flat bar

On the side of platform

No grating

Flat bar

No grating

Deposits

CRD bottom

3-2. Pre-investigation results for the area inside the pedestal

5

The pre-investigation was conducted as planned. In the pre-investigated area,• No changes in positions of Control Rod Drive (CRD) housing, Position

Indication Probe (PIP) cable, and CRD exchanger• A part of the grating deformed • Some deposits on the CRD rail and grating found • Water dripping found in some areas Visual images obtained through this pre-investigation will be analyzed to

determine whether a rubble removal device and a self-propelled investigation robot can be inserted.

The Unit 2 PCV is stably cooled because no abnormalities in reactor core cooling have been found in PCV/RPV temperatures and plant parameters such as parameters related gases inside the PCV.

No leakage has been found to the outside of PCV because air tightness is secured by using isolation valve and O-ring during the pre-investigation work and the area around the O-ring is pressurized more than the pressure inside the PCV.

No external impacts have been found from the radiation doses inside the PCV because they are appropriately managed by buildings and shielding.

4. Summary

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Remote operation room in the main administrative office

Inside the Unit 2 Reactor Building

Reference: Work site scenes

The pre-investigation was conducted by remotely operating the camera in the remote operation room and by inserting/pulling out the guide pipe at the field headquarters and inside the Unit 2 Reactor Building.

Work site scenes