ReferenceFebruary 2, 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(examination results of digital images)

Tokyo Electric Power Company Holdings, Inc.

1Cross section of Reactor Building

Primary Containment Vessel (PCV) dry well

Nuclear fuel in the Primary Containment vessel (PCV) was exposed to the air and melted from the impact of March 2011 Great Earthquake.

As a result of the accident analysis, it was found that a portion of melted nuclear fuel might have been fallen inside the pedestal.

Spent Fuel Pool

Suppression Chamber(S/C)

Reactor Pressure Vessel(RPV)

Pedestal

Cross section of the bottom ofPrimary Containment Vessel

Expanded

Reactor Pressure Vessel (RPV)

Pedestal

Control rod drive (CRD) exchange rail

X-6 penetration

To remove fuel debris, it is necessary to investigate the PCV and clarify the conditions of debris and surrounding structures.

Platform

Possibility of fuel debris falling

Reactor Building

8.5m

Hei

ght a

bout

33m

Diameter about 20m

1. Current conditions of Unit 2 Primary Containment Vessel (PCV)

Primary Containment Vessel (PCV) dry well

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.

2. 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

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

4

Deformed grating

CRD housing support

LPRM cable or PIP cable

CRD exchanger

Flat barDeposits possibly adhered to TIP guiding pipe support

End of CRD rail

Reference: the inside of Unit 5 pedestal

LPRM (Local Power Range Monitor) measures flux levels of neutron inside the reactor core.TIP (Traversing In-Core Probe System) proofs LPRM.PIP (Position Indicator Probe) detects positions of Control Rods.

Reference: the inside of Unit 2 pedestal during regular inspection

TIP guiding pipe support

4-1. Pre-investigation results for the area inside the pedestal(examination results of digital images)

5Flat bar

Slot openingDeformed grating

4-2. Pre-investigation results for the area inside the pedestal(examination results of digital images)

Reference: the inside of Unit 5 pedestal

The investigation was originally to be conducted using the above routes. However, because of some deformed grating found this time, it has been examined whether the self-propelled investigation robot can be inserted.

CRDレール

Sunken area

5. Expected investigation routes for the self-propelled Scorpion robot

Platform

CRD rail

7

To determine whether the obstacle removal robot and the self-propelled investigation robot can be inserted inside the pedestal, we examined digital images obtained from the pre-investigation conducted on January 30 and found detailed conditions inside the pedestal. Some deposits possibly adhered to TIP guiding pipe support A part of the grating sunken in at the center of the pedestal

Based of the conditions inside the pedestal found this time, we will proceed with the examination on whether to insert the obstacle removal robot and the self-propelled investigation robot.

6. Summary