Unit 2 Primary Containment Vessel Investigation at Fukushima Daiichi Nuclear Power Station

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Reference February 16, 2017 Tokyo Electric Power Company Holdings, Inc.

Unit 2 Primary Containment Vessel Investigation at Fukushima Daiichi Nuclear Power Station

(Investigation results by the self-propelled investigation device)

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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 penetration Drilling device Hole saw

Isolation unit^*

Drilling device X-6 penetration Isolation

Drilling device

X-6 penetration Shielding

Step 2. Drilling device set up

Self-propelled investigation device

*Combination of isolation and shielding Clamp

Step 6. Obstacle removal device inserted^*

Deposit removal device Pan-tilt

camera Step 4. Pre-

investigation of X-6 penetration and CRD rail using guide pipe

Pan-tilt camera X-6 penetration

CRD rail

X-6 penetration CRD rail

Pedestal

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

1. Work steps for Unit 2 PCV investigation

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自走式調査装置による調査概要

Investigation by the self-propelled investigation device

Pedestal opening Hanging

balance

画像提供：国際廃炉研究開発機構(IRID)

Step 7

2. Investigation results by the self-propelled investigation device (digital images)

Shooting range

Platform Alternative

shielding

Control Rod Drive (CRD) Pedestal

Inside of PCV X-6 penetration Isolation

valve Isolation

valve

Chamber unit

Guide pipe for pre-investigation

(Φ110mm)

Self-propelled investigation device (cameras, dosimeter, thermometer)

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About 210Sv/h^*

16.5℃ Dose rate

Temperature

*・Calculated from integrating radiation dose for about four minutes.

・Estimated value from noise images: about 5-13Sv/h Note) Could be affected by the lighting

Temperatures have been evaluated from the sequentially obtained data.

Reference: temperature inside the PCV:

18.6℃ (as of 8:00 a.m.) TE-16-114C

2. Investigation results by the self-propelled investigation device (temperatures and radiation levels)

Step 7

shielding Control Rod Drive (CRD)

Pedestal

valve Isolation

valve

Chamber unit

(Φ110mm)

Investigation by the self-propelled investigation device

Control Rod Drive (CRD)

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 Today’s investigation results

• The self-propelled investigation device ran on the deposits of the CRD rail and reached the area toward the pedestal (the vicinity of hanging balance), further than the area where the deposit removal device reached.

• It tried to move further toward the pedestal but could not reach there because the crawler belt on the left side could not move any more.

• It investigated temperatures and radiation levels on the CRD rail as well as conditions of surrounding structures.

• The connection cable was cut and the device was left on the side of the CRD rail not to obstruct further investigations.

 Plans for further examination

TEPCO will continue to evaluate the information, such as deposits on the CRD rail and conditions inside the pedestal, obtained from this entire

investigation.

4. Summary

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Guiding pipe slope

CRD rail

End of CRD rail

Investigation by the self-propelled investigation device Step 7

Shooting range

shielding

Control Rod Drive (CRD) Pedestal

valve Isolation

valve

Chamber unit

(Φ110mm)

Self-propelled investigation device (cameras, dosimeter, thermometer)

Images provided from International Research Institute

for Nuclear Decommissioning (IRID) Location where the device was left

Reference: Location where the device was left