Reference January 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
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 opening Pedestal
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 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*
Obstacle 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.
3. Work steps for Unit 2 PCV investigation
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 shielding
Control Rod Drive (CRD) Isolation valve Guide pipe
(Φ110mm)
Pedestal
Inside of Primary Containment Vessel X-6 penetration
Pan-tilt camera and lights
Step 4
3-1. Pre-investigation results for the area inside the pedestal
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
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
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
