pre-investigation results of the area inside the pedestal … rail which the self-propelled scorpion...
TRANSCRIPT
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
6
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