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<Reference>
“Development of a technology to investigate inside
the Reactor Primary Containment Vessel (PCV)”
-- Site test “Investigation B1” on grating around
the pedestal inside Unit 1 PCV [For April 10]
April 13, 2015
Tokyo Electric Power Company
The content of this material includes the output of the International Research Institute for Nuclear Decommissioning (IRID)
1. Investigation overview
Purpose: For Unit 1, conducting an investigation in order to collect information on “the 1st floor grating
inside the Primary Containment Vessel (PCV)” from the robot inserted through X-100B penetration pipe.
CRD rail
: Access route (counterclockwise)
: Access route (clockwise)
HVH
MS pipe
B0, ～ B18, Counterclockwise route
～
C11, Clockwise route
C0,
B17,
B16,
Access points (Planned)
B18,
Pedestal Opening
B15,
C11,
B14,
Investigation device
C10,
B13,
C9,
B12,
C8,
B11,
PLR pump
C7,
B9,
C6,
B10,
PLR pipe
C5,
(Conducted on April 10)
B8,
B5,
C4,
B3,
C3,
HVH
Counterclockwise
access route
B4,
B7,
B6,
C2,
B1,
B2,
C1,
C0,
B0,
X-100B
Opening to
access
Basement
floor
1
2. Access route (performance result)
 The investigation was conducted taking on a different route as some objects were
found to be fallen on the original access route planned.
 The robot was stuck on the route between B14 and B15.
B17,
B16,
B18,
B15,
Approx. 20 mm
Where the
robot stuck
B14,
B13,
Approx. 20 mm
B12,
B11,
B9,
B8,
B5,
Approx. 20 mm
B3,
Original route
B10,
B1,
B0,
B4,
B7,
B6,
B2,
Actual investigation route
Fallen objects
X100B penetration pipe
Approx. 20 mm
2
3. Investigation results
The following information were obtained for items ① to ③ of this investigation.
CRD rail
No.
Location
Investigation results
①
Opening to
access
basement
floors
・B2 investigation* will be conducted next time.
TEPCO confirmed there is an opening accessible to
the basement as well as no obstacles around it.
HVH
HVH
Pedestal
Opening
B14,
B13,
PLR pump
B12,
B11,
Opening to access
basement floors
B9,
PLR pipe
B10,
B8,
HVH
B3,
B1,
B2,
B0,
X-100B
Penetration
pipe
B4,
B5,
B7,
B6,
②
CRD rail
・Yet to be reached at CRD rail.
・Images have been taken with a camera facing
towards CRD rail from the place where the robot
reached at, which is now under evaluation.
・No significant damages were found on the
existing facilities. (such as HVG, PLR pipe, the wall
On the access of Pedestal)
③
route
・Information on the temperature and radiation
levels has been obtained at each investigation point.
* B2 investigation: Investigation on basement floor excluding the pedestal.
3
4-1. Images (Opening to access the basement)
B４
With B2 investigation to be conducted next time, TEPCO confirmed
there is an opening accessible to the basement as well as no obstacles
around it.
HVH
HVH
Pedestal
Opening
B14,
B13,
PLR pump
B12,
B11,
Opening to access
Basement floor
B9,
PLR Pipe
Approx. 50 mm
B10,
B8,
HVH
B3,
B1,
B4,
B2,
B0,
X-100B
Penetration pipe
B5,
B7,
B6,
Spot where the robot can
be inserted.
Appri. 20 mm
4
4-2. Images (PLR pipe)
B7
・No significant damages were found on the PLP pipe (for
heat retention).
・It was found that a part of the shield has been fallen off.
HVH
HVH
PLR pipe
Pedestal
Opening
B14,
B13,
PLR pump
B12,
B11,
B9,
PLR pipe
B10,
B8,
HVH
B3,
B1,
B4,
B2,
B5,
B7,
B6,
B0,
Approx. 20 mm
X-100B
Penetration pipe
5
4-3. Images (Equipment hatch and exterior of pedestal)
B３
Exterior of the outer wall of the pedestal
No significant damages were found on the outer wall of the
pedestal.
Outer wall of the pedestal
HVH
HVH
Pedestal
Opening
B14,
B13,
PLR pump
B12,
B11,
B9,
PLR pipe
B10,
B2
Exterior of the equipment hatch.
No significant damages were found on the equipment
hatch.
B8,
HVH
B3,
B1,
B4,
B2,
B5,
B7,
B6,
B0,
X-100B
Penetration pipe
6
4-4. Images (HVH (D) )
B1
HVH
No significant damages were found on HVH (D).
HVH
Pedestal
Opening
HVH（In the center at the bottom)
HVH（At the edge of the bottom)
B14,
B13,
PLR Pump
B12,
B11,
B9,
PLR pipe
B10,
Approx. 20 mm
Approx. 20 mm
B8,
HVH
B3,
B1,
B4,
B2,
B5,
B7,
B6,
B0,
X-100B
Penetration pipe
7
5. Investigation results (Temperature/ dose rate)
Temperature and dose rate were measured at the following points.
HVH
HVH
Pedestal
Opening
B14,
B13,
PLR pump
B12,
B11,
B9,
PLR pipe
B10,
B8,
HVH
B3,
B1,
B2,
B4,
B5,
B7,
B6,
B3
B4
B5
B7
B11
B14
Dose rate
（Sv/h）
Temperature
（℃）
7.4
7.5
8.7
7.4
9.7
7.0
17.8
19.2
19.4
19.5
19.2
20.2
B0,
X-100B
Penetration
pipe
8
6. Investigation robot stuck on route
 Object was found to be fallen on the planned route between B 14 and B 15
where was the narrowest part of it.
 Following the procedures, the investigation continued by choosing an another
route avoidable the objects.
 After that, although the robot stuck at a narrow point, it captured some images
facing to the direction of CRD rail. (currently the images are under evaluation)
Possible cause and measures:
Fallen
object
B15,
Existing pipe
Where the
robot stuck
★
B14,
Original route planned
Actual investigation route
The robot got stuck with an existing
pipe and some shut parts of the grating
or uneven part at the joint, which
resulted in making the route hard to
run on.
Measures to be taken are under study.
9
7. Schedule
 Dose rates were obtained below 10 Sv/h.
 A knowlege was obtained that with the same amount of dose rates in “investigation on clockwise
route”, the investigation camera which installed into the robot could tolerate two or three days without
any problems .
As for the case of an investigation on clockwise route, the plan is currently reviewed based on the
knowledge obtained above.
April 2015
1. Investigation on counterclockwise
route
１０
１１
１２
１３
１４
１５
１６
１７
Fri
Sat
Sun
Mon
Tue
Wed
Thu
Fri
Investigation
Robot collection review
2. Investigation on clockwise route
Under examination for the
implementation period for the
investigation on clockwise route.
10
Reference: Mock-up
Spot where the robot stuck
11
Reference: Mock-up
CRD rail
Spot where the robot stuck
12