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Measure to solve technical subjects in MARICO-2 subassembly retrieval
Experimental Fast Reactor Joyo Oarai R&D Center, JAEA
1
Hold-down shaft
App
rox.
90m
m
Results of in-vessel observation
Status of MARICO-2 test subassembly (S/A)
MARICO-2 Holding
Mechanism UCS In-vessel
storage rack
core MARICO-2 S/A
Reactor Vessel
Rotating Plug Hold-down shaft
Approx. 200mm
Transfer pot
R-16 R-15
Bent MARICO-2 S/A
UCS
MARICO-2 S/A
Hold-down shaft
Image of in-vessel Transfer pot
2
3 State of
MARICO-2(S/A) Normal state
Transfer pot
Test S/A
Status of MARICO-2 test subassembly (S/A)
A handling head has come out from S/A. S/A cannot be gripped by the ordinary refueling machine.
The length of the bent part of S/A is more than 200 mm. It cannot pass through the fuel exchange hole.
The bent S/A is losing its balance.
A degree of mechanical interaction between S/A and the transfer pot should be taken into consideration in the design of a retrieval device.
Development of gripper mechanism for retrieving
MARICO-2 S/A
4
Development of gripper mechanism
2nd Plan Gripping pot and retrieving together
S/A is bent onto the in-vessel storage rack
possible possible
impossible impossible
impossible possible
3rd Plan Gripping both of pot and S/A Retrieving together
1st Plan Gripping & retrieving S/A singly
5
Inspection hole(A) Rotating Plug
Handle
Preliminary in-vessel test(1) MARICO-2 S/A lift-up test
to grip and lift up the transfer pot is required. MARICO-2 S/A
(Dummy)
Transfer pot (Dummy)
Two Claws Type Gripper
MARICO-2 S/A
Gripper
Lift-up equipment
Transfer pot
It is confirmed that MARICO-2 S/A is stuck in transfer pot owing to its deformation. Equipment to retrieve MARICO-2 S/A together with transfer pot is required.
Two Claws Type Gripper
6
The observed gap between MARICO-2 S/A and a pot is narrow. It was uncertain whether a single hook type gripper could insert.
Expected Space which can insert
a single hook (30mm X 30mm)
Estimated outline of S/A
Inner diameter of opening of a
transfer pot (107mmφ)
Image of Single hook type gripper
(Latch finger)
Gripping position of transfer pot and gripper structure
Na level 7
Dummy S/A
Latch finger
Dummy transfer pot
Transfer pot
70mm
MARICO-2 S/A
Insertion of latch finger
UCS Hold-down shaft
Fiberscope
Latch finger
Latch finger
Latch finger
MARICO-2 S/A
Lifting up MARICO-2 S/A
MARICO-2 S/A
Latch finger
Preliminary in-vessel test(2) Preliminary in-vessel test was conducted to demonstrate latch finger performance.
8
Decision of gripper mechanism
2nd Plan Gripping pot and retrieving together
S/A is bent onto the in-vessel storage rack
possible possible
impossible impossible
impossible possible
3rd Plan Gripping both of pot and S/A Retrieving together
1st Plan Gripping & retrieving S/A singly
Preliminary in-vessel tests show; - Detachment of S/A from pot is impossible
- Grip and Lift of transfer pot are possible by the latch finger
9
Latch finger
Wire rope
Latch finger MARICO-2 S/A
Transfer pot
Design point - Shape of latch finger is based on the fuel exchange machine which handles transfer pot normally
- Single latch finger is improved its reliability through changing to the higher strength material. Outline of gripper mechanism
Basic structure of gripper mechanism
Pot supporting nose
Spring
10
Access to MARICO-2 S/A position
11
UCS
Large R/P
Small R/P
In-vessel inspection hole (B)
(Φ110mm)
Fuel handling hole (φ164mm) (Largest route in existing penetration holes)
MARICO-2 In-vessel
inspection hole (A) (Φ110mm)
The retrieval device employs “offset configuration”
1m
App
rox.
90
mm
UCS cannot be positioned right above MARICO-2 to avoid a contact with it.
App
rox.
70
mm
Transfer pot
MARICO-2
Approx. 200mm
MARICO-2 UCS
Access route to retrieve MARICO-2 is UCS hole (1m) by geometric size
Access route for retrieval Geometric condition
The length of bent part of MARICO-2 S/A > 200mm
12
2) Avoiding the in-vessel thermal insulating plate by folding upper arm
1) Extending arms to right above position of MARICO-2 and lift up the pot
3) pulling up to diagonally upward
Pantograph mechanism and manner of retrieving
Offset
Thermal insulating
plate
A hole where the UCS was extracted
Upper arm
Lower arm
Ex-vessel test
Movement of each component such a hoist mechanism and a pantograph mechanism were carefully checked by ex-vessel test.
4) Folding lower arm and Storing MARICO-2 to a guide sleeve
13
Image of MARICO-2 retrieval
14
Guide tube
1) Failure in gripping operation 1) In-vessel observation
Design for reliable gripper mechanism
Front view Side view Transfer
pot
Gripper mechanism
3.2)Lock pin
3.1) Lock lever 4) Break of hoist wire
Guide rail
3) Trip of latch finger
Causes of failure Measures
1) Failure in gripping operation
1) In-vessel observation device is prepared to monitor the gripping operation.
2) Break of latch finger
2) Enough strength material which has 7 times strength of the maximum stress.
3) Trip of latch finger
3.1) Lock lever When pot is lifted up by hoist wire, the lock lever makes grip tight by weight of pot 3.2) Lock pin When pot is lifted to upper position, lock pin is push on lock lever.
4) Break of hoist wire
4.1) Enough strength wire which has 13 times strength of the maximum stress. 4.2) Backup by wire operating latch finger which is designed as same diameter with the hoist wire.
2) Break of latch finger
4.2) Backup by wire operating latch finger
4.1) Enough strength wire
2) Enough strength material
15
Maintain of boundary of MARICO-2 retrieval device
16
Main boundary is formed by steel wall.
Manual handles in the boundary is needed to stretch the pantograph.
Install of Glove box Upper guide sleeve and bellows
(Steel boundary)
Handles to stretch Pantograph mechanism
Hoist handle
Boundary structure of MARICO-2 retrieval device
Lower guide sleeve (Steel glove box)
17
Argon gas blow-down
Working pressure range : 150+50Pa
(Design pressure: 1000Pa)
In-vessel Argon cover gas
Ventilation of Argon
Small R/P
Open and Close dependent on
situation
Lid
Polycarbonate window
Glove port cover (to close port when glove is not used)
Main boundary is formed by steel wall.
A steel lid is installed to shut convection of Ar cover gas.
By appropriate Argon gas blow-down, convection of Ar cover gas is prevented.
Safety measures for work in glove box Upper guide sleeve
(Steel boundary)
Glove
Lower guide sleeve (Steel glove box)
18
Measure for unexpected incident - Safety measures against falling accident of transfer pot - Provision for unexpected incident in MARICO-2 retrieval work
19
In lifting operation Roller rides up along the wedge of in mobile space in housing.
In falling accident Roller slips down along the wedge and constrict the pot.
Unlocking The stopper is unlocked by a lift of the cotter.
Large dia. Small dia. Unlocking
Shock absorber at bottom
(1) Stopper mechanism of falling pot Safety measures against falling of transfer pot
(2) Shock absorber
Cotter Wedge Roller
20
Provision for unexpected incident in MARICO-2 retrieval work
Return of the pot to the initial position
Investigation of incident and its cause
Measure based on the cause analysis
Unexpected incident
Preparation of operation manual including the initial response in unexpected incident Full mockup test in manufacturer’s factory - Confirmation of operation procedures including return to initial position - Careful checking and revising manual - Training of operators
Retry
Fiberscope type observation device monitors and records in-vessel status during retrieval work Preparation of the inspection work area The equipment pit is available as inspection area in the reactor containment vessel
21