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

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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

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