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All OTs.. OT11(1)
Occasional Topics
OT11(1) (2010-5-7)
 
- Special Issue on ITER (1) -
Overview of Remote Maintenance for ITER Blanket
 
Nobukazu TAKEDA
ITER Tokamak Device Group, ITER Project Unit
Fusion Research and Development Directorate
Japan Atomic Energy Agency
 
KEYWORDS:
ITER, fusion, remote handling, manipulator, blanket
 

Full Download( PDF)
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  1. Overview of Remote Maintenance for ITER Blanket
N. Takeda
ITER Tokamak Device Group
ITER Project Unit
Fusion Research and Development Directorate
Japan Atomic Energy Agency
February 2010
  2. ITER Project: Way to Fusion Energy
  Programmatic Objectives
To demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes
Main Parameters
  3. ITER: An International Project
  Members of ITER Project:
  »Japan
  »European Union
  »Russia
  »United States
  »China
  »Korea
  »India
The members established an international organization (ITER organization) to operate the ITER project.
  4. ITER Technical Objectives [1]
  Plasma Performance
●The ITER device should achieve extended burn in inductively driven plasmas with the ratio of fusion power to auxiliary heating power, Q, of at least 10 (Q ≥ 10) for a range of operating scenarios and with a duration sufficient to achieve stationary conditions on the timescales characteristic of plasma processes.
●The device should aim at demonstrating steady-state operation using non-inductive current drive with the ratio of fusion power to input power for current drive of at least 5.
●In addition, the possibility of controlled ignition should not be precluded.

Engineering Performance and Testing
● The device should demonstrate the availability and integration of technologies essential for a fusion reactor (such as superconducting magnets and remote maintenance).
● The device should test components for a future reactor (such as systems to exhaust power and particles from the plasma).
● The device should test tritium breeding module concepts that would lead in a future reactor to tritium self-sufficiency, the extraction of high grade heat and electricity production.
  5. ITER Remote Handling Classification [2]
  Case 1
those components that require scheduled remote maintenance or replacement.

Class 2
those components that do not require scheduled but are likely to require unscheduled or very infrequent remote maintenance.

Class 3
those components not expected to require remote maintenance during the life time of ITER. The projected maintenance time in case of failure may be long.
  6. Two Major Components for Remote Handling (RH) [2]
  Blanket (green)
●removes the surface heat flux and the nuclear heating within the allowable temperature and stress limits, while minimising the impurity influx to the plasma;
●reduces the nuclear responses in the vacuum vessel structural material for the ITER fluence goal;
●protects the superconducting coils, in combination with the vacuum vessel, from excessive nuclear heating and radiation damage.
Divertor (purple)
●exhausts the major part of the plasma heating power and He from the plasma, while minimising the impurity influx to the plasma;
●must tolerate high heat loads while at the same time providing neutron shielding for the vacuum vessel and magnet coils in the vicinity of the divertor as the main interface component under normal operation between the plasma and material surfaces.
  7. Parameters of Blanket and Divertor [2]
  8. RH Equipment: Boom Type
  Boom: cantilevered beam (deformation, vibration: large)
-> Precise positioning: difficult
Moving speed: slow
-> Low working effectiveness
The boom type has been adapted to the Joint European Torus (JET), which is one of largest existing fusion devices.
  9. RH Equipment: Rail-Vehicle Type
  Functions are separated: structure (rail) and vehicle/manipulator
Rail: multiple support (high stiffness)
->Precise positioning: available
Moving speed: high
->high working effectiveness
The vehicle type is adapted as the RH equipment for the ITER blanket.

10. Rail-Vehicle Type RH Equipment
  A semi-circular rail is installed in the vacuum vessel.
A monorail-like vehicle travels along the rail with a manipulator.
The rail is supported at three points.
The manipulator can transport ton-level weight.
11. Vehicle/Manipulator
12. Rail Deploying Equipment
13. Steps of Rail Connection
  Step (1) Start of rough positioning
Step (2) Rough positioning
Step (3) Fine positioning
Step (4) Attachment of hinge
Step (5) Rail deploying
14. Steps of Rail Deployment (1)
  Step (1) Support of vehicle fixing arm
Step (2) Deploying of rail by vehicle traveling drive
Step (3) Arcing of rail by rail positioning arm
15. Steps of Rail Deployment (2)
  Step (4) Deploying of final rail join
Step (5) Installation of rail support and cable handling
Step (6) Removal of vehicle fixing arm
16. Cable Handling Equipment
  The manipulator and its tools (20 motors) requires a multiple core cable (7.5 cm in diameter) for power supply (140 cores) and signal transmission (235 cores).
The cable is fed by a cable handling equipment.
17. Accumulator-Type and Reel-Type
Accumulator Type
The cable is accumulated by increasing the span between sheaves.
Merit:
Rotating connector is not needed.
Demerit:
Equipment becomes large.

Reel Type
Merit:
Equipment becomes compact.
Demerit:
It requires rotating connector (potentially noise source).

Arrangement of slip ring
●The slip ring becomes longer in the axial direction because of huge amount of power and signal lines.
●The slip ring is separated to two pieces, for power and for signal, and they are arranged coaxially.
->The device becomes compact.
18. Conclusion
The remote maintenance is one of essential technologies for a fusion reactor and its demonstration is one of technical objectives in the ITER.
The blanket is one of the major components which require remote maintenance and its RH equipment will be procured from Japan.
The Japan Atomic Energy Agency proposed the rail-vehicle type for the blanket RH equipment and completed its design.
19. Reference
[1] Project Specification, ITER_D_27ZRGH, Private Communication with ITER Organization (2008)
[2] Project Integration Document, ITER_D_2234RH, Private Communication with ITER Organization (2009)
[1] Project Requirements, ITER_D_27ZRW8, Private Communication with ITER Organization (2009)
EJAM OT11: "Overview of Remote Maintenance for ITER Blanket"