Technical

As a result of the continual review of the ITER design in preparation particularly of the procurement documents for long-lead items, a number of design improvements, selections of options, and design development have been carried out compared to the original design at the end of the EDA.  In addition R&D has been going on regarding manufacturing, and there has been progress in procurement specification development nad in documentation updating.

Magnets

• Strand critical current has been increased (from ~600 to ~800 A/mm²), and stainless steel jacketing is now the reference for all conductors.  This has been done to recover from the reduced thermal stability margin experienced in the Large Project model coils compared to what was expected, and to avoid filament fracture by keeping the cable in compression.
• A friction joint of welded plates has been chosen for the outer intercoil structures.  The previous option of a box section interface with shear keys was shown by analysis to be inadequate, with the keyways opening up in operation.

Vessels/Blanket

• The earlier design of vessel supports, in which the vessel was attached to the magnet structure in the shadow of the TF coils, made assembly and adjustment very difficult.  An improved scheme has been designed where the vessel is supported on its lower ports with a direct link to the cryostat lower ring pedestal.
• The number of lower ports has been reduced to nine to reduce cost, as well as to greatly simplify the assembly of the thermal shield.
• The blanket module reference design foresees a first wall supported from a welded central leg.  This is now preferred over the earlier two bolted and welded options.
• The module arrangement has been improved around the neutral beam (NB) ports.  The previous arrangement was made to try to retain standard modules throughout the machine, but resulted in small size modules and difficult support arrangements around these ports.  By customising a few modules it has now been possible to produce a more robust design, and the inevitable cost increment has been shown to be rather small.
• The interlocking joint of the thermal shield sectors has been improved.    A substantial revision of the whole cryostat thermal shield section has resulted in a large reduction of the number of labyrinths and subsequently a simplification of the assembly and a reduction of the heat losses.

Building/Services

• The introduction of confined port cells has eliminated the need for secondary vacuum closure plates at the cryostat boundary. Such a change has greatly simplified the access to the vacuum vessel ports also allowing further simplification in the design of services and lines to the related post plugs.
• Detailed studies of the layout of equipment and services around the machine have led to the relocation of some equipment.
• It was concluded that the site would require the incorporation of seismic isolation. Associated simplifications within the isolated island are still underway.
• The site layout has been improved, for example by relocating the hot cell further to the east.  This now allows straighter routing of NB high voltage lines, allowing the NB injectors to be assembled from larger units.

Manufacturing R&D

R&D has been continuing on items closely related to the manufacturing of long lead items.  For example:

• Vacuum vessel welds inspection, where some welds have restricted or one-sided access only.  Low angle ultrasonic testing and photo-thermal camera techniques have been developed for this use.
• Finalization of fabrication methods and QA is underway by manufacturing critical parts of the vacuum vessel.
• The ITER poloidal field coil NbTi conductor will soon be tested.
• A manufacturing study of the TF coil case, radial plate and inter coil structure, is underway.
• Testing of cutting and rewelding of the first wall panel leg and the hydraulic connector of the shield blanket is underway.
• Nb₃Sn strand with the new specification is being produced and tested by 15 vendors worldwide.
• The blanket first wall panels will be produced soon also by those Participants who have recently joined ITER.

Procurement Specification Writing

Drafting of detailed technical specifications has continued for long lead items, namely the magnet strand and conductor, and PF and TF coils, the main vessel and ports, the blanket coolant manifolds, and the tokamak building complex, cryogenic halls used for PF coil winding, and service tunnels. Task Forces have been established with PT/IT membership to complete work in the necessary detail and with appropriately managed industrial input. This has, however, only partly been successful due to the lack of a site decision.  Development of other procurement specifications to cover interfaces with long lead items has continued, limited by insufficient human resources.

Documentation Updating

The above design developments naturally lead to inconsistencies with respect to the formal Project documentation produced in 2001. Also with a view to smoothly transferring responsibilities to a new organisation, an update of this documentation has been carried out.  The opportunity has also been taken to introduce a new configuration control document encapsulating previous top-level requirements and key system parameters, thereby making configuration management easier. The revised documentation is currently being made available to the Participant Teams via the ITER intranet site (password required).

Organisational

Five elements have been introduced in the project to help ensure that what will actually be built will conform to the requirements as well as to the documentation referring to the hardware.

• Technical Coordination Meetings (TCM). These decide on change proposals, and organise and schedule supporting work and priorities.
• Improved process documentation. Design Change Requests which document proposals for changes, Design Work Orders which request CAD effort, and Design Work Check forms to check drawing office output, have all been introduced.
• Design Integration/Drawing Office (DIDO) Meetings. These review ongoing CAD progress, prioritise new CAD effort allocation, and schedule detailed design reviews.
• Virtual Product data Management, along with an upgrade of CAD software. This gives the ability to perform clash detection, utility routing, collaborative design and better tools to control the configuration and allocation of the available space particularly around the tokamak.  The upgrade of capability is now well advanced, with use in full production work planned from around the end of 2004.
• Document Management System. New document management software based on the ZOPE open source toolbox has been implemented in the project to cope with new requirements specific to this type of project, and to speed up document control procedures, as well as to ease collaboration with external institutions.