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Fusion Engineering and Design 75–79 (2005) 607–612

ITER vacuum vessel sector manufacturingdevelopment in Europe

Lawrence Jonesa,∗, Aldo Bianchib, Alain Crosc, Enrico di Pietroa,Benoit Giraudc, Kimihimo Ioki d, Lubomir Juneke, Bruno Parodib,

Michael Picka, Gian-Paulo Sanguinettib,Richard Tiveyd, Yuri Utin d

a EFDA CSU, Boltzmannstrasse 2, 85748 Garching, Germanyb Ansaldo Ricerche, Corso Perrone 25, 16161 Genova, Italy

c Framatome ANP, 10 rue Juliette Recamier, 69456 Lyon, Franced ITER JCT, Boltzmannstrasse 2, 85748 Garching, Germany

e Institute of Applied Mechanics Brno, Veveri 95, 61139 Brno, Czech Republic

Abstract

The ITER vacuum vessel, to be constructed on site from nine toroidal sectors, places as-welded manufacturing toleranceson the surfaces several times smaller than usual, in relation to its large size. Framatome ANP has proposed a manufacturingroute for the sector construction, accepted as the reference by the ITER International Team. To facilitate the achievement of ther sector andt he resultso©

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equired tight tolerances, EFDA has implemented a development programme, including the manufacturing part of thehe analysis of its distortion using SYSWELD computer modelling. This paper describes the manufacturing route and tf the development programme so far.2005 The European Commission. Published by Elsevier B.V. All rights reserved.

eywords: ITER vacuum vessel sector; VVPSM manufacture; Welding distortion assessment; SYSWELD

. Introduction

The ITER vacuum vessel (see Ref.[1]) provides therst tritium and vacuum boundary, and supports the

∗ Corresponding author. Tel.: +49 89 3299 4278;ax: +49 89 3299 4198.

E-mail address: [email protected] (L. Jones).

first wall blanket and divertor modules, the attachmrequirements of which complicate the construcwith a high density of welding and makes the achiement of the tight manufacturing tolerances problatic. During the manufacturing studies, the feedbfrom the representatives of the potential VV semanufacturing companies was clear: they wouldreluctant to embark on a VV sector contract, withoprototype included, due to the risk of rejection of a s

920-3796/$ – see front matter © 2005 The European Commission. Published by Elsevier B.V. All rights reserved.doi:10.1016/j.fusengdes.2005.06.308

608 L. Jones et al. / Fusion Engineering and Design 75–79 (2005) 607–612

tor due to out-of-tolerance, which ITER cannot relax asthe blanket module first wall components must be accu-rately mounted and the sectors must be welded togetheron site and offsets larger than 10 mm lead to unaccept-able bending stress in the walls. The central part of theexperimental investigation of distortion control is theplacement of a contract in 2004 with Ansaldo Ricerche,Genova for the construction of a full-size vacuum ves-sel poloidal segment (VVPSM). Since the goal of thisprogramme is to be able to extrapolate the VVPSMmeasured distortions to the actual ITER VV sector,numerical simulations by IAM, Brno, Czech Republic,using the SYSWELD program, which is a commer-cial program marketed by ESI Ltd. (http://www.esi-group.com) is used with a new module, incorporatinglocal models of instrumented welding coupons, theresults of which are included in simplified global mod-els.

2. VV sector manufacturing method

The ITER VV sector manufacturing method,based on Framatome ANP experience with submarinedouble-hulled fabrication is shown inFig. 1, involvesthe joining of four, partially-constructed poloidal seg-ments together in an erection frame in four parallelassembly lines, due to the position of the VV on theITER critical path. To limit the welding distortion,each segment at the beginning of the manufacture pro-c ghto sup-p bly.I ringt heo eg-m thej ar-r nce.T lvest ani hasb tor-t go mmd t thew mt sibly

faulty root of the first weld. The outer wall welds areone-sided and have limited inspection capabilities, soNGTIG is used. E-beam welding was a clear choicefor the circular flexible housings to inner wall weld-ing and more extensive use can be considered for innerwall butt welds, considering the existence of the newpro-beam facility (6 m× 7 m× 14 m long) in Burg,Germany. One of the challenging features of the con-struction is the high density of welded features, bestexemplified in the region including the lower triangu-lar support, divertor port and divertor rail, shown inFigs. 2 and 3.

3. Vacuum vessel poloidal segment model

Since the mock-up, to be representative of the fullmanufacturing process, cannot simply be one of thefour poloidal segments, it includes the all-importantsector-to-sector weld. The VVPSM, as shown inFig. 4,consists of a 40◦, 5 m high, 20 tonnes part of the inboardupper section, is fabricated according to the manufac-turing route, including bracing fixtures (as heavy as thesection itself), welding applications, restraint effectsand fit-up aspects, and will be constructed using theITER-grade stainless steel 316 L (N), similar to butwith more constrained properties than the RCC-MRgrade of 316. A 40-tonne ferritic steel structure withstiffness comparable to the missing part of the sectoris included with the internal stiffening jigs, which arer lsos thefi terw havet ibles . Ino ts, ad uterhS datet ure-m theo f thec oa portrt wos

ess, has welded a jig to its inner wall, (total weif 135 tonnes per segment) which is also used fororting from the erection frame during final assem

n contrast to the method used by the JAHT duhe L3 project of constructing a VV sector (from tld ITER larger design with backplate), when the sents were completed before welding together,

oining of the segments in the EU concept is cied out half-way through the manufacturing sequehis is because the welding of these parts invo

he risk of unavoidable distortion, since there isnternal rib also to be joined. A weld procedureeen qualified that avoids angular (not lateral) dis

ion of the inner wall 60 mm butt weld by carryinut the first group of passes from one side to 18eep using manual metal arc, then machining oueld groove preparation of the following NGTIG fro

he other side, at the same time remove the pos

emoved on completion of the fabrication, and aimulated as this has an important influence onnal ‘distorted’ shape. The welding of the closing oualls provides a particular challenge, as the plates

o fit between ribs and the large number of flexupport housings that join the inner to outer wallsrder to alleviate this fit-up issue and reduce cosesign of two-part housing is used, in which the oole is bored after rib welding, as shown inFig. 5.ince an important aspect of the contract is to vali

he computer modelling activity, extensive measents of the individual welding shrinkages and

verall wall movements are taken at each stage oonstruction. The finished VVPSM will be cut in twnd used as the basis for a mock-up that will supobotic equipment (see Wu et al.[2]) welding, cut-ing and inspection trials to simulate the joining of tectors.

http://www.esi-group.com/

L. Jones et al. / Fusion Engineering and Design 75–79 (2005) 607–612 609

Fig. 1. Manufacturing route of ITER VV sector: (1) welding of inner shell, ribs and housings on support jigs, (2) assembly of PS 1–4 (includingsupport jigs), (3) welding of PS 1–4 to a 40◦ VV sector and (4) welding of outer shell and removal of support jigs.

4. SYSWELD modeling

A new SYSWELD module has recently beenreleased which allows for the computation of weldingdistortion of large complicated structures previouslyconsidered impossible. This so-called ‘local–global’module achieves this by first validating with experi-

ment on simple coupons local models for each typeof weld with all thermal and mechanical properties,then integrating these models into a simplified globalmodel, where the slow thermal calculations are carriedout only in the (moving) region of the welding opera-tion, while the rest of the structure is represented by astatic FE model. The goal of the numerical simulation


Fig. 2. Inboard triangular section.

is the prediction of distortion of the VV sector, duringwelding operations and the comparison of distortionbetween numerical simulation and manufacturing tol-erances. First the correct input data and numerical anal-ysis requirements are needed to obtain good agreementwith measurement. Then the local model must be pre-pared for transfer to global model so these requirementsmust also be established. To validate the method for60 mm thickness, TIG welding experiments on 20 mmcoupons with 11 passes are sufficient, as shown in themesh described inFig. 6. The parameters measured

Fig. 4. VVPSM with jigs.

are: thermal cycle by thermocouples and digital ther-mometers, stresses on the surface by strain gauges,distortion and shrinkage by inductive gauges, residualstresses by the hole drilling method and size, and shapeof the weld bead on the macro. Before the successful

Fig. 5. Two-part flexible support housing.
Fig. 3. Inboard triangular section cross-section.

L. Jones et al. / Fusion Engineering and Design 75–79 (2005) 607–612 611

Fig. 6. SYSWELD finite element mesh for local model.

outcome was achieved, first calculations showed thatthe SYSWELD local–global module yielded incorrectresults for the thicker material and interactions withthe ESI Group, the owners of the software, and mod-ifications of the software were required, which waspossible as the IAM, Brno has a long history of suchinteraction and development of SYSWELD. Severaladditional developments were also needed to refinethe model to yield more accurate results. The analysisshowed that for stiff structures such as the VV sector,the differences between the analysis with and withoutlarge strain are very small, even though the stress pat-tern is slightly different. The material behaviour wasalso extended to high temperatures by including valuessupplied by ITER/EFDA, data from ESI and experi-ments carried out by IAM, Brno. This greater definitionof properties into the visco-plastic region of an unre-strained coupon compared to the calculation with lowtemperature values caused the prediction of the bend-

ing to increase by 25%. The validation of this first-everuse of the SYSWELD program for local–global anal-ysis with thick walled, multi-pass welding is carriedout on a well-restrained sample, with the stiffness sim-ulated by springs on one side. The model was firstcalculated in local mode, using solid elements, in therestrained condition and then the restraint released andthe new deflection assessed. The global model of thesame component was prepared, using small parts ofthe local model and gave results with an agreementup to 5%, mainly dependent on the mesh size whilethe global model using shell-3D (important for latersaving computer time) gave a value up to 15% high.The preparations for the final real numerical simula-tion on the VVPSM have thus far been successfullyachieved and will be carried out during 2005 and 2006.The final goal to apply this work later during the VVsector manufacture will be implemented during the VVsector manufacture phase.


5. Conclusions

The positive results of the design development andanalytical work carried out thus far and the supportingexperimental work to be carried out in the next 2years should provide the necessary confidence tothe companies for manufacturing programme forthe VV sectors. This indicates a good prospect forthe successful achievement of the tight tolerancerequirements, given the high importance for the

ITER programme and its position on the time-criticalpath.

References

[1] Y. Utin, et al., Design progress of the ITER vacuum vessel andports, Fusion Eng. Des. 75–79 (2005) 571–575.

[2] H. Wu, et al., Development and control towards a parallel waterhydraulic weld/cut robot for machining processes in ITER vac-uum vessel, Fusion Eng. Des. 75–79 (2005) 625–631.

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