EUOFUSION WPM-CP(6) 5466 D Wolff t al. Th Impact on mot Maintnanc of Varying th Aspct atio an Numbr of TF Coils for a Dmonstration Fusion Powr Plant Prprint of Papr to b submitt for publication in Procings of 29th Symposium on Fusion Tchnology (SOFT 206) This work has bn carri out within th framwork of th EUOfusion Consortium an has rciv funing from th Euratom rsarch an training programm 204-208 unr grant agrmnt No 633053. Th viws an opinions xprss hrin o not ncssarily rflct thos of th Europan Commission.
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Th Impact on mot Maintnanc of Varying th Aspct atio an Numbr of TF Coils for DEMO Dan Wolff a, Matti Colman b, Davi Coopr a, Olivr Crofts a, Jonathan Horn a, Jonathan Kp a, Antony Loving a a mot Applications in Challnging Environmnts (ACE), UKAEA, Culham Scinc Cntr, Abingon, Oxforshir, OX4 3DB, Unit Kingom b EUOfusion Consortium, Boltzmannstr.2, Garching 85748,Grmany As part of th concptual sign stuis for a Europan DEMO, iffrnt tokamak gomtris ar bing consir. As intifi in th EFDA oamap to th ralisation of Fusion Enrgy, 203: Th intgration of th mot Maintnanc systm within th DEMO plant is an ssntial task within th DEMO CDA phas. This will involv stablishing rquirmnts, functions an intrfacs with many othr systms to nsur that plant availability an maintainability ar consir from th outst. In orr to fulfil this intgration rquirmnt iffrnt gomtris of DEMO hav bn assss for thir impact on rmot maintnanc (M). Th aspct ratio an numbr of TF coils hav bn intifi as th pivotal variabls, riving th tokamak gomtry, with significant ffcts on rmot maintnanc both in trms of tchnical fasibility an sp of opration. Tokamak gomtris with aspct ratios from 2.6 to 4.0 an 6 or 8 TF coils hav bn compar. Th rsults of this valuation show that highr aspct ratios an lowr numbrs of TF coils ar bnficial to M both in trms of tchnical fasibility an sp of oprations. To livr a maintainabl DEMO, fforts must b ma to maximiz its aspct ratio an minimiz th numbr of TF coils. Kywors: Intgration, Optimization, Systms Enginring, mot Maintnanc, Holistic Dsign, Tokamak Gomtry. Introuction In fining th concpt sign of th DEMO mot Maintnanc (M) systm it has always bn apparnt that th numbr of TF coils an th aspct ratio spcifi for th DEMO tokamak will hav a major impact. This papr sts out to quantify th ffct of varying th numbr of TF coils an th aspct ratio of DEMO on its M systm, in trms of tchnical fasibility an sp of rmot maintnanc oprations. It compars tokamak gomtris with aspct ratios from 2.6 to 4.0 an 6 or 8 TF coils. 2. Tokamak gomtris consir Th basis of th analysis was to compar altrnativ tokamak gomtris to Eurofusion s 205 baslin. Th four othr gomtris consir wr; Eurofusion s 204 baslin, a 6 TF coil variant with th 205 baslin aspct ratio (204-5 Intrmiat) gnrat by ACE, a ruc aspct ratio / 8 TF coil variant (uc A (TF 8)) gnrat by th Programm Managmnt Unit (PMU) of Eurofusion, an finally th sam ruc aspct ratio variant but with 6 TF coils (uc A (TF 6)) gnrat by ACE. Th top lvl paramtrs of th fiv tokamak gomtris consir ar shown in tabl an th rlativ sizs in figur. All gomtris follow th sam blankt sgmntation, with two inboar blankt multi-moul sgmnts (MMS) an thr outboar MMS pr sctor. Tabl. Dimnsions of th gomtris consir. [PFS Plasma Facing Surfac] n i l s a B 4 0 Dimnsion 2 5-4 0 2 t ia r m t In n i l s a B 5 0 2 A c u Aspct atio 4.0 3. 3. 2.6 2.6 Numbr of TF coils Inboar PFS aius at Mi-plan (m) Outboar PFS aius at Mi-plan (m) Hight from Mi-plan to Top PFS (m) 3. Factors consir ) 6 F T ( A c u 6 6 8 6 8 6.6 5.9 5.9 5.6 5.6.4 2.2 2.2 3.3 3.3 3.9 5.2 5.2 7.0 7.0 Tokamak gomtris wr compar in trms of th sp an tchnical fasibility of carrying out M oprations, using ky prformanc rlat paramtrs, ) 8 F T ( author s mail: an.wolff@ukaa.uk
Fig.. Comparativ sizs of th DEMO gomtris consir. with appropriat wightings appli, as fin by M xprts from ACE. Th paramtrs focus on th rmoval an rplacmnt of th blankt multi-moul sgmnts (MMS) through th uppr vrtical ports, as this is m to b on of th main rivrs for th sp an tchnical fasibility of th M in DEMO. Th following ky paramtrs wr us to compar th iffrnt gomtris: Total numbr of Blankt sgmnts. Th total numbr of blankt sgmnts corrlats strongly with th ovrall tim rquir to carry out maintnanc of DEMO. Blankt manifol slnrnss ratio. Th blankt manifol slnrnss ratio is a masur of how flxibl th MMS is. It was calculat by iviing th Blankt sgmnt lngth by th minimum raius of gyration of th MMS manifol. It is assum that all structural loas in th MMS ar takn by th manifol. A mor flxibl MMS rquirs slowr M sp an mor complx collision avoianc controls. Numbr of kinmatic stps to rmov a Blankt sgmnt. This is th numbr of istinct movmnts (translations or rotations) that ach MMS will n to go through in orr to b xtract from th tokamak. This has bn trmin from a first pass look at th likly routing for th MMS, ignoring minor clashs which hav yt to b rsolv an not taking into account any movmnts that may b rivn by tooling gomtry. If a gratr numbr of translations an rotations ar rquir to rmov an MMS, rmoval (an rplacmnt) will b slowr an rquir a mor complx control systm an tooling. Equivalnt tooling strss. This is a masur of th loa th MMS rmoval/rplacmnt tooling will carry, rlativ to th spac to packag that tooling. It was calculat by iviing th approximat gravitational loa of th blankt sgmnt bing consir by th cross-sctional ara of uppr port in which th lifting an manipulation tooling must b hous. A highr strss quats to, mor challngs in th sign, packaging an opration of th M tooling for MMS rmoval an rplacmnt. Equivalnt strss at th Blankt lifting intrfac This spcifically consirs th strss at th intrfac btwn th MMS an th lifting tooling. Highr strss hr will mak signing an oprating th rmoval/rplacmnt tooling mor ifficult. It was calculat by iviing th approximat gravitational loa of th blankt sgmnt bing consir by th crosssctional ara of th sam blankt sgmnt that is accssibl through th uppr port. Torqu at th Blankt lifting intrfac. Anothr ky paramtr affcting th tooling sign an oprational nvlop will b th momnt arm from th lifting point to th MMS cntr of gravity assuming a homognous mass istribution. Hr this is coupl with th approximat gravitational loa of th blankt sgmnt bing consir to giv a torqu figur. Th highr this torqu valu, th mor ifficult it will b to sign, packag an oprat M tooling in th rquir spac to manouvr th blankt sgmnts. Ara ratio btwn th Blankt bing hanl an th aprtur through which it must pass. This is th total cross-sctional ara of th MMS bing consir whn viw from abov ivi by th crosssctional ara of th uppr vrtical port availabl for that MMS to xit/ntr through, also viw from abov. As th ara ratio rucs, th room for manouvr of th MMS incrass, making xtraction asir an clashs lss likly. Gratr claranc for th MMS uring rmoval an rplacmnt will la to a simpl movmnt control systm an scop for fastr movs. 4. lativ wighting of comparison paramtrs In orr to nsur th rlativ ffct of th iffrnt paramtrs on M Sp an M Tchnical Fasibility was proprly captur, th Analytical Hirarchy Procss (AHP) was appli. First, a pairwis comparison of all paramtrs was carri out by a group of M xprts from ACE, sparatly in trms of both M Sp an M Tchnical Fasibility. Th rlativ ffct of ach pair of paramtrs on th two critria was trmin using a scal from (qual) to 5 (strong iffrnc). This gnrat a pair of matrics from which th ignvctors wr thn calculat. Which th AHP shows ar rprsntativ of th rlativ importanc of th paramtrs []. Ths wr thn appli in th calculation of th M Sp Inx (MSI) an th M Tchnical Fasibility Inx (MTFI) for ach gomtry bing consir.
Tabls 2 shows th rlativ ffct of th iffrnt paramtrs on sp of M oprations an tchnical fasibility of M. Tabl 2. Sp an tchnical fasibility wighting calculat using th Analytical Hirarchy Procss (AHP). Paramtr (s Sc. 3 for tails) M sp wighting M tchnical fasibility wighting Total numbr of blankt sgmnts 0.40 0.03 Manifol slnrnss ratio 0.8 0.4 Kinmatic stps to rmov MMS 0.2 0.05 Equivalnt Tooling Strss 0.04 0.9 Equivalnt Intrfac Strss 0.04 0.9 Intrfac Torqu 0.06 0.30 Ara ratio 0.4 0.09 5. Comparison mthoology In orr to compar th iffrnt gomtris in trms of both M tchnical fasibility an sp using th intifi paramtrs th procing mthoology was follow: First, all paramtr valus wr trmin from th CAD mols of th fiv iffrnt gomtry variants. In th cas of Eurofusion s 205 baslin, this involv first applying prviously agr changs to th blankt sgmntation to nsur that th kinmatics of ach MMS rmoval wr fasibl. For all th othr gomtry variants th blankt sgmntation was stablish bas on th sam principls. Having gathr all paramtr variabls for ach variant, th approach iffrs for th sp an tchnical fasibility. To compar th sp of M oprations th aim was to gt an ovrall valuation of th rlativ tim takn to rmov a full st of blankt sgmnts. Howvr, for th tchnical fasibility th intntion was to compar th worst cas for ach paramtr typ. 5. mot Maintnanc Sp Inx (MSI) Th MSI is a masur of th impact of ach gomtry variant on th sp with which M oprations can b complt. A highr MSI quats to fastr M oprations. In orr to compar th sp of M th nxt stp was to normaliz ach of th paramtrs to a imnsionlss figur rlativ to th valus for th 205 baslin. This was on by iviing ach paramtr valu for ach MMS typ by th corrsponing valu for th 205 baslin. This gav an unwight inx valu for ach paramtr of ach gomtry variant. Th sp wightings in tabl 2 wr thn appli sparatly to ach unwight inx valu to tak account of th magnitu of th ffct of th paramtr on M sp. This gav a wight inx valu for M sp for ach paramtr of ach gomtry variant. For ach gomtry variant th wight paramtrs wr thn combin to giv an M Sp Inx (MSI) for ach MMS typ. This was calculat by fining th invrs of th prouct of all iniviual paramtrs, wight for sp, rlat to ach MMS typ. This gav an MSI for ach MMS typ of ach gomtry variant. Finally, th avrag of th MMS typ MSIs was calculat for ach gomtry variant. Ths valus can now b us to compar ach gomtry variant consir an any futur variants in trms of thir ffct on M sp. 5. mot Maintnanc Tchnical Fasibility Inx (MTFI) Th MTFI is a masur of th impact of ach gomtry variant on th tchnical fasibility of signing an M systm capabl of carrying out th rquir maintnanc. A highr MTFI quats to a gomtry that is mor tchnically fasibl to maintain. To compar th tchnical fasibility of maintaining th iffrnt gomtris with M, first th worst cas for ach of th paramtr typs scrib in sction 3 was foun for ach gomtry variant. As, for all th paramtrs consir, lowr valus corrlat with improv tchnical fasibility th worst cas was th maximum valu from th fiv MMS typs. Th nxt stp was to normaliz ach of ths worst cas valus rlativ to th valus for th 205 baslin. This gav an unwight inx valu for ach paramtr of ach gomtry variant. Th tchnical fasibility wightings in tabl 2 wr thn appli sparatly to ach unwight inx valu to tak account of th magnitu of th ffct of th paramtr on M tchnical fasibility. This gav a wight inx valu for M tchnical fasibility for ach paramtr of ach gomtry variant. For ach gomtry variant th wight paramtrs wr thn combin to giv an ovrall M Tchnical Fasibility Inx (MTFI). This was calculat by fining th invrs of th prouct of all iniviual paramtrs, wight for tchnical fasibility, for that gomtry variant. Ths MTFI valus can now b us to compar ach gomtry variant consir an any futur variants in trms of thir ffct on M tchnical fasibility. 6. sults Th calculat valus for MSI & MFTI ar shown in tabls 3 & 4. Thy show that both MTFI & MSI incras with incrasing aspct ratio (physically smallr machins) an crasing numbr of TF coils.
Tabl 3. mot Maintnanc Sp Inx (MSI) valus for th fiv gomtry variants consir No of TF coils MSI Tabl 4. mot Maintnanc Tchnical Fasibility Inx (MTFI) valus for th fiv gomtry variants consir MTFI No of TF coils 7. Conclusion Aspct atio 2.6 3. 4.0 6 0.97.06.3 8 0.93.00 Aspct atio 2.6 3. 4.0 6 0.90.04.2 8 0.86.00 Having rviw th rsults of this invstigation th following conclusions can b rawn: Thos EU DEMO gomtris with a highr aspct ratio ar fastr to rmotly maintain than gomtris with lowr aspct ratios. This is logical as highr aspct ratios quat to a smallr machin with shortr, lightr MMS, nabling quickr movmnts an shortr path lngths for thos MMS to travl along. mot Maintnanc of EU DEMO gomtris with a highr aspct ratio is mor tchnically fasibl than lowr aspct ratio gomtris. Again this follows as th shortr, lightr MMS of a smallr, highr aspct ratio machin mak sign of th tooling an control systm to manipulat it, asir. EU DEMO gomtris with a lowr numbr of TF coils ar fastr to rmotly maintain than thos with mor TF coils. This is vry simply own to thr bing lss parts to b maintain an hnc ovrall shortr maintnanc urations. mot Maintnanc of EU DEMO gomtris with a lowr numbr of TF coils is mor tchnically fasibl than for highr numbrs of TF coils. This can b largly attribut to th rlativ incras in th siz of th uppr port allowing mor spac in which to packag th M tooling. From a rmot maintnanc prspctiv, both in trms of tchnical fasibility an sp, of th gomtry variants consir, th Eurofusion 204 Baslin is th optimum sign. This is owing to th fact that this is th gomtry variant with th smallst numbr of TF coils an largst aspct ratio. In orr to livr a DEMO machin that can b maintain, fforts must b ma to maximis th aspct ratio of th vic an minimis th numbr of TF coils. Shoul th ability to altr ths paramtrs b limit by othr ovrriing consirations, thn significant rsourcs must b allocat at an arly stag to vloping M solutions. Diffrnt altrnativs shoul b vlop an valuat making us of proof of principl tsts to riv up th Tchnology ainss Lvls of caniat solutions. Howvr, this will not guarant that a suitabl M solution can b achiv. Through- lif cost is a ky lmnt of proving th viability of a futur Fusion Powr Station. It is thrfor vital that fforts ar ma to nsur that th cost of oprating DEMO is minimiz. If an M solution can b foun that is sufficintly robust, th primary maintnanc cost rivr bcoms th sp with which M oprations can b carri out. Thrfor, from a maintnanc prspctiv, minimizing th numbr of TF coils an maximizing th aspct ratio of th DEMO machin will also ruc th through lif cost. Maintnanc howvr cannot b consir in isolation an is only on aspct that must b takn into account whn trying to vlop th optimum sign of DEMO. 8. Futur work Thus far only a limit rang of gomtris hav bn consir. This mthoology coul b us to xplor a wir rang of gomtris, iffrnt gomtry paramtrs an altrnativ blankt sgmntation. Currntly th Inics ar solly focuss on th blankt rplacmnt aspcts of M. Othr M activitis coul also b consir, with rlativ prioritis. Ultimatly this work shoul form part of wir cision making procss to ci th optimum DEMO gomtry taking account of th ns of all th various stakholrs. Acknowlgmnts This work has bn carri out within th framwork of th EUOfusion Consortium an has rciv funing from th Euratom rsarch an training programm 204-208 unr grant agrmnt No 633053 an from th CUK Enrgy Programm [grant numbr EP/I50045]. To obtain furthr information on th ata an mols unrlying this papr plas contact PublicationsManagr@ccf.ac.uk. Th viws an opinions xprss hrin o not ncssarily rflct thos of th Europan Commission. frncs [] Thomas L. Saaty, Dcision-making with th AHP: Why is th principal ignvctor ncssary, Europan Journal of Oprational sarch 45 (2003) 85 9.