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EU PWI Task Force

Issue card: change of first wall. EU PWI Task Force. ITER. V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006. Issue card: exchangeable first wall V. Philipps. ITER divertor: 54 cassettes which can be exchanged using remote handling Estimated minimum time (3 months, if spares available(? ).

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EU PWI Task Force

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  1. Issue card: change of first wall EU PWI Task Force ITER V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Issue card: exchangeable first wall V. Philipps ITER divertor: 54 cassettes which can be exchanged using remote handling Estimated minimum time (3 months, if spares available(? ) • ITER will start with the present Divertor material choice and decide about the choice for the ITER T-phase depending on actual results on • Divertor performance and transient power experiences • T- retention (see issue card H,D,T retention measurements)

  2. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 • Critical issues with a Be first wall • Erosion • steady state • transients (Disruptions, Elms) → melting • Power loads (upper dump plate, Be start limiters ) • Be-W interaction (alloying) • T retention (co-deposition of Be with T ) Large uncertainties in all these areas  Motivation for the JET ITER like wall project More information will probably evolve but to late for ITER decisions now

  3. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 ITER has to test the Demo first wall material which will be selected as a result from ITER and other experiences Most probably not Be High Z most promising candidates → First wall flexibility the only solution Non changeable first wall represents a large risk for the overall project

  4. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Aim: Allow to change the ITER first wall material in a time window of about 1 year. Technical implications (ordering of actions ) 1.Increase the remote handling capability for cutting and rewelding 2. Procure a spare set of first wall panels 3. Redesign the first wall such that exchange is more easier (poloidal limiters, more bolting in between (less welding) 4. perform R&D to develop a W, C main wall target 1-3 must be explored in a working group with ITER and outside ITER experts

  5. Remote handling • currently a track at the bottom of the machine covering 180 degrees of the circumference. For modules farther apart the entire track must be removed, shifted toroidally, and re-installed. • rack expanding to 360 degrees increase capabilities Cost: doubling (cost of current system is 27.1 kIUA, or 38Meuros, chapter 7, PDD, page 9). • Adding additional arms and additional port tracks to remove items from the machine to the hot cell - so-called cask transporters (cost: 10kIUA, Chapter 7, PDD, page 8) • Spare modules in storage. Cost: 142.6 kIUA (199.6 Meuros, present design, chapter 7, PDD, page 8). • Compromise: smaller set of spares of most important tiles • Presently one rail at the bottom of the machine. Possible second system via an arm through a port. In under investigation (EFDA). No cost estimate.

  6. First wall PFC design • Separate first wall panel and shield modules inside the machine • No cost estimate and technical difficulty assessment • Change wall design to poloidal limiters and recessed area in between (e.g. JET). • three levels of wall protection (limiters): • Port limiters for start up • Poloidal limiters (~e.g. 10 spaced toroidally) 10 cm closer, removal as rapid as possible (locating them next to ports) better access to coolant pipes from the port • Shield modules small heat loading (neutron heating, radiation ). bolted tiles to a water cooled substrate possible ( East) ?) • Cost: similar as the current system (?)

  7. Reserve slides for discussion

  8. Issue card: change of first wall EU PWI Task Force Shield First wall panel, separable V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Central support leg 4 panels attached to 1 first wall module

  9. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 The remote maintenance of each module involves cut and rewelding of the main joint and the plug. They are done by a Nd-YAG laser delivered with fibre optics to a periscope tool rotating in the front access hole. A jet of inert gas removes the molten metal. The nozzle passes through the 30 mm access hole while it is straight and then opens 90

  10. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Be- CuCrZ – SS cooling tubes and SS back plate hipped together

  11. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Federici, Kukushkin, SOFT 2002 B2 Eirene ITER calculation about 6 g Be-erosion/ITER shot, mainly due to CXS by divertor leackage, gas inlet Ion wall interaction simulated with two step e-folding length to take into account enhanced transport in the outer SOL Simple scaling of JET Be wall erosion (20% wall coverage) to ITER via input energy implies 30-100g Be (M.Stamp, 10th carbon workshop, Juelich)

  12. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 • The power loading of the first wall need a critical review in light of recent results on first wall loading during • Inter ELM phase • ELMs • Disruptions • Power loads on upper dump plates • “special” disruptions (ITB plasmas) deposit a large part of stored energy directly onto the inner wall , this will lead to Be melting of inner wall guard limiters in JET already ! ITER mitigated disruptions at full stored energy with uniform power dissipation in 1 ms (thermal quench) will melt Be (D. Whyte) • Consequences of Be melting not evaluated in terms • Melt layer erosion and movement • Subsequent power handling performance • Also large ELMs can melt the Be first wall. ( but ELM energy losses must be limited already from divertor power handling viewpoint)

  13. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Be deposited on W C. Linsmeier et al At  800K Be alloy dominates At  1000K Be2W stoichiometric composition At RT thin alloy forms at interlayer and Be films growth

  14. Issue card: change of first wall EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 T- retention in mixed codeposited Be –C (O) layers • At RT, Be-rich mixed Be/C/O and C layers retain deuterium at similar levels • Only at higher temperature (> 400-500K) Be-rich layers have significant less retention • Codeposited Be/C layers in PISCES-B are Be rich • Influence of oxygen to investigate more D/C codeposited Be-C-(O) layers in JET contain high levels of D similar to pure C layers These layers are C and O rich M. J. Baldwin et al., J. Nucl. Mater. 337-339(2005)590.

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