L Giancarli et al Fusion Engineering and Design 61-62(2002)307-318 Some preliminary designs using SiCSic struc- Required design work involves the development tures have already been proposed, for both diver- of appropriate methods for modeling SiCSiC tors and shield. Tungste generally proposed composites and the establishment of appropriate as armor material, introducing in such a way an and validated design rules additional material. In Dream studies. the Required r&d concerns with high priority the divertor vertical target uses SiC/SiC as structural two main issues associated with SiCSic struc material and is protected by a 2-mm thick CVD- tures, that is the low thermal conductivity and Sic region; the divertor baffle surface requires a 2- large uncertainty on the behavior under neutron mm thick w protection. irradiation. moreover. fabrication issues such as w has the drawback of having significant complex shape manufacturing, thin wall manufac activation and afterheat levels, therefore its use turing and joints, have to be addressed with large should be strongly minimized in order not to experimental campaigns before achieving satisfac- jeopardize the good safety features of the blanket. tory solutions. Depending on the concept, He- SClL blankets are associated with high-velocity hermeticity or Pb-17Li compatibility, at the Pb-17Li-cooled divertor while DREAM uses appropriate temperatures and pressure, have also high-pressure He-cooled divertor. In all cases, the to be demonstrated maximum acceptable heat flux was estimated to be The cost of these required developments could 5 MW/m be prohibitive for a single research program. One Detailed shielding design has not yet been of the advantages of SiC!Sic is that it has performed in any of the considered blankets applications in other field than fusion, such as studies. Only proposals based on qualitative con- aerospace research and advanced high tempera- siderations have been made. For instance. in the ture fission reactors Moreover. because of the framework of the TAURO studies, the shielding achievable high coolant temperature, it can also be design is based on SiCSiC structures, on Pb-17Li envisaged for hydrogen production using efficient coolant and on two hydrates, CaH and TiH, for high temperature processes currently available slowing down the neutron. A major drawback is These different potential applications could lead the risk of H-production at temperature above to a beneficial R&D cost sharing 800C. The demonstration that this level of Sic/ Sic structures for in-vessel fusion reactor temperature can be avoided in any accidental components are envisaged in all countries involved conditions has yet to be performed. In DREAM in technology development for fusion reactor es, the proposed shield is formed by He- Significant cooperation already exists among ing analysis has yet to be performed international cooperation is therefore strongly supported in order to focus the R&D efforts on he major critical issues and to efficiently achieve 6. R&D priorities and conclusions cost sharing with potential benefit for all partners The use of the Sic!siC composite as structural naterial in a FPr can be viewed as a high-risk high payoff endeavor. The high payoff is linked to References the superior safety characteristics of SiC arising The ARIES Team, A.R. Raffray, L. El-Guebaly, s from its low induced radioactivity and afterheat Gordeev, S. Malang, E. Mogahed, F. Najmabadi, L and to the possibility of high performance through Sviatoslavsky, D K. Sze, M.S. Tillack, X. Wang, High high temperature operation performance blanket for ARIES-AT P lant. Fusion The high risk is linked to the significant design Engineering and Design 58-59(2001)549-553. work and material R&d that has still to be [2H. Golfier, G. Aiello, R. Coutourier, M. Futterer, L. performed in order to conclude about the feasi- Giancarll, A. Li Puma, Y. Poitevin, J F. Salavy, J Szczepanski, Progress on the TAURO Blanket System. bility of the corresponding reactor components. Proceedings of ISFNT-6, San Diego, CA, April 2002.Some preliminary designs using SiCf/SiC struc￾tures have already been proposed, for both diver￾tors and shield. Tungsten been generally proposed as armor material, introducing in such a way an additional material. In DREAM studies, the divertor vertical target uses SiC/SiC as structural material and is protected by a 2-mm thick CVD￾SiC region; the divertor baffle surface requires a 2- mm thick W protection. W has the drawback of having significant activation and afterheat levels, therefore its use should be strongly minimized in order not to jeopardize the good safety features of the blanket. SCLL blankets are associated with high-velocity Pb/17Li-cooled divertor while DREAM uses high-pressure He-cooled divertor. In all cases, the maximum acceptable heat flux was estimated to be 5 MW/m2 . Detailed shielding design has not yet been performed in any of the considered blankets studies. Only proposals based on qualitative con￾siderations have been made. For instance, in the framework of the TAURO studies, the shielding design is based on SiCf/SiC structures, on Pb/17Li coolant and on two hydrates, CaH and TiH, for slowing down the neutron. A major drawback is the risk of H-production at temperature above 800 8C. The demonstration that this level of temperature can be avoided in any accidental conditions has yet to be performed. In DREAM studies, the proposed shield is formed by He￾cooled beds of SiC pebbles, but a complete shielding analysis has yet to be performed. 6. R&D priorities and conclusions The use of the SiCf/SiC composite as structural material in a FPR can be viewed as a high-risk high payoff endeavor. The high payoff is linked to the superior safety characteristics of SiC arising from its low induced radioactivity and afterheat, and to the possibility of high performance through high temperature operation. The high risk is linked to the significant design work and material R&D that has still to be performed in order to conclude about the feasi￾bility of the corresponding reactor components. Required design work involves the development of appropriate methods for modeling SiCf/SiC composites and the establishment of appropriate and validated design rules. Required R&D concerns with high priority the two main issues associated with SiCf/SiC struc￾tures, that is the low thermal conductivity and large uncertainty on the behavior under neutron irradiation. Moreover, fabrication issues, such as complex shape manufacturing, thin wall manufac￾turing and joints, have to be addressed with large experimental campaigns before achieving satisfac￾tory solutions. Depending on the concept, He￾hermeticity or Pb/17Li compatibility, at the appropriate temperatures and pressure, have also to be demonstrated. The cost of these required developments could be prohibitive for a single research program. One of the advantages of SiCf/SiC is that it has applications in other field than fusion, such as aerospace research and advanced high tempera￾ture fission reactors. Moreover, because of the achievable high coolant temperature, it can also be envisaged for hydrogen production using efficient high temperature processes currently available. These different potential applications could lead to a beneficial R&D cost sharing. SiCf/SiC structures for in-vessel fusion reactor components are envisaged in all countries involved in technology development for fusion reactor. Significant cooperation already exists among USA, EU and Japan. A continuation of this international cooperation is therefore strongly supported in order to focus the R&D efforts on the major critical issues and to efficiently achieve cost sharing with potential benefit for all partners. References [1] The ARIES Team, A.R. Raffray, L. El-Guebaly, S. Gordeev, S. Malang, E. Mogahed, F. Najmabadi, I. Sviatoslavsky, D.K. Sze, M.S. Tillack, X. Wang, High performance blanket for ARIES-AT power plant, Fusion Engineering and Design 58-59 (2001) 549/553. [2] H. Golfier, G. Aiello, R. Coutourier, M. Fu¨tterer, L. Giancarli, A. Li Puma, Y. Poitevin, J.F. Salavy, J. Szczepanski, Progress on the TAURO Blanket System, Proceedings of ISFNT-6, San Diego, CA, April 2002. L. 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