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A perspective on the history, status and future of fusion materials research in the united states
DISCUSSION ON INVITED PAPERS
Discussion 9
Paper on page
A perspective on the history, status and future of fusion materials research in the united states
H. Nickel: In your abstract you describe the necessity and the challenge of constructing and operating an International Fusion Materials Irradiation Facility. Would you be so kind as to explain the status of the discussion about this facility and the chance for realization of the IFMIF ? T. C. Reuther: Action on approaches to establishing an IFMIF is continuing under the IEA lmplementing Agreement on Materials in a followup to the 1986 Amelincks Panel report (issued by IEA). The IEA convened a workshop in this process in February 1989, which is now published in Fusion Technology, ed., R. Krakowski, LANL. Also available from IEA Paris. Discussion is continuing within the IEA Executive Committee. Also this is the subject of the final session of this conference. Paper on page
13
History, present status and future of fusion reactor materials reserch in the EC and other European countries P. Schiller, K. Ehrlich and J. Nihoul T. Kondo: Would you add a short comment ramics research for fusion applications ?
on ce-
P. Schiller: In the laboratories associated with the EC-fusion Program, work on ceramic insulators is under progress. Paper on page
19
Thermal effects and other critical issues of plasma facing components and J. B. Whitley
M. Dalle Donne: You mentioned a fluence of 45 dpa at the first wall for the technology phase of ITER. For NET, the foreseen material is 316L solution annealed. This material cannot withstand such a high fluence. HOW do you think to solve this problem ? A. Miyahara: I am not familiar with this area, but I have heard about already developed PCA (Primary Candidate Alloy in US) and JPCA (Japanese Primary Candidate Alloy) that can meet the requirement. K. EhrIich:
The envisaged
maximum
first wall of ITER of 45 dpa would indeed raise problems if a solution-annealed material 316L would be in the swelling regime of used above 35O”C, i.e. this material. However, as has been pointed outby J. L. Boutard (NET-Team) such high temperatures are not expected under normal operation for the first Wall.
T. C. Ffeuther
A. Miyahara
157
OR invited papers
fluence
in the
Paper on page
Radiation
25
enhanced sublimation
of carbon and carbon related materials V. Philipps, E. Vietzke and H. Trinkaus H. Wollenberger: The term “interstitial loosely bound to the surface” sounds a little strange. Could you please, give a few more details about the picture of this interstitial ? Thank you. V. Philipps: We believe that the carbon interstitial is not bound as a normal carbon surface atom when it arrives at the surface since it does not find immediately a free bond. It may be bound (shortly) only by weak (van der Waals-like) forces so that it can easily evapolate thermally. This special property of carbon materials must be the fundamental step in which it differs from other materials which do not show DESemission following the model I have outlined. J. Roth: Measurements have been made in collabo ration with ORNL on the radiation enhanced subliand simultaneous mation during Ar + bombardment Ti evaporation. The enhanced sublimation yield decreased drastically at Ti fluxes yielding a steady state Ti concentration of 10 at.% in the graphite surface. A stoichiometric TiC phase was not necessary for the reduction of the enhanced sublimation yield. V. Philipps: Thank you for this correction. I think that the observed suppression of DES by only 10% titanium in the surface is an important observation and is worth being investigated further in the future, including other doping materials. H. Wiedersich: Is any information on the effect of surface orientation on the DES of graphite available ? V. Philipps: According to my knowledge only one attempt has been made to investigate the dependence of DES on the orientation, but no difference was found within the experimental resolution. Please note that the mean differential range of the interstitials is rather short (IO nm) so that the interstitials easily reach the surface.
Discussion 9
Paper on page
A perspective on the history, status and future of fusion materials research in the united states
H. Nickel: In your abstract you describe the necessity and the challenge of constructing and operating an International Fusion Materials Irradiation Facility. Would you be so kind as to explain the status of the discussion about this facility and the chance for realization of the IFMIF ? T. C. Reuther: Action on approaches to establishing an IFMIF is continuing under the IEA lmplementing Agreement on Materials in a followup to the 1986 Amelincks Panel report (issued by IEA). The IEA convened a workshop in this process in February 1989, which is now published in Fusion Technology, ed., R. Krakowski, LANL. Also available from IEA Paris. Discussion is continuing within the IEA Executive Committee. Also this is the subject of the final session of this conference. Paper on page
13
History, present status and future of fusion reactor materials reserch in the EC and other European countries P. Schiller, K. Ehrlich and J. Nihoul T. Kondo: Would you add a short comment ramics research for fusion applications ?
on ce-
P. Schiller: In the laboratories associated with the EC-fusion Program, work on ceramic insulators is under progress. Paper on page
19
Thermal effects and other critical issues of plasma facing components and J. B. Whitley
M. Dalle Donne: You mentioned a fluence of 45 dpa at the first wall for the technology phase of ITER. For NET, the foreseen material is 316L solution annealed. This material cannot withstand such a high fluence. HOW do you think to solve this problem ? A. Miyahara: I am not familiar with this area, but I have heard about already developed PCA (Primary Candidate Alloy in US) and JPCA (Japanese Primary Candidate Alloy) that can meet the requirement. K. EhrIich:
The envisaged
maximum
first wall of ITER of 45 dpa would indeed raise problems if a solution-annealed material 316L would be in the swelling regime of used above 35O”C, i.e. this material. However, as has been pointed outby J. L. Boutard (NET-Team) such high temperatures are not expected under normal operation for the first Wall.
T. C. Ffeuther
A. Miyahara
157
OR invited papers
fluence
in the
Paper on page
Radiation
25
enhanced sublimation
of carbon and carbon related materials V. Philipps, E. Vietzke and H. Trinkaus H. Wollenberger: The term “interstitial loosely bound to the surface” sounds a little strange. Could you please, give a few more details about the picture of this interstitial ? Thank you. V. Philipps: We believe that the carbon interstitial is not bound as a normal carbon surface atom when it arrives at the surface since it does not find immediately a free bond. It may be bound (shortly) only by weak (van der Waals-like) forces so that it can easily evapolate thermally. This special property of carbon materials must be the fundamental step in which it differs from other materials which do not show DESemission following the model I have outlined. J. Roth: Measurements have been made in collabo ration with ORNL on the radiation enhanced subliand simultaneous mation during Ar + bombardment Ti evaporation. The enhanced sublimation yield decreased drastically at Ti fluxes yielding a steady state Ti concentration of 10 at.% in the graphite surface. A stoichiometric TiC phase was not necessary for the reduction of the enhanced sublimation yield. V. Philipps: Thank you for this correction. I think that the observed suppression of DES by only 10% titanium in the surface is an important observation and is worth being investigated further in the future, including other doping materials. H. Wiedersich: Is any information on the effect of surface orientation on the DES of graphite available ? V. Philipps: According to my knowledge only one attempt has been made to investigate the dependence of DES on the orientation, but no difference was found within the experimental resolution. Please note that the mean differential range of the interstitials is rather short (IO nm) so that the interstitials easily reach the surface.