Power Extraction Research Using a Full Fusion Nuclear Environment G. L. Yoder, Jr. Y. K. M. Peng Oak Ridge National Laboratory Oak Ridge, TN Presentation at a ReNeW Community Workshop: Harnessing Fusion Power and Taming the Plasma Material Interface Themes UCLA, March 2 - 6, 2009

2Managed by UT-Battelle for the U.S. Department of Energy Greenwald Report Identified 7 Scientific Issues in Fusion Power Extraction 1.High surface heat flux and high peaking factors 2.Complex volumetric heating source 3.Strong impact of Electromagnetic Field on heat transfer 4.Large temperature and stress gradients 5.Compatibility with the fuel cycle 6.Complex geometry 7.Evolving material properties Several physics topics lend themselves to ex-reactor testing – especially if scaled Some physics will be very difficult or impossible to reproduce without reactor testing The combination of these issues cannot be reproduced without reactor tests

3Managed by UT-Battelle for the U.S. Department of Energy Successful ITER TBM Tests will Develop a Significant Knowledge Base for Power Extraction Components* TBM testing leading to ITER – Small scale tests aimed at examining individual phenomena – structural, thermal, manufacturing, etc. – Large scale ex-reactor testing to establish performance, reliability, safety, etc. Testing in ITER will provide relevant: magnetic fields surface heat fluxes volumetric heating tritium environment neutron flux (but < DEMO) Testing is intended to: Validate thermal performance predictions Validate tritium breeding predictions, recovery process, and inventories Validate structural performance under combined fields *Partially extracted from ITER TBWG documents

4Managed by UT-Battelle for the U.S. Department of Energy A Significant Gap in Power Extraction Component Research Will Still Exist Between ITER and DEMO Power extraction/production not an objective of ITER – Main ITER blankets and diverters are water cooled ITER duty cycle is limited – 400s plasma, 1400s 0 power dwell, 8 cycles per day ITER has lower neutron flux than DEMO (0.78 vs. 2.5 MW/m 2 ) ITER has a very low neutron fluence compared to DEMO ITER will cannot develop reliability information under long term continuous operation that will be required for DEMO Remote handling of power extraction components in ITER will not be designed to achieve availability levels required for DEMO

5Managed by UT-Battelle for the U.S. Department of Energy A Variety of Efforts will be Needed to Bridge the ITER to DEMO Gap Continued development of analytical methodologies to combine applicable physics and develop optimized component designs Ex-reactor testing and test facilities will be needed to benchmark design and safety methodologies – Selection, Extension, and continued development of blanket designs for DEMO – Prototypic diverter systems – coolants, geometries, etc. – Integration of blanket power extraction systems, tritium breading, and tritium recovery systems, etc. – Testing of heat exchanger systems under prototypic thermal and structural conditions – Reliability testing of power conversion components – Etc. In-reactor testing will be required to address issues unique to the DEMO fusion environment – Interaction of multiple physics processes in a steady state environment Materials irradiation Transients Geometric alignment Multidimensional thermal loading Etc. – Benchmark multi-physics design codes needed for extension to DEMO and develop realistic methodologies for design optimization – Steady state tritium production, retention and transport Coolant stream impurity levels and composition

6Managed by UT-Battelle for the U.S. Department of Energy Full Fusion Environment in an Experimental Facility Will Allow Required Development of Power Extraction Components Before DEMO More instrumentation than possible in commercial or near-commercial facility – Individual blanket/diverter performance characterization – temp/flow/tritium/etc. – Tritium inventory mapping – development of process system control, accountability, etc. Flexible enough to accommodate multiple component designs – Multiple blanket and diverter configurations – Staged component testing – eg. 300 o C → 500 o C → 700 o C → 1100 o C Designed to accept and recover from failures – Some failure mechanisms will depend on a combination of environmental factors Allows component reliability information to be developed in appropriate environment – Long term testing of components, remote handling equipment, and maintenance processes for each prospective component design – Provides data for ultimate down selection of process and component designs Develop appropriate data base for regulatory acceptance – Regulator for DEMO will require safety codes to be benchmarked with prototypic data some of which will need to be near operating environment Power conversion systems could be incorporated in some blanket designs to support technical arguments and provide marketing support Provide operational experience needed to establish DEMO design and operating strategies