1. RAMI Requirements for DEMO, Gaps, and Thrusts 03 March 2009 RAMI Panel Members: Mohamed Abdou (UCLA), Tom Burgess (ORNL), Lee Cadwallader (INL), Wayne Reiersen (PPPL), John Sheffield (UT), John Smith (GA), Les Waganer (Boeing – retired)

2. Identifying gaps and thrusts 1.What does DEMO have to do? 2.Where do we have to be before proceeding with DEMO? 3.Where will we be after ITER? 4.What are the gaps between ITER and DEMO? 5.What are the research thrusts needed to fill those gaps?

3. What does DEMO have to do? Primary Requirement. Availability is adequately high (A=50-75%) for the power producers to commit to building a commercial fusion plant. Supporting Requirements –Integrated design. An integrated design for the tokamak core components and balance of plant which provides adequate reliability, maintainability, availability, and inspectability while meeting performance requirements –Component reliability and maintainability. Component reliability and maintainability adequate to provide high availability. Probability of an investment-critical failure adequately low. –Component lifetimes. Component lifetimes are adequate for achieving high availability. –Inspection and maintenance system. An effective inspection and maintenance system that is proficient in monitoring equipment health, detecting and isolating failures, providing spares, effecting and verifying repair, refurbishing failed components, and processing radwaste. Many of these activities will have to be performed remotely. –Disruptions and off-normal events. DEMO must be tolerant of any disruptions or off- normal events which could occur.

4. Need a credible, low risk approach for meeting the availability requirement before proceeding with DEMO Integrated design. A DEMO-relevant integrated design approach for the tokamak core components and balance of plant has been developed and is projected to provide adequate performance, reliability, maintainability, availability, and inspectability. Component reliability and maintainability –Database developed to identify failure modes and predict component failure rates and repair times For critical components requiring low failure rates, long testing or operating times are required to develop estimates that are statistically meaningful The extent of the necessary R&D depends upon the required availability. –Component lifetime, failure rate, and repair time projections consistent with representative reliability and availability goals –Technologies and design options chosen which have demonstrated the ability to meet RAMI goals.

5. Need a credible, low risk approach for meeting the availability requirement before proceeding with DEMO Component lifetimes –High temperature, high fluence in-vessel materials and components qualified for use in an operational environment –Proven blanket and fuel cycle designs capable of meeting tritium self-sufficiency requirements and tritium inventory constraints derived from safety with acceptable lifetimes –Proven first wall and divertor designs capable of managing high heat fluxes with acceptable lifetimes –Proven heating and current drive system designs capable of meeting heating, current drive, current profile control, and plasma rotation requirements with acceptable lifetimes. Reliable coupling for RF systems will likely be needed to avoid unwanted H- to L-mode transitions. RF launchers must withstand plasma heat loads and EM loads due to disruptions (unless eliminated) –Proven, simple control diagnostics capable of surviving the harsh environment with long lifetimes

6. Need a credible, low risk approach for meeting the availability requirement before proceeding with DEMO Inspection and maintenance system –Proven concepts for monitoring equipment health and detecting and isolating failures. For instance, embedded sensors in key components might be used to assess component health, performance, lifetime, and predicted failure conditions. –Proven maintenance system concept –Clear requirements and constraints for the design of equipment to be remotely maintained need to be established Disruptions and off-normal events –Two possible success paths: [1] Potential for disruptions or other potentially damaging off-normal events (ELMs, unwanted H- to L-mode transitions, uncontrolled vertical excursions, runaway electrons) eliminated or [2] plasma facing components demonstrated to be tolerant of such events at the frequency expected –Requires demonstration with a self-sustaining plasma (little external input, a pre- requisite for high-Q operation)

7. ITER will provide valuable information for DEMO, but not all the information required Integrated design –ITER will provide critical experience for developing a DEMO-relevant, integrated design but it does not represent a DEMO-relevant, integrated design. –Valuable experience with ex-vessel systems such as magnets and cryo systems which may be prototypical of DEMO will be gained –Valuable information on the operating environment for plasma facing components will be gained, including heat loss channels, characterization of the SOL, and avoidance and mitigation of disruptions and ELMs –Valuable information on divertor heat loads including techniques for minimizing peak heat fluxes (e.g. radiative divertor operation) will be gained –Valuable information on long pulse, self-sustained (Q~10) plasma control and operation will be gained –Remote handling design and practice will be greatly enhanced –Experience in the management of DT fuel cycle systems will be gained –TBMs will have tested blanket modules to screen concepts, validate prompt response, analytical models and early-life effects; but not sufficient fluence-dependent behavior

8. ITER will provide valuable information for DEMO, but not all the information required Component reliability and maintainability –ITER can potentially provide much reliability and maintainability data that will be necessary (but not all that is needed) for the design of DEMO –Three types of data are needed: plant engineering data, component or system failure reports, and operating reports. –This data is needed to project the reliability and maintainability parameters for DEMO –It is important to collect data from other experimental and test facilities –Standard terminology and information to be included in the data sets should be established

9. ITER will provide valuable information for DEMO, but not all the information required Component lifetimes –ITER will provide limited opportunities for significantly testing component lifetimes –ITER will not test in-vessel components to fluence levels which would constitute a test for DEMO-relevant component designs. –ITER will not provide very long operating time for systems which only operate during plasma operation. The fluence objective of 0.3 MW-a/m 2 corresponds to an integrated burn time of ~9 months. But, for systems which operate 24/7 (TF coils, cryo systems, vacuum systems, etc), the 20 year life may be a significant test. –ITER will have 30,000 plasma pulses which are likely to be more than the DEMO requirement. This may be a significant test for systems which only operate as part of plasma startup or shutdown.

10. ITER will provide valuable information for DEMO, but not all the information required Inspection and maintenance system –ITER will provide an opportunity to advance our readiness to [1] design an effective inspection and maintenance system for DEMO and [2] design a tokamak for remote maintainability. –ITER is planning to implement reliability-centered maintenance which fundamentally is a program to monitor equipment failures and health, replace components at maintenance opportunities before they fail, and redesign components to reduce failures or shorten repair times. –ITER will develop and refine a system for the full remote maintenance cycle including detecting and isolating failures, removing and replacing components remotely, transporting components between the tokamak and hot cell facility, refurbishing failed components, and processing radwaste. It will be an excellent remote handling testbed. –The ITER experience (good and bad) will provide useful information to identify tokamak design features to facilitate remote maintainability and to determine the optimum level of modularization.

11. ITER will provide valuable information for DEMO, but not all the information required Disruptions and off-normal events –The ITER experience will provide a critical test on disruption and ELM avoidance and mitigation –The frequency and severity of disruptions and ELMs on ITER will be important input to the design of plasma facing components on DEMO

12. Significant gaps exist between ITER and being ready for DEMO Integrated design –Gap: There is no iterative integration activity to process what we learn from ITER and other experiments and test activities; apply it to develop a credible, low risk design for DEMO; and define DEMO support requirements for interim experiments and test activities to underpin (or modify) that design. –Gap: Order of magnitude improvements in the time to perform in-vessel maintenance and reduce outage times will be required in going from ITER to DEMO –Thrust: Initiate an integrated design activity for DEMO

13. The Integrated Design Thrust Process what we learn from ITER and other experiments and test facilities Develop a credible, low risk, attractive design for DEMO. In the context of RAMI, this design would have a credible, low risk approach to achieve and demonstrate the availability required for DEMO to be attractive. The integrated design would include the tokamak systems, plant systems, maintenance systems, and facilities. Studies would be performed to determine the test and development activities (and associated cost) required to meet the availability goal. (The higher the goal, the more time and resources will be required to achieve it.) The DEMO design would be developed to a level of detail at which the feasibility of the design (including RAMI performance) could be evaluated and safety assessments performed – much greater detail than ARIES Trade studies would be conducted to evaluate configuration options and component design alternatives. Results would be fed back to supporting experiments and test activities to provide needed focus. A clear map would be developed for coordinating design integration and development and testing activities, and down-selecting between design options. At the time when DEMO design was initiated, there would be a well defined set of design requirements and a well documented, low risk design approach for meeting those requirements

14. Significant gaps exist between ITER and being ready for DEMO Component reliability and maintainability –Gap: There is no coordinated effort to gather RAMI-related data from ITER and other experimental and test facilities for the purpose of improving designs specific to DEMO –Thrust: Initiate an international RAMI data collection system through ITER that can be a pattern for existing and future experimental and test facilities. The purpose of this system is to provide the information needed to improve DEMO design, in particular with regard to RAMI performance, drawing on as wide an experience base as possible Asian tokamaks would provide a new source of important data –Gap: ITER will not provide the failure mode and failure rate data for prototypical nuclear (in-vessel) components needed to design DEMO –Thrust: Perform R&D for nuclear components including testing in laboratory experiments, and aggressive reliability growth program on component test facilities to identify failure modes, failure rates and improve reliability.

15. DEMO Availability of 50% Requires Blanket Availability ~88%, MTBF > 11y Table based on information from J. Sheffield’s memo to the Dev Path Panel Assumes 0.2y per year for scheduled maintenance

16. Significant gaps exist between ITER and being ready for DEMO Component lifetimes –Gap: ITER will not test in-vessel components (blankets, divertor, diagnostics, heating system front ends) to fluences that are representative of DEMO, nor will it provide substantial operating time for components which are only on (stressed) during plasma operation –Thrust: Design, construct, and operate a Component Test Facility/Fusion Development Facility(ies) which will provide a platform for operating DEMO- relevant component designs in an operating environment which is similar to DEMO for times that provide substantial fluence and operating times for in-vessel components (10x ITER) Materials and components selected for use in the CTF/FDF should be qualified in test facilities CTF/FDF should be designed to provide an operating environment similar to DEMO for in-vessel components CTF/FDF in-vessel components designs should be prototypical of designs envisioned for DEMO where practical Technology development activities (materials, blanket technology) will necessarily precede the design of CDF/FDF in-vessel components

17. Significant gaps exist between ITER and being ready for DEMO Inspection and maintenance system –Gap: ITER will be a second generation RH system (with JET as the first generation) but will not provide the level of performance required for DEMO –Thrust: In order to achieve its fluence objectives, CTF/FDF will require an effective maintenance and inspection system. Designing, constructing, and operating this system should provide a major improvement in our readiness to [1] design an effective inspection and maintenance system for DEMO and [2] design a tokamak for remote maintainability. The CTF/FDF maintenance and inspection system will operate in a higher radiation field than on ITER, although not as high perhaps as in DEMO The outage times for in-vessel operations have to be improved dramatically, perhaps by an order of magnitude An integrated system health management system for all plant systems is needed to assess component health, performance, lifetime, and predicted failure conditions to schedule future scheduled maintenance actions.

18. Significant gaps exist between ITER and being ready for DEMO Disruptions and off-normal events –Gap: There is a large step from ITER to DEMO. The ITER experience on disruption and ELM avoidance and mitigation would require large extrapolation to DEMO. –Thrust: CTF/FDF operation will reduce the extrapolation to DEMO and provide a good test of [1] our ability to avoid and mitigate off-normal events [2] the tolerance of plasma facing components to off-normal events such as disruptions and ELMs and [3] the design requirements for those components.

19. Three thrusts have been identified to fill the gaps between what ITER will provide and DEMO needs 1.Initiate an integrated design activity for DEMO 2.Initiate an international RAMI data collection system through ITER that can be a pattern for existing and future experimental and test facilities 3.Design, construct, and operate a Component Test Facility/Fusion Development Facility(ies) which will provide… –A platform for operating DEMO-relevant component designs, particularly nuclear components, in an operating environment which is similar to DEMO for times that provide substantial fluence and operating times for in-vessel components –Data on failure modes, effects, and rates and mean time to replace/fix components. Reliability growth program must be aggressive including design/test/fail/analyze/improve programs aimed at improving reliability and safety. –A major improvement in our readiness to [1] design an effective inspection and maintenance system for DEMO and [2] design a tokamak for remote maintainability –A good test of [1] our ability to avoid and mitigate disruptions and off-normal events [2] the tolerance of plasma facing components to such events and [3] the design requirements for those components. –Operation of the CTF/FDF should be preceded and complemented by testing in laboratory experiments and operation of non-DT experiments

20. RAMI gaps and research thrusts Gaps Integrated design activity RAMI data collection system Testing and demonstration activities There is no iterative integration activity to process what we learn from ITER and other experiments and test activities; apply it to develop a credible, low risk design for DEMO; and define DEMO support requirements for interim experiments and test activities to underpin (or modify) that design. Order of magnitude improvements in the time to perform in-vessel maintenance and reduce outage times will be required in going from ITER to DEMO There is no coordinated effort to gather RAMI-related data from ITER and other experimental and test facilities for the purpose of improving designs specific to DEMO. ITER will not provide the failure mode and failure rate data for prototypical nuclear (in-vessel) components needed to design DEMO ITER will not test in-vessel components (blankets, divertor, diagnostics, heating system front ends) to fluences that are representative of DEMO, nor will it provide substantial operating time for components which are only on (stressed) during plasma operation ITER will be a second generation, RH system (with JET as the first generation) and will not provide the level of performance required for DEMO There is a large step from ITER to DEMO. The ITER experience on disruption and ELM avoidance and mitigation would require large extrapolation to DEMO.