US/Japan Workshop on Fusion Power Plant Studies A methodology for evaluating progress toward an attractive fusion energy source M. S. Tillack, L. M. Waganer US/Japan Workshop on Fusion Power Plant Studies 5-7 March 2008

Why do we need a methodology for evaluating progress? Metrics are needed to quantify progress and the value of fusion facilities In addition to individual facilities, a method is needed to compare alternative pathways (using cost, risk, benefit) in an objective and quantitative manner DOE and the Greenwald subpanel of FESAC (”Priorities, gaps and opportunities: towards a long-range strategic plan for magnetic fusion energy”) also recognizes the need for metrics (http://www.ofes.fusion.doe.gov/fesac.shtml) ?

The EU is also pursuing an approach to evaluate current technology readiness

The US Government Accountability Office (GAO) encourages “a disciplined and consistent approach for measuring technology readiness” Technology Readiness Levels represent a systematic methodology that provides an objective measure to convey the maturity of a particular technology. They were originally developed by NASA, but with minor modification, they can be used to express the readiness level of just about any technology element. The Department of Defense has adopted this metric to evaluate the readiness levels of new technologies and guide their development to the state where they are considered “Operationally Ready”. The Department of Energy has adopted the use of TRL’s in their evaluation of the GNEP program. Can fusion energy benefit from this approach to develop the technologies needed for Demo?

Generic description of readiness levels TRL Category Generic Description 1 Concept Development Basic principles observed and formulated. 2 Technology concepts and/or applications formulated. 3 Analytical and experimental demonstration of critical function and/or proof of concept. 4 Proof of Principle Component and/or bench-scale validation in a laboratory environment. 5 Component and/or breadboard validation in a relevant environment. 6 System/subsystem model or prototype demonstration in relevant environment. 7 Proof of Performance System prototype demonstration in an operational environment. 8 Actual system completed and qualified through test and demonstration. 9 Actual system proven through successful mission operations.

Characteristics of TRL’s Generic Description Characteristics of TRL 1 Basic principles observed and formulated. Pure research. Basic properties. Does not require a specific application. 2 Technology concepts and/or applications formulated. Practical application of ideas identified. Could be speculative. 3 Analytical and experimental demonstration of critical function and/or proof of concept. Development has begun. Proof of concept obtained. Demonstration of an experimental process in the lab, concept-specific modeling. 4 Component and/or bench-scale validation in a laboratory environment. Concepts from TRL2 integrated into a low-fidelity version. A “playable” demonstration. 5 Component and/or breadboard validation in a relevant environment. Alpha version: demonstration under real-life conditions or a decent simulation, high degree of scaling, low degree of integration. 6 System/subsystem model or prototype demonstration in relevant environment. Beta version of system: relevant environment, small degree of scaling, moderate degree of integration, higher management confidence

Characteristics of TRL’s, cont’d. Generic Definition Characteristics of TRL 7 System prototype demonstration in an operational environment. Full system prototype in a relevant environment. 8 Actual system completed and qualified through test and demonstration. Actual system (not a prototype) qualified through test and demonstration. Product ready for full implementation. 9 Actual system proven through successful mission operations. Product in use. Actual system operated successfully. Final stage of development. Expansions or upgrades require separate TRL’s. GAO recommendation: “Direct DOE Acquisition Executives to ensure that projects with critical technologies reach a level of readiness commensurate with acceptable risk – analogous to TRL 7 – before deciding to approve the preliminary design and commit to definitive cost and schedule estimates, and at least TRL 7 or, if possible, TRL 8 before committing to construction expenses.

Example of TRL’s for GNEP*: fast reactor spent fuel processing Description 1 Concept Development Concept for separations process developed; process options (e.g., electrolyte composition, process equipment) identified; separations criteria established. 2 Calculated mass-balance flowsheet developed; scoping experiments on process options completed successfully with simulated advanced recycling reactor spent fuel; preliminary selection of process equipment. 3 Bench-scale batch testing with simulated advanced recycling reactor spent fuel completed successfully; process chemistry confirmed; reagents selected; preliminary testing of equipment design concepts done to identify development needs; complete system flowsheet established. 4 Proof of Principle Unit operations testing at engineering scale for process validation with simulated advanced recycling reactor spent fuel consisting of unirradiated materials; materials balance flowsheet confirmed; separations chemistry models developed. 5 Unit operations testing completed at engineering scale with actual fast reactor spent fuel for process chemistry confirmation; reproducibility of process confirmed by repeated batch tests; simulation models validated. 6 Unit operations testing in existing hot cells with full-scale equipment completed successfully, using actual fast reactor spent fuel; process monitoring and control system proven; process equipment design validated.

*Global Nuclear Energy Partnership Example of TRL’s for GNEP*, continued: fast reactor spent fuel processing TRL Description 7 Proof of Performance Integrated system cold shakedown testing completed successfully with full-scale equipment (simulated fuel). 8 Demonstration of integrated system with full-scale equipment and actual advanced recycling reactor spent fuel completed successfully; short (~1 month) periods of sustained operation. 9 Full-scale demonstration with actual advanced recycling reactor spent fuel successfully completed at throughput rate consistent with annual discharge from a cluster of advanced recycle reactors at a collocated site; sustained operations for a minimum of three months. *Global Nuclear Energy Partnership

How can we apply this to fusion energy? Use criteria from utility advisory committee to derive issues (roll back) Connect the criteria to fusion-specific (design independent) technical issues and R&D needs Describe Technology Readiness Levels for the key issues Define the end goal (design) in enough detail to evaluate progress Evaluate status, gaps, facilities and pathways

Utility Advisory Committee “Criteria for practical fusion power systems” 1 J. Fusion Energy 13 (2/3) 1994. Have an economically competitive life-cycle cost of electricity Gain public acceptance by having excellent safety and environmental characteristics No disturbance of public’s day-to-day activities No local or global atmospheric impact No need for evacuation plan No high-level waste Ease of licensing Operate as a reliable, available, and stable electrical power source Have operational reliability, high availability Closed, on-site fuel cycle High fuel availability Capable of partial load operation Available in a range of unit sizes End-user (Customer) Pathways Power plant requirements Demo R&D needs R&D and facilities definition Power plant designs

The criteria for attractive fusion suggest three categories of technology readiness 2 Economic Power Production Control of plasma power flows Heat and particle flux handling High temperature operation and power conversion Power core fabrication Power core lifetime Safety and Environmental Attractiveness Tritium inventory and control Activation product inventory and control Waste management Reliable Plant Operations Plasma diagnosis and control Plant integrated control Fuel cycle control Maintenance 12 top-level issues

The intent is to be comprehensive based on functions rather than physical elements Economic Power Production Control of plasma power flows Heat and particle flux handling High temperature operation and power conversion Power core fabrication Power core lifetime Power deposition Power flows Power conversion

Example: High Temperature Operation 3 Generic Description Fusion-specific Description 1 Basic principles observed and formulated. System studies define tradeoffs and requirements on temperature, effects of temperature defined: chemistry, mechanical properties, stresses. 2 Technology concepts and/or applications formulated. Materials, coolants, cooling systems and power conversion options explored, critical properties and compatibilities defined. 3 Analytical and experimental demonstration of critical function and/or proof of concept. Data in static capsule tests and convection loops, modeling of transport phenomena, high-temperature mechanical properties measured. 4 Component and/or bench-scale validation in a laboratory environment. Capsule and loop operation at prototypical temperatures with prototypical materials for long times. 5 Component and/or breadboard validation in a relevant environment. Forced convection loop with prototypical materials, temperatures and gradients for long exposures. 6 System/subsystem model or prototype demonstration in relevant environment. Forced convection loop with prototypical materials, temperatures and gradients for long exposures integrating full power conversion systems. 7 System prototype demonstration in an operational environment. Prototype power conversion system demonstration with artificial heat source. 8 Actual system completed and qualified through test and demonstration. Power conversion system demonstration with fusion heat source. 9 Actual system proven through successful mission operations. Power conversion systems operated to end-of-life in fusion reactor with prototypical conditions and subsystems.

An evaluation of readiness requires identification of an end goal 4 For the sake of illustration, we are considering Demo’s based on mid-term and long-term ARIES power plant design concepts, e.g. Diverted, high confinement mode, tokamak burning plasma Low-temperature or high-temperature superconducting magnets He-cooled W or PbLi-cooled SiC divertors PbLi-cooled SiC or dual-cooled He/PbLi/ferritic steel blankets 800˚C (or higher) coolant outlet temperature with high-efficiency Brayton cycle Advanced power core fabrication processes Efficient autonomous maintenance

Example evaluation: High temperature operation and power conversion (DCLL) 5 3 Analytical and experimental demonstration of critical function and/or proof of concept. Data in static capsule tests and convection loops, modeling of transport phenomena, high-temperature mechanical properties measured. 4 Component and/or bench-scale validation in a laboratory environment. Loop operation at prototypical temperatures with prototypical materials for long times. Thermomechanical analysis and tests on in-vessel elements (e.g., first wall). Concept development is largely completed. Limited data on ex-vessel parts of power conversion system (e.g., HX) To achieve TRL4: Need full loop operation at high temperature in a laboratory environment This is typical of many issues; some are more advanced, but most are stuck at TRL=3

Summary The TRL approach has significant advantages Objective metrics for entire range of development Systematic for all plant elements Integrated approach Widely accepted (within the US government) We have shown that the TRL approach can be applied to fusion energy The ARIES pathways study will develop a complete methodology and evaluate example concepts TRL’s have been defined for all of the key issues We are preparing to run through an example evaluation of Demo concepts Analysis of facilities will follow