1. Fusion power: Visions and the Development Path in the ITER Era
Farrokh Najmabadi
University of California San Diego
Plasma Seminar
University of Wisconsin Madison
October 31, 2006
Electronic copy:
ARIES Web Site:

2. Do we have an attractive vision for the final product?

3. Fusion physics & technology Low-activation material
Elements of the Case for Fusion Power Were Developed through Interaction with Representatives of U.S. Electric Utilities and Energy Industry
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
Reliable, available, and stable as an electrical power source
Have operational reliability and high availability
Closed, on-site fuel cycle
High fuel availability
Capable of partial load operation
Available in a range of unit sizes
Fusion physics & technology
Low-activation material

4. A dramatic change occurred in 1990: Introduction of Advanced Tokamak
Our vision of a fusion system in 1980s was a large pulsed device.
Non-inductive current drive is inefficient.
Some important achievements in 1980s:
Experimental demonstration of bootstrap current;
Development of ideal MHD codes that agreed with experimental results.
Development of steady-state power plant concepts (ARIES-I and SSTR) based on the trade-off of bootstrap current fraction and plasma b (1990)
ARIES-I: bN= 2.9, b=2%, Pcd=230 MW
Last decade: Reverse Shear Regime
Excellent match between bootstrap & equilibrium current profile at high b.
Requires wall stabilization (Resistive-wall modes).
Internal transport barrier.

5. Advanced Tokamak lead to attractive power plants
1st Stability,
Nb3Sn Tech.
ARIES-I’
Major radius (m)
8.0
b (bN)
2% (2.9)
Peak field (T) 16
Avg. Wall Load (MW/m2)
1.5
Current-driver power (MW)
237
Recirculating Power Fraction
0.29
Thermal efficiency
0.46
Cost of Electricity (c/kWh) 10
High-Field
Option
ARIES-I
6.75
2% (3.0) 19
2.5
202
0.28
0.49
8.2
ARIES-RS
5.5
5% (4.8) 16 4 81
0.17
0.46
7.5
Reverse Shear
Option
ARIES-AT
5.2
9.2% (5.4)
11.5
3.3 36
0.14
0.59 5
Approaching COE insensitive of power density
Reduced COE mainly due to advanced technology

6. Advanced Brayton Cycle Parameters Based on Present or Near Term Technology Evolved with Expert Input from General Atomics*
Recuperator
Intercooler 1
Intercooler 2
Compressor 1
Compressor 2
Compressor 3
Heat
Rejection HX W
net
Turbine
Blanket
Intermediate 5' 1 2 2' 3 8 9 4 7' 9' 10 6 T S 5 7
Divertor
LiPb
Coolant
He Divertor 11
Key improvement is the development of cheap, high-efficiency recuperators.

7. ARIES-ST Featured a High-Performance Ferritic Steel Blanket
Originally developed for ARIES-ST, further developed by EU (FZK).
Typically, the coolant outlet temperature is limited to the max. operating temperature of structural material (550oC for ferritic steels).
A coolant outlet temperature of 700oC is achieved by using a coolant/breeder (LiPb), cooling the structure by He gas, and SiC insulator lining PbLi channel for thermal and electrical insulation.

8. ARIES-AT2: SiC Composite Blankets
Outboard blanket & first wall
Simple, low pressure design with SiC structure and LiPb coolant and breeder.
Simple manufacturing technique.
Very low afterheat.
Class C waste by a wide margin.
LiPb-cooled SiC composite divertor is capable of 5 MW/m2 of heat load.
Innovative design leads to high LiPb outlet temperature (~1,100oC) while keeping SiC structure temperature below 1,000oC leading to a high thermal efficiency of ~ 60%.

9. Use of High-Temperature Superconductors Simplifies the Magnet Systems
HTS does offer operational advantages:
Higher temperature operation (even 77K), or dry magnets
Wide tapes deposited directly on the structure (less chance of energy dissipating events)
Reduced magnet protection concerns
Inconel strip
YBCO Superconductor Strip Packs (20 layers each)
8.5
430 mm
CeO2 + YSZ insulating coating
(on slot & between YBCO layers)
Epitaxial YBCO
Inexpensive manufacturing would consist of layering HTS on structural shells with minimal winding!

10. Estimated Cost of Electricity (c/kWh)
Our Vision of Magnetic Fusion Power Systems Has Improved Dramatically in the Last Decade, and Is Directly Tied to Advances in Fusion Science & Technology
Major radius (m)
Estimated Cost of Electricity (c/kWh)
Approaching COE insensitive of power density
Advanced Technologies is the main lever in reducing fusion power plant costs

11. Generated radioactivity waste is reasonable
1270 m3 of Waste is generated after 40 full-power year (FPY) of operation (~50 years)
Coolant is reused in other power plants
29 m3 every 4 years (component replacement)
993 m3 at end of service
Equivalent to ~ 30 m3 of waste per FPY
Effective annual waste can be reduced by increasing plant service life.
90% of waste qualifies for Class A disposal

12. 2) How to we get from ITER to an attractive final product

13. Integration of fusion plasma with fusion technologies
ITER
Integration of fusion plasma with fusion technologies
A 1st of the kind Power Plant!
“Fusion Power: Research and Development Requirements.”
Division of Controlled Thermonuclear Research (AEC).

14. World-wide Development Scenarios use similar names for devices with different missions!
An R&D Device
A Power Plant
CTF
Demo US
ITER + IFMIF + Base
Proto
Demo
US (1973 AEC)
Commercial
Demo
Proto
EU or Japan
Demo-Proto
Demo (R&D)
EU or Japan (Fast Track)
Combine Demo (R&D) and Proto in one device

15. What do we need to bridge the gap between ITER and attractive power plants?
With ITER construction going forward with US as a partner and increased world-wide interest and effort in developing fusion energy, it will become increasingly important that new major facilities and program in US demonstrate their contributions to developing fusion energy as a key part of their mission.
Do we have a detailed map for fusion power development?
How do we optimize such a development path?
What can we do in simulation facilities and what requires new fusion devices?
How can we utilize existing devices to resolve some of these issues?
Preparation for lunching new facilities.
Resolving issues that can make a difference in any new facilities.

16. In the ITER area, we need to develop a 5,000 ft view

17. What is the most cost-effective way to do this?
Various devices are proposed in US to fill in the data needed to proceed with a power plant
Many devices are proposed:
A device that can explore AT burning plasma with high power density and high bootstrap fraction (with performance goals similar to ARIES-RS/AT).
A device with steady-state operation at moderate Q (even D plasma) to develop operational scenarios (i.e., plasma control), disruption avoidance, divertor physics (and developing fielding divertor hardware), etc.
Volume Neutron Source for blanket testing.
Most these devices provide only some of the data needed to move to fusion power. They really geared towards one part of the problem.
Can we do all these in one device or one facility with minor changes/upgrades and a reasonable cost?
How can we utilize existing devices to resolve some of these issues?
What is the most cost-effective way to do this?

18. A holistic optimization approach should drive the development path.
Traditional Approach: Ask each scientific area (i.e., plasma, blanket, …)
What are the remaining major R&D areas?
Which of the remaining major R&D areas can be explored in existing devices or simulation facilities (e.g., fission reactors)? What other major facilities are needed?
Holistic Approach: Fusion energy development should be guided by the
requirements for an attractive fusion energy source
What are the remaining major R&D areas?
What it the impact of this R&D on the attractiveness of the final product.
Which of the remaining major R&D areas can be explored in existing devices or simulation facilities (i.e., fission reactors)? What other major facilities are needed?
Should we attempt to replicate power plant conditions in a scaled device or Optimize facility performance relative to scaled objectives

19. Fusion physics & technology Low-activation material
Elements of the Case for Fusion Power Were Developed through Interaction with Representatives of U.S. Electric Utilities and Energy Industry
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
Reliable, available, and stable as an electrical power source
Have operational reliability and high availability
Closed, on-site fuel cycle
High fuel availability
Capable of partial load operation
Available in a range of unit sizes
Fusion physics & technology
Low-activation material

20. Existing facilities fail to address essential features of a fusion energy source

21. ITER is a major step forward but there is a long road ahead.
Present Experiments

22. A holistic optimization approach should drive the development path.
Traditional Approach: Ask each scientific area (i.e., plasma, blanket, …)
What are the remaining major R&D areas?
Which of the remaining major R&D areas can be explored in existing devices or simulation facilities (e.g., fission reactors)? What other major facilities are needed?
Holistic Approach: Fusion energy development should be guided by the
requirements for an attractive fusion energy source
What are the remaining major R&D areas?
What it the impact of this R&D on the attractiveness of the final product.
Which of the remaining major R&D areas can be explored in existing devices or simulation facilities (i.e., fission reactors)? What other major facilities are needed?
Should we attempt to replicate power plant conditions in a scaled device or Optimize facility performance relative to scaled objectives

23. ARIES studies emphasize holistic R&D needs and their design implications
Traditional approach
Power control
Power and particle management
Fuel management
Maintenance
Safety
Waste
Cost
Concurrent engineering/physics
Plasma
Blankets
Divertors
Magnets
Vacuum vessel
This approach has many benefits (see below)

24. Examples of holistic issues for Fusion Power
Power & Particle management: Demonstrate extraction of power core high-grade heat, divertor power and particle handling, nuclear performance of ancillary equipment.
Fuel management: Demonstrate “birth to death” tritium management in a closed loop with self-sufficient breeding and full accountability of tritium inventory.
Safety: Demonstrate public and worker safety of the integral facility, capturing system to system interactions.
Plant operations: Establish the operability of a fusion energy facility, including plasma control, reliability of components, inspectability and maintainability of a power plant relevant tokamak.

25. Pneutron Pfusion Pa Prad Prad Pinjected Pcond Pcond
Power & particle management: Demonstrate extraction of power core high-grade heat, divertor power and particle handling, nuclear performance of ancillary equipment.
Fission:
rf antennas, magnets, diagnostics, etc.
Fusion:
Pneutron
In-vessel
Pfusion
Blanket
PFC’s
First wall Pa
Prad
Prad
edge
power
Divertor
Pinjected
Pcond
core
power
Pcond

26. A holistic approach to Power and Particle Management
Does not allow problem cannot be solved by transferring to another system:
A 100% radiating plasma transfers the problem from divertor to the first wall.
Allows Prioritization of R&D:
Systems code can be used to find power plant cost (or any other metric) as a function of divertor power handling. This leads to a “benefit” metric that can be compared to other R&D areas, for example increasing plasma b. We can then answer: should we focus on power flow or improving plasma b.
Most technologies for current experiments & ITER are NOT transferable to a power plant. Is this an optimum approach?
Solution may come from other areas:
Low recirculating power
A higher blanket thermal efficiency reducing input fusion power
This particular area may have a profound impact on next-step facilities.

27. Fuel management: Demonstrate “birth to death” tritium management in a closed loop with self-sufficient breeding and full accountability of tritium inventory.
inventory
pumps
breeder
coolant
breeder processing
coolant processing
vacuum processing
fueling
D+T
D+T+ n T
Fuel
processing

28. Fuel Management divides naturally along physical boundaries
ITER provides most of the required data.
Issues include minimizing T inventory and T accountability
(the rest)
Can & should be done in a fission facility.
Demonstrate in-situ control of breeding rate (too much breeding is bad).
Demonstrate T can be extracted from breeder in a timely manner (minimum inventory).

29. There is a need to examine fusion development scenarios in detail
Any next-step device should advance power plant features on the path to a commercial end product.
We need to start planning for facilities and R&D needed between ITER and a power plant.
Metrics will be needed for cost/benefit/risk tradeoffs
An integrated, “holistic” approach provides a path to an optimized development scenario and R&D prioritization.
We should consider the needs of next-step facilities in the R&D in current facilities as well as initiating R&D needed to ensure maximum utilization of those facilities.
For the next three years, the ARIES program will consider these issues.

30. Further Thoughts

31. We Should Be Ready to Accelerate Fusion Development!
With the industrialization of the emerging nations, the demand for energy will increase by many folds.
Few options available:
Energy Efficiency Only has reduced the growth rate
Fossil fuels Global Warming
Renewable Intermittency, high cost, environmental impact
Nuclear (fission) Waste disposal, proliferation
There would be a large increase in energy R&D in the next 5-10 years.
We need to be prepared to put fusion option on the table.

32. What can we do to accelerate fusion development?
We will not be able to compete with Asian Superconducting tokamaks and ITER in a timely manner.
We can leap-frog the rest of the world by focusing on the pace-setting issues – Plasma and fusion technologies
We can aim at a Fusion Pilot Plant: A steady-state demonstration device with the capability to produce copious amount (> 100 MW) of fusion power and demonstrate all aspect of a fusion power plant.
This device does NOT have to be a net energy producer! (Q =1-2 is enough!)
It would resolve the remaining issues of fusion plasma physics.
It would set the necessary technical/regulatory data base for moving towards a fusion power plant.

33. Are we ready to accelerate fusion development?
We probably have the plasma basis to proceed with such a device.
We do NOT have the Engineering Sciences basis to move forward.
We do NOT have the people! (no students in fusion technology area)
Proposal: A Concept Exploration Program for Fusion Engineering Sciences:
Small Grants, involve as many universities as possible.
Clear goals and milestones, reward performers and drop non-performers.
This will allow a new generation of fusion scientists to come forward to take the leadership of this area.

34. An Example of Fusion Engineering Sciences Research in Universities

35. T-Tube Divertor Geometry
Helium Pressure = 10 MPa
Inlet Temperature = 873 K
Exit Temperature = 950 K
Flow Rate/length = 0.2 kg/s.m
85 mm
25 mm
D = 15 mm
* From T. Ihle (FZK) and R. Raffray (UCSD)

36. Experimental Flow Loop
Inlet port
Outlet port
TC 1
TC 9
Plugged end (single inlet)

37. Predicted Performance – Flow Field (Double Inlet)
Max velocity: 93 m/s
Operating pressure: 14.3 PSI (98 kPa)
Pressure drop: 0.54 PSI (3700 Pa)

38. Predicted Performance – Heat Transfer Coefficient (Double Inlet)
Max Heat Transfer Coefficient:
850 W/m2k (Standard Wall Functions)

39. Experimental Results (two inlets) Temperature & Heat Transfer Coefficient
Location 5