1. Generation IV Systems: Key Technological Challenges for Fission Reactors and What It Means for Fusion
David Petti
R&D Technical Director
Next Generation Nuclear Plant
Deputy Director Fusion VLT
APS-DPP
Oct. 31, 2006

2. Overview
A number of Generation-IV nuclear systems are under study worldwide
There are many technology challenges that these advanced fission reactors (Generation IV) and fusion have in common.
Examples of the overlap are:
power conversion technologies,
materials corrosion: high temperature materials and coolant compatibility
welding and joining technologies,
materials response under neutron irradiation,
first-principles materials modeling,
high temperature materials design rules, and
tritium/hydrogen behavior in materials
The fusion community can help advance its technology development activities by actively engaging and leveraging much of the common cross-cutting research.

3. The National Energy Policy Endorses Nuclear Energy as a Major Component of Future U.S. Energy Supplies
Existing Nuclear Plants
Expedited NRC licensing of advanced reactors
Update and relicense nuclear plants
Nuclear energy’s role in improved air quality
Geologic repository for nuclear waste
Price-Anderson Act renewal
New Nuclear Plants
Advanced fuel cycle/pyroprocessing
Next-generation advanced reactors
Reprocessing
International collaboration
Cleaner, more efficient, less waste, more proliferation-resistant

4. Generation IV Technology Roadmap
Identifies systems that are deployable by 2030 or earlier
Over 100 concepts were submitted for evaluation
Six ‘most promising’ systems that offer significant advances towards:
Sustainability
Economics
Safety and reliability
Proliferation resistance and physical protection
Each system has R&D challenges. None are certain of success.
Summarizes R&D activities and priorities for the systems and lays the foundation for Generation IV R&D program plans
Very-High-Temperature Reactor System (safety, hydrogen production)
Lead-Cooled Fast Reactor System (sustainability, safety)
Gas-Cooled Fast Reactor System (sustainability,economics)
Supercritical-Water-Cooled Reactor System (economics)
Molten Salt Reactor System (sustainability)
Sodium-Cooled Fast Reactor System (sustainability)

5. Generation IV International Forum (GIF)
Brings international perspective:
Generation IV Technology Goals
Evaluation of Systems and R&D
Endorses key elements:
Six Gen IV Systems announced Sep ‘02
Generation IV Roadmap
Identifies areas of multilateral collaborations and establishes guidelines for collaborations
Regularly reviews progress on collaborations
Observers from:
International Atomic Energy Agency
OECD/Nuclear Energy Agency
European Commission
Nuclear Regulatory Commission
Department of State
Chartered July, 2001
South Korea
U.S.A.
Argentina
Brazil
Canada
France
Japan
South Africa
United Kingdom
Switzerland
European Union

6. Molten Salt Reactor (MSR)
Characteristics
Fuel: liquid Na, Zr, U and Pu fluorides
700–800°C outlet temperature
1000 MWe
Low pressure (<0.5 MPa)
Benefits
Waste minimization
Avoids fuel development
Proliferation resistance through low fissile material inventory

7. Sodium-Cooled Fast Reactor (SFR)
Characteristics
Sodium coolant
550°C Outlet Temp
150 to 500 MWe
Metal fuel with pyro processing / MOX fuel with advanced aqueous
Benefits
Consumption of LWR actinides
Efficient fissile material generation

8. Lead-Cooled Fast Reactor (LFR)
Characteristics
Pb or Pb/Bi coolant
550°C to 800°C outlet temperature
120–400 MWe
15–30 year core life
Benefits
Distributed electricity generation
Hydrogen and potable water
Cartridge core for regional fuel processing
High degree of passive safety
Proliferation resistance through long-life cartridge core

9. Gas-Cooled Fast Reactor (GFR)
Characteristics
He or supercritical CO2 coolant
High (>800 °C ) outlet temperature
High thermal efficiency (>40%)
MWth
Several fuel options and core configurations
Benefits
Utilize fuel efficiently through high energy extraction and recycle
Destroy long-term radioisotopes efficiently

10. Supercritical-Water-Cooled Reactor (SCWR)
Characteristics
Water coolant at supercritical conditions, single phase fluid
550°C outlet temperature
1700 MWe
Simplified balance of plant
Benefits
Efficiency near 45% with excellent economics
Thermal or fast neutron spectrum

11. Very-High-Temperature Reactor (VHTR)
Characteristics
He coolant (inert, single-phase)
1000°C outlet temperature
600 MWe
Solid graphite block core based on GT-MHR
Benefits
High thermal efficiency
Hydrogen production
Process heat applications
High degree of passive safety

12. DOE has selected the VHTR system for the Next Generation Nuclear Power (NGNP) Project. The NGNP is the Leading Generation IV Technology for Near-Term Demonstration in Idaho
The purpose of the NGNP Project is to demonstrate emissions-free nuclear-assisted electricity and hydrogen production by ~

13. Power Conversion Technology
Prismatic Very High Temperature Reactor: Brayton Cycle for Power Conversion
ARIES-AT: Brayton Cycle for Power Conversion

14. Coolant/Structural Material Corrosion
Lead cooled fast reactor: corrosion with ferritic steel
US ITER TBM: PbLi corrosion with advanced ferritic steel

15. Coolant/Structural Material Corrosion
Very High Temperature Reactor: He impurities effects on high temperature structural materials (Superalloy systems)
US ITER TBM: Influence of He impurities effects on high temperature structural material (Superalloy systems)

16. Welding/Joining Technology
Ferritic steels are used in both advanced fission plants (sodium fast reactor, Pb fast reactor) and ITER Test Blanket Modules
High temperature Ni superalloys are currently envisioned for heat exchangers at high temperature (> 900°C)
Welding and joining technologies are needed for each system
Post-weld heat treatments on componments to get proper microstructure
Joints in heat exchangers and other components
Dissimilar materials weld issues

17. Material Response Under Irradiation
Both fission and fusion systems will be subject to neutron damage
Key materials common to both systems include:
Advanced ferritic steels (improved creep resistance)
Cladding in fast reactors
Blanket structure in fusion
SiC composites
Control rod guide tubes in very high temperature reactors
Flow channel inserts in ITER TBM and blanket structure in ARIES-AT
Slight differences exist in temperatures and level of damage. Major difference is He/dpa expected in fission versus fusion

18. First Principles Materials Modeling
First principles modeling of material damage phenomena occurring over a range of both space and time scale is recognized as an important element of bridging gaps and filling in uncertainties in material response under irradiation in both fission and fusion systems

19. High Temperature Materials Design Rules
Because of the impact of high temperature on thermal efficiency of both fission and fusion systems, there is a strong push to develop materials that can accommodate high temperature operation ( °C)
VHTR for fission
DEMO embodiment of ITER TBM and ARIES-AT for fusion
High temperature design rules (ASME code case) that account for behavior in nuclear environment and at high temperature are needed
US VHTR personnel are starting this activity

20. Tritium permeation barriers are needed to ensure that at high temperatures permeation through the heat exchanger can meet safety limits of ~ 1-10 Ci/day
Very High Temperature Reactor: ternary fission produces about 1 to 2 g of tritium at equilibrium. A key issue is to limit permeation into hydrogen product in hydrogen plant
Fusion strives to keep blanket inventory to g. High partial pressure of tritium in some blankets makes control of permeation difficult

21. Summary
There are many technology challenges that advanced fission reactors (Generation IV) and fusion have in common.
The fusion community can help advance its technology development activities by actively engaging and leveraging much of the common cross-cutting research.
Decrease in resources for fusion technology makes this more difficult
More integration of the fission and fusion technology communities in the US would help