ARIES: Fusion Power Core and Power Cycle Engineering

1
Breeding Blanket Concepts for Fusion and
Materials Requirements
A. R. Raffray1, M. Akiba2, V. Chuyanov3, L.
Giancarli4, S. Malang5 1University of
California, San Diego, 458 EBU-II, La Jolla, CA
92093-0417, USA 2Blanket Engineering Laboratory,
JAERI, Naka-machi, Naka-gun, Ibaraki-ken,
311-0193 Japan 3ITER Garching Joint Work Site,
Boltzmannstr. 2, Max-Planck-Institut für
Plasmaphysik, 85748 Garching, Germany 4CEA-Saclay,
DEN/CPT, 91191, Gif-sur-Yvette,
France. 5Forschungszentrum Karlsruhe, Postfach
3640, D-76021 Karlsruhe, Germany Plenary
Presentation at ICFRM-10 Baden Baden,
Germany October 15-19, 2001
2
Outline of Presentation

• Highlight key performance and attractiveness
  parameters for breeding blanket concepts
• Summarize range of blanket concepts being
  currently considered
• Focus on MFE (although significant IFE/MFE
  synergies)
• Differentiate between class of concepts (material
  basis)
• Example description for each class of blanket
  concepts
• Highlight key material-related issues associated
  with each class of blanket concepts.
• Evolve an example classification of concepts
  based on the level of attractiveness and the
  development risk associated
• Propose a strategy for blanket development and
  supporting material RD

3
Performance and Attractiveness Factors Guide the
Blanket Design Process

• Electrical power production
• Neutron energy multiplier
• Power cycle efficiency
• Safety
• Short-term activation possibility of passive
  accommodation of off-normal scenarios without
  major consequences
• Long-term activation waste disposal
  requirements
• Availability
• Commercial reactors would require high
  availability
• Key parameters reliability, lifetime and
  downtime of the blanket system

• Design and Fabrication
• Simplicity
• Tritium
• Need for tritium self-sufficiency from blanket
  tritium breeding
• Total tritium inventory in blanket and tritium
  permeation
• Economics
• Ultimate economic measure COE
• Affected by all other factors

Design and material impact on all these
factors Require close interaction between
design and material communities
4
A Number of Different Breeding Blanket Concepts
Have Been Considered Recently

• Focus on solid wall concepts but material
  issues also applicable to thin liquid film
  concepts
• Blanket concepts can be classified based on
  the structural and breeder materials
• Ceramic Breeder Ferritic/Martensitic Steel
  Concepts (water-cooled and He-cooled)
• Pb-17Li Ferritic/Martensitic Steel Concepts
  (self-cooled and water-cooled)
• Self-Cooled Lithium Vanadium Alloy Concepts
• SiCf/SiC Based Concepts (self-cooled Pb-17Li and
  He-cooled ceramic breeder)
• Other concepts (less studied)
• Advanced concepts
• FLiBe
• For each class of concept, an example blanket
  design is described and key material issues
  discussed

5
Ceramic Breeder Be and Ferritic/Martensitic
Steel Concepts Have Been Considered with Water
and He as Coolant

• Generally good compatibility among CB, structural
  material and coolant
• No MHD effects
• CB and Be in form of sintered blocks or pebble
  beds
• Candidate breeder materials
• Ternary CB (Li4SiO4, Li2TiO3, Li2ZrO3)
• Li2O

• Example Water-Cooled Concept SSTR (JAERI)
• Modular design
• Use of reduced activation F82H steel
• Binary Be CB pebble beds
• Maximize keff and T breeding performance
• PWR-like water conditions
• Possible use of supercritical-pressure water
• 500C/25 MPa
• Increase cycle efficiency to 40-45
• Results in high stresses - use of advanced FS,
  such as Dispersion Strengthened FS, might be
  required

Struc. Tmax550C Cool. Tmax320C Cool. P 15
MPa Cycle Eff. 35 Energy Multip.
1.3 Lifetimegt10MW-a/m2
6
Key Material Issues of Ceramic Breeder Concepts

• Chemical compatibility between Be and water/air
  (hydrogen production)
• Water-cooled concept
• Accidental water/air ingress
• Possible solution to reduce H2 production Use of
  Be12Ti, which has better compatibility with
  water.
• Tritium inventory in blanket and permeation to
  coolant
• Thermo-mechanical interactions among pebbles and
  between
• pebbles and structure including neutron
  irradiation effects
• Limits on blanket lifetime due to irradiation
  damages in ceramic breeder and beryllium
• Fabrication and re-processing of the ceramic
  breeder
• Cost and waste considerations indicate need for
  re-processing of replaced blanket modules and
  re-use of the Li

7
Pb-17Li Ferritic/Martensitic Steel Concepts
Include Self-Cooled and Water-Cooled Options

• Pb-17Li is an attractive breeder material
• Good tritium breeding capability
• Possibility to replenish 6Li on-line
• Almost inert in air and relatively mild reaction
  with water
• In general limited extrapolation of blanket
  technology
• Simplest FMS and Pb-17Li concept is a self-cooled
  configuration (ARIES-ST and FZK DC concepts)
• Water-cooled option to avoid MHD effects (WCLL
  concept)

Struc. Tmax550C Pb-17Li Tmax700C He Cool.
Tmax/P 480C/14 MPa Cycle Eff. 45 Energy
Multip. 1.17 Lifetime 15MW-a/m2

• Example Dual Coolant Concept FZK DC
• Uncouple FW cooling from blanket cooling
• He coolant for more demanding FW cooling (no MHD
  uncertainties)
• Self-cooled Pb-17Li with SiCf/SiC flow channel
  insulating inserts for blanket region
• Use of ODS-steels would allow for higher
  temperature but more demanding welding
  requirements
• Compromise ferritic steel structure with mms
  ODS layer at higher temperature FW location

8
Key Material Issues for Pb-17Li
Ferritic/Martensitic Steel Concepts

• Performance of this concept is limited by
• Maximum allowable FW temperature
• Structural material compatibility with Pb-17Li (
  500 ?C)
• Possible development of advanced ODS steel to
  allow for higher temperature
• Fabrication/joining
• For water-cooled concept, need to limit tritium
  permeation from Pb-17Li to water
• Development of permeation barriers

9
Self-Cooled Lithium and Vanadium Alloy Concept

• Lithium provides the advantages of
• High tritium breeding capability,
• High thermal conductivity,
• Immunity to irradiation damage
• Possibility of unlimited lifetime if 6Li burn-up
  can be replenished
• Vanadium alloys offer advantages of
• Low after heat
• High temperature and high heat flux capability.
• Compatibility with liquid Li

Struc. Tmax700C Cool. Tmax610C Cool. P lt
1MPa Cycle Eff. 46 Energy Multip.
1.21 Lifetime 15MW-a/m2

• Example Li V Concept ARIES-RS
• Simple box-like structure
• Insulating coating on V alloy to reduce MHD
  effects
• E.g. CaO maintained by adding 0.5 Ca in Li
• Allows for low system pressure
• Multiple flow passes in the blanket provide the
  capability for FW surface heat flux 1 MW/m2

10
Key Material Issues for Lithium and Vanadium
Alloy Concept

• Insulated walls are a must to reduce MHD effects
  for acceptable pressure drop and heat transfer
• MAJOR ISSUE
• Need to develop reliable and self-healing
  insulation coating
• Compatible with low activation requirements,
  material interfaces and tritium recovery systems
  in a fusion environment
• Chemical reactivity of Li
• Radiation damage effect on V-alloy from fusion
  neutron spectrum
• Fabrication method and cost of V-alloy under the
  goal of minimizing impurities
• Joining of V-alloy to another structural material

11
Concepts Utilizing SiCf/SiC Composite as
Structural Material
SiCf/SiC offers advantages of Safety - Low
afterheat Possibility of passive accommodation
of accident scenarios (E.g. LOCA,
LOFA) - Low long term activation favorably
influences waste disposal requirement (Class
C or better) Performance - High temperature
operation possibility of high cycle hSiCf/SiC
has been considered with Self-cooled Pb-17Li
(e.g. TAURO and ARIES-AT) He-cooled CB
(ARIES-I, DREAM, A-HCPB, and A-SSTR2)
Example Self Cooled Pb-17Li SiCf/SiC
Concept ARIES-AT Simple box
design geometry Utilizes 2 cooling passes to
uncouple structure temperature from outlet
coolant temperature Reasonable design margins
as an indication of reliability
Struc. Tmax1000C Cool. Tmax1100C Cool. P
1-1.5 MPa Cycle Eff. 59 Energy Multip.
1.11 Lifetime(?) 18MW-a/m2
12
Key Material Issues for Fusion Blanket Concepts
with SiCf/SiC Composite
Major issue linked to uncertainty about
SiCf/SiC behavior and performance at high
temperature and under irradiation - Thermal
conductivity - Maximum allowable operating
temperature - Neutron irradiation
effect/Lifetime - Allowable stress - Hermeticity
(in particular for He-cooled concept) - Fabricat
ion Key issues associated with the breeders
are similar to those for other concepts
utilizing similar breeding materials
13
Other Concepts Receiving Some Degree of Attention
but Generally Less Studied Include
Advanced concepts, e.g. EVOLVE concept with Li
evaporation cooling and W alloy - Make use of
high latent heat of evaporation of Li
- Operation at Li saturation temperature of
1200C and low pressure - High heat load capable
- FW q gt 2 MW/m2 and neutron wall load gt10
MW/m2 - Key material issue qualification of W
alloy under these conditions
Struc. Tmax1300C Cool. Tmax1200C Cool. P
0.04 MPa Cycle Eff. gt55 Energy Multip.
1.2 Lifetime(?)
FLiBe concepts with Ferritic or Other Structural
Materials Advantages of FLiBe - Low
chemical activity with air and water - No MHD
effect on pressure drop for self-cooled
concepts - Compatible with most structural
materials to high temperature Issues - Material
compatibility issues with transmutation products
- Poor heat transfer Possible MHD effects on
heat transfer need turbulence - Tritium
control Limited effort on conceptual design
studies for FLiBe concepts in MFE reactors
- e.g. FFHR-2 helical-type reactor, with FLiBe
FS blanket concept
Struc. Tmax550C Cool. Tmax550C Cool. P 0.5
MPa Cycle Eff. 38 Lifetime 15MW-a/m2
14
Substantial Progress Has Been Made in
Understanding the Performance and Behavior Of
Breeder, Multiplier and Structural Materials
Over the Last 10-15 Years
Example Accomplishment Tritium inventory
predictions for ceramic breeders Tritium
transport in CB is complex process involving
several mechanisms Overly conservative T
inventory estimate in early studies in the
absence of adequate analytical tools and
fundamental property data characterization
Focused international RD program including
material fabrication and characterization,
laboratory and in-reactor purge experiments, and
fundamental and integrated model development
15
However, Many Issues Still Remain for Each Class
of Blanket Concept

• Blanket concepts with the potential for high
  performance and attractive safety features tend
  to have higher associated development risk
• Semi-qualitative subjective classification of
  different blanket concepts
• Attractiveness measure is a subjective assemblage
  of attractive features, such as cycle efficiency,
  safety, and lifetime
• Measure of development risk includes degree of
  extrapolation from current material and component
  performance and complexity and scale of effort
  required to validate the concept
• Individual classification could change over a
  certain range according to the reviewer
• However, the overall classification of choice of
  structural materials and of breeder materials is
  unlikely to vary appreciably

16
Proposed Blanket RD Strategy (1)

• The objective of blanket RD should be to lead at
  least to the development of a blanket with a
  minimum acceptable level of performance and
  attractiveness for a commercial reactor
• Lower-bound blanket performance levels which
  would still result in an acceptably attractive
  commercial fusion reactor should be developed
• Blanket concepts with the lowest development risk
  meeting these performance criteria should be
  developed and tested
• Typically medium-risk medium-performance concepts
• Representing a fall-back position
• Provide a reference scale to judge more advanced
  concepts.
• Can be tested in ITER
• First time operation of full blanket systems in a
  fusion environment.
• These tests will give important information on
  various aspects of blanket component functions
• But not sufficient (in particular for lifetime)
  and other approaches would also be required

17
Proposed Blanket RD Strategy (2)

• In parallel, critical RD should be done for the
  more advanced, higher risk but higher pay off
  concepts
• This RD is very much material-related
• Promises offered by the performance of advanced
  concepts provides a challenge to the material RD
  community to help the blanket design to achieve
  this
• Design effort on advanced blanket conceptual
  design should also be pursued to help guide the
  material RD towards high performance material
  and to provide a vision and a goal for attractive
  concepts for the future

• This requires close interaction and coordination
  between material and design communities, for
  example, through
• Cross meeting participation, organization of
  focused workshop
• e.g. International town meeting on SiCf/SiC at
  Oak Ridge in Jan. 2000