Fusion presentation-npss-alex-ii
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Lecture II 1
Introduction to Fusion Technology Issues
. Lecture II In-vessel components: Blanket,
shield, Divertor
Prof. Mohamed SawanFusion Technology Institute
University of Wisconsin-MadisonM. Sawan
Lecture II 2
Outline
• In-Vessel Components• Magnetic Confinement Blanket,
Shield, Divertor• Inertial Confinement Blanket, Shield
M. Sawan
Lecture II 3
MFE and IFE Fusion Reactors are Complex with Many Components
MFE IFE
M. Sawan
Lecture II 4
Components of a Tokamak Reactor
M. Sawan
Lecture II 5
Breeding Blanket Functions and Requirements
M. Sawan
Lecture II 6
Example Fusion Power Flow
M. Sawan
Lecture II 7
Energy Distribution in Blanket and Divertor Zones
M. Sawan
Lecture II 8M. Sawan
Lecture II 9M. Sawan
Typical Radial Build in MFE Reactor
Lecture II
Tritium Breeding in Lithium
10
Two Reactions:6Li(n,a)t
• Low energy• Multiplier helps
7Li(n,n’a)t• High energy• Competes with multiplier
• Produces additional neutron along with breeding
M. Sawan
Lecture II
Fusion Facilities beyond ITER Should Breed Their Own Tritium
Almost all tritium supply will be used by ITER and FNSF has to be self-sufficient in tritium in addition to providing initial startup inventory for DEMO
11M. Sawan
Lecture II 12
Tritium Breeding Potential of Candidate Breeders
Li and LiPb have highest breeding potential
Breeders with moderate breeding potential (Li2O, Flibe) require moderate amount of multiplier
Ceramic breeders have poor breeding potential and require significant amount of multiplier and minimal structure content
Enriching Li in 6Li is beneficial when a multiplier is used
In realistic designs, the structure, configuration, and penetrations will degrade the achievable overall TBR below the values shown
0.60.81.01.21.41.61.82.0
1.041.061.081.101.121.141.161.181.20
TBR
Energy Multiplication, M
Li17Pb83(90% 6Li)Li (nat.)
Flibe (nat.)
No StructureNo Multiplier2 m Blanket
Li2O (nat.)
Li4SiO4 (nat.)Li2TiO3 (nat.)
LiAlO2 (nat.)
Li2ZrO3 (nat.)
M. Sawan
Lecture II 13
Blanket Breeding Materials
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Lecture II 14
Issues for Blanket Breeders
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Lecture II 15
Neutron Multipliers
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Lecture II 16
Issues for Neutron Multipliers
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Lecture II 17
Component Damage and Lifetime
M. Sawan
Low Activation Structural Materials for Fusion
18
Based on safety, waste disposal and performance considerations, the 3 leading candidates are: Ferritic/martensitic steelsVanadium alloySiC/SiC composites
Lecture IIM. Sawan
Lecture II 19
Issues for Structural Materials
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Lecture II 20
Blanket Coolants
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Lecture II 21
SiC/LiPb Blanket Designs
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Lecture II 22
Helium Cooled Pebble Bed Blanket
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Lecture II 23
Helium Cooled Lithium Lead Blanket
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Lecture II 24
Dual Coolant Lithium Lead Blanket
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Lecture II 25M. Sawan
Lecture II 26M. Sawan
Lecture II 27M. Sawan
Lecture II 28M. Sawan
Lecture II 29
Divertors• To first order, particles are
confined to the closed field lines
• A divertor uses a “separatrix” to separate closed from open field lines
• W is the lead plasma facing material with Carbon Based material as alternate (retains T)
M. Sawan
Lecture II 30
Particle Load Summary
• Particles strike walls, leading to sputtering• Sputtered particles will be pumped or
deposit somewhere in the chamber• Key issues are
– Particle flux and spectrum– Sputtering rate and mechanism– Transport and deposition throughout chamber
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Lecture II 31
The ITER Divertor
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Lecture II 32
Candidate Plasma Facing Materials
M. Sawan
From: V. Barabash, et al., “Selection, Development and Characterization of Plasma Facing Materials for ITER,” Journal of Nuclear Materials, Vol. 233-237, pp. 718-723 (1996).
Lecture II 33
IFE Chamber RequirementsEstablish at a rep rate 1-10 Hz chamber conditions to
allow target injection (or placement in the case of Z-IFE), beam propagation and engagement at specifications needed for ignition and high gain (unique for IFE)
Protect the first wall from pulsed, short-ranged target emissions (x-rays and ion debris), e.g., from intense thermal spikes and ion damage, or design the FW to accommodate these threats (unique for IFE)
Capture and transfer power to power conversion systemBreed, recover and recycle tritium to provide a self-
sustained fuel Cycle. For IFE, adequate tritium breeding is typically not the most constraining requirementM. Sawan
Lecture II 34
Three Categories of IFE Chamber Design
• Dry-wall– Gas protected– Magnetically protected– Engineered surface
• Wetted-wall• Thick-liquid-wall
M. Sawan
Lecture II 35
Blanket Design in IFE Chamber Blanket design options used in MFE can be
used in IFE Surface heat flux is higher at FW in IFE
requiring more attention and using liquid walls is an attractive option
Flowing liquid metals can be utilized due to lack of MHD effects
Space is not constrained allowing using thicker blankets with potential for higher TBR
M. Sawan
Lecture II 36
Target Neutronics• Initial split of energy from DT fusion energy is 14.1 MeV n and
a 3.5 MeV a • In IFE target, DT fuel is heated and compressed to extremely
high densities before ignition and neutron fuel interactions cannot be neglected
• Softening of neutron spectrum, neutron multiplication, and gamma production occur
• Energy deposited by neutrons and gamma heats target and ultimately takes the form of radiated x-rays and expanding ionic debris
• Spectra of neutron and gamma photons emitted from the target represent the source term for subsequent blanket neutronics, shielding, and activation calculations
M. Sawan
Lecture II 37
Energy Spectra of Source Neutrons and Gammas from HAPL Target
Target spectrum from LASNEX results (Perkins, LLNL)
M. Sawan
Lecture II 38
HAPL Blanket Thermal Power for 1836 MW Fusion Power (5 Hz Rep Rate)
Total Thermal Power 1878 MW
Volumetric Nuclear Heating
1548 MW
Ion Energy Dissipation
307 MW
X-rays Surface Heating
23 MW
Blanket coverage 91.6% Target yield 367.1 MJ (274.3 n, 0.017 , 4.94 x-ray, 87.84 ions) 70% of ion energy dissipated resistively in blanket
• Thermal power in water-cooled 50 cm thick shield is only 3 MWM. Sawan
Lecture II 39
Examples of Recent Chamber Designs
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Lecture II 40
Dry Wall Examples
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Lecture II 41
Wetted Wall Examples
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Lecture II 42
Thick Liquid Wall Examples
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Lecture II 43
Impact of Wall Protection Scheme on Neutronics Features
• Various IFE wall protection methods influence the FW/blanket design and neutronics features– Dry wall (e.g., SOMBRERO, SIRIUS-P)– Wetted wall (e.g., HIBALL, PROMETHEUS-L)– Liquid wall (e.g., HYLIFE)
• Blanket neutronics features of dry wall and wetted wall designs are
identical since thin liquid sheet in wetted wall provides negligible neutron attenuation
• Thick liquid wall concepts have different neutronics features due to
protection of blanket structure by thick liquid layer and elimination of structure in thick breeding liquid layer
M. Sawan
Lecture II 44
Biological Shield Requirement• Biological shield is needed outside the chamber to maintain occupational biological
dose rate <25 mSv/h outside building during operation• Required shield thickness depends on location of shield and material used in
components between target and shield• 2.5-3.5 m thick steel re-enforced concrete shield is needed• If allowed by maintenance approach, significant reduction in shield volume and cost
is realized by placing the biological shield as close as possible to the chamber
LIBRA-SP1.2 m FS/LiPb blanket
M. Sawan
Lecture II 45
Beam Line Penetration Shielding
Penetrations in IFE chamber required for ions or laser transport from driver to target
Measures must be taken to protect the vital components from streaming radiation
Shielding issues are different for the two drivers considered• Laser• HIB
M. Sawan
Lecture II 46
Shielding of Final Optics in Laser Driven IFE• Final laser optics located in direct line-of-sight of source neutrons experience
largest radiation damage• Damage level in these components can be reduced only by moving them
farther from target• Damage contributed mostly by direct source neutrons Dielectric coated mirrors Sensitive to neutron radiation that degrades optical transmission of
dielectric material, decomposes dielectric materials, and destroys interfaces between dielectric layers
Removing them from line-of-sight of target neutrons prolongs their lifetime Grazing incidence metallic mirrors (GIMM)More radiation resistant and can be used in direct line-of-sightLifetime of GIMM is limited by mirror deformation from swelling and creep
that leads to defocusing of laser beam
M. Sawan
Lecture II 47
SOMBRERO Building
Lifetime of dielectric coated FF mirror increases with trap aspect ratio, distance from target, and neutron fluence limit
M. Sawan
Lecture II 48
Final Optics in HAPL
Bio-Shield
Turning (M3)
GIMM (M1)
Beam Duct
Focusing (M2)Shield
Blanket
M. Sawan
Lecture II 49
Fast Neutron Flux Distribution in Final Optics of HAPL
SiC GIMM
M2M3
Flux
(n/c
m2 s
)
M. Sawan
Lecture II 50
Shielding of Final Focusing Magnets in HIBALL• Final focusing system consists of set of quadrupole magnets (usually superconducting) • Shielding provided between the ion beam and the final focusing magnets• Shield configuration should not interfere with the ion beam envelope
Effective shield configuration developed for HIBALL and utilized in OSIRIS
Radiation effects in magnets can be reduced by about three orders of magnitude by tapering inner surface of shield along direct line-of-sight of source neutrons
All direct source neutrons impinge on neutron dumps at optimized location that minimizes magnet damage
Magnets are lifetime components
M. Sawan
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