fusion presentation-npss-alex-ii

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

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Lecture II 4

Components of a Tokamak Reactor

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Lecture II 5

Breeding Blanket Functions and Requirements

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Lecture II 6

Example Fusion Power Flow

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Lecture II 7

Energy Distribution in Blanket and Divertor Zones

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Lecture II 8M. 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.)

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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

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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 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)

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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

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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

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Lecture II 37

Energy Spectra of Source Neutrons and Gammas from HAPL Target

Target spectrum from LASNEX results (Perkins, LLNL)

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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

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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

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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

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Lecture II 47

SOMBRERO Building

Lifetime of dielectric coated FF mirror increases with trap aspect ratio, distance from target, and neutron fluence limit

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Lecture II 48

Final Optics in HAPL

Bio-Shield

Turning (M3)

GIMM (M1)

Beam Duct

Focusing (M2)Shield

Blanket

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Lecture II 49

Fast Neutron Flux Distribution in Final Optics of HAPL

SiC GIMM

M2M3

Flux

(n/c

m2 s

)

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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