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Creep Fatigue Interaction for Nuclear Fusion

4 October 2018

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To lead the commercial development of fusion power and related technology and position the UK as a leader in sustainable nuclear energy

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UKAEA’s mission statement

Nuclear Fusion

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Fusion Reaction on Earth

Deuterium

TritiumNeutron

Helium

+ energy (17.6MeV)

Deuterium

TritiumNeutron

Helium

+ energy (17.6MeV)

Deuterium supplies are extensive

Tritium to be bred from lithium through neutron reactions6Li + n → 4He + T

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The Tokamak Concept

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Toroidal field coilPrimary transformer circuit

Secondary plasma currentPoloidal magnetic field

Toroidal magnetic field

Resultant helical magnetic field

EU-Fusion Power Roadmap

JETJoint European Torus ITER DEMO

The EU fusion community is pursuing an aggressive programme of research to allow the near-term realisation of a

demonstration magnetic confinement fusion power plant (DEMO).

Physics Oriented

Technology

Oriented

Confinement, H-mode scaling, ITER-like wall

Burning plasma, current drive steady state (long

pulse), disruption control, edge control)

Superconducting magnets, fueling, heating/CD,

test blanket modules

Electricity generation (balance of plant), materials and component lifetime, closed fuel cycle, remote

maintenance, availability

Technology & Materials Programme

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Fusion operational limits

“..known, knowns .. known, unknowns (and) unknown, unknowns…1”

Fusion will require a pragmatic approach and accepted of risks

1 Part of speech by Donald Rumsfeld in 2002

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The Blanket Challenge

▪ To shield the vacuum vessel and the superconducting magnets

▪ To capture the neutrons to “breed” tritium fuel

▪ To turn the kinetic energy from neutrons into heat energy for electrical power production

▪ High structural integrity to permit long operational lifetimes (~years)

▪ High operational temperature to promote high thermodynamic efficiencies

Functions

Requirements

Power densities: >1MWm-2 steady state

Cyclic operation: >15,000 cycles anticipated in DEMO

Irradiation: ~10dpa/fpy via 14MeV neutrons

~12appm/dpa Helium production

Lifetime: >5fpy in order to assure availability

Temperature: >500℃ for high thermodynamic efficiencies

Power plant solution demands innovation:

Materials, Engineering, Physics

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Using steel in the blanketTritium permeation – issues and

compatibility with permeation

barriers

He and H production

Water/He compatibility

Matching temperature for BoP

Codes and StandardsCompatibility with vacuum

conditions

Tritium trapping in damaged

material

Total mass

Performance on cyclic

operational plantCompatibility with remote

handling

Manufacturing to acceptable

tolerances

Extreme heat flux at the surface

Accident tolerance: Loss of

coolant, temperature spikes,

ELM

Oxidation and plasma erosion

tolerance Total costs

Compatibility with diagnostics

Compatibility with heating and

current drive components

Meeting lifetime requirements

Effects of high magnetic field on

propertiesMeeting reduced activation

requirements

Effects of ELMs inducing

magnetic swings

Enabling of in-service

inspection techniques

Beryllium and Lithium pebble

compatibility

Liquid lithium and lead

compatibilityJoining methods

Effects of neutrons

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Using steel in the blanketTritium permeation – issues and

compatibility with permeation

barriers

He and H production

Water/He compatibility

Matching temperature for

BoP

Codes and StandardsCompatibility with vacuum

conditions

Tritium trapping in damaged

material

Total mass

Performance on cyclic

operational plantCompatibility with remote

handling

Manufacturing to acceptable

tolerances

Extreme heat flux at the surface

Accident tolerance: Loss of

coolant, temperature spikes,

ELM

Oxidation and plasma erosion

tolerance Total costs

Compatibility with diagnostics

Compatibility with heating and

current drive components

Meeting lifetime requirements

Effects of high magnetic field on

propertiesMeeting reduced activation

requirements

Effects of ELMs inducing

magnetic swings

Enabling of in-service

inspection techniques

Beryllium and Lithium pebble

compatibility

Liquid lithium and lead

compatibilityJoining methods

Effects of neutrons

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Creep Fatigue Interaction

Creep fatigue is the life limiting factor in

proposed DEMO operation

• Material: EUROFER97 (Ferritic-

martensitic steel)

• Operating temperature: ~500⁰C

• Operational stresses: ~100MPa

• Operating cycle: Ramp up with ~2hr hold

• Number of cycles: ~40,000

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Data gathering -> testing

• Issues to overcome:

– How to accelerate the testing

– Tension / compression testing

– Incorporating heating and vacuum

– Dealing with small sized samples

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Data gathering -> testing

• Phoenix hydraulic testing rigs:

– Creep and fatigue

– IR heating

– Bespoke grips for small samples

• Future rigs

– Incorporate vacuum

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Structural integrity case

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DEMO is a First of Kind Engineering Project Success/Failure based on sufficient:

component performance (safety & operational)lifetime

Verification of structural integrity at design phase and through life are pivotal!

Courtesy UKAEA

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FusionUKAEA is at the vanguard of fusion research; we work to help mankind harness this power.

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