Fusion- Materials Qualification Lecture 1

Question 1

What is needed for fusion to occur of earth?

Answer 1

Plasma temperature of about 150mill K and confinement.

Question 2

What is the fusion reaction that will be used for fusion reactors?

Answer 2

Deuterium plus tritium makes helium and a neutron with 14.1MeV of energy

Question 3

Order of fusion power plants that will be built

Answer 3

JET (now)
ITER (being built?)
DEMO (demonstration power plant in future)

Question 4

What steady state loads will in-vessel components have to withstand?

Answer 4

Thermal: up to 20 MW/m2
Magnetic: up to 13T
Irradiation: up to 20-30dpa

Question 5

What does a divertor do?

Answer 5

Extracts the waste helium produced by the fusion reaction inside the tokomak. Goes round the bottom of the donut shape

Question 6

What is the divertor armour made of?

Answer 6

Series of tungsten monoblocks. Going through the monoblocks is a CuCrZr pipe (creep resistant) which acts as a heat sink and has cooling water going through it. The monoblocks will be absorbing 10-20MW/m2 of heat. Between the CuCrZr pipe and the monoblocks is a pure Cu interlayer to take the deformation due to thermal expansion

Question 7

What steady state loads will magnetic components have to withstand?

Answer 7

Thermal: superconducting magnets need to be at 4K
Magnetic: up to 13T
Irradiation: around 10dpa
Force: up to MN forces on the magnetic coils

Question 8

What is it necessary for the magnets to be able to do?

Answer 8

Be taken apart to allow for maintenance and inspection. Therefore contain re-mountable magnet joints between superconducting cables

Question 9

What is fusion regulated by in the EU and UK?

Answer 9

In the EU fusion is regulated and licensed under the same rules as nuclear fission.
In the UK fusion will be regulated by the Environment Agency and Health and Safety Executive (HSE)

Question 10

Monotonic loads and cyclic or time dependent loads to be considered for design criteria for in-vessel components

Answer 10

Monotonic: plastic collapse/plastic instability, exhaustion of ductility, fast fracture.
Cyclic or time dependent: high/low cycle fatigue (cycle dependent), creep (time dependent), creep/fatigue (cycle and time dependent).

Question 11

Other criteria to be considered for in-vessel components

Answer 11

Excessive deformation
Buckling
Melting, corrosion and erosion
Irradiation damage (creep/swelling)

Question 12

Suitable baseline materials for structural in-vessel components

Answer 12

Steel, reduced activation ferritic martensitic steels (RAFM).
316L stainless steels would become too radioactive

Question 13

Suitable baseline materials for thermal-hydraulic in-vessel components

Answer 13

Steel and/or copper, CuCrZr.
These are creep resistant and have food thermal conductivity

Question 14

Suitable baseline materials for armour/plasma facing in-vessel components

Answer 14

Tungsten and beryllium. These need to let neutrons through and these material do

Question 15

Suitable baseline materials for cryogenic (magnetic and structural) components

Answer 15

Structural: steel, 316L stainless steel.
Superconductors: Nb-Sn, Nb-Ti, Rare-Earth Barium Copper Oxide (REBCO).
Conductors: oxygen free high conductivity (OFHC) copper, pure Al.
Insulators: epoxy polymers and short fibre glass/epoxy composites

Question 16

What conditions do material properties need to be tested under for fusion applications?

Answer 16

From room temperature to operational conditions in 50C intervals.
From entry into service to 10s of dpa. Irradiation damage also depends on irradiation temperature

Question 17

What is Eurofer97?

Answer 17

A reduced activation energy ferritic-martensitic steel (RAFM)

Question 18

What determines the operational temperature window for fusion materials?

Answer 18

Low temperature limit is the DBTT. High temperature limit is thermal softening or creep

Question 19

What is STEP?

Answer 19

Spherical tokomak for energy production. In UK

Question 20

Problem for testing materials for use in fusion reactors

Answer 20

We will not have access to fusion spectrum 14MeV neutrons before we turn on STEP. Need to use other irradiation sources which will have minimal depth penetration