PhD studies report: "FUSION energy: basic principles, equipment and materials"

1. PhD studies report: "FUSION energy: basic principles, equipment and materials" Birutė Bobrovaitė; Supervisor dr. Liudas Pranevičius

2. Content Fusion reactions; Iter configuration; Plasma operation scenario; Fusion power plant; Plasma wall interaction; Materials and their properties.

3. The demand of energy will rise • The enviroment must be protected • Fossil fuels will eventually run out • We must continue to develope alternative energy sources Energy is vital

4. Fusion D + Tα particle (4He) (3.5 MeV) + n (14.1 MeV) Plasma heating – 3,5MeV; Energy sources – 14,1MeV.

5. ITER - way ITER – experimental reactor It is an international project involving: European Union, Japan, Russian Federation, China, South Korea, United States of America. The main goal to demonstrate the scientific and engineering feasibility of fusion as an energy source.

6. ITER JET: B – 3,8 T R – 2,9 m ITER: B – 5,5 T R – 6,2 m

7. Main parameters: Major radius: 6.2 m Minor radius: 2.0 m Plasma volume: 840 m3 Plasma current: 15 MA Toroidalfield: 5.3 T Pulse length: > 300 s Fusion power: 500 MW Plasma energy: 350 MJ n-wall load~: 0.5 MW/ m2 n-fluence: 0.3 MW-a/ m2 Heating power: 70-100 MW Machine height: ~25 m Machine diameter: ~26 m Machine mass: 23350 t

8. Tokamakconfiguration • A toroidal device • Large plasma current - poloidal magnetic field - confinement • Strong toroidal magnetic field - stability Magneticfield configuration

9. Vessel Purpose: • The vacuum vessel provides the high vacuum. • The vessel cooling also provides decay heat removal by natural water convection for all the vessel and in-vessel components. • The vessel also provides in-built attachment points for the blanket and divertor.

10. Blanket The blanket system is generally defined as the components that surround the plasma absorbing • heat; • radiation and neutrons from the plasma, • and converting the nuclear energy of the neutrons into thermal energy.

11. Divertor • Heat flow average:– 3-5 MW/m2 • Max heat flow: 10-20 MW/m2 • Heat flow < 5MW/m2 (W) • Heat flow to 20 MW/m2 (CFC) ITER divertor exhausts the flow of energy from charged particles produced in the fusion reactions and removes helium and other impurities resulting from the reactions, and from interaction of plasma particles with the material walls.

13. Plasmaheating

15. A fusion power plant

16. Tritium breeding The most promising source of tritium seems to be the breeding of tritium from lithium-6 by neutron bombardment which can be achieved by slow neutrons.

17. coolant Steam generator • Vacuum vessel • contains plasmachamber vacuum Turbines • Shield • reduces radiationload on VV andcoils T Divertor ElectricPower D+T He • Blanket • heat recovery • tritium generation • shielding • energy multiplication Fuel processing plant • Magnets • cryogenicsuperconducting(mass ~20,000 Te) • Biological shield • protects personnelfrom radiation Fusion Power Plant operation n Li Biological shield Magnet coils Vacuum Vessel Plasma Blanket Cryostat Shield

18. Plasmawall interaction • Plasmawall interaction based on erosion: • melting or sublimations (heat loads); • particle fluxes to the wall. • Transport process : • impurity remove; • neutralization, recycling.

19. Materials for fusion reactor The main characteristics of materials • High thermal conductivity • Resilience to thermal shocks • Low neutron activation • Low chemical erosion • Low affinity to hydrogen towards formation of volatile products • Low affinity to oxygen towards formation of volatile products • Oxygen gettering(formation of stable oxides) • Low sorption of hydrogen

20. Structural materials • The main structural material in ITER is austenitic stainless steel. • For magnets are used niobium alloy . Plasma facing materials: • Tungsten • Beryllium • CFC These materials are connected to cupper alloy cooling system and connected tothe main structural material stainless steel.

21. Materials • 700m2Be – first wall: - low Z - good oxygen getter •~ 100m2W – divertor (baffle, dome): - low erosion - long lifetime • ~ 50 m2CFC – divertor target - no melting - C good radiator, emitter

22. Berilium • Low plasma contamination; • Low radiative power losses; • Good oxygen gettering; • Low bulk tritium inventory; • Lowest BeO and metallic impurity content amongthe other structural grades; • High elevated temperature ductility; • Thermal shock resistance.

23. Tungsten chemical properties: - Atomic weight – 183,85; • Highest melting point in comparison with other infusible materials - 3683 K; • Boiling temperature – 5933K; • Tungsten density – 19,35 g/cm3; • Crystal lattice – body- centered crystal.

24. Tungsten physical and mechanical properties: • High temperature stability and tightness; • High thermal conductivity; • Low tritium retention; • Compability with plasma.

25. Tungsten disadvantages: • Low erosion rate -low sputtering productivity; • During breakdown tungsten melt faster then CFC; • Low ductility at low temperature; • Recrystalisation at high temperature.

26. Production of layers • Thin layers (CVD, PVD): • carbon substrates; • short lifetime. • Thick layers (PS, LPPS) • High porousity; • Limited thermal conduction.

27. Thank You for Your attention