Fusion- Intro Flashcards
Good things about fusion
Abundant fuels: deuterium from water and tritium bred from Li.
Energy efficient: 1kg Li could produce enough tritium to supply as much energy as 900,000L of petrol or 100,000kg coal.
Env friendly: no carbon emissions directly associated with fusion reactions, no long-lived radioactive waste produced.
Safety: small amounts of fuel and fundamental fusion process means large-scale nuclear accident not possible.
Reliable power: provide baseload power
100 year criterion
All radioactive waste produced will decay to a safe level of activity within 100 years. Now this is being expanded to between 100 and 1000 years to be more realistic.
What is the fusion reaction?
Deuterium+tritium-> He+n
Releases 17.6MeV energy
14.1MeV of which is the neutron’s energy
How is tritium bred?
From Li
Li+n->He+T
Where T is tritium
Li-6 atom absorbs a neutron and splits (fission) into He and T
Describe the arrangement of the breeder blanket and where it is in a tokamak fusion reactor
It forms a torus like shape with the cross section of a hollow ear shape. At the bottom of this blanket sector is the divertor. The more curved outer side is the first wall. The inner more straight part is the blanket segment which contains the tritium breeder and support structure. The outer part (from the core) of this contains many blanket modules make of thin layers of Li ceramic breeder pebbles between thicker Be multiplier pebbles
Where do reactants and products for T production and fusion go with respect to the breeder blanket?
Fusion reactions in the core (next to the breeder blanket) produce neutrons which then go into the breeder blanket. Li is in the breeder blanket and absorbs a neutron and then splits into He and T. T then goes into the core to fuse with deuterium already there. The He produced from splitting of Li forms He bubbles in the breeder blanket.
Difference in neutron energy and operating temperatures between DEMO fusion reactors and PWR fission reactors
Neutron energy: DEMO is 14.1MeV to 0.025eV. PER is around 2MeV.
Operating temperatures: DEMO is 200-1000°C. PWR is about 350°C.
Difference in damage dose, transmutation product rates and steady-state heat fluxes between DEMO fusion reactors and PWR fission reactors
Damage dose: DEMO 80-140dpa. PWR under 50dpa.
Trans product rates: DEMO- 10appm He/dpa, 45appm H/dpa, 1550appm He. PWR- 0.1appm He.
Steady-state heat fluxes: DEMO 1-10MW/m^2. PWR 1MW/m^2 in fuel cladding
How do material challenges vary between ITER, DEMO and actual reactor?
They get more difficult going from ITER to DEMO to reactor
What features increase for the final reactors with respect to ITER and DEMO?
Fusion power
Heat flux in first wall and divertor
Neutron load in first wall
Integrated neutron load in first wall
First wall dpa
Transmutation product rates the same per dpa so increasing dpa increases their amount
