Lecture 10: Fusion

Question 1

What are the two variations of fusion?

Answer 1

PP
DT

Question 2

What is the reaction for DT fusion?

Answer 2

H2 + H3 > He4 + neutron

Question 3

What does DT fusion stand for?

Answer 3

Deuterium and Tritium Fusion

Question 4

What key condition is required for fusion to occur?

Answer 4

Need sufficient KE to overcome coulomb repulsion of positively charged deuterium and tritium nuclei.

Question 5

Approximately how much particle energy is needed for fusion?

Answer 5

10 keV

Question 6

What is fusion gain?

Answer 6

Ratio of:
Fusion power released /
Power injected into plasma

Question 7

What is the fusion gain of a realistic fusion power plant?

Answer 7

Q >= 20

Question 8

How is the high speed of particles replicated?

Answer 8

Supply high temperature in the for of plasma

Question 8

Define triple power?

Answer 8

a single value tells us how close a fusion experiment is to net power

Question 9

How is triple power calculated?

Answer 9

n the density of ions in the plasma (ions/cubic meter)
T the temperature of those ions (keV2)
τE the energy confinement time (seconds)

Question 10

Name three methods for fusion:

Answer 10

Magnetic Confinement
Inertial Confinement
Pinches

Question 11

What is magnetic confinement?

Answer 11

The use of magnets to confine a fusion reaction by suspending the fuel and controlling the direction of particle travel.

Question 12

What is a significant practical hurdle for fusion?

Answer 12

Must avoid touching surrounding walls due to 100 million K temperature.

Question 13

Name three magnetic confinement designs:

Answer 13

Stellarator
Reversed Field Configurations
Tokamaks

Question 14

What shape is a tokamak?

Answer 14

Torus

Question 15

Name two key fusion research programs:

Answer 15

JET (Joint European Torus)
ITER (International Thermonuclear Experimental Reactor)

Question 16

What is a challenge for JET?

Answer 16

Can only sustain a pulse of energy for 1-6 seconds as operational time limited by overheating of copper electromagnets.

Question 17

Name two variations of laser inertial confinement:

Answer 17

Direct Drive
Indirect Drive

Question 18

What is direct drive?

Answer 18

Lasers strike a small pellet of fuel which rapidly compresses and heats to produce a burst of fusion energy.

Question 19

What is indirect drive?

Answer 19

Lasers heat the inner walls of a cavity
Creates super hot plasma which radiates x-rays and heats outer surface of a fuel pellet
Fuel capsule implodes producing energy,

Question 20

Where is the greatest investment into laser inertial confinement?

Answer 20

USA

Question 21

What does a pellet of fuel contain for laser inertial confinement?

Answer 21

Deuterium and Tritium

Question 22

What is the greatest difficulty for laser inertial confinement?

Answer 22

Simultaneously directing lasers at a pellet / capsule

Question 23

Is fusion more or less safe than fission?

Answer 23

More

Question 24

Why is fusion considered more safe?

Answer 24

Reaction stops a few seconds after fuelling
Very little fuel is required
Dose to public is well below evacuation level
No potential of widespread melting

Question 25

What is a challenge of using tritium?

Answer 25

Does not naturally occur, must be manufactured / bred

Question 26

What is the purpose of blanket modules?

Answer 26

Extract heat from the fusion reactor for electrical power generation
Shielding, preventing the high-energy neutrons from escaping to the area outside the reactor

Question 28

What is the conversion between kelvin and electrovolt?

Answer 28

1 kelvin = 8.62 e-5 eV

Question 29

What value of triple power is needed for ignition?

Answer 29

5 e21