Fusion

Question 1

Definition of fusion

Answer 1

Joining of two nuclei at extremely high temps and pressure.

up to 5MeV produced (compared to 1 with fission) per nucleon.

Question 2

What elements undergo fusion easiest?

Answer 2

Light elements, as binding energy is low.

Question 3

Equation of fusion

Answer 3

Deuterium (D) + Tritium (T) -> Helium (He) + High energy neutron

Question 4

Why are deuterium and tritium used for fusion?

Answer 4

Their reaction occurs easily as its a low temp reaction but still sufficiently large energy outputs.

Question 5

What the concern with fusion in terms of tritium?

Answer 5

Not sufficient tritium supplies in nature and globally, would have to develop more.

Fairly short half life of 12.3 years

Question 6

How does the tritium fuel cycle work?

Answer 6

1. Lithium is placed in a blanket around the reactor - to generate, recover and store tritium.
2. When it consumes a neutron is split to form tritium
   Neutron + Li-6 -> He-4 + H-3 (tritium)
3. Stores and freezes tritium, can then fire it back into reactor plasma

Question 7

Why are there fewer concerns with fusion?

Answer 7

• No residual heat generated in reactor pool.
• Don’t have to actively cool, therefore can have heat incident.
• No fission products which are radioactive for long periods.

Question 8

Describe the what happens to energy related to fusion in stars when elements are lighter or heavier than Fe.

Answer 8

Elements lighter than Fe - fusion process creates energy

Elements heavier than Fe - fusion process consumes energy.
- These elements are created in supernovas, when there is a flood of neutrons.

Question 9

Where does fusion occur in stars?

Answer 9

Occurs in star cores, where pressure and temperature are high forcing atoms to fuse.

Question 10

Whats the main fusion cycle in stars?

Answer 10

PPI chain - 69% of the time

Hydrogen produces helium