Fission and Fusion

Question 1

What is fission?

Answer 1

The splitting of a ²³⁵₉₂U nucleus or a ²³⁵₉₄Pu nucleus into two approximately equal fragments.

Question 2

What is induced fission?

Answer 2

Induced fission is fission caused by an incoming neutron colliding with a ²³⁵₉₂U nucleus or a ²³⁵₉₄Pu nucleus.

Question 3

Define fission neutron

Answer 3

Neutrons released when a nucleus undergoes fission and which may collide with nuclei to cause further fission.

Question 4

What is a chain reaction?

Answer 4

• A series of reactions in which each reaction causes a further reaction.
• In a nuclear reactor, each fission event is due to a neutron colliding with a ²³⁵₉₂U nucleus which splits and releases two or three further neutrons that can go on to produce further fission.
• A steady chain reaction occurs when one fission neutron on average from each fission event produces a further fission event.

Question 5

What is critical mass?

Answer 5

• The minimum mass of the fissile isotope (e.g., the uranium isotope ²³⁵₉₂U ) in a nuclear reactor necessary to produce a chain reaction.
• If the mass of the fissile isotope in the reactor is less than the critical mass, a chain reaction does not occur because too many fission neutrons escape from the reactor or are absorbed without fission.

Question 6

Energy released =

Answer 6

change in binding energy = Δmc²

Question 7

Why does nuclear fusion take place?

Answer 7

The binding energy per nucleon of the product nucleus is greater than the initial nuclei.

As a result, energy is released equal to the binding energy

Question 8

When does fusion take place?

Answer 8

• When the nuclei are combined at high speeds.
• To overcome the electrostatic force of attraction.