E.4 Fission

UNIT SYLLABUS

SL/HL

Nuclear fission process, chain reactions, and nuclear power.

1 Key Formulas

Mass-Energy Equivalence

E = mc^2

2 Exam Preparation & Topic Explanations

Mastering Nuclear Fission and Reactors

Nuclear fission is the process where a heavy, unstable nucleus (such as Uranium-235) splits into two lighter fragments after absorbing a neutron. This split releases a large amount of energy (roughly 200 MeV per U-235 fission) and several fast neutrons, which can go on to trigger a self-sustaining chain reaction.

Key components of a pressurized water nuclear reactor:

Fuel Rods: Contain the fissionable material.

Moderator: Slows down the high-energy neutrons produced in fission so they can successfully induce further fissions. Water often acts as both the moderator and the coolant for heat exchange.

Control Rods: Regulate the reaction rate by acting as good absorbers of neutrons.

Heat Exchanger: Transfers thermal energy to a separate system, helping generate electricity through turbines.

Pro Exam Strategy

When balancing nuclear fission equations, ensure both the sum of nucleon numbers (A) and the sum of proton numbers (Z) remain conserved.
Distinguish clearly between the roles of the moderator (slowing neutrons) and control rods (absorbing neutrons).
Be prepared to discuss the environmental impacts of fission power, particularly the management and long-term storage of radioactive nuclear waste.

3 MCQ Practice

Q1. Which of the following statements about a nuclear fission reactor are correct? I. The heat exchanger transfers energy from the fuel rods to the moderator. II. The control rods must be good absorbers of neutrons. III. The moderator must slow neutrons down.

I and II only
I and III only
II and III only
I, II and III

4 Short Answer Questions

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E.3 Radioactive decay

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E.5 Fusion and stars

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