Fission and Fusion

Question 1

What is:

Nuclear fission

Answer 1

The splitting of a large atomic nucleus into smaller nuclei

Question 2

What is:

Nuclear fission

induced fission

Answer 2

• Happens in a chain reaction
• neutrons are absorbed by the nucleus of an atom of a fissionable substnace

Question 2

What are the:

Products of uranium fission

Answer 2

3 neutrons, energy in kinetic and EM waves, and 2 daughter nuclei

Question 2

What does the:

Nuclear reactor consist of?

Answer 2

Uranium fuel rods spaced evenly in the reactor core as well as control rods
This is so that neutrons that escape by a fuel rod can be absorbed by another or a control rod

Question 2

How to:

Increase or reduce the rate of the reaction in a nuclear power station

Answer 2

Lowering a control rod reduces fission reaciton
increased control rod increases fission reaction rate

Question 2

What is the:

Nuclear reactor made out of

fuel rods

Answer 2

• Fuel rods must have fissionable isotopes
• Most use enriched uranium, made out of:
• non-fissionable U-238 which changes into other heavy nuclei including fissionable plutonium 239
• Plutonium cannot be used in U-235 reactor
• 2-3% is fissionable U235

Question 2

What is in the:

Reactor Core

Answer 2

• Fuel rods, control rods, water at high pressure
• fission neutrons are slowed down by collisions with water molecules, preventing further fission of U-235 and making sure the neutrons can be absorbed
• Reactor core is made from thick steel, which withstands high temperature and pressure in the core
• core is enclosed in thick concrete wall which absorbe radiation that escapes through the steel

Question 3

What is the purpose of:

Water in a nuclear reactor

Answer 3

• Water acts as a coolant
• water molecules gain KE from neutrons and fuel rods, and is pumped through the core
• Goes to a heat exchanger outside the core which transfers energy for the heating to the heat exchanger from the core
• acts as a moderator by slowing the fission neutrons

Question 4

Purpose of:

Control rods

Answer 4

• Absorb surplus neutrons
• Controls the chain reaction
• This is adjusted to maintain a steady chain reaction
• Can be raised so that less neutrons are absorbed and the rate of nuclear fission increases
• When the energy output increases the control rods are lowered leading to more neutrons being absorbed and the rate of nuclear fission decreases which leads to the energy output decreasing