Nuclear fission Flashcards
What is nuclear fission?
The splitting of a large, unstable nucleus into two smaller nuclei.
What are fissile materials?
Materials that can undergo fission under the right conditions, such as uranium and plutonium.
What is induced fission?
When a uranium-235 nucleus absorbs a neutron, becomes uranium-236, and splits almost immediately.
What is spontaneous fission?
Fission that occurs without additional energy being put into the nucleus.
What are the products of fission?
Two smaller daughter nuclei, two or three neutrons, and gamma rays.
What is a chain reaction?
A chain reaction occurs when a neutron emitted from the splitting of a nucleus causes further nuclei to split, and the neutrons emitted from these cause further fission reactions.
What happens during the fission of uranium-235?
Uranium-235 absorbs a neutron and becomes uranium-236, which is very unstable and splits by nuclear fission almost immediately.
What energy is released during fission?
Energy is transferred from the nuclear potential energy stored in the original nucleus into the kinetic energy of the products.
What happens in a chain reaction involving uranium-235?
Each fission produces two or three neutrons, which move away at high speed and can cause further fission reactions.
What is critical mass?
The minimum amount of fissile material required for a sustained chain reaction.
What happens if the mass of fissile material exceeds the critical mass?
The rate of reaction accelerates, which can cause a huge and uncontrolled release of energy, i.e., a nuclear explosion.
What is the purpose of control rods?
Control rods are made of a material which absorbs neutrons without becoming dangerously unstable themselves.
What happens when control rods are lowered?
Lowering the rods decreases the rate of fission, as more neutrons are absorbed.
What happens when control rods are raised?
Raising the rods increases the rate of fission, as fewer neutrons are absorbed.
What is the purpose of a moderator?
The moderator is a material that surrounds the fuel rods and control rods inside the reactor core and slows down neutrons by colliding with the molecules of the moderator.
