Nuclear Flashcards
Define Binding Energy
The minimum energy needed to pull a nucleus apart into its separate nucleons
Describe the process of induced nuclear fission
A slow moving ‘thermal’ neutron is absorbed by a nucleus such as U-235.
This causes the nucleus to become very unstable.
So it splits into two (unequal) parts and releases some fast-moving neutrons.
Describe and explain the process of nuclear chain reaction
Most reactions produce several neutrons which then collide with other nuclei causing a chain reaction.
Explain the role and composition of the fuel rods
The fuel rods are mainly U-235 but contain some U-238. U-235 undergoes fission but U-238 can decay to become Pu-239 which is toxic and has a long half-life.
Explain the role of control rods
They keep the reaction at a steady rate. They absorb neutrons to do this and may be made of boron.
Explain the role of the moderator
This can be carbon (graphite) or heavy water and the purpose is to slow the neutrons down so there is a greater chance they will cause induced fission.
Define Spontaneous
The decay of a particular nucleus is not affected by other nuclei or external factors.
Define Random
It is impossible to predict when a particular nucleus will decay or which nuclei will decay next
Define the decay constant
The probability a nucleus will decay per unit time
Define Activity of a source
The rate at which nuclei decay
How does C-14 Dating work?
Living plants and animals absorb Carbon (C-12 & C-14)
Once dead, they stop taking Carbon in.
The ratio of C-12 to C-14 is compared in the relic and a living sample.
x=x0e^-(lambda*t) used with data to estimate age.
Describe the use of radioactive isotopes in smoke alarms
An alpha source causes ionisation and a small current.
Smoke particles get charged instead. reducing the current which is detected and an alarm sounds.
