Nuclear Flashcards
What is the composition of Alpha radiation ?
helium nucleus
2protons, 2neutrons
What is the mass and charge of Alpha radiation ?
4 relative mass
+2 relative charge
What is Beta radiation made of ?
A high velocity electron
What is the mass and charge of Beta radiation ?
0 relative mass
-1 relative charge
What is gamma radiation ?
A wave of electromagnetism (shortest wavelength)
What is the charge and mass of gamma radiation ?
0 relative charge
0 relative mass
What is one use of alpha radiation ?
Smoke alarms
What is one use of beta radiation ?
testing paper thickness
What is one use of gamma radiation ?
to be used as a medical tracer
(put into body and creates an image of the body for medical tests)
What can alpha penetrate ?
A few centimetres of air
Stopped by paper
What can beta penetrate ?
A few centimetres of air
A few millimetres of paper
Stopped by aluminium
What can gamma penetrate ?
A few centimetres of air
A few millimetres of paper
A few millimetres of aliminium
Stopped by Thick lead
What is the ascending order of strength in radiation ?
Alpha
Beta
Gamma
What is the ascending order of ionisation in radiation ?
Gamma
Beta
Alpha
Why is gamma least ionising ?
1 photon interacts with 1 electron
so each gamma photon can only ionise 1 atom and only if it actually hits an electron
Why is alpha more ionising than beta ?
Alpha is slower (more time to interact)
Much bigger (bigger space to interact)
x2 charge (twice as likely to ionise)
What are some sources of radiation ?
rocks
fallout from nuclear testing
radiation from chenauble
How is background radiation accounted for in an experiment ?
count background radiation for ~10 minutes
deduct from final count
What is the unit for activity ?
Number of decays per second
Bq
s^-1
What is the unit for Intensity ?
Activity per unit area
Bq m^-2
s^-1 m^-2
What did Rutherford do in his experiment ?
- Alpha particles fired at very thin gold foil
- In a vacuum
( Had a detector to see where the particles went )
What were the results of Rutherford’s experiment ?
- Most alpha particles went straight through
- Some deflected at small angles
- Some deflected at large angles (90+)
Why did the alpha particles going straight through align with the modern structure of the atom ?
- Atom is mostly empty space
Why did the alpha particles deflecting align with the modern structure of the atom ?
- The positive charge is held in the nucleus (like charges repel)
What happens to the kinetic energy when a particle gets to the point of closest approach ?
- All converted to Electric Potential energy
What is the graph for electron diffraction (x : diffraction angle, y : intensity of scattered electrons)
- Minimum angle : max intensity
- Max angle : min intensity
- Middle of graph has a sharp decrease that then goes to an increase (graph is not a standard curve, has 2 turning points in the middle)
What is the purpose of electron diffraction ?
To get a better measurement of a nucleus radius (alpha particles are bigger and can make nucleus recoil)
What does N mean in a Nuclear decay equation ?
Number of undecayed nuclei
What does N0 mean in a Nuclear decay equation ?
Number of Nuclei at the start
When can the Activity equation
( ΔN / Δt = -A = λN) be used
If given a graph
What is the unit for Count rate ?
Bq
counts per time period
What is a half life ?
- Time taken for activity to half
- Time taken for number of undecayed nuclei to half
What is the unit for decay constant (λ)
s^-1
How to find the half life from a graph ?
From a y value, use the graph to find out how long it takes to half and repeat 3 times
On a graph with number of neutrons against number of protons where is beta- decay ?
just above the line for stable nuclei
On a graph with number of neutrons against number of protons where is beta+ decay / electron capture ?
Just below curve
On a graph with number of neutrons against number of protons where is alpha decay ?
further below the line than beta+
What is binding energy ?
Energy difference when nucleons join via strong
How to calculate binding energy ?
Calculate initial mass of protons + neutrons
Calculate total mass of nucleus
Sub Mass difference into E = mc^2
What is fusion ?
When 2 nuclei come together to make a bigger nucleus
What are the conditions for fusion ?
- Travelling fast enough to overcome electrostatic repulsion
- High temperature
- Lots of nuclei
What is fission ?
When a large nucleus splits into 2 smaller nuclei
What is a fission chain reaction ?
n —> (big nucleus) —> 2 smaller nuclei + 3n
What is a thermal neutron ?
A neutron with 1eV of kinetic energy
Why does a thermal neutron need 1eV of kinetic energy to induce fission ?
Too much energy it will go right through the nucleus
Too little energy it will bounce off
Why does a thermal neutron need 1eV of kinetic energy to induce fission ?
Too much energy it will go right through the nucleus
Too little energy it will bounce off
What does a moderator do ?
- Slows down neutrons (so they have 1eV Ek) through inelastic collissions
- Made from graphite or water (to not absorb neutrons)
What do fuel rods do ?
- Contains the fuel
- Makes it easier to change fuel
- Used up over time so become less effective
- Usual fuel is uranium
What does a coolant do ?
- Removes heat from the reactor
- Usually made of water or carbon dioxide
What do the control rods do ?
- Absorb neutrons from the fission so that 1 is left
- Can be move further in to slow down reactions
- Can be moved further out to speed up
- Can be made from Boron or Cadmium
Why does the Nuclear Reactor get hot ?
- Neutrons collide with the moderator
- Atoms gain Ek
Why does the nuclear reactor have shielding ?
- To absorb neutrons
- Reduce intensity of gamma rays
- Made from concrete
What happens when the control rods are dropped fully in ?
- Absorbs all the neutrons
- Stops reactions
- Stops the reactor quickly
How is Nuclear Waste stored ?
- Removed by remote control
- Stored in a cooling pond for several months
- Remaining waste is stored in glass and buried underground
