Radioactivity Flashcards
ion
element that has gained/lost electrons
isotope
element with the same number of protons, but different number of neutrons
Mass number
protons + neutrons
Atomic number
proton number
When does an atom become stable
when it doesn’t emit ionising radiation anymore
Ionising radiation
radiation with the ability to knock electrons off other atoms, damaging them
Alpa particle
2 protons + 2 neutrons (helium nucleus)
charge: +2
mass: 4
slow
most ionising
least penetrating (few cm of air, paper, skin)
Beta particle
electron
charge: -1
mass: 1/1800
fast (10% of speed of light)
medium ionising
medium penetrating (aluminium, bone)
Gamma wave
Electromagnetic wave
Gamma wave
Electromagnetic wave
charge: 0
mass: 0
very fast (speed of light)
least ionising
Most penetrating (Thick lead)
Describe how to measure radioactivity of a rock
- use a GM tube + counter (if not given)
- measure background radiation
- measure radiation from the rock
- subtract background
Describe an experiment to prove a rock emits beta radiation
- use a GM tube + counter (if not given)
- measure background radiation
- measure radiation from the rock
- place PAPER between rock and tube
- reading stays the same
- place aluminium between
- radioactivity drops to background
Sources of Background radiation
Cosmic rays from sun
Potassium in food + drink
Radon gas in air
Radioactive rocks in buildings/mountains
Alpha emission
mass number -4
atomic number -2
U 238,92 –> α 4,2 + Th 234,90
Gamma emission
mass number stays the same
atomic number stays the same
U 238,92 –> γ 0,0 + U 238,92
Beta emission
mass number stays the same
atomic number +1
U 238,92 –> β 0,-1 + Np 238,93
Beta production
During beta emission, a neutron splits into a proton (stays in the nucleus) and an electron (leaves)
Activity
is the amount of raidation given off by an element over a period of time. Measured in Bequerells (Bq)
It is random (unpredictable)
Half life
The time it takes for half of the radioactive nuclei/isotope to decay
Uses of radioactivity
Radiocarbon dating
Radioactive tracers
Radiotherapy
Serilization
Radiocarbon dating
One in a billion carbon atoms is Carbon - 14
Once a plant or animal dies, this carbon 14 is not replaced and it decays over time.
Carbon 14 has a half life of 5700 years.
By measuring amount of carbon -14 in a dead organism we can determine when it died.
Radioactive tracing
Radioactive isotopes (technetium 99) with short half-life can be injected to humans.
Once in blood stream, emits gamma which penetrates the body and can be detected outside.
Isotope follows circulatory system, we can see any problems with heart, arteries or veins.
Same in digestive system
Radiotherapy
High intensity gamma rays to treat cancer.
Placing radioactive isotope near can kill cancer cells.
But can also kill healthy cells nearby
Sterilization
Gamma can be used to sterilize food and medical equipment.
Gamma penetrate food or equipment and kill bacteria on both sides.
Dangers of radioactivity when exposed to the body
- ionising radiation damages cells / tissues
- repeated damage can lead to mutations
- these mutations can be cancerous
Safety precautions
- minimise exposure time
- handle sources with tongs
- store sources in lead containers when not using
Contamination
when radioactive isotope is put into an object and emits radiation from INSIDE
Irradiation
when you expose an object radiation from OUTSIDE
3 Nuclear Reactions
Nuclear Fission
Nuclear Fussion
Radioactive Decay
Describe the process of nuclear fission
- a slow neutron is absorved by a nucleus
- the nucleus becomes unstable
- the nucleus splits (fissions) into 2 daughter nuclei
- 2 or 3 neutrons are emitted
Explain fow one fission leads to a chain reaction
- When a nucleus splits it releases neutrons
- These neutrons are absorved by other nuclei
- These also fission and the process repeats
Describe the use of CONTROL RODS
Absorbs neutrons and take them out of the fission process
Explain the use of CONTROL RODS
Controls rate of reaction (amount of energy released)
Describe the use of GRAPHITE MODERATOR
Absorb the kinetic energy of the neutrons and slow them down
Explain the use of GRAPHITE MODERATOR
So neutrons are slow enough to be absorbed by the nucleus (doesn’t bounce)
Describe the use of FUEL RODS
To produce energy
Describe the use of THICK CONCRETE SHIELD
Absorb neutrons and other radiations
Explain the use of THICK CONCRETE SHIELD
Radiation could lead to ionisation and cell mutation/cancer
Describe the use of GAS
Absorn heat energy and transfer the energy into the turbine
How do we control nuclear fission
- WHen control rods are fully inserted, chain reaction almost stops + heat production is low.
- When control rods are withdrawn, rate of fission increases and more heat energy is produced
Describe Nuclear Fusion
- 2 small nuceli collide
- join to create a larger nucleus
Nuclear fusion equation
H 2,1 + H 3,1 –> He 4,2 + n 1,0
State and explain the conditions needed for a nuclear fusion reaction
HIGH TEMPERATURE:
- Nuclei have a high kinetic energy
- to overcome the electrostatic repulsion
- between the positively charged nuclei
HIGH PRESSURE:
- lead to high density
- lead to high rate of collisions
