P3.3 Production, uses and risks of ionising radiation from radioactive sources Flashcards
What is tritium?
A radioactive form of hydrogen
What does an atom consist of?
Protons, neutrons and electrons
What are nucleons?
Protons and neutrons
What is the atomic number?
The number of protons in an atom
What is the mass number?
The number of protons or neutrons in total
What is beta decay?
The emission of electrons or positrons when a radioactive material decays
What are beta particles?
Electrons and positrons
What is a positron?
The anti-particle of an electron, it has the same mass but opposite charge.
What are two types of beta (β) decay?
- beta minus decay (β-)
- beta plus decay (β+)
What happens during β- decay?
- A neutron becomes a proton
- an electron (beta particle) is emitted
What can beta minus decay penetrate?
Paper
What does ionising mean?
Capable of turning atoms into ions (charged particles)
What happens to an ion that loses an electron?
It becomes a positive ion
What happens to an ion that gains an electron?
It becomes a negative ion
What happens to the atomic and mass numbers after β- decay?
- the atomic number decreases by one
- the mass number is unaffected
What happens during β+ decay?
- a proton becomes a neutron
- a positron is emitted
What happens to the atomic and mass numbers after β+ decay?
- decreases the atomic number by one
- leaves the mass number unaffected
What can’t beta particles penetrate?
Thin sheets of metal
What is the charge of a positron?
+1
What are the three types of radioactive emission called?
- alpha (α)
- beta (β)
- gamma (γ)
What are alpha and beta emissions made up of?
Particles
What are gamma emissions?
Waves
What is an alpha particle made up of?
Two protons and two neutrons
What is the most penetrating type of radiation?
Gamma
What is the most ionising type of radiation?
Alpha
What is the least penetrating type of radiation?
Alpha
What is the least ionising type of radiation?
Gamma
Why are alpha particles the most ionising?
They are very big and so are easily capable of dislodging electrons from any atoms they collide with
Why are alpha particles the least penetrating?
Their big size means they have more collisions which means that they lose energy quickly and so have a limited range
What happens to the atomic number and mass after alpha decay?
The atomic number decreases by two and the mass number decreases by four
What happens during alpha decay?
The nucleus emits an alpha particle
What happens during gamma decay?
The nucleus emits a gamma ray
What absorbs gamma rays?
A few centimetres of metal
Why does an unstable nucleus undergo decay?
To become stable
What happens to the atomic and mass number after gamma radiation?
Nothing
Why does gamma radiation cause no change in atomic and mass number?
Because it has no mass
How does gamma decay make radioactive materials stable?
When gamma rays are emitted the nucleus loses energy
What is neutron radiation equal to in terms of penetration?
Gamma radiation
What is neutron radiation?
The emission of a neutron during radioactive decay
Why aren’t neutrons ionising?
They have no charge
What must be the same on each side of a nuclear reaction?
The atomic and total mass number
What type of nucleus is an alpha particle?
A helium nucleus
What is an alpha particle written as in a nuclear reaction?
4
He
2
What is an electron written as in a nuclear reaction?
0
e
-1
What is a positron written as in a nuclear reaction?
0
e
+1
What is a gamma ray written as in a nuclear reaction?
0
γ
0
What do all isotopes of an element have in common?
The same number of protons
What causes there to be different isotopes within an element?
Different numbers of neutrons
What does it mean when an isotope is stable?
It will keep the same number of protons and neutrons indefinitely
What happens to unstable isotopes?
They decay
What does a stability curve graph show?
How likely it is an isotope will decay and what kind of decay it will undergo
Where are lighter elements found on the stability curve graph?
The bottom left corner
Where are heavier elements found on the stability curve graph?
Towards the top right
What does the straight line N=Z show on a stability curve graph?
Where elements will appear if they have the same number of protons as neutrons
What does a line called the N-Z curve show on a stability curve graph?
Stable isotopes
What is another name for the N-Z curve?
A stability curve
Where does the stability curve stop at?
Z=82
Why does the stability curve stop at Z=82?
Above this all isotopes are unstable
What kind of decay do isotopes above the N-Z curve undergo?
β- decay
Why do isotopes above the N-Z curve undergo β- decay?
They have too many neutrons to be stable
Why are isotopes below the N-Z curve likely to undergo β+ decay?
They have too many protons
What two types of radiation are isotopes below the N-Z curve likely to undergo?
β+ and α radiation
What state are radioactive isotopes in?
Unstable
Where are the isotopes of the heaviest elements likely to be found on the N-Z stability graph?
Towards the top right when Z ≥ 82
What type of decay do many isotopes of the heaviest elements usually undergo?
Alpha
What are protons and neutrons made up of?
Quarks
What type of particles are protons and neutrons?
Hadrons
What mass does an up quark have?
1/3
What mass does a down quark have?
1/3
What charge does an up quark have?
+2/3
What charge does a down quark have?
-1/3
What quarks does a proton consist of?
Two up quarks and one down quark (udu)
What quarks does a neutron consist of?
One up quark and two down quarks (dud)
How many quarks does one neutron or proton contain?
Three
Why can protons change into a neutron and vice versa?
Because quarks can change from one type to another, e.g. down to up or up to down
What type of decay does an element undergo when an up quark changes into a down quark?
β+
What type of decay does an element undergo when a down quark changes into an up quark?
β-
How can radiation cause cancer?
It damages DNA within living cells which can cause mutations which can lead to cancer
What does dosage mean in radiation treatment?
The total amount of radiation absorbed by the patient
What two factors does the likelihood of getting burns from radiation depend on?
- the amount of exposure
- the type of source
What type of radiation burns look similar to sunburn?
Beta
How far do beta burns reach?
The surface of the skin
What type of radiation causes the deepest burns?
Gamma
Why does gamma radiation cause the deepest burns?
It is the most penetrating
How do medical staff minimise their exposure to radioactive sources?
- increasing their distance from the source
- shielding
- containment
- minimising the amount of time spent in its presence
How is the amount of radiation medical staff are exposed to monitored?
Using a dosimeter
What are two reasons why patients might be exposed to radiation?
Diagnosis and treatment
What is radiotherapy used for?
Treating cancers and palliative care
What type of radioactive source is used for internal radiotherapy?
A beta emitter
What type of radioactive source is used for external radiotherapy?
A gamma source or high frequency X-rays
What is palliative care?
A medical intervention that doesn’t cure a condition but may reduce pain and other symptoms
How can radiotherapy be used in palliative care?
It can shrink tumours
What is a tracer?
A substance which is usually used by the body which is made using atoms from radioactive isotopes
Why are some tracers used directly instead of being incorporated into larger molecules?
They are already directly absorbed by some parts of the body
How does a tracer diagnose cancer?
They are more concentrated in areas where there are diseased tissues or tumours, which show up in a PET scan
Why does a tracer need to have a short half-life?
So that other parts of the body are affected as little as possible
What locates the tracer?
a PET scanner
What tracer does the brain absorb?
Technetium-99
What tracer does the thyroid gland absorb?
Iodine-123
What tracers do the lungs absorb?
Nitrogen-13 and oxygen-15
What tracer do the bones absorb?
Indium-111
What happens when a positron collides with an electron?
Total annihilation, two gamma rays are released in opposite directions
How does a PET scan detect tracers?
It emits electrons which collide with the positrons emitted from the tracers. This releases two gamma rays which are released in opposite directions and are detected by the PET camera. The computer can then use triangulation to see where the rays came from and so can see where the highest concentration of tracer and therefore diseased cells or tumours are
Why do all medical radioactive techniques carry a risk?
They increase the amount of exposure to patients
What is the speed of a gamma ray?
The speed of light
