Radioactivity And Ionising Radiation Flashcards
What is a proton
Realtime mass 1
Charge +1
What is a neutron
Mass 1
Charge 0
What is an electron
Mass 1/2000
Charge -1
What is alpha
A helium nucleus
Slow and heavy
Strongly ionising
Stopped by paper and skin
What is beta
An electron
Light and fast
Moderately ionising
Stopped by thin metals
What is gamma
Electromagnetic wave
No mass very fast
Weakly ionising
Stopped by thick lead or very thick concrete
What is a positron
It is an anti particle of an electron
Relative mass 1/2000
Charge +1
They have the same properties as an electron
If they meet an electron they are annihilated
What is neutron radiation
They are more penetrating than alpha beta or gamma
They’re not directly ionising but can be absorbed by nuclei of atoms in substances they pass through
Absorbing a neutron can make a nucleus radioactive
Neutrons are absorbed best by light nuclei such as hydrogen
Often neutron absorption makes nuclei emit gamma radiation
What makes a nucleus unstable
Too many neutrons
Too few neutrons
Too many protons and neutrons together
Too much energy
What does the curve of stability show
Any isotope not on the curve is unstable
An isotope above the curve has too many neutrons to be stable
An isotope below the curve as too few neutrons to be stable
When does beta- decay happen
When there are too many neutrons
What happens in beta- decay
Emission of an electron from the nucleus
It happens when there’s more neutrons than protons so one of the neutrons is changed into a proton
The proton number is increased by one and the mass number stays the same
When does beta+ decay happen
When there are too few neutrons
What happens in beta+ decay
A positron is emitted from the nucleus
A proton gets changed into a neutron
So the proton number decreases by one and the mass number stays the same
When does alpha decay happen
When there are navy atoms with a z value (number of protons) above 82 like uranium and radium
What happens is alpha decay
A helium nucleus is emitted
The proton number decreases by two and the mass number decreases by four
When does gamma radiation happen
After alpha or beta decay the nucleus has lots of energy
What happens in gamma radiation
It always goes with alpha or beta decay there’s no change in the proton on mass number of the atom
What are quarks
Small particles that make up protons and neutrons
Describe an up quark
Charge 2/3
Mass 1/3
Describe a down quark
Charge -1/3
Mass 1/3
What is a proton made up of
Two up quarks and one down quark
The charge is 2/3+2/3+{-1/3} = 1
The mass is 1/3+1/3+1/3=1
What is a neutron made up of
One up quark and two down quarks
Charge is 2/3 +{-1/3}+{-1/3}
Mass is 1/3+1/3+1/3
What happens when a neutron is turned to a proton
A down quark turns into an up quark
The overall charge still has to be 0 so an electron is also produced
What happens when a proton turns into a neutron
An up quark turns into a down quark and a positron is released
How are radioactive isotopes used in tracers
The trader is injected into the the patient or swallowed and an external detector follows its process as it moves around the body
A computer uses these images to create and image of where the strongest radiation comes from
Only isotopes with beta and gamma are used because they can pass out of the body they also have short half lives to reduce the amount of radioactivity inside the patient
How is iodine 131 used in tracers
It is absorbed into the thyroid gland it gives out radiation which can be detected to indicate if the thyroid gland is taking in iodine like it should
What are pet scans used for
They show areas of damaged tissue in the heart by detecting areas of decreased blood flow
This can show coronary heart disease or damaged or dead heart muscle caused by heart attacks
They can record blood flow and activity in the brain to diagnose diseases like epilepsy
They can identify active cancer Tumors by showing metabolic activity in tissue cancer cells have a much higher metabolism than healthy cells because they grow fast
How do pet scans work
Inject the patient with a substance used by the body e.g. Glucose containing a positron emitting radioactive isotope
Positrons meet electrons and annihilate emitting high energy gamma rays which are detected
The distribution of radioactivity matches up with metabolic activity this is because more of the radioactive substance is taken into the cells that have increased metabolism
Why do hospitals have their own cyclotrons
The isotopes in pet scanning have short half lives so it’s important they’re made close to where they are used otherwise the isotopes could have to be transported over long distances and their activity could be low by the time they are used so they’re no longer useful
How does ionisation effect cells
It can kill a cell completely or damage it so it can’t divide causing tissue damage
It can change the genetic material in a cell this can cause mutations or make the cell divide and grow uncontrollably this is what causes cancer
How is exposure to radiation limited
The lowest possible doses of radiation is used and a short exposure time
The patients could wear lead shielding to protect areas not being treated
Intensity decreases with distance so the staff should stand well away from the source
Staff can wear lead aprons or lead lined clothing to stop the radiation
The radiation dose must be carefully monitored
How is radiation used internally to treat tumours
Internal radiation therapy means a radioactive material is placed inside the body into or near the tumour this can be done by injections or implanting a small amount of a radioactive substance this gives a high dose of radiation to a small part of the body limiting damage to the normal tissue
How are tumours treated externally
Using high energy x rays or gamma rays aimed at the tumour
The radiation is focused at one part of the body but can affect healthy cells
What are the pros internal radiation therapy
It is shorter than using external radiation methods so reduces the amount of visits a patient has to take to hospital
It has few side effects apart from some discomfort from the implant
What are the bad things about internal radiation
They can cause the person to emit radiation after the source is emitted so they may have to limit contact with people until it is removed
Where as external sources mean the radiation only lasts a few minutes and they’re not radioactive now
What are the downsides of using radiation in treatment
Even if precautions are taken the radiation can still harm some healthy cells leading to side effects such as sickness hair loss and skin irritation
There are long term effects such as bowel damage or infertility
The person could develop a second cancer caused by the treatment of the first treatment
Some people may refuse treatment because of these risks
Why do some people chose to ignore the risks of radiation therapy
It doesn’t always lead to a cure but can be used to reduce suffering this is known as palliative care
It increases their life expectancy even if one of the risks were to happen their life would still be longer
What are the ethical arguments against testing radioactive techniques
The new techniques could have harmful side effects but doctors won’t know for certain what the side effects are until it is tested on humans
Lots of patients might want to get onto the medical trial but places are limited
When a trial seems to work how long should it be before it is offered to anyone else because of the long term effects
How are treatments tested
First on cells then animals then humans
