Radioactivity Flashcards
What is nuclear fusion?
The joining of small nuclei
What happens in nuclear fusion?
Two light nuclei collide at high speed and join together to form a heavier nuclei
What happens to some of the mass in nuclear fusion?
Some of the mass is converted into energy and is released.
What types of conditions need to present for nuclear fusion?
There needs to be high temperatures and pressure
Why does the pressure need to be high for nuclear fusion?
The positively charged nuclei have to get very close to fuse, so the strong force due to electrostatic repulsion has overcome
What are the advantages of nuclear power?
- It is a safe way of generating electricity
- It is a very reliable energy resource and reduces the need for fossils fuels
- Does not release carbon dioxide
- Huge amounts of energy can be generated from a relatively small amount of nuclear energy
What are the disadvantages of nuclear power?
- They have very long half-lives meaning they will be radioactive for years
- It has to be stored for years as they are very radioactive
- Can be used for bombs which can cause terror attacks
- Risks that they can leak if not store correctly causing major catastrophes
- It is expensive
What is nuclear fission?
The splitting up of big atomic nuclei which cause a chain reaction
What happens in nuclear fission?
- A slowing-moving neutron is fired at a large unstable nucleus (uranium-235)
- The neutron is absorbed by the nucleus which causes the nucleus to split into two lighter daughter nuclei
- energy is released
- two or three neutrons are released causing a chain reaction
Why are PET scans useful?
- They can help diagnose illnesses
- They show tissue and organ function
What is the first step of a PET scan?
- inject the person with a substance used in the body which includes a positron emitting radioactive isotope with a short half -life
- this is a tracer
What is electron-positron annihilation?
occurs when a negatively charged electron and a positively charged positron collide causing both of them to be destroyed and release gamma rays
What happens in the second step of a PET scan?
- Positron meets the electron in the organs causing annihilation
- this causes high-energy gamma rays in opposite directions to be emitted
- and are detected by detectors detect pairs of gamma rays where the tumours will lie along the same path of the pairs
- the tumour is detected accurately by triangulation
Why does the distribution of the radioactivity match up with the metabolic activity?
More of the radioactive substance injected into the patient is taken up and used by cells that are doing more work ( cells with an increased metabolism)
Why do isotopes used in PET scans have a short half-life?
So that they can become less radioactive quicker overtime
What types of radioactive sources are more dangerous?
Those with a longer half-life. A source may be more radioactive however it can have a short half-life but a source that isn’t as reactive can be more dangerous if it has a longer half-life
What type of radiation do household fire alarms use?
Alpha Radiation
How do household fire alarms use alpha radiation?
- A weak source of alpha radiation is place inside the smoke detector which is close to two electrons
- The source cause ionisation, and a current of charged particles to flows
- when there is a fire the smoke will be absorbed by the charged particle
- when the current stops, the alarm begins to ring
What type of radiation is used to sterilise food and equipment?
Gamma rays
How are gamma rays used to sterilise food and equipment?
- can kill all microbes with high doses of gamma rays cause the food or equipment to not be damaged
- have a long half-life so they dont need to be replaced often
What do electrons sit in?
Different energy levels or shells with each level being a different distance from the nucleus
How can an electron move up to a higher energy level?
if it absorbs EM radiation with the right amount of energy to a empty or partially filled shell
What is the term when an electron moves up an energy level?
excited
How can an electron move up to a lower energy level?
after moving up they quickly move to their original energy level and will emit the same amount of energy it absorbed
Isotope definition
atoms with the same number of protons but a different number of neutrons
What are alpha particles and their properties?
- helium nuclei
- dont penetrate very far into materials and ae stopped quickly
- they can only travel a few cm in the air
- are absorbed by a thin piece of paper
- it is ionising due to its size
What are beta-minus particles and their properties?
- fast moving electron released by the nucleus
- mass of 1/1836
- charge of -1
- moderately ionising
- can travel a few metres in the air
- are absorbed by a sheet of aluminium
What are beta-plus particles and their properties?
- fast moving positron
- same mass of 1/1836
- charge of +1
- moderately ionising
What are gamma rays and their properties?
- gamma rays are waves of EM radiation released by the nucleus that carry away energy produced in nuclear rearrangement
- penetrate through materials without being stopped
- weakly ionising as they pass through rather than colliding with atoms
- can be absorbed by thick lead or concrete
What is activity measured in?
Bq (Becquerels)
- 1 Bq = 1 decay per second
How can activity be measured?
Geiger-Muller tube
What is half life?
The half-life is the average time taken for the number of radioactive nuclei in an isotope to halve
What is background radiation?
Low level radiation that’s around us all the time?
What are examples of background radiation?
- natural occur due to unstable isotopes
- from space
- human activity
What is irraduiation?
Being exposed to a radioactive sources
What is contamination?
Unwanted radioactive atoms get onto an object
What is a moderator?
used slow down the fast-moving neutrons
What is are the control rods?
- made of boron
- limit the rate of fission by absorbing excess neutrons
- they can be placed in-between the fuel rods
- they are raised and lowered into the reactor to control the chain reaction
