Nuclear Radiation Flashcards
What is ionisation?
Ionisation is when an electron is knocked off an atom (or added to an atom) producing a positive (or negative) particle
What are the features of alpha particles?
Two protons and two neutrons (a helium nucleus)
Travels a few cm in air
Absorbed by paper or skin
What are the features of beta particles?
Fast moving electron
Travels many cm in air
Absorbed by a few mm of aluminium
What are the features of gamma radiation?
Electromagnetic wave
Travels many km in air
Partially absorbed by lead
Name 4 natural sources of radiation
Radon gas from rocks and soil (partially granite)
Gamma rays from the ground
Carbon and potassium in body (from our food)
Cosmic rays from outer space
Name 3 artificial sources of radiation
Medical applications such as x-rays and radionuclides
Fallout feom weapons testing
Nuclear waste from power stations
What is activity?
The number of radioactive decays per second, measured in Bequerels (Bq)
What is half life?
The half life of a radioactive source is the time taken for its activity to reduce by half
Describe the 3 medical applications of nuclear radiation
Diagnosis - Injection of a radioactive tracer drug that goes to a specific area of the body and is detected using a Gamma Camera. Tracers emit gamma radiation.
Treatment - Gamma radiation can be used to kill cancer cells from outside the body.
Disease prevention - Medical equipment can be sterilised by exposure to gamma radiation
Describe some industrial applications of nuclear radiation
Radiation can be used to test welds without destroying them and find leaks in underground pipes. Some jobs expose workers to a higher dose of radiation than normal - these include miners and aircrew as well as nuclear power plants.
Describe the 2 main methods of reducing risk of harm from radiation (SID)
Shielding, e.g. using a lead apron, storing sources in lead lined boxes
Increasing distance from the radioactive source, e.g. using tongs to handle sources
What does the risk of harm from nuclear radiation depend on?
Absorbed dose
Type of radiation
Type of tissue
Time of exposure
What is absorbed dose measured in?
Grays (Gy)
What is equivalent dose measured in?
Sieverts (Sv)
What is eqivalent dose rate measured in?
Sv s-1, Sv h-1 etc.
What is nuclear fission?
Nuclear fission is when a heavy nucleus splits into two nuclei of smaller mass, releasing some neutrons and energy.
Describe the two types of nuclear fission
Spontaneous fission - this is very rare and happens when a very large nucleus is unstable enough to split into fission products by itself
Induced fission - this is caused by bombarding the nucleus with a neutron
Describe uncontrolled fission
Neutrons released in nuclear fission can cause fission in more nuclei, releasing more energy and more neutrons, which can cause further fission. This is a chain reaction.
How do you get more power from a nuclear fission reaction?
The neutrons released by the fission reaction are fast moving. A MODERATOR (e.g. graphite) is used to slow them down and INCREASE the chance of further fission reactions happening
How do you control the power from a nuclear fission reaction?
The reaction is managed using CONTROL RODS (e.g. boron) which absorb some of the slow neutrons
Describe nuclear fusion
Nuclear fusion is where two or more nuclei combine to form an element with a higher mass. This is the opposite of nuclear fission, but energy is still released in the reaction. Fusion takes place in the Sun and other stars.
How does a nuclear power station work?
The heat released by the nuclear reaction is used to produce steam in the heat exchanger. The steam is used to turn a turbine, which then turns a generator, producing electrical energy.
What are the advantages of nuclear power?
Nuclear power stations produce a large amount of energy for a small amount of fuel.
There are no carbon dioxide or sulphur dioxide emissions from a nuclear power station.
What are the disadvantages of nuclear power?
Nuclear waste must be stored securely for a very long time.
Many people have a negative view of nuclear fuel.
