Radioactivity Flashcards
What are the main particles that make up an atom?
Protons, neutrons, and electrons
Protons and neutrons are found in the nucleus, while electrons orbit the nucleus.
What is the atomic number of an atom?
The number of protons in the atom
The atomic number also equals the number of electrons in a neutral atom.
What does the mass number of an atom represent?
The total number of protons and neutrons
It does not include electrons.
Define isotopes.
Atoms of the same element with the same number of protons but different numbers of neutrons
Isotopes can have different physical properties.
What is background radiation?
Nuclear radiation that we are exposed to all the time
It is emitted by natural and artificial sources.
List some sources of background ionising radiation.
- Radon gas from igneous rocks
- Radioactive substances in food and air
- Building materials like granite
- Artificial sources like medical treatments and nuclear waste
What is cosmic background radiation?
Radiation that comes from the sun
It is a component of background radiation.
What is ionising radiation?
Radiation strong enough to remove an electron from an atom
It can be dangerous to living organisms.
What are the three types of ionising radiation?
- Alpha particles
- Beta particles
- Gamma rays
Describe an alpha particle.
Consists of two protons and two neutrons
It is strongly ionising but not very penetrating.
Describe a beta particle.
A high-speed electron
It is moderately ionising and more penetrating than alpha particles.
What are gamma rays?
Very high frequency electromagnetic waves
They are produced when an unstable nucleus loses energy.
True or False: Alpha particles are highly penetrating.
False
Alpha particles are not very penetrating.
Fill in the blank: The atomic number is equal to the number of _______.
Protons
Fill in the blank: Isotopes have the same number of protons but different numbers of _______.
Neutrons
Properties of alpha particle?
Strongly ionising and so not very penetrating.
Properties of beta particle?
Moderately ionising and more penetrating than alpha.
Properties of gamma rays?
They are weakly ionising and very penetrating.
When are gamma rays produced?
When an unstable nucleus loses energy.
What stops an alpha source?
A few sheets of paper.
Alpha particles are relatively large and can be stopped by light materials.
What stops a beta source?
A few millimetres of aluminium.
Beta particles are lighter than alpha particles and require denser materials for shielding.
What stops gamma rays?
A few centimetres of lead.
Gamma rays are highly penetrating and require substantial density to be effectively stopped.
Which type of radiation is the most penetrating?
Gamma rays.
Due to their lack of charge and high energy, gamma rays are the least easily stopped.
What equipment can detect all three types of radiation?
Geiger-Muller detector.
This device can detect ionising radiation, including alpha, beta, and gamma radiation.
What must you remember to do when measuring radiation with a Geiger-Muller detector?
Subtract the background radiation.
This is done by measuring the count rate with the source removed.
In a magnetic field, how are alpha and beta particles deflected?
In opposite directions.
This occurs due to their opposite charges.
Why are alpha particles deflected less than beta particles?
Alpha particles have a larger mass.
Their greater mass means they are less affected by magnetic fields.
How are gamma rays affected by magnetic fields?
They are not deflected.
Gamma rays are uncharged and thus unaffected by magnetic fields.
In an electric field, how do alpha and beta particles behave?
They are deflected in opposite directions.
This deflection is due to their opposite charges.
Why do alpha particles experience less deflection in electric fields compared to beta particles?
Due to their much larger mass.
Heavier particles are less responsive to electric forces.
What happens to gamma rays in electric fields?
They aren’t deflected.
Gamma rays, being uncharged, do not interact with electric fields.
What occurs when a radioactive isotope decays?
Its nucleus changes from an unstable to a more stable state and gives out energy as ionising radiation
Decay is a random process.
What types of decay result in a change of atomic number?
Alpha and beta radiation
Gamma decay does not change the atomic number.
What happens during alpha decay?
An alpha particle (helium nucleus) is emitted, consisting of two protons and two neutrons, resulting in the atomic number decreasing by 2 and the mass number decreasing by 4
Example: 238/92 U -> 234/90 Th + 4/2 He.
What is emitted during beta decay?
An electron is ejected when a neutron in the nucleus changes into a proton
The atomic number increases by 1 while the mass number remains the same.
What is the effect of gamma decay on atomic and mass numbers?
The mass and atomic number stay the same
This occurs as particles in the nucleus rearrange to a more stable position by releasing excess energy.
Fill in the blank: In alpha decay, the atomic number goes down by _______.
2
Fill in the blank: In alpha decay, the mass number goes down by _______.
4
True or False: Gamma decay results in a change of atomic number.
False
What is the outcome of a neutron changing into a proton during beta decay?
The atomic number increases by 1 while the mass number stays the same.
What does an alpha particle consist of?
Two protons and two neutrons
Example of a nuclear equation for alpha decay?
238/92 U -> 234/90 Th + 4/2 He
What rearranges during gamma decay?
Particles in the nucleus
What type of radiation is emitted during gamma decay?
Gamma rays
What is half-life in the context of radioactivity?
The time taken for the activity of a radioactive source to decrease to half the initial value or the time it takes for half of the nuclei of the isotope to decay into another isotope.
How is the activity of a radioactive source measured?
In Becquerels (Bq).
What happens to the activity of a radioactive source after n half-lives?
It equals 1 / 2° of the original value of activity.
What is radiocarbon dating?
A method that estimates the age of organic material by measuring the amount of radioactive carbon-14 it contains.
What is the half-life of carbon-14?
About 5600 years.
How do living organisms contain carbon-14?
Plants absorb carbon-14 during photosynthesis, and animals consume plants and each other.
What happens to carbon-14 levels when an organism dies?
The proportion of carbon-14 decreases as it decays.
What are the limitations of radiocarbon dating?
Only works with organic material, destroys the sample, assumes constant carbon-14 proportion, requires a reasonable amount of material, and is only accurate up to around 10 half-lives.
What is the purpose of radiotherapy?
To target cancer cells with radiation emitted from outside the body to kill or reduce tumor size.
What characteristics should radiation have for effective radiotherapy?
- Long half-life
- Gamma radiation to penetrate the body
- Non-toxic as it does not enter the body.
What are medical tracers used for?
To check if all organs are working properly by showing where a tiny amount is absorbed.
What characteristics should medical tracers have?
- Short half-life
- Gamma radiation to be picked up from outside the body
- Non-toxic as it enters the body.
What is used to trace underground leaks in pipes?
A radioactive tracer can be added to a fluid e.g. gas
The leak is indicated by an increased count rate in that area.
What type of radiation is used for sterilisation?
Ionising radiation
Strong sources can kill micro-organisms, used on medical instruments and food.
What does automatic thickness monitoring depend on?
The amount of radiation received by the detector
This allows adjustments to the thickness of materials like aluminium.
How do smoke detectors function?
An alpha emitter ionises an air gap
Smoke absorption of alpha particles drops current, triggering the alarm.
What type of radiation can penetrate the skin and damage cells?
Beta and gamma radiation
They can damage tissues and organs if they penetrate the skin.
Which type of radiation is very dangerous if it gets inside the body?
Alpha radiation
It cannot penetrate the skin but can be harmful when internal.
What happens when radiation collides with molecules in cells?
Causes ionisation, damaging or destroying molecules
This can lead to cell mutations and cancer.
What is the effect of lower doses of radiation?
Tends to cause minor damage without killing the cell
This can potentially lead to mutations and cancer.
Fill in the blank: A _______ tracer can be used to trace underground leaks.
radioactive
The tracer is non-toxic and has a short half-life.
True or False: Gamma radiation is used for sterilisation because it has a long half-life.
True
Long half-life is beneficial for sterilisation processes.
What is the purpose of using alpha radiation in smoke detectors?
To ionise an air gap and conduct electricity
This allows the detector to sense smoke by a drop in current.
What type of radiation is typically used in automatic thickness monitoring?
Beta radiation
It is used for monitoring the thickness of materials like aluminium.
What is radiation sickness?
A condition caused by high levels of radiation exposure that can kill cells completely.
How is low-level radioactive waste typically disposed of?
By burying it in landfill sites.
What is the primary challenge in disposing of high-level radioactive waste?
It is hard to get rid of and is often sealed in glass blocks and buried deep underground.
What factors must be considered when finding a suitable place for high-level waste disposal?
Must not be in an earthquake-prone area to prevent leakage and contamination.
What is contamination in the context of radioactivity?
When unwanted radioactive atoms get onto or into an object.
What is a potential consequence of contamination?
Contaminated atoms may decay, releasing radiation and causing harm.
What safety measures should be taken when handling radioactive sources?
Use gloves and tongs to prevent contamination.
What is irradiation?
The exposure of objects near a radioactive source without making them radioactive.
What are some methods to reduce the risk of irradiation?
- Keeping sources in lead-lined boxes
- Standing behind barriers
- Using remote controls
What is nuclear fission?
A nuclear reaction that can be a source of energy, involving the splitting of a fissile material.
What is the most commonly used fissile material?
Uranium-235.
What are the products of a nuclear fission reaction?
- Two daughter nuclei (fission fragments)
- Neutrons
- Gamma radiation
- Kinetic energy
What initiates the process of nuclear fission?
A collision with a slow-moving neutron
This collision leads to the absorption of the neutron by Uranium-235.
What unstable isotope is formed when Uranium-235 absorbs a neutron?
Uranium-236
What is produced when Uranium-236 splits apart during fission?
Two daughter nuclei and additional neutrons
What is a chain reaction in the context of nuclear fission?
A process where the fission of one nucleus causes further fissions in other nuclei
Fill in the blank: The fission of uranium-235 can be initiated by a _______.
slow-moving neutron
What are the components of a nuclear power station?
Control rods, boiler, steam, turbine, generator, condenser, nuclear reactor
What material are moveable control rods typically made of?
Boron
What effect do control rods have when moved down between fuel rods?
They absorb neutrons and slow the rate of reaction
What happens to uranium fuel rods during fission?
They become very hot and radioactive
What is the purpose of adjusting the depth of control rods in a nuclear reactor?
To maintain a constant rate of fission
True or False: The coolant in a nuclear reactor is always hot.
False
What type of core is commonly used in a nuclear reactor?
Graphite core
What structure encases the reactor vessel in a nuclear power station?
Concrete shield
Fill in the blank: The coolant enters the reactor vessel _______.
cold
What is the primary function of the generator in a nuclear power station?
To produce electricity
What is the function of the moderator in a nuclear reactor?
Surrounds fuel rods and slows down neutrons to increase absorption likelihood
This process kickstarts nuclear fission.
What role does the coolant play in a nuclear reactor?
Transfers thermal heat energy from fuel rods to the heat exchanger
An example of a coolant is water.
How does the heat exchanger work in a nuclear reactor?
Converts water into high pressure steam using heat energy from the coolant
This steam turns the turbine, which generates electricity.
What is the purpose of the concrete shield in a nuclear reactor?
Absorbs radiation such as high energy neutrons and gamma rays
This protects against ionising radiation emitted from the reactor.
Define nuclear fusion.
The joining of two atomic nuclei to form a larger one
This process releases energy.
What is the mass comparison of the larger nucleus formed in nuclear fusion?
The larger nucleus has a smaller mass than the combined masses of the two smaller nuclei
Energy is released during this process.
What element undergoes fusion in stars to create helium?
Hydrogen nuclei
This process releases a significant amount of energy.
Which releases more energy for a given mass of fuel, fusion or fission?
Fusion
It releases more energy than fission.
What conditions are necessary for nuclear fusion to occur?
High temperatures and pressures
This is required to overcome the electrostatic repulsion between positively charged nuclei.
True or False: Nuclear fusion can occur at low temperatures and pressures.
False
High temperatures and pressures are necessary for fusion.
Why are current nuclear fusion reactors not economically viable?
The temperatures and pressures required are too high
Scientists are still working on developing viable fusion reactors.
Why are high temperatures and high pressure needed for nuclear fusion?
The particles need to be moving very fast to overcome the strong forces of electrostatic repulsion.
