7 Flashcards
Describe Alpha particles?(3)
When unstable isotopes decay, they could release alpha particles. Alpha particles are two neutrons and two protons - Helium nuclei.
They don’t penetrate very far into materials and can only travel a few cm in air and absorbed easily
Their size means they are strongly ionising.
Describe Beta particles?(3)
A beta minus particle is a fast moving electron, which have virtually no mass and a charge of -1.
A beta plus particles is a fast moving positron which has same mass as the electron but +1 charge.
They are both moderately ionising, the Beta minus have a range of a few metres, while Beta plus have smaller range.
Describe Gamma Rays?(3)
After a nuclear decays it usually has a nuclear rearrangement and releases gamma rays to carry away the energy.
They penetrate far into materials and travel long distance in air.
This means they are weakly ionising because they pass through rather than collide with atoms.
What is ionisation?
Ionisation is the turning of an atom into an ion by gaining or losing electrons.
What are the mass numbers and charge of each type of radiation?(3)
Alpha have a mass of 4, and a +2 charge.
Beta have a mass of 0 and a -1 charge.
Gamma have a mass of 0 and 0 charge.
How is radioactive decay measured?(4)
Activity is the rate in which something decays, it is measured in becquerels, Bq.
1 Bq is 1 decay/second.
A Geiger-Müller tube clicks every time it detects radiation.
Photographic film can also be a measure; the more radiation it is exposed to the darker it becomes.
What is half-life?(3)
The half life is the average time taken for the number of radioactive nuclei in an isotope to halve.
A short half-life means the activity falls quickly because the nuclei are very unstable and rapidly decay. Long half-life is the opposite.
Short half life sources are very dangerous but become safe quickly, while long-half life sources are dangerous because they can expose nearby areas to radiation for a long time.
What are the sources of Background radiation?(3)
Radioactivity of naturally occurring unstable isotopes, which are everywhere.
Radiation from space, cosmic rays. These are mostly from the sun.
Radiation from human activity, like a nuclear explosion.
Define irradiation.
Irradiation is the process in which objects are exposed to radiation. This does not make it radioactive.
How can radiation damage the body?(2)
Radiation can enter living cells and ionise atoms and molecules within them. This can lead to tissue damage.
Lower doses give rise to mutant cells which is cancer, while higher doses will kill cells completely.
What is nuclear fission?(2)
Nuclear fission is a nuclear reaction that is used to release energy from uranium or plutonium atoms. The fission of U-235 specifically produces two radioactive daughter nuclei and a small number of neutrons, this therefore will cause a chain reaction if one of these neutrons strike another U-235.
Huge amounts of energy is released in this way through a chain reaction.
How is the rate of fission controlled in a nuclear Power-plant?(3)
The neutrons need to be moving slowly in order to be easily absorbed by Uranium. They can be slowed by graphite or water, which are called moderators.
In order for a stable rate of fusions there are control rods which can be raised or lowered to increase or decrease rate of fission. Made from elements like Boron.
Furthermore, there will be lots of concrete surrounding the whole core in order to reduce the amount of radiation that escapes.
What is nuclear fusion?(2)
Creates energy by fusing two light elements rather than splitting one heavy element(fission). This loss of mass produces energy.
Much more sustainable as the reactants are much more abundant(hydrogen) but no one has found a way to make it produce more energy than is used.
Why is nuclear fusion not a good source of energy as of now?
Hydrogen nuclei both have +1 charge, therefore the atmosphere pressures and temperatures can’t be low otherwise the nuclei will repel(like charges repel).
Define isotope.
The number of protons in an atom identifies the element. Therefore, an isotope is an atom of an element with a different number of neutrons.
