P4 Flashcards
What is the radius of an atom
Around 1×10^ -10 m
What do radioactive substances always give out and from where
– Radiation from nuclei of atoms
What does a short half life mean and why does it occur
– Activity falls quickly because the nuclei are very unstable and rapidly decay
Describe the safety of sources with a short half life
– Can be dangerous because of the high amount of radiation they omitted the start
– quickly become safe
What does a long half life of a substance mean and why does it occur
– Activity falls more slowly because most of the nuclei don’t decay for a long time
Describe the danger of substances with a long half life
– Source just sits there are releasing small amounts of radiation for a long time
– can be dangerous because nearby areas are exposed to radiation for (millions of) years
What is background radiation and what should you always do with it when experimenting to avoid what
– The low-level radiation that is around us all of the time
– should measure and subtract the background radiation from your results to avoid systematic errors
Where does background radiation come from
– Radioactivity of naturally occurring on stable isotopes which are all around us – in there, food, building materials and rocks under our feet
– radiation from space which is known as cosmic rays – mostly from Sun – earths atmosphere protect us from much of this radiation
– radiation due to human activity e.g. fallout from nuclear explosions or nuclear waste – represents tiny proportion of the total background radiation
What does radiation dose tell you and what is it measured in
– The risk of harm to body tissues due to exposure to radiation
– sieverts (Sv)
What is the dose of background radiation often measured in and why
– millisieverts
– the dose from background radiation is small
What is your radiation dose affected by
– Where you live
– whether you have a job that involves radiation
– other factors such as having x-rays
What is irradiation
Exposure to radiation
What does and doesn’t irradiating something do
– Exposes it to the radioactive source
– doesn’t make it radioactive
What are ways of reducing irradiation when working with radioactive sources
– Keeping sources in lead lined boxes
– standing behind barriers
– being in a different room and using remote-controlled arms
What is a substance said to be if unwonted radioactive atoms get onto or into it and what is an example
Contaminated
If you touch a radioactive source without wearing gloves your hands would be contaminated
Why is radioactive contamination especially dangerous
Radioactive particles could get inside your body
What can be used to reduce radioactive contamination
Gloves and tongs when handling sources to avoid particles getting stuck to your skin or and your nails
Some industrial workers wear protective suits to stop them breathing in particles
What are the most dangerous type of radioactive sources outside of the body and why
– Beta and gamma
– they can penetrate the body and get into delicate organs
– alpha less angels because it can’t penetrate skin and is easily blocked by small airgap
– high levels of irritation from all sources are dangerous but especially ones that emit beta and gamma
Which type of radioactive source is the most and least dangerous inside of the body and why
– Alpha
– they do all of their damaged in a very localised area so contamination rather than irritation is the major concern
– Beta less damaging inside the body as radiation is absorbed over a wide area and some passes out of body altogether
– gamma least dangerous inside body as they mostly pass straight through – lowest ionising power
Why is It’s important that research about different types of radiation and how they affect our bodies is published and what happens to the data before publishing and what does this lead to
– It means we can understand about how different types affect our bodies – we can protect ourselves when using them
– peer reviews – quickly become accepted – many improvements in our use of radioactive sources
What is nuclear fission
A type of nuclear reaction that is used to release energy from large and unstable items e.g. uranium or plutonium by splitting them into smaller atoms
What usually has to happen to the nucleus before it will split and what does this mean
– Absorb a neutron
– spontaneous (and force) sufficient rarely happens
LOOK AT NUCLEAR FISSION DIAGRAM
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What happens when the atom splits
Its forms two new lighter elements that are roughly the same size and have some energy in their kinetic energy stores
Two or three neutrons also released – if any of these neutrons are moving slow enough to be absorbed by another nucleus, they can cause more fission to occur – chain reaction
What happens to the energy not transferred to the kinetic energy stores of the products of nuclear fission
Carried away by gamma rays
What can the energy carried away by gamma rays and in kinetic energy stores of remaining three neutrons and other decay products of nuclear fission be used for
To heat water, making steam to turn turbines and generators
What is the amount of energy produced by fission in a nuclear reaction controlled by and how is this done
– Changing how quickly the chain reaction can occur
– using control rods which when lowered and raised inside a nuclear reactor, absorb neutrons – slows down the chain reaction and controls the amount of energy released
How do nuclear weapons work
Uncontrolled chain reactions quickly lead to lots of energy being released as an explosion
What happens during nuclear fusion And what is an example
Two light nuclei collide at high speed and join to create a larger, heavier nucleus
E.g. hydrogen nuclei confused to produce a helium nucleus
Describe the heavier nucleus formed in nuclear fusion
– Not as much mess as the two separate nuclei did – some of the mass of the light to nuclei converted to energy – energy then released as radiation
Does fusion release a lot or a little bit of energy
A lot
Have scientists so far found a way of using fusion to generate energy for us to use and why
No – the temperatures and pressures needed for fusion are so high that fusion reactors are really hard and expensive to build
