Topic 5 Flashcards
Where does all radioactivity come from
Unstable reactive isotopes undergoing nuclear decay and spitting out high-energy particles or waves
What is given of when unstable nuclei decay
Ionising radiation
Radioactivity is a ……..process
Random
When the nucleus does decay it will give out one or more of the three types of ionising radiation
In the process what happens
It will change into a new element
What is ionisation
When an atom loses or gains an electron becoming an ion
Alpha beta gamma cause
Ionisation of atoms
What do radioactive isotopes do
Decay into other elements and give out radiation
Alpha particles have a large ……. Charge
Positive
Therefore pull negatively charged electrons out of atoms orbit
Beta particles are …….. Charged
Negatively
Put electrons out of atoms orbit beeping them
How do gamma rays cause ionisation
They interact with electrons orbiting atom transferring energy to them
If election gets enough energy it can break free from atom
The more ionising the radiation is
The less penetrating it is
Why is more ionising radiation less penetrating
Because it gives up its energy quickly as it creates ions
Don’t penetrate far
Alpha particles travel at a …….. Speed
Slow
Increasing chance of radiation
Alpha particles are ……..nuclei
Helium nuclei
How many protons and neutrons does Apha particles, helium nuclei have
Two protons
Two neutrons
What kind of charge do Apha particles have
Strong positive charge
Name three factors of Apha particles
Big
Heavy
Slow moving
Apha particles big mass and charge make them
Strongly ionising
Remove electrons from lots of atoms, creating lots of ions
Don’t penetrate far into materials, stopped quickly
Beta particles are……
Electrons emitted from nucleus
Beta particles move…….
And are quite…….
Fast
Small (electrons)
Beta particles are……..charges
Negatively
Are electrons
Deceive the ionising and penetrating properties of beta particles
Moderately ionising
Penetrate moderately far into materials before being stopped
For every beta particle emitted
A neutron turns into a proton in the nucleus
Gamma rays are a type of
Electromagnetic radiation
Gamma rays are opposite to
Gamma particles
Name properties of gamma rays
Weakly ionising and can penetrate a long way into materials before interacting with an atom
What are alpha particles blocked by
Paper and cardboard
What are beta particles blocked by
Aluminium
What are gamma rays blocked by
Thick lead
Nuclear fission is
A type of nuclear reaction that is used to release energy from uranium(or plutonium atoms.
E.g nuclear reactor
Huge amounts of energy released using chain reaction
Describe how an atom becomes unstable and splits up
Slow-moving neutron is fired at an isotope of uranium (-235)
Neutron is absorbed by nucleus causing atom to become unstable and split
When uranium -235 splits what does it form
Two new lighter elements (‘daughter nuclei’)
Thermal (heat) energy is released
Why is a neutron absorbed by the nucleus
Because it has no charge
(Not repelled by opposite charge of nucleus
Name two nuclei that uranium-235 split into
Krypton-91
Barium-143
Why are the new nuclei of uranium-235 radioactive
They have the ‘wrong’ number of neutrons in them
How is the chain reaction repeated
When uranium splits up it produces two or three new neutrons which hit another uranium nuclei causing them to split up.
And so on…
What are nuclear power stations powered by
Nuclear reactors where a controlled chain reaction takes place splitting up uranium
Heat energy produced form nuclear fission is used to boil water to drive steam turbine, which turns a generator to generate electrical energy.
Chain reactions must be
Carefully controlled
The neutrons released by fission reactions in nuclear reactors have
Lots of energy
When will these released neutrons cause another nuclear fission
Is they are moving slow enough to be captured by the uranium nuclei in fuel rods
What are placed in a generator to slow down fast moving neutrons
Uranium fuel rods
What effect does uranium fuel rods hVe in a moderator
Creates steady rate of nuclear fission
One new neutron produces another fission
What are control rods often made of and what do they do
Boron
Limit rate of fission by absorbing excess neutrons
Where are boron control rods placed
Between fuel rods and raised and lowered into the reactor to control the chain reaction
What happens if the chain reaction in the nuclear reactor is left to continue unchecked
Large amounts of energy released over short time
Many fissions follow each other leading to runway reaction which can cause explosion.
What happens in nuclear fusion and give an example
Two light nuclei collide at high speed and join (fuse) to create larger nucleus
E.g hydrogen nuclei fuse to produce helium nuclei
What does fusion give of a lot of and is it more or less than fission
Energy and more than fission
Energy from stars comes from fission so what are trying to be developed
Fusion reactors to make electricity
What it a positive of fusion and why would it be good for making electricity
Doesn’t leave behind much radioactive waste
Plenty of hydrogen to use as fuel
What is a problem with fusion
Only happens at high temp and pressures
Not at low due to electrostatic repulsion of protons
What are the problems of making fusion reactors
Hard to create right conditions for fusion
No material withstands heat and pressure (just vaporise)
Therefor hard no expensive to build
What does hydrogen need to be stored in for fusion reactors
Magnetic field instead of physical container
Why are the few experimental fusion reactors not generating electricity
It takes more electricity to get up to the temperature then the reactor can produce
What is a theory that hasn’t been accepted yet
‘Cold fusion’
Nuclear fusion with accrues at room temperature rather than millions of degrees C
What would be advantages of cold fusion
Generate lots of electricity, easily and cheaply
What two scientists believed they had discovered cold fusion
Stanley Pons
Martin Fleischmann
