Radioactivity Flashcards
Spontaneous
The decay cannot be induced and occurs without external influence
Random nature of decay
Cannot be predicted which nuclei will decay and when
Activity
The number of decays per unit time
Decay constant
The probability that a decay will occur
Isotopes
Nuclei with the same proton number but different nucleon numbers
What occurs during beta minus decay
A neutron turns into a proton meaning a down quark changes to an up quark
An electron and antineutrino are given off
Binding energy
The minimum energy required to separate all the nucleons in a nucleus
Explain binding energy
Mass if nucleus is less than the mass of nucleons
Difference in mass is mass defect
Energy must be supplied to separate the nucleons
The energy is called binding energy
Explain the energy release in nuclear reactions
The mass decreases
Mass has been converted to energy
The energy released ise=mc^2
Explain induced nuclear fission
A slow moving neutron is absorbed by a nucleus
The nucleus splits into two smaller nuclei and fast protons
Energy is releases at kinetic
Nuclear chain reaction
Neutrons are produced by each fission of a uranium nucleus
Neutrons are absorbed by other uranium nuclei
Causing further fission reactions
Compare fissions reactions and radioactive decay
Similarities
Both give off radiation
Both release energy and lose mass
Differences
In fission two fragments of similar sizes are made
In fission neutrons cause chain reactions
Fission can be induced radioactive decay is spontaneous
How do fission power stations work?
Fission reactor generate energy from kinetic energy of fragments
Nuclei collide transferring kinetic to thermal energy
Temperature of uranium increases
Coolant carries thermal energy away from the reactor core
That energy heat water to steam
Steam drives turbines which are linked to generators
Fuel rods
Contain uranium nuclei for reactions
What are moderators and what do they do
Graphite or water
Slow down the fast moving neutrons because slow moving neutrons have more chance of causing fission
Neutrons collide with nuclei of the moderator
Causing a transfer of kinetic energy
What are control rods
Made from boron to absorb neutrons so one neutrons survives between successive collisons
Environmental effects of nuclear waste
Nuclear waste includes the daughter nuclei and last for a long time
Cause ionisation and mutation of DNA in living things
What is nuclear fusion
The joining together of light nuclei to make heavier nuclei
Mass decreases in the reaction
The lost mass is transformed to energy
Kinetic energy is given off and sometimes gamma rays
What are the conditions for nuclear fusion
Positively charge nuclei repel so they need to be close to eachother for the strong nuclear force to take affect
High kinetic energy is needed for this to occur so high temperatures are needed
Nuclear fusion in stars
Very high temperatures mean that nuclei have lots of kinetic energy
High pressure and density mean there are very frequent collisons
Hydrogen nuclei form helium nuclei
How do fusion reactions occur at low temperatures
Nuclei have a range of kinetic energies
Some have a higher energy than the average
Radioactive decay is
Spontaneous and random
