P7 - radiation Flashcards
What is mass number (nucleon number)
The number of protons + the number of neutrons in the nucleus
What is atomic number (proton number)
Number of protons
What happens if an electron absorbs a photon of light
It becomes exited and moves up an electron shell
What happens when an electron moves down an orbital
It releases energy as a photon of light (different wavelength depending on distance between orbitals, therefore different colours)
What is an unstable nuclei
A nucleus that decays randomly and gives out ionising radiation
What does ionising radiation do
Causes atoms to gain or lose electrons and become ions
What is radioactivity measured in
Becquerels (1Bq = 1 count per second)
What are the properties of an alpha particle
4/2 He, helium nucleus, very ionising, low penetration, a few cm range in air, stopped by skin/paper
What are the properties of a beta particle
0/-1 e-, fast moving electron, medium ionisation and penetration, a metre range in air, stopped by aluminium
What are the properties of gamma radiation
Wave, not very ionising, high penetration, almost infinite range in air, stopped by lead/concrete
What is the difference between irradiation and contamination
Irradiated means exposed to ionising radiation, Contaminated means the presence of materials containing radioactive atoms
What is the alpha decay formula
A/Z X atom, —> A-4/Z-2 Y atom + 4/2 He helium nucleus
What is beta decay
When a neutron changes into a proton and an electron
What is alpha decay
When an atom decays into a more stable atom and releases a helium nucleus
What is the beta decay formula
A/Z X atom —> A/Z+1 Y atom + 0/-1 e- electron
What is background radiation
Where naturally, everything releases small amount of radiation
What is half life of a substance
The average time for the count rate (any therefore number of unstable nuclei) to fall by half
What is a radioactive tracer
A radioactive element that traces the flow of a substance through an organ (gamma)
What is nuclear fission
A type of nuclear reaction that releases energy from large, unstable atoms (uranium/plutonium) by splitting them into smaller atoms. The energy comes from the bonds.
Formula for half life
Amount of unstable nuclei after n half lives = 1/2^n x initial amount
What happens in a nuclear reactor (fission)
controlled nuclear fission - neutrons cause chain reaction, energy is used to heat water and turn turbines
What safety measures are there in a nuclear reactor
Concrete shielding prevents radiation escaping
Graphite moderator slows down neutrons so they don’t cause a reaction
Boron control rods absorb neutrons and can be half or fully lowered
What is nuclear fusion
Where two nuclei (tritium and deuterium) are fused together to create a heavier element. the energy comes from converting matter into energy.
What conditions are needed to start and maintain a fusion reaction
heated to 150 million degrees so that the nuclei are traveling fast enough to overcome the electrostatic repulsion of the H+ ions, and a magnetic field to repel and contain the hot plasma
