Radioactivity Flashcards
What kind of decay if neutron excess
Beta decay
What kind of decay if proton excess
Positron, electron capture
What kind of decay if excess proton and neutron
Alpha or fission
Beta decay equation and range of energies
n -> p+ + e- + anti neutrino
E_mean = 1/3 E_max
Positron decay equation
p+ -> n + e+ + neutrino
Electron capture equation
p+ + e- -> n + neutrino
often results in daughter nuclei in excited or metastable state, emits gamma rays. Characteristic radiation has implications for measurement.
Radionuclide production methods
Charged particle bombardment (cyclotron)
Neutron activation
Fission products (both nuclear reactor)
What are isobars
Nuclides with the same mass number
What are isotones
Nuclides with the same neutron number
What are isomers
Nuclides that are different because one is metastable
What are two forces going on in nucleus
Nuclear force attracts nucleons, electrostatic force repels them –> larger elements need more neutrons to remain stable to overcome electrostatic
Isomeric transformation
Decay of metastable nuclide by emission of gamma ray - good because gives off gamma rays for imaging but no particles for dose
Internal conversion
Alternative to gamma ray emission - transfers energy to orbital electron which is ejected
How does cyclotron work
Accelerates particles in magnetic field towards target. Added protons so decays by positron or electron capture because proton rich.
What happens in nuclear reactor
Undergoing fission - giving off free neutrons which generate further events. Need to control this reaction - control rods absorb neutrons and moderator slows them down
