MODULE 8 IQ 4 Flashcards
radioactive decay definition
natural spontaneous reaction where an unstable nucleus of an atom attempts to become more stable by undergoing a nuclear configuration change
alpha decay
excess energy is released in the form of KE in the products
- alpha particle is Helium-4 nucleus
- alpha decay will cause nuclear transmutation –> change composition of nucleus
beta minus decay
- neutron inside nucleus is converted into a proton –> ejection of electron
- accompanied by electron antineutrinos
beta plus decay
emits a positron (antiparticle of an electron) accompanied by a neutrino
gamma decay
- not nuclear transmutation
- release of gamma rays in order to allow daughter nuclides to reach lower energy states
the nucleus
- nucleus is a highly dense, concentrated, positive sphere –> nucleus would explode due to electrostatic repulsion (Coulomb’s law)
strong nuclear force (SNF)
neutrons within nucleus provide SNF as proton number increases
zone of stability
neutron to proton ratio determines the stability of the nucleus
SNF properties
- short-range force: attractive, however at extremely small distances it also becomes repulsive
- mediated by gluons
- acts on nucleus regardless of the charge
in neutron to proton ratio, when there are more protons…?
electrostatic repulsion > strong force
in neutron to proton ratio, when there are more neutrons…?
repulsive strong nuclear force
what is a half-life of an isotope
time taken for half of the amount to decay into a daughter nuclide
independent to:
- external factors
- only affected by nuclear interactions involving collisions with the nuclei themselves
what is binding energy
the energy input to separate the nucleus into its constituent particles
energy + nucleus –> nucleons
m(nucleus) < m(nucleons)
what is mass defect
difference in mass between the nucleus and the nucleons
Binding energy = ∆mc^2
∆m = mass defect
stability of the nucleus
- increase of binding energy allows for more stability
using Fe-56 to compare stability of the nucleus
fission:
- before Fe-56: exothermic –> spontaneous
- after Fe-56: endothermic –> non-spontaneous
fusion:
- towards Fe-56: exothermic
- past Fe-56: endothermic
mass difference equation
∆m = m(reactants) - m(products)
nuclear fission definition + important example
- any nuclear transmutation process where larger nuclei split up into lighter, smaller daughter nuclei
235 1 131 92 1
92 U + 0 n –> 56 Ba + 36 Kr + 3 0 n
critical mass
not all of the neutrons produced in fission reactions induce further fission as they can easily be lost to the environment
controlled chain reactions
for every 2 or 3 neutrons released, only 1 must be allowed to strike another uranium nucleus
uncontrolled chain reactions
more than one further fission reaction is induced by neutrons emitted from fission
nuclear power plant components
fuel rods, moderator, control rods
fuel rods function
contain U-235, packaged in zirconium tubes
moderator function
slows down neutrons to thermal speed to produce thermal neutrons, increasing percentage of fission, increasing efficiency
- slow neutrons are more likely to interact with the nucleus –> increases matter wavelength, increasing likeliness of interaction
control rods function
keep the reaction controlled
- absorb excess neutrons
- generally made of Boron or Cadmium
- operated using gravity not electricity
nuclear fusion definition
when 2 or more smaller nuclei combine to form a larger nuclei (occurs in stars)
why is nuclear fusion not feasible as an energy source
the cost associated with producing the necessary conditions outweighs the amount of energy produce
