Nuclear (M6) Flashcards
Proton number
The atomic number - the number of protons in an element’s nucleus.
Symbol: Z
Nucleon number
The mass number - the total number of protons and neutrons in a nucleus.
Symbol: A
Isotope
Nuclei of the same element that have the same atomic number (Z) but different nucleon numbers (A).
Different numbers of neutrons.
Hadron
A particle or antiparticle that is affected by the strong nuclear force and, if charged, the electromagnetic force.
Eg proton (uud), neutron (udd)
Baryon
Any hadron made with a combination of three quarks eg a proton.
Meson
Any hadron made with a combination of a quark and an anti-quark eg kaon and pion
Fundamental particle
A particle that has no internal structure and hence cannot be split into smaller particles.
Lepton
A fundamental particle or antiparticle that is not affected by the strong nuclear force.
Eg electron or positron
Ionising radiation
Any form of radiation that can ionise an atom by removing an electron to leave a positive ion.
Random decay
Cannot predict when or which nucleus will decay. Each nucleus has the same chance of decaying per unit time.
Spontaneous decay
Unaffected by the presence of other nuclei or external factors such as pressure or temperature.
Annihilation
The complete destruction of a particle and its antiparticle in an interaction that releases energy in the form of identical photons.
Rest mass
The mass of an object such as a particle when it is stationary
Mass defect
The difference between the mass of a nucleus and the mass of its completely separated constituent nucleons.
Binding energy
The minimum energy required to completely separate a nucleus into its constituent protons and neutrons.
Binding energy per nucleon
The binding energy divided by the number of nucleons. The greater the binding energy per nucleon, the more tightly bound the nucleons in the nucleus, therefore the more stable the atom.
Binding energy curve
Increases rapidly, Iron 56 at peak then decreases slowly.
Fusion on left
Fission on right
Induced fission
Nuclear fission occurring when a nucleus becomes unstable on absorbing another particle
U-235 + n = U-236 = Ba-141 + Kr-92 + 3n
Fusion
A process in which two smaller nuclei join together to form one larger nucleus.
Chain reaction
A reaction in which the neutrons from an earlier fission stage are responsible for further fission reactions leading to an exponential growth in the rate of the reactions.
Components of a fission reactor
Fuel rods: contain enriched uranium (2-3% U-235, the rest U-238)
Moderator: slows the fast neutrons - normally water which is also used as a coolant
Control rods: material absorbs neutrons so exactly one survives per reaction
Carbon dating
A method for determining the Age of organic material by comparing the activities or ratios of carbon-14 nuclei of the dead material of interest and similar living material.
Exponential decay equation
N = N⁰ e^-lt
l = decay constant
When t = its half life: N = N⁰/2
Half life
The average time it takes for half the number of active nuclei in a sample of an isotope to decay.
Activity
The rate at which nuclei decay or disintegrate in a radioactive source.
Unit: Becquerels (Bq)
Decay constant
The probability of decay of an individual nucleus per unit time.
Strong nuclear force
One of the four fundamental forces in nature, acting on hadrons and holding nuclei together.
Very short range - repulsive below 0.5fm and attractive up to about 3fm
Force carrier: gluon
Weak nuclear force
One of the four fundamental forces.
Responsible for beta decay.
Range of about 10^-18m and 10^-6 X strength of SNF
Force carrier: boson
Alpha radiation properties
Charge: 2e
Range: a few cm
Absorption: thin sheet of paper
Typical speed: 10^6 ms
Mass: 4.00151u
Equation: (A, Z)X -> (A-4, Z-2)Y + (4,2)He
Beta radiation properties
Charge: e or -e
Range: 1m
Absorption: 1-3mm of aluminium
Typical speed: 10^8 ms
Mass: 0.00055u
Plus equation: (A,Z)X -> (A,Z-1)Y + (0,1)e + Ve
Minus equation: (A,Z)X -> (A,Z+1)Y + (0,-1)e + Vē
Gamma radiation properties
Charge: 0
Absorption: a few cm of lead
Typical speed: 3x10^8 ms
Mass: 0
Equation: X -> X + g
Measuring half-life of protactinium
Plastic bottle with solution of uranyl nitrate in water and organic solvent containing protactinium.
First measure background count rate
Shake bottle so protactinium dissolves in organic solvent which floats to the top.
Place GM tube pointing at organic layer (not touching bottle) and measure count rate for 10s every 30s.
Calculate CCR
Plot graph of CCR against time.
