Nuclear physics Flashcards
Define the decay constant
The probability that one atom will decay per unit time
What does N represent
N represents the number of radioactive atoms
Define the activity of a sample
The activity of a sample is the number of nuclei that decay per second
What is the decay constant
The probability of the decay of any nucleus per unit time
T1/2 = ln2/λ
What is the radius of the nucleus
1.4 x 10^-15
What does the radius of a nucleus depend on
The radius R of a nucleon number depends on the mass number A.
R = r0A1/3
What is r0
r0 is the constant between the radius of a nucleon and the nucleon number
Density of the nucleus
Radius = R=R0A^1/3 Volume = 4/3piR^3
Density = mass/volume
Define the term atomic mass unit
The atomic mass unit is defined as one twelfth as of the mass of an atom of carbon-12
Binding energy
The energy required to completely separate the nucleus into its individual nucleons
What is the mass defect of a nucleus
The difference between the mass of the separated nucleons and the combined mass of the nucleus
Nuclear fusion
A process where two nuclei join together to form one larger nucleus due to high temp and pressure that can overcome electrostatic forces
What is 1u equivalent to in MeV
1u = 931.3MeV
Radius of a nucleus
R = r0A^1/3
De broglie wavelength
λ = hc/E (E in J)
Electron diffraction first minimum
sinθ = 1.22λ/2R
Activity
A = A0e^-λt
Number of atoms in a sample
N = n x Na
n = no. of mols Na = Avogadro
Alpha particle that rebounds
Initial Ek = E elec = Charge of nucleus x Charge of alpha/ 4πε0r
What is critical mass
The amount of fuel needed for a fission chain reaction to continue at a steady rate on its own
Function of the coolant
Coolant is sent around the reactor to remove heat produced by fission. The coolant needs to be a liquid or gas at room temperature and be efficient at transferring heat. Water is often used
Function of the Moderator
The moderator slows and absorbs neutrons. A moderator needs to slow down some neutrons so they can cause further fission (high velocity neutrons will just bounce off the U nucleus) The moderator slows neutrons down through elastic collisions.
Water is used because it contains hydrogen which has hydrogen (similar mass to a neutron)
Function of the control rods
Limit the number of neutrons in the reactor. They absorb neutrons so that the rate of fission is controlled. Made of a material that absorbs neutrons (Boron)
Function of shielding
A thick concrete case surrounds the reactor to stop the radiation escaping
