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
Risks and benefits of Nuclear Power
Benefits: There is enough fuel to keep generating energy for centuries
Doesn’t release much greenhouse gas
Very efficient, generates thousands of times more energy per kg than fossil fuels
Energy can be generated constantly unlike other renewables
Risks: Have to be designed and built extremely carefully to avoid the risk of a nuclear disaster.
Waste disposal and making sure it doesn’t endanger people and the environment
