RadioactiviTEA Flashcards
Nuclear fission/fusion, Energy of nuclear reactions, Binding Energy (per nucleon), Mass defect and their implications
What is mass defect ?
The difference between the actual mass of a nuclide and the masses of its constituent nucleons when taken apart
What mass is always higher
between nuclide mass and total constituent mass?
Total constituent mass
True or False?
The higher the (potential) energy state of a substance, the higher its mass
True
These changes are just so minute in everyday circumstances that they are considered negligible, however, such is not the case in nuclear physics
What is Einstein’s mass-energy equation?
ΔΣ = Δmc2
What is seen as the energy equivalent of the mass defect?
Binding Energy
True or False?
In Nuclear physics there are large changes in energy which result to small changes in mass
False
There are considerable and visible changes in mass due to the large energy changes in Nuclear Physics
What is the rest mass of a particle
The mass of a particle when it is stationary
What is the (unified) atomic mass unit (U)?
The mass of 1/12th the mass of the C-12 isotope
What is the value of 1 (unified) atomic mass unit (U) in kilograms?
1U = 1.66 x 10 -27 kg
What is the value of 1 (unified) atomic mass unit (U) in MeV (mega electron volts)?
1U = 931.5 MeV
What does the mass defect imply?
That energy is released when the nucleons are combined to form the nuclide
This same energy will be released when the nuclide is separated into its nucleons
How does binding energy determine nuclide stability?
The higher the binding energy per nucleon, the more stable the nuclide
What is binding energy?
This is the minimum energy required to split a nuclide into its constituent nucleons
What is binding energy per nucleon?
This is the binding energy of a nuclide divided by the nucleon number
What is the nature of strong nuclear force between nucleons in the nucleus of an atom?
It is attractive and very short-ranged.
What are nucleons?
Particles that make up a nucleus/nuclide
Name the two types of nucleons in a nuclide
Protons and Neutrons
What is there to note about beta (electron, β-) radioactive decay?
The proton number increases when the electron is liberated
What is there to note about beta (positron, β+) radioactive decay?
The proton number decreases when the positron is liberated
What is there to note about alpha (α) radioactive decay?
Nucleon number decreases by 4 and proton number decreases by 2 when the alpha particle is liberated
What is there to note about gamma (γ) radioactive decay?
There is no change in either the nucleon number or the proton number, only energy is released (making the nuclide more stable) when a gamma ray is emitted
What is noticed when attempting to balance masses in a nuclear equation?
There is typically a lesser mass on the right hand side of the equation
What reason can be given for the difference in masses on either side of a nuclear equation?
Energy is released when the reaction occurs
In what form is this energy typically released?
Kinetic energy
What does this kinetic energy typically do when released?
It is supplied to the particles of the system
What is the point of Albert Einstein’s mass-energy equation?
To explain/ try to quantify the mass lost due to large energy changes
Footnote: Objects at different energies always have different masses, with objects at higher energies having higher masses. In real life, the energy changes are too small to be accounted for, but they always occur
In what context is binding energy more adequately defined?
Externally. Binding energy is the minimum external energy needed to separate a nuclide into its constituent nucleons
At what speed should neutrons be to induce fission?
Low speeds
Slow-moving or thermal neutrons are the most effective at inducing fission
What does it mean when a nuclide is described as ‘fissile’?
The nuclide is capable of undergoing nuclear fission
In neutron-induced fission, the neutron’s introduction to the already fissile nuclide makes it more unstable, initiating a fission that’d have otherwise happened at a later date
What is the function of a moderator in a nuclear reactor?
It reduces the speed of the fast-moving neutrons produced
Give an example of two materials that can be used as a moderator in a nuclear reactor?
Carbon (Graphite) rods or Water
What type of materials are moderators made of:
Good or Poor absorbers of neutrons?
Poor absorbers of neutrons
What type of materials are control rods made of:
Good or Poor absorbers of neutrons?
Good absorbers of neutrons
These materials absorb these neutrons without becoming unstable themselves. They are non-fissile materials
What is the function of the control rods in a nuclear reactor?
They absorb (excess) neutrons produced in the nuclear reactor
This helps to regulate the rate of fission
Give an example of two materials that can be used as a control rod in a nuclear reactor?
Boron or Cadmium rods
How can a nuclear reaction be stopped in a nuclear reactor?
By fully lowering down the control rods within the reactor
Give an example of materials that can be used as coolants in a nuclear reactor?
Water, Deuterium Oxide (Heavy water), or Liquid Sodium
Give a reason why water is an effective coolant in a nuclear reactor?
It has a very high specific heat capacity
This makes it capable of transferring very high amounts of thermal energy
What is the decay constant of a radioactive substance?
This is the probability that a radioactive nuclide will decay per unit time
What is the activity of a radioactive substance?
This is the amount of a radioactive substance decaying per unit time
It is the rate of disintegration of a radioactive specimen
Why is radioactive decay spontaneous?
Because one can never determine which nuclide within a radioactive specimen that will decay next
Why is radioactive decay random?
Because it is not affected by physical and chemical factors
Such as temperature, pressure and concentration (the presence of other nuclides around it)
