Nuclear - 27 Flashcards
What type of radioactive element is used in nuclear reactors?
Uranium 235
What type of uranium is naturally found?
Uranium 238
What type of Uranium has a higher percentage of Uranium 235?
Enriched Uranium
describe the process of nuclear fission
Neutrons fired at uranium nuclei and then they split performing fission
What is used to control nuclear fission in reactors?
Control rods, absorbing extra neutrons
What are control rods made from?
Boron
What does the moderator do in nuclear reactors?
slows neutrons, by removing energy
What is the moderator made from?
Deuterium often found in water/ graphite
What is the problem with using water as a moderator?
Absorbs neutrons
What is the mass defect?
the difference in mass
How do you calculate binding energy in watts?
mass defect x c^2
1u is equivalent to how much MEV?
931.5 MEV
1 MEV is how many joules
1.6x10^-13
What type of radiation is released from the moderator in a nuclear fission reactor?
gamma radiation/em radiation
Why is uranium 235 better than 238?
238 is hard to fission, so more likely for 235
Why are there multiple fuel rods in a reactor?
so that they can be replaced in stages and so the neutrons released can go though a moderator before contacting another fuel rod as unlikely to contact same fuel rod
what does Lambda represent in nuclear physics?
decay constant
why do the surroundings of a fission reactor become radioactive?
they absorb too many neutrons and so become unstable isotopes
What does N mean in nuclear physics?
Number of nuclei/ mass number
Why must the ke of a neutron be reduced in a thermal reactor?
to increase its chance of fission, when colliding with another uranium atom.
Why is it better for the moderator to have a higher nucleon number?
it will have a higher mass and so will absorb a higher amount of ke
How do you calculate the binding energy in Mev?
mass defect (u) x 931.3
What are the benefits of using nuclear power?
small amounts of C02, output can easily be changed, doesn’t use fossil fuels.
When is the strong nuclear force greatest?
small distances
What do protons repel each other with?
electromagnetic force
What happens in beta minus decay?
it produces an anti neutrino and an electron 0/-1
What is removed in the process of ionisation?
one or more electron
what measures radiation?
Geiger counter
what does alpha radiation consist of?
two protons and two neutrons 4/2
is alpha radiation deflected by magnetic fields?
yes - not as much as beta
what’s the most ionising radiation?
alpha
what’s the range of alpha radiation?
3-5cm
what does beta radiation consist of?
fast moving electron 0/-1
Is beta radiation deflected by magnetic fields?
yes very
What’s the range of beta radiation?
0.5-3m
what is beta stopped by?
Aluminum
What is gamma radiation?
high frequency EM wave - photon
How ionising is gamma radiation?
low
What’s the range of gamma radiation?
indefinite in air
What is background radiation?
radiation that we are always exposed to
what are the main contributors to background radiation?
Radon and Thornon gas, buildings, cosmic rays
How will gamma radiation spread out?
Inverse square law
What are some hazards of radiation?
ionising cells causing cancer
How must radioactive substances be stored?
in a lead lined box, no direct touching
describe the motion of decay
randomly and spontaneously
What does radioactive material decay into?
it will decay into something more stable
what is coolant
A substance that passes through nuclear reactors and is responsible for removing heat from the core. This heat is then used to generate energy.
what is critical mass
The smallest mass of fissile material required in a fission reactor for a chain reaction to be sustained.
what is electron capture
A process that occurs in proton-heavy nuclei, in which an electron is drawn into the nucleus, causing a proton to transition into a neutron. An electron neutrino is also produced.
what is fusion
The joining of two smaller nuclei to form a larger nucleus and to release energy.
what is fission
The splitting a nucleus, to form two smaller daughter nuclei, neutrons and energy
what is half life
The average time it takes for the number of radioactive nuclei in a sample to halve.
what is the inverse square law
A law that governs the intensity of gamma radiation. It means that the intensity of radiation at any point is inversely proportional to the square of the distance from its source.
what is the mass defect
The difference in mass between a nucleus and the sum of the masses of its constituent nucleons.
what is the closest approach
A method of estimating a nuclear radius by firing a alpha particle at it. It involves calculating the distance at which all the alpha particle’s kinetic energy is converted to electric potential energy
why might there be more radioactivity than the sources itself?
the products may also decay and be radioactive.
what is meant by decays spontaneously?
decays without the need for a stimulus
