Nuclear Flashcards
In Rutherford scattering experiment, what does the fact that most alpha particles pass straight through the foil or are scattered slightly conclude to?
The atom must be mostly empty space, with a small nucleus
In Rutherford scattering experiment, what does the fact that some alpha particles are deflected by very large angles (>90 degrees) conclude to?
Most of the mass must be in the nucleus, and the nucleus must have a large positive charge
State 3 disadvantages of the closest approach method
- alpha particle measurements are disturbed by nuclear recoil
- alpha particle measurements are disturbed by the SNF when coming close to the nucleus, where as electrons are not effected by the SNF
- alpha particles are scattered only by the protons and not all the nucleons that make up the nucleus
State 1 disadvantage of the electron diffraction method
The first minimum of the diffraction pattern is often difficult to determine as it supposes on other scattering events
What is the value of R0, and what does it represent?
Approx 1.4 x10^-15 m, and its the radius of a hydrogen nucleus
What are the constituents of the 4 types of radiation?
Alpha: 2 protons, 2 neutrons
Beta -: electron
Beta +: positron
Gamma: higher frequency EM wave
What is the penetrating power of the 4 types of radiation?
Alpha: low
Beta: medium
Gamma: high
What is the range in air for the 4 types of radiation?
Alpha: approx 5cm
Beta -: 1-2m
Beta +: annihilates almost instantly
Gamma: infinite
State 3 sources of background radiation
- cosmic rays
-nuclear waste
-X-rays
What is meant by the random nature of radioactive decay?
You cannot predict when a particular nucleus will decay
Define the decay constant
The probability of a nucleus decaying per second
Define activity
The number of unstable nuclei decaying per second
State 3 limitations of carbon dating
- for man made objects, you can only find the age of the material not the object
- objects may have been contaminated by other radioactive sources
- there is uncertainty of the ratio of carbon-14 to carbon-12 thousands of years ago
Define the atomic mass unit
1u = 1/12 the mass of an atom of carbon-12
Define mass defect
The difference between the mass of a nucleus and its constituents
Define binding energy
The amount of energy required to separate a nucleus into its separate nucleons
What is nuclear fission?
When a nucleus splits into 2 smaller daughter nuclei, releasing energy and several fast moving neutrons in the process
What is nuclear fusion?
When 2 smaller nuclei join to make a larger one, releasing energy in the process
Why is nuclear fusion so hard to achieve?
Electrostatic repulsion between 2 nuclei must be over come
What is the function of fuel rods and what isotopes do they contain and in what proportion?
They contain the fuel required for fusion, and they consist of approx 5% of U-235 and 95% of U-238
What is the function of the moderator, and what is it made from?
Slows down the neutrons via elastic collisions, its made from water or graphite usually
What is the function of control rods, and what are they made from?
Absorbs neutrons to keep the rate of reaction steady, usually made from boron
What is the function of the coolant, and what is made from?
Removes the heat produced by fission and then produces steam which drives turbines, usually water
What is the function of the shielding, and what is it made from?
The concrete casing around a reactor core, reduces the intensity of the radiation from neutron and gamma emission in particular
What is the most dangerous part of neuclear waste and why?
Used fuel rods, they emit beta and gamma radiation
