Nuclear Radiation Flashcards
Define Background Radiation
Low levels of radiation from environmental sources, always present around us.
What are the types of nuclear radiation?
Alpha α, Beta β, Gamma γ
What is the composition of an Alpha particle?
Two protons and two neutrons (same as helium). It has +2e charge so is highly ionising so it loses kinetic energy and is easily absorbed. Blocked by paper.
What is the composition of an Beta particle?
Electron. Blocked by sheet of aluminium.
What is the composition of an Gamma particle?
High energy, high frequency, em radiation. Photons with no charge and no mass, so rarely interact with particles in path - least ionising. Energy can be reduced by several cm of lead.
Define Decay Contant, λ
The probability per second, a given nucleus will decay.
A = -λN
A - Activity
N - Number of nuclei in sample
What does the minus indicate?
A = -λN
Number of nuclei in sample decreases with time.
Define Activity
A = -λN = dN/dt
The number of radioactive decays in unit time
Define Half Life
The time taken for half of the atoms of a nuclide within a sample to decay.
λ = ln 2 / t½
Define Mass defect
The difference between measured mass of a nucleus and sum total of masses of its constituent nucleons.
Define Nuclear Binding Energy
The energy used to hold the nucleus together converted from the mass deficit. E=mc^2
Which isotope has the highest binding energy per nucleon?
Iron-56 at 8.8Mev per nucleon.
What does binding energy per number - mass number graph show?
Small nuclides combine to make larger nuclei up to Fe-56 with a greater binding energy per nucleon - nuclear fusion. Larger nuclei can break up into smaller pieces which have a greater binding energy per nucleon than original nucleus - fission.
Explain process of Nuclear Fusion releasing energy
Small nuclei fuse together to produce a larger nucleus. Mass of fused nucleus is less than total mass of initial nuclei. Binding energy increases so energy is released.
Explain process of Nuclear Fission.
.
Define Radioactive Isotope
Has an unstable nucleus which decays and emits radiation
Radioactive decay is a random process. Explain what this means.
We can’t know when an individual nucleus will decay
We can’t know which nucleus will decay next. Each nucleus has a fixed probability of decay.
Explain the conditions necessary for fusion
High temperature to overcome electrostatic repulsion. High pressure to maintain high collision rate.
Massive stars can only produce elements up to iron (Fe) in their cores by fusion. Explain why.
Iron-56 is the peak of the graph. If nuclei were to be formed nucleon number would be greater than 56, so binding energy per nucleon decrease. This would require net input of energy so does not occur.
Nuclear decay is said to be random and spontaneous. What is meant by spontaneous?
Spontaneous: decay cannot be influenced by any external factors
Nuclear decay is said to be random and spontaneous. What is meant by random?
Random: you cannot identify which nucleus will decay next/ when an individual nucleus will decay
What is meant by ionising radiation?
Ionising radiation removes electrons from atoms/ molecules
State the most stable element and give a reason why.
Iron-56 has the maximum value of binding energy per nucleon
State what is meant by isotopes.
same number of
protons but different numbers of neutrons
State the conditions for fusion and hence explain why it has proved difficult to
maintain a sustainable reaction in a practical fusion reactor.
Very high temperatures, o overcome electrostatic repulsion. Nuclei come close enough to fuse for strong (nuclear) force
to act. Very high densities needed this gives a sufficient
collision rate. Very high temperatures lead to confinement problems
State two advantages fusion power might have over fission power.
Hydrogen fuel for fusion is unlimited whereas fission relies upon uranium a relatively limited resource. Fusion results in few radioactive products, but radioactive
products produced in fission present significant disposal
problems. For a given mass of fuel, the energy released by fusion is
greater than the energy released by fission.
State what red shift means and discuss the conclusions that can be drawn from
the observation that radiation from all distant galaxies is red shifted.
Radiation is received with a stretched wavelength
compared to that emitted. This indicates that distant galaxies are receding. Hence the universe is expanding.
A student measures the
potential difference across the combination with a high resistance voltmeter. Explain
why the resistance of the combination is hardly changed by the addition of the
voltmeter.
Voltmeter is connected in parallel. Voltmeter draws
little/no current. 1/RV is very small.
Nuclear power stations currently use the process of fission to release energy. Outline
the process of fission.
A heavy nucleus absorbs a neutron. The nucleus becomes unstable and splits into two fragments. Neutrons are also emitted which cause a change reaction.
State what is meant by nuclear fission and explain why energy is released during the
fission of a nucleus such as uranium.
Fission is the splitting of a large nucleus into smaller nucleons. The mass of fragments is less than the mass of the original nucleus. E=mc^2: Binding energy per nucleon is greater in fragments than in original nucleus.
Discuss the potential advantages of nuclear fusion, compared with nuclear fission, as
a means of supplying our power demands.
- Hydrogen fuel is virtually unlimited.
- Fission relies upon uranium which is a limited resource.
- Fusion results in no radioactive products. -Radioactive products produced in fission present disposal problems.
- For a given mass of fuel, energy released by fusion is greater than energy released by fission.