Nuclear Fusion and Fission

C.3.NoS Assessing the ethics of scientific research—widespread use of nuclear fission for energy production would lead to a reduction in greenhouse gas emissions. Nuclear fission is the process taking place in the atomic bomb and nuclear fusion that in the hydrogen bomb. (4.5)

C.3.U1 Light nuclei can undergo fusion reactions as this increases the binding energy per nucleon.

C.3.U2 Fusion reactions are a promising energy source as the fuel is inexpensive and abundant, and no radioactive waste is produced.

C.3.U3 Absorption spectra are used to analyse the composition of stars.

C.3.U4 Heavy nuclei can undergo fission reactions as this increases the binding energy per nucleon.

C.3.U5 \^{235}U undergoes a fission chain reaction: \^{235}_{92}U + \^{1}_{0}n -> \^{236}_{92}U -> X + Y + neutrons

C.3.U6 The critical mass is the mass of fuel needed for the reaction to be self-sustaining.

C.3.U7 239Pu, used as a fuel in “breeder reactors”, is produced from 238U by neutron capture.

C.3.U8 Radioactive waste may contain isotopes with long and short half-lives.

C.3.U9 Half-life is the time it takes for half the number of atoms to decay.

C.3.AS1 Construction of nuclear equations for fusion reactions.

C.3.AS2 Explanation of fusion reactions in terms of binding energy per nucleon.

C.3.AS3 Explanation of the atomic absorption spectra of hydrogen and helium, including the relationships between the lines and electron transitions.

C.3.AS4 Deduction of nuclear equations for fission reactions.

C.3.AS5 Explanation of fission reactions in terms of binding energy per nucleon.

C.3.AS6 Discussion of the storage and disposal of nuclear waste.

C.3.AS7 Solution of radioactive decay problems involving integral numbers of half-lives.

C.3.G1 Students are not expected to recall specific fission reactions.

C.3.G2 The workings of a nuclear power plant are not required.

C.3.G3 Safety and risk issues include: health, problems associated with nuclear waste and core meltdown, and the possibility that nuclear fuels may be used in

C.3.G4 The equations, N = N0 e-\lambda{}t and t_{1/2} = ln 2 / \lambda{} are given in section 1 of the data booklet.

C.3.IM1 The use of nuclear energy is monitored internationally by the International Atomic Energy Agency.

C.3.IM2 High-energy particle physics research involves international collaboration. There are accelerator facilities at CERN, DESY, SLAC, Fermi lab and Brookhaven. Results are disseminated and shared by scientists in many countries.

C.3.IM3 The ITER project is a collaboration between many countries and aims to demonstrate that fusion is an energy source of the future.

C.3.ToK1 The use of nuclear energy carries risks as well as benefits. Who should ultimately be responsible for assessing these? How do we know what is best for society and the individual?

C.3.Aims1 Aim 7: Computer animations and simulations of radioactive decay, and nuclear fusion and fission reactions.

C.3.Aims2 Aim 8: Consideration of the environmental impact of nuclear energy illustrating the implications of using science and technology

C.7.NoS Trends and discrepancies—our understanding of nuclear processes came from both theoretical and experimental advances. Intermolecular forces in UF6 are anomalous and do not follow the normal trends. (3.1)

C.7.U1 The mass defect (∆m) is the difference between the mass of the nucleus and the sum of the masses of its individual nucleons.

C.7.U2 The nuclear binding energy (ΔE) is the energy required to separate a nucleus into protons and neutrons.

C.7.U3 The energy produced in a fission reaction can be calculated from the mass difference between the products and reactants using the Einstein mass-energy equivalence relationship E = mc2.

C.7.U4 The different isotopes of uranium in uranium hexafluoride can be separated, using diffusion or centrifugation causing fuel enrichment.

C.7.U5 The effusion rate of a gas is inversely proportional to the square root of the molar mass (Graham’s Law).

C.7.U6 Radioactive decay is kinetically a first order process with the half-life related to the decay constant by the equation 𝜆𝜆 = ln 2.

C.7.U7 The dangers of nuclear energy are due to the ionizing nature of the radiation it produces which leads to the production of oxygen free radicals such as superoxide (O2-), and hydroxyl (HO·). These free radicals can initiate chain reactions that can damage DNA and enzymes in living cells.

C.7.AS1 Calculation of the mass defect and binding energy of a nucleus

C.7.AS2 Application of the Einstein mass-energy equivalence relationship, E = mc2, to determine the energy produced in a fusion reaction.

C.7.AS3 Application of the Einstein mass–energy equivalence relationship to determine the energy produced in a fission reaction.

C.7.AS4 Discussion of the different properties of UO2 and UF6 in terms of bonding and structure.

C.7.AS5 Solution of problems involving radioactive half-life.

C.7.AS6 Explanation of the relationship between Graham’s law of effusion and the kinetic theory.

C.7.AS7 Solution of problems on the relative rate of effusion using Graham’s law.

C.7.G1 Students are not expected to recall specific fission reactions.

C.7.G2 The workings of a nuclear power plant are not required.

C.7.G3 Safety and risk issues include: health, problems associated with nuclear waste, and the possibility that nuclear fuels may be used in nuclear weapons.

C.7.G4 Graham’s law of effusion is given in the data booklet in section 1.

C.7.G5 Decay relationships are given in the data booklet in section 1.

C.7.G6 A binding energy curve is given in the data booklet in section 36.

C.7.IM1 There are only a very small number of countries that have developed nuclear weapons and the International Atomic Energy Agency strives to limit the spread of this technology. There are disputes about whether some countries are developing nuclear energy for peaceful or non-peaceful purposes.

C.7.IM2 Nuclear incidents have a global effect; the accidents at Three Mile Island and Chernobyl and the problems at Fukushima caused by a tsunami could be discussed to illustrate the potential dangers.

C.7.ToK1 “There is no likelihood that humans will ever tap the power of the atom.” (Robert Millikan, Nobel Laureate Physics 1923 quoted in 1928). How can the impact of new technologies be predicted? How reliable are these predictions? How important are the opinions of experts in the search for knowledge?

C.7.ToK2 The release of energy during fission reactions can be used in times of peace to generate energy, but also can lead to destruction in time of war. Should scientists be held morally responsible for the applications of their discoveries? Is there any area of scientific knowledge the pursuit of which is morally unacceptable?

C.7.Aims1 Aim 7: Computer animations and simulations of radioactive decay, and nuclear fusion and fission reactions.

C.7.Aims2 Aim 8: Consideration of the advantages and disadvantages of nuclear fusion illustrates the economic and environmental implications of using science and technology. The use of fusion reactions in the hydrogen bomb can also be discussed.