Nuclear Fusion

Engager: Complete the worksheet provided 1. A nuclear fuel such as ____________ releases large amounts of energy when it nuclei ___________. In nuclear ________, neutrons are fired at the __________, causing some of its _________ to split into two smaller nuclei, roughly _______ in size. The split also releases two or three more ________. Match up the two halves of these statements: Use the diagram, to describe fully the stages of a fission reaction in a nuclear reactor. Why does lowering the control rods reduce the amount of energy released each second from the nuclear fuel? Chain reactions have to be controlled. This means limiting the number of neutrons causing fission. Explain what could happen if a chain reaction is uncontrolled. Control rods are used to… …are used to carry away the heat. Coolants such as water and CO2… …nucleus releasing more neutrons. In nuclear reactors… …controlled to prevent overheating. A neutron splits a uranium… … to split more nuclei, releasing more neutrons. The neutrons released go on… …absorb some neutrons. The chain reaction has to be… …a chain reaction is set up.

A (uranium/plutonium) nucleus absorbs a neutron (do not accept neutron fired/hits) into uranium/plutonium the nucleus split energy is released further neutrons are released. Neutrons are absorbed by the control rods, there are fewer neutrons. Chain reaction slows down as a result. Each fission decay releases energy so an uncontrolled reaction would release lots of energy, which could lead to reactor meltdown/an explosion. Self Marking 1. Nuclear fuel such as uranium releases large amounts of energy when it nuclei split. In nuclear reactor, neutrons are fired at the uranium, causing some of its nuclei to split into two smaller nuclei, roughly equal in size. The split also releases two or three more neutrons. Control rods are used to… …absorb some neutrons. Coolants such as water and CO2… …are used to carry away the heat. In nuclear reactors… …a chain reaction is set up. A neutron splits a uranium… …nucleus releasing more neutrons. The neutrons released go on… … to split more nuclei, releasing more neutrons. The chain reaction has to be… …controlled to prevent overheating.

To understand what Nuclear Fusion is Progress To distinguish the difference between Fission and Fusion To justify the advantages and disadvantages of Nuclear Fusion. To explain what happens in a nuclear fusion.

To demonstrate good progress in this lesson Name Will… To distinguish the difference between Fission and Fusion. To justify the advantages and disadvantages of Nuclear Fusion. To explain what happens in a nuclear fusion. The Honley Learning Mindset Advocate for this lesson is… Matthew – will show resilience by not giving up if he finds something difficult.

Can anyone define Nuclear Fission? Nuclear fission is the splitting of large and unstable nucleus, by absorbing a slow moving neutron. Nuclear Fusion? In nuclear fusion, two light nuclei collide at high speeds and join (fuse) to create a larger, heavier nucleus. Nuclear fusion two nuclei are pushed together hard enough that the nuclei fuse to form a heavier element. During this process, a vast amount of energy is released. Nuclear fission only works with heavier elements, where as nuclear fusion works with lighter elements, most commonly hydrogen.

We can model a fusion reaction using symbol equations: When forming a symbol equation using the same rules as forming a decay equation.

Connector Conditions for Nuclear Fusion. Nuclear fusion in stars is the only place currently that fusion is possible for a sustained period of time it takes a large amount of energy to fuse nuclei together. In the centre of a star the temperatures are very high and the high gravitational force of the star means that the nuclei travel at very high speeds and collide with high energy. The combination of high temperature and high pressure in stars enables the nuclear fusion process to occur, and it is the heat released during fusion which keeps the reaction going.

Problems with fusion Watch the video and explain why would we want to harness fusion on Earth and what are some of the problems with nuclear fusion on Earth.

Task on Nuclear Fusion You have 15 minutes You are to use your notes and the worksheets that are spread around the room to write arguments for and against the development of Nuclear Fusion. Your arguments must be based on scientific fact. You have 15 minutes

Securing activity – complete the GCSE Question use your notes if needed

Self Marking Up to 5 marks for any of the following points: In nuclear fusion, two light nuclei collide at high speeds and join (fuse) to create a larger, heavier nucleus. Nuclear fusion two nuclei are pushed together hard enough that the nuclei fuse to form a heavier element. Some of the mass of the small nuclei is converted to energy. This energy is then released as radiation. Advantages: Fusion fuel readily available. No waste products. Fusion stops if plasma out of control. Disadvantages: Large amounts of energy needed to start fusion. Plasma difficult to control. Currently fission produces more energy than fusion. Additional mark for correct spelling and grammar. Keywords: Fusion, Joining, Light Nuclei, Temperature, Pressure

Worksheets to print

Worksheet on Nuclear Fusion Problems with fusion If nuclear reactors could be built on Earth, they would supply huge amounts of energy with tiny amounts of fuel. The hydrogen fuel can be made from seawater and the waste product is helium which is harmless. However, there many technical problems with fusion on Earth. To get fusion to work, the hydrogen must be heated to roughly 100 million degrees Celsius. Hotter than temperatures in the core of the Sun. As there is less pressure on Earth a higher temperature is required. It has been achieved experimentally, however these reactors produced less energy than was needed to get the fusion started. The costs of these nuclear fusion reactors is extremely high. Another problem is that there is no materials that can withstand the temperatures required for nuclear fusion. One solution is using strong magnetic fields to contain the reactor, such as in a tokomak reactor.

Flame, Plasma Ball, Ball Lightning PLASMAS: Flame, Plasma Ball, Ball Lightning The main problems are: How can the plasma be heated to such extreme temperatures? What can it be kept in? Any physical container would simply vaporise. Consider: The plasma is a gas. Its particles need to be supplied with more kinetic energy to raise the temperature. The plasma is a gas made of IONS, which will make an electric current when they move. Electric currents can be deflected by magnetism.

HEATING THE PLASMA The plasma can be heated: By the electric current that flows when a magnetic field is applied to the ions By beaming in microwaves By injecting extra hydrogen atoms with high kinetic energy

MAGNETIC PLASMA CONFINEMENT In a star, the plasma is confined by GRAVITY. In a fusion reactor, the plasma is confined using MAGNETIC FIELDS The + ions and electrons in the plasma move in spirals around the magnetic field lines

Very powerful magnetic fields are used to confine the plasma into a TOROID (doughnut) shape. This allows it to be heated to the 150 million °C needed without touching the chamber walls

Laser Ignition Fusion “Inertial Confinement” Researchers in the US are trialling a different system using small pellets of hydrogen fuel in lithium cases. Intensely powerful LASERS are focussed on the pellets, starting a fusion reaction. These are in effect tiny nuclear fusion bombs. A continuous series of pellets would be detonated, with the heat produced being used to produce electricity

Energy and Fuel Supply Issues Fusion power stations could provide the very large amounts of continuous energy without producing any greenhouse gases The fuel supply is almost inexhaustible: deuterium is extracted from seawater tritium is made in the reactor from lithium which is very common in the Earth’s crust H 1 3 H 1 2 The lithium from one laptop battery, combined with the deuterium in 100 litres of water, can cover the electricity use of an average European citizen for 30 years.

Radiation and Safety Deuterium (2H) and 4He are stable Whilst tritium is radioactive, it only emits low energy beta particles with a short half life (12 yr). The reaction emits neutrons which are absorbed by the reactor vessel walls, making them weakly radioactive. By choosing suitable metals for the reactor walls, the half lives of the radioactive isotopes produced by the neutrons are around 10 years, so there is no long term waste issue as there is for fission.

Radiation and Safety The mass of fuel in the reactor is no more than a few grams at a time. If the fusion process is disrupted by for example: cutting the fuel supply interrupting the heating mechanisms damage to the reactor walls …the reaction stops immediately