Controlled Nuclear reactors

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Physics unit 5 Flashcards on Controlled Nuclear reactors, created by sammy414 on 19/02/2014.
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Flashcards by sammy414, updated more than 1 year ago
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Question Answer
What do Nuclear reactors use rods of? Uranium that are rich in U-235 for fuel and U-238
What type of reaction do fission reactors produce? A chain reaction The fission produces more neutrons which then induce other nuclei to fission
When will neutrons cause a chain reaction? When they are slowed down Allows them to be captured by the uranium nuclei
What are these slowed down neutrons called? Thermal neutrons
What must the U-235 rods be placed in? A moderator such as water to slow down/absorb neutrons
What type of moderator must you use? One which will slow down some neutrons enough so they can cause further fission and keep the reaction going at a steady rate
What happens if you choose a moderator which absorbs more neutrons at a higher temperature? It will decrease the chance of meltdown if the reactor overheats as it will naturally slow down the reaction
What is the critical mass? The amount of fuel to keep the reaction going at a steady rate where one fission follows another
What happens if you have any less then the critical mass (sub-critical mass) ? The reaction will just peter out
What mass of fuel do Nuclear reactors use? A super-critical mass Where several new fission's normally follow each fission
What do Nuclear reactors do to control the rate of fission? Use control rods
How do control rods control the chain reaction? By limiting the number of neutrons in the reactor. These absorb neutrons so that the rate of fission is controlled
What are control rods made up of? A material which absorbs neutrons eg. boron
In an emergency what will the reactor do? Shut down automatically by the release of the control rods into the reactor which will stop the reaction as soon as posssible
What does coolant do? sent around the reactor to remove the heat produced by the fission
What material is the coolant? Often the same water that is being used in the reactor as the moderator
What can the heat from the reactor be used for? To make stream for powering electricity-generating turbines
What is the nuclear reactor surrounded by? A thick concrete case which acts as shielding
What does the shielding do? Prevents radiation escaping and reaching the people who work in the power stations
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