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Why can't ordinary uranium be used in reactors coooled by ordinary water?
Wiki User
∙ 13y ago
Because the neutron economics are against it, a critical reactor and a chain reaction would not be possible. Ordinary water absorbs too many neutrons. For natural uranium you must use graphite or heavy water for the moderator.
Wiki User
∙ 13y ago
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What is fuel enrichment?
Natural uranium contains about 0.7 percent of uranium 235 which is fissile, the rest is uranium 238 which is not. Reactors that use graphite or heavy water moderators can operate with natural uranium, but light water reactors cannot because the water absorbs too many neutrons. Therefore the fuel for this type of reactor has to be enriched, which means the U 235 is increased to about 4 percent. This is done using the gaseous uranium hexafluoride, either by gaseous diffusion or by centrifuging which is the modern way to do it and uses much less power than diffusion.
Why is it necessary to enrich the uranium before manufacturing the fuel pellets?
Natural uranium is only 0.72% fissile uranium-235 isotope. This is only fissionable when using heavy water as the moderator to slow the fission neutrons. With any other moderator you need 3% to 5% uranium-235 isotope. For unmoderated fast neutron reactors like breeders you need 20% to 95% uranium-235 isotope.
What is the most common coolant used in nuclear reactors?
The most common coolant used in nuclear reactors is water. There are light water reactors (using "regular" water), and the heavy water kind of reactor.
Is light water reactors considered as safer than graphite moderated power reactors?
Yes Light water reactors avoid graphite problems and are having more negative temperature coefficient of reactivity.
What Nuclear material is used in nuclear power plant?
The reactor is usually initially fueled with uranium (for water moderated reactors this is enriched to 3% uranium-235, but other designs may be enriched more or less than that). A few reactors (e.g. reactors in France) are initially fueled with plutonium or a mixture of both uranium and plutonium.After a reactor has operated for a period of time significant levels of transuranic elements have built up in the reactor core, these will also fission and the reactor uses them also as fuel (but unless it is a fast breeder reactor it neither produces nor burns these transuranic fuels very efficiently.Note: a fast breeder reactor contains no moderator to slow neutrons and therefor if fueled with uranium usually requires it to be enriched to 93.5% uranium-235, commonly referred to as weapons grade uranium). The advantage of a fast breeder is that it efficiently converts the normally unusable uranium-238 to plutonium and other transuranics. The plutonium it produces would have far too much plutonium-240 and plutonium-241 in it (due to long fuel burn cycles) for use in weapons and could be used to fuel nuclear reactors of other types. It is also able to efficiently burn all the transuranics it produces, meaning the waste it produces would contain little more than the fission products which all have short halflives; therefor this waste would only have to be stored a few hundred years (not the tens of thousands of years that the wastes of current reactors must be stored, because they still contain unburned plutonium and other transuranics).
What are the advantages of enriched uranium?
It could be used with light water reactors.
What is nuclear fuel reactor?
In light water reactors it is uranium dioxide with the uranium enriched to 4-5 percent
How heavy water is used to make plutonium from uranium?
Heavy water is used in nuclear reactors as moderator for neutrons.
What are the moderator used in a nuclear reactor with natural uranium?
The moderator used in nuclear reactors with natural uranium is generally the heavy water (D2O).
Does a critical mass of uranium require enriched uranium?
No. Heavy Water moderated reactors like the CANDU type can go critical and run on natural (0.72%) Uranium just fine.
The uranium rich fuel rods are surrounded by which molecule?
In water reactors the fuel rods are clad with zircaloy sheaths
What has the author Robert Civiak written?
Robert Civiak has written: 'Nuclear fusion power' -- subject(s): Nuclear energy, Nuclear fusion 'Breeder reactors' -- subject(s): Breeder reactors, Nuclear industry, Nuclear reactors 'Improved uranium utilization in once-through light water reactors' -- subject(s): Light water reactors, Technological innovations, Uranium as fuel 'Plutonium economics and Japan's nuclear fuel cycle policies' -- subject(s): Nuclear fuels, Plutonium, Reactor fuel reprocessing 'Economics of plutonium use in light water reactors' -- subject(s): Costs, Economic aspects of Plutonium as fuel, Economic aspects of Uranium as fuel, Light water reactors, Nuclear fuels, Plutonium as fuel, Reactor fuel reprocessing, Uranium as fuel 'Uranium enrichment' -- subject(s): Economic aspects of Nuclear energy, Nuclear energy, Uranium enrichment 'Nuclear power' -- subject(s): Nuclear energy, Technological innovations 'Magnetohydrodynamic (MHD) power generation' -- subject(s): Electric power production, Magnetohydrodynamic generation, Magnetohydrodynamics
What is a light water reactor?
The nuclear fission reactors used in the United States for electric power production are classified as "light water reactors" in contrast to the "Heavy Water Reactors" used in Canada. Light water (ordinary water) is used as the moderator in U.S. reactors as well as the cooling agent and the means by which heat is removed to produce steam for turning the turbines of the electric generators.
What is fuel enrichment - nuclear?
Natural uranium contains approx 0.7 percent U235, the rest U238. The 235 is the useful fissile isotope. Some reactors using graphite or heavy water can use natural uranium, but light water reactors need to have the U235 proportion increased to about 4 percent. this is called enrichment.
How nuclear energy is used today?
Mostly in reactors fuelled by Uranium and moderated and cooled by light water (PWR and BWR types)
What is fuel enrichment?
Natural uranium contains about 0.7 percent of uranium 235 which is fissile, the rest is uranium 238 which is not. Reactors that use graphite or heavy water moderators can operate with natural uranium, but light water reactors cannot because the water absorbs too many neutrons. Therefore the fuel for this type of reactor has to be enriched, which means the U 235 is increased to about 4 percent. This is done using the gaseous uranium hexafluoride, either by gaseous diffusion or by centrifuging which is the modern way to do it and uses much less power than diffusion.
Why can ordinary uranium not be used to fuel a reactor cooled by ordinary water?
Because "ordinary" uranium is mostly 238U, which won't fission and create a chain like its lighter cousin 235U will. When critical mass is achieved with the 235U isotope of uranium, fission will occur spontaneously. Or with a significantly enriched uranium fuel (one where the natural concentration of 235U has been increased a bunch so the fuel has a much higher percentage of this isotope), fission and a chain reaction is also possible. But with just natural uranium, a big pile of it will just sit there. It won't fission and create a chain reaction. Note that 238U is radioactive and decays over time because it is unstable, but it has a long half-life. Also, the fact that it's unstable (radioactive) doesn't mean it's fissile. It isn't.
