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Because some of the fission products are neutron poisonsthat as they build up reduce the reactivity. Without the excess reactivity available to overcome this the reactor would shut itself down until the neutron poisons decayed away. This effect was observed in the first production reactor at Hanford (B reactor) when it was first started.
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MaxineExcess reactivity is designed into nuclear reactors to allow for control over the reactor's power level and to ensure safety margins are maintained. It provides flexibility to adjust power output and respond to changes in operating conditions, such as changes in fuel burnup or reactor configuration. Having excess reactivity also enables operators to compensate for uncertainties in reactor behavior.
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What chemical reactions are involved in a nuclear reactor?
In a nuclear reactor, the main chemical reactions involve nuclear fission, whereby heavy atomic nuclei such as uranium-235 split into smaller nuclei, releasing energy and neutrons. These neutrons go on to induce further fission reactions in a chain reaction, creating a sustained release of energy. Control rods are used to regulate the reaction by absorbing excess neutrons to maintain a steady power output.
How many fuel channels does an advanced gas-cooled reactor have?
I don't believe that the design is fixed at this time. General Atomics and others have been working on designs and one has been built in South Africa, but the companies are still working out the final design. A link is provided to an interesting read on the latest evelopments. The advanced gas-cooled reactors, at least the ones I know, have been built in the UK but not elsewhere. The last ones built were at Heysham Stage 2 and Torness, in Scotland. As far as I can remember the number of channels was 332. I think the first answer may have been on the pebble bed reactor, which is gas cooled and advanced, but not the same as the AGR in UK.
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 is ITER?
Wikipedia, the free encyclopedia says, "In computer science, an iterator is an object which allows a programmer to traverse through all the elements of a collection, regardless of its specific implementation. An iterator is sometimes called a cursor, especially within the context of a database."Source: http://en.wikipedia.org/wiki/Iterator
Where was the cobalt bomb made?
The cobalt bomb is a theoretical type of nuclear weapon designed to produce massive amounts of radioactive cobalt-60. It has not been built or tested because of the extreme consequences it would have on the environment.
