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The neutrons simply collide with graphite atoms and get slowed by impacts. Some get absorbed but not too many, and it is important to have very pure graphite to avoid absorption by other elements in the graphite as impurities.
Wiki User
∙ 14y ago
Wiki User
∙ 12y agographite are very stable so absorption cross section is approximatly zero so ofter sricking neutron with graphite neutrons are scattered and slow down.
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Why is graphite used as a moderator in some nuclear reactors?
It is used as a moderator. Natural uranium will not undergo nuclear fission by itself because neutrons emitted by fissioning U-235 tend to be absorbed by U-238. However, if the neutrons can be slowed down, it turns out that U-238 is less likely to eat them, and enough are available to fission U-235 and keep the reaction going. Graphite has the useful property that it can slow neutrons down without eating them, so if you embed uranium lumps in a graphite matrix with appropriate spacing, the neutrons which get into the graphite will be slowed down, and when they finally hit a lump of uranium they are likely to be taken up by U-235 and cause fission.Any light element with a sufficient distaste for neutrons can be used as a moderator. Heavy water (deuterium oxide) works nicely. Natural water has slightly too high an appetite for neutrons to work well, but if the concentration of U-235 is raised a bit, you can make a reactor with natural water moderator. That is how power reactors work in the USA and most other countries.
Does the cadmium in the control rod slow down a nuclear reaction by absorbing neutrons?
true
Are graphite rods radioactive?
no graphite rod not radioactive but these r absorb radioemission rays that's why people think so because in the nuclear plant graphite rod use as a controling nuclear reaction by absirb the nuclear emission rays .A2. The graphite is used as a Moderator - a material that slows the neutrons down sufficiently that they have a greater chance of collision and thus releasing some of their energy. Which we use as thermal energy.Otherwise, the neutrons would have only a small chance of interacting - they are travelling very fast, and the dimensions of a nuclear pile is only a metre or so in dimension. Having interacted to give up some of their energy, the neutrons then just lose the remainder of their energy in the shielding.
What is the difference between two atoms of carbon having the same number of neutrons?
carbon rod, graphite, diamond.
What causes particles to slow down and contract?
what causes particles to slow down and contract
What is the function of graphite in a nuclear reactor?
It's purpose is to slow down fast neutrons that maybe present in the reactor.
What is the function of graphite in the first atomic reactor?
The graphite acts as a moderator, to slow neutrons down. Most fission reactors work on the basis of slow or thermalised neutrons, though some have been built using fast neutrons. When the neutrons are ejected from the uranium nucleus as it fissions or splits, they come off at high speed, but in order to be captured by another nucleus of U-235 they need to be slowed down. This is simply a physical fact, U-235 captures slow neutrons much more readily than it does fast neutrons. Graphite was used in the first demonstration reactor in 1942 and in subsequent bigger reactors at Hanford Wa. It had to be made specially with very high purity to avoid absorbing too many neutrons. Other moderators used are heavy water, as in CANDU reactors, and light water as in PWR. Light water absorbs more neutrons so the fuel has to be enriched in U-235.
Why is the moderator important in a nuclear reactor?
The moderator is used to slow down the neutrons present in the core of the reactor. Normally the neutrons produced as the nuclear fuel (e.g. uranium) is fissioned are travelling too fast to produce a sustained chain reaction. Some examples of moderators are cadmium, heavy water and graphite.
Why is graphite used in nuclear reactors?
Graphite can be used as a moderator, that is to slow down the fast neutrons produced in fission. Early reactors including Hanford and Windscale used graphite, and in the UK this type of reactor was built extensively for power production. However water reactors such as PWR and BWR have proved cheaper to build and have a longer life, so graphite is now little used, there are a few still running but none being planned or built as far as I know.
Are control rods in nuclear reactors made of graphite?
No, control rods in nuclear reactors are not made of graphite. The control rods have to be able to gather up the neutrons to shut the reactor down, so boron is often selected. Graphite is used in some reactors as a moderator, and a moderator slows down neutrons. The slower neutrons have a greater ability to undergo neutron capture to continue the chain.
Why are graphite rods used in a nuclear pile?
Graphite is a "moderator" that slows down the fast neutrons which are produced during the fission process. Fast neutrons are captured by uranium-238 atoms removing them from the chain reaction process. Slow "thermal" neutrons avoid uranium-238 atoms and easily split uranium-235 atoms, producing 2 to 3 more neutrons that can continue the chain reaction. For a moderator to be effective it must slow neutrons rapidly (before too many can be captured by uranium-238 atoms and thus removed from the chain reaction). The most effective moderators in decreasing order are: heavy water (D2O), graphite (C), light water (H2O).
Are there fast neutrons?
Yes, in fact for a sustainable nuclear chain reaction to work, you have to slow neutrons down.
Why do neutrons slow down if they are neutral?
This is because they have rather small penises.
Is moderation of neutrons always used to slow nuclear fission?
No, moderation of neutrons is not always used to slow nuclear fission. In some types of nuclear reactors, such as fast breeder reactors, fast neutrons are intentionally not moderated to slow down the fission process. These reactors operate using fast neutrons to sustain a chain reaction. However, in most commercial nuclear reactors, moderation of neutrons is employed to slow down the fission process and maintain a controlled chain reaction.
Does the cadmium in the control rod slow down a nuclear reaction by absorbing neutrons?
true
Why is graphite used as a moderator in some nuclear reactors?
It is used as a moderator. Natural uranium will not undergo nuclear fission by itself because neutrons emitted by fissioning U-235 tend to be absorbed by U-238. However, if the neutrons can be slowed down, it turns out that U-238 is less likely to eat them, and enough are available to fission U-235 and keep the reaction going. Graphite has the useful property that it can slow neutrons down without eating them, so if you embed uranium lumps in a graphite matrix with appropriate spacing, the neutrons which get into the graphite will be slowed down, and when they finally hit a lump of uranium they are likely to be taken up by U-235 and cause fission.Any light element with a sufficient distaste for neutrons can be used as a moderator. Heavy water (deuterium oxide) works nicely. Natural water has slightly too high an appetite for neutrons to work well, but if the concentration of U-235 is raised a bit, you can make a reactor with natural water moderator. That is how power reactors work in the USA and most other countries.
What is the function of a moderator in a reactor?
It is to slow down the neutrons produced in fission. U-235 and Pu-239 capture slow neutrons much more readily than they do fast neutrons, so it makes the chain reaction much more efficient.
