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Why you use slow neutrons instead of fast neutrons in nuclear reaction?
Wiki User
∙ 14y ago
in reacter U-235 fission is due to slow neutrons because in reacter the probability of fission from fast neutron is approximatly zero.
Wiki User
∙ 14y ago
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Are there fast neutrons?
Yes, in fact for a sustainable nuclear chain reaction to work, you have to slow neutrons down.
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.
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.
In nuclear reactor heavy water is used as?
Heavy water (deuterium) functions as a moderator. It slows down fast neutrons released by fission reactions in order to allow the reaction to be sustained. Fast neutrons pass through the reactor before initiating another fission reaction.
What happens if a nuclear chain reaction is not controlled?
The reactor fuel would overheat, melt, and fall apart.
How much temperature can be controlled by liquid sodium in nuclear reactors?
Liquid sodium has been used as a coolant in fast reactors, because it does not slow down and absorb fast neutrons. It does not control the nuclear reaction directly, for that variable neutron absorbers are required.
What is nuclear reactors?
An assembly of fissile fuel (U-235 or PU-239) arranged in a geometric array. The assembly can be made to go critical such that a chain reaction starts which builds up a neutron flux inside the assembly. The chain reaction is controlled at a steady level using neutron absorbing control rods.The nuclear reactor can classified under:a thermal nuclear reactor, where the majority of fissions are caused by slow neutrons. In these reactors, the fast neutrons produced by fissions are slowed down with a moderator which can be graphite, heavy water or light water, anda fast nuclear reactor where the majority of fissions are caused by fast neutrons
What is a nuclear reactor?
An assembly of fissile fuel (U-235 or PU-239) arranged in a geometric array. The assembly can be made to go critical such that a chain reaction starts which builds up a neutron flux inside the assembly. The chain reaction is controlled at a steady level using neutron absorbing control rods.The nuclear reactor can classified under:a thermal nuclear reactor, where the majority of fissions are caused by slow neutrons. In these reactors, the fast neutrons produced by fissions are slowed down with a moderator which can be graphite, heavy water or light water, anda fast nuclear reactor where the majority of fissions are caused by fast neutrons
The way a reactor works and the theory behind nuclear reaction?
A nuclear reactor is composed of several parts:Fuel - fissionable material, typically enriched UraniumModerator - material to rapidly slow fast fission produced neutrons to thermal neutrons, to prevent too many from being captured by non-fissionable Uranium-238 (not used in fast reactors using HEU fuel).Control rods - boron or cadmium rods that absorb excess neutrons, they can be inserted or removed to adjust the reaction rate.Coolant - any material to carry heat out of the core (e.g. water, liquid metals, air).Emergency systems - SCRAM system for emergency reaction shutdown, emergency cooling system to remove decay heat from core after SCRAM, etc.Operator instrumentation and controls - allows operators to interact with the reactor remotely.A nuclear fission chain reaction happens when fissionable fuel Uranium-235 or Plutonium captures a thermal neutron. It quickly splits into two fission fragments and 2 to 6 fast neutrons (the average being between 2 to 3 neutrons). The moderator slows the fast neutrons to thermal neutrons and the reaction continues.
What is a moderator when it concerns nuclear energy?
A moderator is a material that slows fast neutrons.
How is plutonium used in nuclear reactors?
Plutonium is used in nuclear reactors as a nuclear fuel (as dioxide, carbide or MOX). The isotopes 239Pu and 241Pu are fissionable with thermal neutrons; other isotopes are fissionable only with fast neutrons.
what is fission chain reaction how can it be controlled?
Fission chain reactions occur because of interactions between neutrons and fissile isotopes (such as 235U). The chain reaction requires both the release of neutrons from fissile isotopes undergoing nuclear fission and the subsequent absorption of some of these neutrons in fissile isotopes. When an atom undergoes nuclear fission, a few neutrons (the exact number depends on several factors) are ejected from the reaction. These free neutrons will then interact with the surrounding medium, and if more fissile fuel is present, some may be absorbed and cause more fissions. Thus, the cycle repeats to give a reaction that is self-sustaining. Nuclear power plants operate by precisely controlling the rate at which nuclear reactions occur, and that control is maintained through the use of several redundant layers of safety measures. Moreover, the materials in a nuclear reactor core and the uranium enrichment level make a nuclear explosion impossible, even if all safety measures failed. On the other hand, nuclear weapons are specifically engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started. When properly designed, this uncontrolled reaction can lead to an explosive energy release
