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In a nuclear reactor why does the moderator need to slow down the neutrons?
Wiki User
∙ 9y ago
Nuclear fission of Uranium-235 is more efficient when hit by neutrons with low energy of the order of electron volts. However, neutrons coming from fission are at high energies around 2 megaelectron volt. Accordingly, the moderator is needed to slow down the neutrons coming from fission to low energy values through scattering process with moderator molecules. This is the concept of the so called "thermal nuclear reactors"
Wiki User
∙ 9y ago
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Do moderator in nuclear reactor slows down the neutrons emitted during fission?
Yes, it is the main moderator function in what is called "thermal nuclear reactors"
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 moderator is not used in case of fast breeder reactor?
Moderator is not used in case of fast breeder reactor because there is no need to slow down neutron energy. Nuclear fission takes place at high energy of neutrons.
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.
Which material is used in controlling chain reaction in nuclear reactor?
The material used to slow down high-speed neutrons in a reactor is called the moderator. The moderator in a pressurized water reactor is the water, which is the main coolant. Collisions between the neutron and hydrogen nuclei (protons) slow the neutron down (thermalizing it) and increasing the probability that it will be absorbed by another fissionable atom. That makes the chain go, it maintains the chain reaction. Slowing down neutrons does NOTslow down the process of nuclear fission. If anything, it maintains it or speeds it up because slower moving neutrons have a higher probability of being absorbed and continuing or building the chain reaction. A link is provided.
Slows down neutrons in a nuclear reactor?
moderator
Do moderator in nuclear reactor slows down the neutrons emitted during fission?
Yes, it is the main moderator function in what is called "thermal nuclear reactors"
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 moderator is not used in case of fast breeder reactor?
Moderator is not used in case of fast breeder reactor because there is no need to slow down neutron energy. Nuclear fission takes place at high energy of neutrons.
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.
What is a moderator in a nuclear reactor?
A moderator is a substance that helps slow down the neutrons so that they can collide with other nuclei to perpetuate the fission reaction (instead of just zipping by at high speeds and missing the nuclei completely most of the time).
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.
Which material is used in controlling chain reaction in nuclear reactor?
The material used to slow down high-speed neutrons in a reactor is called the moderator. The moderator in a pressurized water reactor is the water, which is the main coolant. Collisions between the neutron and hydrogen nuclei (protons) slow the neutron down (thermalizing it) and increasing the probability that it will be absorbed by another fissionable atom. That makes the chain go, it maintains the chain reaction. Slowing down neutrons does NOTslow down the process of nuclear fission. If anything, it maintains it or speeds it up because slower moving neutrons have a higher probability of being absorbed and continuing or building the chain reaction. A link is provided.
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 moderator in US nuclear power plants?
Neutrons released from the fissioning, or splitting, of Uranium or Plutonium atoms collide with the molecules of the moderator, losing some of their energy in the process. This slows the neutrons down (slow neutrons are referred to as "thermal" neutrons") so that they are more likely to cause fission when colliding with another Uranium or Plutonium atom. In the most common types of reactors the moderator used is ordinary distilled water which is also used as the coolant for the reactor. Graphite and heavy water can also be used, and there are types of reactors which use no moderator at all - they operate on "fast" neutrons alone.
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
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
