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In a controlled nuclear reaction it's critical that excess neutrons are absorbed what is or are used to do this?
Wiki User
∙ 14y ago
control rods
Wiki User
∙ 14y ago
Meme Warrior
jotinacastillo
Wiki User
∙ 14y agoThe nuclear chain reaction needs to proceed at a steady rate so that the reactor power is steady. Each fission produces on average about 2.5 fast neutrons, which are slowed down by the moderator so that they are more likely to be captured by a fissile nucleus, so continuing the chain. Clearly to sustain a steady rate of fissions the population of neutrons needs to remain steady from one generation to another, so the excess neutrons need to be captured by some process that does not give rise to more fissions than are needed. Some are captured by the moderator, some by other material in the reactor structure, some escape at the core boundaries and so are absorbed in surrounding structures, and the remainder by the control rods, which can be raised/lowered to maintain a fine balance. When balanced the reactor state is said to be just critical.
Wiki User
∙ 14y agoYou don't say what you mean by 'the following'
Wiki User
∙ 14y agol would need to know what 'the following' are!!
Wiki User
∙ 13y agoYou don't say what your list of "the following" consists of. Boron is most commonly used in control rods.
Wiki User
∙ 14y agocontrol rods
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What happens if a nuclear chain reaction is not controlled?
The reactor fuel would overheat, melt, and fall apart.
How is a chain reaction in a nuclear reactor controlled?
Nuclear reactors contain rods made of materials which will absorb neutrons. This reduced the cascade of neutrons which are responsible for the chain reaction.
What does nuetron absorption accomplish in a nuclear reactor?
Neutron absorption is the key to the operation of a nuclear reactor as this is what perpetuates the chain reaction. Neutrons can be absorbed by a number of things within the core of an operating reactor, but when a fuel atom absorbs a neutron, it becomes unstable and fissions. The fission event releases fission fragments, energy, and more neutrons, which will, when absorbed, continue the chain reaction.
Why must neutrons in a chain reaction be controlled?
Neutrons in a nuclear fission chain reaction must be controlled for two reasons... First, they must be moderated, or "slowed down", to exactly the right level of energy required to sustain the reaction. This is because, initially, the neutrons are too fast to sustain the fission reaction. They must be slowed down, but not too much, otherwise the reaction will stop. Second, they must be controlled. You want the reaction to proceed at an orderly pace, at a constant rate. To do this, you need, on a statistical average, exactly one neutron to go on to fission one atom to produce one parcel of binding energy release and one neutron, to repeat without multiplying or dividing. This is what we call KEffective = 1, where the rate of reaction does not change. Moderation and control. In tight balance. Easily upset. Fortunately, when upset, the tendency is to shutdown. That is engineering safety.
What is the amount of fissionable material that must be present in order for a nuclear reaction to take place called?
The critical mass. With an amount of U-235 or Pu-239, the smallest critical mass will be a sphere. For a nuclear reactor, it will be the minimum number of fuel assemblies loaded to produce a chain reaction.
What does neutron moderation counteract?
the minimal chance that newly formed neutrons of a fussion reaction are absorbed by moore atoms
What happens if a nuclear chain reaction is not controlled?
The reactor fuel would overheat, melt, and fall apart.
What is the amount of fissionable material required to continue a reaction at a constant rate?
At less than critical mass, there are fewer "targets" for neutrons to strike, fission, and release more neutrons. As a result, the reaction dies out.
How is fission inside a powerplant controlled?
The fission is controlled by inserting rods made of a material that absorbs the neutrons. This keeps the reaction from continuing, or slows the chain reaction.
How is a chain reaction in a nuclear reactor controlled?
Nuclear reactors contain rods made of materials which will absorb neutrons. This reduced the cascade of neutrons which are responsible for the chain reaction.
A fission chain reaction can be controlled by using materials that will?
Absorb neutrons. Examples are boron and cadmium
How does a chain reaction start in chemistry?
In a nuclear fissionchain reaction, neutrons are absorbed by large nuclei, and they undergo fission, part of the fission products are more neutrons, which are absorbed by more nuclei, which ... blah, blah, blah.
Neutron moderation is used to counteract what?
the minimal chance that newly formed neutrons of a fission reaction are absorbed by more atoms. (apex)
Does a chain reaction involve fission?
Yes, a chain reaction is all fission, just out-of-control fission. Usually, fission creates 2 neutrons per decay, but it is controlled by the fact that lots of neutrons get absorbed by U-238, which doesn't fission, unlike U-235, which does, and by the control rods, which also absorb lots of neutrons. But if these fail to contain the outbreak of neutrons, and the fail safes (which usually just drop the control rods totally into the reactor, stopping any chain reaction) fail, then an exponentially accelerating chain fission reaction can start, and once it starts, it's pretty much impossible to stop.
What is neutron moderation used to counteract against?
the minimal chance that newly formed neutrons of a fission reaction are absorbed by more atoms. (apex)
What does nuetron absorption accomplish in a nuclear reactor?
Neutron absorption is the key to the operation of a nuclear reactor as this is what perpetuates the chain reaction. Neutrons can be absorbed by a number of things within the core of an operating reactor, but when a fuel atom absorbs a neutron, it becomes unstable and fissions. The fission event releases fission fragments, energy, and more neutrons, which will, when absorbed, continue the chain reaction.
What is a self sustained nuclear fission chain reaction controlled by?
In most nuclear reactors control rods are used, which contain some material that absorbs neutrons, like boron. These can be finely adjusted to keep the reactor just critical, or dropped in to shutdown quickly if necessary.
