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Neutron moderation is used to counteract what?
the minimal chance that newly formed neutrons of a fission reaction are absorbed by more atoms. (apex)
A nuclear fission chain reaction of U-235 starts with a slow neutron. What produces this first neutron?
Uranium is naturally radioactive; it's unstable. Somewhere in a sample of uranium, spontaneous fission occurs. All the time. Neutrons are released in this reaction. It cannot be stopped. If critical mass is assembled, a couple of neutrons will appear from a spontaneous fission somewhere within the sample, and a chain will immediately begin to build. There is no way to stop it except by separating the mass into subcritical quantities. But the reaction will do that. It happens in the twinkling of an eye. Always. Note that a so-called fast neutron, a neutron with a lot of kinetic energy, can cause fission. But it has a lot lower probability of doing that than a thermal neutron. Slowing down or "thermalizing" of neutrons increases the chance that they will be captured, and neutron capture will build a chain reaction. This was included because the question stated that a chain starts with a slow neutron, and this might not be the case. It is the slow neutrons that drive the fission chain in nuclear reactors. They have moderators to slow the neutrons down. But the fast neutrons are the chain builders in nuclear weapons. In a nuclear weapon, we don't put moderator material in the thing. We might incorporate some neutron mirrors or lenses in the geometry of the device, but we rely on the a lot of fast neutrons to carry out the mission of burning the fissile material very rapidly to get a big yield. The proof is in the pudding.
How can the fission be controlled or stopped in a nuclear reactor?
The nuclear chain reaction is controlled using neutron absorbing control rods containing boron, and in PWR's by also using soluble boron when necessary. Nuclear engineers use a term called reactivity, which just means the surplus of neutrons from one generation to another, and in steady operation this is zero. During the fission reactions fission products are produced, some of these are neutron absorbers like Xenon131, and their concentration changes with power changes, so that adjustments with the control rods are necessary following such changes. On start-up with new fuel for example it takes some hours before equilibrium xenon is reached, and if power has to be reduced the xenon rises again as a delayed action, so enough control to overcome the increased poisoning has to retained, or the reactor will shut itself down. The reactivity with new fuel loaded is higher than at the end of the fuel life, and this is where boric acid added to the reactor water circuit is useful. The reactor power (neutron flux level) is constantly monitored with instruments so that the control room staff know what is happening and can respond. In addition automatic safety circuits are triggered if there is an increase in flux beyond a certain point which the operators don't react to, and this inserts the control rods fully (scram or trip) which shuts the reactor down and holds it down. So there is no chance of a runaway.
What happend to lone neutrons?
A neutron has a lifetime of about 15 minutes. This means that if you wait roughly 15 minutes there is a good chance the neutron will have decayed into other particles. So lone neutron just decay quickly, that is why there aren't any around. A neutron in an atomic nucleus is stable however (fortunately for us!).
Why are neutrons used as nuclear bullets to cause nuclear disintegration of an unstable nucleus?
Neutrons have no charge. As a result, they are not deflected by the positive charge of the nucleus or the negative charge of the electron cloud. They have the best chance of interacting with the nucleus and further destabilizing it, causing it to split.
What does neutron moderation counteract?
the minimal chance that newly formed neutrons of a fussion reaction are absorbed by moore atoms
Neutron moderation is used to counteract what?
the minimal chance that newly formed neutrons of a fission reaction are absorbed by more atoms. (apex)
What is neutron moderation used to counteract against?
Neutron moderation is used to counteract against the high speed (fast) neutrons produced during nuclear fission. By slowing down the neutrons through moderation, they are more likely to cause further fission reactions in nuclear reactors, sustaining the chain reaction.
A nuclear fission chain reaction of U-235 starts with a slow neutron. What produces this first neutron?
Uranium is naturally radioactive; it's unstable. Somewhere in a sample of uranium, spontaneous fission occurs. All the time. Neutrons are released in this reaction. It cannot be stopped. If critical mass is assembled, a couple of neutrons will appear from a spontaneous fission somewhere within the sample, and a chain will immediately begin to build. There is no way to stop it except by separating the mass into subcritical quantities. But the reaction will do that. It happens in the twinkling of an eye. Always. Note that a so-called fast neutron, a neutron with a lot of kinetic energy, can cause fission. But it has a lot lower probability of doing that than a thermal neutron. Slowing down or "thermalizing" of neutrons increases the chance that they will be captured, and neutron capture will build a chain reaction. This was included because the question stated that a chain starts with a slow neutron, and this might not be the case. It is the slow neutrons that drive the fission chain in nuclear reactors. They have moderators to slow the neutrons down. But the fast neutrons are the chain builders in nuclear weapons. In a nuclear weapon, we don't put moderator material in the thing. We might incorporate some neutron mirrors or lenses in the geometry of the device, but we rely on the a lot of fast neutrons to carry out the mission of burning the fissile material very rapidly to get a big yield. The proof is in the pudding.
How is a uranium-235 nucleus made to undergo fission?
Nuclear fission is the splitting up of big atomic nuclei. Uranium is quite a large nuclei. Each time a uranium atom splits up, it spits out two or three neutrons. One of which might hit another nuclei causing it to split - thus keeping the chain reaction going. The uranium atom - when hit by a neutron splits into Barium and Krypton.
If your sister is a twin what is your chance of having twins?
actually u have a greater chance of twins then
Is it a greater chance of landing on boardwalk or Illinois on monopoly?
Every site on the board has an equal chance.
What dog has a greater chance of biting?
Pit Bulls
Why immigrants came to cities?
for a greater chance of employment
What does Vincent say that a child conceived in love has a greater chance of in the movie 'Gattaca'?
Vincent said, "They used to say that a child conceived in love has a greater chance of happiness."
Which value shows a greater probability that the result did not occur by chance 0.05 or 0.001?
In the context of significance tests, the value of 0.001 indicates a lesser likelihood that the event occurred by chance, that is a greater probability that it did not occur by chance.In the context of significance tests, the value of 0.001 indicates a lesser likelihood that the event occurred by chance, that is a greater probability that it did not occur by chance.In the context of significance tests, the value of 0.001 indicates a lesser likelihood that the event occurred by chance, that is a greater probability that it did not occur by chance.In the context of significance tests, the value of 0.001 indicates a lesser likelihood that the event occurred by chance, that is a greater probability that it did not occur by chance.
How does binary fission result in bacteria becoming resistant to antibiotics?
the genes of the bacteria have to be replicated, allowing for the chance of genetic mutation.
