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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 else can I help you with?
Can the chain reaction of nuclear fission be stopped or controlled?
Yes, the chain reaction of nuclear fission can be controlled by using control rods made of materials like boron or cadmium that absorb neutrons, thus regulating the rate of fission. Additionally, cooling systems can also be used to control the temperature and prevent the reactor from overheating.
True or false the energy from nuclear fission is released as heat?
True. Nuclear fission is a process in which the nucleus of an atom is split into two or more smaller nuclei, releasing a large amount of energy in the form of heat and radiation.
What kind of energy is given from a nuclear fission reaction?
The initial release of energy is in the form of kinetic energy of the fission fragments, but they are quickly stopped inside the fuel and the energy appears as heat, which is then passed into the coolant, whether water or gas.
What kind of energy is given off from a nuclear fusion reaction and from a nuclear fission reaction?
the "disappearance" of a small amount of mass. Most of the energy from nuclear fusion of deuterium and tritium, which is the most likely reaction to be harnessed by man, is given off as kinetic energy of the neutrons formed. This is one of the problems involved-how to make use of this energy, even when the plasma can be contained and made to fuse, which has only been achieved for brief bursts so far. The neutrons will have to be stopped in some material surrounding the plasma to produce heat, but what material will stand up to these conditions is not clear. In nuclear fission most of the energy appears first as kinetic energy of the fission fragments, which are then stopped in the fuel resulting in heat being generated which can be removed by the coolant, water or gas. There is also some gamma ray energy released.
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.
Can the chain reaction of nuclear fission be stopped or controlled?
Yes, the chain reaction of nuclear fission can be controlled by using control rods made of materials like boron or cadmium that absorb neutrons, thus regulating the rate of fission. Additionally, cooling systems can also be used to control the temperature and prevent the reactor from overheating.
What could happen if the water stopped flowing through a nuclear reactor?
If water stopped flowing through a nuclear reactor, the cooling system would fail, leading to a buildup of heat. This could result in the fuel rods overheating and potentially melting down, causing a severe nuclear accident like a meltdown. Cooling water is essential for regulating the temperature and preventing the reactor from overheating.
How did the Nuclear reactor get damiged?
If you are talking about the Nuclear Reactors in Japan, they were damaged because when they lost power, the water pumps used to cool them stopped, and all of the nuclear material overheated.
How does the control rod affect the rate of reaction in the nuclear reactor?
Control rods absorb neutrons in a nuclear reactor, regulating the rate of fission reactions by controlling the number of free neutrons available to cause further reactions. By inserting control rods into the reactor core, the reaction rate can be slowed down or stopped, while retracting them allows the reaction rate to increase.
Why is the nuclear reactor surrounded by a thick concrete layer?
To stop radiation leaking out. Alpha and Beta types of radiation will be stopped by the concrete
True or false the energy from nuclear fission is released as heat?
True. Nuclear fission is a process in which the nucleus of an atom is split into two or more smaller nuclei, releasing a large amount of energy in the form of heat and radiation.
What is done to keep the nuclear reactor under control?
control rods act like brakes to slow the neutron chain reaction rate in normal operation. the SCRAM system acts in emergencies to completely bring the neutron chain reaction to an instant stop. even with the reactor stopped, the cooling system must operate to prevent overheating from the radioactive decay of the built up fission products.
What kind of energy is given from a nuclear fission reaction?
The initial release of energy is in the form of kinetic energy of the fission fragments, but they are quickly stopped inside the fuel and the energy appears as heat, which is then passed into the coolant, whether water or gas.
When an atom splits (fission) what kind of energy is produced?
The nuclear energy released appears initially as kinetic energy of the fission fragments, but they are quickly stopped in the surrounding material and the energy then turns to heat. There is also some gamma ray energy released.
What is the type of energy transfer taking place during nuclear energy?
Nuclear energy is produced in fission by the destruction of mass (a small proportion of the mass of the U-235 nucleus). The energy appears initially as kinetic energy of the fission fragments, which are quickly stopped inside the fuel rods and the energy is converted to thermal energy (heat)
Why can the flow of water be controlled but not stopped?
Because it is to powerful to be completely stopped but it can be controlled for a small period of time.
Severe overheating of a nuclear reactor core?
The ultimate would be to cause melting of the fuel. It must be shown (theoretically) that this would be contained in the bottom of the reactor vessel. The fission chain reaction would have stopped but there is after heat from radioactive decay and this must be absorbed by emergency cooling to avoid damage to the vessel. This is an extreme case and might be caused by a severe loss of cooling accident, but is very unlikely in most reactors.
