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What type of coolants is usually used to remove heat from a nuclear reactor core?
Wiki User
∙ 10y ago
liquid sodium or water
Wiki User
∙ 10y ago
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How could you increase the rate of fission reactions?
Fission does not respond to changes in temperature and pressure like chemical reactions do. In a nuclear reactor, the fission chain reaction can be sped up by removing rods of cadmium, which absorb neutrons. These are in place to prevent the reaction from occurring too quickly. Remove them, and the chain reaction may proceed out of control.
Fuel used in nuclear reactor?
Uranium or plutonium are usually used in fission reactors, although certain special reactor designs are capable of burning all of the transuranic elements too.Depending on the reactor design this fuel can be packaged in a variety of different ways:uranium oxide powder (aka "yellowcake" because of its color) canned in small zirconium alloy pellets (this is used in the largest number of reactors now operating)short metal rods canned in zirconium alloy or aluminum alloy pelletsuranium oxide and/or plutonium oxide solid ceramic clad in porous carbona solution of uranium sulfate and/or uranium nitrate dissolved in water (this has the advantage of acting simultaneously as fuel, moderator, and coolant and as this liquid is continuously circulating through the reactor core it is possible to easily remove spent fuel, reprocess to obtain plutonium, and refuel without disturbing the reactor operation in any way; however it has the disadvantage that coolant in the primary cooling loop is very radioactive thus the heat exchanger must be shielded and inside the containment building)etc.
How do you remove self adhesive glue?
Goof off will usually remove most self-adhesive glues.
How do you remove dog urine from carpet?
Usually any stain removal will remove it whether it's specifically for pet stains or not.
Why does uranium become radioactive in a nuclear reactor?
Uranium is already radioactive, it does notbecome radioactive in a reactor. Uranium naturally undergoes alpha decay, emitting alpha particles and transforming to Thorium, another radioactive element. The radioactive decay of these daughter isotopes continues via either alpha or beta decay until a stable isotope of lead is produced.Perhaps what you meant to ask is "Why does Uranium fission in a nuclear reactor?".This is because there are low energy neutrons (aka thermal neutrons) in the reactor that can avoid capture by the plentiful Uranium-238 isotope and fission the rare Uranium-235 isotope. Initially when the reactor is being started these thermal neutrons are provided by a device called a neutron source. When the reactor becomes critical (by the operators gradually removing control rods) it sustains a stable fission neutron chain reaction supplying its own neutrons to keep fissioning at a constant rate. The operators then remove the neutron source, as it is no longer needed. The only problem in keeping this chain reaction going is that Uranium-235 fission emits high energy neutrons (aka fast neutrons) which are readily captured by the plentiful Uranium-238 isotope. This problem is solved by a moderator, a substance that rapidly removes energy from the neutrons (slowing them from fast to thermal speeds) before a significant number can be lost in Uranium-238 neutron capture. Typical moderators are: graphite, water, heavy water, hydrocarbons, etc.Perhaps what you meant to ask is "Why do Uranium fuel rods become more radioactive in a nuclear reactor?".The fuel rods become more radioactive in the reactor than they were originally because of the highly radioactive fission product isotopes produced by the Uranium-235 fission (as well as radioactive isotopes produced by neutron capture by stable elements in the structural parts of the fuel rods). These isotopes are more dangerous than the original Uranium was, because they undergo beta and gamma decay, emitting beta particles and gamma rays both of which are more penetrating than than alpha particles are. Also the longer the fuel rods remain in the reactor the more of these fission products build up in the fuel rods. The good thing is these fission products have much shorter halflifes than the original Uranium: they decay rapidly to stable non-radioactive elements.The original Uranium takes billions of years to decay completely to stable lead. The fission products take from hours to centuries to decay completely to stable isotopes. The slowest to decay is gone in about 250 years. Thus, after the decay period the fuel rods are actually less radioactive than they were originally before being put in the reactor. The reactor "burned up" the Uranium, leaving fission product "ashes" which take a few centuries to "cool" completely.You might ask now "What becomes of the Uranium-238 that captured neutrons during the neutron chain reaction in a nuclear reactor?".It becomes Plutonium, some of which the reactor "burns" just like the Uranium-235 and some builds up in the fuel rods (like the fission products do). This Plutonium could be reprocessed(along with unused Uranium) to make new fuel rods, but if not, with a halfllife of about 25,000 years it will take about 125,000 years in storage to completely decay back to Uranium via alpha decay, which as I said already takes billions of years to decay to stable lead isotopes.
If you wanted to slow down the chain reaction in a nuclear reactor would you remove or insert the control rods?
In order to slow down the chain reaction in a nuclear reactor, i.e. to reduce KEff, you would insert the control rods.
Why is a cooling sysyem necessary in a nuclear reactor?
When we talk about the reactor cooling system, the meaning is usually the system for removing the reactor thermal output and transferring it to the steam raising units. This is obviously the way the reactor power is utilised. There are other cooling systems though, the most important being the emergency cooling system which can remove the reactor after heat, after it has been shutdown. This system can be powered by back up diesel generators if the connection to the grid has been lost. There will also be an emergency cooling system for the secondary containment, should there be a large loss of coolant accident, though this is very unlikely to happen.
The function of control rods in a nuclear reactor is to speed up the nuclear reactions?
Control rod act as brakes to reduce the reaction rate. However as nuclear reactors have so much excess reactivity, its like a car rolling downhill: remove the control rods a bit (release the brakes some) and the reaction rate increases.
How do they start a nuclear reactor?
With all control rods inserted all the way, begin inserting fuel rods.When the basic minimum operating number of fuel rods have been inserted, insert a continuous neutron source of known intensity.Measure the neutron flux in the reactor and calculate the reactor's neutron multiplication factor to determine how close you are to design predicted critical.Begin withdrawing control rods very slowly, stopping periodically and repeating step 3. Each time the neutron multiplication factor should increase.If the multiplication factor keeps increasing in step 4 while the control rods are stopped, you have reached critical. Remove the neutron source and the neutron flux in the reactor should decline slightly then become constant.You have now safely started your nuclear reactor. Congratulations!If anything unexpected happens reinsert all control rods, remove the neutron source, find and fix the problem, and restart the procedure.
What happens when a nuclear reactor reaches the end of its life?
When a reactor has burned enough of its fuel that it cannot be made to go critical by pulling all the control rods all the way out, it has reached the end of its useful life. There is a lot of unburned fuel left in the fuel elements, but not enough to achieve criticality the way the reactor core is set up. (Only a small percentage of the fuel is actually burned.) Usually the operators of a nuclear plant will take a reactor out of service and refuel it a bit before this. And military reactors will be taken offline sooner and refueled because of the requirement that the reactor be able to be brought critical at what is called the "peak xenon" point. Generally speaking, the core is removed and put in a storage pool that provided cooling and shielding. The core will remain there until it can be disassembled into fuel bundles and the bundles packed up and moved to a long-term storage facility for a century or a few. It is unusual that the fuel elements are reprocessed to remove the remaining fuel because of the presence of a lot of extremely radioactive fission fragments.
Can normal water be used in nuclear plant?
Yes, though it has to be purified to remove dissolved solids and any other contaminants down to a very low level, this is done with a demineralization plant on the power station site. This applies to any power station using high quality steam, but also on a nuclear station in the reactor coolant circuit.
What safety features are installed in a nuclear power stations?
The most important safety features are the control rods, which can be inserted quickly to shut the reactor down, either automatically in certain faults, or by operator action, and the core emergency cooling system which operates after a reactor trip or scram to remove decay heat from the fuel, and is powered by diesel generators independent of the outside grid connections.
How do you disarm an atomic bomb?
Figure out a way to remove the nuclear material, and there will be no reaction. Unfortunately, atomic bombs are usually dropped from the sky, detonating on impact.
Is the melting point of sodium high or low?
Quite low. Sodium metal is put inside hollow valves of high power internal combustion engines. At operating temperature the sodium melts and the movement of the valve splashes the molten sodium around carrying heat rapidly from the valve face to the stem where the engine cooling system easily carries it away. By this system the part of the exhaust valve that contacts the seat can be kept over 500F cooler, avoiding warping and burning of the valve. Alloyed with potassium it melts just above room temperature. This alloy called NaK is a common Nuclear Reactor coolant where the coolant should not also be a moderator, or the reactor core is too small and dense for nonmetallic coolants to remove heat fast enough.
How would you build a nuclear reactor to avoid a meltdown?
The most important design feature here is that the reactor must have a very large negative temperature coefficient of reactivity. This will ensure that even without active human or computer control working, the reactor will automatically shut itself down long before getting hot enough to begin melting. The next most important design feature is a reliable emergency cooling system that can work even with no power available, to remove fission product radioactive decay heat once the reactor was shutdown (either actively or passively).
What are the fuctions of moderator and controller in nuclear reactor?
moderator, slows fast fission neutrons to thermal (near room temperature) energies rapidly enough to prevent their capture by uranium-238 before they can participate in the chain reaction and fission uranium-235control, remove excess neutrons so as to hold the reactor at exactly critical at all times, permit control of increases and decreases of operating power level
How does a control rod work?
Control rods need to contain material that is a strong absorber of neutrons, so that rapid shutdown can be achieved when necessary. Two such materials are Cadmium and Boron. Both have been used in different types of reactor. The elements may be used as alloys or as chemical compounds, and will be encased in stainless steel to avoid corrosion in the reactor.
