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What is the function of the moderator in a boiling water reactor?
Wiki User
∙ 14y ago
The moderator in a reactor serves to slow down, or moderate, neutrons so they can be more effective in interacting with other nuclei. This is needed as most neutrons emitted from fission reactions in power reactors are fast neutrons that tend to not participate well in the chain reaction. Slowing them down increases the probability that their subsequent involvement with other nuclei will result in better capture, with the end result of better odds of destabilizing those other nuclei, which causes reactivity to continue.
In a boiling water reactor (BWR), the primary moderator is water. This water carries away the energy released from fission so that it can be converted into electricity, it cools the reactor so that it does not overheat, and it moderates the chain reaction, supporting a constant level of reactivity.
The moderation effect of water is proportional to density, which is proportional to pressure and inversely proportional to temperature. As a result, anything that cools the water increases reactivity, and anything that depressurizes the water decreases reactivity. This gives you the best of both worlds...
If the steam demand increases due to increased electric demand, the water cools and reactivity increases to meet the demand. Conversely, a decrease in demand warms the water, and reactivity decreases. This makes the reactor self stabilizing.
If the pressure were to decrease, such as from a loss of coolant accident (LOCA) or some kind of leak, the water would flash to steam, suddenly reducing density, and reactivity would suddenly decrease, stopping the chain reaction.
At relatively low power levels, say below 25%, primary power control is the control rods, but the self stabilizing effect of the water moderator remains in force. At higher power levels, primary power control is the recirculating water pumps, which tends to remove steam voids, increasing density, and increasing power. Self stabilization still remains in force.
Wiki User
∙ 14y ago
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How big is the reactor vessel in a boiling water reactor?
A reactor vessel in a boiling water reactor is approximately 300 tons.
Which is used as moderator in nuclear reactor?
Most often, light water (H2O) is used as a moderator in a nuclear reactor. Sometimes, heavy water (D2O), or graphite is used.
What is PWR or BWR?
PWR = pressurised water reactor. BWR = boiling water reactor
The moderator used in the nuclear reactor at Madras atomic power station in Kalpakkam is?
Heavy water(PHWR)--Pressurised heavy water reactor
A boiling water nuclear reactor delivers what to the turbine blades?
Steam
How can neutrons be slowed in the reactor core?
This is the function of the moderator, which may be heavy water, light water, or graphite
Are the PHWR and PWR are same?
They are the same in that they don't allow reactor coolant water boiling in the primary water coolant loop. They are different in that in PHWR the moderator is heavy water while in PWR the moderator is normal light water.
How big is the reactor vessel in a boiling water reactor?
A reactor vessel in a boiling water reactor is approximately 300 tons.
Which is used as moderator in nuclear reactor?
Most often, light water (H2O) is used as a moderator in a nuclear reactor. Sometimes, heavy water (D2O), or graphite is used.
Are there more are there one type of nuclear reactor?
the boiling water reactor, pressurized water reactor, and the LMFB reactor
What is PWR or BWR?
PWR = pressurised water reactor. BWR = boiling water reactor
The moderator used in the nuclear reactor at Madras atomic power station in Kalpakkam is?
Heavy water(PHWR)--Pressurised heavy water reactor
Two important functions of heavy water in a candu reactor?
moderator, coolant
Why do you keep the Ph of moderator neutral in pressurized heavy water reactor?
This is done in order to limit corrosion of the internal reactor components
What are the moderator used in a nuclear reactor with natural uranium?
The moderator used in nuclear reactors with natural uranium is generally the heavy water (D2O).
Can you use tritium water as moderator in nuclear reactor?
Yes, but it would usually be too expensive as tritium must be made in a reactor from lithium.
What are some nonexamples fo nuclear fission?
Pressurised Water Reactor (PWR), Boiling Water Reactor (BWR)
