Nuclear Reactors

There is no fixed number, but most nuclear stations have two reactors. These are usually run quite separately, with separate generating equipment, so that whilst one reactor is being refuelled the other can continue to produce power. Some stations have more than two reactors, but usually then they have been built over a long time period and the later ones may be of an improved design.

The amount of uranium-235 used in a nuclear reactor depends on the design and size of the reactor. Typically, a reactor core contains several tons of uranium fuel, with the concentration of uranium-235 ranging from 3-5%. The fuel is arranged in fuel assemblies to sustain a controlled nuclear fission chain reaction.

Nuclear reactors produce very low greenhouse gas emissions during operation, as they do not burn fossil fuels. However, there are some emissions associated with the mining and processing of uranium fuel, construction of the facilities, and potential accidents. Overall, the emissions from nuclear power are significantly lower than those from fossil fuel-based energy sources.

You can work out the gas flow from the gas circulator characteristics, and measure the reactor inlet and outlet temperatures, so you can work out the reactor thermal output. Then you can measure the thermal conditions in the steam circuit from feed flow and temperature and steam temperature and pressure, this will give the reactor thermal output together with the gas circulator heat input. From all this data work out the best estimate for the reactor output. The generator output is straightforward, then you have to subtract the power being used on the plant for driving the gas circulators and feed pumps etc, to get the net electrical output, then it is just the ratio of that to the reactor thermal output.

Lightning bolts are discharges of electricity. Nuclear reactors contain mainly uranium. Stars contain light elements undergoing nuclear fusion. I don't see any common form of matter.

Actually, plasma is found in all of them.

In a nuclear reactor, materials such as water or graphite are commonly used as neutron moderators to slow down fast-moving neutrons to speeds where they are more likely to induce fission in uranium or plutonium atoms. Slowed down neutrons are termed thermal neutrons and are key to sustaining a nuclear chain reaction.

Fission of Uranium-235, splitting of this atom into two smaller atoms of different elements. A neutron must hit the nucleus at just the right speed to cause the Uranium-235 to undergo fission. When the Uranium atom is split into smaller atoms called fission products, free neutrons are released which can split more Uranium atoms. The fission product atoms separate at high speed, transferring lots of energy to its surroundings making them very hot. This heat is used to boil water, making steam which is used to turn turbines. The turbines turn generators which produce electricity.

They are used in nuclear reactor to control the rate of fission of uranium and plutonium. Because these elements have different capture cross sections for neutrons of varying energies, the compositions of the control rods must be designed for the neutron spectrum of the reactor it is supposed to control.

Reactors can be fueled by uranium or many of the transuranic elements, but uranium is the only element that occurs naturally with large enough levels of its fissionable isotope uranium-235 for practical use.

Plutonium is also a good reactor fuel, but must be produced first from the plentiful but nonfissionable uranium-238 in a reactor as it only occurs naturally at trace levels.

While thorium cannot be directly used as fuel, the fissionable isotope uraniuum-233 which can be used as fuel can be produced from it in a nuclear reactor.

For transuranics other than plutonium (and maybe americium) specially designed fast neutron reactors are required to effectively use them as fuel, but they too can be used.

• 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-235
• control, 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

The element used as a fuel component in most nuclear reactors is uranium. Specifically, uranium-235 is the primary isotope used for nuclear fission reactions in nuclear power plants.

The nuclear reactor that exploded and burned in the 1980s was located near the town of Chernobyl in Ukraine. The Chernobyl disaster, which occurred in 1986, released a significant amount of radioactive material into the environment and is considered one of the worst nuclear accidents in history.

India's first nuclear reactor is situated in the ''Rajasthan, porbandar.''

Any fissile material would do, but Uranium is the most common.

The controlled release of nuclear energy in a reactor is accomplished by controlling the rate of fission reactions through the use of control rods. These rods absorb neutrons and regulate the nuclear chain reaction to maintain a constant and safe level of energy production. Additionally, the coolant in the reactor helps remove heat and regulate the temperature to prevent overheating.

The power required to start a nuclear reactor varies depending on the size and type of reactor, but typically ranges from a few hundred megawatts to several gigawatts. Once the reactor is operating, it generally requires a smaller amount of power to maintain criticality and sustain the fission chain reaction, usually around 1-5% of the total reactor power output.

• Nuclear power plants are more efficient than ever before. New technology has made them more reliable (they break down less often) and safer. People for nuclear power argue that this is evidenced by more and more nations (such as China) building nuclear power plants.
• Reduce greenhouse gas emissions. This is a contentious issue. Proponents of nuclear power argue that, as no coal or fossil fuels are burnt, no carbon dioxide is released into the air. However, uranium has to be mined and transported to the nuclear plant. Both these activities require burning of fuels, so carbon dioxide is released. Also, producing nuclear fuel from the uranium requires a lot of energy, which also contributes to the emission of greenhouse gases.
• Although the initial cost of building nuclear plants is high, the running costs are relatively low.
• One reason the costs are low is that nuclear plants need only a small amount of uranium to produce a lot of energy. In fact, if the cost of uranium doubled, costs would only be increased by 7%. 1 truck of uranium produces as much energy as 1000 trucks of coal!
• Reduces dependence on foreign oils and natural gas (like biofuels). America, for instance, imports a lot of oil and natural gas from other countries. The price of these products is volatile, and change very quickly. If the price increases quickly, consumers have to pay more for their electricity (which they may not be able to afford). Building more nuclear power plants means that Americans will not be susceptible to price rises in oil and gas. President Barack Obama supports this idea of 'energy independence'.
• Nuclear wastes can be safely stored underground (another debated issue).

The primary function of a moderator in a nuclear reactor is to slow down the fast neutrons produced during fission reactions, making them more likely to cause additional fission events. This helps sustain a chain reaction by ensuring a sufficient number of neutrons are available to continue the process. Common moderators include water, graphite, and heavy water.

It is not possible for a nuclear reactor to explode in the way a nuclear bomb does, because the fissionable part of the fuel is spread out through the reactor in a matrix, in a bomb a critical mass has to be formed very quickly to make the explosion happen.

What is possible is some sort of failure in the reactor's pressure circuit, releasing the coolant and causing fuel to melt thus leaking radioactivity to the environment. This is what happened at Chernobyl, a steam pressure surge blew the top of the reactor off, and some fuel was ejected, then the remains of the reactor caught fire (it was graphite moderated) and released even more activity. It must be emphasised however that this did not happen during normal operation. It was due to an experiment that was badly planned and carried out, together with some design faults that had not been assessed thoroughly enough.

PWR's and BWR's used in the US and elsewhere are very different. A massive disruptive failure of the pressure vessel can be discounted because of design overkill and thorough inspection before use. Some smaller coolant circuit failures are deemed credible and are allowed for in safety studies. The main protection is that the reactor has secondary containment, this is the large dome that is characteristic of reactors seen from outside the plant.(Chernobyl did not have this). In the Three Mile Island incident coolant did leak out through a valve that the operators did not know was open. This shows the necessity of better instrumentation and this has been taken into account in new designs. No significant radiation exposure happened to the nuclear staff or the public nearby, though the reactor was damaged and has never operated since.

Because "ordinary" uranium is mostly 238U, which won't fission and create a chain like its lighter cousin 235U will. When critical mass is achieved with the 235U isotope of uranium, fission will occur spontaneously. Or with a significantly enriched uranium fuel (one where the natural concentration of 235U has been increased a bunch so the fuel has a much higher percentage of this isotope), fission and a chain reaction is also possible. But with just natural uranium, a big pile of it will just sit there. It won't fission and create a chain reaction. Note that 238U is radioactive and decays over time because it is unstable, but it has a long half-life. Also, the fact that it's unstable (radioactive) doesn't mean it's fissile. It isn't.

A nuclear fission reaction is controlled in a nuclear reactor by using control rods made of materials that absorb neutrons, such as boron or cadmium. By adjusting the position of these control rods within the reactor core, the rate of fission and thus the power output can be regulated. Inserting the control rods absorbs neutrons and reduces the number available for further fission reactions, helping to maintain a steady power level.

it comes from nuclear fission
Nuclear energy is the fission of certain, materials such as uranium or plutonium,within a nuclear reactor. This produces heat, which turns water into steam. This steam rises, driving a turbine which creates electricity for commercial and public use.