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What raw materials is graphite made of?
Like diamonds, graphite is what's known as an allotrope of carbon. That means it is actually carbon, although it ocurs in a different form in nature. Graphite occurs naturally as an ore; it is considered by some to be a high form of coal, although this reference is uncommon as graphite is hard to light and makes a poor fuel source.
What substances are used as moderators in a nuclear reactor?
Substances commonly used as moderators in nuclear reactors include light water (H2O), heavy water (D2O), and graphite. These materials help slow down fast-moving neutrons to speeds at which they are more likely to cause fission in uranium fuel.
What is the most common coolant used in nuclear reactors?
The most common coolant used in nuclear reactors is water, in either liquid or steam form. Water provides effective heat transfer properties and is readily available and cost-effective. Other coolants, such as liquid sodium or gas, are used in specialized reactors but water-cooled reactors are the most prevalent.
Why is graphite used as a moderator in some nuclear reactors?
It is used as a moderator. Natural uranium will not undergo nuclear fission by itself because neutrons emitted by fissioning U-235 tend to be absorbed by U-238. However, if the neutrons can be slowed down, it turns out that U-238 is less likely to eat them, and enough are available to fission U-235 and keep the reaction going. Graphite has the useful property that it can slow neutrons down without eating them, so if you embed uranium lumps in a graphite matrix with appropriate spacing, the neutrons which get into the graphite will be slowed down, and when they finally hit a lump of uranium they are likely to be taken up by U-235 and cause fission.Any light element with a sufficient distaste for neutrons can be used as a moderator. Heavy water (deuterium oxide) works nicely. Natural water has slightly too high an appetite for neutrons to work well, but if the concentration of U-235 is raised a bit, you can make a reactor with natural water moderator. That is how power reactors work in the USA and most other countries.
Is graphite black?
Graphite is made up of sheets of conjugated aromatic benzene rings. If you consider the structures of dye molecules, you will see that the more conjugated a dye molecule is, the higher the extinction coefficient. Graphite is in effect the ultimate conjugated organic system; it has unlimited pi electrons to absorb light. So Graphite absorbs all light, however reflects none.
How nuclear energy is used today?
Mostly in reactors fuelled by Uranium and moderated and cooled by light water (PWR and BWR types)
Most of the world's nuclear reactors are of the type?
Most are lightwater moderated and cooled, these are the PWR and BWR. There also a substantial number of heavy water reactors, based on CANDU, and gas cooled reactors mainly now in the UK.
What are nuclear reactors called?
One type (model) of reactor is the CANDU, or Canada (CAN) dueterium-uranium (DU)reactor. Ther are also differences between fusion and fission reactors, fast and thermal reactors (the differences bing in the speed of the neutrons used to initiate the chain reaction, usually fission), light or heavy water cooled or moderated reactors, and many other distinctions.
What is the transparency of graphite?
Graphite is considered transparent because it allows light to pass through it. However, its transparency is limited due to its layered structure, which can scatter and absorb light.
What is a graphite reactor?
A reactor using graphite as the moderator. This has the advantage that natural non enriched uranium can be used. The first reactors built in the WW2 project to produce plutonium were graphite, these were at Hanford. The idea was taken up in the UK and in France and pressurized reactors using CO2 coolant were developed, though these are now all obsolete. The trouble with graphite is it has a limited lifespan in the reactor, gradually eroding and so losing mechanical integrity. It also is a possible fire hazard, as graphite is flammable at temperatures reachable during a nuclear accident (as evidenced by the Chernobyl accident), particularly in oxygen and hydrogen-rich environments found inside such sealed reactors. Nevertheless in the UK the advanced gas cooled reactor was developed which used enriched fuel and higher gas temperature. These were eventually made to work quite well, but turned out too expensive to build compared with the simpler PWR and BWR types which now predominate.
What are the two substances used as moderators in nuclear reactors?
Moderators contain materials that rapidly slow neutrons down to thermal speeds without absorbing a significant number of neutrons. A few of these are:carbon, usually in the form of graphiteheavy waterlight waterhydrocarbons, like oilsberyllium (usually too expensive)etc.
What is the color for graphite?
Light brown
Is graphite metallic or non metallic?
Graphite is not metallic it just "shines" when the light shines on it
Which one among the following is used as a moderator in nuclear reactors?
The most common moderator used in nuclear reactors is water, particularly light water (H2O). Water slows down the fast neutrons produced during fission reactions, allowing them to more easily induce further fission events.
What is VVER-1000 type nuclear reactor?
light water moderated Soviet designed reactor
Who invented the first nuclear reactor for electrical power?
This is usually credited to Eugene P. Wigner, Leo A. Ohlinger, Gale J. Young, and Alvin M. Weinberg in their US Patent #2,736,696 titled Reactor, applied for August 29, 1945 and granted February 28, 1956. While this patent applies specifically to a heavy water moderated, light water cooled type of power reactor and the vast majority of modern power reactors are derived the the later light water moderated, light water cooled type of power reactor designed by Hyman G. Rickover for the nuclear submarine USS Nautilus, this patent and its inventors have precedence over the work of Rickover. Weinberg specifically worked with Rickover and contributed greatly to the success of Rickover's work with nuclear power reactors.
What is a light water reactor?
The nuclear fission reactors used in the United States for electric power production are classified as "light water reactors" in contrast to the "Heavy Water Reactors" used in Canada. Light water (ordinary water) is used as the moderator in U.S. reactors as well as the cooling agent and the means by which heat is removed to produce steam for turning the turbines of the electric generators.
