0
Basically a chain reaction (nuclear or chemical) is a self sustaining auto-catalytic reaction.
In a nuclear reactor it is a neutron chain reaction, where each neutron released in every fission event can trigger another fission event. In a nuclear reactor the excess neutrons must be disposed of, which is the purpose of the control rods so that the reaction can be kept at some desired constant rate.
Wiki User
∙ 9y ago
Add your answer:
Earn +20 pts
What is meant by nuclear reaction at very temperature?
there is no end-scale "highest" temperature, to put this in easy terms : the bigger the bang the higher the temperature, to answer the Question: the highest temperature would probably be the temperature created when the big-bang occurred.
What can happen when a fission chain reaction gets out of control?
A chain reaction has products or byproducts that cause the reaction to continue. One example is a state of nuclear critical mass, in which an atom of u-235 decays to produce fast neutrons (along with other fission fragments), which crash into other u-235 atoms, which release more neutrons. The number of neutrons in the environment increases, and if this is not controlled, then there is a nuclear explosion. That is how an atomic bomb works. Another example is a state of instability in snow on a mountain side. If snow begins to move at the top of the mountain, it pushes the snow below it to give way, this pushes the snow below it to give way in turn, going down the mountainside until the snow runs out or the mountain levels out. This is an avalanche. Another example is a situation where the electric grid is overloaded to the point of instability. A failure in a transformer can cause a power surge that causes another failure, this causes other power surges in other places, resulting in other failures. This produces widespread power outage. Chain reactions continue until some sort of equilibrium is attained, or until the unstable features of the situation have lost their energy. In human terms, the results are often destructive or at least dangerous.
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.
What is artificial radioactivity?
Not all nuclear reactions are spontaneous. These reactions occur when stable isotopes are bombarded with particles such as neutrons. This method of inducing a nuclear reaction to proceed is termed artificial radioactivity. This meant new nuclear reactions, which wouldn't have been viewed spontaneously, could now be observed. Since about 1940, a set of new elements with atomic numbers over 92 (the atomic number of the heaviest naturally occurring element, Uranium) have been artificially made. They are called the transuranium elements.
What is meant by the rate of reaction?
The how much speed it takes for two substances to make one product. Many factors can affect this including the temperature, the surface area, the concentration, the catalyst and the pressure (only applies for gases)
What is meant by nuclear reactor?
It is a device where a controlled nuclear fission chain reaction occurs.
Functions of nuclear reactors?
One of the primary functions of a nuclear reactor is to maintain a chain reaction. Also, nuclear reactors are meant to provide a steady flow of neutrons.
How is energy lost in a nuclear reactor?
how am i meant to know you
What is meant by supercritical and how does it relate to making a nuclear bomb?
A subcritical mass cannot sustain a nuclear chain reaction, it dies exponentiallyA critical mass can sustain a nuclear chain reaction, but it remains constant neither increasing nor decreasingA supercritical mass not only sustains a nuclear chain reaction but it increases exponentially until the mass explodesA nuclear fission bomb must become supercritical at some time in order to explode.
What are nuclear leaks?
By "nuclear leaks" is meant the leakage of radioactive material from a nuclear facility such as a nuclear reactor or a store of spent fuel. This would only happen if the fuel had been damaged and the zircaloy sheathing was leaking, and also the contents of the reactor or store were leaking into the atmosphere. The leaked material could be gaseous like iodine, or could be particulate.
What is meant by reactor grade materials?
This means that the nuclear material is of a high enough concentration to fissile (allow for a fission chain reaction). This is because Uranium comes naturally as 99.3% U238, which cannot sustain fission, and .7% U235, which is what they want for the fuel. So they have to find away to pull away the U238 and leave the U235. As they concentrate the U235, it becomes concentrated enough so that it can sustain fission (too much U238 bogs down the reaction and will eventually end the fission). When it reaches this point of concentration, it is concidered reactor grade. Different elements have different needed concentrations to reach this level.
What is meant by supercritical andhow dose it relate to making a nuclear bomb?
subcritical - a mass or arrangement of fissionable or fissile material unable to sustain a neutron chain reaction. It can provide a fixed amount of neutron multiplication from a neutron source, but after removal of the neutron source the chain reaction rate drops exponentially.critical - a mass or arrangement of fissionable or fissile material capable of sustaining a constant neutron chain reaction. No increase or decrease. (Nuclear reactors operate at critical)supercritical - a mass or arrangement of fissionable or fissile material capable of not only sustaining a neutron chain reaction, but once initiated the chain reaction rate rises exponentially. (Nuclear fission bombs explode when made supercritical)A nuclear fission bomb must have 2 of these states: subcritical (so that it can't explode until desired) and supercritical (so that it explodes with an effective yield). This requires a rapid "assembly" system using conventional explosives to rearrange the fissile material from subcritical to supercritical in about 1ms. A neutron source starts the chain reaction and the explosion completes in about 1 microsecond.
What is meant by the term biomass?
Biomass is from an ecosystem which can cause a nuclear reaction otherwise known as a nuke in MW2
What is meant by drum foundation which is used for supporting reactor turbines?
hvfv
What is meant by light reaction of photosynthesis or light phrase of photosynthesis?
The biochemical reactions involving photolysis of water comes under light reaction. It is infect a chain of reactions commonly known as light phase.
What is meant by nuclear reaction at very temperature?
there is no end-scale "highest" temperature, to put this in easy terms : the bigger the bang the higher the temperature, to answer the Question: the highest temperature would probably be the temperature created when the big-bang occurred.
The differences between nuclear reactors and nuclear bombs include what?
Nuclear reactors produce exactly one additional fission for each fission reaction while nuclear bombs don't Nuclear bombs are runaway fission reactions and reactors aren't (APEX)
