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Sub Critical
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Describe a characteristic of a fissionable substance that is essential for a chain reaction to sustain itself?
Firstly it must be able to capture neutrons which then have a high probability of causing its nuclei to undergo fission or splitting, and the fissions must produce enough further neutrons so that for every fission that occurs, another one will follow.
Describe a characteristic of a fissionable substance that is essential for a chain-reaction to sustain itself?
The fission process is sustained by neutrons. A neutron entering a nucleus and causing fission must be replaced in order to cause the next fission, and so on. So the fissionable substance must emit more neutrons when fission occurs, and enough of them so that despite some being absorbed by the moderator and some leaking from the reactor boundary, there is still enough to maintain the chain reaction. Uranium 235 emits on average about 2.5 neutrons per fission (you might say what is half a neutron, but this is explained by the fact that fissions have a range of possible results, with different numbers of neutrons emitted, and the average is 2.5).
How are rusting the same as burning?
In some ways. Rusting is an oxidation reaction similar to fire and it does release heat, but it is so slow that the heat does not affect the reaction. In a fire the heat released goes helps sustain the reaction.
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.
How can you sustain coal?
you can't sustain coal. It's gone then it is gone.
What is the quantity of fissionable material called that CANNOT sustain a nuclear reaction?
Sub Critical
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.
Is it true or false that the only isotopes that can be used as fuel in a nuclear power plant are those in which a chain reaction can occur?
True, only fissionable isotopes that produce enough excess neutrons to sustain a chain reaction can be used directly as fuel.However fertile isotopes that capture neutrons and then transmute to fissionable isotopes can be used indirectly as fuel through a process called breeding.
Who was the first person to sustain a fissionable chain reaction?
This was first achieved in the Chicago pile, 1942. Enrico Fermi was the team leader.
Critical mass is the of material required to produce a chain reaction?
minimum amount
Atoms that naturally undergo nuclear fissions are called?
These are called fissile or fissionable. Fissile isotopes undergo fission, producing sufficient neutrons of sufficient power that a chain reaction can happen, if there is enough of the isotope to support it. The mass sufficient to support a chain reaction is called critical. Atoms of fissionable isotopes will undergo fission when a sufficiently energetic neutron collides with them, but the neutrons they emit when they divide are either insufficient in number or insufficient in energy to sustain an chain reaction. There is a third type of material that can undergo fission, called fertile, which is isotopes that can be caused to capture neutrons, changing into fissile or fissionable isotopes, so the fission does not happen to atoms of the fertile material directly, but to the atoms of the isotopes they become.
What is the amount of fissionable material that must be present in order for a nuclear reaction to take place called?
The critical mass. With an amount of U-235 or Pu-239, the smallest critical mass will be a sphere. For a nuclear reactor, it will be the minimum number of fuel assemblies loaded to produce a chain reaction.
What is necessary sustain a nuclear chain reaction?
In a chain reaction, neutrons released during the splitting of an initial nucleus trigger a series of nuclear fissions.
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 is nuclear chain reaction?
A nuclear chain reaction is one in which the disintegration of one nucleus creates a cascade of nucleons which, in their turn, cause the disintegration of other nuclei and thus the process can sustain itself.
What is the amount of radioactive material needed to sustain a chain reaction in order to provide useful energy?
The critical mass.
Is A working nuclear reactor is a very simple energy conversion device?
No, its not simple. It requires a sophisticated balance of temperature, pressure, and moderation in order to sustain a critical nuclear fission reaction.
