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Because slow neutrons are the most efficient way to cause U235 to fission. The U235 nucleus is said to have a large cross section for the capture of slow neutrons, much larger than for fast neutrons.
Wiki User
∙ 15y ago
Wiki User
∙ 11y agoIf the question is how are nuetrons seperated in the first place, then it is due to an imbalence in the nucleas causing fission where as (depending on circumstances and decay type) fire off a nuetron, or the substance absorbs it and ballences itself accordingly- beta, gamma, positron e.c.t.
If the question is how to slow it once released then it is like that of a moderator in a nuclear reactor/ by having it continuously 'hit' other (ushally smaller yet sodium, graphite and heavy water are common) nuclei it slows its kenetic energy, ushally to about 1 EV/ 2 kms^(-1) depending on size (gazillions of variabilitys but you get the gist).
Source: Physics Student.
Wiki User
∙ 11y agoThe crosssection for neutron capture by uranium-238 is very high for fast neutrons but low for slow neutrons. Each neutron captured by uranium-238 is one less to fission uranium-235.
A reactor can work on fast neutrons, but then it needs most of the uranium-238 removed. That means it has to use weapons grade uranium.
Wiki User
∙ 13y agoBreeder reactors do use fast neutrons, but they have no moderator and must use highly enriched uranium ( > 20% Uranium-235).
Also bombs use fast neutrons.
Wiki User
∙ 13y agoNeutrons are small, and fast, they split the nucleus of the atom, therefore releasing massive amounts of energy.
Wiki User
∙ 10y agoOnly neutron is used for nuclear fission because neutrons are neutrally charged particles and hence can hit the positively charged nuclei more conveniently.
Wiki User
∙ 11y agodifferent properties of the isotopes.
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How is the neutron yield of an AmBe neutron source facility increased?
Fission
What is the bullet that starts a fission reaction?
A neutron.
Do nuclear bombs use nuclear fusion or fission?
Almost all modern nuclear explosive devices use some of each. The early atomic bombs used only fission. All hydrogen bombs use both fission and fusion. Some things you might want to look up are: boosted fission bomb, external electrical fusor neutron source, the plutonium "fission sparkplug" used in each stage of a hydrogen bomb, depleted uranium hydrogen bomb tamper can provide up to 90% of the total yield through fast fission.
What is the particle required to continue the chain process of Uranium fission?
The neutron
Element used in fission?
Usually uranium with various U-235 percentages.
Fast neutron detection by helium 3 ionization chamber?
Helium-3 has a high cross section for thermal neutron absorption. For fast neutrons you must either thermalize the neutrons for use with boron or helium-3 based proportional counters or use a fast fission chamber based on fast fission of uranium. It's worth noting that a uranium based fast fission detector is really only useful in extraordinarily high neutron fluxes like that of a reactor.
Why you use slow neutrons instead of fast neutrons in nuclear reaction?
in reacter U-235 fission is due to slow neutrons because in reacter the probability of fission from fast neutron is approximatly zero.
Why fission cannot take place with fast neutron?
In order to cause an atomic nucleus to become unstable so that it will undergo fission, you have to add a neutron. If a slow neutron collides with an atomic nucleus, it will be absorbed into the nucleus and become part of it. The nuclear attraction of the nucleus is strong enough to grab a slow neutron. But a fast neutron cannot be captured because it has too much kinetic energy. The attraction of the nucleus is not enough to stop the motion of a fast neutron. Even if a fast neutron makes a direct hit on an atomic nucleus, it is just going to bounce off.
In a nuclear fission reaction a freely moving neutron?
In a nuclear fission reaction, a freely moving neutron undergoes neutron capture and initiates the nuclear fission of a fuel atom.
What does thermal indicates in thermal neutrons?
A thermal neutron has much less energy / velocity than a fast neutron. As a result, it has a much larger neutron absorption cross section, making it easier for it to be absorbed by certain nuclei and subsequently initiate fission. The fast neutrons that result from fission are slowed down, i.e. moderated, usually by water, in order to become thermal neutrons and to sustain the fission chain reaction.
How is the neutron yield of an AmBe neutron source facility increased?
Fission
What is the bullet that starts a fission reaction?
A neutron.
What has the author John Gary Owen written?
John Gary Owen has written: 'The calibration and use of a helium-3 spectrometer to measure delayed neutron spectra following neutron-induced fission of uranium-235 at several fission energies'
Do nuclear bombs use nuclear fusion or fission?
Almost all modern nuclear explosive devices use some of each. The early atomic bombs used only fission. All hydrogen bombs use both fission and fusion. Some things you might want to look up are: boosted fission bomb, external electrical fusor neutron source, the plutonium "fission sparkplug" used in each stage of a hydrogen bomb, depleted uranium hydrogen bomb tamper can provide up to 90% of the total yield through fast fission.
What helps control the fission reaction in a nuclear plant?
The fission reaction is controlled through use of high neutron capture material as Boron, Gadolinium, Cadmium, ... etc.
A neutron is an unstable particle outside a nucleus but to start nuclear fission requires the slowing down of a neutron. How is nuclear fusion carried out in the case of uranium?
The neutrons released from Uranium are fast neutrons. In a reactor they are slowed down by a moderator. The moderator could be water, heavy water, graphite, among others. When the neutron is slowed down, it is more likely to create fission.This is what happens with the U-235. The U-238 does not fission, but it does transmute through a series of neutron absorption and beta decay etc. into plutonium which does fission also.
What is a neutron trigger used for?
Atomic nuclear fission.
