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It's to do with the capture cross-section of the nucleus. It just happens that the U-235 nucleus has a much larger cross-section for neutron capture when the neutrons are slow, and that the subsequent nucleus is unstable and splits into two parts. With U-238, it does not undergo fission at all, it just absorbs the fast neutron and transmutes to Pu-239.
As to the fundamental reason for this, it is in the complex nuclear physics field of study
What else can I help you with?
How does the atmosphere keep oxygen inside?
Inside what? Oxygen is part of the atmosphere. The thermal velocity of its molecules are insufficient to escape earth's gravity (unlike hydrogen molecules which are fast enough).
Explanation of fast neutron and slow neutron in nuclear reaction?
Free neutrons are said to have a speed or a temperature. Both ideas mean pretty much the same thing, which is that they have an amount of energy associated with them. It is specifically measured most commonly, perhaps, in electron volts (eV), or as Million electron volts (MeV). Unfortunately, what is meant by fast or slow depends on the application, and perhaps the author or speaker. Free neutrons come from different sources and have different speeds when they are produced. As they fly about, they hit the nuclei of atoms, and may bounce, imparting some part of their energy to the atoms if they do. As time passes, they lose energy in this manner getting slower and slower. Please note, however, that not much time usually passes, because the half life of a neutron is a bit less than fifteen minutes. There are other things that neutrons can do besides bounce. They can cause decay of a radioactive atom, they can cause fission of a fissionable atom, and they can be absorbed. There is a likelihood of any of these events happening by the collision of a neutron with an atom, and the likelihood depends on several things. Of great importance is the isotope of the atom; different isotopes have different cross sections, the cross section being a measurement of how likely it is for the neutron to interact with the atom. Also very important is the temperature of the atom, and the speed of the neutron. The cross section of the atom will be greater or less depending on the speed of the neutron and the temperature of the atom, but not in a way that is easily predictable. A faster neutron might not cause fission as easily as a slower one in a given situation. The data on the nuclear cross sections of atoms by isotope, temperature, and neutron speed, were largely obtained empirically.
What is the least known fact about the earth?
How fast a person is moving, while standing still, on the surface of the Earth.
How fast is silver?
Silver the Hedgehog is pretty dang fast, but no where near as fast as Sonic
Is the rival ghost data same as the expert staff ghost data?
no, your rival ghost is the one that you did not make, but came with the game. its the first ghost you try to beat while the fast staff is the second.
Are there more fast breeder or thermal nuclear reactors?
Most nuclear reactors are thermal-neutron reactors. A few fast breeder reactors have been built, but not many.
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.
What do neutron stars emit?
If a neutron star's rotational period is fast enough to produce jets (A pulsar), said jets will emit radio waves, with faster periods emitting higher frequency radiation as well as the jets themselves emitting synchrotron radiation. Also, unless the neutron star were 0K, it will emit thermal radiation However, as far as a neutron star that isn't a pulsar, nobody knows if they emit anything but thermal radiation.
What will happen if fast-moving neutron strikes with uranium?
When U-238 absorbs a fast neutron it forms plutonium-239
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.
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.
What are the characteristics and applications of fast neutron energy?
Fast neutron energy is characterized by high kinetic energy levels, making them effective for inducing nuclear reactions. These reactions can be utilized in nuclear power generation, nuclear weapons, and neutron imaging techniques. Fast neutron reactors can also help reduce nuclear waste and increase fuel efficiency in the nuclear industry.
Name the element when uranium captures a fast neutron?
The element is determined by the number of protons. When uranium captures a fast neutron it is still uranium but has an increased atomic mass. Fast neutron capture may encourage a further reaction but it depends on which uranium isotope you start with as to the increase in probability some further reaction will occur and which reaction that might be.
Why is the moderator important in a nuclear reactor?
The moderator is used to slow down the neutrons present in the core of the reactor. Normally the neutrons produced as the nuclear fuel (e.g. uranium) is fissioned are travelling too fast to produce a sustained chain reaction. Some examples of moderators are cadmium, heavy water and graphite.
Is uranium 238 a slow or fast neutron absorber?
uranium 238 is a fast neutron absorber the answer is correct but for more explanation:- when uranium 238 is bombard by neutron >>> uranium 238 , undergoes B decay>>>Np 239 ,undergoes B decay >>> Pu 239 finally undergoes alpha decay >>> fissile U
What releases a fast moving electron from a neutron in the nucleus?
Beta decay releases a fast-moving electron (beta particle) from a neutron in the nucleus. During beta decay, a neutron is converted into a proton, and the electron and an antineutrino are emitted to conserve charge and energy.
Thermal conductivity is the ability of an element to transfer what?
Thermal conductivity is the ability of an element to transfer heat. It quantifies how fast heat can be transferred through a material under a temperature gradient. Materials with high thermal conductivity can transfer heat quickly, while materials with low thermal conductivity transfer heat more slowly.
