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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.
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.
Why U 235 is fissioned by thermal neutron while U 238 by a fast neutron?
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
Is a control rod in nuclear reactor a hollow tube?
Varies. A hollow control rod can act as a "neutron trap." The moderator in the hollow center helps slow the fast neutrons into the thermal region for increased absorption by the surrounding absorbing material such as Boron.
What are free and thermal neutrons?
A free neutron is any neutron not bound into an atomic nucleus. A thermal neutron is a free neutron having about the same kinetic energy as the thermal vibrations of atoms at ordinary temperatures, roughly under 2eV (0.025eV at room temperature).
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.
What is the difference between fast and slow neutrons?
The difference between fast and slow neutrons is in the amount of energy they possess. Fast neutrons tend to "blow through" the nucleus of some isotopes. This causes a disruption but, because they don't stay around, the nucleus restabilizes. Slow, or thermal, neutrons, however, may get absorbed by the same nucleus, which then destabilizes, causing fission. It should be pointed out that nuclei of different isotopes are affected differently by neutrons. 238U is caused to divide more frequently by a faster neutron, while 235U is caused to divide more frequently by thermal (slower) neutrons, and 233U is caused to divide more or less equally by any.
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 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.
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 is the effect of slow neutron on nuclear reactions?
Because of neutron multiplication ratio.....
