Search results
Results from the WOW.Com Content Network
A thermal neutron is a free neutron with a kinetic energy of about 0.025 eV (about 4.0×10 −21 J or 2.4 MJ/kg, hence a speed of 2.19 km/s), which is the energy corresponding to the most probable speed at a temperature of 290 K (17 °C or 62 °F), the mode of the Maxwell–Boltzmann distribution for this temperature, E peak = k T.
Fissile nuclides do not have a 100% chance of undergoing fission on absorption of a neutron. The chance is dependent on the nuclide as well as neutron energy. For low and medium-energy neutrons, the neutron capture cross sections for fission (σ F ), the cross section for neutron capture with emission of a gamma ray (σ γ ), and the percentage ...
The chart of those nuclides is also known as a Segrè chart, after the physicist Emilio Segrè. [3] The Segrè chart may be considered a map of the nuclear valley. The region of proton and neutron combinations outside of the valley of stability is referred to as the sea of instability. [4] [5]
Uranium-235 (235 U or U-235) is an isotope of uranium making up about 0.72% of natural uranium.Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction.
In nuclear engineering, a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties (specifically, its nuclear fission cross-section), density, shape, enrichment, purity, temperature, and
While exposed to the neutron flux during normal operation in the core environment, a small percentage of the 238 U in the fuel absorbs excess neutrons and is transmuted into 239 U. 239 U rapidly decays into 239 Np which in turn rapidly decays into 239 Pu. The small percentage of 239 Pu has a higher neutron cross section than 235 U.
In nuclear physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. The neutron cross section σ can be defined as the area in cm 2 for which the number of neutron-nuclei reactions taking place is equal to the product of the number of incident neutrons that would pass through the area and the number of ...
Toggle Neutron temperature subsection. 13.1 Thermal neutrons. 13.2 Cold neutrons. 13.3 Ultracold neutrons. ... 12–13 For a given mass of fissile material, ...