thermal neutrons


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thermal neutrons

pl n
(Nuclear Physics) slow neutrons that are approximately in thermal equilibrium with a moderator. They have a distribution of speeds similar to that of the molecules of a gas at the temperature of the moderator. Data concerning nuclear interactions are often given for standard thermal neutrons of speed 2200 metres per second, which is approximately the most probable speed at normal laboratory temperatures
Translations
neutrons thermiques
References in periodicals archive ?
Such neutrons in nuclear physics are called <<delayed>>, which play an important role in the management of nuclear chain reactions in nuclear power plant reactors operating on thermal neutrons. For a stable course of the nuclear chain reaction in the uranium isotope [sub.92][sup.235]U, impurities that absorb neutrons should be absent in it, and a minimum amount of a nuclear substance called the critical mass should be present [1, 3].
In addition, if the purpose is to detect neutrons, materials composed of light elements are used, and [sup.6]Li or [sup.10]B should be included in the matrix, since these elements have a high cross-section to thermal neutrons. In the case of charged-particle detectors, materials with intermediate [Z.sub.eff] are preferred because there are many background photons and neutrons in the measurement environment of charged particles.
Contract award notice: Supply contract regarding the purchase of 3He filled proportional counters (for thermal neutrons) based on recovery and purification of gas from spare 3He counter tubes
The thermal neutron absorbers, even in screens of small thickness (e.g., 0.1 cm), can cause significant cutoff of the thermal neutrons' component in the neutron energy spectrum.
The neutron diffraction measurements were performed at room temperature in the 2-axis 'PSD' monochromatic neutron diffractometer ([[lambda].sub.0]=1.068 [Angstrom]; Q=0.45-9.8 [[Angstrom].sup.- 1]) [22] at the 10 MW Budapest Research Reactor, using thermal neutrons. The powder specimens (~3 g/each) were filled in cylindrical vanadium sample holder of 8 mm diameter.
Neutron capture therapy (NCT) is a well-known approach to cancer treatment based on the accumulation of neutron capture agents at the tumor site [1], followed by irradiation with thermal neutrons. NCT is a very effective technique for cancer treatment because the thermal neutrons with low energy do not cause damage to normal cells that lack the neutron capture compounds.
Gamma-ray yields were calculated for 517, 788, 1165, 1951, 2863, 6110, 6619, and 8578 keV chlorine prompt gamma rays produced due to capture of thermal neutrons in chlorine.
Detectors with the isotope [sup.6]Li have a high value of cross section for reaction with thermal neutrons via the [sup.6]Li(n, [alpha])[sup.3]H reaction, while detectors with [sup.7]Li are practically insensitive to neutrons in that range of energy.
The expressions obtained for the spectra of moderate neutrons allow reinterpreting the physical nature of the processes that determine the form of the neutron spectra in the region of the thermal neutrons. The influence of the behavior of the cross sections for the elastic scattering of neutrons on the formation of a neutron moderation spectrum maximum in the low-energy part of the spectrum was established.
In response, the relatively inexpensive, compact neutron generator, married to an optimally designed moderator, becomes valuable in a host of new applications using high-flux thermal neutrons and high-yield fast neutrons.
As the main focus of the ESS facility is providing cold and thermal neutrons, it is essential when altering the baseline design to monitor the performance impact on the cold/thermal neutrons available in the instruments beamlines.
BNCT treatment produces radiation inside a tumor using boron-10 and thermal neutrons. Boron-10 is introduced into cancer cells with the help of phenylalanine, a special carrier substance.