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.
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.
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.
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.