Prompt gamma-rays in three H-rich moderators exposed to neutrons.

Monte Carlo methods, with the MCNP5 code, were used to estimate the pulse-height spectra of γ-rays induced in three hydrogen-rich moderators modeled as 20.32 cm-diameter spheres made of water, polyethylene and gasoline. The source-term was a point-like 241AmBe neutron source. The pulse-height spectra were estimated as measured with a NaI(Tl) scintillator and as measured by a detector without the low-resolution limitation. In the moderators the induced γ-rays are produced in 1H(n, γ)2H reactions; also another two gamma rays are scarcely produced in 12C(n, n'γ)12C and 16O(n, n'γ)16O inelastic scattering reactions. For the case of polyethylene moderator the pulse-height spectrum was measured with a gamma-rays spectrometer with a 3" Ø × 3" NaI(Tl) scintillator and compared with the calculated spectrum, where is shown that the 4.44 MeV photon is produced by the neutron source. • The PHS of neutron-induced γ-rays were calculated using MC methods. • Moderators are water, polyethylene and gasoline. • The poor-resolution spectra show the 2.22 MeV due the 1H(n, γ)2H reaction. • The spectra show the induced γ-rays due to inelastic scattering in 12C and 16O. • Experimental validation was carried out for polyethylene. [ABSTRACT FROM AUTHOR]