Research of the effect of water content on the distribution of neutron by using PGNAA for in-situ measurement

Monte Carlo method was used to simulate the physical process of 14 MeV fast neutrons after entering the sediments. The work obtained the neutron spectrums in different depths and the distribution of 0∼1 eV neutrons in sediments, the influence of water contents and concentration of Cl on the distribution was analyzed and the range of maximum depth of 0∼1 eV neutrons diffusion was discussed. The results show that water content has a significant influence on neutron energy spectrums, and the transverse and longitudinal distribution of 0∼1 eV neutrons can also be affected. The optimum depth of neutron activation is 2 cm and the range of maximum depth of 0∼1 eV neutrons diffusion is 20 cm∼40 cm. The concentration of Cl in sea water has influence on neutron absorption, but the influence is not significant. (authors)