Performance comparison of 2.8 MeV and 241Am-Be neutrons based moisture measurement setups

Compact shielding design of a portable 241Am-Be source

A compact shielding tank for portable ²⁴¹Am-Be neutron source, which is used in nuclear well logging, was designed according to the Monte Carlo simulation. From inner to outer, the proposed tank has two shielding layers to shield the high- and low-energy neutrons. In this study, the shielding properties of several materials were evaluated. Tungsten was selected as the neutron moderator to build the inner layer. The thermal neutron absorber in the outer layer was made of polyethylene containing 1.2% boron carbide. The volume and weight of the new tank reduced by 86% and 54%, respectively, by using this dual-layer shielding model, when compared with those of the old shielding tank. Moreover, the simulation results indicated that the total dose rate anywhere outside the tank is less than 0.025mSv/h and that the intensity of gamma flux at the tank surface becomes lower.

Experimental determination of moisture distributions in fired clay brick using a 252Cf source: a neutron transmission study

A neutron transmission method was proposed to study liquid transport in porous media. It was applied to study water penetration into two kinds of fired clay bricks. The results showed that the diffusion processes in the investigated samples are different. Water diffusivities and capillary absorption coefficients characterizing both the flow process and the brick samples were determined and compared. The proposed method is simple, accurate and reliable in studying water diffusion in porous media, in real time.