Neutrons have the power to penetrate metals or heavy elements such as calcium, silicon, and iron. Neutrons also have high sensitivity, so they can be used to detect elements such as boron and chlorine. An accelerator-driven, compact neutron system has been developed in RIKEN for practical use on job sites.In this paper, a pixel imaging detector for fast neutrons with energy levels above 1 MeV is developed and used to produce images of an iron rod and air pockets through 30 cm of concrete. Also, the salt concentrations of 4 cm- and 5 cm-thick mortar blocks are measured, and a correlation diagram is obtained for up to 1 kg/m3.
A nondestructive inspection method which is in type using backscattered neutrons to detect void and water in concrete with RIKEN Accelerator-driven Compact Neutron Source (RANS) is developed. In this method, it is not necessary to be interposed the sample between the radiation source and the detector as in the conventional method using neutron transmission. The position of water and void in the concrete are measured from the intensity change of the backscattered neutrons selected from the incident up to 1 ms. This study reveals that it is possible to observe the two dimensional distribution of water or void inside slabs up to 6 cm below the slab surface.
The authors have developed a nondestructive inspection method using backscattered neutrons to detect voids and water in concrete with a RIKEN Accelerator-driven Compact Neutron Source (RANS). In this study, neutrons are emitted to a slab sample that consists of a concrete layer and an asphalt layer, and position distribution of backscattered neutrons are measured at the timing from 0.1 to 0.5 ms. The two-dimensional position of water and voids in the concrete plate under asphalt (5 cm) of the slab sample are detected.
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