The corrosion under insulation (CUI) is the common problem that can be found in the production pipelines of petroleum and petrochemical plants. The reason of occurrence could be from the accumulation of liquid such as rain or even the condensation of product inside the pipelines. This research aims to determine location and to approximate the volume of liquid accumulated though the true scale pipeline model using neutron radiation techniques. The model composed of a metal pipe, diameter 254 mm (10 in.) covered by polyisocyanurate (PIR) thermal insulation. The volume of liquid accumulated under the insulation can be varied, in order to determine the detectability of system. The neutron radiation techniques used in this research are neutron backscattering and neutron transmission. Neutron backscattering was used to determine the location of liquid whereas neutron transmission was used to estimate the volume of the liquid. The Am241-Be neutron source and He-3 neutron detector were fabricated inside single probe and connected to the radiation counter. Results of research indicated that neutron backscattering technique can locate the boundary of accumulated liquid along the circumference of pipe. The transmission technique provided results of measured volume deviated from setting up about 10%.