In situ gamma radiometry of river bottom based on natural radioactivity measurements

Naturally occurring radioactive material (NORM) mapping at the bottom of rivers or seas is important for the environment, health, industry, and regulatory. NORM mapping procedure under the river bottom is complicated due to several technological, logistical, and environmental challenges. NORM mapping process normally carried out by taking samples from the location and analyzing it in the laboratory and hence it is time consuming especially if a large area is required to be scanned. This paper presents an efficient system for fast in situ mapping of NORM mapping under the river bottom. The system consists of a waterproof (NaI(Tl)) scintillation detector designed to immerge under water with a mechanical system to ensure that it is located on the surface under water. The detector is connected to Data Acquisition System (DAS) on the boat through waterproof coaxial cable. Globalization Positioning System (GPS) is used for determining the location of measurement. System Software provides a fast-mapping Gamma count rates in real time. The system has been tested at Rosetta branch of the river Nile in Egypt. The practical experiments, two navigations have been carried out with different boat speeds (2 km/h and 6 km/h). The measured data has been visualized and analyzed in situ and proved the efficiency of hardware and software. In addition, the obtained measurements show the different concentrations of NORM in the bottom of the river. The results indicate that the NORM is increased when moving toward the Mediterranean Sea direction which reflects that the composition of the soil material is changed at the intersection of the river Nile with the sea. The results also show that the longer sampling times allow more gamma counts to be recorded, the optimal scanning speed depends on the activity level of the source, the detector's sensitivity, and the objective of the NORM mapping.