Development and optimization of an underwater in-situ cerium bromide spectrometer for radioactivity measurements in the aquatic environment.

ABSTRACT

A new medium resolution gamma-ray spectrometer consisting of a cerium bromide (CeBr3) crystal (2˝ x 2˝), is developed and optimized for radioactivity measurements in aquatic environments. This apparatus named GeoMAREA (Gamma-ray spectrometer for in-situ Marine Environmental Applications) is designed to control and prevent radio-contaminants in aquatic environments as well as to estimate the variation of natural radionuclides in marine systems for studying oceanographic processes. The system offers activity concentrations in Bq/m3 for detected gamma-ray emitters in the energy range from 150 to 2600 keV, and can provide sequential continuous monitoring data in a stand-alone mode or it can be integrated in stationary/mobile platforms for (near) real-time applications. The photopeak efficiency values were estimated via the MCNPΧ code. Two experimental points were used to validate the theoretical estimations by deploying the system in a water tank with diluted reference sources such us Caesium-137 (137Cs) and Potassium-40 (40K). The system was subsequently deployed in the field along with a conductivity-temperature (CT) sensor, to measure 40K and radon daughters in a region where submarine groundwater discharges (Anavalos, Kiveri, Greece) are present. The experimental calibration data was utilized to provide a first estimation for the background contribution around the photopeak of 40K, attributed to the Cerium Bromide (CeBr3) intrinsic activity.