Response function calculation of an underwater gamma ray NaI(Tl) spectrometer

Autonomous measuring systems for radioactivity in the water environment require caution concerning the specifications of power consumption, stability, communication equipment, tolerance and efficiency. In addition, the calculation of the response function of the whole system is essential for suppressing the background of the measurement and for estimating the concentration of the involved radionuclides, especially given the greater probability of primary gamma photons undergoing multiple scattering events before they interact with the sensing device. In this work, a method is presented that can be used to calculate the response function of a NaI(Tl)-based spectrometer when it is used in the marine environment. The method takes into account both the scattering of photons in the water (analytical calculations) and the detection mechanism of the sensor (Monte-Carlo simulation). In order to validate the method, the calculated response function has been used in a real measuring system in order to estimate the concentration of 40K and thus the salinity of the water.