Design and fabrication of an in situ gamma radioactivity measurement system for marine environment and its calibration with Monte Carlo method

Simulation, design and fabrication of a sealing enclosure is carried out for a NaI(Tl) 2″×2″ detector, to be used as in situ gamma radioactivity measurement system in marine environment. Effect of sealing enclosure on performance of the system in laboratory and marine environment (distinct tank with 10 m³ volume) were studied using point sources. The marine volumetric efficiency for radiation with 1461 keV energy (from ⁴⁰K) is measured with KCl volumetric liquid source diluted in distinct tank. The experimental and simulated efficiency values agreed well. Marine volumetric efficiency calibration curve is calculated for 60 keV to 1461 keV energy with Monte Carlo method. This curve indicates that efficiency increasing rapidly up to 140.5 keV but then drops exponentially. - Highlights: • Simulation, designing and making of sealing enclosure for a NaI(Tl) 2″×2″ to use 100 m water depth. • Various experimental tests with and without enclosure by point sources. • Carrying out the system in lab water environment with 10 m³ volume and repeat the same tests. • Measurement of the efficiency for designed system by KCl volumetric liquid source and comparison with the simulation results. • Marine volumetric efficiency calibration based on the simulation results.