Designing of an online system for radiocaesium measurements in the marine environment

An online radiocaesium measuring system (ORMS) is designed to determine the environmental radiocaesium contamination of sea water near the Bushehr Nuclear Power Plant (BNPP). The System consists of a 400-liter, spherical stainless steel water tank, including three aluminum (0.5 mm) enclosure NaI (TI) detectors, which each are located in 120° phase angle with size (6×3 in.) to confirm each other. Responses of detectors to gamma radiations were calculated, using Monte Carlo code MCNP.4C. Moreover, delay time of each response and the dead time of the whole system to be considered due to designing decisions were calculated.