Simulation study on detection efficiency of gamma spectrum for water sample

In nuclear emergencies, gamma spectrum analysis is a rapid and effective method to acquire information of radio-nuclides and their concentration of environmental samples, as water, air, soil and foodstuffs, which can play an important data-support function in decision-making for radiation protection, assessment of accident consequence and remedy of radiological contaminated environment. By making use of MCNP4C, this paper calculates full-energy efficiency of gamma rays with energy of 0.662 keV in water samples under different measuring conditions as: standard detector of Nal (Tl) scintillator with standard sample box, standard detector of Nal (Tl) scintillator with Marinelli beaker, and well-shaped Nal (Tl) scintillator with standard sample box. The simulated results indicates that by using of well-shaped Nal (Tl) scintillator, full energy efficiency of gamma ray with energy of 0.662 keV in water sample can reach to 22.9%, 7 times higher than the efficiency of standard Nal (Tl) scintillation detector with standard sample box. (authors)