Survey and design of an irradiation setup for measuring the amount of heavy water in a sample

An irradiation system, which works based on photodisintegration reaction of deuterium, has been evaluated for determination of heavy water in water samples. This irradiation system was designed by simulation with MCNPX code, considering some gamma point-like sources placed in the center of sample, and then counting the created neutrons by the long cylindrical BF3 counter. For increasing the neutron counting efficiency, an optimization was performed for thickness of various moderators considered between the sample and thermal detector. To investigate the practical effectiveness of the designed system, a model apparatus was built for routine use in measurement of a wide range of heavy water concentrations. It was successfully applied for weight percentages larger than 0.5 % to observe the acceptable detection sensitivity of D2O with an error less than 0.24 %. (author)