k. sepanloo

This study examines the various uncertainties in the fire probabilistic risk assessment method based on the NUREG/CR-6850 guidelines. Core damage frequency (CDF) was calculated for a fire scenario in the switchgear room of a PWR nuclear power plant. By incorporating uncertainties in all computational quantities, a unified approach takes to assess the final CDF for this fire scenario. First, the distribution of each parameter of the CDF calculation relationship determined. Then, by using the Monte Carlo sampling method, the final distribution for the CDF calculated. The results indicate that uncertainties integration have a significant impact, and generalization this topic in calculating the final CDF could lead to a more realistic risk assessment. In case of generalization of this calculation method in all assumed fire scenarios in the reactor, it expects that more accurate information on the fire risk amount and its contribution amount in total CDF will obtain and resources will spent more intelligently.

In this research, utilization of typical moisture separation process in conventional steam cycle power plants, for NPPs are recommended; and by applying CFD, two-phase flow of this process is simulated. Results show that with increasing of loading, the pressure drop across the separator increases, and a linear relationship between pressure drop and inlet flow kinetic energy density is established. Also, with increasing inlet width, pressure drop decreases and the efficiency increases. However, excessive increasing of input width leads to a decrease in mass flow at lateral outputs. Study on the variation of lateral outlet diameter show that variation of mentioned parameter does not affect pressure drop and efficiency significantly, but reducing of that lead to increasing lateral out let steam mass fraction. Based on the performed assessment, horizontal steam separator as a component with desirable efficiency and pressure drop, can be recognized as a suitable option for utilization in small and low power NPPs as well as propulsion systems. For validation, an analysis of two phase flow in a vertical cylinder cyclone is performed and results show good agreement with experimental data.

This study aimed to produce a personal dosimeter to connect the electronic devices to transfer the dosimetry data online including dose rate data and integral dose. At first, an electronic board was designed. Afterwards, the board was simulated using Altium Designer software. Then, the microcontroller programming was performed using Code Vision software. The performance of the elements was tested using Proteus Design Suite software and the circuit diagnosis and testing were practically implemented. Afterwards, the calibration factor and the count-to-dose conversion coefficient were obtained using an ionization chamber in the Secondary Standard Dosimetry Laboratory of Iran. Furthermore, dose distribution as a function of distance to the source, was obtained using the produced dosimeter and was compared using a calibrated ionization chamber. To this purpose, an unmitigated Cs-137 source, a Cs-137 source with a 22 mm Pb shield, and a Cs-137 source with a 22 mm plus 18 mm shield were used. The results showed a calibration factor of 0.99 ± 0.02 for the designed dosimeter. Calibration results showed that the produced dosimeter passed the ISO/IEC 17025:2005 criteria. Furthermore, the dose distribution results demonstrated negligible differences of less than 0.01% between the produced dosimeter and the reference ionization chamber. It was concluded that the produced dosimeter could be used as a reference and standard dosimeter in laboratories, for monitoring and dosimetry of ionizing photon radiations.