Sharif Digital Repository

During the operation of a nuclear power plant, the reactor pressure vessel (RPV) is exposed to a variety of pressure and thermal stresses and neutron radiations. This will cause the loss of the initial strength of the reactor vessel component. During the occurrence of some of accidents, an excessive cooling of the coolant inside the RPV takes place which in the term is called overcooling transients. In addition, in some of these events, a break in a section of the circuit will reduce the water level at the core of the reactor. By reducing the water level, the existing emergency makeup water systems are activated and inject water into the reactor. The temperature of the added water is much... 

Two-phase flows are widely used in petrochemical industry, chemical processes, boilers, nuclear reactors, cooling systems and air conditioning equipment. Since the problem of earth’s ozone layer and global warming, the analysis of flow characteristics in evaporators are necessary to improve performance of refrigerating systems and saving the environment. Most of the researchers have been studied the evaporation of two phase flow refrigerant through experimental studies and numerical analysis has less attention in the literature. In this Thesis, a mathematical model based on the two-phase separated flow model is developed to simulate the evaporation of pure refrigerant under constant heat... 

The internal combustion engine power is determined by the amount of fuel effectively burned inside the engine cylinders. On the other hand, the fuel consumption is proportional to the air mass that enters the cylinders in each cycle. Conventionally, incoming the engine inlet air is at ambient conditions. However, with higher air density, the engine power increases for the same dimensions, so-called turbocharging. Although the engine's structure remains unchanged, it may be necessary to adjust the main systems of the engine simultaneously. This research investigated maximizing the power of a turbocharged diesel engine based on upgrading the degree of turbocharging. For this purpose, the EM355... 

Pipeline transfer is the most commonly method for natural gas transportation. Potential force of natural gas transportation in pipeline is pressure difference that is generated in Gas Compressor Stations (GCS). For each 100 to 150 km of pipeline, one GCS is required that pressure is increased usually from 700 to 1000 psig. Each station contains different process equipments such as turbines, compressors, scrubbers, filters, air coolers, throttling valves and pipes with instruments. It is shown that about 10 percent of the generated pressure difference, decays in GCS.
In this thesis, pressure losses are studied and initiatives are purposed to reduce them in a Gas Compressor Station. Then... 

In this thesis to simulate the behavior of liquid engine Thrust chamber of hot gas from a quasi one dimensional code used when the effects of the heat transfer and friction in those terma. As well as during the regenerative channel is simulated by considering the equation’s of continuity, momentum and energy for one dimensional, effects of increase temperature, pressure drop, change the density of coolant flow resulting from the warming which is visible along the way to increase the accuracy of calculation of the thermal flux output of the engine, use a suitable model for unclear boiling in consideration of heat transfer coefficient used coolant flow it has been. As well as coupling of heat... 

In this survey the TTL-1 thermal hydraulic test loop in Nuclear Science and Technology Research Institute (NSTRI) has been modified to study thermal hydraulic phenomenon in research reactor thermal condition. These modifications include: replacing the test section containing a single heating rod by a group of 31 rods in a triangular array, relocating the pressurizer from the cold leg to the hot leg and improving piping of the test loop. In order to measure the time dependant flowrate of the coolant, a rotameter flowmeter is added. Three level meter measure the water level in pressurizer, test section and the primary loop drain tank and a 3-phase AC inverter controls the rotational speed of... 

In this study, the determination of the distribution and the differences concentration of hydrogen in containment of Bushehr power plant by modeling of containment and Hydrogen removal system of Bushehr power plant during LB-LOCA accident is accomplished. In Bushehr nuclear power plant, which has a unique design, the containment is similar to PWR power plants with a metal sphere, but the installed reactor is a VVER-1000. After a full study on the containment and its systems, the required data for modeling is gathered and afterwards, the engineering handbook is prepared for MELCOR input code and then the modeling and size classification of the containment is done in 4 different ways,... 

In this work the large break loss of coolant accident at Boushehr Nuclear Power Plant (NPP) has been studied. At first, primary and secondary side’s components which play important role in the accident have been modeled using RELAP5/MOD3.2 GAMMA system code. The components are: reactor pressure vessel, main pipe lines, main coolant pumps, pressurizer, steam generators, steam lines, emergency core cooling accumulators, boron solution supply tanks and pumps (LP& HP) and KWU accumulators. After preparing the input file and running the code, thermal hydraulic properties such as radial distribution of temperature in fuel rods, temperature distribution in steam generator primary and secondary... 

The capability of Bushehr nuclear power plant spray system to reduce fission product and control a specified severe accident has been investigated in this study. In order to evaluate spray system in one of the worst cases for containment, we have chosen Large Break Loss of Coolant Accident (LB-LOCA) without access to active part of ECCS system. We have only simulated containment, so the leakage of various materials from core and primary circuit of nuclear power plant are considered as the boundary conditions for simulation. Following the Fukushima accident in 2011, many nuclear safety legislative groups concentrated on using mobile equipment which is essential for nuclear power plants these...