2D and 3D numerical models of a Steam generator for VVER-1000 type nuclear reactors used in the nuclear industry is presented. For the calculation Euler-Euler approach is applied for modeling the boiling heat transfer, boiling and recondensation. In the 3D model, the secondary side of the Steam generator is simulated by the porosity model presented earlier by Stosic and Stevanovic. In the Porosity model, the tubes of the primary circuit are not described in detail, but they are modeled as sources of enthalpy and pressure loss. The physical models were implemented by user-defined programs in ANSYS-CFX12.1 computational fluid dynamics software. The results of the 3D thermal-hydraulic modeling of the Steam generator in the Russian type VVER-1000 NPP for the full load operating condition are presented. The results clearly illustrate a void fraction distribution. Moreover, the role of submerged perforated sheet is investigated. The results are compared with a published paper in 1999 by Stevanovic. There is a good agreement between the introduced calculation. In addition, in the 2D model, the superficial velocity of water vapor is calculated as well.

Heat recovery Steam generator (HRSG) is a major component of combined cycle power plant. This component is often subject to gas turbine exhaust temperature and mass flow rate variation. If the power plant works on the island mode, this variation will be more and special attention is needed. In this paper, we predict the island mode operation of HRSG. At first, thermal modeling is done and a code to predict the transient behavior of the HRSG is generated. Then HRSG’s performance with regard to changes in GT’s load will be investigated. We use different strategies for gas turbine load reduction and compare HRSG’s performance. To ensure the correct performance of developed code, the steady-state numerical output of the model will be checked with the output of THERMOFLOW software.

The operation of power generation cycles and their related events are one of the main issues in the field of safety of power plants. If these events are not properly managed for any reason, the consequences will be irreparable. In the meantime, the operator action can be one of the most effective factors in the management of the accident. In this research, the operator action has been evaluated in the main Steam line break connected to the turbine and total loss of Steam generator feed water for the Bushehr power plant. Firstly, the data has been validated in both steady and transient states with the final safety analysis report of the power plant of Bushehr as a reliable reference. The results indicate a good agreement with the final safety analysis report. In the next step, the operator action has been evaluated to mitigate the thermohydraulic parameters, including temperature and pressure. Finally, by performing an operator sensitivity analysis in the main Steam line break connected to the turbine followed by total loss of Steam generator feed water, the maximum possible time for operator intervention has been estimated 76 minutes.

In this paper, nonlinear modeling and control of a typical drum Steam generator are studied. At first, dynamics equations governing the Steam generator are derived using physical principles and parameters. In fact, it is intended to combine some models presented in existing literature in order to construct a stronger model, which is to be based only on physical parameters, of Steam generator dynamics. Next, these equations are simulated using numerical methods and open-loop responses of the Steam generator system, which is inherently unstable, are obtained and investigated. Furthermore, considering boiler-follow mode as the main control mode, two PID controllers are designed using Ziegler-Nichols tuning rules. The Controllers are individually applied to the main Steam pressure and the drum water level loops. During design process, the interaction between the Steam pressure and the water level is well investigated and explained. This model can be used in researches and studies on the Steam generator dynamics optimization and also on the different modem control theories applications.

In this paper the soluble impurity distribution in a PGV-1000 Steam generator has been analyzed. A PGV-1000 Steam generator is a horizontal one with 750 MW thermal powers that produces 1467 t/h Steam. In this paper a two-dimensional model is proposed to simulate the soluble impurity distribution in the SG. It is shown that the model can estimate the impurity distribution with an error within 13%, in longitudinal direction, and within 35%, in traverse direction, of maximum impurity. With this model, various feed-water and blow-down systems are investigated. The calculated results show that the soluble impurity in a PGV-1000 Steam generator can be considerably reduced. The computation results show that, in a standard feed-water and blow-down system, the average impurity can be reduced from about 100 times the impurity of the feed water to about 25 times, and that the maximum impurity can be reduced from 270 to 180. And in the improved feed-water and blow-down system for PGV-1000 with a modification to the feed water system the impurity can be reduced 40% approximately.

This paper examines the flow accelerated corrosion in tubes downstream of an inlet header of the High-Pressure Economizer system using computational fluid dynamics (CFD). This problem was recently identified in a heat recovery Steam generator. The k-ε RNG model with enhanced wall functions was employed. CFD results showed that, at the ends of inlet pipes, abrupt change in flow area resulted in recirculation and jet flow. Flow acceleration downstream of the inlet pipes caused strong recirculation at the entrance of two to three tubes extending from the inlet pipes’ centerline. This recirculation forced the flow in the remaining area to accelerate, causing higher wall shear stresses on the side opposite the recirculation. As high shear stresses correlate with the locations where the flow accelerated corrosion occurs severely in practice, the Chilton-Colburn analogy was applied for FAC rate prediction. Predicted rates and measured rates agreed, although some predicted values were overestimated. The distributions of predicted FAC rates matched the tubes thickness distributions. The maximum predicted rate was 0. 739 mm/year on the left wall of tube 11 at an elevation 0. 045 m below the header centerline. Lastly, a design of experiments was conducted, varying operating flow temperature, pressure, and velocity. ANOVA revealed that FAC in this case was most sensitive to flow velocity. The operating temperature, pressure and tube average velocity that resulted in the minimum FAC rate of 0. 424 mm/year were 160. 48°C, 190. 76 bar, and 0. 639 m/s, respectively.

In this study, NO emission in a HRSG boiler was investigated using CFD. The comparison between the predicted results and measured values showed good agreement, which implied that the adopted combustion and NO formation models are suitable for predicting the characteristics of the flow, combustion, and NO emission in the boiler. The predicted results showed that the NO formation in the HRSG boiler is quite sensitive to fluid flow, temperature, and oxygen concentration distributions. In addition, the influence of the equivalence ratio at a fixed air mass flow rate on the flame temperature and NO formation was investigated. The results revealed that with increasing the equivalence ratio in the fuel-lean condition, higher flame temperatures established in the boiler and more NO formed. However, in the fuel-rich condition, increasing the equivalence ratio at a fixed air mass flow rate caused a decreasing trend in flame temperature and the NO formation. The maximum flame temperature and NO formation are found at the stoichiometric condition.

In recent years, new educational methods tend to combine subjects that were previously considered separate. One of the new educational approaches in the field of combining subjects is the Steam educational approach. The term Steam is related to the fields of science, technology, engineering, art, and mathematics education. The characteristic of the randomness of radioactivity in radioactive nuclear isotopes is seen in the quantity of half-life. In a dice-throwing activity, we simulate and count the number of radioactive nuclei after successive half-lives. By plotting the number of dice representing the active nuclei according to the experiment number, we try to get closer to the decay representation and derive a suitable definition for the half-life. In this lesson plan, some parts of the Steam approach have been used. If the decay graph (exponential graph with negative slope) is correctly extracted and any distance between events on the horizontal axis is chosen as a time unit, the concept of half-life can be taught to the audience. For this purpose, the students will be asked to extract the duration of the halving of the number of radioactive nuclei from the drawn graph.