Numerical Analysis of Unsteady Flow Field in the RWT for the Prediction of the Potential for Air Ingression Into the ECC Supply Lines During the SBLOCA at the KSNPs

2007 ◽  
Author(s):  
Jong Chull Jo ◽  
Seon Oh Yu
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Water Level ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Vortex Flow ◽  
Air Entrainment ◽  
Water Tank ◽  
Outlet Valve

This paper addresses the three-dimensional analysis of unsteady flow in the RWT (Refueling Water Tank) for the prediction of the potential for air ingression into the ECC (Emergency Core Cooling) pump during the SBLOCA (Small Break Loss Of Coolant Accident) at KSNPs (Korean Standard Nuclear Power plants). Upon the receipt of RAS (Recirculation Actuation Signal) by the occurrence of SBLOCA, the RWT outlet valve is designed to be isolated manually. At the nuclear power plants without the provision of automatic isolation operation of the valve on the downstream of the RWT line, the refueling water begins to discharge from the RWT, which may result in forming and developing the vortex flow in the RWT, under the condition of the minimum pressure of containment and minimum water level of containment recirculation sump during the phase of RAS. Due to the vortex flow, when the water level is below the critical height, a dip starts to develop, causing air ingression before the refueling water drains fully. Hence it can be surmised that there is a possibility of ECC pump failure due to air ingression into the ECC supply line even before the RWT is fully drained. Therefore, in this work, when the RAS is actuated followed by the SBLOCA occurrence, a quantitative evaluation for the maximum limiting allowable time for the manual closing of RWT outlet valve is carried out to eliminate the possibility of air ingression into the ECC pump from the RWT. To do this, the unsteady flow field in the RWT including the drain pit with the connected discharge piping in the process of SBLOCA is analyzed using a CFD (Computational Fluid Dynamics) code. In addition, the transient flow behavior accompanying air entrainment resulting from the dip formation due to vortex flow at the upper part of RWT is examined and the applicable limiting time of the isolation valve closing for preventing air ingression is assessed.

scholarly journals Application of Fuzzy Control in Ocean Nuclear Power Plant Control

2021 ◽  
Vol 2076 (1) ◽  
pp. 012010
Author(s):  
Chunhui Dai ◽  
Ping Song ◽  
Lie Chen ◽  
Xingsheng Lao ◽  
Kelong Zhang
Keyword(s):  
Mathematical Model ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Fuzzy Control ◽  
Water Level ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Fuzzy Controller ◽  
Good Control

Abstract In marine nuclear power plants based on molten salt reactors, the complexity of core nuclear reactions, fuel fluidity, and the “false” water level characteristics of the steam generator water level make it unrealistic to establish an accurate mathematical model, so it is difficult to implement traditional PID control methods. This has increased substantially. The fuzzy control has a good solution to this feature. Therefore, combined with the fuzzy control that does not depend on the precise mathematical model of the controlled object, the fuzzy controller of the nuclear power plant is designed, and the control research of the core power is obtained respectively through MATLAB/Simulink simulation. It shows that the designed fuzzy controller can achieve good control of nuclear power plants.

Study on Flushing Phenomena by Microwave Heating

2013 ◽  
Author(s):  
Tatsunori Yamaki ◽  
Akiko Kaneko ◽  
Yutaka Abe ◽  
Tomoomi Segawa ◽  
Koichi Kawaguchi ◽  
...  
Keyword(s):  
Water Level ◽  
Microwave Heating ◽  
Nuclear Fuel ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Nitrate Solution ◽  
Vessel Diameter ◽  
Initial Water ◽  
Liquid Superheat

Recently, the number of nuclear power plants has been increased in many countries. In contrast, uranium fuels used in nuclear power plants are exhaustible resources. Therefore, it is required to exploit uranium resources effectively, and reprocessing of spent fuel is indispensable. To use recovered uranium and plutonium as raw material of nuclear fuel, reprocessing solution (uranium and plutonium mixed nitrate solution) of the spent nuclear fuel is converted to uranium and plutonium mixed oxide (MOX) powder. Microwave heating direct denitration method (MH method) is one of such methods to convert nitrate solution to MOX powder. The cylindrical denitration vessel can be expected to realize high-speed and high-capacity processing against traditional shallow vessel. However, flushing and overflow phenomena of solution have been confirmed in cylindrical vessel. Thus, the safety and the optimization of the vessel shape during microwave heating. In the present study, the purpose of this paper is to clarify generation conditions and generation mechanism of flushing phenomena that is not fully understood. In experiment, flushing phenomena was observed and the liquid temperature was measured using microwave heating device. The main parameters are the vessel diameter, initial water level and the magnetron power. There was tendency of flushing in the case of short vessel diameter and high initial water level when magnetron power was constant. There was also tendency of flushing in the case of large magnetron power when vessel diameter and initial water level was constant. From visualization, it was clarified that generation of singular bubble triggers flushing. If flushing occurs, the liquid is blown up at a burst, and the vessel become almost empty. From temperature measurement results, it was clarified that the liquid had over 10 °C superheat just before flushing. Therefore, it was suggested that the liquid superheat affected flushing significantly. Generation conditions of flushing are different with the vessel diameter, initial water level and the magnetron power because it is considered that these characteristics have influence on the liquid superheat.

scholarly journals Risk Assessment of Extreme Weather Conditions for Nuclear Power Plants at Tidal Rivers

2010 ◽  
Vol 13 (1) ◽  
pp. 41-52 ◽  
Author(s):  
Heinz-Peter Berg ◽  
Matias Krauß
Keyword(s):  
Risk Assessment ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Water Level ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Weather Conditions ◽  
Extreme Weather ◽  
Tidal Rivers

Risk Assessment of Extreme Weather Conditions for Nuclear Power Plants at Tidal RiversThe effects of flooding on a nuclear power plant site may have a major bearing on the safety of the plant and may result in a common cause failure for safety related systems, such as the emergency power supply systems. For river sites with tidal influences, an extreme flood event - tide combined with storm water level set-up - must be assumed. A storm-tide must be covered with an exceeding frequency of 10-4/a. However, the risk assessment regarding the availability of systems and components of a nuclear power plant also includes the situation of extreme low water level of rivers, i. e. below the minimum water level necessary for the supply of the nuclear power plants with cooling water.

lnvestigation of β-Emission Methods of Monitoring Coolant Water Level in Nuclear Power Plants

Atomic Energy ◽  
2017 ◽  
Vol 122 (3) ◽  
pp. 207-212
Author(s):  
S. I. Aleksandrov ◽  
A. A. Bol’shov ◽  
A. V. Kornienko ◽  
I. V Novikov ◽  
V. V. Postnikov ◽  
...  
Keyword(s):  
Water Level ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Coolant Water

Experimental Investigation on Temperature Characteristics of Direct Contact Condensation in a Natural Circulation System

2020 ◽  
Author(s):  
Jianchuang Sun ◽  
Ming Ding ◽  
Zhengpeng Mi ◽  
Zhuohua Zhang
Keyword(s):  
Water Temperature ◽  
Heat Sink ◽  
Direct Contact ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Natural Circulation ◽  
Water Tank ◽  
Subcooled Water ◽  
Contact Condensation

Abstract Direct contact condensation (DCC) is a common physical phenomenon appearing in the nuclear power plants and other industrial applications. The current research on DCC focuses on steam-water counterflow or jet flow under forced flow conditions. For some natural-circulation passive safety systems in floating nuclear power plants, the heated section is connected with the heat sink by the horizontal pipes. The heat sink is usually the ocean. In such natural circulation systems (NCSs), the steam produced in the heated section will inevitably contact the subcooled water in the ocean and result in DCC event. In this paper, the fundamental characteristics of two-phase flow were described in detail. In addition, the influences of the subcooled water temperature on the flow rate, outlet temperature, steam bubble behaviors, and pressure surge were emphatically discussed. The experimental results revealed that the subcooled water in the water tank could reversely flow into the pipe, which was able to cause condensation induced water hammer (CIWH) event and flow oscillation. Further research showed that the subcooled water was evidently prevented from reversely flowing into the pipe with the increase in the subcooled water temperature. The position where the DCC event occurs transferred from the pipe to the water tank, and the pressure peak obviously reduced, even disappear when the subcooled water temperature is larger than 61 °C.

Adaptive neurofuzzy controller to regulate UTSG water level in nuclear power plants

2005 ◽  
Vol 52 (1) ◽  
pp. 421-429 ◽  
Author(s):  
S.R. Munasinghe ◽  
Min-Soeng Kim ◽  
Ju-Jang Lee
Keyword(s):  
Water Level ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants
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