Control of Pipeline Dynamics With Disk Spring Restraints (Design Paper)

1991 ◽  
Vol 113 (2) ◽  
pp. 332-336 ◽  
Author(s):  
E. C. Goodling
Keyword(s):  
Power Plant ◽  
Water Hammer ◽  
Mixed Phase ◽  
Vapor Flow ◽  
Adequate Control ◽  
Process Piping ◽  
Disk Spring ◽  
Phase Water ◽  
Design Paper ◽  
Boiler Feedwater

Dynamic transients such as steam hammer or water hammer in power plant or process piping can generate high destructive reactions if rigid restraints or snubbers are used in an attempt to exert total control of pipe response. However, where some movement can be tolerated, adequate control can be maintained with much lower resulting loads in the restraining structures and components. The disk spring restraint has been demonstrated to be a practical device for controlling piping movements caused by typical dynamic upset conditions in steam and boiler feedwater piping and in drain lines carrying mixed phase (water and vapor) flow. This paper discusses the simplified mathematics used in estimating loads to design disk spring restraints for such applications.

Efficient Second-Order Accurate Shock-Capturing Scheme for Modeling One- and Two-Phase Water Hammer Flows

2008 ◽  
Vol 134 (7) ◽  
pp. 970-983 ◽  
Author(s):  
Arturo S. León ◽  
Mohamed S. Ghidaoui ◽  
Arthur R. Schmidt ◽  
Marcelo H. García
Keyword(s):  
Water Hammer ◽  
Second Order ◽  
Shock Capturing ◽  
Two Phase ◽  
Phase Water

Water Hammer Characteristics for Parallel Pumps Water Supply Systems

2008 ◽  
Author(s):  
Wenxi Tian ◽  
Guanghui Su ◽  
Suizheng Qiu ◽  
Gaopeng Wang ◽  
Qing Lu
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Water Supply ◽  
High Speed ◽  
Nuclear Power ◽  
Optimization Design ◽  
Check Valve ◽  
Water Hammer ◽  
Characteristic Line ◽  
Water Supply Systems

The water hammer induced by abrupt velocity change of fluid flow is inevitable for nuclear power plant systems because of the sudden opening or closing of valves, the sudden startup or shutdown of the pumps and the rupture of pipes. The water hammer pressure wave can damage the pipes and cause the abnormal shutdown of Nuclear Power Plant (NPP). The object of this study is a Parallel Pumps Water Supply system (PPWS) adopted in a NPP. The PPWS is composed of two parallel mixed-flow pumps connected with a check valve separately, a container, a throttle flap and pipe lines. The Method of Characteristic line (MOC) was adopted to evaluate the water hammer behaviors of the PPWS during the alternate startup and shutoff conditions of two parallel pumps. A code was developed using Fortran language to compute the transient behaviors including he peak pressure, the flow velocity and the movement of the valve plate. The results indicate that the water hammer behaviors under low speed startup condition differ from that of high speed startup condition. The maximum pressure vibration amplitude is up to 5.0MPa occurring under high-high speed startup condition. The computation results are instructive for the optimization design of the PPWS so as to minimize the damage potential induced by water hammer.

Study on Water Hammer in the Overpressure Discharge Pipe of Nuclear Power Plant

2017 ◽  
Author(s):  
Qingmu Xu ◽  
Kun Cai ◽  
Jie Qin ◽  
Junkai Yuan ◽  
Juan Li
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Water Hammer ◽  
Liquid Column ◽  
Normal Operation ◽  
Pipeline System ◽  
Spent Fuel ◽  
Vapor Cavity ◽  
Spent Fuel Pool

Water hammer phenomenon is a significant pressure wave in pipe system caused by momentum change when the moving fluid is forced to stop or change direction instantaneously. Common causes of water hammer are sudden valve closing at the end of a pipeline system, pump failure, check valve slam etc. The steam transportation pipeline system may also be vulnerable to water hammer when it confronts with the situation where liquid and steam co-exist. Water hammer often occurs when steam condenses into water in a horizontal section of steam piping. Then steam “picks up” water to form a high-velocity “slug” and create extra stress to pipe. When steam is trapped into sub-cooled water, the collapse of vapor cavity can lead to collision of two columns of liquid, resulting in a large rise in pressure which will damage pipes, supporting structures and hydraulic machinery. Nuclear power plant is composed of complex equipments and piping systems, lots of which contain both liquid and steam. Hence, there is a potential threat of occurrence of water hammer to the normal operation of systems. Thus, this phenomenon needs to be well investigated and prevented with some effective methods. For the purpose of overpressure relief under severe accidents, the spent fuel pool cooling system of CAP1000 series nuclear power plant provides a discharge passage from containment to spent fuel pool. When the containment pressure exceeds the control value, valve is opened to discharge high-temperature and high-pressure steam until the pressure drops to a safety value. During this process, serious water hammer happens, causing pressure rise beyond the design pressure and further leading to damages to pipes and structures. Therefore, water hammer of overpressure discharge pipeline in CAP1000 plant is studied in this work. On the basis of verification of the capabilities of computational code RELAP5/MOD3.3, hydraulic transient of water hammer is simulated under different conditions. It is indicated that after steam discharge stops, residual steam in pipe condenses because of contact with sub-cooled water in spent fuel pool. Subsequently, the rapid backflow and vapor cavity lead to a severe water hammer. The detailed analysis has shown that water temperature of spent fuel pool has a decisive influence on the mechanism of water hammer phenomenon, including collision of liquid column to valve disc and cavity collapse in the horizontal pipe. The collision and separation of liquid column result in relatively lower pressure amplitude.

Nuclear Power Plant Fires and Explosions: Part II — Hydrogen Ignition Overview

2017 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Power Plants ◽  
Water Hammer ◽  
Hydrogen Gas ◽  
Direct Result ◽  
Plant Safety ◽  
Hydrogen Ignition ◽  
Fukushima Daiichi

Major accidents that were affected by hydrogen fires and explosions included Chernobyl, Three Mile Island, and Fukushima Daiichi. Smaller piping explosions have occurred at Hamaoka and Brunsbüttel Nuclear Power Plants. An overview of pertinent topics is presented here to compare similarities and differences between these accidents. In particular, a hydrogen ignition mechanism is presented here, where fluid transients, or water hammer, may cause pressures to compress flammable hydrogen gas in reactor systems. As the gas compresses, it heats to temperatures sufficient to cause autoignition, or dieseling. Autoignition then leads to fires or explosions in nuclear power plant systems. To explain this evolving theory on hydrogen ignition during fires and explosions, various nuclear power plant hydrogen accidents require discussion. For example, Chernobyl explosions were unaffected by water hammer, while a Three Mile Island hydrogen fire was a direct result of water hammer following a reactor meltdown, and explosions that followed a meltdown at Fukushima Daiichi occurred during a water hammer event. Other piping damages also occurred during water hammer events. The primary purpose of this paper is to serve as a literature review of past accidents and to provide new insights into those accidents. In short, what is known versus what is unknown is discussed here with respect to the ignition sources of nuclear power plant fires and explosions. How can nuclear power plant safety be assured unless previous fire and explosion causes are understood? Prior to this work, they were not understood.

scholarly journals Effects of Cloud Microphysics on the Vertical Structures of Cloud Radiative Effects over the Tibetan Plateau and the Arctic

2021 ◽  
Vol 13 (14) ◽  
pp. 2651
Author(s):  
Yafei Yan ◽  
Yimin Liu ◽  
Xiaolin Liu ◽  
Xiaocong Wang
Keyword(s):  
Tibetan Plateau ◽  
Cloud Microphysics ◽  
Mixed Phase ◽  
The Arctic ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
The Tibetan Plateau ◽  
Radiative Effects ◽  
Cloud Radiative Effects ◽  
Phase Water

The Tibetan Plateau (TP) and the Arctic are both cold, fragile, and sensitive to global warming. However, they have very different cloud radiative effects (CRE) and influences on the climate system. In this study, the effects of cloud microphysics on the vertical structures of CRE over the two regions are analyzed and compared by using CloudSat/CALIPSO satellite data and the Rapid Radiative Transfer Model. Results show there is a greater amount of cloud water particles with larger sizes over the TP than over the Arctic, and the supercooled water is found to be more prone to exist over the former than the latter, making shortwave and longwave CRE, as well as the net CRE, much stronger over the TP. Further investigations indicate that the vertical structures of CRE at high altitudes are primarily dominated by cloud ice water, while those at low altitudes are dominated by cloud liquid and mixed-phase water. The liquid and mixed-phase water results in a strong shallow heating (cooling) layer above the cooling (heating) layer in the shortwave (longwave) CRE profiles, respectively.

Simulation of the Water Hammer in a Hydro Power Plant Caused by Draft Tube Surge

2003 ◽  
Author(s):  
Albert Ruprecht ◽  
Thomas Helmrich
Keyword(s):  
Power Plant ◽  
Draft Tube ◽  
Three Dimensional ◽  
Water Hammer ◽  
Tube Flow ◽  
Three Dimensional Flow ◽  
Hydro Power ◽  
One Dimensional ◽  
Water Power ◽  
Dimensional Flow

The system oscillations of a water power plant caused by the draft tube flow in part load are investigated. A coupled simulation of a one-dimensional water hammer analysis and a three-dimensional flow calculation of the draft tube vortex rope is applied. With this approach the excitations of the oscillations, frequencies and amplitudes, have not to be estimated but are obtained from the simulation. This allows an accurate prediction of the system oscillations caused by draft tube surge.

Calculation of Bounding Pressures Due to Condensation-Induced Water Hammer at the Davis-Besse Nuclear Power Plant in Response to Generic Letter 96-06

2003 ◽  
Author(s):  
G. Thomas Elicson ◽  
James P. Burelbach ◽  
Theodore A. Lang
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Water Flow ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Cooling Water ◽  
Water Hammer ◽  
Service Water ◽  
Water Columns

The U.S. NRC is currently evaluating nuclear plant responses to Generic Letter (GL) 96-06, “Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions” [1]. GL 96-06 is concerned with potential two-phase flow and water hammer conditions that could be present in the cooling water systems of nuclear power plants during design-basis accidents. Nuclear power plants rely on large capacity service water pumps to supply cooling water flow, via an extensive pipe network, to heat exchangers such as room coolers, pump lube oil coolers, and containment air coolers (CACs), for normal and abnormal plant operation. Following a postulated a loss of offsite power (LOOP) event, the normal electrical power supply to the service water pump would be lost resulting in a 20 to 30 second cooling water flow interruption while a diesel generator is started and the service water pump load is sequenced onto the diesel generator. In power plants, such as the Davis-Besse Nuclear Power Plant with open service water systems that draw from a lake or a river and supply safety-related CAC heat exchangers located 30 to 40 feet above the pump outlet, this could lead to cold water column separation in the heat exchanger supply and return piping. If a loss of coolant accident (LOCA) occurs coincident with the LOOP, then boiling in the CAC heat exchanger tubes could occur, as well. Upon restoration of the cooling water flow, dynamic loading could be expected as steam condenses and water columns rejoin. The TREMOLO computer program [2,3] has been used to calculate dynamic thermal hydraulic response and reaction forces in service water piping systems for several nuclear power plants in response to GL 96-06. A consistent result obtained in each of these GL 96-06 analyses is that the LOOP + LOCA scenario produces the bounding loads rather than the LOOP-only scenario. This result seemingly contradicts current industry thinking which suggests that because the water columns are colder and the void fraction lower during LOOP-only scenarios, the LOOP-only loads should be bounding [4,5,6]. While the physics supports the conclusion that the rejoining of colder water columns will generally yield the largest water hammer pressure rise, when actual plant geometry and credible accident scenarios are analyzed, a different picture emerges. This paper couples insights obtained from the GL 96-06 TREMOLO analysis of the Davis-Besse Nuclear Power Plant with independent hand calculations and experimental evidence to support the conclusion that the LOCA+LOOP scenario will produce the bounding loads in service water piping systems.

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