scholarly journals Avoiding water hammer/fluid transients in nuclear piping systems by controlled filling

1991 ◽  
Author(s):  
Keyword(s):  
Water Hammer ◽  
Piping Systems ◽  
Fluid Transients

Nuclear Power Plant Fires and Explosions: Part IV — Water Hammer Explosion Mechanisms

2017 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Nuclear Reactor ◽  
Water Hammer ◽  
Compression Process ◽  
Flammable Gas ◽  
Piping Systems ◽  
Fukushima Daiichi ◽  
Accident Conditions

Water hammers, or fluid transients, compress flammable gasses to their autognition temperatures in piping systems to cause fires or explosions. While this statement may be true for many industrial systems, the focus of this research are reactor coolant water systems (RCW) in nuclear power plants, which generate flammable gasses during normal operations and during accident conditions, such as loss of coolant accidents (LOCA’s) or reactor meltdowns. When combustion occurs, the gas will either burn (deflagrate) or explode, depending on the system geometry and the quantity of the flammable gas and oxygen. If there is sufficient oxygen inside the pipe during the compression process, an explosion can ignite immediately. If there is insufficient oxygen to initiate combustion inside the pipe, the flammable gas can only ignite if released to air, an oxygen rich environment. This presentation considers the fundamentals of gas compression and causes of ignition in nuclear reactor systems. In addition to these ignition mechanisms, specific applications are briefly considered. Those applications include a hydrogen fire following the Three Mile Island meltdown, hydrogen explosions following Fukushima Daiichi explosions, and on-going fires and explosions in U.S nuclear power plants. Novel conclusions are presented here as follows. 1. A hydrogen fire was ignited by water hammer at Three Mile Island. 2. Hydrogen explosions were ignited by water hammer at Fukushima Daiichi. 3. Piping damages in U.S. commercial nuclear reactor systems have occurred since reactors were first built. These damages were not caused by water hammer alone, but were caused by water hammer compression of flammable hydrogen and resultant deflagration or detonation inside of the piping.

Measurement and Simulation of Water Hammer in Piping Systems Including Junction Coupling

2013 ◽  
Author(s):  
Stefan Riedelmeier ◽  
Stefan Becker ◽  
Eberhard Schlücker
Keyword(s):  
Three Dimensional ◽  
Water Hammer ◽  
Test Facility ◽  
One Dimensional ◽  
Beam Elements ◽  
Coupled Codes ◽  
Piping Systems ◽  
Complex Test ◽  
System Configurations

For the analysis of the effects of fluid-structure interaction (FSI) during water hammer in piping systems, a complex test facility was constructed. Resonance experiments with movable bends in two system configurations were carried out. The pressure and the displacement of the bend were recorded. The aim was to reproduce the results with two coupled codes: a one-dimensional solver based on the method of characteristics (MOC) for the hydraulic system and a three-dimensional solver based on the finite element method (FEM) working with one-dimensional beam elements for the structural system. The calculation included junction and friction coupling. The models were fine-tuned separately. For this purpose, special measurements were carried out. These included the determination of the structural damping, the friction factor, the influence of the bending of the anchorage, etc. After the validation of the models, the results of the coupled calculations were compared against the measurements, the performance of the coupled codes was evaluated and the most important physical effects were analyzed and are discussed.

Fluid Transients in a Pipeline With One Open End

2008 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Water Hammer ◽  
Atmospheric Conditions ◽  
Air Entrapment ◽  
Complex Interactions ◽  
Fluid Transients ◽  
Pipe Line ◽  
Multi Phase Flow ◽  
Time Required ◽  
Multi Phase ◽  
Transparent Tube

Water hammer during multi-phase flow is rather complex, but in some cases an upper limit to the pressure surge magnitude during water hammer can be estimated. In the case considered here, a two mile long pipeline with a single high point was permitted to partially drain. Due to gravitational effects, air bubbles up through the pipe line to its highest point, but the time required for air to reach the top of the pipe is rather long. Consequently, some transients caused by valve operations are affected by air entrapment and some are not. The intent of this research was to investigate the complex interactions between air, water vapor, and liquid during water hammer in a long pipe with one end of the pipe open to atmospheric conditions. To understand the system dynamics, experimental data was obtained from a long pipeline with an open end and also from a short, transparent tube. Transient calculations were performed for valve closures and pump operations as applicable. The limitations of available calculation techniques were considered in detail.

Fluid transients and fluid-structure interaction in flexible liquid-filled piping

2001 ◽  
Vol 54 (5) ◽  
pp. 455-481 ◽  
Author(s):  
David C Wiggert ◽  
Arris S Tijsseling
Keyword(s):  
Fluid Structure Interaction ◽  
Mechanical Action ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Piping Systems ◽  
Safety And Reliability ◽  
Fluid Transients ◽  
Excitation Mechanisms ◽  
Support Mechanisms ◽  
Numerical And Analytical Methods

Fluid-structure interaction in piping systems (FSI) consists of the transfer of momentum and forces between piping and the contained liquid during unsteady flow. Excitation mechanisms may be caused by rapid changes in flow and pressure or may be initiated by mechanical action of the piping. The interaction is manifested in pipe vibration and perturbations in velocity and pressure of the liquid. The resulting loads imparted on the piping are transferred to the support mechanisms such as hangers, thrust blocks, etc. The phenomenon has recently received increased attention because of safety and reliability concerns in power generation stations, environmental issues in pipeline delivery systems, and questions related to stringent industrial piping design performance guidelines. Furthermore, numerical advances have allowed practitioners to revisit the manner in which the interaction between piping and contained liquid is modeled, resulting in improved techniques that are now readily available to predict FSI. This review attempts to succinctly summarize the essential mechanisms that cause FSI, and present relevant data that describe the phenomenon. In addition, the various numerical and analytical methods that have been developed to successfully predict FSI will be described. Several earlier reviews regarding FSI in piping have been published; this review is intended to update the reader on developments that have taken place over the last approximately ten years, and to enhance the understanding of various aspects of FSI. There are 123 references cited in this review article.

scholarly journals A Hydrogen Ignition Mechanism for Explosions in Nuclear Facility Piping Systems

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Nuclear Power ◽  
Nuclear Reactor ◽  
Nuclear Industry ◽  
Ignition Source ◽  
Piping System ◽  
Nuclear Facilities ◽  
Piping Systems ◽  
Fluid Transients ◽  
Hydrogen Ignition ◽  
Explosion Mechanism

Hydrogen explosions may occur simultaneously with fluid transients' accidents in nuclear facilities, and a theoretical mechanism to relate fluid transients to hydrogen deflagrations and explosions is presented herein. Hydrogen and oxygen generation due to the radiolysis of water is a recognized hazard in piping systems used in the nuclear industry, where the accumulation of hydrogen and oxygen at high points in the piping system is expected, and explosive conditions may occur. Pipe ruptures in nuclear reactor cooling systems were attributed to hydrogen explosions inside pipelines, i.e., Hamaoka, Nuclear Power Station in Japan, and Brunsbuettel in Germany (Fig. 1Fig. 1Hydrogen explosion damage in nuclear facilities Antaki, et al. [9,10–12] (ASME, Task Group on Impulsively Loaded Vessels, 2009, Bob Nickell)). Prior to these accidents, an ignition source for hydrogen was not clearly demonstrated, but these accidents demonstrated that a mechanism was, in fact, available to initiate combustion and explosion. A new theory to identify an ignition source and explosion cause is presented here, and further research is recommended to fully understand this explosion mechanism. In fact, this explosion mechanism may be pertinent to explosions in major nuclear accidents, and a similar explosion mechanism is also possible in oil pipelines during off-shore drilling.

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