Experimental Evaluation of Ability of Relap5, Drako®, Flowmaster2™ and Program Using Unsteady Wall Friction Model to Calculate Water Hammer Loadings on Pipelines

2006 ◽  
Author(s):  
Jerzy Marcinkiewicz ◽  
Adam Adamkowski ◽  
Mariusz Lewandowski
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Transient Flow ◽  
Water Hammer ◽  
Friction Model ◽  
Third Party ◽  
Wall Friction ◽  
Courant Number ◽  
Common Procedure ◽  
Friction Models

Mechanical loadings on pipe systems caused by water hammer (hydraulic transients) belong to the most important and most difficult to calculate design loadings in nuclear power plants. The most common procedure in Sweden is to calculate the water hammer loadings on pipe segments, according to the classical 1D theory of liquid transient flow in a pipeline, and then transfer the results to strength analyses of pipeline structure. This procedure assumes that there is quasi-steady respond of the pipeline structure to pressure surges — no dynamic interaction between the fluid and the pipeline construction. The hydraulic loadings are calculated with 1-D so-called “network” programs. Commonly used in Sweden are Relap5, Drako and Flowmaster2 — all using quasi-steady wall friction model. As a third party accredited inspection body INSPECTA NUCLEAR AB reviews calculations of water hammer loadings. The presented work shall be seen as an attempt to illustrate ability of Relap5, Flowmaster2 and Drako programs to calculate the water hammer loadings. A special attention was paid to using of Relap5 for calculation of water hammer pressure surges and forces (including some aspects of influence of Courant number on the calculation results) and also the importance of considering the dynamic (or unsteady) friction models. The calculations are compared with experimental results. The experiments have been conducted at a test rig designed and constructed at the Szewalski Institute of Fluid–Flow Machinery of the Polish Academy of Sciences (IMP PAN) in Gdansk, Poland. The analyses show quite small differences between pressures and forces calculated with Relap5, Flowmaster2 and Drako (the differences regard mainly damping of pressure waves). The comparison of calculated and measured pressures and also a force acting on a pre-defined pipe segment show significant differences. It is shown that the differences can be reduced by using unsteady friction models in calculations. Recently, such models have been subjects of works of several researches in the world.

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.

scholarly journals Assessment of water hammer effects on boiling water nuclear reactor core dynamics

2007 ◽  
Vol 22 (1) ◽  
pp. 18-33 ◽  
Author(s):  
Anis Bousbia-Salah
Keyword(s):  
Pressure Wave ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Reactor ◽  
Reactor Core ◽  
Water Hammer ◽  
Pressure Wave Amplitude ◽  
Sensitivity Studies ◽  
Rapid Transients ◽  
Complex Phenomena

Complex phenomena, as water hammer transients, occurring in nuclear power plants are still not very well investigated by the current best estimate computational tools. Within this frame work, a rapid positive reactivity addition into the core generated by a water hammer transient is considered. The numerical simulation of such phenomena was carried out using the coupled RELAP5/PARCS code. An over all data comparison shows good agreement between the calculated and measured core pressure wave trends. However, the predicted power response during the excursion phase did not correctly match the experimental tendency. Because of this, sensitivity studies have been carried out in order to identify the most influential parameters that govern the dynamics of the power excursion. After investigating the pressure wave amplitude and the void feed back responses, it was found that the disagreement between the calculated and measured data occurs mainly due to the RELAP5 low void condensation rate which seems to be questionable during rapid transients. .

Blowout preventer (BOP) risk model to assist critical decisions in offshore drilling

2013 ◽  
Vol 53 (1) ◽  
pp. 209
Author(s):  
Inge Alme ◽  
Angel Casal ◽  
Trygve Leinum ◽  
Helge Flesland
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Oil And Gas ◽  
Risk Model ◽  
Oil And Gas Industry ◽  
Third Party ◽  
Risk Level ◽  
Main Task ◽  
Offshore Drilling ◽  
Drilling Rig

The BOP is a critical safety system of an offshore drilling rig, as shown in the 2010 Macondo accident. A challenge for the oil and gas industry is to decide what to do when the BOP is failing. Pulling the BOP to the surface during operations for inspection and testing is a costly and timely operation. Many of the potential failures are not critical to overall safety as multiple levels of redundancy are often available. Scandpower and Moduspec, both subsidiaries of Lloyd’s Register, have developed a BOP risk model that will assist the industry make the pull or no pull decisions. Scandpower’s proprietary software RiskSpectrum is used for the modelling. This software is used for equivalent decision support in the nuclear power industry, where the risk levels of total nuclear power plants are monitored live by operators in the control rooms. By modelling existing BOPs and their submerged control systems, and using risk monitor software for keeping track on the status of the BOP subsystems and components, the industry is able to define the real-time operational risk level the BOP is operating at. It, therefore, allows the inclusion for sensitivity modelling with possible faulty components factored in the model. The main task of the risk model is to guide and support energy companies and regulators in the decision process when considering whether to pull the BOP for repairs. Moreover, it will help the communication with the regulators, since the basis for the decisions are more traceable and easier to follow for a third party.

Performance-Based NDE Personnel Qualifications

2014 ◽  
Author(s):  
Henry M. Stephens
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
White Paper ◽  
Third Party ◽  
Nondestructive Examination ◽  
Alternative Approach ◽  
Hands On ◽  
Task Team ◽  
Integrity Management ◽  
Division 2

This paper establishes an alternative approach for nondestructive examination (NDE) personnel qualification for the boiler and pressure vessel (B&PV) industry. This is the “white paper” developed by the Section XI, Division 2, Task Team, Performance-based NDE Personnel Qualifications. It is anticipated to be the basis for the NDE personnel qualification criteria for the revised Section XI, Division 2, REQUIREMENTS FOR RELIABILITY AND INTEGRITY MANAGEMENT (RIM) PROGRAM FOR NUCLEAR POWER PLANTS that is currently being developed. Based on review of a number of quantitative NDE reliability studies conducted to-date the current deterministic approach to NDE personnel qualification based on such schemes as ASNT SNT-TC-1A, ANSI/ASNT CP-189, EN-473, ISO-9712 and other similar approaches are not as effective as desired. The goal of this document is to present an alternative approach to the deterministic NDE personnel qualification schemes. This paper presents a systematic approach to training together with performance-based tests, psychometrically validated evaluation of knowledge and skills that will improve a NDE candidate’s performance. A majority of traditional employer-based written examinations are not developed or validated psychometrically. The use of third-party psychometrically validated examinations would replace the current practice of employer developed and administered examinations. It improves upon traditional ASNT SNT-TC-1A, ASNT/ANSI CP-189, ISO-9712, etc., requirements by including more comprehensive hands-on practical examinations on a statistically valid set of samples containing flaws representative of those expected to be encounter in shop and field conditions. The sample sets will be designed for either a “general” NDE method, or “limited” technique(s) of a method, or for industry specific sector needs, as applicable.

Water Hammer Analysis/Prevention/Mitigation in Fire Protection Systems at Power Plants

2003 ◽  
Author(s):  
Asif H. Arastu ◽  
Eugene Tom
Keyword(s):  
Fire Protection ◽  
Nuclear Power ◽  
Power Plants ◽  
Void Formation ◽  
Water Hammer ◽  
Mitigation Strategies ◽  
Physical Damage ◽  
Protection Systems ◽  
Piping Networks ◽  
In Fire

Fire Protection water systems are typically piping networks where water is pumped from a low elevation reservoir at atmospheric pressure to higher elevations in the buildings served by the system. Because of this nature of their design, they are prone to water hammers due to water column separation & rejoining. A loss of pressure can lead to void formation at high elevations whose collapse can result in severe water hammer. A damaging water hammer event that occurred at a nuclear power plant (Arastu, et al, 1999) causing a catastrophic valve failure pointed to the need to prevent and mitigate such potential events at other plants. One important aspect of that event is that prior to it, several events of similar magnitude had occurred that did not apparently cause physical damage but degraded the system sufficiently to make it susceptible to damage. This paper discusses the causes of water hammer in Fire Protection Systems at power plants and identifies analysis, prevention, and mitigation strategies. Using a Method Of Characteristics based program, computer simulation results of the application of the mitigative measures are given for three large plant systems to demonstrate the effectiveness of the measures proposed at these plants.

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.

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.

Nuclear Power Plant Fires and Explosions: Part III — Hamaoka Piping Explosion

2017 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Nuclear Power ◽  
Noble Metals ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Nuclear Reactor ◽  
Reactor Core ◽  
Water Hammer ◽  
Preventive Action ◽  
Hydrogen Ignition ◽  
Accident Conditions

An explosion that burst a steel pipe like a paper fire cracker at the Hamaoka Nuclear Power Station, Unit-1 is investigated in this paper, which is one of a series of papers investigating fires and explosions in nuclear power plants. The accumulation of flammable hydrogen and oxygen due to radiolysis has long been recognized as a potential problem in nuclear reactors, where radiolysis is the process that decomposes water into hydrogen and oxygen by radiation exposure in the reactor core. Hydrogen ignition and explosion has long been considered the cause of this Hamaoka piping explosion, but the cause of ignition was considered to be a minor fluid transient, or water hammer, that ignited flammable gasses in the piping, which was made possible by the presence of catalytic noble metals inside the piping. The theory presented here is that a much larger pressure surge occurred due to water hammer during operations. In fact, calculations presented here serve as proof of principle that this explosion mechanism may be present in many operating nuclear power plants. Chubu Electric, the operator of the Hamaoka plant, took appropriate actions to prevent this type of explosion in their plants in the future. In fact, this accident indicates one potential preventive action from explosions for other operating plants. Ensure that a system high point is available, where mixed hydrogen and oxygen may be removed during routine operations and during off-normal accident conditions, such as nuclear reactor meltdowns and loss of coolant accidents.

Waterhammer Analysis of Fire Protection System Due to Draining of High Elevation Headers

2002 ◽  
Author(s):  
S. Mahmood Husaini ◽  
Riyad K. Qashu ◽  
David Y. Arai ◽  
Jeffrey S. Summy
Keyword(s):  
Fire Protection ◽  
Nuclear Power ◽  
Power Plants ◽  
High Elevation ◽  
Sprinkler System ◽  
Water Hammer ◽  
Protection System ◽  
Hydraulic Analysis ◽  
Forcing Functions ◽  
Fire Protection System

This paper presents a methodology for analyzing the potential for water hammer in fire protection systems of nuclear power plants due to draining of high elevation headers. A transient thermal hydraulic analysis was performed that modeled the combined San Onofre Nuclear Generating Station (SONGS) Units 2 and 3 Fire Protection System in general and the high elevation piping in minute detail. The purpose of this analysis was to simulate a postulated scenario that actuates a sprinkler system resulting in the draining of high elevation headers, followed by the start up of the main pumps. The analysis was based on a generalized computer program that utilizes the Method of Characteristics (MOC) numerical scheme. The forcing functions generated by the hydraulic analyses indicated that some hangers would be over loaded. In order to mitigate the water hammer and reduce the loads, the system was analyzed by modeling vacuum breakers at selected locations. The cushioning effect of the air introduced into the system by using vacuum breakers was found to significantly reduce the intensity of the water hammer. Subsequent stress and pipe support analysis predicted there will be no damage to the hangers. The details of the hydraulic analysis, such as the model, pressure and velocity time histories at selected locations, and forcing functions for the cases with and without vacuum breakers are included. Only the conclusions of the stress and pipe support analysis are presented.

Sign in / Sign up

Export Citation Format

Share Document