Study on Effects of Environment Conditions on Essential Service Water System of Nuclear Power Station

2017 ◽  
Author(s):  
Yang Ting ◽  
Li Guang Sheng ◽  
Li Zeng Fen ◽  
Peng Yue ◽  
Hu Jian
Keyword(s):  
Environmental Conditions ◽  
Nuclear Power ◽  
Water System ◽  
Open Water ◽  
Water Levels ◽  
Negative Effects ◽  
Power Stations ◽  
Service Water ◽  
Physical And Chemical ◽  
Essential Service

For nuclear power stations, the main function of Essential Service Water System (ESWS) is to discharge the waste heat from reactor core and spent fuel pool to the environment controllably, which is directly related to the safety and economy of nuclear power stations. Usually ESWS use open water from sea, rivers, lakes, reservoirs, as heat transfer medium. Extremely harsh environmental conditions may disable system functions and even lead to ESWS failure, directly reduce the safety and economy of nuclear power stations, and cause serious nuclear accidents. Failure of ESWS is one of the main reasons that lead to the Fukushima nuclear accident because of the loss of electricity after the earthquake and tsunami. Based on the typical ESWS configuration and conditions of serving nuclear power stations in China, the influence of environmental conditions on the function of water system is studied, and the corresponding measures are analyzed. These conditions can be divided into three categories: temperatures, water levels, and physical and chemical characteristics. Temperatures affect cooling characteristic of ESWS mainly. Nuclear power stations in tropical areas need to focus on cooling capacity might be reduced by high temperature. Those in cold region need attention to excessive cooling and freezing problems caused by low temperature. The influence of water levels is mainly fluid transport capacity and selection of equipment to ESWS. When the range of natural water level is too wide, designers shall consider measures to narrow it, such as the construction of highly reliable reservoir. Inland nuclear power stations shall try to ensure the reliability of ESWS; prevent water level changes beyond the scope of design caused by drought and flood disasters. The effects of physical and chemical properties are derived from the open water characteristics, including high salinity, high chloride ion concentration, carrying solid particles, suspended solids, and aquatics, and so on. These characteristics will cause the equipment and pipeline eroded or even damaged, aqueducts of intake and output jammed, heat exchangers of the final heat sink weakened and other negative effects, resulting in ESWS performance decline. Some of these factors are the characteristics of station site natural environment, some others are changes caused by human activities. Some factors are sustained, long-term; some others may be sudden, temporary. Influence on these factors need to be taken measures from many aspects, including structure, biological disinfection, special materials and equipment, environmental protection measures around the nuclear power station, and so on. On the whole, the environmental factors that affect ESWS in the nuclear power stations are wide, and the influence mechanism is more complex. These factors ultimately act on ESWS, but most of them cannot be banished inside of ESWS or the final heat sink system. Against the negative effects from environmental conditions, it has to be considered from all steps in the engineering of nuclear power stations, including design, construction and operation. All the measures shall be suitable to local conditions, in order to ensure the safety and economy of nuclear power stations.

Research on Operating Strategy of Total Loss of Essential Service Water System With RHR Not Connected in PWR Unit

2020 ◽  
Author(s):  
Shengtao Zhang ◽  
Ke Yi
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Heat Sink ◽  
Nuclear Power ◽  
Cooling System ◽  
Water System ◽  
Total Loss ◽  
Operating Strategy ◽  
Service Water ◽  
Essential Service

Abstract Essential Service Water System (WES) is part of the nuclear power plant cooling system which provides the final heat sink for nuclear power plants. Therefore, WES must operate stably, safely and reliably for a long time. The total loss of WES accident is a design extended condition and will result in the loss of the final heat sink of the unit. The consequences of the accident are severe. In order to deal with the accident quickly and effectively and ensure the safety and economics of the power plant in accident condition, it’s necessary to formulate corresponding treatment strategy to deal with the transient. This paper developed a strategy for dealing with the total loss of WES with Residual Heat Removal System (RHR) not connected condition in Generation III nuclear power plant. The structure of the WES system and the types of failures that may occur are analyzed, and thus the symptoms of the faults are obtained and the entry conditions for the operating strategy are determined. The effect of faults on unit equipment and safety functions and the impact on nuclear steam supply system (NSSS) control are analyzed in this paper. Combined with the unit design, the system and equipment for controlling and mitigating related safety functions are analyzed, and the mitigation method and the fallback strategy of the fault are determined. Thereby a complete operating strategy of total loss of WES with RHR not connected is obtained. In addition, this paper analyzes and evaluates the operating strategy by simulating thermal hydraulic calculation for the first time. The results show that without staff intervention Component Cooling System (WCC) temperature reached 55°C limits after running a few minutes. Based on the intervention of the operating strategy proposed in this paper, WCC temperature reached the 55°C limits when the unit was operated at about 4 hours and 55 minutes. The result shows that and the strategy can effectively alleviate the failure and provide sufficient intervention time for the operator to bring the unit to a safe state.

The Root Cause Analysis of the Bolt Fracture in the Nuclear Power Plant Essential Service Water System

2017 ◽  
Author(s):  
Li Nan ◽  
Lao Yi ◽  
Che Yinhui
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Water System ◽  
Element Distribution ◽  
Material Microstructure ◽  
Root Cause ◽  
Check Calculation ◽  
Service Water ◽  
Essential Service

When inspecting in the nuclear power plant, the bolt of the 001/004 pump in Essential Service Water system was found fracture. The bolt in 001 pump had ever fractured before, and it had been replaced. In this paper, the material, microstructure, energy dispersive spectrometry and mechanical check calculation of the bolt are analyzed. The result shows, the bolt breakage is for stress corrosion cracking, the corrosion element is Cl−. When the martensitic stainless steel is in the heat treatment, the temperature is improper control, which causing the Cr element distribution changed. So the ability of material to resist corrosion becomes poor which is the root cause of the bolt fracture.

Investigation of Effects of Piping Configuration and Water Supply Pressure on Air Intrusion

2012 ◽  
Author(s):  
Jaehyok Lim ◽  
Basar Ozar ◽  
Christopher E. Henry ◽  
Kevin B. Ramsden
Keyword(s):  
Power Plant ◽  
Water Supply ◽  
Storage Tank ◽  
Nuclear Power ◽  
Water Pressure ◽  
Water System ◽  
Supply Pressure ◽  
Service Water ◽  
Essential Service ◽  
Supply Water

An evaluation of the effects of geometry and water supply pressure on the void transport has been performed using RELAP5/MOD3.3 (patch03). Two different piping configurations were considered for a hypothetical nuclear power plant. The cases that were analyzed considered switchover between two different water supplies, i.e. condensate storage tank (CST) and essential service water system (SX) for a safety system that acted as the ultimate heat sink. In addition, two different pressures were considered for the pressure of SX to investigate the effect of supply water pressure on void transport. Results were interpreted based on the differences in the geometries of the piping configurations and supply water pressures.

scholarly journals Model Predictive Control of a River Reach with Weirs

10.29007/1nnf ◽  
2018 ◽  
Author(s):  
Klaudia Horváth ◽  
Bart van Esch ◽  
Jorn Baayen ◽  
Ivo Pothof ◽  
Jan Talsma ◽  
...  
Keyword(s):  
Decision Support ◽  
Convex Optimization ◽  
Decision Support System ◽  
Model Predictive Control ◽  
Predictive Control ◽  
Support System ◽  
Water System ◽  
Open Water ◽  
Global Optimum ◽  
Water Levels

A decision support system for water management based on convex optimization, RTC-Tools 2, is applied for a water system containing river branches connected by weirs. The advantage of convex optimization is the ability of finding the global optimum, which makes the decision support system robust and deterministic. In this work the convex modeling of open water channels and weirs is presented. The decision support system is implemented for a river made of 12 river reaches divided by movable weirs. It is shown how the discharge wave is dispatched in the river without the water levels exceeding the bounds by controlling the weir heights. After this test the optimization can be applied to a realistic numerical model and model predictive control can be implemented.

Engineering, Design, and Fabrication of Flanges and Reinforced Elbows for an Essential Service Water (ESW) Polyethylene Pipeline

2009 ◽  
Author(s):  
Harvey Svetlik
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Water System ◽  
Steel Pipe ◽  
Raw Water ◽  
Statistical Probability ◽  
Internal Corrosion ◽  
Service Water ◽  
Asme Code

30 years ago, steel pipe was the standard in the ASME code for raw water supply and raw water handling at Nuclear Power Plants. At some power plants, despite best efforts, that steel pipe has suffered intermittent leakage from external and severe MIC internal corrosion. Additionally, internal tuberculation and mineral build-up has severely constricted flow in other pipelines. Advanced, engineering pipe-grade polyethylene pipe has been extruded and used in some nuclear power plants as the effective method to eliminate corrosion and tuberculation of raw water system pipelines. Implementing the change to earth-quake tolerant polyethylene pipelines has resulted in decreased maintenance, increased system reliability, and improved plant longevity. The expectation is that the advanced polyethylene will provide continuous service up to 100 years from initial installation, with a very low statistical probability of any pressure rupture during its service life. Herein discussed is the engineering grade of polyethylene material, its design basis, the conversion of extruded heavy-wall pipe (Picture 1) into fabricated components, and the final production of fully pressure-rated, fabricated pipe fittings with wall thickness of up to 5-inches. Fabrication pictures 1 to 12 are included.

Modern Bimodal High Density Polyethylene for the Nuclear Power Plant Piping System

2009 ◽  
Author(s):  
Adel N. Haddad
Keyword(s):  
High Density Polyethylene ◽  
Nuclear Power ◽  
Large Diameter ◽  
Water System ◽  
High Density ◽  
Nuclear Industry ◽  
Piping System ◽  
Service Water ◽  
Hdpe Pipe ◽  
Related Service

Originally introduced in the 1990s, bimodal HDPE, pipe resins are still finding new niches today, including even nuclear power plants. HDPE pipe grades are used to make strong, corrosion resistant and durable pipes. High density polyethylene, PE 4710, is the material of choice of the nuclear industry for the Safety Related Service Water System. This grade of polymer is characterized by a Hydrostatic Design Basis (HDB) of 1600 psi at 73 °F and 1000 psi at 140 °F. Additionally bimodal high density PE 4710 grades display >2000 hours slow crack growth resistance, or PENT. HD PE 4710 grades are easy to extrude into large diameter pipes; fabricate into fitting and mitered elbows and install in industrial settings. The scope of this paper is to describe the bimodal technology which produces HDPE pipe grade polymer; the USA practices of post reactor melt blending of natural resin compound with black masterbatch; and the attributes of such compound and its conformance to the nuclear industry’s Safety Related Service Water System.

Service Water Life Cycle Management

2008 ◽  
Author(s):  
Eric J. Houston ◽  
Arlene S. Rahn ◽  
George J. Licina
Keyword(s):  
Nuclear Power ◽  
Deterministic Model ◽  
Operating Time ◽  
Water System ◽  
Water Systems ◽  
Most Probable Number ◽  
Probable Number ◽  
System Integrity ◽  
Service Water ◽  
Water Piping

Nuclear plant service water systems are a critical part of the facility’s infrastructure. System integrity and performance are vital for plant reliability and essential to achieving a plant life of 40 years and beyond. Corrosion, fouling (macrofouling, microfouling and sedimentation) and other effects that are detrimental to the reliability of the service water system led to the issue of NRC Generic Letter 89-13 “Service Water System Problems Affecting Safety-Related Equipment.” This generic letter continues to be a fundamental guideline for safety related service water systems at all U.S. nuclear plants. The low temperature and pressure service water piping systems are primarily degraded by corrosion. Because of the complexity and random nature of corrosion processes, it is nearly impossible to develop a mathematically deterministic model that accurately predicts pipe wall loss. However, if statistical distributions are used to describe the various corrosion processes, mathematical algorithms that incorporate all of the distributions, iterated a statistically significant number of times, can be used to forecast the most probable number of leaks. This paper predicts the condition of service water piping at Kewaunee Nuclear Power Plant using the described model and includes the expected number of through-wall leaks as a function of operating time.

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