Improvement of Integrity Concepts for NPP Primary Circuit Piping

2008 ◽  
Author(s):  
Alexey Arzhaev ◽  
Sergey Butorin
Keyword(s):  
Carbon Steel ◽  
General Scheme ◽  
Primary Circuit ◽  
Feed Water ◽  
Outer Diameter ◽  
Intergranular Stress Corrosion ◽  
Methodology Development ◽  
Integrity Assessment ◽  
Piping Systems ◽  
Steel Piping

Operating NPPs license extension activities in Russia produced strong demand for safety improvement of plants build according to earlier standards. Installation of additional supports as pipe whip restraints is one of requirement in acting regulatory documentation which should be followed or compensated by appropriate measures like Leak Before Break (LBB) analyses and improvement of In-Service Inspection (ISI) and Leak Detecting System (LDS). Basic document for LBB concept application to Russian NPP piping is RD 95 10547-99. Its requirements correspond to classical LBB principles used in many countries in Europe, USA and Japan. In many real cases requirements of RD 95 10547-99 could not be applied to safety important NPP piping systems due to the presence of specific features of operational degradation due to some corrosion mechanisms: for example, erosion-corrosion (E-C) for carbon steel piping and intergranular stress corrosion cracking (IGSSC) for heat affected zones of austenitic piping weldments. For special case of RBMK piping with outer diameter 325 mm (potentially susceptible to IGSCC) special Break Preclusion Concept has been developed in Russia after IAEA Extrabudgetary Program in 2000–2002. Contrary to LBB Concept demanding for all four basic principles to be completely fulfilled BP Concept accepts some principles to be fulfilled in a balanced way with demonstration of monitored degradation effectively achieved in operation. Special BP Concept is being developed now to support integrity assessment of RBMK carbon steel steam and feed water piping potentially susceptible to E-C which requires another set of measures to demonstrate principle of controlled degradation in operation then in case of austenitic steel piping. General scheme of piping integrity analyses according to LBB and BP Concepts is discussed and examples of specific approaches to achieve controlled degradation are illustrated in paper. As result of LBB and BP Concepts application it is possible to substantiate reject of additional piping whip restraints implementation on-site. Examples of similar safety methodology development in other countries have been reported at IAEA Specialists Meeting on LBB in Kiev, Ukraine in November 2006.

Fatigue-Ratcheting Behavior of 6 in Pressurized Carbon Steel Piping Systems Under Seismic Load: Experiments and Analysis

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
A. Ravi Kiran ◽  
G. R. Reddy ◽  
P. N. Dubey ◽  
M. K. Agrawal
Keyword(s):  
Carbon Steel ◽  
Response Spectrum ◽  
Thickness Variation ◽  
Seismic Load ◽  
Frequency Change ◽  
Shake Table Tests ◽  
Numerical Studies ◽  
Piping Systems ◽  
Earthquake Load ◽  
Steel Piping

This article presents the experimental and numerical studies of fatigue-ratcheting in carbon steel piping systems under internal pressure and earthquake load. Shake table tests are carried out on two identical 6 in pressurized piping systems made of carbon steel of grade SA333 Gr 6. Tests are carried out using similar incremental seismic load till failure. Wavelet analysis is carried to evaluate frequency change during testing. The tested piping systems are analyzed using iterative response spectrum (IRS) method, which is based on fatigue-ratcheting and compared with test results. Effect of thickness variation in elbow on strain accumulation is studied. Excitation level for fatigue-ratcheting failure is also evaluated and the details are given in this paper.

Low cycle fatigue and ductile fracture for Japanese carbon steel piping under dynamic loadings

1994 ◽  
Vol 153 (1) ◽  
pp. 57-69 ◽  
Author(s):  
Naoki Miura ◽  
Terutaka Fujioka ◽  
Koichi Kashima ◽  
Satoshi Kanno ◽  
Makoto Hayashi ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Ductile Fracture ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Dynamic Loadings ◽  
Steel Piping

Pressure Cycling Monitoring Helps Ensure the Integrity of Energy Pipelines

2010 ◽  
Author(s):  
Peter Song ◽  
Doug Lawrence ◽  
Sean Keane ◽  
Scott Ironside ◽  
Aaron Sutton
Keyword(s):  
Fatigue Life ◽  
Pipeline System ◽  
Outer Diameter ◽  
Operating Pressure ◽  
Potential Growth ◽  
Integrity Assessment ◽  
Pressure Cycling ◽  
Pressure Cycle ◽  
Primary Focus ◽  
Pump Stations

Liquids pipelines undergo pressure cycling as part of normal operations. The source of these fluctuations can be complex, but can include line start-stop during normal pipeline operations, batch pigs by-passing pump stations, product injection or delivery, and unexpected line shut-down events. One of the factors that govern potential growth of flaws by pressure cycle induced fatigue is operational pressure cycles. The severity of these pressure cycles can affect both the need and timing for an integrity assessment. A Pressure Cycling Monitoring (PCM) program was initiated at Enbridge Pipelines Inc. (Enbridge) to monitor the Pressure Cycling Severity (PCS) change with time during line operations. The PCM program has many purposes, but primary focus is to ensure the continued validity of the integrity assessment interval and for early identification of notable changes in operations resulting in fatigue damage. In conducting the PCM program, an estimated fatigue life based on one month or one quarter period of operations is plotted on the PCM graph. The estimated fatigue life is obtained by conducting fatigue analysis using Paris Law equation, a flaw with dimensions proportional to the pipe wall thickness and the outer diameter, and the operating pressure data queried from Enbridge SCADA system. This standardized estimated fatigue life calculation is a measure of the PCS. Trends in PCS overtime can potentially indicate the crack threat susceptibility the integrity assessment interval should be updated. Two examples observed on pipeline segments within Enbridge pipeline system are provided that show the PCS change over time. Conclusions are drawn for the PCM program thereafter.

Seismic Qualification of Piping Systems by Detailed Inelastic Response Analysis: Part 3 — Variation in Elastic-Plastic Analysis Results on Carbon Steel Pipes From the Benchmark Analyses and the Parametric Analysis

2017 ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Morishita ◽  
Masaki Shiratori ◽  
Tomoyoshi Watakabe ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Evaluation Procedure ◽  
Response Analysis ◽  
Seismic Load ◽  
Inelastic Response ◽  
Elastic Plastic ◽  
Analytical Results ◽  
Plastic Analysis ◽  
Piping Systems ◽  
Parametric Analyses

It is recognized that piping systems used in nuclear power plants have a significant amount of the safety margin, up to the point of boundary failure, even when the input seismic load exceeds the allowable design level. The reason is attributed to the large strength capacity of the piping systems in the plastic region. In order to establish an evaluation procedure, in which the inelastic behavior of piping systems is considered in a rational way, a task group activity under the Japan Society of Mechanical Engineers (JSME) has been conducted. As a deliverable of this activity, a Code Case in the framework of the JSME Nuclear Codes and Standards is now being developed. The Code Case provides the strain-based criteria, an evaluation procedure using the response-spectrum based inelastic analysis, and detailed inelastic response analysis based on a finite element model. For developing the Code Case, inelastic benchmark and parametric analyses of the tests of a pipe element and piping system made of carbon steel were conducted to investigate the variation of the elastic-plastic analyses results. Based on these analytical results, it is assumed that setting the yield stress has a significant influence on the inelastic analytical results, while the work hardening modulus in the bi-linear approximation of the stress-strain curve has little influence. From the results of the parametric analyses, it is confirmed that the variation in the analytical results among the analysts would be reduced by having a unifying analysis procedure. In this paper, the results of the parametric analyses and the variation in the elastic-plastic analysis are discussed.

scholarly journals Thermal Hydraulic Analysis of a Nuclear Reactor due to Loss of Coolant Accident with and without Emergency Core Cooling System

2020 ◽  
Vol 01 (02) ◽  
pp. 53-60
Author(s):  
Pronob Deb Nath ◽  
Kazi Mostafijur Rahman ◽  
Md. Abdullah Al Bari
Keyword(s):  
Nuclear Reactor ◽  
Cooling System ◽  
Computational Study ◽  
Reactor Core ◽  
Primary Circuit ◽  
Feed Water ◽  
Pressurized Water ◽  
Loss Of Coolant Accident ◽  
Loss Of Coolant ◽  
Core Cooling

This paper evaluates the thermal hydraulic behavior of a pressurized water reactor (PWR) when subjected to the event of Loss of Coolant Accident (LOCA) in any channel surrounding the core. The accidental break in a nuclear reactor may occur to circulation pipe in the main coolant system in a form of small fracture or equivalent double-ended rupture of largest pipe connected to primary circuit line resulting potential threat to other systems, causing pressure difference between internal parts, unwanted core shut down, explosion and radioactivity release into environment. In this computational study, LOCA for generation III+ VVER-1200 reactor has been carried out for arbitrary break at cold leg section with and without Emergency Core Cooling System (ECCS). PCTRAN, a thermal hydraulic model-based software developed using real data and computational approach incorporating reactor physics and control system was employed in this study. The software enables to test the consequences related to reactor core operations by monitoring different operating variables in the system control bar. Two types of analysis were performed -500% area break at cold leg pipe due to small break LOCA caused by malfunction of the system with and without availability of ECCS. Thermal hydraulic parameters like, coolant dynamics, heat transfer, reactor pressure, critical heat flux, temperature distribution in different sections of reactor core have also been investigated in the simulation. The flow in the reactor cooling system, steam generators steam with feed-water flow, coolant steam flow through leak level of water in different section, power distribution in core and turbine were plotted to analyze their behavior during the operations. The simulation showed that, LOCA with unavailability of Emergency Core Cooling System (ECCS) resulted in core meltdown and release of radioactivity after a specific time.

Load Factor for Evaluating Non-Planar Flaws in Carbon Steel Piping Using Limit Load Methodology

2016 ◽  
Author(s):  
Phuong H. Hoang
Keyword(s):  
Carbon Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Pipe Wall ◽  
Local Strain ◽  
Limit Load ◽  
Evaluation Methodology ◽  
Load Factor ◽  
Wall Thinning ◽  
Steel Piping

Non-planar flaw such as local wall thinning flaw is a major piping degradation in nuclear power plants. Hundreds of piping components are inspected and evaluated for pipe wall loss due to flow accelerated corrosion and microbiological corrosion during a typical scheduled refueling outage. The evaluation is typically based on the original code rules for design and construction, and so often that uniformly thin pipe cross section is conservatively assumed. Code Case N-597-2 of ASME B&PV, Section XI Code provides a simplified methodology for local pipe wall thinning evaluation to meet the construction Code requirements for pressure and moment loading. However, it is desirable to develop a methodology for evaluating non-planar flaws that consistent with the Section XI flaw evaluation methodology for operating plants. From the results of recent studies and experimental data, it is reasonable to suggest that the Section XI, Appendix C net section collapse load approach can be used for non-planar flaws in carbon steel piping with an appropriate load multiplier factor. Local strain at non-planar flaws in carbon steel piping may reach a strain instability prior to net section collapse. As load increase, necking starting at onset strain instability leads to crack initiation, coalescence and fracture. Thus, by limiting local strain to material onset strain instability, a load multiplier factor can be developed for evaluating non-planar flaws in carbon steel piping using limit load methodology. In this paper, onset strain instability, which is material strain at the ultimate stress from available tensile test data, is correlated with the material minimum specified elongation for developing a load factor of non-planar flaws in various carbon steel piping subjected to multiaxial loading.

Fracture properties evaluation of carbon steel piping for main steam line

1995 ◽  
Vol 158 (2-3) ◽  
pp. 241-251 ◽  
Author(s):  
Y.J Kim ◽  
C.S Seok ◽  
Y.S Chang ◽  
J.O Kim ◽  
K.M Yang ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Steam Line ◽  
Fracture Properties ◽  
Main Steam Line ◽  
Main Steam ◽  
Steel Piping
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