bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experience of Work for Replacing Reactor Recirculation Piping in Narrow Space of MARK-I Containment Vessel
Authors: Shiraki Keisuke , Taniguchi Akira , Fujino Takushi , Nakama Shouhei , Suzuki Osamu , Kobayashi Hiroyuki 
Published: November 2014

Tsuruga unit-1, the first Japanese commercial BWR (BWR-II, 357MWe) started its operation in 1970, has a Mark-I type containment vessel and 3-loop reactor recirculation piping.
In the 33rd planned outage of 2011, most parts of the reactor recirculation piping were replaced to improve corrosion resistance and inspectability. This replacement work dealing with long pipe pieces had to be conducted in limiting condition and severe environment such as the narrow work space, only one small entrance hatch, and high dose rate. In addition, other maintenance works by four contractors were concurrently being carried out in the same area. Therefore, these work processes in the containment vessel were controlled carefully through close coordination with contractors and using advanced construction technique. As a result, it was achieved that efficient process which contributed to shortening work period and injury-free work in this challenging environment and condition.
Regarding radiation management, radiation dose rate was reduced substantially by applying chemical decontamination using ozone as chemical agent.
Experience obtained from this work is valuable in the current situation that many operators are trying to operate their aging nuclear plants continuously as long as economically viable.
Semianalytical Method for the SIF Calculation for a Crack of Arbitrary Shape in Infinite Body
Authors: Batura Anatolii , Orynyak Igor , Oryniak Andrii 
Published: November 2014

The exact analytical approach for stress intensity factor calculation for an arbitrary shape mode I crack loaded by the polynomial stresses is proposed. The approach is based on the calculation of the crack faces displacement at given loading. The displacement field is presented as a shape function multiplied by an adjustment polynomial. At that the key problem is the solution of well-known inverse task: obtaining the stresses field at the crack faces on the base of a given displacements field. Multiply solution of such task for a whole set of certain displacements base functions (e.g., for the single terms of the adjustment polynomial) allows to get analytical expression which connects stresses and displacements fields.
The original semi-analytical technique for integration with subsequent differentiation of well-known singular integral equation of the flat crack problem is developed. The excellent accuracy of the method is confirmed for an elliptic crack as well as for a rectangular one in the infinite 3D body. New results are given for an inner semi-elliptic crack in the infinite body which surfaces are loaded by polynomial stresses up to the 6th order. The importance of choosing the appropriate shape function is demonstrated.
Development of an Automatic 3D Finite Element Crack Propagation System
Authors: Doi Hiroaki , Nakamura Hitoshi , Gu Wenwei , Okada Hiroshi 
Published: November 2014

When cracks are detected in piping in nuclear power plants during in-service inspections, the crack propagation is usually calculated using approximation formulas of stress intensity factor (SIF) provided in the ASME Code, the JSME Rules or the literature. However, when the crack is detected in complicated-shaped locations in components, finite element analysis (FEA) needs to be used to calculate the SIFs. Accordingly, a method of automatically conducting FEA for crack propagations in nuclear power plants is needed. Therefore, we, the Nuclear Regulation Authority (NRA, Japan) have developed an automatic 3D finite element crack propagation system (CRACK-FEM) for nuclear components. The developed CRACK-FEM uses three methods of SIF calculation: the Virtual Crack Extension Method (VCEM), the Virtual Crack Closure-Integral Method (VCCM) and the Domain Integral Method (DIM). Each method uses different meshes, so users can select a method which uses a suitable mesh for the problem. The software includes a geometry generator to create complicated weld models, and a mesh generator which can deal with interior boundaries formed between different materials. The functions and accuracy of the new software are demonstrated by solving several sample problems involving crack propagation.
The contents of this paper were conducted as a research project of the Japan Nuclear Energy Safety Organization (JNES) when one of the authors (Doi) belongs to JNES. After this project, JNES was abolished and its staff and task were absorbed into NRA on March 1, 2014.
Treatment of Stresses Exceeding Material Yield Strength in ASME Code Section XI Appendix G Fracture Toughness Evaluations
Authors: Mehta Hardayal S. , Stevens Gary L. , Sommerville Daniel V. , Benson Michael , Kirk Mark , Griesbach Timothy J. , Kusnick Joshua 
Published: November 2014

A previous PVP paper [1] identified suggested improvements to be made to ASME Code, Section XI, Nonmandatory Appendix G, “Fracture Toughness Criteria for Protection Against Failure” [2]. That paper also identified that the current version of Appendix G does not have any provisions for when the calculated operating stress (pseudo stress) exceeds the material yield strength. The treatment of stresses exceeding yield was included in earlier versions of Appendix G, but it was removed via Code Action ISI-94-40 in 1995. The specific reasons for removal of these provisions were not documented.
In some Appendix G postulated flaw evaluations for pressure-temperature (P-T) limits, the calculated total linear-elastic (or pseudo) stress (i.e., including the primary stress due to pressure loading and thermal stress) may exceed the material yield stress. The ASME Section XI Working Group on Operating Plant Criteria (WGOPC) decided that this provision needed to be more fully considered, with appropriate benchmarking and possible adjustments to Appendix G made consistent with the current state of knowledge in elastic-plastic fracture mechanics (EPFM) methods. This is appropriate since the state of knowledge in EPFM has significantly advanced since the time the technical basis for Appendix G was established, as documented in Welding Research Council (WRC) Bulletin No. WRC-175, which was published in 1972. Furthermore, EPFM provides an improved method for evaluating the effects of high stresses.
This paper describes the results of preliminary investigations of stresses exceeding the material yield stress in fracture toughness assessments associated with Appendix G. Also included in the technical evaluations presented are the temperature conditions for which upper shelf conditions are present and where EPFM methods are applicable.
Comparison of Probabilistic Fracture Mechanics Evaluations for a Through-Wall Cracked Pipe Under the STYLE Project
Authors: Sharples John , Madew Colin , Radu Vasile , Budden Peter 
Published: November 2014

One of the large scale mock-up experiments (Mock-Up 2) of the recent STYLE European project was a ductile fracture test carried out on a pipe containing a circumferential through-wall crack located in a repair weld and loaded under four-point bending. This experiment has been used as a basis for undertaking a comparative probabilistic fracture mechanics benchmark study by a number of the organisations participating in STYLE.
In launching the benchmark study, the pipe and crack dimensions were specified as fixed values, applied bending stress (moment) was considered as a deterministic variable and three values were taken for weld residual stress (assuming constant membrane values). Tensile and fracture toughness material properties were considered to be random variables and these were specified by log-normal distribution parameter values. In undertaking their evaluations, the participants were asked to evaluate J-integral versus applied bending moment, probability of crack growth initiation versus applied bending moment, probability of net-section collapse versus applied bending moment and carry out various sensitivity analyses.
This paper focuses mainly on the contribution to the benchmark study primarily based on the R6 methodology and includes examples of contributions provided using other methods.
Statistical Analyses of High Cycle Fatigue French Data for Austenitic SS
Authors: Blatman Géraud , Métais Thomas , Le Roux Jean-Christophe , Cambier Simon 
Published: November 2014

In the 2009 version of the ASME BPV Code, a set of new design fatigue curves were proposed to cover the various steels of the code. These changes occurred in the wake of publications [1] showing that the mean air curve used to build the former ASME fatigue curve did not always represent accurately laboratory results.
The starting point for the methodology to build the design curve is the mean air curve obtained through laboratory testing: coefficients are then applied to the mean air curve in order to bridge the gap between experimental testing and reactor conditions.
These coefficients on the number of cycles and on the strain amplitude are equal to 12 and 2 respectively in the 2009 ASME BPV code, using the mean air curve proposal from NUREG/CR-6909 [1]. Internationally, with the same mean air curve, other proposals have emerged and especially in France [2]-[3] where a consensus seems to be reached on the reduction of the coefficient on strain amplitude.
This paper provides statistical analyses of the experimental data obtained in France at high-cycle for austenitic stainless steels. It enables to bring arguments for the selection of a coefficient on strain amplitude in the French RCC-M code, where less scatter on the data is witnessed due to fewer material grades.
Cleavage Crack Propagation and Arrest Prediction in French PWR Vessel Steel
Authors: Yang Xiaoyu , Marie Stéphane , Bompard Philippe , Jacquemoud Clémentine 
Published: November 2014

The integrity assessment of Reactor Pressure Vessels is mainly based on crack initiation. Nevertheless, in the frame of component life extension, crack arrest conception is investigated.
This paper presents a local non-linear dynamic model to predict the propagation and arrest of cleavage crack in French PWR vessel steel (16MND5). The propagation criterion used in this model is a Ritchie Knott and Rice (RKR) fracture stress criterion: the crack propagates when the maximum stress ahead of crack tip reaches a critical level, which has been shown to depend on temperature and plastic strain rate.
In the first step, the criterion has been identified from crack growth and arrest analysis on CT specimens at different temperatures. Then it was applied to predict the propagation and arrest of cleavage cracks on pre-cracked rings under mixed mode loading, at three different temperatures: −150°C, −125°C and −100°C.
2D modeling was performed by using extended element method (XFEM) in CAST3M software. The propagation direction on pre-crack rings under mixed mode loading was determined from maximum hoop stress criterion. Numerical computation showed a good agreement with experiments, for both curved crack paths and crack arrest locations. Furthermore it showed that crack paths and crack arrest also depend on the level of the crack loading at initiation.
Nuclear Regulatory Commission Staff View of Progress in the Nondestructive Testing of Cast Austenitic Steel Components
Authors: Cumblidge Stephen E. 
Published: November 2014

Welds in cast austenitic steels (CASS) are very challenging to inspect using the current American Society for Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section XI requirements. Supplement 9 of ASME Boiler and Pressure Vessel Code Section XI, Appendix VIII is still in the course of preparation, requiring inspectors to use ASME Code Section XI, Appendix III, which provides prescriptive ultrasonic testing (UT) requirements that are significantly less rigorous than UT techniques that have been demonstrated under Appendix VIII. The inability of licensees to demonstrate that the welds in CASS components meet ASME Code requirements has been an ongoing area of concern for the NRC staff. The lack of a reliable inspection method for welds in CASS materials has led to hundreds of relief requests over the past four decades. While no degradation mechanism has been found in CASS components to date, there is no guarantee that a new degradation mechanism affecting CASS welds will not emerge as nuclear power plants go beyond forty years of operation. Licenses need qualified procedures and personnel for the inspection of welds in CASS materials in order to put licensees into compliance with ASME Code, meet federal regulations, reduce the number of needed relief requests, and ensure the structural integrity of their welds.
Over the past decade there have been significant developments in nondestructive examination (NDE) technology. The use of encoded phased array techniques using low frequency ultrasound has been shown to be able to reliably find flaws greater than 30% through wall in CASS materials with a variety of microstructures. Additionally, an improved understanding of the fracture mechanics of CASS components is being developed that shows the flaw sizes that can be tolerated in CASS components. These advances in NDE techniques and fracture mechanics theory are converging on a path to allow for qualifications of procedures and personnel for the ultrasonic inspections of welds in CASS components.
Recent developments in ASME Code includes Code Case N-824, which provides guidance on the examination of CASS materials based on the advances in NDE technology and an improved understanding of the NDE techniques capable of finding flaws in CASS components as well as Code Case N-838 for flaw tolerance evaluations of CASS piping components. Finally, work on ASME Code Section XI Supplement 9 is progressing, with several important issues still to be addressed. The NRC staff sees a clear path forward and is working to ensure that qualified inspections of welds in CASS materials will be possible in the future.
Use of Laser Measurement Systems for Out-of-Roundness Check of ASME BVP Section VIII Div.1 Pressure Vessels
Authors: Millet Barry , Di Lillo Patrizio , Whipple Richard , Kirkpatrick Kenneth , Miller George 
Published: November 2014

Since the 1956 Edition of the ASME Boiler and Pressure Vessel Code Section VIII (ASME B&PV Code) [1], the Out-of-Roundness of circular sections of pressure vessels subject to external pressure have been inspected using a segmental template per paragraph UG-80(b)(2). Newly approved ASME Code Case 2789 “Laser Measurement for Out-of-Roundness Section VIII, Division 1” to the ASME B&PV Code expands the out of roundness checking to allow the use of laser measurement systems. Today with large vessels approaching 60 feet (18.2 m) in diameter, laser measuring systems allow an expeditious and cost effective method of inspection for out-of-roundness.
The Code Case allows the fabricator to use measurements obtained from laser measuring to either verify the vessel in the arc segments or the entire vessel circumference is held to a circularity tolerance. The second option is similar to the requirements of European Standard EN 13445 (EN 13445) [2] which uses circularity.
This paper will explore the origin and objective of the template and presents how laser measuring systems make use of the latest technology available to check for out-of-roundness. The paper will address laser measuring systems, procedures for taking measurements, and processing of the data into a format that can be verified by Authorized Inspectors.
Simple Model for Bubble-Wall Interaction
Authors: Pelletier Etienne , Beguin C. , Etienne S. 
Published: November 2014

We have developed a model for an ellipsoidal bubble colliding with a rigid horizontal wall based on potential flow theory. The model is then compared with experiments of air bubbles surrounded by water impacting a wall. 70 impacts were observed with bubble radius between 0.3 and 2 mm and different trajectory types (helicoidal, zig-zag). Deformation and height of the first impact are the main comparison points. The proposed model is in good agreement with the height of the rebound but tends to overestimate the maximal compression for both types of trajectories.
We also propose a new relation for the viscous drag coefficient correction induced by the wall confinement as well as the definition of potential pressure forces acting on bubbles close to a wall.
Simplified Methodology for Analysis of Reflected Detonation and DDT: Part 2 — Elastic-Plastic Analysis
Authors: Ligon Thomas C. , Gross David J. , Minichiello John C. 
Published: November 2014

This paper applies a simplified conservative approach for analyzing elastic-plastic response of piping due to reflected gaseous detonations and deflagration-to-detonation transitions (DDT). A consequence associated with gaseous explosions is the potential for DDT to occur near the end of a closed pipe or gas pocket. As an accelerating deflagration flame approaches a closed end, the unburned fuel ahead of the flame front is compressed to an elevated initial pressure. This process is often referred to as pressure piling or pre-compression, and the combination of detonation reflection with the elevated initial pressure can produce extremely high peak pressures and large values of impulse. In this paper, the event where DDT occurs immediately ahead of the reflecting surface is referred to as a reflected-DDT (R-DDT). Due to the extreme pressures that R-DDTs can achieve, the piping can frequently experience elastic-plastic deformation.
In this second part, the pressure time-history modeling methodology developed for elastic response in part one is extended to elastic-plastic analysis. The inelastic response of the piping material is modeled using a lower-bound strain hardening curve at a single representative strain rate. The pressure model is compared to a published reflected detonation pressure model for the stoichiometric mixture of ethylene and oxygen, and finite-element analysis results using the simplified methodology are compared to two recent sets of published plastic deformation data from ethylene oxygen explosion tests in austenitic stainless steel tubing and piping.
Fatigue of Stainless Steel in Simulated Operational Conditions: Effects of PWR Water, Temperature and Holds
Authors: Solin Jussi , Reese Sven , Karabaki H. Ertugrul , Mayinger Wolfgang 
Published: November 2014

Our experimental research on fatigue performance of stainless steels and transferability of laboratory data to plant operational conditions focuses in niobium stabilized stainless steel (1.4550, X6CrNiNb1810mod) taken from a pipe manufactured as primary piping for a German NPP Good fatigue performance both in air and in PWR water was reported in previous PVP papers.
The NUREG/CR-6909 report proposes Fen factors based on stroke controlled experiments in hot water for non-stabilized steels. Since PVP2013-97500 we have new data in 200°C PWR water to compare with predictions by NUREG/CR-6909. Our strain controlled tests in 325°C and 200°C PWR water give longer lives resp. smaller Fen factors. For the slowest tested strain rate 4·10−6 in 325°C water the prediction according to NUREG/CR-6909 goes just below the current ASME design curve, but our results remains well above. Including also the relevant design temperature effect, our result Fen = 4 is well below the predicted Fen = 14,5. The gap is smaller for higher strain rates and low Fen values.
Simplified simulations of fatigue transients combined with normal operation indicated that relevant loading patterns as hold-time effects may result to notably longer lives than in standard laboratory tests. A concern was raised on transferability of data to thermal transients separated with months of normal operation. Cyclic strain (transients) followed by hot holds (normal operation) lead to time and temperature dependent hardening with reduction in cyclic plastic strain and fatigue usage, i.e. extension of life.
This paper reports new data, challenges met and our progress towards developing realistic design factors for effects both reducing and extending fatigue endurance in nuclear power plant operational conditions.
Presentation of the 2014 Revisions to the RCC-M Code
Authors: Malouines Philippe 
Published: November 2014

The paper describes the general approach followed by AFCEN, the French Society for Codified Rules for Design, Construction and In-Service Inspection of Nuclear Island Components, from the technical and organizational points of view. The RCC-M code, reissued in 2012 and modified with addenda in 2013 and 2014, is presented. The main new topics of activity of the RCC-M Subcommittee are considered: conformity with regulation(s), use of International Standards, equivalence with other codes and harmonization, and new requirements for the quality management system.
The paper highlights how industrial experience is currently being integrated into the RCC-M code, and how the code is evolving to take into account the enlargement of the AFCEN Membership, new AFCEN organization rules, and the international environment, and best practices. The processes for dealing with requests for modifications and interpretations are described.
Estimates of J and COD for Complex-Cracked Pipes Based on FE Analyses and ERS Method
Authors: Jeong Jae-Uk , Choi Jae-Boong , Huh Nam-Su , Kim Yun-Jae 
Published: November 2014

A complex crack can occur at the dissimilar metal weld parts of nuclear pipes due to stress corrosion cracking. The fracture behavior of such crack is different with those of a simple through-wall crack. Thus, the engineering estimation equations for predicting the fracture mechanics parameters, i.e. crack opening displacement and J-integral, should be newly provided in order to evaluate the leak-before-break of pipe including complex cracks.
In the previous research, an engineering scheme using reduced thickness analogy was suggested to calculate the crack opening displacement and J-integral for complex cracked pipes. However, this method has limitations in the sense that a through-wall crack is assumed to be developed only in the circumferential direction, and the effect of crack closure cannot be considered. Another scheme for complex cracked pipes is the enhanced reference stress method considering crack closure effect by suggesting the optimized reference load for complex crack geometry. It presented the more accurate results compared to previous engineering estimation scheme. However, an elastic component of crack opening displacement and J-integral were calculated by assuming the crack shape as the simple through-wall crack due to the absence of engineering solutions for complex-cracked pipes.
In this context, finite element based evaluation of fracture parameters was performed to confirm the validation of previous estimation schemes. Moreover, the variations of crack opening displacement and J-integral according to a change of surface crack depth ratio of complex crack are systematically investigated based on detailed 3-D finite element analyses. Furthermore, enhanced reference stress method considering finite element based elastic values from the complex-cracked pipe models is assessed to overcome the limitation of previous enhanced reference stress approach.