bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissimilar Metal Weld Pipe Fracture Testing: Analysis of Results and Their Implications
Authors: Rudland D. , Lukes R. , Scott P. , Olson R. , Cox A. , Shim D.-J. 
Published: August 2013

Typically in flaw evaluation procedures, idealized crack shapes are assumed for both subcritical and critical crack analyses. Past NRC-sponsored research have developed estimation schemes for predicting the load-carrying capacity of idealized cracks in nuclear grade piping and similar metal welds at the operating conditions of nuclear power reactors. However, recent analyses have shown that growth of primary water stress corrosion cracks (PWSCC) in dissimilar metal (DM) welds is not ideal; in fact, very unusual complex crack shapes may form, i.e., a very long surface crack that has a finite length through-wall crack in the same plane. Even though some experimental data on base metals exists to demonstrate that complex shaped cracks in high toughness materials fail under limit load conditions, other experiments demonstrate that the tearing resistance is significantly reduced. At this point, no experimental data exists for complex cracks in DM welds. In addition, it is unclear whether the idealized estimation schemes developed can be used to predict the load-carrying capacity of these complex-shaped cracks, even though they have been used in past analyses by the nuclear industry. Finally, it is unclear what material strength data should be used to assess the stability of a crack in a DM weld.
The NRC Office of Nuclear Regulatory Research, with their contractor Battelle Memorial Institute, has concluded an experimental program to confirm the stability behavior of complex shaped circumferential cracks in DM welds. A combination of full-scale pipe experiments and a variety of laboratory experiments were conducted. A description of the pipe test experimental results is given in a companion paper. This paper describes the ongoing analyses of those results, and the prediction of the load-carrying capacity of the circumferential cracked pipe using a variety of J-estimation scheme procedures. Discussions include the effects of constraint, appropriate base metal material properties, effects of crack location relative to the dissimilar base metals, and the limitations of the currently available J-estimation scheme procedures. This paper concludes with plans for further development of J-estimation scheme procedures for circumferential complex cracks in DM welds.
High-Accuracy Analysis Methods of Fluid Temperature Fluctuations at T-Junctions for Thermal Fatigue Evaluation
Authors: Qian Shaoxiang , Kanamaru Shinichiro , Kasahara Naoto 
Published: August 2013

T-junctions are widely used for fluid mixing in nuclear power and process plants. Temperature fluctuations generated by the mixing of hot and cold fluids at a T-junction can cause thermal fatigue failure. The existing method for evaluating thermal fatigue leads to an over-conservative evaluation in part. CFD/FEM coupling analysis is a useful tool for the more rational evaluation of thermal fatigue.
The present paper aims to verify another high-accuracy difference scheme used for simulating fluid temperature fluctuations at T-junctions for rational evaluation of thermal fatigue. In addition to the high-accuracy numerical methods presented in the previous paper, the TVD 2nd-order upwind difference scheme (2UD) is also used for the CFD analysis. In the present simulation, the TVD 2UD scheme is only applied to calculate the convective term of the energy equation to facilitate the comparison with the previous simulation.
For comparison, the simulation conditions including the geometry of T-junction are the same as those in the experiments in the literature. The simulation results for distributions of time-averaged fluid temperature are very close to the experimental and previous simulation results. Especially, the predicted results of fluid temperature fluctuations of our concern also agree with the experimental and previous simulation results very well. The simulation results indicate that the TVD 2UD scheme is also a high-accuracy numerical method for the simulation of unsteady phenomena, along with the hybrid scheme.
Cleavage Dynamic Propagation Analysis in a Nuclear Reactor Pressure Vessel Steel Using a High-Speed Camera
Authors: Bousquet Amaury , Marie Stéphane , Bompard Philippe 
Published: August 2013

Initiation stage of cracks is considered as a key issue, but more and more component integrity analyses investigate the crack propagation and arrest possibility. This study deals with physical mechanisms of cleavage crack propagation and numerical computations related to brittle fracture. Dynamic effects, involved in unstable cleavage crack propagation, have to be taken into account to properly depict brittle crack propagation, arrest and possible propagation re-initiation events.
Experiments were carried out on thin CT specimens made of 16MND5 PWR vessel steel at five temperatures (−150°C, −125°C, −100°C, −75°C, −50°C). In addition to standard crack gages, an innovative experimental technique has been used to determine crack propagation. By the means of developments on the experimental protocol (improvements of isolation and airtightness of the thermal chamber, optimization of the experimental protocol to eliminate ice in the thermal chamber and in order to have a good acquisition quality), use of a high-speed framing camera was made possible to measure crack propagation on a CT mirror polished surface. This optical device, combined with this optimized experimental process, has allowed the study of straight and branching crack paths with high accuracy. The framing camera (520 000 fps up to 1 100 000 fps) has allowed to have a very accurate estimation of crack speed even up to 1000 m.s−1 and also to detect some phases of crack branching during propagation and phases of arrest-re-initiation. Numerical computations, based on X-FEM and combining a local non linear dynamic approach with a RKR type fracture stress criterion, have been performed to depict experimental crack behavior.
This paper describes this innovative experimentation and the interpretation by FE calculations and SEM observations associated with quantitative 3D optical microscopy.
Benchmarking xLPR Version 1.0 With the PRO-LOCA Version 3.0 Code
Authors: Kurth Robert , Kurth Elizabeth , Young Bruce , Cox Andrew , Olson Rick , Scott Paul , Rudland Dave , Iyengar Raj , Harrington Craig 
Published: August 2013

The US Nuclear Regulatory Commission (NRC) in conjunction with the US nuclear power industry under the leadership of the Electric Power Research Institute (EPRI) is developing a new probabilistic fracture mechanics (PFM) code as a means of demonstrating compliance with the 10CFR50 Appendix A, General Design Criterion 4 (GDC-4) requirement that primary system piping exhibit an extremely low probability of rupture. This PFM code, called xLPR (eXtremely Low Probability of Rupture) will be comprehensive by addressing all aspects of the problem, i.e., crack initiation, growth, stability, surface crack detection and leakage detection.
Previously, the NRC, along with two of its contractors, Battelle Memorial Institute and Engineering Mechanics Corporation of Columbus (Emc2), developed a probabilistic fracture mechanics code called PRO-LOCA[1] which was to have been used as a tool for re-evaluating the break frequency versus break size curves developed as part of the technical basis for the transition break size as part of the redefinition of the emergency core cooling system (ECCS) requirements in 10CFR50.46. PRO-LOCA was subsequently developed as part of an international cooperative research program led by Battelle called MERIT (Maximizing Enhancements in Risk-Informed Technology). Today PRO-LOCA is being further developed as part of another international cooperative program called PARTRIDGE (Probabilistic Analysis as a Regulatory Tool for Risk-Informed Decision GuidancE). The focus of this paper is three-fold. First, the relationship between PRO-LOCA and xLPR will be described. Secondly, the enhancements being made to PRO-LOCA will be discussed and compared to xLPR development. Finally, the results of some comparative cases where PRO-LOCA (Version 3.0) was benchmarked against xLPR (Version 1.0) are provided.
Influence and Modeling of Residual Stresses in Thick Walled Pressure Vessels With Through Holes
Authors: Troiano E. , Parker A. P. , Izzo J. H. 
Published: August 2013

Thick walled pressure vessels are often autofrettaged in order to impart favorable near bore compressive residual stresses which can significantly increase the life of the vessels. These stresses can be imparted via a thermal shrink process in which there is no loss of residual stresses due to the Bauschinger Effect, or more economically with a mechanical swage or hydraulic overload process in which the Bauschinger Effect is present.
In some cases these vessels have holes bored through the wall in order to take advantage of the escaping gasses for actuation of external peripherals associated with the vessel. These through holes, which can be angled or perpendicular to the centerline of the pressure vessel can significantly reduce the fatigue life of the vessel depending on the wall ratio of the vessel as well as the, angle of inclination of the hole to the centerline of the vessel.
This study utilizes the classic stress based Paris Law fatigue life approach which takes into account the residual stresses as a function of radial location to assess the life of the vessel in the region of both configurations of through holes. It quantifies the concentration of stresses associated with the perpendicular and angled through wall holes, and the amount of pressure that actually enters the hole. The analysis is employed to ensure that the life within these through holes meets or exceeds the safe life of the vessel without holes which has been determined by assuming a log normal distribution from of a sample size of six with the 90% lower confidence bound on the 0.1th percentile of the population.
Investigation on Developing Seismic Safety Evaluation Method Using Elasto-Plastic Analysis
Authors: Nakamori Tomohito , Kojima Nobuyuki , Ueda Yuya , Shimizu Hiroshi , Monde Masatsugu , Okamoto Hiromu , Ikeda Kazutoyo , Hosotani Terushige , Matsuzaki Daichi , Ishihama Kiyoshi 
Published: August 2013

As seismic motion level for seismic resistant designing has been increased, usual tolerance is no longer enough in the existing domestic PWR and BWR plants.
In this study, the authors had an eye on devices supported by four legs in the existing domestic PWR and BWR plants, and established a reasonable earthquake-proof evaluating safety method compared to the original method (JEAG4601.that is earthquake resistant design code for nuclear plants in Japan).
This was done by establishing an analytical method which premises elasto-plastic deformation of the support legs that do not associated with device’s function maintenance.
At first, the support leg’s configuration of the devices supported by four legs in the existing plants was organized, and for the typical legs, the elasto-plastic behavior of support leg itself was verified by element test. Then the authors have established an analytical method that would simulate with result in element test.
Secondly, main configuration (including support leg configuration) of the practical device was organized, and for the typical devices the elasto-plastic behavior of the practical test object was verified by seismic excitation test. Then, the authors have established an analytical method that would simulate with result in seismic excitation test.
By implementing the established analytical method to a few practical devices supported by four legs in the existing domestic PWR and BWR plants, this analytical method was a reasonable method compared to the original standard.
Justification for a New Industry Standard for Torque Wrench Calibration
Authors: Hamilton Scott R. , Smith Thomas J. 
Published: August 2013

In most cases, it is assumed that a manual or hydraulic torque wrench will deliver the requested torque value if set correctly. However, torque wrenches have moving parts that will be subject to wear. They are also subject to harsh operating conditions in the field, which elevates the risk of damage. Calibration is the measurement of a device’s output to a known standard and adjustment to within specific tolerances if necessary.
There are several different codes and standards that are followed in the industry, but these practices are normally left up to interpretation. Common sense tells us calibration of torque wrenches on a periodic basis would be advisable. Many in the industry have different policies that are inconsistent when considering several factors of a calibration program. This may be because there is not data available to justify the cost of such a calibration program or misconceptions on what calibration is and when it should be completed. An analysis of the data reveals exactly why regular, periodic calibration of torque wrenches should be an important part of any maintenance program. By using certain methods of calibration, one can mitigate the risk of an un-calibrated torque wrench affecting one’s facility. This paper includes general trends for a sample of torque wrenches that received calibration in order to compare the overall accuracy of the wrenches prior to calibration versus post-calibration. The study was conducted on data obtained from the calibration of hundreds of wrenches over a five year period. This may be considered a reasonable snap-shot of the inaccuracy of torque wrenches that may be expected in the field if recent calibration has not been performed.
Due to the highly prevalent misconceptions regarding calibration found in the petrochemical and oil industry, there needs to be an industry standard for torque wrench calibration. Our hypothesis for this paper states that each torque wrench that is used in the field, whether it is new, used, or repaired, shall have an individual calibration performed at no less than a 12 month interval. This standard will prevent material damage to the installation and operation of equipment by correcting both slight deviations from accuracy tolerances and, especially, extreme outliers. The material presented in this paper will show justifcation of an industry standard that should be adopted.
Design and Baseline Testing of Motor Operated Valves (MOVs) for Generation 3+ Nuclear Power Generating Plants
Authors: Hobbs Matthew E. , Gradle Richard J. , Bensinger Floyd A. 
Published: August 2013

Flowserve is supplying motor operated valves (MOVs) to Generation 3+ nuclear power plants. These valves have been custom designed to meet the design and qualification criteria for ASME Section III, Class 1 nuclear service. To support plant operations, the valve designs benefit from the lessons learned from US NRC Generic Letter 89-10, “Safety-Related Motor-Operated Valve Testing and Surveillance”, the subsequent MOV testing programs, the Joint Owners Group (JOG) MOV Periodic Verification Program and ASME QME-1 functional qualifications.
As a result, some new MOV designs are larger and heavier than typical valves of corresponding size and pressure class supplied to existing nuclear power plants.
During the valve functional testing portion of valve manufacturer’s production testing, each MOV assembly is instrumented to record stem thrust and torque, position, motor operator voltage and current draw, and limit switch and torque switch function. The data are digitally recorded for further review and acceptance. The baseline data will allow the end user to confirm proper MOV installation and setup. The baseline data can also be compared to future in-situ test data to evaluate potential performance degradation during the nuclear power plant operation.
This paper discusses:
• MOV design parameters and design features
• The production testing to establish and record MOV baseline functional data and
• ASME QME-1-2007 qualification of these MOVs
Material Characterization and Modeling Within Safety Analysis of Packages for Transport of Radioactive Material
Authors: Neumann Martin , Ballheimer Viktor , Sterthaus Jens , Schubert Sven , Eisenacher Germar , Wille Frank 
Published: August 2013

In mechanical design safety assessment of packages for the transport of radioactive material the International Atomic Energy Agency (IAEA) regulations [1, 2] require the use of one of four methods of demonstration of compliance with regulations: tests with prototypes, reference to previous satisfactory demonstrations, tests with scaled models as well as calculation or reasoned argument. In all cases characterization of material behavior is necessary. The need for material characterization can be split into three groups: characterization for material modeling in the design and verification process, determination of assessment criteria and inspections during manufacturing.
The paper deals primarily with material characterization for the material modeling in the design phase and authorities approval process. Main package components are discussed: cask body and lids, screws, trunnions, impact limiter and basket (structure holding the content in specified position). Depending on the material used for these components this paper shows exemplary a possible set of material investigations in order to allow modeling in design and assessment during the approval process.
Development of Material Model Parameters Suitable for the Finite Element Simulation of Ferritic Welds
Authors: Bate Steve , Shallcross Neil , Stone Karen , Francis John , Mark Alison , Gill Chris 
Published: August 2013

The prediction of residual stresses in ferritic welds using finite element techniques requires materials properties to describe the thermal, tensile, cyclic and phase transformation behaviour that the material undergoes during welding and also during creep as the effect of post weld heat treatment is also of interest. Ferritic steels will transform at a temperature above about 850°C to austenite. As the steel is cooled, a further phase transformation in the structure occurs. The precise structure formed depends on the detailed chemical make-up of the steel and on the rate at which it is cooled. On slow cooling from above 850°C a pearlite-ferrite microstructure is formed. On more rapid cooling, other microstructures, particularly bainite at intermediate cooling rates and martensite at the highest cooling rates are formed. Predicting the phase on cooling requires a Continuous Cooling Transformation diagram that is suitable for welding thermal cycles and reflects the time spent above the austenitisation threshold which influences the austenitic grain size formed and subsequently the phase of material on cooling. Material properties for a SA508 Grade 3 steel and a low carbon SD3 filler metal have been generated and fitted to constitutive models that are available in the finite element codes ABAQUS and SYSWELD. The choice of hardening model and its associated parameters have been evaluated on the basis of the observed cyclic behaviour in materials testing. Validation of these models has then been carried out by finite element simulations of welded mock-ups which have been measured using neutron diffraction. These include an autogenous weld beam and groove weld specimens containing up to eight weld passes. The rationale for using these simple specimens has been to:
• Validate the capability of the model to predict the correct phase transformation behaviour and resulting stresses.
• Account for the different behaviour of the parent and filler material.
• To develop the capability for representing the material cyclic behaviour.
On the basis of these simulations recommendations have been made on the material models (and their parameters) that may be used for the finite element simulation of the welding process.
The Sealing Characteristics of Bolted Flanged Connection With Metal Gasket
Authors: Kondo Koji , Sawa Toshiyuki , Sato Koji , Kikuchi Tsutomu , Tsubaki Shota 
Published: August 2013

Metal gaskets have been used in bolted flanged connections under high pressure and high temperature conditions. However, it is difficult to estimate an amount of leakage from the metal contact interfaces in the connections. Recently, it has been noticed that a tiny leakage occurs from the gasket interfaces in bolted flanged connections. Thus, it is necessary to study on the sealing characteristics of the metal to metal contact gasket in the connections under internal pressure and high temperature.
In the present paper, for clarifying the characteristic of the metal gaskets, some experiments were conducted at room temperature. The gaskets are used aluminum, copper and mild steel flat gaskets. Firstly, according to JIS B 2490, the sealing behavior was measured taking account the surface roughness of the metal gaskets. The gaskets were compressed using a material testing machine while the amount of leakage was measured. Secondly, the amount of leakage was measured for bolted flanged connections with metal gaskets. The flange nominal diameter used was 2″. Finally, the contact gasket stress distributions in the connection were analyzed using 3-D FEM analysis. Using these results, discussion was made on the sealing behavior of the metal gaskets. In the result, it is found that plastic strain is important for the sealing performance of the metal gasket.
FEM Stress Analysis and the Sealing Performance Evaluation in Bolted Flange Connections With Ring Joint Gasket Subjected to Internal Pressure: Effect of Scatter in Bolt Preloads
Authors: Kondo Koji , Tsubaki Shota , Sawa Toshiyuki , Kikuchi Tsutomu , Omiya Yuya 
Published: August 2013

Bolted flange connections with ring joint gaskets have been used to seal the inner fluid under higher internal pressure and higher temperature conditions where soft gaskets such as compressed sheet gaskets cannot be applied. Bolted flange connections are frequently tightened using torque wrench, and it is known that the values of bolt preloads are scattered. The effect of the scatter on the sealing performance for bolted flange connections with compressed sheet gasket or semi-metal gasket has been examined. However, no research on the characteristics for the bolted flange connections with ring joint gasket has been found. It is necessary to know the effect of the scattered bolt preloads on the sealing performance and mechanical behavior of the connection with ring joint gasket. In addition, it is important to know an optimum method for determining the bolt preloads taking account of the scatter in bolt preloads.
In this paper, leakage tests for bolted flange connections with octagonal ring joint gaskets were conducted for cases where the bolt preloads are uniform and scattered. The sealing performance of these connections with ring joint gaskets was measured and evaluated. In addition, the leak rate was estimated using the contact gasket stress distributions of the connections when the bolt preloads were uniform and scattered using 3-D FEM. Finally, the measured leak rate for the connection using helium gas was compared with the estimated results. The estimated results are in fairly good agreement with the measured values. It is found that the sealing performance of the connections tightened with the uniform bolt methods is better than that with scattered bolt preloads.