bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of Stresses in Cylindrical Shells Having Tapped Holes Parallel to the Axis of the Cylinder
Authors: Chandiramani Dipak K. , Gopalakrishnan Shyam , Mathkar Ameya 
Published: December 2016

Clause UG-27 of ASME Section VIII Division 1 [1] provides rules for calculating the thickness of shells under internal pressure. Mandatory Appendix-2 of Code [1] provides rules for design of bolted flanged connections.
In certain high pressure and high thickness pressure vessels having a cylindrical shell with bolted cover flange, Manufacturers avoid a separate end flange welded to the shell, as the construction becomes bulky. Instead of the same, Manufacturers provide tapped holes in shell wall parallel to axis of the cylindrical shell. The cover is directly bolted to these tapped holes provided in the shell.
This type of construction may be economical as compared to welding a conventional flange to the end of the shell. However this type of construction is not covered in the Code [1].
When such tapped holes are provided in the cylindrical shell, generally the total metal thickness provided at the tapped hole location meets UG-27 requirement of the Code [1]. However due to the tapped holes, the thickness from inside surface of vessel to inside surface of tapped hole is less than the required thickness of UG-27.
It is therefore required to analyze the stresses due to these tapped holes in the shell thickness to ensure that Code [1] allowable stresses are not exceeded.
The work reported in this paper was undertaken to determine the effect of internal pressure on the stresses in a cylindrical shell having tapped holes parallel to axis of the cylindrical shell.
Issue of Application for the Pre-Cracked Charpy Specimens to Estimate WWER-1000 RPV Metal Embrittlement
Authors: Revka Volodymyr M. , Chyrko Liudmyla I. 
Published: December 2016

In this study the analysis of fracture toughness test data has been performed in terms of estimation of the proper T0 value for several WWER-1000 RPV materials in unirradiated condition. The surveillance test data for the standard and reconstituted specimens were included in the analysis. It was found that a reference temperature T0 for reconstituted specimens is 31°C higher on average in comparison to the standard specimens. The possible reason is a high level of the stress intensity factor Kmax during the cycle at the stage of completion of crack tip sharpening for standard specimens.
Furthermore, the Charpy impact and fracture toughness test data for standard and reconstituted specimens have been compared considering the known relationship between the reference temperature T0 and the transition temperature T28J which corresponds to the Charpy energy level of 28 J.
Another objective of this study was to compare the RPV metal embrittlement rate for the two reactor pressure vessels using surveillance test data from standard and reconstituted fracture toughness specimens. The analysis has shown that test data for the reconstituted specimens is consistent with the test data for the standard specimens with regard to the embrittlement rate.
Comparison of Seismic Design Provisions Using ASCE 43 With Conventional Design Based on ASCE 7 Seismic Loads
Authors: Houston Thomas W. , Mertz Greg E. , Maham Andrew 
Published: December 2016

One graded approach for the design of nuclear facilities would design high hazard facilities to meet the provisions of ASCE 43 while low hazard facilities would be designed as conventional structures based on the seismic loading and design criteria in ASCE 7. In structures with an intermediate hazard it is not immediately obvious which standard provides a more conservative design. This paper presents a case study that compares the performance of an intermediate hazard structure with ASCE 7 seismic loading and criteria to the target performance goals described in ASCE 43 and DOE-STD-1020.
The purposes of seismic design associated with ASCE 7 are; 1) to provide minimum design criteria for structures appropriate to their primary function and use considering the need to protect the health, safety, and welfare of the general public by minimizing the earthquake-related risk to life, and 2) to improve the capability of essential facilities and structures containing substantial quantities of hazardous materials to function during and after design earthquakes.
Designs developed using the provisions of ASCE 7 are targeted to a collapse prevention limit state probability of 1% in 50 years. The goal of the earthquake provisions in ASCE 43 is to ensure that high hazard nuclear facilities can withstand the effects of earthquakes with desired performance, expressed as probabilistic Target Performance Goals and various limit, or damage, states. These Target Performance Goals range from 1×10−4 to 1×10−5 with limit states ranging from essentially linear response to short of collapse.
There are requirements invoked by ASCE 7 that are different than the requirements of ASCE 43 which prevents a direct computation of performance based on comparing the seismic demand levels required by each standard. These differences include the use of building R values in ASCE 7 compared to component specific Fu values in ASCE 43, the use of different analyses methods, ASCE 7 upper bound limits on seismic forces for some components, the limitations on framing system types, among others. The effect of these differences on the performance achieved between the two standards is evaluated for the design of a reinforced concrete shear wall structure that is representative of the types of structures used in nuclear facilities.
Evaluation of Ultrasonic Phased-Array for Detection of Planar Flaws in High-Density Polyethylene (HDPE) Butt-Fusion Joints
Authors: Prowant Matthew S. , Denslow Kayte M. , Moran Traci L. , Jacob Richard E. , Hartman Trenton S. , Crawford Susan L. , Mathews Royce , Neill Kevin J. , Cinson Anthony D. 
Published: December 2016

The desire to use high-density polyethylene (HDPE) piping in buried Class 3 service and cooling water systems in nuclear power plants is primarily motivated by the material’s high resistance to corrosion relative to that of steel alloys. The rules for construction of Class 3 HDPE pressure piping systems were originally published as an alternative to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME BPVC) in ASME Code Case N-755 and were recently incorporated into the ASME BPVC Section III as Mandatory Appendix XXVI (2015 Edition). The requirements for HDPE examination are guided by criteria developed for metal pipe and are based on industry-led HDPE research and conservative calculations.
Before HDPE piping will be generically approved for use in U.S. nuclear power plants, the U.S. Nuclear Regulatory Commission (NRC) must have independent verification of industry-led research used to develop ASME BPVC rules for HDPE piping. With regard to examination, the reliability of volumetric inspection techniques in detecting fusion joint fabrication flaws against Code requirements needs to be confirmed. As such, confirmatory research was performed at the Pacific Northwest National Laboratory (PNNL) from 2012 to 2015 to assess the ability of phased-array ultrasonic testing (PAUT) as a nondestructive evaluation (NDE) technique to detect planar flaws, represented by implanted stainless steel discs, within HDPE thermal butt-fusion joints. All HDPE material used in this study was commercially dedicated, 305 mm (12.0 in.) nominal diameter, dimension ratio (DR) 11, PE4710 pipe manufactured with Code-conforming resins, and fused by a qualified and experienced operator. Thermal butt-fusion joints were fabricated in accordance with or intentionally outside the standard fusing procedure specified in ASME BPVC. The implanted disc diameters ranged from 0.8–2.2 mm (0.03–0.09 in.) and the post-fabrication positions of the discs within the fusion joints were verified using normal- and angled-incidence X-ray radiography. Ultrasonic volumetric examinations were performed with the weld beads intact and the PA-UT probes operating in the standard transmit-receive longitudinal (TRL) configuration. The effects of probe aperture on the ability to detect the discs were evaluated using 128-, 64-, and 32-element PA-UT probe configurations. Results of the examinations for each of the three apertures used in this study will be discussed and compared based on disc detection using standard amplitude-based signal analysis that would typically be used with the ultrasonic volumetric examination methods found in ASME BPVC.
Fatigue Analysis of Cladded HPHT Pressure Containing Equipment
Authors: Karpanan Kumarswamy , Gatherar Nicholas 
Published: December 2016

Large, pressure-containing equipment used in subsea production, including Christmas trees (XTs), gate valves, flowloops, jumpers, and connectors, are constructed of low-carbon steel and cladded with corrosion resistant alloys such as Alloy 625. Cladding is a welding process that generates high tensile residual stresses on the cladded layer and on the heat affected zone (HAZ). High pressure high temperature (HPHT) equipment for subsea applications, designed to operate above 15 ksi internal pressure and 350°F, is also cladded. This equipment experiences severe working conditions in the field, plus cyclic loading during operations, such as riser loads, installation, intervention and, most importantly, startup and shutdown sequences. Per API 17TR8 guidelines, all HPHT equipment be hydrostatically tested to 1.5 times the equipment rated working pressure (RWP). For 20 ksi equipment, the hydrostatic test pressure is 30 ksi, which can significantly deform any highly localized stressed regions. These regions deform plastically when test pressure is applied. When the pressure is bled, these regions experience high compressive stresses due to surrounding materials that are still elastic.
This paper analyzes a simplified HPHT cladded gate valve (GV) body for fatigue loading (pressure cycles only) using the ASME Sec VIII, Div-3 method. The fatigue stress amplitude is calculated using an elastic-plastic material (E-P method) finite element analysis. In this method, first, the residual stress from the cladding process is simulated, and then the hydrotest is simulated on the component. During the hydrostatic test, fatigue sensitive regions (FSRs) or highly localized stressed regions such as the valve cavity and seat pockets, deform plastically, and the initial weld tensile residual stress turns to compressive (similar to autofrettage). Later, when these components are subjected to working pressure cycles (startup and shutdown), the shear stress range remains the same but the mean stress on the FSR reduces significantly. By considering all types of residual stresses, the high cycle fatigue life can be predicted with a high degree of accuracy.
Measurement of Hydride Precipitation and Dissolution Kinetics Using Synchrotron X-Rays
Authors: Shiman Oksana , Tulk Eric , Daymond Mark R. 
Published: December 2016

Structural components of nuclear reactors made from zirconium alloys are subject to degradation mechanisms associated with hydrogen pickup during their operating life. Even small amounts of hydrogen isotopes (∼tens of wt. ppm) can significantly reduce the material’s fracture toughness and make it susceptible to a sub-critical crack growth mechanism known as Delayed Hydride Cracking (DHC). The mitigation of potentially costly failures of these components requires assessments based upon not only the bulk concentration of hydrogen, but the concentration of hydrogen precipitated as hydrides, and in solution. The behaviour of the zirconium-hydrogen system near ∼100 ppm hydrogen concentration continues to be the subject of research, primarily due to its otherwise complex behaviour and critical role in nuclear plant operations. There is an anisotropic volumetric expansion associated with the precipitation of zirconium hydride, and this precipitation event results in plasticity in the surrounding matrix and compressive strain in the hydride phase. This leads to both a pronounced solubility hysteresis upon dissolution and precipitation, as well as variances in solubility behaviour depending on the prior thermal and mechanical history.
In the present study, high-energy synchrotron x-ray diffraction is used to study the evolution of hydrogen solubility in Zr-2.5 wt% Nb pressure tube material with different hydrogen concentrations in situ during thermal cycling between 100 and 400°C. This technique provides the ability to directly measure the amount of hydride in a given sample at different temperatures, and to evaluate zirconium-hydrogen precipitation and dissolution kinetics.
Structural Integrity Assessment of Doel 3 and Tihange 2 RPVs Affected by Hydrogen Flakes: Refined X-FEM Analyses
Authors: Dulieu Pierre , Lacroix Valéry 
Published: December 2016

During the 2012 outage at Doel 3 and Tihange 2 Nuclear Power Plants, specific ultrasonic in-service inspections revealed a large number of quasi-laminar indications in the base metal of the reactor pressure vessels, mainly in the lower and upper core shells. The observed indications could subsequently be attributed to hydrogen flaking induced during the component manufacturing process.
As a consequence, a Flaw Acceptability Assessment had to be performed as a part of the Safety Case demonstrating the fitness-for-service of these units.
In that framework, detailed analyses using eXtended Finite Element Method were conducted to model the specific character of hydrogen flakes. Their quasi-laminar orientation as well as their high density required setting up 3D multi-flaws model accounting for flaw interaction.
These calculations highlighted that even the most penalizing flaw configurations are harmless in terms of structural integrity despite the consideration of higher degradation of irradiated material toughness.
Structural Integrity Assessment of Doel 3 and Tihange 2 RPVs Linear Elastic and Elastic-Plastic X-FEM Calculations Performed for Large Scale Tests
Authors: Lacroix Valéry , Dulieu Pierre 
Published: December 2016

In the framework of the hydrogen flakes issue concerning the reactor pressure vessels of the two Belgian NPP’s Doel 3 and Tihange 2, the Federal Agency of Nuclear Control required to perform tests on large scale specimens taken from a block representative of the pressure vessels with the double objective of validating the structural integrity approach and of verifying the load capacity of the specimens affected by flakes.
The large scale tests were led on many kinds of specimens: 4 points bending specimens, CT specimens and tensile specimens containing hydrogen flakes or flawed with EDM notches. All of these tests have been simulated using extend finite element method (XFEM).
The paper describes the linear elastic and elastic-plastic fracture mechanics calculations performed in the frame of these large scale tests using XFEM and presents the comparison between simulations and experiments.
A focus is done on the XFEM capabilities to model 3D complex shaped flaws like hydrogen flakes.
Effect of the Thickness on Re-Characterisation of Subsurface to Surface Flaw: Application on Piping and Vessels
Authors: Lacroix Valéry , Katsumata Genshichiro , Li Yinsheng , Hasegawa Kunio 
Published: December 2016

If a subsurface flaw is located near a component surface, the subsurface flaw is transformed to a surface flaw in accordance with a subsurface-to-surface flaw proximity rule.
The re-characterization process from subsurface to surface flaw is adopted in all fitness-for-service (FFS) codes in different countries. However, the specific criteria of the recharacterizations are different among the FFS codes.
The authors have proposed a new subsurface-to-surface flaw proximity rule based on experimental data and equivalent fatigue crack growth rates.
Recently, the authors have highlighted through numerous fatigue crack growth calculations that, on one hand, the proximity rule provided in the current ASME Boiler and Pressure Vessel Code Section XI (ASME Code Section XI) can provide non conservative fatigue lives for thin wall components like pipes and, on the other hand, for thick wall components like vessels, the current proximity rule and the proposed one provide relatively similar fatigue lives.
It appears therefore that the flaw-to-surface factor should be updated according to the thickness of the component or according to the type of component i.e. pipe or vessel.
In this study, fatigue crack growth calculations were carried out on additional flaw configurations in thick wall pipes and thin wall vessels in order define the best limit for the thickness-dependence of the fatigue lives.
Finally, a new subsurface to surface proximity rule depending on the thickness of the component is proposed.
Assessing the Behaviour of Subsea Pipes Under Impact
Authors: Fareed Shamsoon , Cotsovos Demitrios M. , Laghrouche Omar 
Published: December 2016

Subsea steel pipes are often used to form extensive networks for transporting oil and gas over large distances. Such pipes can potentially be subjected to actions characterized by high loading rates and intensities stemming from accidental loads, due to high-mass low-velocity impacts. In order to ensure that such networks can continue to operate even after being subjected to such extreme loading conditions, it is essential that the behavior of the pipes is characterized by a certain level of resilience. The present study aims to investigate numerically, via dynamic nonlinear finite element analysis, the effect of various parameters on the dynamic response exhibited by pipes under impact loading. The considered parameters are associated with the impacting object, the geometry and the support conditions of the pipes, the level of axial loading as well as the internal and the external pressures imposed onto the walls of the pipes.
The numerical predictions, which are validated against relevant published test data, reveal that the above parameters, which are associated with the in-situ conditions imposed onto subsea pipes throughout their operational life, can significantly affect, often detrimentally, the behavior exhibited under impact loading. Existing assessment methods employed in practice for predicting the level of damage sustained by pipes during impact do not accurately consider the effect of the above parameters. As a result, questions are raised concerning the ability of such guidelines to realistically predict the level of damage sustained by subsea pipes under impact.
Technical Basis for Proposed ASME Section XI Code Case on Beyond Design Bases Earthquake
Authors: Donavin Paul R. , Gilada Ramiz , Gustin Harry , Vo Truong , Pace Raymond 
Published: December 2016

This paper will provide the bases for the requirements in the Beyond Design Basis Events (BDBE) evaluation performed in accordance with the American Society of Mechanical Engineers (ASME), Boiler and Pressure Vessel Code (BPVC), Section XI, Code Case (CC). The CC provides rules to facilitate the affected components Return to Service (RTS) after a BDBE magnitude Earthquake. The paper describes the bases for the examination of Reactor Coolant Pressure Boundary (RCPB) Structures, Systems and Components (SSCs) for determining the actual seismic loading and magnitude. The implications of the examination data based on design allowable stress values. The pipe loads determined shall be used to calculate stresses on the pumps and valves.
The paper also describes the methodology for seismic events lasting longer than 100 cycles.
The Cumulative Usage Factor (U) due to the event is calculated from individual cycles as; U = U1 + U2 + U3 + ... + Un. Aftershocks are accounted for in the methodology. Fatigue usage from the event that increases the total U to a value greater than 0.8 shall be included as high risk location(s) in the ASME BPVC, Section XI, Inservice Inspection (ISI) Program.
Validation of Axial Crack Stability Assessment Methods in xLPR Version 2.0 Code
Authors: Kalyanam S. , Brust F. W. , Wilkowski G. , Shim D. J. , Rudland D. 
Published: December 2016

As part of the xLPR (Extremely Low Probability of Rupture) project, validation efforts were conducted to assess the predictive capability of axial surface crack (Ax-SC) and axial through-wall crack (Ax-TWC) stability modules employed for making the crack stability assessment. For the Ax-SC, the plastic collapse solution/criteria from the Ductile Fracture Handbook (DFH) was selected and employed after making detailed comparisons between the solutions obtained from the DFH and API-579/ASME FFS-1 solution methods. Experiments from past tests conducted for the Atomic Energy Commission (AEC) and by MPA-Stuttgart were used to validate the performance of the implemented axial SC stability module.
Similarly, for the axial TWC stability assessment, a Limit Load solution, and a numerical analysis procedure for an elastic-plastic fracture mechanics (EPFM) based method employing a J-integral fracture mechanics parameter approach using a GE/EPRI type J-estimation equation, and tabulated plastic influence functions based on pipe dimension and Ramberg-Osgood material parameters, were used. Experimental results from past pipe tests conducted for the AEC, others conducted for the PRCI, and by Tokyo Gas involving larger diameter pipes were used to validate the performance of the implemented axial TWC stability module.
In this paper, the selection of stability criteria/solutions, their performance and implications for the xLPR 2.0 code are discussed. The impact of using different flow stresses (function of yield and ultimate stresses), and stress magnification factor (Folias bulging factor) expressions, on the predictions is highlighted. Further, a conservative basis for the assessment of axial crack stability in welds is proposed. In closing, additional empirical corrections that can be incorporated without overly biasing the deterministic solutions/criteria that feed into a probabilistic analysis are highlighted.
Manufacturing Conditions of French Reactor Pressure Vessels to Avoid the Occurrence of Hydrogen Flakes
Authors: Miller C. , Champigny F. , Frund J. M. 
Published: December 2016

The formation of hydrogen flakes in Reactor Pressure Vessels (RPV’s) forgings is a well known phenomenon that can affect forging components during manufacturing. Following recent data from Belgium, it has been the object of important assessments during the last 3 years. We will present in this paper elements pertaining to the RPV’s of the French nuclear fleet.
A thorough review of fabrication processes and specifically of ultrasonic examination of forgings, including the oldest ones has demonstrated that the risk of leaving undetected hydrogen flakes in RPV’s forgings is not a problem in French RPVs. The French Regulator also clearly shared this position point in 1985. Parts with defects were once again observed at the beginning of 2012 but the defects were attributed to errors in hydrogen measurement at the steel maker shop. Those hydrogen induced defects were detected at an early manufacturing stage (before quality heat treatment) by ultrasonic examination, and the concerned parts were consequently rejected through the normal quality control process.