bluuebunny/crossref_metadata_2025_split huggingface dataset:
How an Experienced Fabricator Can Provide Support to Site Activities to Upgrade Existing Units to New Operational Requirements
Authors: Sabattoli Luca , Poddighe Salvatore 
Published: October 2017

Some examples how an experienced fabricator can manage in-field alteration of critical equipment in order to satisfy new customer needs are presented and relevant implications evidenced.
1) Site modification of a Cr-Mo-V Reactor
A high thickness, large diameter 2.25Cr-1Mo-0.25V Hydrocracker Reactor was completed in field by performing three circumferential seams and related LPWHT. Since the Customer decided to modify the process and to add a new catalyst bed, design changes were implemented to add a new catalyst bed and a new 8” quench nozzle.
2) Rehabilitation of existing Reactor
An existing reactor no more in operation for several years was rehabilitated in field to comply with a new process unit layout (debottlenecking) to comply with current law requirements.
3) Site Assistance during schedule Turnaround activities
Reactors are designed for extended life cycle up 25 to 30 years, but severe operating conditions may require reconditioning after onsite inspection during scheduled turnaround.
Fabricator has been involved jointly with End User and Process Licensor for design changes and has responsible for the onsite execution activities.
Tribological Analysis of Thermal Spray Coatings of Ni and Al2O3 With Dispersion of Solid Lubricants in Wear Modes
Authors: Christy John V. , Mourad Abdel-Hamid I. , Tiwari Sudhir 
Published: October 2017

In the present work, Ni and 60 wt. % of Al2O3, as thermal spray was mixed in 2:1 proportion with entrapped solid lubricant such as PTFE and Graphite through a D-Gun on the Bakelite used as substrate. For that, the specimen was taken and cleaned properly and coated with thermal spray and solid lubricating coatings of 0.5 micrometre thickness. At elevated temperatures, NiAl2O3 a common thermal spray coating protects the solid lubricants entrapped in it and thus causes the layer to be stable and dynamic. The solid lubricants mixed in thermal spray were graphite and PTFE. These were then ultrasonically cleaned in the acetone bath. The coating is done by a duo spray pump that spurts the coating on the work piece. This pump spurting is controlled by a semi permeable membrane coated on the work piece. Coatings were tested at different air pressure, temperature and impingement angle. It was found that the degradation of coating was observed on low impingment angles and also with the reciprocating stress inputs. The Graphite and NiAl2O3 coating is found to be more stable tribologically as compared to PTFE and NiAl2O3 coating at high temperatures and pressures. Morphological analysis of coatings was also done. The coating was tested on cutting tool ends like drill bits, planar cutting tool and turning tools. Separate analysis was carried out on erosive wear, abrasive wear, temperature and pressure with varied load conditions on the coatings done on Bakelite. On all the individual tests done Graphite and NiAl2O3 mix coating was found stable.
This coating finds much more application in pipes and pressure vessels systems. The inside bore of a pipe can be coated similarly which will smoothly transfer the abrasive sludge or fluids with much reduction on its friction coefficient.
Difference of Strength Evaluation Approach Between for DBE and for BDBE
Authors: Kasahara Naoto , Sato Takuya 
Published: October 2017

Preparation for beyond design basis events (BDBE) becomes important as the lessons learned from the Fukushima Daiichi nuclear accident.
The objective of strength evaluation for design basis events (DBE) is a confirmation to prevent structural failure for assumed events.
For BDBE, main objectives are weak point survey, deterministic and probabilistic risk assessment, and planning of countermeasures including potable equipment and accident management.
According to the above objectives, strength evaluation approach have to be different between for DBE and for BDBE.
(1) DBE
Conservative approach to prevent of failure.
Design by analysis concept is basically adopted
Assumption of hypothetical failure modes to prevent actual failure modes
Stress criteria to bond actual strength
Elastic analyses for conservative loading assumption
Design factor to bound uncertainties
(2) BDBE
Best estimation of failure behavior with uncertainties to plan mitigations
Identification of realistic failure modes to identify failure consequences
Criteria by dominant parameters of failure phenomena
Inelastic analyses for realistic loading prediction
Probabilistic evaluation to quantify uncertainties.
Strength evaluation concept has not yet been established for BDBE. It is necessary to discuss from basic philosophy to make sharable concepts.
Adequate criteria is required to meet above concepts. Instead of stress, strain is one of candidate.
New evaluation technics are desired to satisfy above criteria.
This paper indicates the direction of strength evaluation for BDBE with same examples proposals. Its aims is to promote international discussions and to implement new technologies to actual countermeasures against BDBE.
Development of a Novel Test Procedure to Investigate the Impact of Strain Gradients on the Fatigue Endurance of Stainless Steel
Authors: Riley Mohammed-Rafi , Davies Catrin M. , Garwood Stephen 
Published: October 2017

In recent years, there has been an increasing need for component specific testing in nuclear power plant (NPP) materials. This has arisen from changes in fatigue design criteria outlined within the ASME Boiler Pressure and Vessel and Pipe Code (BPVC). These are primarily derived from low-cycle fatigue (LCF) testing on idealized small-scale specimens. For the case of stainless steel (SS), testing is performed under membrane loading on traditional uniaxial round-bar specimens according to standards such as ASTM E606. Here, failure is defined as a 25% drop in load, that typically corresponds to a 3 mm deep crack. Real NPP components however, rarely experience such membrane loading due to their complex geometry and in-service loading (combined primary and secondary stresses). For the case of an internally-pressurized pipe subjected to thermal transients, due to temperature fluctuations in the coolant, an additional through-wall stress field gradient is present. This results in fatigue crack initiation and propagation occurring into a decreasing stress field, which may be expected to result in longer fatigue lives than within small specimen testing and, hence, a large degree of inherent over-conservatism may exist in the ASME design data.
This paper describes the development of a novel test procedure able to incorporate the effect of a stress gradient within fatigue endurance testing. A bespoke eight-point bend (8PB) setup has been developed that is capable of performing load-, displacement- and strain-controlled LCF tests. A series of trials have been conducted in all three control modes with the material response validated against finite element analysis (FEA). It is anticipated that this testing procedure can provide a better representation of NPP components under fatigue loading conditions, providing results that would be used to remove over-conservatism within the current design criteria.
Application of Master Curve Approach to Surveillance Test Data for WWER-1000 Reactor Pressure Vessels
Authors: Revka Volodymyr M. , Chyrko Liudmyla I. 
Published: October 2017

An important issue in the safety operation of WWER-1000 type reactor is a decrease in fracture toughness for reactor pressure vessel steels due to neutron irradiation. This effect for RPV metal is known as radiation embrittlement. The radiation induced temperature shift of the fracture toughness transition curve is considered as a measure of the embrittlement rate. The Charpy impact and fracture toughness specimens are included in the surveillance program for an assessment of changes in fracture toughness of RPV materials.
The present analysis is based on a large data set which includes mostly experimental results for pre-cracked Charpy specimens from a WWER-1000 RPV surveillance program. A Master curve approach is applied to analyze the surveillance test data with respect to a shape of the fracture toughness transition curve and a scatter of KJC values.
The RPV base and weld metal in unirradiated, thermally aged and irradiated conditions are considered in this study. The maximum shift in a reference temperature T0 due to irradiation is 107 degree Celsius. It is shown that the Master curve, 5 % and 95 % tolerance bounds describe adequately the temperature dependence and the statistical scatter of KJC values for WWER-1000 RPV steels both in unirradiated condition and after irradiation up to design as well as long term operation neutron fluence. Furthermore, a development of the Weibull plots for considered data sets is shown that the Weibull slope is close to the expected one of 4 on average. Finally, a comparison of the reference temperature T0 and a scatter of KJC values derived from the pre-cracked Charpy and 0,5T C(T) specimens of base and weld metal in unirradiated condition is done. The analysis has shown a significant discrepancy between the T0 values derived from the two different types of specimens for both RPV metals.
Seismic Response Analysis of Flexible Drain System Into External Floating Roof Storage Tanks
Authors: Bernard Gary , Vera Damien , Lim Weng Kheong 
Published: October 2017

Floating roofs are commonly used worldwide on top of cylindrical oil storage tanks as a primary means to prevent formation of vapor above stored products into the storage tanks and should provide a safe and efficient storage of products with minimal risk for the environment.
However, aboveground storage reservoirs built in seismic zones are prone to earthquake damage. Extensive research has been done to enhance performance of the floating roof tanks against damage to ground foundations, fixed and floating roof, tank shells as well as adjacent piping. Indeed, the stored oil sloshing in a cylindrical storage tank is known to have caused damage to the tank shell, tank roof and as well to anti-rotation columns.
One of the possible dangers of liquid sloshing is the resultant damage to in-situ roof drain systems within external floating roof tanks. Indeed, roof drain systems are designed for continuous withdrawal of rainwater from external floating roofs, and if damaged, would result in dysfunction of the systems and irreversible discharge of oil products into the containment dyke. In this regard, a reliable roof drain system should have the capability to withstand liquid sloshing effects, and to a certain degree, ensure resistance in events of displacement of the floating roof.
The aim of this document is to use knowledge of flexible pipe technology and industry recognized dynamic analysis software to analyze the effects of earthquakes on the integrity of a flexible drain pipe system. Analysis of liquid sloshing effects on flexible drain pipe systems using dynamic analysis software will be presented and the effects of structural damages such as loss of anti-rotation columns on the integrity of flexible drain pipe systems will be assessed.
In the end, the document will propose recommendations on how industry can further enhance roof drain systems within external floating roof tanks to ensure performance and functionality after occurrence of earthquakes.
Excellent Resistance to Hydrogen Embrittlement of High-Strength Copper-Based Alloy
Authors: Ogawa Yuhei , Yamabe Junichiro , Matsunaga Hisao , Matsuoka Saburo 
Published: October 2017

In order to develop more energy-efficient and safer, hydrogen pre-cooling systems destined for use in hydrogen refueling stations, a metallic material must first be researched and found to possess three excellent material properties: high strength, high thermal conductivity and low susceptibility to hydrogen embrittlement (HE).
This study investigated the hydrogen compatibility of a beryllium-copper alloy 25 (UNS-C17200), fabricated by a solution annealing at 1053 K and via subsequent aging treatment at 588 K. After these thermal processes, the tensile strength exceeded 1200 MPa, due to the precipitation of nano-sized CuBe compounds (γ’ phase). Slow strain rate tensile (SSRT) and tension-compression fatigue tests were performed using this material, in addition to fatigue crack growth and fracture toughness tests, in laboratory air and in gaseous hydrogen with a pressure of 115 MPa at room temperature.
After the SSRT test, the material showed no hydrogen-induced degradation of strength or ductility and, surprisingly, there was also no degradation of fatigue resistance or fracture toughness values in high-pressure gaseous hydrogen. Specifically, it was revealed that the material demonstrated an excellent HE resistance, despite having such a high tensile strength.
Research and Development of Three Dimensional Seismic Isolation System Utilized Coned-Disc-Springs With Rubber Bearings
Authors: Miyagawa Takayuki , Watakabe Tomoyoshi , Yamamoto Tomohiko , Fukasawa Tsuyoshi , Okamura Shigeki 
Published: October 2017

The seismic isolation system consisting of laminated rubber bearings is applied to development of the Sodium-cooled Fast Reactor (SFR) in Japan. While rubber bearings as horizontal isolation system have been expected to be ensured seismic safety margin of components installed in reactor building against horizontal seismic load, vertical isolation systems have been also studied in order to tolerate to the seismic load which has been increased steadily.
In this paper, the three dimensional seismic isolation system by combining coned disc springs with rubber bearings is proposed as a concept which consists of isolation devices with abundant track record. Analytical study for this system results that the rocking motion can be suppressed by itself without any suppression system and that the mitigation of vertical response can be enough for buckling design of the reactor vessel simultaneously. In particular, it is important that the vertical natural frequency of system is within the range of 3Hz to 5Hz. Besides, layout, size and stacks of coned discs in the unit of system are studied in order to obtain suitable for specification to SFR buildings.
Methods for Uncertainty Quantification and Comparison of Weld Residual Stress Measurements and Predictions
Authors: Lewis John R. , Brooks Dusty , Benson Michael L. 
Published: October 2017

Weld residual stress (WRS) is a major driver of primary water stress corrosion cracking (PWSCC) in safety critical components of nuclear power plants. Accurate understanding of WRS is thus crucial for reliable prediction of safety performance of component design throughout the life of the plant. However, measurement uncertainty in WRS is significant, driven by the method and the indirect nature in which WRS must be measured. Likewise, model predictions of WRS vary due to uncertainty induced by individual modeling choices. The uncertainty in WRS measurements and modeling predictions is difficult to quantify and complicates the use of WRS measurements in validating WRS predictions for future use in safety evaluations. This paper describes a methodology for quantifying WRS uncertainty that facilitates the comparison of predictions and measurements and informs design safety evaluations.
WRS is considered as a function through the depth of the weld. To quantify its uncertainty, functional data analysis techniques are utilized to account for the two types of variation observed in functional data: phase and amplitude. Phase variability, also known as horizontal variability, describes the variability in the horizontal direction (i.e., through the depth of the weld). Amplitude variability, also known as vertical variability, describes the variation in the vertical direction (i.e., magnitude of stresses). The uncertainty in both components of variability is quantified using statistical models in principal component space. Statistical confidence/tolerance bounds are constructed using statistical bootstrap (i.e., resampling) techniques applied to these models. These bounds offer a succinct quantification of the uncertainty in both the predictions and measurements as well as a method to quantitatively compare the two. Major findings show that the level of uncertainty among measurements is comparable to that among predictions and further experimental work is recommended to inform a validation effort for prediction models.
Seismic Test Results of the Main Steam Safety Relief Valve for Japanese Boiling Water Reactor Nuclear Power Plants
Authors: Nishino Koji , Tsutsumi Yoshitaka , Yonekura Kazuyoshi , Kojima Nobuo , Watanabe Yukio , Kumagai Shin 
Published: October 2017

The functional requirements of Main Steam Safety Relief Valves (SRVs) provided in Boiling Water Reactor (BWR) nuclear power plants in Japan have been previously evaluated via seismic tests and so forth; however, since the response acceleration has increased in line with a recent reassessment of standard earthquake ground motions, it is necessary to evaluate seismic operability with respect to high acceleration. In addition, from the viewpoint of equipment fragility in seismic PRA also, it is necessary to determine the practical seismic operability limits.
We used a resonant shaking table in the Central Research Institute of the Electric Power Industry (CRIEPI) [1], which is capable of seismic tests at acceleration levels that have been unachievable until now, and in seismic tests carried out on an SRV, we obtained results confirming that validated seismic operability was possible even at response accelerations as high as 20×9.8 m/s2.
The seismic operability results obtained for this SRV will be applied to a fragility analysis of seismic PRA.
Comparison of Prediction Models for Mechanical Properties of Thermally Aged Cast Austenitic Stainless Steels
Authors: Hirota Takatoshi , Ochi Mayumi , Hojo Kiminobu , Nishi Wataru , Hayashi Shotaro 
Published: October 2017

The cast austenitic stainless steel (CASS) is used for the primary loop pipes of some PWR plants. It is known that these stainless steels are susceptible to thermal aging during plant operation. This material degradation decreases the fracture toughness (J-R curve) and increases the tensile strength, which affects the possibility of the fracture of the pipes.
The JPOG prediction models for aged CASS materials were developed based on the CASS material test data for PWR plants in Japan, which was presented in ASME PVP2005-71528. The JPOG prediction models consist of the model to predict the true stress-true strain curve and the model to predict the J-resistance parameters, such as the Js at ductile crack initiation (JIc) and at Δa = 6 mm (J6) in terms of the ferrite contents and aging time. In the US and France, similar degradation models were developed using their own databases or internationally combined one. In this work, three prediction models for thermal aging of CASS were compared and benchmark analyses were performed under Japanese PWR plants operating condition.
Study on Dynamic Response of Piping System Induced by Waterhammer Considering Support Characteristics
Authors: Okami Atsushi , Kataoka Shunji , Honda Takuro 
Published: October 2017

Waterhammer is the phenomenon which occurs due to rapid valve operation or sudden stop of pumps. When the waterhammer occurs, unbalanced pressure between elbows causes transient load on piping system. In the piping design against the waterhammer, it is necessary to evaluate the strength and the displacement of piping system against the transient load, and required to provide adequate piping supports. In the piping design, dynamic analysis and static analysis with DLF (Dynamic Load Factor) are often conducted to consider dynamic effect of the water hammer load. The piping support often regarded as rigid in the piping system analysis, however, because of support characteristic (flexibility, plastic behavior, sliding friction), the dynamic response of piping system changes from analysis result with rigid support. For this reason, support characteristics shall be considered adequately. Nevertheless, effect of the support characteristics on the piping design has not been discussed sufficiently.
In this paper, to clarify the effect of the support characteristics against the waterhammer load, a series of the nonlinear dynamic analyses were conducted. Based on the analysis results, the response spectra and the ductility charts considering the nonlinearities of the piping system were created. the design approach to properly control the displacement of piping system based on the nonlinear response spectra and ductility charts, is proposed, and the dynamic response against waterhammer load in the piping system of LNG loading line is discussed.
On a Plastic Limit Loads of Complex-Cracked Pipes With Weld Overlay Using Finite Element Limit Analyses
Authors: Jeon Da-Som , Huh Nam-Su 
Published: October 2017

In the present study, the plastic limit loads of the complex-cracked pipes, which have 360° internal surface crack along the circumference of pipe together with partial through-wall crack, are investigated via detailed 3-dimensional (3-D) finite element (FE) limit analyses. In terms of geometry of the complex-cracked pipe, the Alloys 82/182 butt weld that has welds overlay using the Alloys 52/152 for mitigating primary water stress corrosion cracking (PWSCC) in the nuclear pipe is considered.
In the present FE limit analyses on complex-cracked pipes with welds overlay, the effect of strength mismatch between Alloys 82/182 and Alloys 52/152, depth of 360° internal surface crack and length of partial through-wall crack on plastic limit loads of complex-cracked pipes is systematically evaluated. As for loading conditions, axial tension, global bending and internal pressure are employed.
The resulting FE plastic limit loads of complex-cracked pipes with welds overlay are also compared with the existing solutions, and finally the applicability of simple engineering estimate using the single material property based on the weighted average concept instead of using the properties of Alloys 52/152 and Alloys 82/182 to the prediction of the plastic limit loads of complex-cracked pipes with welds overlay is pursued.
Introduction of Subsurface Proximity Criteria in the World and Stress Intensity Factors for Transformed Surface Flaws
Authors: Hasegawa Kunio , Li Yinsheng , Katsumata Genshichiro , Dulieu Pierre , Lacroix Valéry 
Published: October 2017

Net-section stress at the ligament between component free surface and subsurface flaw increases when the ligament distance is short. It can be easily expected that stress intensity factors increase when the subsurface flaw locates near the free surface. To avoid catastrophic failures caused by ligament failure, fitness-for-service (FFS) codes provide flaw-to-surface proximity rules. The proximity rules are used to determine whether the flaws should be treated as subsurface flaws as-is, or transformed to surface flaws. The stress intensity factor for the transformed surface flaw increases furthermore. The increment of the stress intensity factor before and after transformation depends on the location of the subsurface flaw.
Although the concept of the proximity rules are the same, the specific criteria for the rules on transforming subsurface flaws to surface flaws differ amongst FFS codes. Particularly, the criteria are different amongst the same organizations of ASME (American Society of Mechanical Engineers).
The proximity criteria of the FFS codes in the world were introduced in this paper. In addition, the stress intensity factors based on the different criteria used in the ASME Codes are compared.