bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Measurement of an Array of Heated Rods Subjected to Vacuum Drying Conditions
Authors: Maharjan Dilesh , Hadj-Nacer Mustafa , Greiner Miles 
Published: October 2017

During vacuum drying of used nuclear fuel canister, helium pressure is decreased to as low as 67 Pa to promote evaporation and removal of water remaining in the canister following draining operation. At low pressures associated with vacuum drying, there is a temperature jump (thermal resistance) between the solid surfaces and helium in contact with them. This temperature jump increases as the pressure decreases (rarefied condition), which contributes to the fuel assembly’s temperature increase. It is important to keep the temperature of the fuel assemblies below 400°C during vacuum drying to ensure their safety for transport and storage.
In this work, an experimental apparatus consisting of a 7×7 array of electrically heated rods maintained between two spacer plates and enclosed inside a square cross-section stainless steel pressure vessel is constructed to evaluate the temperature of the heater rods at different pressures. This geometry is relevant to a BWR fuel assembly between two consecutive spacer plates. Thermocouples are installed in each of the 49 heater rods, spacer plates and enclosure walls. They provide a complete temperature profile of the experiment. Different pressures and heat generation relevant to vacuum drying conditions are tested. The results showed that the maximum temperature of the heater rods increases as the pressure decreases. The results from these experiments will be compared to computational fluid dynamics simulations in a separate work.
Numerical Analysis of Mechanical Interaction of Pipe-in-Pipe Flowline
Authors: Akolawole M. T. , Pu Yongchang 
Published: October 2017

Pipe-in-pipe (PIP) flowline is a unique solution for long subsea tie-backs in deepwater and ultra-deepwater fields. This is because of its optimum thermal performance over wet insulation. However, pipelines are subjected to the highest loading condition during installation. Significant limitation imposed on existing installation vessel in deepwater, is peculiar to S-lay installation method. Contrary to the level of stress experienced with the S-lay installation method at specific locations such as overbend and sagbend region, this method is still widely utilized because of its high production rate. These regions are dominated by bending curvatures which are defined by different load conditions. Due to the composition of PIP system, it is important to understand the structural response of the flowline, the mechanical interaction occurring between various components and the amount of load transfer at this location.
Although, the mechanical interaction within the PIP system are case specific. However, it has been observed that prior to case study analysis; simple pipe models are being developed to assess the mechanical interaction of this system. This paper addresses the impact of the centralizer material on the structural response and load transfer between the outer pipe and inner pipe. The numerical analysis was carried out using Ansys software and was based on Euler Bernoulli bending theory. The centralizer was clamped on to the inner pipe with the clearance between the centralizer and the outer pipe included in the model. The core of the analysis, was modeling the visco-elastic response of nylon rings (Polyamide 6), from which centralizers are made. The centralizer was spaced based on S-lay or J-lay installation criteria against heat sink.
The results demonstrated the relationship between spacing of the centralizer and areas of first contact, amount of force transferred through the centralizer material, non-linearity introduced by contact formulation, alongside the time and temperature dependent behavior of visco-elastic material. The result correlated accurately with the bending principle. Different material model was assessed to determine accuracy of results obtained, in the absence of experimental test data to model visco-elastic response. In addition, the bending curvature was used to predict the mechanical interaction in installation and operation analysis, where limitations of explicitly modeling centralizers exist.
Models for Calculating the Effect of Environment on Fatigue Life (Fen) for Complex Waveforms and/or Non-Isothermal Conditions
Authors: Currie Chris , Morley Andrew , Platts Norman , Twite Marius , Wright Keith 
Published: October 2017

Environmentally assisted fatigue of nuclear plant materials in the Pressurised Water Reactor (PWR) coolant environment is a phenomenon that has been extensively studied over the past 30 years. Methods for accounting for the PWR environment in an ASME III fatigue assessment are presented in NUREG/CR-6909. The deleterious effect of environment is described through a Fen factor dependent upon strain rate, temperature and the dissolved oxygen content of the water. The formulae which describe the Fen are based upon correlations observed in test data predominantly from tests conducted with constant temperature and strain rate (triangular or sawtooth loading). Actual loading histories encountered during service are far more complex, with both strain rate and temperature, and therefore Fen, varying through the cycle. NUREG/CR-6909 recommends a modified rate approach method for accounting for this, whereby the load cycle is broken up into a number of strain increments and then integrated to give the Fen for the cycle.
There is a substantial and growing body of data for conditions in which the strain rate or temperature or both changes. The NUREG/CR-6909 modified rate approach does not generally perform well in describing the deleterious effect of environment in these complex conditions. In particular, the modified rate approach does not predict a difference in life when the temperature is varied in-phase or out-of-phase with the strain waveform, or when the slow portion of the strain rate is moved from the top to the bottom of the waveform.
This paper presents new data from strain-controlled fatigue endurance testing of two casts of 304L with complex waveforms and temperature cycling. The paper then presents and compares a number of models for integrating the Fen through the cycle, including methods which weight Fen increments depending on position in the strain cycle.
It is concluded that greater weighting on the environmental effect in the top of the cycle is necessary to describe the differences in life observed. This is further validated by a review of test data in the wider literature. An improved method is presented to account for the effects of the PWR environment on fatigue lives of austenitic stainless steel materials, which has similarities to the “Weighted K Rate” method previously presented by Rolls-Royce, PVP2016-63497, for environmentally assisted fatigue crack growth.
Development of Secondary Stress Weighting Factor and Plastic Reduction Factor From Moment-Rotation Curves of Surface Cracked Pipe Tests
Authors: Pothana S. , Wilkowski G. , Kalyanam S. , Hioe Y. , Hattery G. , Martin J. 
Published: October 2017

In flaw evaluation criteria, the secondary stresses (displacement controlled) may have different design limits than primary stresses (load-controlled stress components). The design limits are based on elastic stress analysis. Traditionally the elastic design stresses are used in the flaw evaluation procedures. But realistically a flaw in the piping system can cause non-linear behavior due to the plasticity at the crack plane as well as in the adjacent uncracked-piping material. A Secondary Stress Weighting Factor (SSWF) was established which is the ratio of elastic-plastic moment to the elastic moment calculated through an elastic stress analysis. As long as the remote uncracked pipe stresses are below yield, the SSWF is 1.0, and if the uncracked pipe plastic stresses are above the yield stress, the SSWF reaches a limit which is called the Plastic Reduction Factor (PRF).
Four-point-bend tests were conducted on pipes with varying circumferential surface-crack lengths and depths. The moment-rotation plots obtained from various pipe tests were used in the determination of PRF. A lower-bound limiting PRF can be calculated from a tensile test, but pipe systems are not uniformly loaded like a tensile specimen. The actual PRF value for a cracked pipe was shown to have a lower bound, which occurs when the test section of interest is at a uniform stress (such as the center region in a four-point pipe bend tests). When multiple plastic hinges develop in a pipe system (a “balanced system” by ASME Section III NB-3650 design rules), this gives a greater reduction to the elastically calculated stresses since there is more plasticity. It was found that the plastic reduction is less when most parts of the pipe system remains elastic, or if the crack is located in the high strength/ lower toughness pipe or welds, or if the pipe size is large enough that elastic-plastic conditions occur even for a higher toughness material. Interestingly, it was shown that the same system with different loading directions could exhibit different actual PRF values if the change in the loading direction changes how much of the pipe system experiences plastic stresses. For smaller cracks, where the bending moments are high, the actual PRF is controlled by plasticity of the uncracked pipe, which is much larger than the plasticity that occurs locally at the crack. However, for large cracks where the bending moments are lower (closer to design conditions), the plasticity at the crack is equally important to the smaller amount of plasticity in the uncracked pipe for the actual PRF. Hence the plasticity of both the uncracked pipe and at the cracked sections is important to include in the determination of actual PRF values.
Modeling of Pipe System Behavior With Circumferential Surface Crack for Secondary Stress Margin Assessment
Authors: Uddin M. F. , Brust F. W. , Wilkowski G. M. , Kalyanam S. , Martin J. 
Published: October 2017

In flaw evaluation criteria, the design limits for the secondary stresses is frequently different than the primary stresses. The evaluation procedure for primary stresses are load-controlled based which is independent of pipe deformation. The evaluation procedures for secondary stresses are displacement controlled which are dependent on pipe deformation. Certain stress components such as thermal expansion, thermal striping, welding residual stress, misalignment/cold-springing, dynamic anchor motion are historically considered secondary stresses and their design limits are based on elastic stress analysis. In reality, there can be much more rotation/displacement of the pipe with nonlinear fracture behavior due to nonlinear material behavior and plasticity at the crack plane providing extra margins on the elastically calculated rotation values that come from uncracked-pipe design analyses. In assessing secondary stress margin, a secondary stress reduction factor is defined as the ratio of elastic-plastic moment to elastic moment. This is equivalent to another concept using a Plastic Reduction Factor (PRF) as well as the inverse of structural (or safety) factor (SF) in ASME Section XI flaw evaluation criteria for various service levels.
In this work, the secondary stress reduction factor was determined for a representative pipe system with multiple crack sizes, crack locations, and loading conditions. Nonlinear finite element (FE) analyses of a whole uncracked-pipe system were performed using ABAQUS® under various loading combinations to determine the critical locations for cracks in the pipe system. Next, FE analyses of the cracked-pipe system were carried out using cracked-pipe element — a methodology developed by the authors. Cracked-pipe system analyses were conducted for two loading conditions — one producing contained plasticity or single-hinge system and the other producing larger plasticity in the pipe system. Several analyses were conducted for each loading conditions with a combination of two crack sizes at two key locations. Secondary stress reduction factors were then calculated for both loading conditions in the pipe system. Finally, the margin in secondary stress was assessed for the pipe system by comparing the secondary stress reduction factors with that for straight pipe sections (determined for experimental bend tests) as well as with the recommended equivalent PRF and the equivalent ASME secondary stress correction factors.
Welding of Internally Clad X65 Pipes With Precipitation Strengthened Ni-Based Filler Metals
Authors: Penso Graciela C. , Alexandrov Boian T. 
Published: October 2017

X65 steel pipes internally clad with Alloy 625 used in subsea oil extraction are normally welded together with Alloy 625 filler metal. For pipe reeling applications, DNV-OS-F101 requires pipe girth welds to overmatch base metal yield strength with 100 MPa. Since Alloy 625 filler metal does not meet this requirement, Ni-base super alloys 718 and 282 were considered as potential welding consumables for reeling applications.
The solidification behavior in weld metal of these alloys diluted with Alloy 625 pipe ID cladding was evaluated using thermodynamic simulations. The response to precipitation hardening by multiple reheat cycles was studied by producing multilayer buildups with cold metal transfer (CMT) and pulsed gas metal arc welding (GMAWp) processes. Weld buildup of Alloy 718 exhibited insufficient hardening response and yield strength, while Alloy 282 met the DNV overmatch requirement. Successful narrow groove welding of X65 pipes with Alloy 282 was performed using CMT process. Welding parameter optimization allowed resolving centerline solidification cracking and lack of fusion defects. The weld metal yield strength was lower than in the multipass buildup, which was attributed to lower number of reheats in groove welding. Meeting the overmatch requirement for yield strength in Alloy 282 groove welds requires further parameter optimization.
Comparison Between Test and Analysis for Spent Nuclear Fuel Transportation Cask
Authors: Choi Woo-Seok , Cho Sangsoon , Seo Ki-Seog , Bang Kyoung-Sik , Lee Ju-Chan , Yu Seunghwan 
Published: October 2017

The storage and transport system are being developed in Korea. The spent fuels stored temporarily in wet storage at reactor site are scheduled to be transported to the interim storage in near term in Korea. To prepare the spent fuel transportation and storage, the dual purpose cask and concrete cask have been developed and submitted for the license approval.
Safety evaluation test was conducted with 1/3 scaled model and so was analysis. Since numerical simulation results can be different based on the analysis models, the reliable FE model was generated through several revising process. The comparison between simulation and test was conducted by numerical simulation using this FE model.
The reliable FE model made it possible to be proceeded stably by analysis and generated more realistic results compared to those of test. By the comparison between analysis and test results, the validity and appropriateness of the modeling technique and analysis methodology were verified.
Closed-Form Stress Intensity Factor Solutions for Deep Surface Cracks in Plates
Authors: Azuma Kisaburo , Li Yinsheng , Hasegawa Kunio , Xu Steven 
Published: October 2017

Materials made of Alloy 82/182/600 used in light-water reactors are known to be susceptible to stress corrosion cracking. It is known that the depth a of some cracks due to primary water stress corrosion cracking is larger than the half-length c. The stress intensity factor solution for cracks plays an important role to predict crack propagation and failure. However, Section XI of the ASME Boiler and Pressure Vessel Code does not provide the solutions for cracks with large aspect ratios a/c.
In this study, closed-form stress intensity factor influence coefficients for deep surface cracks in plates are discussed. The crack tip stress distribution is represented by a fourth degree polynomial equation. Influence coefficient tables obtained by using finite element analysis in previous studies are used for curve fitting. The closed-form solutions for the coefficient were developed at the surface points and the deepest points of the cracks with aspect ratio a/c ranged from 1.0 to 8.0. The solutions for the points where the stress intensity factor reaches maximum were also investigated.
Development of a Partial Structural Factor Approach for Direct Fracture Toughness Implementation Into the ASME Boiler and Pressure Vessel Code
Authors: Erickson Marjorie , Kirk Mark 
Published: October 2017

Direct implementation of best estimate fracture toughness models is a growing priority to enable an accurate assessment of the fracture safety of nuclear pressure boundary components for extended licensing periods. Models currently adopted for use in ASME Section XI of the Boiler and Pressure Vessel Code are based in linear elastic fracture mechanics methodologies developed 40 or more years ago at a time when drop weight tear tests and Charpy V-notch impact tests were the accepted standards used for characterizing a material’s resistance to brittle fracture. The current ASME guidance uses:
• a conservatively estimated RTNDT reference temperature,
• to index the linear elastic, lower-bound KIc curve that describes a material’s resistance to fracture, and
• then divides this lower-bound curve by a structural factor.
This approach includes multiple implicit and explicit treatments of uncertainty. It is not transparent, it produces inconsistent levels of conservatism, and it makes it difficult to incorporate improved knowledge, obtained from either new data or new models, into a flaw evaluation.
Code Case N830-R1 proposes use of a suite of best-estimate models to describe the temperature dependence and scatter of fracture toughness from lower shelf through upper shelf. CC-N830-R1 proposes that the 5th percentile lower bound of these models be used in flaw evaluations along with the current IWB 3611 and 3612 requirements that includes division of this 5th percentile curve by a structural factor. The intent in the next revision of this Code Case (Revision 2) is to move away from these current methods that inconsistently, and in some cases multiply, treat uncertainties.
Uncertainty treatment that relies on combinations of lower bound models, structural factors that do not consistently bound data, and margins needlessly complicate and confuse the characterization of material toughness and make it nearly impossible to assess the true level of safety. CC N830-R2 will therefore propose the use of a partial structural factor (PSF) approach. PSFs will be assigned to each of the key terms (i.e., toughness, stress, flaw size) in the fracture mechanics equations used in assessing safety of flaws. The value of each PSF will be defined to account for the uncertainty contribution of that term in a consistent manner. Partial safety factors have been successfully adopted by other codes and standards as will be further described in this paper, along with a proposed approach for defining partial safety factors for use with the CC N830-R1 models.
Experimental Damping of a Heat Exchange Tube With a Large Number of Supports in Air and Water
Authors: Park Tae-Jung , Ha Chang-Hoon , Cho Min-Ki , Kang Heung Seok , Lee Kang Hee 
Published: October 2017

The flow induced vibration occurs frequently in a steam generator in the nuclear power plant. The large-scale steam generator has a large number of tube supports whose cell has rhombus-type shape, and there is a tiny clearance between tube and its support grid. The damping is very complex because of non-linearity and randomness.
The experiment for damping was performed to investigate it with a number of 13 support spans both in air and water environment. The lower part of multi-span fixture was excited by root-mean-square random force with the range of 1∼10 newton to get the frequency response function. The half-power bandwidth method was applied to obtain the damping ratio. The sensitivity of a number of spans was investigated in the range of 9 ∼ 13. In addition, the damping was reviewed from a comparison with Pettigrew [1∼4] and ASME B&PV Code [5].
Laminated Type Isolation Device for Light Weight Structure Using Urethane Elastomer
Authors: Goda Kengo , Furuya Osamu , Imamura Kohei , Ishihana Kenta 
Published: October 2017

At the present, base isolation system has been recognized by general earthquake resistant technique since the Great Hanshin Earthquake 1995. The seismic isolation will be aggressively applied to not only architectural and civil structures but also various structures, because the effectiveness on seismic safety had been demonstrated again in the Great East Japan Earthquake. In generally, although the base isolation system is divided into laminated rubber bearing type and friction sliding bearing type. In the case of former type, shape factor, maximum or minimum outer shapes and so on are restricted by the material characteristics in visco-elastic material. In general, the isolation structure is used in high damping rubber. However, we pay attention to base isolation using urethane elastomer. Urethane elastomer has excellent elasticity, mechanical strength, abrasion resistance, weather resistance, oil resistance, impact resistance the absorbent, anti-vibration and excellent low-temperature properties. Furthermore, it is possible to impart various characteristics by a combination of isocyanate and polyol and chain extender, requires no large-scale apparatus, it has the advantage molecular design is easy.
In previous study, the research and development of laminated type base isolation device using urethane elastomer was carried out to upgrade a seismic safety for various structures. The fundamental characteristics was investigated from several loading test by using various experimental devices, and the design formula for the stiffness and equivalent damping coefficient is formulated as an approximate expression of mechanical characteristics until now. It was confirmed that urethane elastomer is not hardening up to 500% shear strain. Moreover, the experimental examination for aged deterioration in the urethane material has been continuously carried out. As the results, it was confirmed that the laminated type seismic isolation device using urethane elastomer is possible to develop as a practicable device from the stable mechanical properties as considering in design step.
In this study, the small-scale laminated type base isolation device using urethane elastomer is advanced to the direction of further technical upgrading and of scale down for light-weight structure as a sever rack. The first stage, basic properties of the urethane elastomer has been investigated by loading test. Furthermore, the design equation is created by loading test using urethane elastomer. The validity of the design equation has been confirmed. The second stage, the compression creep test with laminated type base isolation device has been investigated to confirm an effect on light-weight mechanical devices.