bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity Study of Boundary Conditions for a 9-Meter Drop of a Shielded Cask for Operational Handling of a Container of Liquid
Authors: Yaksh Michael C. , Babu Suresh
Published: December 2016

A shielded cask is used to move welded containers whose contents are liquid. The requirement controlling the design of the shielded cask was the 9-meter drop. Since the orientation of the cask is arbitrary, it is required to assume an orientation which would result in the most damage to the cask. For such drops the target is usually considered to be an unyielding surface. The shielded cask of interest is not designed with components to mitigate the damage due to such drops. The shielded cask contains a thick shell of lead which is considered to move and deform during the 9-meter drop. Additionally, the container of liquid is not physically attached to the cask, and is free to move within the confined space during the event as well. Each component has its own unique stiffness and mass characteristics which could result in a different dynamic response. Since the dynamic response of each component is different, the most damage to a particular component may be sensitive to the boundary conditions. The unyielding surface would maximize the damage to the impact surface of the cask, but as a result, could mitigate the maximum loading applied to other components of the cask. Most actual targets are comprised of concrete. The evaluations are performed using an explicit finite element computer code. Consequently, it is necessary to monitor certain energies, such as the hourglass energy or a sliding energy indicating the behavior of the contact surface associated with the target. These parameters confirm the accurate behavior of the elements comprising the finite element model. Given that components can have a different response, the hourglass energy may also vary. Varying the boundary conditions will affect these types of parameters.

In this paper, the authors present the results of a study of the effect of the boundary conditions on the shielded cask components response to the 9-meter drop. The primary orientation of interest is the end drop. The end drop maximizes the axial loading to the container. It is this orientation which could result in the most compression of the lead shield leading to increased radiation exposure. The container is considered as a pressure vessel and its integrity would be evaluated using the plastic strain based criteria contained in Section III, Division 3. The shielded cask, however, is not a pressure vessel and was evaluated using Section VIII, Division 2, Part 5. Both evaluations used the plastic strains and triaxiality factors determined from the drop evaluations.
Regulatory Perspective for the Definition of Probabilistic Acceptance Criteria for CANDU Pressure Tubes
Authors: Laxman Sankar , Carroll Blair , Jin John
Published: December 2016

For the assurance of fitness-for-service of CANDU Pressure Tubes (PTs), guidelines and acceptance criteria are provided in Canadian Standard Association (CSA) N285.8-15, Technical requirements for in-service evaluation of zirconium alloy pressure Tubes in CANDU reactors. With respect to the assessment of risk of operation associated with degradation mechanisms and aging of the PTs in the entire core of a given reactor Unit, Clause 7 of CSA N285.8 allows Licensee’s to use either a deterministic or probabilistic method to assess the likelihood of PT failures. When a probabilistic method is used, the Licensee is obligated to demonstrate that the combined frequency of PT failure(s) over the evaluation period, due to the various potential degradation mechanisms, is less than the maximum acceptable frequency provided in Table C.1 of CSA N285.8-15.

The maximum acceptable frequency provided in Table C.1 of CSA N285.8-15 was developed in the early-1990’s based on reactor operating experience and knowledge at that time, Station Siting Guides and Consultative Regulatory Guide C-006 (Revision 1). A task group was established by the CSA N285.8 Technical Steering Committee to re-evaluate the allowable failure frequencies to confirm that they remain relevant given the current state of knowledge and the additional evaluation tools available. This paper provides Canadian Nuclear Safety Commission staff views regarding the technical basis for revisions to the allowable frequencies based upon current industry practices in conducting probabilistic core assessments.
Nonlinear Finite Element Analysis of Pipe Bends Subjected to Inplane Bending
Authors: Akula Venkata M. K. , Martin David W.
Published: December 2016

Pipe bends are structural components that provide flexibility to accommodate length changes in pipelines while allowing fluid flow. Estimating the collapse load is critical to ensuring the structural integrity of the pipeline. This research discusses modeling and analysis of pipe bends utilizing the finite element method. Three-dimensional models utilizing elbow elements, shell elements, and brick elements are generated to predict the collapse moment of pipe bends subjected to in-plane loading. All simulation was performed using Abaqus.

To obtain a more physically-consistent response, material, geometric, and boundary nonlinearities are all included. A MPC user subroutine is utilized to capture the end behavior of the pipe bends correctly when utilizing shell and brick elements. Experimental data from two sources, available in literature, was used to evaluate the effect of the different element types on the predicted structural response.

Finally, utilizing the shell, brick, and the elbow elements, parameter sensitivity analyses are performed to identify the key parameters influencing the response of pipe bends. Multiple parameters are varied independently of each other to fully understand and capture their influence on the response. SIMULIA’s Isight software was used to automate the workflow and vary the model parameters about their respective baseline values.
The Effects of Discretization Errors on the High Frequency Content of In-Structure Response Spectra
Authors: Mertz Greg , Spears Robert , Houston Thomas
Published: December 2016

The next generation ground motion prediction equations predict significant high frequency seismic input for rock sites in the Central Eastern United States (CEUS). This high frequency motion is transmitted to basemat supported components and may be transmitted to components supported on elevated slabs. The existing ASCE 4 analysis requirements were initially developed based on seismic motions having lower frequencies, typical of ground motions in the Western United States (WUS). The adequacy of the existing ASCE 4 analysis requirements are examined using high frequency CEUS spectral shapes and the potential error inherent in using the existing approach to computing in structure response spectra is quantified. Modifications to reduce potential error in the existing ASCE 4 criteria are proposed.

In structure response spectra are typically generated for a subsystem given the time history response of a building region. The building time history response is based on analyses that use either modal time history superposition, direct integration or complex frequency response analysis of the building and supporting soil. Input to the building analyses consist of either real or synthetic discretized ground motion records. The discretized ground motion records are often based on recorded ground motion seeds and are often limited to a 0.005 second time step. Thus the time step of the seed record often limits the frequency content of the problem.

Both the building analyses and in structure response spectra subsystem analysis may interpolate the discretized ground motion records to obtain stable results. This interpolation generates errors that are propagated through the analyses used to calculate in structure response spectra. These errors may result in extraneous high frequency content in the in structure response spectra. Errors are quantified by comparison of time history parameters, Fourier components and in structure response spectra.
Proposed Updates to Appendix D SIF and K-Factors for Branch Connections
Authors: Becht Charles , Paulin Anthony , Stonehouse Mark
Published: December 2016

The latest revision of B31J, which is currently in draft mode, introduces new formulations for stress intensification factors (SIF’s) and flexibility factors (k’s) for various branch components. This paper explores the background of the work that has gone into the latest B31J document, draft revision 12 – 2015. Trends based on different geometric parameters are presented with respect to how conservative or non-conservative the current (2014) B31.3 Code is versus the data which serves as the basis of the new B31J formulations. Eliminating non-conservative evaluations will help eliminate the small subset of piping systems that likely do not provide the Codes’ intended separation between design and failure. More importantly, eliminating overly-conservative evaluations will reduce the material and man-time costs associated with larger diameter piping systems (8"NPS and larger and D/T>15). It is believed that this cost savings, and reduced need for unnecessary rerouting will be the most significant benefit realized by the implementation of B31J. Just as with WRC 329 three decades earlier, B31J also recognized a number of additional deficiencies beyond the current alignment scope caused principally due to changes in manufacturing, quality control and testing. Future revisions of B31J will hopefully continue to support a uniform, practical, and safe design environment for piping systems.
Pipeline Design Method Against Large Displacement of Strike-Slip Fault
Authors: Oda Keita , Ishihara Takahiro , Miyajima Masakatsu
Published: December 2016

This study proposes a method for designing a water pipeline system against fault displacement by incorporating earthquake resistant ductile iron pipes (ERDIPs). An ERDIP pipeline is capable of absorb the large ground displacements that occur during severe earthquakes by movement of its joint (expansion, contraction and deflection) and the use of the joint locking system. Existing ERDIP pipelines have been exposed to several severe earthquakes such as the 1995 Kobe Earthquake and the 2011 Great East Japan Earthquake, and there has been no documentation of their failure in the last 40 years.

In the case of a pipeline that crosses a fault, there is the possibility of the occurrence of a local relative displacement between the pipeline and the ground. It is known that an ERDIP pipeline withstands a fault of axial compression direction by past our study. Hence, this present study was targeted at developing a method for designing an ERDIP pipeline that is capable of withstanding a strike-slip fault of axial tensile direction for a pipeline. This was done by FEM analysis wherein the ERDIPs and spring elements were used to model the soil and ERDIP joints.

An ERDIP pipeline can accommodate a fault displacement of about 2 m by joint expansion/contraction and deflection, while maintaining the stress in the pipeline within the elastic limit. However, additional countermeasure is required when the fault displacement exceeds 2 m because such could stress the pipeline beyond the elastic limit.

The use of large displacement absorption unit is an effective countermeasure for displacements exceeding 2 m. The expansion/contraction capacity of a unit is 10 times that of an ERDIP joint and it is able to absorb a locally-concentrated axial displacement of the pipeline. It was confirmed in the present study that an ERDIP pipeline with large displacement absorption unit, referred to as a large displacement absorption system, could accommodate fault displacement in excess of 2 m within the elastic stress range of the pipeline.
Temperature Effects on Guided Ultrasonic Wave Sensing for Dry Cast Storage Health Monitoring
Authors: Sun Xiaoyi , Ma Linlin , Howden Stephen , Lin Bin , Yu Lingyu
Published: December 2016

This paper discusses the temperature effects of using guided ultrasonic wave sensing in damage detection for structural health monitoring (SHM) for nuclear dry cast storage system (DCSS). The sensing capability of GUW under temperature effect is investigated and presented in this paper. Two types of sensors are studied: (a) piezoelectric wafer active sensor (PWAS) and (b) optical fiber Bragg grating (FBG) sensors. Temperature effect on the free sensors was first tested in experiments. Pristine specimens instrumented with PWAS are then investigated through sensing tests at selected temperatures. Parameters in wave modes are obtained and evaluated for changes in the waveforms at different temperatures. The investigation continues to evaluate the damage detection capability of GUW under temperature influence. The potential of using GUW for damage detection with temperature effect applied for DCSS application is discussed and concluded in the end, as well as suggestions for further work.
Combined Extended Finite Element Method and Cohesive Element for Fracture Analysis
Authors: Jiang Y. , Xuedong Chen , Fan Zhichao
Published: December 2016

Extended finite element method (XFEM) is a versatile tool for fracture mechanics. Due to its excellent property, XFEM is widely used in research and engineering. On the other hand, cohesive element is a good option for interface delamination in composite materials. In order to take advantage of these two methods, combined XFEM and cohesive element method is developed for fracture analysis in composite materials in two-dimension. In this method, XFEM is used to simulate matrix fracture, and cohesive element is used to simulate delamination between layers. Due to the differences in the construction of these two methods, special attention is paid to the intersection of these two methods. The new method is applied to the fracture analysis of composite materials. The results show this method has excellent property as expected. This method shows potential application in fracture analysis of composite materials.
Further Evaluation of the Structural Integrity of the Chinese Qinshan 300-MWe Reactor Pressure Vessel Under Pressurized Thermal Shock Using the Master Curve Method
Authors: Cao Yupeng , He Yinbiao , Hu Hui , Li Hui
Published: December 2016

Pressurized thermal shock (PTS) is a potential major threat to the structural integrity of the reactor pressure vessel (RPV) in a nuclear power plant. An earlier work on the PTS analysis of the Chinese Qinshan 300-MWe RPV was performed with the single parameter fracture mechanics method by Shanghai nuclear engineering research and design institute (SNERDI). The integrity analysis of this RPV under PTS was re-evaluated using the Master Curve method later in the paper PVP2015-45577[1]. The objective of this paper is to expand on the previous work, covering more crack geometries and transients to discuss the differences in the use of Master curve based and single parameter linear elastic fracture mechanics based method for PTS analysis. Attempts are made to consider additional size adjustment to the long crack front, which yields more reasonable maximum allowable transition temperature.
Elevated Temperature Analysis in BPV Code Section VIII Division 2 Part 5
Authors: Mann J. Adin , Nadarajah Chithranjan , Hantz Benjamin F. , Krishnamurthy Sujay
Published: December 2016

The Working Group on Design by Analysis in collaboration with the Working Group on Elevated Temperature Construction has developed a proposal for elevated temperature analysis in the ASME Boiler and Pressure Vessel Code Section VIII Division 2 Part 5, Design by Analysis. Elevated temperature is defined as the temperature where the allowable stress is time-dependent, that is, controlled by creep. The proposal is divided into the potential failure modes: rupture, ratcheting, fatigue, buckling, and service conditions. Linear elastic and inelastic analysis options rely on published approaches. The focus of the presentation will be on the Linear Elastic analysis options which include a fatigue screening, a ratcheting assessment, and an assessment for burst. Multiple conditions are allowed in the analysis. The proposed rules will be presented.
Defect Tolerance Assessment for ABWR Nozzle Crotch Corner
Authors: Hirokawa Fumihito , Hayashi Masaaki , Masuda Minoru , Mabuchi Yasuhiro , Yamamoto Yukinori , Iwamatsu Fuminori , Miyazaki Katsumasa , Johnson David
Published: December 2016

In the nuclear industry, demands on the structural integrity reliability of metal components are always increasing. The quantification of allowable defects in pressure vessels should therefore draw on advanced structural integrity assessment procedures. In the UK, R6 [1] is the main procedures used for defect tolerance assessment (DTA). In this paper, the overall evaluation procedure of DTA using R6 applied to the Main Steam (MS) nozzle crotch corner of the Advanced Boiling Water Reactor (ABWR) is presented. At the nozzle crotch corner region, high stresses, including through-wall bending stresses from the local structural discontinuity, were present. These bending stresses have been categorised as secondary. R6 conservatively implies such bending stresses may need to be categorised as primary, to allow for the possibility of elastic follow-up. To support application as a secondary stress, an elastic-plastic finite element analysis has been performed to evaluate the J-integral for the nozzle crotch corner. The resulting values of J, when compared to the stress intensity factor and collapse solutions used for the assessment, showed that treating the bending stress as secondary maintained sufficient margin, indicating conservatism. Finally, the DTA results of the nozzle crotch corner are presented to determine the defect tolerance criteria. This includes calculating the limiting defect size at the start of plant life when considering the end of life critical defect size and through life Fatigue Crack Growth (FCG).
Experimental Investigation of Kevlar KM2Plus Nano-Reinforced Laminated Composite Thermo-Mechanical Properties
Authors: Mourad Abdel-Hamid I. , Ayad Omar G. , Rahman Ashfakur , Hilal-Alnaqbi Ali , Abu-Jdayil Basim I.
Published: December 2016

This work is concerned with the synthesis and characterization of Multi-Walled Carbon Nanotube (MWCNT) reinforced Kevlar KM2Plus composites with various MWCNT contents (0.2, 0.3, 0.4, 0.5, 0.6, and 0.8 wt. %), by the wet lay-up technique. These samples were experimentally investigated for their thermo-mechanical properties using Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), tensile testing and three-point bending techniques. The mechanical properties showed remarkable improvement with increasing MWCNT wt.% up to certain content. The results revealed that the addition of MWCNT fillers has no significant effect on the thermal stability of the composites.
Deterministic and Probabilistic PTS Study for a Reactor Pressure Vessel Considering Plume Cooling Effects
Authors: Qian Guian , Niffenegger Markus , Sharabi Medhat , Lafferty Nathan
Published: December 2016

A reactor pressure vessel (RPV) is assumed to be subjected to pressurized thermal shocks (PTSs) as a result of the emergency cooling water injected during a loss-of-coolant accident (LOCA). The cooling flow is not homogeneous but typically in a plume shape (stripe cooling) flowing from the cold leg through the inlet nozzles. This paper aims to analyze the non-uniform cooling effect on the RPV integrity.

In this paper, both deterministic and probabilistic methods are used to analyze the integrity of a model RPV subjected to PTS. RELAP5, GRS-MIX, CFD and other semi-analytical methods are used to analyze the transient with and without considering plume cooling effect. Finite element method (FEM), extended finite element method (XFEM) and weight function method are used to calculate KI of the postulated cracks. The FAVOR code is used to calculate the conditional probabilities for crack initiation and failure of the RPV considering different crack distributions.

KI based on CFD input is the highest, followed by that based on reference transient, GRS-MIX and RELAP5. Peak KI of the cracks inside the plume increases about 33% compared with that outside. According to the maximum criteria, the maximum allowed RTNDT are 56.9 °C, 90.2 °C, 98 °C, 115.7 °C and 136.2 °C for the crack in the nozzle region based on CFD transient, the cracks in the ring region based on the CFD, reference data, GRS-MIX and RELAP5 calculated transient, respectively. These values are 36 °C, 68.5 °C, 73 °C, 81 °C and 104 °C according to the tangent criteria. The conditional probability inside the plume is more than nine orders of magnitude higher than outside the plume. Considering plume cooling effects increases the total failure frequency by 1–2 orders of magnitude. In order to be conservative, it is necessary to consider the plume effect in the integrity assessment.
Root Cause Analysis of the Unexpected Behaviour of a Flaked Material Under Irradiation and Transferability to the Doel 3/Tihange 2 Reactor Pressure Vessels
Authors: De Bruycker Evy , De Vroey Séverine , Hallet Xavier , Stubbe Jacqueline , Nardone Steve
Published: December 2016

During the 2012 outage at Doel 3 (D3) and Tihange 2 (T2) Nuclear Power Plants (NPP), a large number of nearly-laminar indications were detected mainly in the lower and upper core shells. The D3/T2 shells are made from solid casts that were pierced and forged.

Restart authorization in 2013 was accompanied by a number of “mid-term” requirements, to be completed during the first operating cycle after the restart. One of these requirements was the mechanical testing of irradiated specimens containing hydrogen flakes. These tests showed unexpected results regarding the shift in the Reference Temperature for Nil Ductility Transition (RTNDT) of the flaked material VB395 (Steam Generator shell rejected because of flakes) after irradiation.

This paper presents the root cause analysis of this unexpected behaviour and its transferability (or not) to the D3/T2 Reactor Pressure Vessels (RPVs).

A mechanistic and a manufacturing based approach were used, aiming at identifying the microstructural mechanisms responsible for the atypical embrittlement of VB395 and evaluating the plausibility of these mechanisms in the D3/T2 RPVs.

This work was based on expert’s opinions, literature data and test results. Both flaked and unflaked samples have been investigated in irradiated and non-irradiated condition.

All hydrogen-related mechanisms were excluded as root cause of the unexpected behaviour of VB395. Two possible mechanisms at the basis of the atypical embrittlement of VB395 were identified, but are still open to discussion. These mechanisms could be linked to the specific manufacturing history of the rejected VB395 shell.

Since the larger than predicted shift in transition temperature after irradiation of VB395 is not linked with the hydrogen flaking and since none of the specific manufacturing history features that are possible root causes are reported for the D3/T2 RPVs, the D3/T2 shells should not show the unexpected behaviour observed in VB395.
A Super-Parametric Approach to Estimating Accuracy and Uncertainty of the Finite Element Method (*)
Authors: Rainsberger Robert B. , Fong Jeffrey T. , Marcal Pedro V.
Published: December 2016

A finite element method (FEM)-based solution of an industry-grade problem with complex geometry, partially-validated material property databases, incomplete knowledge of prior loading histories, and an increasingly user-friendly human-computer interface, is extremely difficult to verify because of at least five major sources of errors or solution uncertainty (SU), namely, (SU-1) numerical algorithm of approximation for solving a system of partial differential equations with initial and boundary conditions; (SU-2) the choice of the element type in the design of a finite element mesh; (SU-3) the choice of a mesh density; (SU-4) the quality measures of a finite element mesh such as the mean aspect ratio.; and (SU-5) the uncertainty in the geometric parameters, the physical and material property parameters, the loading parameters, and the boundary constraints. To address this problem, a super-parametric approach to FEM is developed, where the uncertainties in all of the known factors are estimated using three classical tools, namely, (a) a nonlinear least squares logistic fit algorithm, (b) a relative error convergence plot, and (c) a sensitivity analysis based on a fractional factorial orthogonal design of experiments approach. To illustrate our approach, with emphasis on addressing the mesh quality issue, we present a numerical example on the elastic deformation of a cylindrical pipe with a surface crack and subjected to a uniform load along the axis of the pipe.
Heat Transfer Enhancement for Heat Exchanger Applications: Use of Surface Hydrophobicity
Authors: Kafarakis S. T. , Mastrokalos M. E. , Papadopoulos C. I. , Kaiktsis L.
Published: December 2016

Hydrophobic surfaces, enabling flow slip past a solid boundary, can potentially be effective for heat transfer enhancement in heat exchanger applications. The scope of the present work is the computational study of forced convection heat transfer in flow past a hydrophobic cylinder, maintained at constant surface temperature. Hydrophobic surfaces are applied in flow control applications, since they enable flow slip past a solid boundary; as a result, they can contribute to flow stabilization. At the same time, hydrophobic surfaces are a potential means for heat transfer enhancement. In the present study, a computational investigation of forced convection heat transfer in cross-flow past a circular hydrophobic cylinder is performed by means of Computational Fluid Dynamics; the effects of hydrophobicity on flow stability and forces are also quantified. Here, low Reynolds number values, Re, are considered, whereas the Prandtl number, Pr, is maintained constant, equal to unity. Hydrophobicity is modelled by means of the Navier model.

For slip conditions applied on the entire cylinder surface, the present results demonstrate that the stabilizing effect of increasing the non-dimensional slip length, b* = b/D, b being the slip length and D the cylinder diameter, is accompanied by a simultaneous enhancement of heat transfer. In particular, the time-averaged mean Nusselt number, Num, is found to be an increasing function of both b* and Re. Further, it is shown that, for the same levels of b*, an equivalent heat transfer rate can be achieved by substantially reducing the extent of the hydrophobic region, in particular by excluding the rear stagnation point region, i.e. at a significantly reduced cost. Overall, the present results illustrate that implementing partial hydrophobicity results in a substantial enhancement of heat transfer rates and a simultaneous (partial or full) suppression of the wake unsteadiness.
A Numerical Study on Crack Growth Resistance Curve of X70 Steels
Authors: Paredes Marcelo , Zelenak Paul , Wierzbicki Tomasz
Published: December 2016

In this work a phenomenological approach is employed for fracture initation and propagation in SENT specimens. Modified Mohr-Coulomb (MMC) fracture criterion establish the initiation of damage/fracture at the critical material point and the post-initation softening controls its rate of propagation. By means of a tridimensional mixed stress state (equivalent plastic strain, εp; Triaxiality, η; and Lode angle, θ) the nature of the growing crack front can be explained.
Value of Information and Hypothesis Testing Approaches for Sample Size Determination in Engineering Component Inspection: A Comparison
Authors: Higo Eishiro , Pandey Mahesh D.
Published: December 2016

A sample size determination method is developed for a two-action problem that represents a component maintenance scenario requiring current state estimation. For safety and generation efficiency, each component of a nuclear power plant must be regularly inspected. In terms of safety, the larger the sample size inspected, the less the uncertainty about current and future states of the components; however, such inspections are expensive. Thus, sample size determination becomes an important problem. A key idea for solving this problem is the Value of Information (VoI) and its derivation: the Expected Net Gain of Sampling (ENGS). The ENGS is a function of sample size and represents by how much a decision maker benefits from the observed data. By maximizing the ENGS, the optimal sample size is determined in terms of cost-benefit analysis.
Yield Strength Reduction Factor of Nonlinear SDOF Systems on the Supporting Structures
Authors: Tamura Ichiro , Matsuura Shinichi , Shimazu Ryuya
Published: December 2016

Equipment installed on the supporting structure responds to the earthquake floor motion, which is strongly amplified by the structural response of the supporting structure. The required yield strength of equipment can be reduced by allowing inelastic deformation of the supporting structure and its equipment. Inelastic behavior of the supporting structure can significantly reduce elastic floor response spectra, especially their peak values. Furthermore, the allowance of inelastic deformation of equipment in strongly amplified spectral region produces a significant reduction in the required yield strength of equipment.

In this study, we discussed inelastic behavior of single-degree-of-freedom(SDOF) systems installed on the supporting structures by using constant-ductility floor response spectra. Constant-ductility floor response spectra readily provide the yield strength of a SDOF system necessary to limit the ductility demand imposed by an earthquake floor motion to a specified value. Based on these discussions, we propose simple and conservative equations of the yield strength reduction factor of nonlinear inelastic SDOF systems with the natural period, the ductility factor and the stiffness ratio for earthquake floor motions.
Optimal Weld Design of Plug Repair in Reactor Pressure Vessel With 3D Computational Weld Modeling
Authors: Brust Frederick W. , Barton David
Published: December 2016

A bottom mounted instrument (BMI) nozzle in a European nuclear pressure vessel experienced some cracking caused by primary water stress corrosion cracking (PWSCC). Rather than repair the nozzle a decision was made to place a plug over the nozzle hole since this particular instrument panel could be removed in the reactor. The plug repair will be installed remotely during an outage and consists of performing the welding from a location near the top of the vessel which is more than 20 meters away. This makes the design of the repair critical.

This paper uses 3D computational weld analyses to design the repair. Considerations for the design include the possibility of repair welds, proper seating of the plug (distortion control), weld residual stress control, and load applications to the plug during the repair process. Computational weld modeling permitted a proper design to be realized and helped in the regulatory certification process for the plug repair. These are discussed in this paper.
Prediction of Creep Life on Notched Bar Specimens of Grade 92 Steel
Authors: Shigeyama Haruhisa , Takahashi Yukio , Parker Jonathan
Published: December 2016

Creep tests on two kinds of circumferentially notched round bar specimens as well as plain bar specimen were performed to obtain the multiaxial and uniaxial creep data. Creep damage models of strain fraction and energy fraction rule were developed using these creep data. Then creep damage analyses using a finite element software, MSC Marc, were carried out on notched specimens of both types and creep failure lives were predicted using the creep damage models of classical life fraction rule and developed strain or energy fraction rule. Experimental failure lives of all the conditions of notched specimens were compared with analytical results. As a result, creep failure lives obtained by life fraction rule were underestimated in the short term region and overestimated in the long term region. On the other hands, it is apparent that the majority of creep failure lives obtained by strain and energy fraction rule were predicted with an accuracy within a factor of two. Furthermore, some interrupted creep tests and creep void observations were conducted on the notched specimens of both types. The distributions of creep void number density were in good agreement with the distributions of creep damage calculated by finite element analyses.
Characteristics of Turbulence and Drag Forces on Foreign Objects in Tube Arrays
Authors: Mureithi Njuki , Cucuel Bastien , Saber-Cherif Karim , Olala Stephen , Ashrafi Farzad
Published: December 2016

Steam generator tube wear due to foreign objects (FOs) is a significant industry problem. Removal of foreign objects comes with challenges related to accessibility and the environment inside the steam generator. It is therefore of interest to estimate the rate of wear due to foreign objects lodged within the SG; particularly in the tube-sheet region. To estimate wear, the fluid forces acting on the FO are a key input.

Much remains unknown regarding the characteristics of fluid forces acting on small objects located within tube arrays. In the work reported here, an exploratory study of fluid forces acting on complex geometry objects was done. Force measurements were conducted in a wind-tunnel on a range of objects to investigate the effect of object geometry on the drag coefficient and the parameters which may be used to develop drag coefficient correlations.

Turbulence forces acting on FOs in a tube array were found to be intimately related to turbulence forces acting on the tubes themselves. A direct relation between the corresponding force PSDs, via turbulence force correlations, is reported. This is a potentially useful result with regard to the nature of fluid forces acting on foreign objects in general.
Development of Evaluation Procedures for Crack Initiation From In-Service Flaws in CANDU Zr-2.5Nb Pressure Tubes With Hydrogen
Authors: Cho David , Xu Steven X. , Scarth Douglas A. , Shek Gordon K.
Published: December 2016

Flaws found during in-service inspection of CANDU(1) Zr-2.5Nb pressure tubes include fuel bundle scratches, debris fretting flaws, fuel bundle bearing pad fretting flaws and crevice corrosion flaws. These flaws are volumetric and blunt in nature. Crack initiation from in-service flaws can be caused by the presence of hydrogen in operating pressure tubes and resultant formation of hydrided regions at the flaw tips during reactor heat-up and cool-down cycles. Zr-2.5Nb pressure tubes in the as-manufactured condition contain hydrogen as an impurity element. During operation, the pressure tube absorbs deuterium, which is a hydrogen isotope, from the corrosion reaction of the zirconium with the heavy water coolant. In addition, deuterium ingresses into the pressure tube in the rolled joint region. The level of hydrogen isotope in pressure tubes increases with operating time.

Over the years, Canadian CANDU industry has carried out extensive experimental and analytical programs to develop evaluation procedures for crack initiation from in-service flaws in Zr-2.5Nb pressure tubes. Crack initiation experiments were performed on pressure tube specimens with machined notches to quantify resistance to crack initiation under various simulated flaw geometries and operating conditions such as operating load and hydrogen concentration. Predictive engineering models for crack initiation have been developed based on understandings of crack initiation and experimental data. A set of technical requirements, including engineering procedures and acceptance criteria, for evaluation of crack initiation from in-service flaws in operating pressure tubes has been developed and implemented in the CSA Standard N285.8. A high level review of the development of these flaw evaluation procedures is described in this paper. Operating experience with the application of the developed flaw evaluation procedure is also provided.
Deterministic Technical Basis for Re-Examination Interval of Every Second Refueling Outage for PWR Reactor Vessel Heads Operating at Tcold With Previously Detected PWSCC
Authors: White Glenn , Fuhr Kevin , Burkardt Markus , Harrington Craig
Published: December 2016

Plant operating experience with Alloy 600 reactor pressure vessel top head penetration nozzles in U.S. PWRs shows that the inspection intervals prescribed by ASME Code Case N-729-1 have been successful in managing the PWSCC concern. No through-wall cracking has been observed in the U.S. after the first in-service volumetric or surface examination was performed on all CRDM or CEDM nozzles in a given head. The current inspection intervals have facilitated identification of any PWSCC in its early stages, with small numbers of nozzles affected and substantial margins to leakage at the five affected heads operating at Tcold. MRP-395 demonstrated through both deterministic and probabilistic analyses that the inspection intervals of Code Case N-729-1 remain valid to conservatively address the PWSCC concern.

This paper supplements MRP-395 with additional deterministic crack growth analyses coupled with assessments of the PWSCC indications detected in heads operating at Tcold. The supplemental deterministic assessments presented in this paper demonstrate the acceptability of a 36-month volumetric or surface inspection interval for heads with previously detected PWSCC and that operate at Tcold. Until Code Case N-729-5 is approved by U.S. NRC, use of the 36-month interval in the U.S. for such heads would require review and approval by U.S. NRC of a relief request submitted by the licensee.
Comprehensive understanding of chamber conditioning effects on plasma characteristics in an advanced capacitively coupled plasma etcher
Authors: Baek Kye Hyun , Lee Eunwoo , Klick Michael , Rothe Ralf
Published: December 2016

An advanced capacitively coupled plasma etcher with two frequencies and additional direct current is characterized with complementary sensors. Due to the restrictive boundary conditions of the manufacturing environment, which the authors had to take into account, applicable plasma sensors are limited. Thus, the plasma parameters depending on the center, wall, sheath, and cathode regions are extracted separately based on the tool parameters, optical emission spectroscopy, and self-excited electron spectroscopy. One main target of this investigation is a cross verification of complementary sensor data and a deeper understanding. Due to the complex chamber setup, the authors use a chemically simple system of an Ar plasma with a blank Si wafer as the substrate. It is found that the removal of SiO2 and sputtering Si from the cathode and wafer changes the chamber condition and thus causes changes in the plasma characteristics. The established plasma process model comprises a change in secondary electron emission caused by changing the surface condition and a subsequent change in collisionless electron heating, in particular, in the case of applied low frequency power. Current electron heating models and conditioning models are used for cross verification of the plasma process model. It indicates that both chemical and electrical aspects to chamber conditioning should be considered in multiple frequency driven plasma etchers. The results presented in this paper are expected to contribute to the understanding of the interaction of the chamber conditioning effects and plasma parameters in advanced plasma etchers for sub-20 nm devices.
KR12 peptide associated with cyclodextrin: Antimicrobial and antitumor activities
Authors: Teixeira Karina I. R. , Cortés Maria E. , Santos Robson A. S. , de Oliveira Fábio , Sinisterra Ruben D.
Published: December 2016

The aim of this study was to determine the physical properties and antimicrobial and antiproliferative effects of the KR12 peptide complexed with 2-hydroxypropyl-β-cyclodextrin (Hp-βCd) in vitro. The KR12:Hp-βCd composition was evaluated for particle size and its zeta (ζ)-potential in the presence and absence of cells. Antimicrobial activity against Streptococcus mutans, Actinobacillus actinomycetemcomitans, and Porphyromonas gingivalis for the peptide alone or associated was evaluated by minimal inhibitory concentration. The cytotoxicity of the peptide and composition toward fibroblasts, Caco-2 cells, and A431 cells was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide; thiazolyl blue assay and hemolysis assay. Membrane integrity was analyzed by the lactate dehydrogenase assay. KR12:Hp-βCd decreased the peptide concentration required for the antimicrobial effect. Moreover, this composition was able to modify cell surface parameters, such as ζ-potential, and alter the degree of hemolysis induced by KR12. However, the KR12:Hp-βCd and KR12 alone alter the zeta potential of cells to a similar extent, suggesting a similar level of membrane interaction. The peptide alone inhibited the proliferation of Caco-2 and A431 cells more efficiently than KR12:Hp-βCd (p < 0.001), but did not show significant cytotoxic effects via the dehydrogenase lactate assay. Both substances were effective in inhibiting the growth of odontopathogenic bacteria, as well as inhibiting Caco-2 epithelial cells. These observations highlight the potential antimicrobial and antiproliferative effects of KR12 peptide alone or associated with Hp-βCd.
Alumina films as gas barrier layers grown by spatial atomic layer deposition with trimethylaluminum and different oxygen sources
Authors: Franke Sebastian , Baumkötter Matthias , Monka Carsten , Raabe Sebastian , Caspary Reinhard , Johannes Hans-Hermann , Kowalsky Wolfgang , Beck Sebastian , Pucci Annemarie , Gargouri Hassan
Published: December 2016

Alumina layers were grown from trimethylaluminum (TMA) and water, ozone as well as an oxygen plasma as co-reactants in low temperature spatial atomic layer deposition (ALD). The influence of the amount of precursor, the precursor exposure duration, and substrate temperature were investigated with respect to the growth rate while employing different oxygen sources. The TMA/water process provided alumina (AlOx) films with superb film quality as shown by infrared measurements. Ozone-based processes allowed lower substrate temperatures. Nevertheless, carbon residuals in different binding states were found within the bulk material. However, the carbon impurities have no impact on the barrier performance, since 50 nm AlOx grown by TMA either with water or ozone exhibited a water vapor transition rate in the range of 10−6 g/m2/day. However, when our home-built microwave plasma source was applied in a remote configuration, the water vapor transition rate was one order of magnitude higher due to a reduction in film quality. Furthermore, a TMA utilization of ∼50% demonstrated the highly cost-effective spatial ALD concept as a deposition technique which is very suitable for industrial deposition applications.
Inductively coupled BCl3/Cl2/Ar plasma etching of Al-rich AlGaN
Authors: Douglas Erica A. , Sanchez Carlos A. , Kaplar Robert J. , Allerman Andrew A. , Baca Albert G.
Published: December 2016

Varying atomic ratios in compound semiconductors is well known to have large effects on the etching properties of the material. The use of thin device barrier layers, down to 25 nm, adds to the fabrication complexity by requiring precise control over etch rates and surface morphology. The effects of bias power and gas ratio of BCl3 to Cl2 for inductively coupled plasma etching of high Al content AlGaN were contrasted with AlN in this study for etch rate, selectivity, and surface morphology. Etch rates were greatly affected by both bias power and gas chemistry. The authors detail the effects of small variations in Al composition for AlGaN and show substantial changes in the etch rate with regard to bias power as compared to AlN.
Effects of background noise on acoustic characteristics of Bengalese finch songs
Authors: Shiba Shintaro , Okanoya Kazuo , Tachibana Ryosuke O.
Published: December 2016

Online regulation of vocalization in response to auditory feedback is one of the essential issues for vocal communication. One such audio-vocal interaction is the Lombard effect, an involuntary increase in vocal amplitude in response to the presence of background noise. Along with vocal amplitude, other acoustic characteristics, including fundamental frequency (F0), also change in some species. Bengalese finches (Lonchura striata var. domestica) are a suitable model for comparative, ethological, and neuroscientific studies on audio-vocal interaction because they require real-time auditory feedback of their own songs to maintain normal singing. Here, the changes in amplitude and F0 with a focus on the distinct song elements (i.e., notes) of Bengalese finches under noise presentation are demonstrated. To accurately analyze these acoustic characteristics, two different bandpass-filtered noises at two levels of sound intensity were used. The results confirmed that the Lombard effect occurs at the note level of Bengalese finch song. Further, individually specific modes of changes in F0 are shown. These behavioral changes suggested the vocal control mechanisms on which the auditory feedback is based have a predictable effect on amplitude, but complex spectral effects on individual note production.
Congress votes on sweeping biomedical bill
Authors: Kaiser Jocelyn , Mervis Jeffrey , Servick Kelly
Published: December 2016

NIH would get $4.8 billion for key research initiatives.
Reactivation of latent working memories with transcranial magnetic stimulation
Authors: Rose Nathan S. , LaRocque Joshua J. , Riggall Adam C. , Gosseries Olivia , Starrett Michael J. , Meyering Emma E. , Postle Bradley R.
Published: December 2016

A pulse of random activity is sufficient for a brain network to retrieve a dormant activity state.
Respiratory Syncytial Virus: Infection, Detection, and New Options for Prevention and Treatment
Authors: Griffiths Cameron , Drews Steven J. , Marchant David J.
Published: December 2016

Respiratory syncytial virus (RSV) infection is a significant cause of hospitalization of children in North America and one of the leading causes of death of infants less than 1 year of age worldwide, second only to malaria. Despite its global impact on human health, there are relatively few therapeutic options available to prevent or treat RSV infection. Paradoxically, there is a very large volume of information that is constantly being refined on RSV replication, the mechanisms of RSV-induced pathology, and community transmission. Compounding the burden of acute RSV infections is the exacerbation of preexisting chronic airway diseases and the chronic sequelae of RSV infection. A mechanistic link is even starting to emerge between asthma and those who suffer severe RSV infection early in childhood. In this article, we discuss developments in the understanding of RSV replication, pathogenesis, diagnostics, and therapeutics. We attempt to reconcile the large body of information on RSV and why after many clinical trials there is still no efficacious RSV vaccine and few therapeutics.