bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Cooling Technologies for Xeon Phi™ Based High Performance Computing Clusters
Authors: Sarangi Suchismita , Kuhn Will A. , Rider Scott , Wright Claude , Krishnan Shankar 
Published: November 2015

Efficient and compact cooling technologies play a pivotal role in determining the performance of high performance computing devices when used with highly parallel workloads in supercomputers. The present work deals with evaluation of different cooling technologies and elucidating their impact on the power, performance, and thermal management of Intel® Xeon Phi™ coprocessors. The scope of the study is to demonstrate enhanced cooling capabilities beyond today’s fan-driven air-cooling for use in high performance computing (HPC) technology, thereby improving the overall Performance per Watt in datacenters. The various cooling technologies evaluated for the present study include air-cooling, liquid-cooling and two-phase immersion-cooling. Air-cooling is evaluated by providing controlled airflow to a cluster of eight 300 W Xeon Phi coprocessors (7120P). For liquid-cooling, two different cold plate technologies are evaluated, viz, Formed tube cold pates and Microchannel based cold plates. Liquidcooling with water as working fluid, is evaluated on single Xeon Phi coprocessors, using inlet conditions in accordance with ASHRAE W2 and W3 class liquid cooled datacenter baselines. For immersion-cooling, a cluster of multiple Xeon Phi coprocessors is evaluated, with three different types of Integrated Heat Spreaders (IHS), viz., bare IHS, IHS with a Boiling Enhancement Coating (BEC) and IHS with BEC coated pin-fins. The entire cluster is immersed in a pool of Novec 649 (3M fluid, boiling point 49 °C at 1 atm), with polycarbonate spacers used to reduce the volume of fluid required, to achieve target fluid/power density of ∼ 3 L/kW. Flow visualization is performed to provide further insight into the boiling behavior during the immersion-cooling process.
Performance per Watt of the Xeon Phi coprocessors is characterized as a function of the cooling technologies using several HPC workloads benchmark run at constant frequency, such as the Intel proprietary Power Thermal Utility (PTU), and industry standard HPC benchmarks LINPACK, DGEMM, SGEMM and STREAM. The major parameters measured by sensors on the coprocessor include total power to the coprocessor, CPU temperature, and memory temperature, while the calculated outputs of interest also include the performance per watt and equivalent thermal resistance. As expected, it is observed that both liquid and immersion cooling show improved performance per Watt and lower CPU temperature compared to air-cooling. In addition to elucidating the performance/watt improvement, this work reports on the relationship of cooling technologies on total power consumed by the Xeon-Phi card as a function of coolant inlet temperatures. Further, the paper discusses form-factor advantages to liquid and immersion cooling and compares technologies on a common platform. Finally, the paper concludes by discussing datacenter optimization for cooling in the context of leakage power control for Xeon-Phi coprocessors.
Singulation by Plasma Etching: Integration Techniques to Enable Low Damage, High Productivity Dicing
Authors: Barnett Richard , Thomas Dave , Ansell Oliver 
Published: November 2015

Plasma dicing has rapidly gained traction as a viable alternative to conventional blade and laser techniques for wafer singulation. This has been due mostly to the significant benefits plasma dicing delivers in relation to the quality and reliability of devices singulated in this manner.
Key to the successful integration of plasma dicing, into the established hierarchy of singulation techniques, is how the ancillary parts of the process flow can be utilized or adapted to accommodate it. More importantly, is the ease at which this can happen and also, how implementation can be achieved in a cost effective manner.
Operational Lessons Learned Based on Comprehensive Temperature Measurements at Primary Circuit Components
Authors: Reese Sven H. , Seichter Johannes , Klucke Dietmar , Karabaki H. Ertugrul 
Published: November 2015

In nuclear power plants operated by E.ON, thermocouples have been installed since commissioning of the plants at fatigue relevant locations, especially at primary circuit components. Temperature measurement planes have been retro-fitted, further developed and the positions of the measurement planes have been reassigned and optimized continuously based on operational lessons learned. Comprehensive surveillance activities yield to a significant amount of information which is used to analyze the component specific health status. Additionally this information can be used to optimize plant’s behavior in the context of operational excellence.
An evaluation of temperature measurement is needed from the regulatory point of view and reported periodically in the context of long term fatigue evaluation being a significant part of the German ageing management process and break preclusion concept. Beyond that, the detailed information of temperature transients, gained by these measurements, allows the engineer to analyze thermal loadings of monitored components. Subsequently this information is used to optimize operation of the plants by minimizing fatigue relevant transients. The more detailed the temperature transient information is the more complex analytical and numerical models have to be in order to comprehensively consider relevant effects. Therefore numerical Finite-Element models of primary circuit components have been developed allowing the engineer to analyze temperature loading (e.g. stratification or plug-flow events) in detail and to draw conclusions being used to optimize the plant.
In the context of this publication examples of pressurized light water reactors will be discussed in detail showing the ability of the detailed evaluation process and the effectiveness of the evaluation procedure:
• Operational lessons learned from temperature measurement evaluation.
• Minimizing stratification events in the surge line by optimizing the point in time when main coolant pumps are turned off.
• Temperature loading of the auxiliary spray line during start-up phase.
Application of Extended Finite Element Method (XFEM) to Stress Intensity Factor Calculations
Authors: Shim Do-Jun , Uddin Mohammed , Kalyanam Sureshkumar , Brust Frederick , Young Bruce 
Published: November 2015

The extended finite element method (XFEM) is an extension of the conventional finite element method based on the concept of partition of unity. In this method, the presence of a crack is ensured by the special enriched functions in conjunction with additional degrees of freedom. This approach also removes the requirement for explicitly defining the crack front or specifying the virtual crack extension direction when evaluating the contour integral.
In this paper, stress intensity factors (SIF) for various crack types in plates and pipes were calculated using the XFEM embedded in ABAQUS. These results were compared against handbook solutions, results from conventional finite element method, and results obtained from finite element alternating method (FEAM). Based on these results, applicability of the ABAQUS XFEM to stress intensity factor calculations was investigated. Discussions are provided on the advantages and limitations of the XFEM.
On the Use of the Notch Master Curve for Apparent Fracture Toughness Predictions of Notched Ferritic Steels Operating Within the Ductile-to-Brittle Transition Zone
Authors: Cicero Sergio , Garcia Tiberio , Madrazo Virginia 
Published: November 2015

This paper presents the Notch-Master Curve as a model for the prediction of the apparent fracture toughness of ferritic steels in notched conditions and operating at temperatures corresponding to their ductile-to-brittle transition zone.
The Notch-Master Curve combines the Master Curve of the material in cracked conditions and the notch corrections provided by the Theory of Critical Distances.
In order to validate the model, the fracture resistance results obtained in fracture tests performed on notched CT and SENB specimens are presented. The results gathered here cover four ferritic steels (S275JR, S355J2, S460M and S690Q), three different notch radii (0.25 mm, 0.50 mm and 2.0 mm) and three different temperatures within the corresponding ductile-to-brittle transition zone.
The results demonstrate that the Notch Master Curve provides good predictions of the fracture resistance in notched conditions for the four materials analyzed.
Measurement of Flow-Induced Forces: A Single Flexible Tube in a Rigid Triangular-Pitch Bundle Subjected to Two-Phase Cross-Flow
Authors: Deri Enrico , Nibas Joël , Ries Olivier , Adobes André 
Published: November 2015

Flow-induced vibrations of Steam Generator tube bundles are a major concern for the operators of nuclear power plants. In order to predict damages due to such vibrations, EDF has developed the numerical tool GeViBus, which allows one to asses risk and thereafter to optimize the SG maintenance policy.
The software is based on a semi analytical model of fluid-dynamic forces and dimensionless fluid force coefficients which need to be assessed by experiment. The database of dimensionless coefficients is updated in order to cover all existing tube bundle configurations.
Within this framework, a new test rig was presented in a previous conference with the aim of assessing parallel triangular tube arrangement submitted to a two-phase cross-flow. This paper presents the result of the first phase of the associated experiments in terms of force coefficients and two-phase flow excitation spectra for both in-plane and out-of-plane vibration.
Thermal-Hydraulic Response of the Secondary Side of a PWR Steam Generator With an Internal Structure to a Main Steam Line Break
Authors: Jo Jong Chull 
Published: November 2015

This study addresses a numerical analysis of the thermal-hydraulic response of the secondary side of a steam generator (SG) model with an internal structure to a main steam line break (MSLB) at a pressurized water reactor (PWR) plant. The analysis model is comprised of the SG upper space where steam occupies and the part of the main steam pipe between the SG outlet nozzle and the broken pipe end upstream of the main steam isolation valve. To investigate the effects of the presence of the SG internal structure on the thermal-hydraulic response to the MSLB, the numerical calculation results for the analysis model having a perforated horizontal plate as the SG internal structure are compared to those obtained for a simple analysis model having no SG internal structure. Both analysis models have the same physical dimensions except for the internal structure. The initial operating conditions for both SG models are identical to those for an actual operating plant. To simplify the analyses, it is assumed that steam is constantly generated from the bottom of the SG secondary side space during the blowdown process.
As the results, it has been found that the pressure wave significantly attenuates as it passes through the perforated internal structure and as time elapses. This leads to reduction in instantaneous hydraulic load on the internal structure including tubing. However, it is seen that the presence of the internal structure does not affect the transient velocities of steam passing through the SG tube bundle during the blowdown, which are 2 to 8 times the velocities during the normal reactor operation as in the case for the empty SG. Consequently, the present findings should be considered for the design of the steam generator to ensure the reactor safety as such elevated high steam velocities can cause fluidelastic instability of tubes which results in high cycle fatigue failure of the tubes.
A Numerical Investigation of the Fluidelastic Coupling for a Cell of Flexible Tubes in a Square-in-Line Bundle Subject to Water Cross-Flow
Authors: Berland Julien , Deri Enrico , Adobes André 
Published: November 2015

The unsteady flow motions and the force distribution in a normal square tube array subject to cross-flow induced vibrations are investigated by means of large-eddy simulations. The flow configuration and the operating conditions are taken from the experiments of Gosse et al. (PVP Conference, 2001). The set-up is made of 63 (9 rows and 7 columns) straight tube bundle. The tubes are arranged in a square in line pattern, and a cell of 9 flexible tubes, located in the middle of the bundle, may translate in the drag and lift directions.
The LES of cross-flow induced vibrations of a cell of 9 flexible tubes in a normal square tube array is performed. A fully-coupled fluid-structure calculation is hence achieved using Code_Saturne, an open source CFD tool. Turbulence modeling is achieved using the large-eddy simulation framework based on the so-called classical Smagorinsky model. The tube dynamics is modeled by simple mass-spring-damper systems, and the motions of the fluid domain is accounted for by a moving mesh technique (Arbitrary-Lagrangian-Eulerian formulation).
The consistency of the calculations is demonstrated by comparing the numerical data to the experiments of Gosse et al. (PVP Conference, 2001) in terms of tube amplitude and flow-induced force spectra, for various gap velocities.
Investigation of the spectra of the flow-induced forces then shows that the tube motions ignite the emergence of flow phenomena at constant Strouhal numbers. The fluid-structure interactions are also responsible for the existence of a series of tones at rather constant frequencies, corresponding to the vibrational modes of the flexible cell.
Strain Gage and Thermocouple Measurements of Hyper Compressor Packing Cups to Study Pressure Sealing Performance
Authors: Miller Eric S. , Blanding James M. 
Published: November 2015

Low Density Polyethylene (LDPE) production involves reactors operating at up to 3,000 bar pressure or even higher. The final stage of gas compression is done with a plunger-type machine called a “Hyper Compressor”. A “packing stack” for pressure sealing consists of multiple bronze packing rings and oil lubrication injection points; which are positioned in place by numerous packing cups. The distribution of pressure drop in a new cylinder and the changes in sealing behavior over its life are critical to design, but have long been prohibitively difficult to verify experimentally.
Four cylinders were extensively instrumented; two in each of two successive test campaigns over four years’ time. Strain gages were located at the outside diameter of each packing cup to infer internal dynamic pressure across the packing stack. Included also in the high-speed data acquisition were strain gages on numerous additional components, thermocouples on packing cup faces, a pressure transducer in the low-pressure lubrication line, and existing eddy-current proximity probes on the plunger rods. Continuous monitoring was performed from the initial installation to final removal of each cylinder. Analysis of this high speed data along with long-term trends led to several conclusions regarding the design and operation of the Hyper cylinder. Testing also revealed various unusual events that can be further studied to better understand some of the unique behaviors that take place in the highly complex cylinder design of Hyper compressors.
Development of the Extremely Low Probability of Rupture (xLPR) Version 2.0 Code
Authors: Rudland D. , Harrington C. , Dingreville R. 
Published: November 2015

NRC Standard Review Plan (SRP) 3.6.3 describes Leak-Before-Break (LBB) assessment procedures that can be used to assess compliance with the 10CFR50 Appendix A, GDC-4 requirement that primary system pressure piping exhibit an extremely low probability of rupture. SRP 3.6.3 does not allow for assessment of piping systems with active degradation mechanisms, such as Primary Water Stress Corrosion Cracking (PWSCC) which is currently occurring in systems that have been granted LBB approvals.
US NRC staff, working cooperatively with the Electric Power Research Institute through a memorandum of understanding, conducted a multi-year project that focused on the development of a viable method and approach to address the effects of PWSCC in primary piping systems approved for LBB. This project, called eXtremely Low Probability of Rupture (xLPR), defined the requirements necessary for a modular-based probabilistic fracture mechanics assessment tool to directly assess compliance with the regulations.
As reported in previous technical papers, the first version of the xLPR code was developed as part of a pilot study, which leveraged existing fracture mechanics based models and software coupled to both a commercial and open source code framework to determine the framework and architecture requirements appropriate for building a modular-based code with this complexity. Using the lessons learned from the pilot study, the production version of this code, designated as Version 2.0, focuses on those primary piping systems previously approved for LBB. In this version, the appropriate fracture mechanics-based models are employed to model the physical cracking behavior and a variety of computational options are provided to characterize, categorize and propagate problem uncertainties.
This paper examines the xLPR Version 2.0 model by presenting a brief overview of the xLPR scope, the code structure, computational framework and fracture mechanics-based models. As a demonstration of the xLPR Version 2.0 capabilities, an example is presented that focuses on PWSCC in large-bore piping systems. This example exercises some functionalities of the xLPR code to demonstrate its application to assess compliance with 10CFR50 Appendix A, GDC-4. This paper concludes with a brief discussion on the path forward and plans for the control and maintenance of the xLPR code.
Computation of a Loosely Supported Tube Under Cross-Flow by a Hybrid Time-Frequency Method
Authors: Piteau Philippe , Borsoi Laurent , Delaune Xavier , Politopoulos Ioannis , Antunes Jose 
Published: November 2015

Flow-induced vibrations of heat-exchanger tubes are particularly analyzed in the nuclear industry for safety reasons. Adequate designs, such as anti-vibration bars in PWR steam generators, prevent any excessive vibrations provided the tubes are well supported. Nevertheless degraded situations, where the tube/support gaps would widen, must also be considered. In such a case, the tubes become loosely supported and may exhibit vibro-impacting responses due to both turbulence and fluid-elastic coupling forces induced by the cross-flow.
This paper deals with the predictive analysis of such a situation, based on a time-frequency hybrid method, given the necessity of taking into account both the strong impact nonlinearity due to the gap and the linearized fluid-elastic forces defined in the frequency domain. It comprises four parts.
1) The experimental campaign carried out at CEA Saclay on this issue, with a rigid square bundle surrounding a flexible cantilever tube under water cross-flow, is briefly recalled.
2) The hybrid time-frequency method is presented. The technique consists in an iterative solving, going back and forth from the frequency domain to the time domain, until convergence. Focus is made on the key points that are the algorithm convergence, and the non-causality of fluid-elastic forces stemming from the extrapolation of the frequency-limited experimental data.
3) The experimental and computational results are compared for a large range of flow velocities and three values of gaps, with a satisfying overall agreement. The comparison includes also previous results obtained from a simplified method based on the concept of “instantaneous” frequency.
4) Finally two a priori surprising behaviors are noted in the energy balances that have been computed: the sometimes dissipative aspect of turbulence forces, and the “mirror effect” between the work of turbulence and fluid-elastic forces.
Prediction of Dynamic Break-Opening Area Under Beyond Design Basis Seismic Loading
Authors: Uddin M. , Kurth E. , Brust F. W. , Wilkowski G. M. , Betervide A. A. , Mazzantini O. , Fernandez R. A. 
Published: November 2015

The thermal-hydraulics computer code, RELAP (Reactor Excursion and Leak Analysis Program) is used to analyze loss of coolant accidents (LOCAs) and system transients in PWRs and BWRs. However, RELAP requires the knowledge of break-opening area versus time history for Double-Ended Guillotine Break (DEGB) of a pipe fracture event as an input to calculate pressure drops at critical locations in the primary pipe loop. Previously authors conducted a detailed dynamic FE analyses to determine the condition for DEGB that provided moment versus rotation of the cracked-pipe and time histories for DEGB under beyond design basis seismic loading.
In this paper, crack-opening area was calculated using the moment-rotation-time history obtained from dynamic FE analyses. In the LBB.ENG2 J-estimation scheme for circumferentially cracked pipe, the rotation at the cracked-pipe cross-sectional location (rotation due to the crack) is uniquely related to the total crack length and crack-opening displacement at the center of the crack. However, the relationship is only valid when the moment versus rotation from the FE analyses corresponds to the ductile tearing curve from the LBB.ENG2 ductile fracture analysis. During any unloading (and reloading) parts of the applied seismic history, the rotation can drop down from the upper-envelope for the tearing resistance of the cracked pipe in an elastic unloading manner from the seismic/cyclic unloading. During this part of the seismic time-history, the crack length remains constant but the center-crack-opening displacement decreases, i.e., there is crack closure with a constant crack length which needs to be included in predicting crack-opening area. Based on a number of past cyclic pipe fracture tests with large amounts of ductile tearing, a procedure was developed to predict the crack-opening area that included crack closure during cyclic loading of the seismic event. The resulting opening-area versus time history then becomes the input to the RELAP analysis for determination of emergency core cooling/safety processes.
Application of XFEM to Model Crack Initiation and Propagation During a PTS Event
Authors: Nicak Tomas , Mutz Alexander , Keim Elisabeth , Meier Gottfried 
Published: November 2015

The integrity of a reactor pressure vessel (RPV) has to be ensured throughout its entire life in accordance with the applicable regulations. Typically an assessment of the RPV against brittle failure needs to be conducted by taking into account all possible loading cases. One of the most severe loading cases, which can potentially occur during the operating time, is the loss-of-coolant accident (LOCA), where cold water is injected into the RPV at operating conditions. High pressure in combination with a thermal shock of the ferritic pressure vessel wall caused by the injection of cold water leads to severe loading conditions at the beltline area known as Pressurized Thermal Shock (PTS).
Usually the assessment against brittle failure is based on a deterministic fracture mechanics analysis, in which common parameters like the J-integral or stress intensity factor are employed to calculate the load path during the PTS event for an assumed (postulated) flaw. Subsequently the results of the fracture mechanics analysis are compared with material properties obtained from the irradiation surveillance program of the RPV to demonstrate the exclusion of brittle fracture initiation.
In this paper an alternative novel method for the calculation of the crack initiation and possible crack propagation by means of the eXtended Finite Element Method (XFEM) will be introduced and compared with results of the standard PTS analysis.