bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface to Through-Wall Crack Transition Model for Axial Cracks in Pipes
Authors: Shim Do-Jun , Rudland David , Park Jeong-Soon 
Published: November 2014

Recent studies have shown that a subcritical surface crack, due to PWSCC, can transition to a through-wall crack with significant differences between the inner diameter and outer diameter crack lengths. This behavior has been observed for both circumferential and axial cracks. Recently, a surface to through-wall crack transition model has been developed for circumferential cracks using existing K and COD solutions for non-idealized circumferential through-wall cracks.
In this paper, a similar crack transition model was developed for axial cracks. As a first step, a study was conducted to define the appropriate crack front shape for non-idealized axial through-wall cracks. Then, elastic finite element analyses were carried out to develop K and COD solutions using these crack front shapes. The newly developed solutions were utilized for the crack transition model. The present crack transition model includes a criterion for transitioning the final surface crack to the initial non-idealized TWC. This criterion determines when the transition should occur (based on surface crack depth) and determines the two crack lengths (at ID and OD surfaces) of the initial non-idealized TWC. Furthermore non-idealized TWC growth can be conducted using the proposed model. Example results (crack length and COD) obtained from the proposed model were compared to those obtained from the natural crack growth simulations. Results presented in this paper demonstrated the applicability of the proposed model for simulating axial crack transition.
Experimental and Numerical Analysis for Fluid-Structure Interaction for an Enclosed Hexagonal Assembly
Authors: Sargentini Lucia , Cariteau Benjamin , Angelucci Morena 
Published: November 2014

This paper is related to fluid-structure interaction analysis of sodium cooled fast reactors core (Na-FBR). Sudden liquid evacuation between assemblies could lead to overall core movements (flowering and compaction) causing variations of core reactivity. The comprehension of the structure behavior during the evacuation could improve the knowledge about some SCRAMs for negative reactivity occurred in PHÉNIX reactor and could contribute on the study of the dynamic behavior of a FBR core. An experimental facility (PISE-2c) is designed composed by a Poly-methyl methacrylate hexagonal rods (2D-plan similitude with PHÉNIX assembly) with a very thin gap between assemblies. Another experimental device (PISE-1a) is designed and composed by a single hexagonal rod for testing the dynamic characteristics. Different experiments are envisaged: free vibrations and oscillations during water injection.
A phenomenological analysis is reported showing the flow behavior in the gap and the structure response. Also computational simulations are presented in this paper. An efficient numerical method is used to solve Navier-Stokes equations coupled with structure dynamic equation. The numerical method is verified by the comparison of analytic models and experiments.
Discussion of Fatigue Data for Austenitic Stainless Steels
Authors: Wilhelm Paul , Steinmann Paul , Rudolph Jürgen 
Published: November 2014

The first results of a detailed fatigue model for austenitic stainless steels in general and for the grades 1.4541 and 1.4550 are presented to describe the effect of the light water reactor (LWR) coolant environments on the fatigue life. The statistical evaluations are based on strain (and load) controlled test series from different institutions. The compiled fatigue data include not only results from America (Keller (1971), Conway (1975), Hale (1977), and Argonne National Laboratory (ANL)(1999–2005)), but also from Europe (Solin (2006), Le Duff (2008–2010), De Baglion (2011, 2012), Huin (2013),…) and Japan (Kanasaki (1997)). The fatigue life is defined as the number of cycles necessary for tensile stress to drop 25 percent from its peak value. Fatigue lives defined by other failure criteria are normalized to the load reduction of 25 percent, before the statistical analysis is performed. The fatigue data are expressed in terms of the Langer equation and the parameter “material variability and data scatter” is quantified.
Additionally, fatigue data in air of roughened specimens are compiled and discussed. A reduction factor of 2.5 on number of cycles is derived to cover the maximum allowed surface roughness.
Based on the derived best-fit curves, design-curves in air and, in a second step, environmentally assisted fatigue (EAF) curves for LWR environments, which consider temperature, strain rate, dissolved oxygen content, and hold-time effects, will be incorporated in the detailed fatigue model in the future.
Effect of Warm Pre-Stress on Highly Irradiated Pressure Vessel Steel
Authors: Moinereau Dominique , Landron Caroline , Ait Bachir Malik , Garbay Eric 
Published: November 2014

The effect of warm pre-stress (WPS) is well known on cleavage fracture resistance of ferritic steels and has been confirmed on numerous tests on non irradiated materials. Theoretical knowledge let expect that this effect occurs by the same way on irradiated material but has to be demonstrated with experiments in such conditions. An experimental program has been conducted by EDF in Chinon hot cell laboratory on two RPV steels irradiated up to a fluence of 6,5*1019 n/cm2.
The ½ TCT specimens (CT12.5) used in this programme have been irradiated in the capsules of the EDF RPV surveillance program of two PWR reactors. Different types of WPS loading path have been applied to cover typical postulated accidental transients. The results confirmed the effect on WPS on the cleavage fracture resistance of the irradiated materials. No fracture occurred during the cooling phase of the loading path and the fracture toughness values are higher than that measured with conventional isothermal tests.
The analyses of the experiments have been conducted based on use of simplified engineering models and more refined fracture models based on local approach to cleavage fracture. These analyses are in agreement with the experimental results.
Improved Accuracy on Efficiency of PK Hypercompressor Valves
Authors: Maggi Carmelo , Wojnar Jan , Bagagli Riccardo , Tognarelli Leonardo 
Published: November 2014

In recent years, also because of the overall contraction of the market, all compressor manufacturers are differentiating their products by offering solutions that optimize/minimize costs while maintaining the same robustness and reliability.
To achieve this goal, the main guidelines are “Power Density” and “Efficiency”.
On hyper compressors for LDPE plants, the absorbed power of the valves has a key role in overall efficiency and, thanks to dedicated development programs aimed to design more and more efficient valves, represents one of the disciplines where it is still possible to improve the performance.
The absorbed power of this type of valves is strictly correlated to their behavior which is challenging to predict because it depends on many factors. The expected macroscopic gas parameters, such as pressure, temperature and gas composition often are not sufficient to properly evaluate valve behavior in the field.
In fact valve operation is highly dependent on local phenomena such as localized pressure losses and presence of vortexes which are in turn influenced by the geometry of the valve and by its behavior.
To better understand all these phenomena it is needed to characterize these valves through experimental tests aimed at defining, with a good precision and accuracy, the valve dimensionless parameters Cd (drag coefficient) and Ks (flow coefficient) as a function of the geometry of the valve itself. If the coefficients Cd and Ks are not accurate, the expected behavior of the valve and, as a consequence the valve losses, may be completely different from the evidence of the field and could not properly explain some unexpected power consumption.
Therefore, through a dedicated characterization of the valves design, it is possible to improve the predictability of the valve, also in terms of power consumption, that contributes to a better evaluation of the total absorbed power by the compressor, which allows designers to reduce their margins of uncertainty.
Fatigue Crack Growth Rates for Nickel Base Alloys in Air
Authors: Nomura Yuichiro , Yamamoto Kenji , Hojo Kiminobu 
Published: November 2014

When defects are detected by in-service inspections of the nuclear power plants in Japan, allowable flaws are evaluated according to the Rules on Fitness-for-Service for Nuclear Power Plants of Japan Society of Mechanical Engineers (JSME maintenance rules). The fatigue crack growth analysis is an important part of the flaw acceptance evaluation. However FCGR curves for nickel base alloys in air are not provided in the current JSME maintenance rules.
This paper describes the evaluation of the fatigue tests in air of nickel base alloys and formulation of the FCGR curves for the JSME rules on Fitness-for-Service. From the test results, the temperature and stress ratio are not dominant factors. However, as based on the form of the FCGR curve of NUREG/CR-6721, the proposed curves are shown to be functions of these parameters. Threshold of stress intensity factor is introduced in the curves by taking into account crack closure.
Advanced Analyses of Let-Down Valves to Improve LDPE Plant Performance
Authors: Grassini Ubaldo 
Published: November 2014

High pressure plants for LDPE production are characterized by machinery and equipment undergoing severe fatigue, pulsation, vibration and erosion problems.
The collection of data relevant to the performance of compressors and plants has to be properly carried out to help the maintenance engineering team to identify the possible ways of improvement.
The use of advanced laboratory analyses gives a valid contribution to the investigations and the determination of the root causes of the existing problems. While on the compressors the wear and fatigue are generally the reasons for a shut-down, on the plant there are other critical components like the let-down valves, needing careful consideration.
Their periodical actuation implies fatigue and erosion appreciably influencing the MTBF and the availability of the plant.
These valves are real critical components on tubular reactor plants. The analyses carried out at different times have allowed to change material so improving the resistance to wear and the mechanical properties resulting in a higher reliability.
The Impact of Emergency Release in LNG Transfer
Authors: van Bokhorst Evert , Webber Tony , van der Putte Jesper , Smeulers Jan , Remans David 
Published: November 2014

This paper describes the results of experimental work and simulations of pressure surges resulting from fast closing valves and activation of an emergency release coupling (ERC) in ship-to-ship LNG transfer. The first part presents the results of an ambient water flow test with a fast closing 4-inch full bore valve in combination with a 4-inch flexible multi-composite hose. High amplitude pressure surges up to 4 times the working pressure occur upstream of the valve. Pressure surge amplitudes strongly depend on valve closing time and flow rate. The propagation speed in the upstream hose is lowered considerably due to the hose flexibility. Furthermore the temporarily deformation of the hose results in loss of energy and acoustic damping of the pressure surge amplitudes.
The measurement results are compared to the results of modeling. Acoustic damping and propagation speed of sound show a non-linear behavior of the hose, due to a varying internal pressure, which is not captured in the present modeling techniques.
The second part of the paper describes the results of a full scale flow test on an 8-inch ERC (KLAW make) for LNG ship-to-ship transfer (Figure 1). The ERC in the test is located downstream of an 8-inch 15-meter long multi-composite flexible hose. The test is intended to investigate operational and mechanical integrity, spill rate and the impact of pressure transients and shock loads on the ERC including upstream hose and downstream piping.
Upon hydraulic activation the ERC separates in two parts, each provided with a fast closing butterfly valve. The complete operation takes about 0.2 s and the actual valve closure duration is about 0.02 s resulting in a negligible spill of less than 0.002 m3. Pressure transients from 34 to 100 bar, over 10 times the operating pressure, occur at the maximum flow rate of 1000 m3/hr, resulting in shock loads and high acceleration levels. The mechanical integrity remains intact even after four successive releases at the maximum flow rate of 1000 m3/hr. The results contribute to the certification of the ERC by Lloyds B.V.
Further development in modeling is necessary to obtain a validated model for the calculation of pressure surges due to emergency shutdown in a LNG transfer.
LBB Nozzle Transition Parameter Variation and Plasticity Influence
Authors: Baas Peter , Blom Frederic 
Published: November 2014

In the framework of the R6 development programme on leak before break NRG investigated a circumferential through wall crack in a pipe with nozzle. A range of crack angles (3–180°), radius over wall thickness ratios (Ri/t = 5, 10, 20, 50 and 100) and nozzle divergence angles (0, 5, 10, 20, 30 and 40°) have been investigated in order to investigate parameter sensitivity. The stress intensity factor (KI) and the Crack Opening Area (COA) are compared for the nozzle and pipe models. The nozzle investigation is performed using a longitudinal force (100 MPa).
It can be concluded that with larger nozzle divergence angles, the resulting maximum KI nozzle factors are higher. The larger nozzle divergence angles have a suppressive effect on the crack opening resulting in a lowered COA nozzle factor.
The influence of plasticity has been investigated by a number of analyses including plastic behaviour. The geometry variations are five Ri/t ratios (5, 10, 20, 50 and 100) and eight different crack angles (3, 10, 30, 50, 75, 100, 140 and 180°). A 30° nozzle angle was selected for plastic analyses. The plasticity investigation is performed using longitudinal force (100 MPa).
In general the results for KI are higher with the inclusion of plasticity. However, since the inclusion of plasticity has a stress relieving effect on the pipe/nozzle transition, the resulting maximum KI nozzle factor is lowered. The COA results for the individual analyses are overall higher due to the inclusion of plasticity. The COA nozzle factor is lowered, because the relative influence of plasticity is lower on the stiffer nozzle.
Implementation of the EPRI Guidelines to Fatigue Analyses of Primary Circuit Components: Challenges and Recommendations in the Framework of Practical Application
Authors: Reese Sven H. , Seichter Johannes , Klucke Dietmar , Karabaki H. Ertugrul , Mayinger Wolfgang 
Published: November 2014

The influence of LWR coolant environment to the lifetime of materials has been discussed recent years. Nowadays the environmentally assisted fatigue (EAF) is under consideration in Codes and Standards like ASME by formula calculation and in the German KTA Rules (e.g. KTA No. 3201.2 and 3201.4) in addition by means of so called attention thresholds.
Basic calculation procedures in terms of quantifying the influence of LWR coolant environment by the so called Fen-factor were proposed in NUREG CR-6909 in 2007. Since this report the set of formulas have been adapted several times (e.g. in ANL-LWRS47-2011) and further changes in set of formulas are likely to occur. Subsequently a revision of the NUREG CR-6909 report is taking place incorporating recent changes.
Within the EPRI 2012 Technical Report “Guidelines for Addressing Environmental Effects in Fatigue Usage Calculations” some practical recommendations for the application of the EAF to real components are stated. In this report EPRI presented the calculation of sample problems in combination with sample transients carried out by the participants and verifying the applicability of the proposed approaches. However, the EPRI guideline provides a set of tools taking environmentally assisted fatigue into account. This guidance figures out to be quite helpful on one hand, but incorporates some challenges in terms of practical application on the other hand. Additionally, the EPRI Report gives no clear advice which specific combination of calculation methods to apply finally.
Within this publication the procedures proposed in the EPRI guideline will be applied to existing numerical approaches being published. Challenges when applying the methods defined in the EPRI guideline will be identified and solutions will be given. Additionally, recommendations will be stated based on the proposed procedures in terms of practical application especially in context of calculations for fatigue relevant primary circuit components.
Experimental Determination of the Static Equivalent Pressures of Detonative Decompositions of Acetylene in Long Pipes and Chapman-Jouguet Pressure Ratio
Authors: Schildberg Hans-Peter 
Published: November 2014

Gaseous acetylene (C2H2), which is used in industry in large quantities, is well known for being prone to detonative decomposition. Existing guidelines provide advice for a safe handling but are still deficient with regard to quantifying the static equivalent pressures experienced by the wall of a pipe when exposed to an internal detonative decomposition reaction. By applying the pipe wall deformation method we determined the static equivalent pressures occurring in long pipes. Once the static equivalent pressure is known, the well-established pressure vessel design guidelines, which can cope with static loads, can be applied for detonation pressure proof pipe design in all cases where the detonation speed is not close to the propagation speed of the flexural waves in the pipe.
The tests revealed further important new details characterizing the detonative decomposition of C2H2: 1) The static equivalent pressure at the location of the occurrence of the deflagration to detonation transition (DDT) turned out to decrease relatively with increasing initial pressure. 2) When exceeding an initial pressure of approximately 12 bar abs there was no longer a stage of instable detonation after the occurrence of the deflagration to detonation transition, but the reaction front immediately propagated as a stable detonation. 3) It was found that the Chapman-Jouguet theory, which provides reasonably precise predictions for the propagation speed of the stable detonation and the Chapman-Jouguet pressure ratio in the case of common stoichiometric combustible/oxidant mixtures, seems to fail in the case of the decomposition of C2H2. A possible reason for this could be the fact that the decomposition reaction, in contrast to all other combustion reactions, generates both gaseous and solid reaction products. 4) By combining the results of recent work on detonations in ethylene/O2/N2-mixtures published in PVP2013-97677 and the present tests, a good estimate for the Chapman-Jouguet pressure ratio of the detonative decomposition reaction of C2H2 could be derived.
European Contributions to Environmental Fatigue Issues Experimental Research in France, Germany and Finland
Authors: Métais Thomas , Karabaki Ertugrul , De Baglion Laurent , Solin Jussi , Le Roux Jean-Christophe , Reese Sven , Courtin Stéphan 
Published: November 2014

Environmentally assisted fatigue (EAF) is at the centre of numerous discussions and conferences on fatigue around the world. The methodology proposed in NUREG/CR-6909 [1] is being applied in the USA for new builds and for license renewal per the RG 1.207 [2], but there is still room for a better understanding of all the effects involved and for fine-tuning of the methodology. A roadmap by EPRI lists areas where testing is recommended [3].
In Europe, research is going on and the accumulated results show that NUREG/CR-6909 is very conservative [4]–[10]. Applicability of the proposed design curve and the Fen factors were questioned in previous papers and alternative approaches have been developed [11]–[14].
This paper summarizes different experimental, analytical and practical approaches taken by four main players in the European nuclear industry and compares results with the NUREG/CR-6909 methodology. This joint discussion demonstrates that, although the approaches have been different, a common conclusion is reached: the NUREG/CR-6909 methodology can be improved.
License Renewal and Subsequent License Renewal in the U.S.
Authors: Young Garry G. 
Published: November 2014

As of February 2014, the NRC has renewed the operating licenses for 73 nuclear units, allowing for up to 60 years of safe operation. In addition, the NRC has license renewal applications under review for 18 units and 9 additional units have announced plans to submit applications over the next few years [1]. This brings the total of renewed licenses and plans for renewal to 100% of the operating nuclear units in the U.S.
By the end of 2014, there will be 38 nuclear plants that will have operated for more than 40 years and will be eligible to seek a subsequent license renewal (or almost 40% of the nuclear units expected to be operating at the end of 2014). In 2013, nuclear plant owners of 5 units shutdown operation or announced plans to shutdown by the end of 2014. However, most of the remaining operating plant owners are keeping the option open for long term operation beyond 60 years. NRC and the U.S. nuclear industry have made significant progress in preparing the way for subsequent license renewal applications. This paper presents the status of the U.S. license renewal process and issues being addressed for possible applications for subsequent renewals for up to 80 years of operation.
Study on Power Generation Using Unstable Energy by In-Flow Fluidelastic Vibration
Authors: Sumitani Takuya , Hagiwara Shinichiro , Nakamura Tomomichi 
Published: November 2014

In-flow instability of tube arrays is one of recent major issues to be examined in the heat exchanger design since the event at a nuclear power plant in California [1]. In our previous tests [2], the effect of the pitch-diameter ratio in triangular arrays is reported. This is one of the present major issues in the nuclear industry.
On the other hand, there are some trials [3] to produce the electric power by the phenomenon of the flow-induced vibration. They are mainly using the vortex shedding, but in this report the power generation by the unstable vibration is investigated. It is spotlighted the combination between the unstable vibration and the power generation whether the limit cycle exists or not. This report introduces the result on the existence of the limit cycle.
Many engineers have attempted to produce electric power using semi-conductor devices, but they could not obtain enough power. Then, the device using the electro-magnetic system is used here. The in-flow instability has a small effect on the fluid flow compared with the usual fluidelastic vibration in the transverse direction, because the in-flow movement does not disturb the flow path compared to the transverse fluidelastic vibration.
The coil-magnet system is set on the top of the flexible cylinder cantilevered from the bottom. A three by three array of cylinders in a triangular pattern is set in a small wind tunnel. When the flow velocity increases, the cylinder array becomes unstable in the in-flow direction as similarly to the transverse direction, and it produces the electricity in the coil. However, as the power generation means energy dissipation, resulting in increase of the system damping, the effect on the instability is examined.
At the end of this report, an analytical solution is introduced to explain the measured results. It is successfully completed to show the existence of the limit cycle.