bluuebunny/crossref_metadata_2025 huggingface dataset:
Irradiation Induced Changes in Mechanical and Microstructural Properties of the High Flux Reactor Vessel: Update of the Results From 2014 and 2015 Surveillance Test Campaigns
Authors: Kolluri M. , de Haan-de Wilde F. H. E. , Nolles H. S. , de Jong A. J. M. , van den Berg F. A.
Published: October 2017

The reactor vessel of the High Flux Reactor (HFR) in Petten has been fabricated from Al 5154 - O alloy grade with a maximum Mg content of 3.5 wt. %. The vessel experiences large amount of neutron fluences (notably at hot spot), of the order of 1027 n/m2, during its operational life. Substantial damage to the material’s microstructure and mechanical properties can occur at these high fluence conditions. To this end, a dedicated surveillance program: SURP (SURveillance Program) is executed to understand, predict and measure the influence of neutron radiation damage on the mechanical properties of the vessel material. In the SURP program, test specimens fabricated from representative HFR vessel material are continuously irradiated in two specially designed experimental rigs. A number of surveillance specimens are periodically extracted and tested to evaluate the changes in fracture toughness properties of the vessel as a function neutron fluence. The surveillance testing results of test campaigns performed until 2009 were already published by N. V. Luzginova et. al. [1]. The current paper presents results from the two recent surveillance campaigns performed in 2014 and 2015. The fracture toughness and tensile testing results are reported. Changes in mechanical properties of Al 5154-O alloy with an increase in neutron fluence are discussed in correlation with the irradiation damage microstructure observed in TEM and the fracture morphology observed in SEM. The HFR surveillance testing results are compared to the historically published results on irradiated aluminum alloys and conclusions about the evolution of embrittlement trends in relation with irradiation induced damage mechanisms in HFR vessel are drawn at the end.
Crack Extensions in Compact Tension Specimens of Hydrided Irradiated Zr-2.5Nb Materials Using Cohesive Zone Model
Authors: Wu Shengjia , Sung Shin-Jang , Pan Jwo , Lam Poh-Sang , Scarth Douglas A.
Published: October 2017

The crack extension in a compact tension specimen of hydrided irradiated Zr-2.5Nb material is investigated by a two-dimensional plane stress finite element analysis. The stress-strain relation of the Zr-2.5Nb material for the finite element analysis is obtained from fitting the experimental tensile stress-strain curve of the irradiated Zr-2.5Nb material without hydrides by a three-dimensional finite element analysis. The calibration of the cohesive zone model with a trapezoidal traction-separation law is based on fitting the load-displacement-crack extension experimental data of a compact tension specimen of hydrided irradiated Zr-2.5Nb material. The general trends of the load-displacement, crack extension-displacement, and load-crack extension curves obtained from the finite element analysis based on the calibrated cohesive zone model are in agreement with the experimental data.
Efficient Fitting Procedure for Corrosion Rate Distribution in View of Reliability Analysis
Authors: Sakai Shinsuke , Kaida Takuyo
Published: October 2017

The Gumbel model is widely used for the theoretical distribution of the corrosion rate. In applying the reliability analysis, the parameters of the distribution must be estimated from the inspected data. The estimation of parameters is done by using some fitting procedures. However, it is not necessarily clear which fitting procedure is suitable in view of reliability analysis. Especially, the fitting accuracy around tail region is possibly influence the reliability analysis. In this study, the efficient fitting procedure for the corrosion rate distribution in view of reliability analysis was investigated using Monte Carlo Simulation together with reliability analysis.
Gaseous Deflagration in Piping: Part 2 — Proposed Methods and Code Acceptance Criteria
Authors: Minichiello John C. , Ligon Thomas C. , Gross David J.
Published: October 2017

This paper proposes Piping Code rules to address the effects of hydrogen deflagrations inside piping. Previous work proposed a set of criteria for piping subject to detonation loading [PVP2012-78519, PVP2012-78525]. This paper provides criteria to evaluate the effect of deflagrations, which typically have a slower rise time and lower energy, inside the piping. These deflagration criteria, coupled with the previously cited detonation criteria, are being used at the Hanford Tank Waste Treatment and Immobilization Plant to evaluate piping systems subject to hydrogen accumulation.

The previous papers did not investigate or propose criteria for deflagrations, as these were known to have lower pressures and slower pressure rise times, but are still of some significance for piping design. Recent work has shown that there exists a scenario in which the deflagration loading may be very significant: deflagrations in small gas pockets surrounded by large waste slugs. Depending on the assumptions used to develop the loading, the unbalanced forces on piping segments in a long piping system can become high during a deflagration event. Thus, for the set of criteria chosen for deflagration, the deflagration event may become the limiting event, especially if it is the more frequent event. The criteria proposed need to recognize this scenario and guide the user to possible solutions. This paper presents the original methodology for evaluating these “slug” events, briefly discusses the recent testing and theory being pursued to reduce the effect of the loading [PVP2015-45970, PVP2016-63260, PVP2016-63262], and then proposes criteria for evaluating deflagration induced stresses and loads.
Correlation of Fractographic Examinations With Numerical Calculations Regarding Dynamic Fracture
Authors: Tlatlik Johannes , Reichert Thomas
Published: October 2017

In practice, cleavage fracture assessment for ferritic reactor pressure vessel steels is standardized by the quasi-static Master Curve concept (ASTM E 1921) on a macroscopic level. This standard is technically valid for dynamic loading conditions, yet recent work has shown that experimentally determined fracture toughness values under rapid loading lead to discrepancies regarding the shape of the Master Curve. It is assumed that one reason for these discrepancies is the profound adiabatic heating. The investigation of this, as well as related phenomena, is subject of this work.

Regarding this work, these experimental discrepancies are specified by a wide range of experiments. Moreover, fractographic investigations were performed on this experimental database to determine the exact origin of cleavage fracture, and compared to data from quasi-static experiments. In a second step numerical simulations were conducted for various crack-tip loading rates and testing temperatures, whereupon the temperature development in the cleavage fracture relevant region was quantified. This also allowed a determination of the individual initiation temperatures, which were analyzed and discussed whilst also taking into account the increase in local strain rate at the origin of cleavage fracture.

Finally, fractographic examinations also revealed the relevance of local crack arrest (crack stop) which was quantified, and also linked to the mentioned experimental discrepancies regarding the Master Curve concept.
Vibration Testing of Compression Joints
Authors: Hirschberg Paul , Sindelar Mark , Kassar Maher , Haupt Ron
Published: October 2017

The use of compression joints in ASME Nuclear Class 2 and 3 small diameter piping systems has become increasingly popular because their installation does not require welding, and therefore saves time, money, and radiation dose. An important question is whether these types of joints can be a practical alternative to socket welds in piping systems subject to vibration. There have been numerous operating experience events where socket welds have developed cracks due to high cycle fatigue. On the other hand, parts of compression joints plastically deform the pipe to grip and create their sealing connection; the application of a high cycle vibration load to an already plastically strained pipe might lead to premature failure. It is desired to know whether at least one type of compression joint would perform better or worse than socket welds in such an environment.

In this paper, a testing methodology is described, in which one supplier’s coupling joint design was tested for vibration loading in tubing assemblies of varying sizes. The intended application for these joints is in an Electro-Hydraulic Control system at a northeastern Boiling Water Reactor plant. Industry experience reports have identified past vibration problems in this system at other plants. A test setup was devised, in which multiple specimens could be tested simultaneously by adjusting specimen natural frequency, shake table speed, and input acceleration. Fatigue Strength Reduction Factors were derived, allowing the resistance to fatigue failure to be quantified. Both compression joints and socket welds were tested using the same procedures, in order that the fatigue damage resistance could be compared between the two types of joints.
The Significance of Coke Resistance in Coke Drum Failures
Authors: Samman Mahmod , Doerksen Brian
Published: October 2017

Shell bulging and cracking in coke drums have been documented for decades. Most of the literature on the subject attributes these failures to severe spatial and temporal thermal gradients that develop during the quench part of the operating cycle. While transient thermal gradients can be severe and can cause excessive stresses, they alone cannot explain all types of observed shell damage in drums. In this paper, the authors present and discuss observations that suggest that when a cooling shell contracts during quenching, the interaction of the cooling shell with the in-situ coke in the drum can induce substantial hoop and axial stresses in its wall. The manner and degree to which this resistance plays a role in causing damage appears to depend on the type of coke produced and the way drums are operated.
Effect of Material Anisotropy on the Structural Integrity of Composite Bolted Flanged Joints
Authors: K. Vafadar Ali , Bouzid Abdel-Hakim , Ngô Anh Dung
Published: October 2017

The leakage tightness and structural integrity are the two most important criteria that are considered in the design of bolted flanged joints; composite flanges are no exception. Although the current practice is to use existing design methods for metallic flanges in the design of FRP flanges, their ability to appropriately address the anisotropic behavior of composite flanges is of major concern. Several failures of such flanges has fostered new alternative to design composite flanges.

This paper assess the reliability of numerical modeling of FRP bolted joints based on isotropy and compares the results with anisotropic based numerical Finite Element (FE) modeling. Experimental data are included to support the findings and emphasis the importance of including anisotropy to predict stresses and strains in composite flanges.
Optimizing Maintenance Strategy of a Reactor Pressure Vessel Using 3D-CFD and FEM Based Probabilistic Pressurized Thermal Shock Analysis
Authors: Ruan Xiaoyong , Nakasuji Toshiki , Morishita Kazunori
Published: October 2017

The structural integrity of a reactor pressure vessel (RPV) is important for the safety of a nuclear power plant. When the emergency core cooling system (ECCS) is operated and the coolant water is injected into the RPV due to a loss-of-coolant accident (LOCA), the pressurized thermal shock (PTS) loading takes place. With the neutron irradiation, PTS loading may lead a RPV to fracture. Therefore, it is necessary to evaluate the performance of RPV during PTS loading to keep the reactor safety.

In the present study, optimization of RPV maintenance is considered, where two different attempts are made to investigate the RPV integrity during PTS loading by employing the deterministic and probabilistic methodologies. For the deterministic integrity evaluation, 3D-CFD and finite element method (FEM) simulations are performed, and stress intensity factors (SIFs) are obtained as a function of crack position inside the RPV. As to the probabilistic integrity evaluation, on the other hand, a more accurate spatial distribution of SIF on the RPV is calculated. By comparing the distribution thus obtained with the fracture toughness included as a part of the master curve, the dependence of fracture probabilities on the position inside the RPV is obtained. Using the spatial distribution of fracture probabilities in RPV, the priority of the inspection and maintenance is finally discussed.
Current Status of the Characterization of RPV Materials Harvested From the Decommissioned Zion Unit 1 Nuclear Power Plant
Authors: Rosseel Thomas M. , Sokolov Mikhail A. , Chen Xiang , Nanstad Randy K.
Published: October 2017

The decommissioning of Units 1 and 2 of the Zion Nuclear Power Station in Zion, Illinois, after ∼ 15 effective full-power years of service presents a unique opportunity to characterize the degradation of in-service reactor pressure vessel (RPV) materials and to assess currently available models for predicting radiation embrittlement of RPV steels [1–3]. Moreover, through-wall thickness attenuation and property distributions are being obtained and the results to be compared with surveillance specimen test data. It is anticipated that these efforts will provide a better understanding of materials degradation associated with extending the lifetime of existing nuclear power plants (NPPs) beyond 60 years of service and subsequent license renewal. In support of extended service and current operations of the US nuclear reactor fleet, the Oak Ridge National Laboratory (ORNL), through the U.S. Department of Energy, Light Water Reactor Sustainability (LWRS) Program, coordinated procurement of materials, components, and other items of interest from the decommissioned Zion NPPs. In this report, harvesting, cutting sample blocks, machining test specimens, test plans, and the current status of materials characterization of the RPV from the decommissioned Zion NPP Unit 1 will be discussed. The primary foci are the circumferential, Linde 80 flux, wire heat 72105 (WF-70) beltline weld and the A533B base metal from the intermediate shell harvested from a region of peak fluence (0.7 × 1019 n/cm2, E > 1.0 MeV) on the internal surface of the Zion Unit 1 vessel. Following the determination of the through-thickness chemical composition, Charpy impact, fracture toughness, tensile, and hardness testing are being performed to characterize the through-thickness mechanical properties of base metal and beltline-weld materials. In addition to mechanical properties, microstructural characterizations are being performed using various microstructural techniques, including Atom Probe Tomography, Small Angle Neutron Scattering, and Positron Annihilation Spectroscopy.
Finite Element Analysis Based Stress Intensification Factor Calculation and Comparison With Various Approaches for Stress Intensification Factor Calculation
Authors: Kulkarni Mahesh , Dewangan Vivek
Published: October 2017

Piping caters a major role in the process industries wherein stress intensification factor (SIF) express the Piping flexibility of the system. A typical Piping system consists of combination of pipes and various fittings with intersection geometries namely bend, tee, reducer, etc. A SIF is a multiplier on nominal bending stress so that the effect of geometry and welding can be considered in a flexibility analysis. An attempt has been made to compare the SIF values among ASME Piping B31.3, Welded Research Council (WRC) Bulletin 329, Paulin Research Group (PRG) empirical data and shell-based finite element analysis (FEA) for various tee sections based on in-plane and out-plane bending moments through this paper. The bending moment which causes tee to open/close in the plane formed by two limbs of tee is called in-plane bending moment. The bending moment which causes branch of tee to displace out of the plane retaining run pipe steady is called Out-plane bending moment.

ASME B31.3 provide guidelines to evaluate SIF values through empirical formulation as per Appendix-D with few limitations listed below.

1. Valid for d/D < 0.5 only

2. Non-conservative for 0.5 < d/D < 1.0

3. Valid for D/T ≤ 100

4. SIF values calculated with respect to header pipe. There is no difference in SIF values for header and branch pipe and it is the average value.

WRC 329 was published in 1987 and has not been updated taking ASME B31.3 latest edition into account. PRG carried out SIF for the various sizes and types of tee fittings and prepared correlation equations through detailed FEA using nonlinear regression and test data.
Vibration Suppression Performance of a Desktop Vibration Isolator Supported by Four Air Spring
Authors: Baba Yuichi , Onishi Kento , Asami Toshihiko
Published: October 2017

Desktop vibration isolators are often used as precision measuring instruments. This article discusses the accuracy of performance prediction methods for vibration isolators elastically supported by four air springs. Each air spring possesses a reservoir tank to ensure the natural frequency of the support system remains low and to provide adequate damping force. For practical use, air springs and reservoir tanks should be installed in separate locations and connected by a small-diameter pipe because desktop isolators must be thin. Our previous studies have shown that there is a secondary resonance point in systems supported by air springs with long pipes and reservoir tanks and that it is not simple to theoretically calculate the amplitude and frequency at this point because this type of air spring support system has nonlinear characteristics. In this study, the change in the vibration isolation performance of a desktop vibration isolator with the length of the pipe connecting the main air tank and the reservoir tank of an air spring-supported system was examined experimentally and approximated using theoretical calculations.
Room Temperature Creep Behavior and its Effect on Tensile Properties of CP-Ti
Authors: Chang Le , Zhou Changyu , He Xiaohua
Published: October 2017

Commercial pure titanium (CP-Ti) is an attractive material, due to its good properties such as high strength, high specific work hardening ability, excellent plasticity, toughness, corrosion resistance and weld ability. It is commonly used in pressure vessels, such as heat exchangers, pumps, valves and so on. It has been reported that the room temperature creep has a great influence on the failure of titanium pressure vessel. In this paper, in order to investigate room temperature creep behavior and its effect on tensile properties of CP-Ti, both creep and tensile experiments were carried out. According to creep experiment results, CP-Ti shows strong stress dependent creep behavior at the creep stress higher than 305MPa. On the contrary, the strong loading rate dependent creep behavior occurs at the creep stress lower than 305MPa. Besides, creep strain of CP-Ti can be reduced by pretension. As pretension reaches 6%, creep behavior of CP-Ti is completely suppressed at the creep stress of 320MPa. Subsequent tensile test results show that the occurrence of room temperature creep obviously enhances the strength of CP-Ti. With the increase of creep strain and loading rate in previous creep tests, the yield strength and tensile strength of CP-Ti increase.
Mean Stress Effect on Fatigue Properties of Type 316 Stainless Steel: Part I — In High-Temperature Air Environment
Authors: Kamaya Masayuki
Published: October 2017

The mean stress effect on the fatigue life of Type 316 stainless steel was investigated at 325°C in air. It was shown that the fatigue life was extended by applying the mean stress under the same stress amplitude. Increase in the maximum peak stress by applying the mean stress induced additional plastic strain and this hardened the material. The strain range of the hardened material was relatively small for the same stress amplitude, and this extended the fatigue life for a given stress amplitude. On the other hand, the fatigue life was shortened by the mean stress for the same strain range. The mean stress increased the effective strain range due to an increase in the minimum peak stress. Also, the mean stress induced ratcheting strain during the fatigue test and this accelerated crack mouth opening. The enhanced crack mouth opening accelerated the crack growth and shortened the fatigue life for a given strain range.
Mean Stress Effect on Fatigue Properties of Type 316 Stainless Steel: Part II — In PWR Primary Water Environment
Authors: Kamaya Masayuki
Published: October 2017

The mean stress effect on the fatigue life of Type 316 stainless steel was investigated at 325°C in simulated PWR primary water. It was shown that, as shown in high-temperature air environment, the fatigue life was extended by applying the mean stress under the same stress amplitude. An increase in the maximum peak stress by applying the mean stress induced additional plastic strain and this hardened the material. On the other hand, the fatigue life was shortened by the mean stress for the same strain range. The ratcheting strain caused by applying mean stress accelerated crack mouth opening and reduced fatigue life. It was also shown that the fatigue life in the simulated PWR primary water was shorter than that in air even without the mean stress. The magnitude of the reduction depended on the strain range. The reduction in fatigue life was the maximum when the strain range was 0.6%. The environmental effect disappeared when the effective strain was less than 0.4%.
Dynamics Modeling and Analysis of Riveted Mainframe Computer Structure
Authors: Notohardjono Budy , Ecker Richard , Canfield Shawn
Published: October 2017

A typical mainframe computer rack is narrow, tall and long. In certain installations, during its functional operation, the server can be subjected to earthquake events. The rack is a steel structure joined together with steel rivets. One of the rack’s functions is to protect the critical components such as the processor, input-output and storage drawers from excessive motion by minimizing the amount of deflection. The riveted joints pose a challenge in accurately representing more than three thousand joints in a finite element (FE) model. In the FE model, bonding together sheet metal regions around the rivet joints will lead to a significantly stiffer model than the actual structure. On the other hand, an accurate representation of the riveted joints will lead to a better representation of the dynamic response of the server rack under vertical and horizontal loadings.

This paper presents a method of analyzing rivet joints. The rivet joints are represented by beam elements with cylindrical cross-sections in the FE model. This is accomplished by identifying two parallel or overlapping plates and inserting discrete beam elements at the riveted joint. This method will be used to predict the dynamics modes of the structure. To validate the FE model, a prototype server rack was subjected to side to side vibration tests. A sine sweep vibration test identifies dominant mode shapes and the transmissibility of the input vibration. The results of the tests on the prototype rack serve as input for FE model refinement. The test data show that representing the riveted joints with beams does provide results that closely match the actual test data. A validated FE model will be used to evaluate dominant vibration modes for several configurations of rack weight as well as configurations to stiffen the structure in the side to side direction. The dynamic mode shapes visualize the effect of stiffening brackets on dominant frequencies of the rack. The optimal stiffening design will be the one that results in the minimum deflection under the standard testing profile.
Pressure Vessel and Piping Hazard Analysis Methods Comparison
Authors: Edel Matthew , Ketchum Donald , Rodriguez Oscar
Published: October 2017

Pressure vessels and piping represent potential sources of hazards in the event of an accidental release. The most common hazards are typically projectiles, blast loads, and fluid spray. The ASME PCC-2 standard includes guidance for determining a safe standoff distance from projectiles and blast loads based on converting the stored energy in the system to an equivalent weight of high explosives (i.e., TNT). This paper investigates a case study where the PCC-2 methods are compared to results obtained using CFD modeling of blast loads and analytical methods of projectiles. Both results are then compared to test results.
Investigation of Flow Structure to Prevent Thermal Fatigue in a Downward Branch Pipe With a Closed End
Authors: Miyoshi Koji , Nakamura Akira
Published: October 2017

Many pipes branch off from the main pipes in power plants. Main flow with high velocity initiates a cavity flow in a downward branch pipe with a closed end. Hot water penetrates into the branch pipe and a thermally stratified layer forms in the branch pipe if the main flow is hot. Fluctuations of the thermally stratified layer may initiate wall temperature fluctuations and thermal fatigue cracks in the branch pipe. Penetration depth of the main flow and the fluctuation characteristics into the branch pipe with a closed end were investigated by experiments. Experiments were conducted for various inner diameters of a branch pipe and main flow velocities under room temperature conditions. Flow structure was observed by test section made of acrylic resin. A tracer method was used to measure the penetration depth of the main flow. The penetration depth of the main flow changed periodically. The maximum penetration depth of the main flow was correlated by the Reynolds number. The fluctuation range and period of the penetration depth were also investigated. Next, the flow patterns on the cross-sectional plane in the branch pipe were observed to investigate the fluctuation mechanism of penetration depth. Three flow patterns were observed on the cross-sectional plane in the branch pipe. They were flow parallel to the cross-sectional direction, flow consisting of small vortexes and large swirl flow. The generation period of the large swirl flow was nearly equal to the fluctuation period of the penetration depth. The fluctuation range of the penetration depth and the duration showed similar trends for different inner diameters of the branch pipe. These results showed that the fluctuation of the penetration depth was caused by the periodic generation of the large swirl flow.
Plastic Loads for Cones Subjected to Internal Pressure and Axial Tension
Authors: Błachut J. , Sala D.
Published: October 2017

The paper discusses envelopes of combined loading corresponding to: (i) first yield (ii) plastic load, and (iii) plastic instability load. The latter two were researched in the past but for a single load, only. The past idea has been expanded in the paper to two, practically relevant, simultaneously acting loads. Conical shell serves here as an example.

It is shown that the ratio of area of plastic load envelope to the area associated with the first-yield envelope is 3.2 whilst the similar ratio of plastic instability to the first-yield envelope amounts to 25.8. This indicates ‘a modest’ (320 %) increase of possible range of loading, and a substantial reserve of strength above the end-of-elastic behavior (approx. 26-times).
Study on Diffusion Area of Fluid Leakage With Pipe Failure
Authors: Watanabe Shun , Yoneda Kimitoshi
Published: October 2017

Light water reactors in Japan are expected to restart sequentially after given permission in condition to meet the new regulatory requirements. Since several safety related systems were added to the plants through the process of the new regulatory requirements, the numbers of components to be inspected, which is already a large amount, will increase even more after the restart in Japan. Effective measure will be required to command maintenance activities by reasonably assigning limited resource. The authors have planned a research project aiming optimization of maintenance considering influence of fluid leakage behavior with pipe failure, mainly targeting less-safety related piping and components. The experimental facility which has the ability to evaluate the fluid leakage behavior with pipe failure was constructed. By using this facility, it is able to conduct the test of the water jet, the flashing and the steam flow leaked from various flaw geometries of the piping.
Performance of All-Polypropylene Composites at LNG Temperatures
Authors: Atli-Veltin Bilim
Published: October 2017

In the small scale LNG infrastructure, composite materials are scarcely employed. Potentially, cost effective solutions for LNG applications could be developed thanks to the advantages of composite materials over metals such as weight savings, design flexibility and recyclability. The research presented in this paper focuses on the mechanical performance of fully recyclable, thermoplastic Polypropylene (PP) composite tapes at cryogenic LNG temperatures. Quasi-static tensile tests performed on [±45] laminates made of plain woven plies of PURE® show that at −196°C the behavior is bilinear with the failure strain of 6.5% and failure stress of 37 MPa. Such non-brittle failure behavior of PP is desirable for cryogenic applications. The other results presented in the paper contains [0/90] laminate results and the interlaminar shear strength characteristics at room and cryogenic temperatures.
Using Isochronous Method to Calculate Creep Damage: Part 1
Authors: Nadarajah Chithranjan , Hantz Benjamin F. , Krishnamurthy Sujay
Published: October 2017

This paper is Part 1 of two papers illustrating how isochronous curves can be used to determine creep stress and damage. In Part 1 of the paper two simple examples of two bars under axial load and a beam in pure bending are illustrated using a closed form solution to determine the creep stress and damage from an isochronous stress strain curves. For the two examples, the Omega material model was used for generating the isochronous stress strain curve and for computing the creep damage. The closed from solutions are compared with finite element analysis using isochronous stress strain curves as well as time explicit Omega creep model. The results from all the three analysis are found to be in good agreement.
Failure Mode of ED and AD Type Head Plates Subject to Convex Side Pressure
Authors: Yada Hiroki , Ando Masanori , Tsukimori Kazuyuki , Ichimiya Masakazu , Anoda Yoshinari
Published: October 2017

Containment vessel is an important structure to prevent a significant and sudden radioactive release, however, the safety margin of the containment vessel against the internal or external pressure are not numerically clarified. Namely, the safety margins due to the relationship of the ultimate toughness of containment vessel structures and maximum design pressure is not clear. Indeed, to clarify the progress of events under the beyond design basis events (BDBE) and to design the BDBE countermeasure equipment, it is necessary to evaluate the pressure toughness of containment vessel adequately. The containment vessel of fast reactor is composed of the various structures. The head plate that composes the boundary between primary and secondary coolant in intermediate heat exchanger has an important role when the progress of the BDBE is considered. Therefore, in order to develop the evaluation method of the pressure toughness of the head plate under the BDBE, the pressure failure tests and finite element analysis of head plate structure subjected to convex side pressure was performed in this study.

Two types of head plates were applied for pressure failure tests. ED type and AD type head plates were chosen as a representative to clarify the effect of shape. These head plates have 250mm diameter and 3mm thickness. The head plates were subjected to pressure on convex side by water in the pressure failure tests. In tests, almost completely inside-out of each head plate was caused after buckling.

Then after that, leakage was observed near the rim. Two types of head plates had similar failure mode in spite of difference original shapes. The circumferential through-wall crack was observed near the rim of each head plates.

According to the results of pressure failure tests, it is seemed that the circumferential crack was caused by straightening following bending associated with large deformation as inside-out. To clarify the relationship between bending radius and crack initiation, straightening following the bending deformation (bending-straightening) tests were performed.

As a result, the crack was initiated in the test case of the bending radius smaller than 3 mm. 3 mm of bending radius generate 33 % strain. The bending radius at the time of leakage observed of head plates was estimated almost similar value at which crack initiated. Therefore, it can be concluded that a failure mode of a head plate subjected convex side pressure is circumferential through-wall crack caused by straightening following bending deformation near the rim.
Numerical-Experimental Study on the Erosion-Cavitation Wear of Coal Oil Slurry Valve
Authors: Zheng Zhijian , Ou Guofu , Jin Haozhe
Published: October 2017

The coal oil slurry valves are located between the high pressure and intermediate pressure separators in the direct coal liquefaction unit. Because of the high pressure drop between the valve inlet and outlet, the cavitation occurs immediately once the coal oil slurry enters into the valve. Simultaneously, the severe erosion wear are also found on the valve components. Therefore, the erosion-cavitation wear has become a serious problem in the running of valve. In this paper, a numerical-experimental investigation on the erosion-cavitation wear of coal oil slurry valve is conducted. The cavitation experiments are used to verify the numerical modeling and calculation. Moreover, the expressions of functions used in the particle erosion model are defined from the erosion experiments in the high temperature environment. In the numerical simulation, the areas with the high risk of erosion-cavitation wear are predicted. The results showed that the most serious erosion-cavitation wear occurs on the top of valve spool. The particle erosion can also be found around the spool head. The numerical prediction of erosion-cavitation wear can be verified by the comparison between numerical results and actual failure morphology.
Considerations in Steam Piping Design for Prevention of an Acoustic Resonance at a Closed Side Branch
Authors: Morita Ryo , Uchiyama Yuta , Inada Fumio , Takahashi Shiro
Published: October 2017

Flow-induced acoustic resonances in piping with closed side branches or T-junctions are one of the causes of severe structural vibrations, which sometimes cause fatigue damage to piping and components in a power plant and many engineering applications. In this paper, on the basis of the results of steam flow experiments and calculations, the effects of the liquid phase on the flow-induced acoustic resonance at closed side branches in the steam flow piping of BWRs are described, and some suggestions for the steam piping design of BWRs are also given. The liquid phase in a steam flow forms droplets or liquid film, which may affect the amplitude, frequency and critical Strouhal number of the resonance. From the results of wet steam experiments and CFD calculations, we have found that in some cases the wetness of the steam flow may decrease the resonant amplitude and change the frequency owing to the interaction of the vortex generation or damping by the existence of the liquid film and droplets. Therefore, for the wet steam piping design of BWR, some suggestions for taking these effects into consideration, under actual BWR steam conditions are described.
INCEFA-PLUS (Increasing Safety in Nuclear Power Plants by Covering Gaps in Environmental Fatigue Assessment)
Authors: Mottershead Kevin , Bruchhausen Matthias , Métais Thomas , Cicero Sergio , Tice David
Published: October 2017

INCEFA-PLUS is a five year project supported by the European Commission HORIZON2020 program. The project commenced in mid-2015. 16 organizations from across Europe have combined forces to deliver new experimental data which will support the development of improved guidelines for assessment of environmental fatigue damage to ensure safe operation of nuclear power plants. Within INCEFA-PLUS, the effects of mean strain, hold time, strain amplitude and surface finish on fatigue endurance of austenitic stainless steels in light water reactor environments are being studied experimentally, these being issues of common interest to all participants. The data obtained are being collected and standardized in an online environmental fatigue database, implemented with the assistance of a CEN workshop led by members of the INCEFA-PLUS project. Later in the project it is planned that INCEFA-PLUS will develop and disseminate methods for including the new data into assessment approaches for environmental fatigue degradation.

This paper provides an update to the project introduction presented at PVP2016 (PVP2016-63149). In particular the paper presents the finalized matrix of test conditions for Phase 1 testing planned for 2017, including the agreed positions on testing for the effects of mean stress/strain and hold time. The materials being tested are summarized, together with available material characterization data. The specimen surface finishes used in the phase 1 testing are described, including measures taken to ensure uniformity of surface conditions throughout the consortium and characterization results for the two chosen surface finishes for each specimen geometry and material. The emerging plans for Phase 2 testing is also described, with a focus on steps being taken to enable more plant-relevant testing for the effects of mean stress and exploration of sensitivities to hold times within plant transients. The latest view on how the project results will be used to advance development of improved assessment guidelines is also discussed. An update is provided on the discussions at the CEN workshop on Standards-Compliant Formats for Fatigue Test Data (FATEDA) including progress towards agreeing test data formats and trials of XML data transfers from laboratory to database. Finally, a summary is provided of project dissemination activities.
Complex Low-Cycle Fatigue Damage Assessment of Components and Piping of Nuclear Power Plants Type WWER
Authors: Vlcek Libor , Junek Lubomir
Published: October 2017

An innovative principle of low-cycle fatigue (LCF) life assessment suggested for WWER nuclear power plants is presented. In the design stage the fatigue life assessment is based on fatigue design curves, which are introduced in graphical form for air environment. Alternatively and especially for operational stage the fatigue curves are constructed on the basis of mathematical formulas. Mathematical descriptions were validated by strain-controlled LCF laboratory tests. Due to such validated mathematical formulas the complex LCF damage analyses of nuclear power plant components and piping are enabled. In the frame of complex LCF assessment the influence of operating temperatures, stress asymmetry ratio, corrosion environment, neutron fluency and multiaxial loading can be taken into account not only for the base steel materials, but also for their welds. The aim of this paper is to summarise the whole methodology of complex LCF assessment and damage prediction including operational limits of fatigue damage defined in the Czech nuclear standard. The innovation process of original Russian LCF formulas has been running since 2010 based on three national R&D projects focused mainly on environmental aspects and multiaxial loading.
Fracture Assessments of High Pressure Vessel Components Having Longitudinal Holes
Authors: Xu Yu , Young Kuao-John
Published: October 2017

Small size longitudinal holes are common in components of high pressure vessels. In fracture mechanics evaluation, longitudinal holes have not drawn as much attention as cross-bores. However, longitudinal holes become critical at certain locations for such assessments because of high stress concentration and short distance to vessel component wall. The high stress concentration can be attributed to three parts: global hoop stress that is magnified by the existence of the hole, local stresses due to pressure in the hole, and crack face pressure. In high pressure vessel design, axisymmetric models are used extensively in stress analyses, and their results are subsequently employed to identify critical locations for fracture mechanics evaluation. However, axisymmetric models ignore longitudinal holes and therefore cannot be used to identify the critical location inside the holes. This paper is intended to highlight the importance of including longitudinal holes in fracture mechanics evaluation, and to present a quick and effective way of evaluating high stress concentration at a longitudinal hole using the combined analytical solutions and axisymmetric stress analysis results, identifying critical locations and conducting fracture mechanics evaluation.
Cost-Effective Alternatives to Conventional Charpy Tests for Measuring the Impact Toughness of Very-High-Toughness Steels
Authors: Lucon Enrico
Published: October 2017

For modern plate steels exhibiting high toughness and ductility, the conventional Charpy test is ostensibly stretched beyond its limits of applicability. Impact tests yield absorbed energy values in excess of 300 J – 400 J, which are associated with limited material fracture and mostly derive from plastic deformation of the specimen (bending), friction and vibrations of the swinging hammer. It would be therefore very desirable to measure the actual fracture toughness of very-high-toughness steels by means of an alternative specimen and/or methodology, entailing just a moderate increase of cost and test complexity with respect to Charpy testing. The investigation presented here was aimed at establishing a reasonable, yet cost-effective test procedure utilizing Charpy-type specimens for measuring the dynamic toughness of high-toughness steels, such as line pipe steels. Promising results have been obtained from notches cut by Electrical-Discharge Machining (EDM) using a thin wire of 0.1 mm diameter, as compared to specimens where an actual crack was generated and propagated by fatigue at the root of the machined notch.
Fretting-Wear Damage due to Vibration in Nuclear and Process Equipment
Authors: Pettigrew Michel J. , Yetisir Metin , Fisher Nigel J. , Smith Bruce A. W. , Taylor Colette E. , Janzen Victor P.
Published: October 2017

The problem of fretting-wear damage between a vibrating structure and its supports is discussed in this paper. Typical components of concern are piping systems and pipe-supports, multispan heat exchanger tubes and tube supports, and nuclear fuel bundles and fuel channels.

Fretting-wear damage is related to the dynamic interaction between a structure and its supports. This interaction is conveniently formulated in terms of a parameter called “work rate” to predict fretting-wear damage. Work rate is simply the integral of contact force over sliding distance per unit time.

Fretting-wear damage may be investigated from an energy point of view. It is essentially the mechanical energy or power dissipated through contact forces and sliding that causes fretting-wear damage. Development of a simple formulation that relates tube vibration response and fretting-wear damage is reviewed in this paper. Some new practical examples and simple calculations are discussed.
Optimization of the Receipt and Delivery Schedules for a Transfer Tank Farm of Products Pipeline Network
Authors: Wang Li , Wu Changchun , Zuo Lili , Huang Yanfei , Chen Haihong
Published: October 2017

Transfer tank farms play an important role in an oil products pipeline network, which receive oil products from upstream pipelines and deliver them to downstream pipelines. The scheduling problem for oil products supply chain is very complicated because of numerous constraints to be considered. The published literatures on schedule optimization of oil products pipeline network usually focus on the batch plans of each pipeline, without consideration on the receipt and delivery schedule of transfer tank farm. In this paper, a mixed-integer linear programming (MILP) model is developed for the schedule optimization of transfer tank farm. The objective of the model is to minimize switching times of the tank operations of a tank farm during a planning horizon, while fulfilling the products transmission requirements of the upstream and downstream pipelines of the tank farm. The constraints of the model include material balance, the operational rules of tanks, the topological structure constraints of the tank farm, the settling period of the oil products stored in dedicated tank and so on. To satisfy the constraint of fulfilling the specific transmission requirements of pipelines, concepts of static and dynamic time slot are proposed. A continuous time representation is used to obtain accurate optimal schedules and decrease scale of the model by reducing the number of variables. The model is solved by CPLEX solver for a transfer tank farm of an oil products pipeline network in China. Some examples are tested under different scenarios and the results show that global optimal solution can be obtain at acceptable computational costs.
Age 60+ — Applicability of Ageing Related Data Bases and Methodologies for Ensuring Safe Operation of LWR Beyond 60 Years
Authors: Ortner Susan , Brumovsky Milan
Published: October 2017

The AGE60+ project aimed towards the application of ageing related data bases and methodologies to ensuring the safe operation of Light Water Reactors beyond 60 years, and the longer-term safe storage of waste. It acted by encouraging European researchers to share data in order to maximize its utility.

As an initial step, the AGE60+ consortium considered the development and utilization of a number of databases set up to collate data and derive information relevant to the management of nuclear power plant. This review was used to identify the factors which lead to a database successfully making a useful contribution.

The AGE60+ project has been a very fruitful collaboration. It has:

• Raised the concept of sharing data and setting up databases related to the ageing of concrete in waste disposal, and received a generally positive response to this first step.

• Identified an area in which a new database would provide the opportunity to advance predictive modeling of the degradation of internals.

• Collated and reviewed data on the thermal ageing of low alloy steels.

• Identified information gaps in the area of internals degradation and the thermal ageing of low alloy steel components.

• Produced an up-to-date database on WWER-440 RPV steel embrittlement.

• Produced a new embrittlement trend curve (ETC), relating the fracture toughness transition temperature to fluence and composition for WWER-440 weld and base metal.

• Expanded and utilized a database on MnMoNi steel embrittlement.

This AGE 60+ project was realized as a part of the NUGENIA+ Call and lasted 18 months with participating organizations: UJV Rez a.s., Czech Republic, AREVA GmbH, Germany, CIEMAT, Spain, MTA EK, Hungary and NNL, UK as a leading organization.