bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Material Databook for API Std 530
Authors: Prager M. , Osage D. A. , Panzarella C. H. , Brown R. G.
Published: November 2014

In 2005, the American Petroleum Institute (API) initiated an effort to update existing yield, tensile and stress-rupture properties found in API Standard 530 Calculation of Heater Tube Thickness in Petroleum Refineries and add properties for alloys not yet covered. The design curves in API 530 until that time were based on data gathered 40 to 50 years earlier by the Materials Properties Council (MPC) and its predecessor, the ASTM-ASME Joint Committee on the Effects of Temperature on Materials. Later, MPC developed proprietary statistically sound algorithms to apply lot-centered regression for parametric analysis of large, unbalanced data sets of diverse heats tested under a variety of conditions. Subsequently, MPC built and maintained archives on the creep and stress-rupture data of alloys of interest to API. For some alloys the data sets contained over a thousand test results on over 100 heats. To assure that future designs will reflect the properties of materials produced using modern practices, API requested MPC to deliver design properties applicable to current materials. This paper presents the back ground, principles and results of the recent analyses performed by MPC that are now available for use by the API membership. The properties furnished in equation format are yield and ultimate tensile strengths for time-independent stresses and results of lot centered Larson-Miller Parameter analyses to obtain time-dependent average and minimum strengths. The properties and application examples of the equations are published as WRC Bulletin 541 Evaluation of Material Strength Data for Use in API Std 530.
Estimation of Graphite Dust Production in a Pebble-Bed Type Nuclear Reflector
Authors: Kang Ji-Ho , Kim Eung Seon , Cho Seungyon
Published: November 2014

In this study, an estimation method of graphite dust production in the pebble-bed type reflector region of Korean HCSB (Helium-Cooled Solid Breeder) TBM (Test Blanket Module) in the ITER (International Thermonuclear Experimental Reactor) project using FEM (Finite Element Method) was proposed and the amount of dust production was calculated. A unit-cell model of uniformly arranged pebbles was defined with appropriate thermal and mechanical loadings. A commercial FEM program, Abaqus V6.10 was used to model and solve the stress field under multiple contact constraints between pebbles in the unit-cell. Resulting normal contact forces and slip distances on contact points were applied into the Archard adhesive wear equation to calculate the amount of graphite dust. The friction effect on contact points was investigated. The calculation result showed that the amount of graphite dust production was estimated to 2.22∼3.67e−4 g/m3 which was almost linearly proportional to the friction coefficient. The analysis results will be used as the basis data for the consecutive study of dust explosion.
Determination of Creep Properties of PE 4710 Cell Classification 445574C High Density Polyethylene
Authors: Adams Timothy M. , Nickholds Shawn , Munson Douglas , Andrasik Jeffery
Published: November 2014

For corroded piping in low temperature systems, such as service water systems in nuclear power plants, replacement of carbon steel piping with high density polyethylene (HDPE) is a cost-effective solution. Polyethylene pipe can be installed at much lower labor costs than carbon steel pipe and HDPE pipe has a much greater resistance to corrosion. The ASME Boiler and Pressure Vessel Code, Section III, Division 1 currently permits the use of non-metallic piping in buried safety Class 3 piping systems. Additionally, HDPE pipe has been successfully used in non-safety-related systems in nuclear power facilities and is commonly used in other industries such as water mains and natural gas pipelines. This paper presents the results of creep testing of PE 4710 cell classification 445574C pipe compliant with ASME Boiler and Pressure Vessel Code material requirements. This information was developed to support and provide a strong technical basis for material properties of HDPE pipe for use in ASME Boiler and Pressure Vessel Code, Section III New Construction and Section XI repair or replacement activities. The data may also be useful for applications of HDPE pipe in commercial electric power generation facilities and chemical, process and waste water plants via its possible use in the B31 series piping codes. The report provides long term creep and modulus data, as well as an analysis of the stress dependency of both.
Estimation of Crack Growth Rate by J-Integral Range for Type SUS304 Stainless Steel Plate in Creep-Fatigue Tests at High Temperature
Authors: Funai Madoka , Watanabe Osamu , Matsuda Akihiro
Published: November 2014

In structures having stress concentration under cyclic loading, a small crack initiates and it grows and propagates. Evaluating crack growth is important to estimate the remaining life of cracked components.

The present paper shows the estimation of crack growth rate under creep-fatigue loading with some patterns of strain holding times.

Creep-fatigue tests of the perforated plate having initial crack were conducted with the different strain holding time under strain-controlled loading at 550°C. The crack growth was observed from the photographs taken at each cycle. The crack growth per one cycle of creep-fatigue loading was evaluated by the creep-fatigue crack propagation law which used increment J-integral range. Comparing the crack growth rates of experimental with those of predicted, the crack growth rates were predicted by using increment J-integral range with the accuracy was factor of 2.
Inelastic FE Analysis for J-Integral of Center-Cracked Plate in Creep-Fatigue Range
Authors: Funai Madoka , Watanabe Osamu , Matsuda Akihiro
Published: November 2014

In order to estimate crack growth rate, it is necessary to use increments of the J-integral for both of time-independent fatigue process and time-dependent creep process. Many researchers and methodologies use C* to characterize creep crack growth and ΔJ or ΔK for fatigue crack growth, suggested are the following Refs.[1,2] This paper shows the fundamental features of J-integral in elastic, plastic and creep range. The path dependency is studied for center-cracked plate by using path integral from the large path to the small path near crack tip. The inelastic FE analysis is carried out for creep-fatigue loading, where the tensile strain is held constant to receive creep damage, and this paper shows the J-integral according to the loading histories. Also discussed are effects of the strain rate in fatigue process to affect the successive creep behavior.
Wave Propagation of Water Hammer in Compound Tube
Authors: Takeda Kengo , Inaba Kazuaki , Takahashi Kosuke
Published: November 2014

There are pipes with square or rectangular cross sectional shape rather than more common circular shape. Moreover, a part of the walls can be made of different materials or have different wall thicknesses. To estimate pressure wave propagation in such a channel, we examined water hammer phenomenon and measured wave speeds in rectangular tubes assembled with different wall materials and thicknesses by strain gages and pressure transducers. We newly proposed theoretical wave speeds based on the classical theory and the junction conditions of two walls: fixed, simply supported, and mixed supported. Circumferential strains on the wall can be estimated from the different forms derived by the different junction conditions. We confirmed that theoretical predictions with the simply supported conditions agreed with experimental wave speed in compound tubes, while wave speeds in ready-made square tubes with the same wall-thickness were close to those by the fixed conditions.
Study on Strength of Thin-Walled Tee Pipe for Fast Breeder Reactors Under Seismic Loading
Authors: Watakabe Tomoyoshi , Tsukimori Kazuyuki , Otani Akihito , Moriizumi Makoto , Kaneko Naoaki
Published: November 2014

In recent years, earthquakes over design condition were observed in Japan. Confirming the ultimate strength and design safety margin of mechanical components is important for the seismic integrity. This study focused on piping components, and it was one of the most important mechanical components for protecting boundary of coolant. Failure tests of thick-walled piping components for Light Water Reactors (LWRs) described previously in the literature. According to these tests, the failure mode of thick-walled piping components under seismic cyclic loading was low cycle fatigue. However, failure tests have scarcely been performed on thin-walled piping components pressurized at low levels for Fast Breeder Reactors (FBRs).

This paper presents dynamic failure tests of thin-walled piping components in FBRs. Based on the test results, the failure mode, the ultimate strength, and the elastic-plastic behavior are discussed.
On Control Factors for the Oscillation of a Simplified Flip-Flop Jet Nozzle
Authors: Umemura Kazuki , Kobayashi Ryohei , Inoue Tatsuya , Tanigawa Hirochika , Hirata Katsuya
Published: November 2014

The authors experimentally investigate a self-excited oscillatory phenomenon of a two-dimensional confined jet with a cylinder as a downstream target, especially for the effect of a streamwise target size a. As a result, the authors find that the jet’s dominant frequency fD can be approximately predicted by the proposed empirical formula (Hirata et al., 2011), whenever the jet stably oscillates at various values of the non-dimensional streamwise target size a/b where b denotes the length scale of the jet’s breadth. The effect of a/b upon the occurrence of the stable jet oscillation is negligible for a/b ≤ 10. Then, the occurrence of oscillations can be predicted by the proposed empirical formula (Hirata et al., 2009). On the other hand, for a/b > 10, the a/b effect is not negligible. In addition, the authors conduct numerical analyses, which reveal the two-dimensionality of the concerning phenomenon.
Statistical Analysis of Seismic Effects of Low Seismic Class Equipment Based on Damage Data of Nuclear Power Plants
Authors: Morita Ryo , Inada Fumio , Ohtori Yasuki , Nanpo Mitsuhide , Naradate Koji , Yamaguchi Syuhei , Takeuchi Masataka , Yamaguchi Tatsuya , Numata Takeshi , Tamura Ichiro , Hosotani Terushige , Kimura Yusuke , Amemiya Mitsuhiko , Taguchi Toyonobu , Fukushi Naomi , Yamaguchi Atsushi , Kojima Nobuyuki
Published: November 2014

Structural strengths of the piping and components in NPPs have been designed with seismic margin. They are classified seismically S, B and C class in terms of the influence rate to nuclear safety. For the highest seismic class (Class S) equipment, it is clarified that they have enough seismic margins against design seismic conditions by shaking table tests or numerical simulations. However, for the lower seismic class (Class B and C) equipment, their seismic margins have not been clarified quantitatively.

In this paper, in order to evaluate seismic robustness of the lower seismic class equipment with no clarification of seismic margin, seismic influences of the lower seismic class equipment in NPPs damaged by actual large earthquakes have been surveyed and sorted as a database, and the integrity of the lower class equipment have been discussed.

Seismic effects on 24 plants damaged by the recent large 6-earthquakes are surveyed, sorted as a database, and investigated. As a result, a total of 29 cases of function deterioration or loss were observed. Considering the total number of components and piping, the frequency of those cases in class B and C components and piping was low. And also, as it is found there are a few cases of degradation or loss of function in the equipment installed on the bedrock or in the buildings.
A Comparison of Notch Failure Assessment Diagram Methods for Assessing the Fracture Resistance of Structures Containing Non-Sharp Defects
Authors: Horn Anthony J. , Budden Peter J.
Published: November 2014

This paper analyses and compares a range of Notch Failure Assessment Diagram (NFAD) methods for assessing the fracture resistance of structures and components that contain defects with non-sharp tips. As micromechanistic failure criteria for predicting fracture from notch tips have developed, several forms of NFADs have been proposed over the last 20 years with notable developments having been made in the last 10 years. This paper quantifies the differences between four different types of NFAD approach and uses test results from test specimens containing notches of varying acuities to evaluate each approach. The results highlight significant differences in fracture predictions between the different NFAD approaches due to differences in the definition of the NFAD axes, the failure loci, the assumed failure mechanism and the corresponding micromechanistic failure criteria employed by each method.
Fatigue Capacity of Steel Cylindrical Bodies and Conduits Subjected to Cyclic Pressure
Authors: Wormsen Anders , Kirkemo Finn , Muff Anthony David
Published: November 2014

This paper presents a code review (API 17G, ASME VIII Div 2 and ASME VIII Div 3) for addressing the fatigue capacity of steel cylindrical bodies and conduits subjected to cyclic pressure only. The fatigue capacity for pipes with a yield strength of 75ksi and 90ksi and with rated working pressures (RWP) ranging from 5ksi to 30ksi have been considered using both the S-N approach and the fracture mechanic approach. The S-N based fatigue lives from API 17G are found to be much longer than the corresponding S-N based fatigue lives from ASME VIII Div 2 and Div 3 and by the fracture mechanic (FM) approach as required in ASME VIII Div 3 for vessels where a leak-before-break condition can not be demonstrated. The S-N predicted fatigue lives are found to decrease with increasing RWP while the FM based fatigue lives are found to be rather independent of the RWP. The S-N based fatigue lives from ASME VIII Div 2 and Div 3 for free corrosion conditions are found to be shorter than the corresponding FM based fatigue lives for RWPs ≥ 25ksi and ≥ 20ksi, respectively. Based on this work, it is recommended to establish the fatigue capacity of steel cylindrical bodies and conduits subjected to cyclic pressure using either ASME VIII Div 2 or Div 3. The FM approach is considered to give a lower bound fatigue life as the number of cycles to initiate a crack is disregarded. Guidance on when it is considered applicable to use the API 17G criterion is given in the conclusion section of this paper.
Research on Ultrasonic Testing for Electro-Fusion Joint of Reinforced Thermoplastic Pipes
Authors: Guo Weican , Shi Jianfeng , Zheng Jinyang , Liu Zhongqiang
Published: November 2014

Reinforced Thermoplastic Pipe (RTP) is generally connected by butt fusion joint or electro-fusion joint with intensified sleeves. Contrast to regular electro-fusion joints for PE (polyethylene) pipe, those for RTP are of larger length and thickness. Based on the ultrasonic inspection research of electro-fusion joint of PE pipe, the authors designed a special phased array probe for the electro-fusion sleeve of RTP considering its complicated structure and large size. A special C-scan technique was proposed including a longitudinal scan carried out with electronic method and circumferential scan carried out with mechanical method. Meanwhile, special software was designed to ensure the synchronization and precision control between longitudinal electronic scan and circumferential mechanical scan, and the consistency control between ultrasonic information and position information. Based on the results of detection experiments of RTP electro-fusion joint with typical defects, it was proven that this technique has the capability to detect typical defects in RTP electro-fusion joint, and high testing sensitivity was obtained.
Potential Difference Distribution on Flat Plate Around Semi-Ellipsoidal Thinning on the Back Surface
Authors: Tada Naoya , Uchida Makoto , Nohara Manabu
Published: November 2014

Local wall thinning is one of serious problems in aged power generating plants and is known to occur mainly by Flow Accelerated Corrosion (FAC) and Liquid Droplet Impingement (LDI) erosion. As the thinning grows inside the pipes, it is difficult to detect and evaluate it from the outer surface of pipe. The direct-current potential difference method (DC-PDM) is thought to be a suitable non-destructive technique to monitor the initiation and growth of these damages. In this study, an approximate analysis method of the potential difference around a semi-ellipsoidal thinning on the back surface of flat plate is presented and the accuracy is discussed based on the results obtained by the finite element analyses.
Failure Analysis of Burner Muffle in Shell Gasifier
Authors: Liu Wen , Shi Jin , Chen Qiuping , Xie Guoshan , Zhou Yufeng , Xu Wenhui
Published: November 2014

The failure of burner muffles in shell gasifiers has been a common problem, which directly leads to unexpected shutdown in operation of the gasifier and huge economic losses for the factory. Therefore, the experiment of the failure analysis to the burner muffle was conducted in the current work. The microstructure of the burner muffle after failure was measured by means of optical microscope, SEM (scanning electro-microscope) and X-ray diffraction. The reason of failure was obtained based on the analysis of experimental data together with the structural study of the gasifier. It is indicated that the failure of burner muffle is accounted for slag overflow and “backfire”, which lead to local temperature increasing. Cooling water tubes of Burner muffle were partially melted due to oxidation and sulphidation at high temperature, resulting into water leaks.
Thermal Aging Effects on Microstructures of Type-II Boundary in Dissimilar Metal Weld Joints
Authors: Yoo Seung Chang , Choi Kyoung Joon , Kim Ji Hyun
Published: November 2014

In order to investigate the long-term thermal aging effects on the type-II boundary region in Alloy 152 weld metal, a representative dissimilar weld mock-up made of Alloy 690–Alloy 152–A533 Gr. B has been fabricated and heat treated under accelerated temperature conditions. To simulate the thermal aging effects, the heat treatment was performed at 450°C for 15, 30 and 60-yr equivalent times (1,375, 2,750 and 5,500 h). The aging time was determined by the diffusion equation based on the activation energy for chromium diffusion. The microstructure characterization was primarily conducted in the type-II boundary region of the weld root, which is a boundary parallel to fusion boundary existing within 100um from the fusion boundary and is known to be less resistant to stress corrosion cracking than other regions in the weld. The investigations were performed by scanning electron microscope, electron backscatter diffraction, and nanoindentation test. In this study, the dilution zone of the chromium content was observed at the weld metal region within a 1.5-mm range from the fusion boundary. Ferrites and high angle grain boundaries are found at the type-II boundary region of weld metal. In the narrow zone between the type-II boundary and fusion boundary, the hardness is relatively higher than that of other regions. These results show that the chromium content in the dilution zone increases with heat treatment, but the stiff chemical gradient still exists in the weld region at the narrow zone between the type-II boundary and fusion boundary.
Reheat Cracking Sensitivity of CGHAZ in Vanadium-Modified 2.25Cr1Mo Welds
Authors: Han Yichun , Chen Xuedong , Fan Zhichao , Bu Huaquan , Zhou Yu
Published: November 2014

Over the past few years, some reheat cracks have been detected in the welding coarse grained heat affected zones (CGHAZ) of Vanadium-modified (V-mod) 2.25Cr1Mo reactor. Focusing on this problem, a series of Gleeble high temperature tensile tests were carried out on the simulation CGHAZ specimens of V-mod 2.25Cr1Mo at different temperature and strain rate, the reheat cracking sensitivity of CGHAZ has been assessed according to the reduction of area (RoA) of the specimens. Microstructural observation, hardness test and fractographic analysis also have been employed to ascertain possible causes for the effects of temperature and strain rate on the reheat cracking sensitivity.

The results of tests show that the reheat cracking sensitivity of CGHAZ increases with a decreasing strain rate, it first increases and then decreases with a rising test temperature. The RoA presents a minimum value around 675°C, corresponding to the most sensitive temperature to reheat cracking. The comprehensive analysis reveals that the ductility of the simulated CGHAZ at elevated temperature is closely related to the tensile strength and the hardness of fractured tensile specimen. In the intermediate temperature range or at a slower strain rate, a relatively high hardness and relatively low tensile strength together results in a low RoA of the specimen and high reheat cracking sensitivity of CGHAZ metal.
AREVA’s Modularized Fatigue Monitoring for Lifetime Extension and Flexible Plant Operation
Authors: Heinz Benedikt , Wu David
Published: November 2014

For plant lifetime extension programs, AREVA provides a customized solution for thermal load monitoring and fatigue calculation. Requirements like environmental assisted fatigue effects or flexible plant operation (load following) have crucial impacts for a detailed fatigue assessment. With a modularized monitoring concept and automated simplified fatigue estimation technique, plant components can be monitored very cost efficiently with validated methodologies, providing flexible, fast and accurate results. The layout of the modularized monitoring system is simplified and different options can be added on demand. With the automated fatigue assessment, thermal transients can be classified and a cumulative usage factor can be estimated on-line. With the help of this method, the impact of thermal transients to the component fatigue can be evaluated just in time. That can be a piece of important information to get for a better knowledge about the plant behavior during flexible operating (load following) modes.
FEM Stress Analysis and Sealing Performance Evaluation in Bolted Flange Connections With Metal Flat Gasket Subjected to Bending Moment and Internal Pressure
Authors: Kondo Koji , Omiya Yuya , Tsubaki Shota , Sawa Toshiyuki
Published: November 2014

Bolted flange connections with metal gasket have been used at higher pressure under higher temperature condition. Assembly procedures and tightening methods the connections including some types of metal gasket is empirically. Generally, it is known that the bolt preload which is required for satisfying an indicated leak rate in the connections including the metal gasket is not higher than that of the connections including sheet gaskets and spiral wound gaskets. However, no research for the evaluating the sealing performance in the bolted flange connections with metal gaskets has been conducted. In this paper, the leakage tests for the bolted flange connections with the metal flat gasket were conducted in the case where the maximum internal pressure of 7MPa and a bending moment are applied, where the leak rate is measured using the pressure drop method. Then, the sealing performance of the connections with the metal flat gasket was evaluated. In addition, using the FEM stress calculations, the flange stress distributions between the flange surface and the gasket were examined as the evaluation. As the result, it is found that the stress distribution at the contact surfaces between the metal flat gasket and the flange surface under the bending moment and the internal pressure. In the leakage tests, it was observed that the amount of the leakage (He gas) depends on the stress distributions and the plastic deformation of the gasket.
The Rocking and Stability of Spent Fuel Casks
Authors: Ananth Raju , Day Shari , Bose Mrinal
Published: November 2014

This paper describes an analytical and numerical study performed to benchmark LS-DYNA computer analysis of the response of a stacked spent fuel cask system to seismic base excitation. The LS-DYNA solution of the rocking block problem and stability of the block under the action of a base acceleration pulse are compared to the inverted pendulum solution first published by George W. Housner in 1963. Housner’s work has been cited by a number of subsequent investigations exploring the physics behind the rocking block problem, including Yim and Chopra [2]. The analytical formulation of the rocking block problem is derived in 2D in this paper. As is the case in many of the previous formulations, the solutions are provided after linearization of the governing equations.

The stability of the unanchored block subjected to an acceleration pulse is solved using the energy method. The solution displays key differences relative to Housner’s minimum acceleration required to overturn. An alternate equation for effective viscous damping is also presented, which differs from the formulation given in Appendix A of ASCE 43-05 [9]. Simulation of the rocking block problem using LS-DYNA is shown to faithfully reproduce the classical solution, albeit at lower levels of energy loss. Effective damping and minimum acceleration to overturn from the LS-DYNA benchmark agree with predictions of the classical solution even after linearization.
Measurement of High Amplitude Relief Valve Noise for Acoustically Induced Vibration and Comparison to Predictive Methods
Authors: Evans Neal
Published: November 2014

The prediction of acoustically induced vibration (AIV) failures in the design or redesign of piping systems requires an accurate estimate of the excitation source. Furthermore, the next generation of AIV analysis may require a physics-based noise-generation predictive technique, which entails the need for validation via direct measurements. The noise generated by a pressure relief valve (PRV) during a full-scale AIV blowdown test was measured inside a pipe downstream of the valve. A maximum flow rate of 33.5 kg/s was achieved using nitrogen gas through a 3×4″ relief valve generating a peak dynamic pressure level exceeding 650 kPa and sustained levels of 450 kPa (peak). Measurements are compared to existing noise calculation techniques which appear to under-predict the generated noise.
Validation of Thermal Stress Ratcheting Criteria
Authors: McKillop Suzanne , Reinhardt Wolf , Reddy Vangala , Koski William
Published: November 2014

Design of components against incremental deformation or “ratcheting” under cyclic loading conditions is addressed in Article NB-3200 of Section III of the ASME Boiler and Pressure Vessel Code. The ratcheting rules, based on the Bree diagram, relate primary stress and secondary stress ranges that are calculated elastically and aim to approximate elastic-plastic material behaviors under cyclic loading. The Bree diagram was developed for cases with through-thickness thermal bending and constant primary membrane stress. It does not account for high thermal membrane stress that can occur near gross structural or thermal discontinuities. Cyclic thermal membrane stress combined with sustained stress can lead to ratcheting that is not accounted for in the current design rules.

This paper discusses the validation of proposed criteria for evaluating thermal stress ratcheting under high thermal membrane stress using an elastic analysis. These proposed criteria are confirmed by an analysis of a nozzle that is attached by a partial penetration weld to a vessel head and subjected to severe thermal cycling. Linearized stresses from an elastic analysis under pressure and thermal loadings typical for a nuclear power plant are compared to limits in NB-3200 for thermal stress ratcheting. Additionally, an elastic-perfectly plastic analysis is used to evaluate if the component will shakedown.

This analysis demonstrates that the proposed rules prevent ratcheting of a typical geometry with typical operating loads in a nuclear plant. The current thermal stress ratcheting rules evaluated on an elastic basis are enhanced to cover cases with high thermal membrane stress while not removing conservatism. Additionally, the evaluation of the simplified elastic-plastic rules for thermal stress ratcheting are simplified.
Experimental and Analytical Study for Collapse Characteristics of 45 Deg Cylinder-to-Cylinder Intersections
Authors: Kataoka Shunji , Sato Takuya , Honda Takuro , Takeda Masashi , Tanimoto Toshiya
Published: November 2014

The 45-degree laterals are widely used in pressure vessel nozzles and piping branch connections. Though the pressure design is always important for the 45-degree laterals, it is not a simple work because it has severe stress concentrations, it is difficult to weld and inspect, and there are some discrepancy between a conventional design and design by linear and nonlinear finite element analysis. In previous papers, authors studied the characteristics of both 90 degree tee and 45 degree laterals using an inelastic finite element analysis based on simplified shell element models and proposed Collapse Strength Reduction Factor (CSRF) based on an inelastic analysis were compared. In this paper, results of the burst test of 45-degree lateral and 90 degree intersection were shown. The fracture surface of 45-degree lateral was different from that of 90-degree intersection. These experimental results are compared with the inelastic finite element analysis results focusing on the local stress and strain behaviors. It was found that the magnitude of the local strain affected the burst pressure. Consideration should be given on the local failure due to excessive plastic strain under high stress triaxiality for the design of the 45-degree lateral by inelastic analysis.
Blast Adjustment Factors for Elevated Vertical Cylindrical PVBs
Authors: Geng Jihui , Baker Quentin , Thomas Kelly
Published: November 2014

Pressure vessel burst (PVB) is an explosion scenario commonly encountered at chemical processing facilities. PVBs pose both blast and fragmentation hazards. Blast prediction methods specific to PVBs were first developed in the 1970s and revised blast curves were published in 1995. The published blast curves were developed for spherical vessel bursts. However, most pressure vessels are cylindrical rather than spherical. The blast wave originating from a cylindrical PVB is not spherical (i.e., as with a spherical vessel). Rather, the blast to the sides of a cylindrical vessel is stronger than on the ends, creating non-spherical pressure contours, particularly near the vessel. The cylindrical vessel directional blast effect has recently been investigated by the authors, resulting in a correlation to account for the directional effects. However, it was assumed in the prior work that the vessel was at ground level. This paper extends the prior work to elevated PVBs. Both elevated spherical and cylindrical PVBs are examined to provide new correlations for blast overpressure and impulse for a range of vessel geometries and burst conditions.
Evaluation of Mass Transfer Coefficient Under Swirl Flow Generated by the Combination of Pipe Elements: Part 3 — Analysis of Geometry Factor Under Swirl Flow on Pipe Element
Authors: Matsushita Mikiya , Yamamoto Kei , Nakamura Takao
Published: November 2014

Flow accelerated corrosion (FAC) is a major pipe wall thinning phenomena in power plant. The management of pipe wall thinning is carried out in pipe elements such as elbow, T-tube, orifice, etc. of piping system in power plants. Wall thinning estimation methods in the management is usually applied with pipe wall thickness measurement in Japan.

In piping system, it is known that several pipe elements that are connected in series generate swirl flow. In Mihama Unit 3 pipe failure accident in 2004, it is pointed out the swirl flow caused by the piping layout might influence thinning rate behind orifice. Therefore the arrangement of pipe elements is considered to affect thinning phenomena seriously. So the behavior of swirl flow is one of the major research items to improve FAC model.

The purpose of this paper is to study the influence of swirl flow on wall thinning phenomena generated by the combination of pipe elements. This study focuses on the conditions and parameters (combination, distance, curvature radius of elbow, etc. of pipe elements) that affect the generation of swirl flow and analyzes the effect of such parameters in mass transfer coefficient and flow field of main-stream of swirl flow behind pipe elements. It is expected that axial velocity of main-stream of swirl flow affects distribution of geometry factor under swirl flow on pipe element.

The results of this study will be reflected to the evaluation of fluid-dynamic factor of FAC and can improve the management of wall thinning.
Constraint Effects in Ductile Fracture on J-Resistance Curve for Full-Scale Cracked Pipes and Fracture Toughness Testing Specimens
Authors: Han Jae-Jun , Kim Yun-Jae , Ainsworth R. A.
Published: November 2014

Fracture toughness is an important quantity in structural integrity assessment of pressurised vessels and piping. This paper reports J resistance (J-R) curves for toughness test specimens and full-scale pipes with a circumferential crack in a carbon steel. Full-scale pipes with a circumferential crack subjected to four-point bending are investigated with single edge-notched-tension specimens, SE(T), under fixed grip and pin-loaded conditions and compact tension, C(T), fracture toughness test specimens. Finite element (FE) damage analyses based on a stress-modified fracture strain model are used to simulate ductile fracture. An element-size-dependent critical damage model is introduced and applied to the large-scale components. Fracture parameter J values are calculated using both experimental data and FE analysis. In the first part of this paper, experimental results performed by Battelle Memorial Institute are compared with results from FE simulations to gain confidence in the ductile fracture simulation. Subsequently, different types of fracture toughness tests and thickness variations are considered to address the effect of in-plane and out-of plane constraint, respectively. Also, pipe geometries and crack depth are varied systematically. In conclusion, the transferability of J-R curves from toughness test specimens to full-scale cracked pipes is discussed.
Summary of an ASME/DOT Project on Measurements of Fatigue Crack Growth Rate of Pipeline Steels
Authors: Slifka Andrew J. , Drexler Elizabeth S. , Amaro Robert L. , Lauria Damian S. , Hayden Louis E. , Stalheim Douglas G. , Chen Yaoshan
Published: November 2014

The National Institute of Standards and Technology has been testing pipeline steels for about 3 years to determine the fatigue crack growth rate in pressurized hydrogen gas; the project was sponsored by the Department of Transportation, and was conducted in close collaboration with ASME B31.12 Committee on Hydrogen Piping and Pipelines. Four steels were selected, two X52 and two X70 alloys. Other variables included hydrogen gas pressures of 5.5 MPa and 34 MPa, a load ratio, R, of 0.5, and cyclic loading frequencies of 1 Hz, 0.1 Hz, and a few tests at 0.01 Hz. Of particular interest to ASME and DOT was whether the X70 materials would exhibit higher fatigue crack growth rates than the X52 materials. API steels are designated based on yield strength and monotonic tensile tests have historically shown that loss of ductility correlates with increase in yield strength. The X70 materials performed on par with the X52 materials in fatigue. The test matrix, the overall set of data, implications for the future, and lessons learned during the 3-year extensive test program will be discussed.
Impact Resistance of Filament Wound Composite Pipes: A Parametric Study
Authors: Arif Abul Fazal M. , Malik M. Haris , Al-Omari A. S.
Published: November 2014

Filament wound composite pipes are being used in more and more applications. However, the impact behavior of these pipes is of particular importance in many applications. The sudden failure of these pipes under low velocity impact loads can be dangerous especially when the medium inside the pipe is hazardous or toxic in nature. The impact response of a composite laminate depends upon various factors such as thickness, stacking sequence and number of layers. The primary focus of this paper is parametric study of low velocity impact damage of CFRP and GFRP pipes under varying design parameters using finite element analysis. The simulation results are then used along with the ANN (Artificial Neural Networks) to fit a function to estimate the amount of absorbed energy.
On the Thermo-Mechanical Behaviour of SA508 Grade 4 Ferritic Steel
Authors: Abdolvand Hamidreza , Francis John A. , Azough Feridoon , Walsh Joanna N. , Gill Christopher M. , Withers Philip J.
Published: November 2014

The development of residual stresses in the Heat Affected Zone (HAZ) during welding of a ferritic steel can be critical to weld structural integrity. The Prior Austenite Grain Size (PAGS), the thermo-mechanical properties of the phases that develop during phase transformation, and the transformation strains are some of the key parameters that can alter residual stress development during welding. Understanding the trend in variation of these parameters is crucial for Finite Element (FE) modelling of residual stress development in weld. In this study, the effect of PAGS on the phase transformation in SA508 grade 4 was determined. For this purpose, samples were heated up to 900, 1050, 1250, and 1350°C and held for various time intervals to produce different austenite grain sizes. The measured austenite grain sizes were then used to fit parameters in an exponential equation implemented in an FE User MATerial subroutine (UMAT) for the modelling of welds. With performing various free dilatometry experiments, it is shown that the only phase that austenite transforms to upon cooling is martensite. In addition, the mechanical properties of as-received material, austenite, and martensite as a function of temperature were measured. Also, various uni-axial loads were applied during cooling cycles, and before the onset of phase transformations, to measure the evolution of transformation strain to generate an empirical formulation for numerical modelling.
Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 2 — Application of CCFS Method to the Multiply Supported Systems
Authors: Tai Koichi , Sasajima Keisuke , Fukushima Shunsuke , Takamura Noriyuki , Onishi Shigenobu
Published: November 2014

This paper provides a part of series of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. Paper is focused on the seismic evaluation method of the multiply supported systems, as the one of the design methodology adopted in the equipment and piping system of the seismic isolated nuclear power plant in Japan.

Many of the piping systems are multiply supported over different floor levels in the reactor building, and some of the piping systems are carried over to the adjacent building. Although Independent Support Motion (ISM) method has been widely applied in such a multiply supported seismic design of nuclear power plant, it is noted that the shortcoming of ignoring correlations between each excitations is frequently misleaded to the over-estimated design.

Application of Cross-oscillator, Cross-Floor response Spectrum (CCFS) method, proposed by A. Asfura and A. D. Kiureghian[1] shall be considered to be the excellent solution to the problems as mentioned above. So, we have introduced the algorithm of CCFS method to the FEM program.

The seismic responses of the benchmark model of multiply supported piping system are evaluated under various combination methods of ISM and CCFS, comparing to the exact solutions of Time History analysis method. As the result, it is demonstrated that the CCFS method shows excellent agreement to the responses of Time History analysis, and the CCFS method shall be one of the effective and practical design method of multiply supported systems.
Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 9 — Ultimate Properties of Full-Scale Lead Rubber Bearings Based on Breaking Test
Authors: Hiraki Takafumi , Nagata Seiji , Kanazawa Kenji , Imaoka Tetsuo , Nakayama Takashi , Umeki Yoshito , Jimbo Masakazu , Shimizu Hiroshi
Published: November 2014

This paper presents a part of “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities”. Ultimate behavior and failure modes of full-scale Lead Rubber Bearings (LRBs) of 1600mm diameter were described herein based on a series of the break tests which conducted on 11 LRBs to obtain a break surface. The shear break tests were monotonically conducted on 3 full-scale LRBs under various axial stresses. Then the monotonic tensile break tests were performed on 5 full-scale LRBs with or without constant offset shear strain. In addition, 3 half-scale LRBs of 800mm diameter were also tested to study the size effect and the ultimate shear behavior in significantly high compression. In the evaluation on the test results, the ultimate strain and stress were firstly summarized to define a break surface for the real-scale LRBs. Then the LRBs broken in the testing were carefully observed to evaluate their failure modes. It was found that the full-scale LRBs exhibited good seismic performance in horizontal ductility capacity and vertical load carrying capacity. It seems that the ultimate properties and the failure modes were basically less affected by the scale of the models.
Understanding the Impact of High-Magnitude Repair-Weld Residual Stresses on Ductile Crack Initiation and Growth: The STYLE Mock-Up 2 Large Scale Test
Authors: Smith Mike C. , Bourgeois Myriam , Arun Sutham , Do Son Cao , Kayser Yann , Smith David , Sherry Andrew
Published: November 2014

The STYLE EU Framework 7 project is examining the structural integrity of non-RPV components in reactor primary circuits. One of its focus areas is the impact of high magnitude weld residual stresses on the initiation and growth of cracks in austenitic stainless steels. A large scale fracture test has been performed on Mock-up 2, a butt-welded austenitic steel pipe containing a short, deep weld repair that induces weld residual stresses of yield magnitude over the length of repair. A through-thickness crack was introduced into the repair weld, and its behaviour under superimposed global bending load was investigated in a large scale fracture test. This paper describes the process of test design, the pre-test predictions made using the R6 defect assessment procedure, and the outcome of the test.
Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 7 — Breaking Test Plan and Development of Test Machine for Full-Scale Lead Rubber Bearings
Authors: Kosugi Shinji , Kanazawa Kenji , Tsudome Hidekazu , Sato Nobuhisa , Jimbo Masakazu , Sato Kunihiko , Umeki Yoshito , Imaoka Tetsuo
Published: November 2014

This paper is a part of the series “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities.” This part presents a break test plan and development of a test machine for a full-scale lead rubber bearing (LRB). Application of seismic base-isolation systems using LRBs of 1600 mm in diameter to reactor building has been considered for the purpose of enhancing seismic safety. It is important to obtain the ultimate properties of isolators in order to estimate the seismic safety margin of seismic base-isolated structures against a beyond design-basis earthquake events. Recent studies reveal that the scaled effect appears on the ultimate properties of seismic rubber bearings. However, because of the limitation of the loading capabilities of loading machines, the ultimate property of such a large scale LRBs has not been confirmed.

In this study, the break tests for LRBs of 1600 mm in diameter is planned on the basis of estimation that refers to previous studies on break tests for small-scale LRBs and natural rubber bearings. The world-largest class test machine is designed and constructed to conduct static break tests for the full-scale LRBs. Furthermore, the performance of the test machine is evaluated from test results including those for break tests.
Fracture Toughness in the Ductile-Brittle Transition and Thermal Ageing Behavior of Decarburized Heat Affected Zone of Alloy 52 Dissimilar Metal Welds of Nuclear Components
Authors: Joly Pierre , Yescas Miguel , Keim Elisabeth
Published: November 2014

Dissimilar metal welds (DMW) are used in nuclear power plants between the nozzles of main components in low alloy steel and stainless steel pipes, or safe-ends connected to the main coolant line pipes. AREVA proposes for EPR™ an improved design of DMW involving narrow gap welding without buttering between the low alloy steel nozzles and the stainless steel safe-ends, and the use of a corrosion resistant weld filler metal (Alloy 52).

AREVA performed a thorough characterization of this type of welds, which shows a particular microstructure close to the fusion line between the low alloy steel and the nickel base alloy, where the heat affected zone of the low alloy steel is decarburized.

This paper presents results of fracture toughness tests performed with the crack tip located in this area, in the ductile to brittle transition in the as post-welded heat treated condition and after thermal ageing. The results show an excellent fracture toughness behavior of this particular area, compared to that of low alloy steel parent metal.
Clearance of Bulk Materials From Decommissioning Projects: Regulatory and Cost Issues
Authors: Devgun J. , Demoss D. , Raupp S.
Published: November 2014

Decommissioning of nuclear facilities requires management of bulk materials on a large scale. Clearance (also called “free release”) is an essential part of material management and is necessary to reduce the amount of radioactive waste generated. Cleared materials can either be recycled for other use or disposed of as conventional waste. While guidance for decommissioning of reactors in the United States is well established by the Nuclear Regulatory Commission (NRC) and License Termination criteria as codified in 10 CFR 20 Subpart E are applied, there is no specific criteria or detailed guidance for the clearance of solid materials. The issue has been around for over three decades. The approach taken by the NRC is still on a case by case basis.

In contrast, the guidance at the international scene is more detailed and clearance of solid materials (for recycling or disposition) from the decommissioning of nuclear facilities is regularly practiced in European countries (such as, Sweden, Belgium and Germany). The cost of disposal of bulk materials from decommissioning, such as demolition debris that may or may not be contaminated, as radioactive waste is prohibitive. A path to free release under some criteria is necessary. It is not a question of radiological safety since there is consensus on extremely low dose criteria and these are accepted at the international level. It is rather, an issue of regulatory void in the United States where clarity and explicit guidance at the national level is pending.

This paper provides an overview of national and international guidance and regulatory developments for the clearance of solid materials from nuclear decommissioning projects including dose risk based methodologies. It will summarize the cost dimension of the issue and the field experience gained from the Big Rock Point decommissioning project.