bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Flow Channel Geometry on Thermomechanical Performance of Printed Circuit Heat Exchanger (PCHE)
Authors: Jiragoontansiri Witiwat , Woravisuttsarakul Teerapat , Sae-pueng Rinrada , Sukjai Yanin , Shirvan Koroush
Published: October 2021

Climate change has garnered attention of communities world-wide. The carbon-free thermal energy systems such as nuclear benefit from compact and highly efficient heat exchanger technologies. The plate-type compact heat exchangers such as the Printed Circuit Heat Exchanger (PCHE) holds promise to fulfil these requirements. The chemical etching and diffusion bonding technology expands PCHE application for several different nuclear technologies. This work presents the thermal-hydraulic and structural analysis of PCHE for molten salt application with thermal energy storage. In this study, three different types of geometry are chosen for the analysis i.e., the zigzag channel type, the airfoil fin type, and the slotted fin type. For the working fluid, FLiBe (Li2BeF4) and Solar Salt (60% NaNO3 and 40% KNO3) are chosen for hot side and cold side respectively. Titanium grade 5 is chosen as the structural material. The study is conducted by Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) analysis. The thermomechanical behavior including pressure drop, fluid temperature, velocity profile, stress, and deformation of the flow channel were considered in this work. From the results, the zigzag channel geometry gives the best thermal hydraulic performance in terms of heat transfer and pressure drop. The structural analysis shows that the stress intensity of all three geometries can exceed the maximum allowable stress (MAS) under certain conditions. Overall, the zigzag channel PCHE is still the most suitable geometry for this application.
Improvement of Conversion Ratio of Thorium Fuel in LWR by Adding Neutron Absorber
Authors: Takeishi Taichi , Takeda Satoshi , Kitada Takanori
Published: October 2021

The reproduction factor of Th232 is high in the thermal energy range and there is a possibility to achieve the breeding in LWRs. However, it is necessary to improve the conversion ratio since the breeding is difficult in LWRs. The conversion ratio can be improved by suppressing capture rate of Pa233 and by promoting capture rate of Th232. In addition, these capture rates can be modified by adding neutron absorber. Therefore, the neutron absorber is focused for improving the conversion ratio in this study.

The high resonance peaks of Pa233 capture cross section exist around 1∼100 eV. The resonance peaks of Th232 are higher than 10 eV. Thus, when the 1∼10 eV neutrons are suppressed in the fuel, the Pa233 resonance capture reaction is suppressed and the Th232 resonance capture reaction is promoted by neutron spectrum hardening. Therefore, six neutron absorbers that have high capture cross section peaks at 1∼10 eV were selected. The PWR pin cell calculations were carried out by Monte Carlo code MVP. The fuels are composed of a base material and an absorber. The base material is an oxidized fuel composed of U233(10 wt%), Th232(89.95 wt%), and Pa233(0.05 wt%). The amount of neutron absorber was adjusted so that the infinite multiplication factor becomes 1.33.

The impact of adding neutron absorber on the reaction rate was evaluated. As the result, the hardening of the neutron spectrum leads increase of the capture rate of Pa233, and the capture rate of Th232 in the epithermal energy range is increased. The change of capture rate of Th232 is greater than that of Pa232. Therefore, the conversion ratio is found to be improved by adding neutron absorber.
Nonlinear Low Bias Current Control for Magnetic Bearing System Using Active Disturbance Rejection Technology
Authors: Yao Yichen , Su Yixin , Yu Suyuan
Published: October 2021

Magnetic bearing is widely used in helium-turbine circle of the high temperature gas-cooled reactor and many other highspeed rotating machinery because of its unique advantages in vibration and noise reduction. However, the power consumption of magnetic bearing increases its cost of use. Moreover, the design of magnetic bearing controller relies on accurate system modeling. All these restrict the industrial application of magnetic bearings.

Based on the structure of the eight-pole magnetic bearing and its corresponding traditional decentralized differential PID control strategy, this paper proposes a magnetic bearing control framework including expected bearing force realization control strategy and centralized control strategy. Under this framework, a nonlinear low bias current control method for magnetic bearing system is given. Afterwards, an active disturbance rejection controller based on low(zero) bias current is proposed to compensate the gyroscopic disturbance and modeling uncertainty of the system. The controller can keep small loss of magnetic bearing and have good stability. It has a frame of active disturbance rejection control (ADRC) and its compensation performance is analyzed.

In order to verify the effectiveness of the controller, a corresponding experimental verification is carried out on the test rig. The results show that the control strategy is effective.
Evaluation of Serpent Capabilities for Hyperfidelity Depletion of Pebble Bed Cores
Authors: Robert Yves , Fratoni Massimiliano
Published: October 2021

Accurate burnup calculation in pebble bed reactor cores is today necessary but challenging. The continuous advancement in computing capabilities make the use of Monte Carlo transport codes possible to efficiently study individual pebbles depletion without making strong assumptions. The purpose is to eliminate unnecessary typical assumptions made in existing codes, while being flexible and suitable for commonly available computing machines.

Among the available codes, Serpent 2 provides extremely useful tools to make pebble beds modeling and simulation efficient. The explicit stochastic geometry definition handles irregular pebble beds with comparable performances to regular lattices. Optimization modes controlling the use of unionized energy grids, cross-sections pre-calculation and flux calculation through spectrum collapse or direct tally lead to high flexibility and optimal memory usage while limiting calculation time. Automated burnable materials division is a useful tool to lower the memory requirements while quickly generating the geometry and materials. Finally, parallelization and domain decomposition allow for decreasing unreasonable memory constraints for large cores.

This work thus explores the possibilities of Serpent 2 when applying depletion in pebble beds, compares the optimization modes and quantifies the simulation time and memory usage depending on the conditions of the calculation. Overall, the results show that Serpent 2 is well adapted to the use of small to large cores calculations with commonly available resources.
Evaluation of Interface Stresses and Cladding-Cladding Delamination Failures In U-Mo Fuel Plates
Authors: Ozaltun Hakan
Published: October 2021

Monolithic fuel is a candidate fuel form for the conversion of high-performance research reactors. This plate-type fuel consists of a high-density, U-Mo alloy-based fuel in a monolithic form that is sandwiched between zirconium diffusion barriers and encapsulated in an aluminum cladding. To qualify this fuel system, the program must demonstrate that the fuel meets the safety standards, has a predictable behavior, and performs well in a reactor. Although many plates have shown satisfactory thermo-mechanical performance in reactor, a small number of experimental plates exhibited failures, rendering performance of these plates unacceptable. Post-irradiation examinations of failed plates have revealed that various failures modes are present, including pillowing, blistering, buckling, warping, delamination, fracture, rupture, oxide spallation, etc. Previous studies have implied that such various operational and loading conditions could generate a complex stress-strain state, facilitating distinct failure modes that could impact the structural integrity. To understand such various failure modes, a comprehensive set of studies focusing on failure modes is being performed. As a part of these studies, this work studies the cladding-cladding separation failures that were observed in some of previous irradiation tests. To understand the root cause of cladding separation failures, selected plates from previous irradiation experiments were simulated under comparable operational conditions. Stress-strain state of the plates at the interface were examined. The results were comparatively evaluated to understand possible effects of stress state of the bond-line on delamination failures. This paper presents these findings, discusses such failure modes, and examines the influence of various factors on previously observed cladding delamination failures.
Study on the Off-Site Consequence Evaluation of NPP Severe Accident Based on JRODOS Platform
Authors: Wang Xuan , Guo Li , Lin Xiujing , Pu Xiang , Du Fenglei , Huang Xiaodong , Xiong Xiaowei , Wang Bo
Published: October 2021

JRODOS (Java Real-time On-line Decision Support) is currently being developed by the German KIT company and promoted globally. Because of its good user visual interface and efficient calculation and analysis functions, it has been widely used in nuclear power plants accident consequences assessment. In this paper, the MVK data set is used to verify the simulation accuracy of the RIMPUFF atmospheric dispersion model in the JRODOS system. The verification conclusion shows that the calculation results of RIMPUFF are significantly better than other calculation models. This paper presents a case study of CAP1400 severe accidents consequence assessment in one nuclear power plant base on the JRODOS platform, the IC severe accident (SA) was chosen to give an example for the rapid assessment of nuclear accidents. The research in this paper shows that for the CAP1400 nuclear SA, the I-132, I-135, I-133 and I-131 are the main radionuclide. Under the selected typhoon weather conditions in this paper, the maximum dose rate within 48 hours is only 1.79E−03mSv/h, the maximum individual dose is only 3.06mSv, the impact area is generally within 6km downwind. Under the selected typhoon weather conditions, the plume can basically reach the monitoring point in the downwind direction within 1h, while for other monitoring points, it will take 17h to reach the points, this is mainly affected by the wind direction. The research results of this paper can be used for rapid assessment of nuclear accidents in nuclear power plants and formation of evaluation manuals, which can better guide emergency or conventional emergency drills.
Failure Assessment of Gas Pipeline Based on Fuzzy Bayesian Network and AHP
Authors: Yu Qiaoyan , Hou Lei , Li Yanhao , Cai Chong
Published: October 2021

The long-distance pipeline is the crucial connection for gas producing area and demand location. It may be damaged due to the impact of various factors, resulting in the leakage of gas. Reliable failure assessment can avoid the occurrence of pipeline leakage and reduce losses effectively. Because of the lack of pipeline historical data and the impact of various uncertainties, this paper adopts the fuzzy Bayesian network (BN) and analytical hierarchy process (AHP) method with expert heuristic to analyze the probability of gas pipeline failure. In the proposed model, an AHP is developed to identify the factors affecting pipeline failure by literature, database and expert questionnaire. Their prior probabilities and conditional probabilities are analyzed with expert opinion and fuzzy theory in the absence of historical data. By using the prediction and diagnosis techniques of BN, the failure probability of gas pipeline is achieved and the critical events are identified. The model is applied to an underwater natural gas pipeline to prove the feasibility and rationality of the model. The results indicate that the proposed model can provide guidance to pipeline managers for the safety of gas pipelines and a technical guide for decision makers with pipeline failure.
Development and Implementation of an In-Situ Repair Method for ISFSI Canisters
Authors: Williams Allen , Johnson Kyle , Beard Jamie , Canfield Stephen , Stephenson Jerry
Published: October 2021

A remote, robotic method of mitigating damage to an Independent Spent Fuel Storage Installation (ISFSI) canister has been developed and tested. It is currently ready for implementation if required for a vertical canister system and will be ready for implementation in 2020 for a horizontal canister system. The development was in response to State of California directives to be ready and able to implement a canister repair technology if needed at San Onofre Nuclear Generating Station.

The method was developed by miniaturizing existing cold spray technology and combining it with robotics previously used on site. The Metallic Overlay method (also known as ‘Cold Spray’) has been tested and accepted for use at San Onofre.

The testing involved the miniaturization of the Metallic Overlay Equipment, testing of several metals which were considered for use, the decision process for the down-selecting of the chosen material, the combining of mitigation tooling and robotics, and the final testing and qualification of the process. This paper will also discuss the details needed to implement on site.

This paper will focus on the development, testing and implementation of the miniature robotic platform and the metallic overlay equipment/process. The background leading to the development of the overlay process will be provided, and will note the tie to (in development) Code Case N-860[1], which would indicate the conditions that would occur to direct the site towards implementation of the metallic overlay process.

The process has been developed in advance of a specific need. It is a proactive action intended to allow efficient response in the event mitigation is required at San Onofre.
Welding Tube to Tubesheet Joints for Corrosion Resisting Applications
Authors: Sippy Haresh K.
Published: October 2021

The work in this paper relates to an improved tube to tubesheet joint in a shell and tube type heat exchanger that have dissimilar metallurgies of tube and tubesheet. This improved tube to tubesheet joint configuration will not only impart reliability and strength to the mechanical integrity of the joint but also reduce the costs of the manufacturing without compromising the functional performance of the exchanger. In a shell and tube heat exchanger, generally the material of tubes may be similar to the tubesheet or of a higher corrosion resistant grade in comparison to that of the tubesheet. Conventionally, shell and tube heat exchangers that involve dissimilar materials of tube and tubesheet are either:

i. Tubes welded directly to the tubesheet with matching grade weld metal

or

ii. The tubesheets are clad / weld overlaid with the higher corrosion resistant material or material similar to the tube material

For purpose of this study, we have considered the material of tube as stainless steel type 304L and that of tubesheet as carbon steel.

The above case 1 wherein the SS-304L tubes are directly welded to the CS tubesheet, may have the following advantages:

i. Manufacturing time is less.

ii. Tubes are attached to the base metal and hence free from defects of weld overlay or cladding, if any.

In case 2, wherein the SS-304L tubes are welded to the SS-304L clad / weld overlaid portion of tubesheet, the advantages are:

i. Welding takes place between two austenitic stainless steel grades, hence PWHT is not required.

ii. The tube to tubesheet joint and adjacent material is of austenitic stainless steel grade, hence has better corrosion resistance.

The main objective of the work done and reported in this paper is to combine the advantages of the above two cases thereby:

i. Reducing the cost of manufacturing

ii. Increasing the mechanical reliability of the tube to tubesheet joint.

Extensive trials were carried out on sample tube to tube sheet joints, the results and conclusions of which are reported in this paper.
A Discussion of Strength Reduction Factor Development for Thermal Aging Effect on Nuclear Structural Alloys
Authors: Ren Weiju
Published: October 2021

In consideration of structural alloy property deterioration during long-term exposure to elevated temperatures, the yield and ultimate tensile strength reduction factors are provided in the Boiler and Pressure Vessel Code Section III for nuclear reactor component design and operation analysis. Because the Gen IV reactor requirement of 40 ∼ 60 years of service life makes it difficult to acquire such long exposure test data for developing the reduction factors, they must be derived from test data with relatively short exposure by predictive methods considered to be reasonably reliable. A novel approach with a physically-based model has recently been proposed for application to development of reduction factors for 9Cr-1Mo-V. In the model, contributors to the tensile strength are first identified and related to definite microstructural features of the alloy, then some physically-based methods are employed to simulate the microstructural evolution, and finally the model is assembled with test-data-calibrated parameters to generate the yield and ultimate tensile strength reduction factors covering elevated temperature exposure for up to 57 years. The approach is undoubtedly a trailblazing development that will, if proven reliable, lead to a paradigm shift in predicting thermal aging behavior of many other alloys. Its debut application to Section III, however, concerns nuclear safety and naturally warrants objective, impartial, and thorough technical scrutiny. In the present paper, the novel and conventional approaches are discussed. Necessary improvements to the novel approach are recommended for its application to nuclear structural component design and analysis, and for its potential expanded use to other alloys.
Vibration Transmission Characteristics of Periodic Composite Pipeline Considering Friction Coupling Effect
Authors: Zeng Qingna , Wang Donghui , Zang Fenggang , Zhang Yixiong
Published: October 2021

In this paper, transmission characteristic of periodic composite pipeline is investigated for axial vibration, focusing on friction coupling effect. A novel transfer matrix method is developed to calculate band gap structures (BGs) with the consideration of different forms of viscous friction. Frequency response function for finite periods is obtained and shows good consistency with BGs for infinite periods. The energy dissipation caused by viscous friction exists in the entire frequency range, as friction coupling is always distributed along the pipe element. Meanwhile, the attenuation intensity is relatively small compared with that induced by Bragg scattering mechanism. Therefore, viscous friction is not affecting the overall trend of BGs, only exhibiting certain attenuation in pass band frequency range. The effect of kinematic viscous coefficients on axial BGs are systematically examined in different friction models. Attenuation intensity goes up with increasing kinematic viscous coefficients, in addition, energy dissipation caused by frequency dependent friction model is generally higher than that of steady state friction condition. Moreover, frictional dissipation shows more sensitivity to high frequency. The research in this paper enriches fluid structure interaction theory of pipe element, which is also expected to be helpful in controlling the dynamical behaviors of pipeline system conveying fluid.
Constraint Effect on Fracture in Ductile-Brittle Transition Temperature Region
Authors: Hojo Kiminobu , Hirota Takatoshi , Nagoshi Yasuto , Fukahori Takuya , Sakima Kimihisa , Ohata Mitsuru , Minami Fumiyoshi
Published: October 2021

Bend fracture tests using flat plate specimens of 50mm thickness with a surface crack, 1TC(T), and SE(B) specimens of low alloy steel were performed in the ductile-brittle transition temperature (DBTT) region. Two types of SE(B) specimen, a/W = 0.1 and 0.5, were used. The fracture tests were conducted at −120°C and −80°C aiming at fracture mode of complete cleavage fracture at lower temperature and cleavage fracture after ductile crack growth at higher temperature. At −120°C, all specimens showed complete cleavage fracture. The shape factor of the Beremin model of the C(T) specimen or SE(B) specimen with a deep crack were determined by using each type of specimen at −80°C. Also, Toughness Scaling Model (TSM) was applied for determination of the Weibull parameters using two types of SE(B) specimens at −80°C. The GTN parameters were determined from fracture data of 1TC(T) specimen at the room temperature. The prediction analyses of the flat plate specimens for −120°C and −80°C were carried out using the Beremin model and the coupled model with the GTN model. The measured KJ of the tests for the flat plates were compared with the predicted KJ of 5% lower bound curve and 95% upper bound for the flat plate specimen which were deduced by the SE(B) specimen’s test data. Transferability from the test results of laboratory test specimens to that of a large specimen with low constraint, which was similar to the actual structure, was investigated. The temperature independency of the Weibull parameter m of the Beremin model was also confirmed.
Causal Relationship Extraction of LNG Unloading System Under Abnormal Conditions Based on Bidirectional LSTM Network
Authors: Xu Kangkai , Hu Jinqiu , Dong Shaohua , Feng Lingan
Published: October 2021

LNG unloading system plays an important role in the transport and storage medium of the process. Once the unloading system occurs exceptions, such as pressure fluctuations, uneven pre-cooling and unexpected temperature rises, these phenomena will affect the safe operation of LNG terminals. In the process of LNG unloading, there is a coupling relationship between the changing of pressure, flow rate, temperature and other parameters. The accurate cause and development direction of abnormal working conditions are conducive to the safe operation and maintenance of the unloading system. According to the accident statistics of 38 LNG receiving stations and peak shaving stations by The LNG International Importer’s Group (GIIGNL), the accident rate of the unloading system was 27%. Therefore, the realization of the extraction and identification of the causality of abnormal working conditions of the LNG unloading system has great significance for the traceability and early warning of the accident.

As a crucial type of relationship, causality plays a key role in many fields such as relational reasoning and so on. Therefore, extracting causality is a basic task in text mining. At present, in China, the analysis of abnormal working conditions of LNG unloading system adopts the methods of HAZOP and FMEA, and a large amount of causality is contained in the text data. To solve the problem of automatically extracting the causality of the LNG unloading system text data, this paper adopts the method of sequence labeling to extract the causal relationship entity and determine its direction. Sequence to sequence (Seq2Seq) architecture and bidirectional long short memory network (Bi-LSTM) are used to train input word vectors and predict the development of causal relationship. In order to solve the problem of unclear objects and inaccurate predictions caused by redundant causal nodes, attention mechanism is applied, and the prediction accuracy reaches 95.23%. In the sensitivity analysis, the recall rate and the granularity of causal relationship information perform well, which indicates that the algorithm has generalization and applicability in the establishment of the causal knowledge base of abnormal conditions in the unloading system.
Interlaboratory Study of All-Weld-Metal Strip Tensile Testing of Narrow Groove Pipeline Girth Welds
Authors: Park Dong-Yeob , Gravel Jean-Philippe , Xu Su , Gianetto James A. , Crapps Justin M. , Lazor Robert , Quintana Marie A.
Published: October 2021

The informative section of AWS B4.0-Annex D offers a recommended practice for all-weld-metal tensile testing of narrow groove pipeline girth welds, sampling a higher proportion of weld metal than is possible with more traditional testing practices. An interlaboratory study (ILS) program was conducted to examine the applicability and practicability of AWS B4.0-Annex D. Program participants represented a broad range of interests across industry, government, and academia. Precision statistics of the test method were assessed according to ASTM E691 and E177. This paper includes results of the assessments. The results from the ILS demonstrate that AWS B4.0-Annex D is repeatable and reproducible for determination of tensile properties of narrow groove pipeline girth welds.
Development of Guideline on Seismic Fragility Evaluation for Aged Piping
Authors: Yamaguchi Yoshihito , Katsuyama Jinya , Masaki Koichi , Li Yinsheng
Published: October 2021

The seismic probabilistic risk assessment is an important methodology to evaluate the seismic safety of nuclear power plants. In this assessment, the core damage frequency is evaluated from the seismic hazard, seismic fragilities, and accident sequence. Regarding the seismic fragility evaluation, the probabilistic fracture mechanics can be applied as a useful evaluation technique for aged piping systems with crack or wall thinning due to the age-related degradation mechanisms. In this study, to advance seismic probabilistic risk assessment methodology of nuclear power plants that have been in operation for a long time, a guideline on the seismic fragility evaluation of the typical aged piping systems of nuclear power plants has been developed considering the age-related degradation mechanisms. This paper provides an outline of the guideline and several examples of seismic fragility evaluation based on the guideline and utilizing the probabilistic fracture mechanics analysis code.
Effects of a Single Overload on Fatigue Crack Growth of Type 316 Stainless Steel
Authors: Miyoshi Koji , Kamaya Masayuki
Published: October 2021

The effect of a single overload on the fatigue crack growth rate was investigated for Type 316 stainless steel. Fatigue crack growth tests were conducted by controlling strain and load. Tensile and compressive overloads were applied during constant amplitude cycling. The overload ratio, which was defined as the ratio of overload size to baseline constant amplitude, was also changed. The constant amplitude tests were conducted at the strain or the stress ratio of −1.0 which was defined as the ratio of the minimum value to the maximum value. The crack opening point was obtained by the unloading elastic compliance method. The crack growth rate increased after the single compressive overload. The accelerating rate increased with the overload ratio. In contrast, not only the acceleration but also the retardation of the crack growth rate was observed for some tensile overload cases. The crack growth rate increased for relatively small tensile overload cases and decreased for relatively large tensile overload cases. The change in the crack opening level was examined. The crack growth rates after tensile and compressive single overloads correlated with the effective strain and stress intensity factor ranges both for load and strain controlling modes.
Explosive Testing of High-Pressure Vessel for Proton Imaging of Shock Physics Experiments
Authors: Spernjak Dusan , Cardon Devin , Scarafiotti Jesse , Biel Morgan , Gibson Joshem , Fehlmann Kevin , Lakey Matthew , Romero Christopher , Bustos Gerald , Marr-Lyon Mark , Llobet Anna
Published: October 2021

We present the results of explosive testing of an Inner Pressure Confinement Vessel (IPCV). The IPCV is explosively-loaded high-pressure vessel which is a part of the containment system to facilitate proton imaging of small-scale shock physics experiments at Los Alamos National Laboratory (LANL). The detonation of high explosive (HE) drives material to extreme loading conditions, which are imaged using a proton beam and an imaging system. The IPCV needs to satisfy the ASME Boiler and Pressure Vessel Code, Section VIII, Division 3, Code Case 2564, while allowing for maximum resolution of proton radiography.

The IPCV contains an Experimental Physics Package (EPP), fragment mitigation assembly, and radiographic windows. To achieve the optimal imaging resolution, the radiographic windows need to be very thin, located extremely close to the HE, and made of low-attenuating material such as Beryllium. While the IPCV is designed to a relatively small HE amount of 30 g TNT equivalent, the radiographic window is located only a few cm away from the HE, which is unique to this specialized high-pressure vessel. Fragment mitigation is critical to protecting radiographic windows from any fragments to allow the IPCV to maintain the pressure boundary before and after the explosive experiment. This shielding contains two layers: Boron carbide (B4C) facing the HE and Dyneema (cross plied composite layers made of ultra-high molecular weight polyethylene) facing the window. The B4C plate serves to break up and dull fragments while Dyneema catches fragments and prevents them from contacting the radiographic windows. Design development of the fragment mitigation assembly and attachment was informed by several series of explosive tests at LANL. The tests also addressed the sealing function of vessel covers, gas lines, and isolation valves before and after an explosive experiment.
Microstructure Control and Optimization of Centrifugal Casting Furnace Tube HP40 Alloys Based on Cafe Model
Authors: Xiang S. L. , Chen T. , Fan Z. C. , Lian X. M. , Chen X. D.
Published: October 2021

With the development of Materials Genome Initiative (MGI), Integrated Computational Materials Engineering (ICME) has emerged as an important tool in the research of materials science. For the furnace tube alloys used in ethylene pyrolysis facilities, the high-temperature mechanical properties highly depend on their microstructure, especially the grain morphology. In this work, a cellular automaton finite element (CAFE) model simulated grain structure in solidification processes is applied. In the CAFE model, the density of grains formed at any undercooling and the growth kinetics of the dendrite tip are deduced by Gaussian distributions and Kurz-Giovanola-Trivedi (KGT) theory, respectively. A method of two-stage modeling for the cylindrical furnace tube is proposed, based on the characteristics of alloy melt flow in the horizontal centrifugal casting process. By the control of different parameters in the solidification process, the various microstructure morphologies of centrifugal casting HP40 alloys are obtained and verified with the experimental observations and theoretical analysis. As a consequence, the microstructural prediction model of centrifugal casting HP40 alloys is optimized. The result shows that the desired full columnar grain morphology of HP40 alloys can be realized at the pouring temperature of 1620 °C and the revolving speed of 3100 rpm. This research reveals the potential application of the CAFE approach in microstructure control and optimization of furnace tube alloys.
Shake Table Testing for a Multi-Component Prototype Industrial Plant: Input and System Modelling Issues
Authors: Nardin Chiara , Bursi Oreste S. , Paolacci Fabrizio , Quinci Gianluca , Lanese Igor , Pavese Alberto
Published: October 2021

Recent destructive earthquakes in China (Sichuan, 2008 and Yushu, 2010), Japan (Tohoku, 2011) and Italy (Emilia, 2012) highlighted the social and the political consequences of seismic risk due especially to industrial facilities. More precisely, critical interactions between the supporting structure and process components reveal to be extremely vulnerable in a seismic scenario and capable to lead serious damage of process equipment and potential release of hazardous substances. This latter circumstance, underestimated by current codes, in addition to loss of production, pose a serious danger to humans and the surrounding environment. Based on these premises, the SPIF project — Seismic Performance of Multi-Component Systems in Special Risk Industrial Facilities — was proposed within the framework of the European H2020 - SERA funding scheme. In greater detail, the goal of the project is the investigation of both the seismic behavior and the dynamic interactions of a representative industrial substructure equipped with complex process technology by means of shaking table tests. A full-scale mock-up composed by two single-bay moment resisting frames with three floors equipped with tanks, flanges, pipes, cabinet etc. was built and tested using a unidirectional shaking table activated with several earthquake levels. More precisely, the salient features investigated by shaking table testing are: i) the interaction between a primary moment resisting frame steel structure and secondary process components that influence the performance of the whole system; ii) input and system modelling capable to faithfully reproduce the seismic response of SPIF tested structure. The comprehensive testing campaign demonstrated a clear dynamic interaction between the primary steel structure and secondary process units that emphasizes the need of further investigations and studies.
Acceleration and Displacement Response of Base Isolation System With Friction Subjected to Random Vibration
Authors: Aoki Shigeru , Kurita Katsumi
Published: October 2021

Various types of devices have been developed to reduce seismic response of the mechanical systems. Base isolation system is one of them. In such devices, friction characteristic is used. The authors have developed a base isolation system with friction for relatively small mechanical system. In ordinary case, response of mechanical system decreases with the increase of friction coefficient. However, in the experiment to examine the effectiveness of base isolation system, it is found that acceleration response takes minimum value at some friction coefficient. In this paper, experimental results are examined using a simplified model. As earthquake excitations, some types of random vibration are used. Responses of the mechanical system are obtained from moment equations using the equivalent linearization method. It is demonstrated that acceleration response takes minimum value at some friction coefficient in some conditions.
High Temperature Aged Leakage Relaxation Screening Tests on Confined Flexible Graphite Gaskets
Authors: Bouzid Abdel-Hakim , Das Shubhra Kanti
Published: October 2021

Flexible graphite-based gaskets are used extensively in high-temperature applications as a replacement of asbestos based gaskets. The effect of aging and temperature exposure of flexible graphite sheet gaskets was the subject of a previous work [1,2], however, the effect when flexible graphite is in a confined gasket configuration is not known.

This study outlines the performance evaluation of the elevated temperature behavior of flexible graphite-based gaskets under a confined configuration and exposed over a long period employing HALR (High temperature Aged Leakage Relaxation) fixture. This ARLA-like fixture can retain the mechanical feature of the ATRS/HATR while allowing the cold leakage rate and weight loss measurement. Four different confined gasket configurations, namely corrugated metal, spiral wound, kammprofile and double jacketed, are evaluated within a temperature range of (427 to 649 °C) 800 to 1200 °F and exposure time of 2500 hours. Graphite weight loss, gasket thickness change, leakage and tightness parameter, creep and relaxation measurements were taken at regular intervals for each gasket style. To better understand the aging process, these critical mechanical and leakage properties are scrutinized; the degradation process related to mainly graphite oxidation is further discussed, and a conclusion is drawn.
Assessment of Dynamic High Momentum Slug Loads on Piping Following STHE Tube Rupture
Authors: Weyer Robert
Published: October 2021

Transient fluid loads in process piping have gained renewed focus recently with the design and construction of many LNG plants. The case of the shockwave (waterhammer) in piping following the rupture of a tube in a STHE has been well studied. Less attention has been paid to the high momentum slug flow which can occur when liquid slugs are accelerated in the piping by the gas.

This paper will examine some of the practical considerations for assessing the dynamic loads resulting from this high momentum slug flow. A method to obtain the force vector for any 3-dimensional change in direction will be presented. The use of DLFs for loads where a detailed time history profile is available will be discussed. The possibility of taking credit for simultaneously acting forces will be investigated.

The applicability of the B31.3 allowable stress for occasional loads will be examined and compared against advanced finite element models using shell elements.
Design Considerations for Half-Pipe Jackets Operating Under Vacuum Conditions
Authors: Mathkar Ameya , Gopalakrishnan Shyam , Pathre Sujay S.
Published: October 2021

Pressure vessel is defined as an equipment having pressure differential between inside and outside. The pressure is accompanied with suitable temperature of the fluid. Based on the process requirement, the temperature within the pressure vessel is maintained. The temperature can be controlled by application of heat from direct or indirect source. Half-pipe jacket or limpet coil is one of the methods to maintain the temperature of fluid in the pressure vessel. The nonmandatory Appendix EE of ASME Sec. VIII, Div. 1 and Para. 4.11.6 of Part 4 of ASME Sec. VIII, Div. 2 provide the rules to design the half-pipe jackets constructed of size NPS 2, NPS 3 and NPS 4. Both ASME Sec. VIII, Div. 1 and Div. 2 stipulates rules for calculation of minimum thickness of half-pipe jacket and the maximum permissible pressure in the half-pipe jacket.

Certain condition of applicability is provided in both ASME Sec. VIII, Div. 1 and Div. 2 to use the calculation procedure for design of half-pipe jackets.

1. There is positive pressure inside the shell/head.

2. There is positive pressure inside the half-pipe jacket.

Under certain situations, the above conditions may partially be met. e.g. The equipment may be under full vacuum with positive pressure in half-pipe jacket. Also, possibility could exist that the equipment is having some positive pressure while the half-pipe jacket may be experiencing vacuum simultaneously.

Such designs are not covered under the rules provided in nonmandatory appendix EE of ASME Sec. VIII, Div. 1 as well as in Part 4 of ASME Sec. VIII, Div. 2 and the users must demonstrate compliance by meeting U-2(g) for ASME Sec. VIII, Div. 1 and by designing in accordance with Part 5 for ASME Sec. VIII, Div. 2. For such design condition, elastic buckling and plastic deformation shall be evaluated for the entire equipment.

Unlike ASME Sec. VIII, Div. 1 and Div. 2, other international Codes like PD5500 and EN 13445 in addition to providing the rules for evaluating half-pipe jacket or limpet coils also states that when the equipment is subject to vacuum, the half-pipe jacket may be considered to contribute as stiffeners.

This paper is an attempt to find out the means to design the equipment with half-pipe jacket or limpet for which the conditions specified in ASME Sec. VIII, Div. 1 and Div. 2 are not satisfied.
Statistical Analysis of Localized Corrosion in Service Water Piping
Authors: Parker S. , Roukema A. , Patten Y.
Published: October 2021

Degradation found in carbon steel Service Water piping is typically characterized as localized corrosion or “pitting.” Localized corrosion or pitting is identified as small sections of thinning that deviate from the average wall thickness. In its most basic sense, a pit is simply a geometric entity that is abrupt and distinct that can range in size, extent, and density throughout the system. This raises the question of how one defines a pit and what geometric characteristics can be used to create this definition.

Research has been conducted to help provide answers to this question through detailed study of wall thickness examination results on operating service water piping in a nuclear power plant. This analysis has determined that the primary geometric characteristics are the depth-to-extent ratio, the extents of thinning, the shape of the pit, and the distance between adjacent pits. Statistical distributions of these characteristics for the evaluated data sets were developed to understand the overall trends of the pitting. With further research, the results of this evaluation can be used to extrapolate these trends of pitting characteristics, with high statistical confidence, to sections of service water piping that have little to no detailed non-destructive examination data. The objective of this paper is to present the preliminary findings of the statistical study on “pitting” and provide a set of geometric characteristics that best define a pit.
Simplified Criteria With Reduced Testing Effort for Selecting Clad Materials for High Temperature Reactor Structural Components
Authors: Barua B. , Jetter R. I. , Messner M. C. , Sham T.-L.
Published: October 2021

Current Class A materials qualified in the ASME Section III, Division 5 rules for high temperature nuclear service do not have optimal resistant to salt corrosion in fluoride salt-cooled high temperature reactor and molten fluoride salt reactor. This limitation can be overcome by using cladded components — overlay the Class A materials with a thin layer of some non-qualified corrosion resistant material. However, there are currently no ASME design rules for cladded components to guard against creep-fatigue failure and ratcheting strain accumulation in elevated temperature nuclear service. Therefore, design methods along with a complete set of design rules for cladded components were developed in [PVP2020-21469]. In order to support the near-term deployment of these advanced reactor systems, the underlying goal of the new design rules was to avoid relying on long-term test data of the clad materials. New design rules for two types of clad materials fulfill this requirement. They are soft clad materials that creep much faster and hard clad materials that creep much slower than the Class A base materials. This necessitates the development of criteria for selecting clad materials which fall into either the hard or soft category. A previous work [PVP2020-21493] developed such clad selection criteria for a Class A metallic alloy — Type 316H stainless steel. These criteria require comparing the minimum creep rate between the clad and base materials at different stresses and temperatures and therefore need some short term creep test data to develop a minimum creep rate model for the prospective clad materials. To reduce the creep testing effort for the clad materials this work develops a new set of clad selection criteria — requiring creep tests at a single condition or no test at all; thus it is much simpler to execute. Sample finite element analyses of a representative high temperature reactor vessel are performed to verify the clad selection criteria.
Development of Leak Before Break Assessment Guidelines for Sodium Cooled Fast Reactors in Japan
Authors: Yada Hiroki , Wakai Takashi , Miyagawa Takayuki , Machida Hideo
Published: October 2021

The leak before break (LBB) assessment guidelines for sodium cooled fast reactors (SFRs) is being developed in the Japan Society of Mechanical Engineers (JSME). The major purpose of the guidelines is to provide LBB assessment procedures for pipes and vessels of SFRs that retain sodium coolant. Design features of SFRs, such as high operation temperatures and low pressure coolant-systems, are taken into account. The LBB guidelines is used in connection to the fitness-for-service code that is also being developed for SFRs in JSME. If the establishment of LBB concept is successfully demonstrated, continuous leakage monitoring will be adopted as an in-service inspection for SFR components constituting sodium coolant boundary, such as sodium retaining pipe and vessels. The LBB assessment consists of three main paths, which are “Unstable fracture assessment”, “Leak rate assessment” and “Penetrated crack assessment”. “Unstable fracture assessment” is conducted to determine a critical crack length, ccr, which introduces unstable fracture under given loading conditions. “Leak rate assessment” is carried out to determine detectable crack length, cd, above which sodium leakage can be detected by installed leak detectors. In order to assess the cd, a new crack opening displacement evaluation method was developed for thin walled large diameter cylindrical structures taking the geometrical feature of SFR pipes into account. “Penetrated crack assessment” is performed to determine cp, the crack length when a crack penetrates the wall, under given transients hypothetically repeated enough cycles for the crack to penetrate the wall. In order to assess the cp, a simplified method was developed both for axial and circumferential cracks as a function of the ratio of membrane and bending stresses and fatigue crack growth characteristics. In the cp assessment, penetrated crack length is evaluated by considering only fatigue crack growth mechanism because penetrated crack length without considering creep effects becomes longer. If ccr is longer than both cd and cp, it can be concluded that the establishment of LBB concept is demonstrated. To demonstrate the procedure of LBB guidelines, actual SFRs piping was evaluated and the establishment of LBB concept is successfully demonstrated.
Development of Minimum Pressurization Temperature Envelopes for Hydroprocessing Reactors - A Case Study
Authors: Kagita Gurumurthy , Pudipeddi Krishnakant V. , Pottem Penchala S. K. , Achary Gudimella G. S. , Sripada Subramanyam V. R.
Published: October 2021

Low alloy heavy-walled hydroprocessing reactors in the refining industry, which operate at elevated temperatures and high hydrogen environments, need to be designed for protection against brittle fracture especially during start-up and shutdown. While developing minimum pressurization temperature (MPT) envelopes for these reactors, both temper and hydrogen embrittlement effects must be considered. However, there are no specific rules to evaluate loss of toughness due to hydrogen embrittlement in the design Codes / fitness-for-service Standards. Earlier, Japanese steel and pressure vessel manufacturers (JSPVM) developed a methodology to estimate MPT envelope for Cr-Mo steel pressure vessels. Recently, a state-of-the-art fracture mechanics based methodology is published in Welding Research Council (WRC) Bulletin 562 to determine MPT envelopes for equipment operating in high-pressure hydrogen environments. Meanwhile, API RP 934-F draft provided guidance on developing MPT envelops for heavy wall Cr-Mo vessels. In this paper, a brief summary of the JSPVM, API and WRC approach is presented with flow charts. A case study of establishing the MPT envelopes for a typical hydroprocessing reactor using WRC, JSPVM and API approach is presented and the results are compared and discussed. The advantages and potential savings of using recent WRC approach are highlighted.