bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Assessment of Data-Driven Digital Twins in a Nearly Autonomous Management and Control System for Advanced Reactors
Authors: Lin Linyu , Rouxelin Pascal , Athe Paridhi , Dinh Nam , Lane Jeffrey 
Published: October 2020

Abstract
A critical component of the autonomous control system is the implementation of digital twin (DT) for diagnosing the conditions and prognosing the future transients of physical components or systems. The objective is to achieve an accurate understanding and prediction of future behaviors of the physical components or systems and to guide operating decisions by an operator or an autonomous control system. With specific requirements in the functional, interface, modeling, and accuracy, DTs are developed based on operational and simulation databases. As one of the modeling methods, data-driven methods have been used for implementing DTs since they have more adaptive forms and are able to capture interdependencies that can be overlooked in model-based DTs.
To demonstrate the capabilities of DTs, a case study is designed for the control of the EBR-II sodium-cooled fast reactor during a single loss of flow accident, where either a complete or a partial loss of flow in one of the two primary sodium pumps is considered. Based on the definition of DTs and the design of autonomous control system, DTs for diagnosis and prognosis are implemented by training feedforward neural networks with suggested inputs, training parameters, and knowledge base. Furthermore, inspired by the validation and uncertainty quantification scheme for scientific computing, a list of sources of uncertainty in input variables, training parameters, and knowledge base is formulated. The objective is to assess qualitative impacts of different sources of uncertainty on the DT errors. It is found that the performance of DT for diagnosis and prognosis satisfies the acceptance criteria within the training databases. Meanwhile, the accuracy of DTs for diagnosis and prognosis is highly affected by multiple sources of uncertainty.
Research on Analysis and Modeling Methods for LBLOCA in Nuclear Power Plants Based on Autonomous LOCA Analysis Platform ARSAC
Authors: Zhou Jiayue , Wu Dan , Ding Shuhua , Jiang Guangming 
Published: October 2020

Abstract
In order to meet the demand of continuous innovation of technologies and the general trend of autonomous nuclear power plants design and export of nuclear power plants, it is necessary to develop an autonomous LOCA analysis platform and corresponding analysis methods for the most complex design basis accidents. In this paper, the characteristics of LOCA analysis platform ARSAC, designed by Nuclear Power Institute of China, and the code ARSAC-K which meets the requirements of the US Federal Code 10 CFR 50.46 Appendix K model are introduced as well as a set of LOCA analysis methods and modeling methods. Based on the international advanced LOCA analysis code development concept, the code ARSAC has made new breakthroughs in matrix algorithms, key thermal hydraulic models and so on. Validation work has also been carried out in-depth. A set of advanced LOCA analysis methods has been developed using code ARSAC-K and advanced power plant parameter sampling methods. Analysis on LBLOCA of nuclear power plants with code ARSAC-K was performed, and the impact of different modeling methods on the LOCA analysis results was studied. To ensure the rationality and conservativeness of the analysis results, a set of reasonable and conservative modeling methods is fixed on the basis of a large number of sensitivity analyses for subsequent analysis and calculation. In the future, a lot of optimization work will be done to improve the LOCA code and corresponding methods.
Uncertainty Quantification of Seismic Response of Reactor Building Considering Different Modeling Methods
Authors: Choi Byunghyun , Nishida Akemi , Muramatsu Ken , Itoi Tatsuya , Takada Tsuyoshi 
Published: October 2020

Abstract
After the 2011 Fukushima accident, the seismic regulations for nuclear power plants (NPP) in Japan have been strengthened to include countermeasures far beyond design-basis accidents. The importance of seismic probabilistic risk assessments, therefore, have been the focus of deserved attention. Generally, an uncertainty quantification has been a very important undertaking to assess for fragility in NPP buildings. Therefore, this study focuses on the reduction in epistemic uncertainty by aiming to clarify the seismic-response effects on NPP buildings based on different modeling methods. As a first step in this study, the authors compared the seismic-response effects using two modeling methods of analysis. To evaluate the seismic response, an analysis was performed on two building model types; these being the three-dimensional (3D) finite-element model and the sway-rocking model with a conventional lumped mass system. To input a ground motion, the authors adopted 200 types of simulated seismic ground motions, generated by fault-rupture models, using stochastic seismic source characteristics. For the uncertainty quantification, we conducted a statistical analysis of the seismic responses acquired from the two modeling methods based on the building response each ground-motion input, and quantitatively evaluated the uncertainty response by considering the different modeling methods. We found a clear difference in the modeling methods near the floor and wall openings. We also imparted our knowledge on these 3D effects for the seismic-response analysis.
Analytical Justifications As Part of the “Post-Fukushima” Upgrades Implementation on Zaporizhzhya NPP Unit 1
Authors: Mazurok Oleksandr , Ivanov Vadym , Kocharyants Oleg 
Published: October 2020

Abstract
In accordance with a complex program to improve the safety of Ukrainian NPP units, a number of “Post-Fukushima” upgrades are being implemented. The upgrades were identified based on the results of “stress-tests” performed after the severe accident at the NPP Fukushima Daiichi (Japan) and aimed at preventing or managing a severe accident. As part of the implementation of upgrades for the possibility of installation and commissioning of new equipment, in accordance with regulatory documentation, is required confirmation that the upgrade will not lead to a degradation of the NPPs safety. For this purpose, the safety analysis report and analytical calculations, including thermal-hydraulic, probabilistic and radiation analysis, are developed. In this paper, on the example of “Post-Fukushima” upgrades, the practical experience of performing analytical calculations in order to justify the safety of Ukrainian NPP power units is described. As an example, Zaporizhzhya NPP Unit 1 (reactor facility type: VVER-1000/V320, reactor type: PWR VVER-1000, operational electric power: 1000 MW) was chosen, which is a pilot for the implementation of “Post-Fukushima” upgrades in Ukraine mainly. In this paper, on the example of “Post-Fukushima” upgrades, the practical experience of performing analytical calculations in order to justify the safety of pilot unit is described.
Company ES Group and its employees took part in the implementation of most upgrades by supporting domestic and foreign companies, as well as the NPP operator, for the successful implementation of upgrades using the best technical solutions and modern calculation justifications.
Probability of Rupture for WWER-1000 Main Piping
Authors: Dubyk Yaroslav , Zarazovskii Maksym , Ageiev Sergii , Filonov Vladislav 
Published: October 2020

Abstract
A probability of rupture for WWER-1000 main piping was calculated based on the Failure Assessment Diagram (FAD), treating material properties of welds (the most likely zone for crack growing and its nucleation) and crack morphology parameters as stochastic values. In order to perform probabilistic calculations, Critical Temperature of Brittleness (CTB, WWER’s analogue of PWRs transition temperature which used to index the Fracture Toughness curve) and Yield (Ultimate) Strength as well were fitted by normal distribution, based on experimental data taken from the manufacture documentation of Ukrainian Nuclear Power Plants (NPPs). A set of calculations were conducted for Normal Operating conditions (NOC), Safe Shutdown Earthquake (SSE) and several emergency situations like: shaft jamming of a reactor cooling pump and break of the piping’s, connected to the considered ones (a set of LOCA events). Based on static and dynamic calculations, the most loaded zones were selected, where the cracks were postulated. Crack opening area was calculated according to original developed procedure, which accounts for membrane and linear stress components through the wall thickness. The Henry-Fauske flow model is used with modified parameters accounting for crack morphology as a normally distributed random variable. It is an important part of analysis, since different crack types have great differences in friction, bend protrusion and flow length parameters. The rupture probabilities for Main Circulating Piping were calculated with accounting for thermal aging effect. It was proven, that crack morphology parameters highly affect the leak rate and its distribution becomes more scattered. Among the mechanical characteristic, a Fracture toughness has more influence rather than Ultimate of Yield strength.
Modeling the Flow Redistribution Upstream From the Spacer Grid of a PWR
Authors: de Lambert Stanislas , Cardolaccia Jérome , Faucher Vincent 
Published: October 2020

Abstract
Fuel assemblies’ deformation is an industrial issue that has been first reported in the 90’s. This phenomenon has originally been pointed out for being the explanation of IRI (incomplete rod cluster insertion). Recently, fuel assembly bowing has regained attention for its impact over several core’s management issues, including core neutronics.
When deformation occurs, it tends to alter bypasses geometry around the affected fuel assembly. The water gaps’ thicknesses along the assembly’s height does not match the nominal value anymore. As a result, spacer grids can get closer of farther to the surrounding ones. The redistribution between the bypasses and the grid is then involved, depending on the bypasses’ thicknesses and the grid geometry. This unfolding effect entails differences in pressure laterally along a grid, which thus brings about a lateral hydraulic force exerting on the grid.
The following paper presents a method to esteem this redistribution thanks to an hydraulic network. Hydraulic resistances can be set up according to the bypass thickness. As a result, both pressure and volumetric flow rates can be calculated to further estimate lateral forces.
The approach has been validated with both CFD simulations and an experimental mock-up.
Computational Fluid Dynamics Simulation of a Single-Phase Rectangular Thermosiphon
Authors: Nguyen Tri , Merzari Elia 
Published: October 2020

Abstract
Buoyancy-driven flows are widespread in diverse engineering applications. Such flows have been studied in great detail theoretically, experimentally, and numerically. However, the fluid-dynamic instabilities and flow reversals of thermosiphon are still actively investigated. The presence of such instabilities limits the effectiveness of such devices for decay heat removal.
Traditionally the stability analysis of natural convection loops has been confined to one-dimensional calculations, on the argument that the flow would be mono-dimensional when the ratio between the radius of the loop and the radius of the pipe is much larger than 1. Nevertheless, accurate velocity measurements of the flow in toroidal loops have shown that the flow presents three-dimensional effects. Previous works of the authors have shown that these structures can be seen in thermosiphons. In this paper, we aim to use modern CFD methods to investigate the three-dimensional flow in thermosiphons.
This paper focuses on rectangular thermosiphons. In particular, we perform a series of high-fidelity simulations using the spectral element code Nek5000 to investigate the stability behavior of the flow in a rectangular thermosiphon. We compare the results with available existing experimental data from the L2 facility in Genoa. We examine in detail the flow structures generated.
Moreover, in the past various authors have demonstrated that the overall behavior of the thermosiphon depends strongly on the boundary conditions (BCs). The simulation campaign was carried out with different BCs to investigate and confirm this effect. In particular, simulations with Dirichlet, Neumann and Robin BCs for heater and sink were performed.
Considerations for Development of Probabilistic Assessments for Nuclear Systems and Components
Authors: Pandey Mahesh , Wasiluk Bogdan 
Published: October 2020

Abstract
The risk-informed approach has been increasingly utilized by the nuclear industry and the regulators in Canada and around the world. This involves the assessment of plant risk and the considerations for defence-in-depth, safety margin and other nuclear safety principles. The estimates of reliability metric have been commonly obtained using probabilistic methods that involve distributed inputs. While the engineering focus has typically been on finding a solution for a specific problem, the scientific community and the regulators are concerned with generic principles, foundation of probabilistic approaches and definition of reliability metric used in the assessment. In this paper, the concept of a time-dependent reliability framework is discussed to facilitate selecting the appropriate approach to meet, in principle, the assessment intent. In the end, any probabilistic assessment should be fundamentally meaningful, consistent and transparent to inspire confidence in the public and the regulators.
Analysis of Droplet Impacting on Inclined Wall
Authors: Chen Bowen , Wang Bo , Ke Bingzheng , Li Ru , Tian Ruifeng 
Published: October 2020

Abstract
The steam generator is an important part of the nuclear power plant, and the corrugated plate separator plays the important role of drying steam in the steam generator to improve power generation efficiency and protect the safety of the system. The separation mechanism of the corrugated plate separator is relatively complicated. The droplets are moved by the drag force of the steam and gravity in the corrugated plate separator, and captured by the wall of the corrugated plate separator. When the velocity is increased, the inertial force of droplet is increased, so that the droplet is more easily captured by the wall of the corrugated plate separator, and the separation efficiency of the corrugated plate separator is increased. In this paper, the phenomenon of droplet impact on the inclined wall is studied by high-speed photography technology, and the cause and mechanism of the phenomenon are analyzed. By analyzing the spreading and splashing on the droplets impacting on the inclined wall, the relationship between the inclination angle of the droplet impacting on the inclined wall and the spreading is obtained, and the influence of droplets with different Weber numbers, and dry and wetted walls were analyzed, which provide a basis for the optimization of the corrugated plate separator.
Study on Effect of Sloshing Phenomenon on Water Level of Pressurizer
Authors: Jiarui Chen , Jianchang Liu , Dongyang Li , Sichao Tan 
Published: October 2020

Abstract
As the key equipment to control the pressure stability of the coolant system, the pressurizer plays a role in maintaining the primary system pressure in the reactor. During the operation of the sea-based reactor, the internal free liquid level of the pressurizer will fluctuate greatly with different marine cycles, causing additional acceleration in the horizontal or vertical direction, which will cause the water level measured by the differential pressure measurement method to deviate from the actual water level. It will adversely affect the judgment and control of the signal. Moreover, the fluctuating liquid level will frequently trigger the water level alarm signal, resulting in the submersion of the sprinkler tuber and the exposure of the electric heating rod, which will reduce the safety and economy of the reactor. Therefore, this research is aimed at suppressing the fluctuation range of the water level and correcting the deviation of the water level measurement so as to improve the inherent safety of the reactor. In the present study, the experimental system consists of a motion excitation drive mechanism and an optical system. The experimental system has successfully established sloshing phenomenon of the pressurizer under different forms of motion by Laser induced fluorescence (LIF) technique and the experimental results obtained are compared with numerical results. The results of the research show that the pressurizer can make significant free surface fluctuation when excitation close to the natural frequency of the pressurizer. The suppression model developed by FLUTENT can effectively reduce the fluctuation range of free liquid level. In addition, the deviation of water level measurement enlarges with the swing angle increasing. The deviation can be reduced to the allowable error range by means of angle correction.
Examining Multilevel Environmental Correlates of Physical Activity Among Older Adults With Multiple Sclerosis
Authors: Silveira Stephanie L. , Baird Jessica F. , Motl Robert W. 
Published: October 2020

Three hundred and sixty-three older adults with multiple sclerosis completed a cross-sectional study examining hierarchical correlates of physical activity using a social cognitive theory perspective within a social ecological model (i.e., built environment, social environment, and individual social cognitive theory variables). Hierarchical linear regression analyses were conducted, wherein significant associations were noted for built environment (i.e., land-use mix diversity and aesthetics) and physical activity in Step 1 (R2 = .09). Social and built environment were significant correlates in Step 2 (R2 = .15). Finally in Step 3, individual social cognitive theory variables (i.e., self-efficacy and outcome expectations) were the only significant correlates of total physical activity (R2 = .38). Results were comparable for health-promoting physical activity; however, self-efficacy was the only significant correlate in Step 3 (R2 = .36). This study provides guidance for researchers and practitioners on relevant targets for tailoring interventions for older adults with multiple sclerosis and supports an emphasis on self-efficacy as a primary predictor of health behavior change.
Influence of Badminton Practice on Age-Related Changes in Patellar and Achilles Tendons
Authors: Bravo-Sánchez Alfredo , Abián Pablo , Sousa Filipa , Jimenez Fernando , Abián-Vicén Javier 
Published: October 2020

Regular sport practice could prevent age-related changes in tendinous tissues. The purpose of the study was to investigate the effect of regular badminton practice on patellar and Achilles tendon mechanical properties in senior competitive badminton players (>35 years old) and to compare the results with physically active people matched by age. One hundred ninety-two badminton players and 193 physically active people were divided by age into four groups, between 35 and 44 (U45), between 45 and 54 (U55), between 55 and 64 (U65), and over 65 (O65) years old. A LogiqS8 transducer in elastography mode and a MyotonPRO myotonometer were used to assess patellar and Achilles mechanical properties. Achilles tendon stiffness was higher in the control group than the badminton players for the U45, U55, and O65 age groups (p < .01). Also, the elastography index was higher in the control group than the badminton players for the U45, U55, U65, and O65 age groups (p < .05). In conclusion, regular badminton practice could prevent the decline in mechanical properties of the patellar and Achilles tendons.
Bidirectional Day-to-Day Associations of Reported Sleep Duration With Accelerometer Measured Physical Activity and Sedentary Time Among Dutch Adolescents: An Observational Study
Authors: Berninger Nathalie , Knell Gregory , Gabriel Kelley Pettee , Plasqui Guy , Crutzen Rik , Ten Hoor Gill 
Published: October 2020

Objectives: To examine the bidirectional association of sleep duration with proportions of time spent in physical behaviors among Dutch adolescents. Methods: Adolescents (n = 294, 11–15 years) completed sleep diaries and wore an accelerometer (ActiGraph) over 1 week. With linear mixed-effects models, the authors estimated the association of sleep categories (short, optimal, and long) with the following day’s proportion in physical behaviors. With generalized linear mixed models with binomial distribution, the authors estimated the association of physical behavior proportions on sleep categories. Physical behavior proportions were operationalized using percentages of wearing time and by applying a compositional approach. All analyses were stratified by gender accounting for differing developmental stages. Results: For males (number of observed days: 345, n = 83), short as compared with optimal sleep was associated with the following day’s proportion spent in sedentary (−2.57%, p = .03, 95% confidence interval [CI] [−4.95, −0.19]) and light-intensity activities (1.96%, p = .02, 95% CI [0.27, 3.65]), which was not significant in the compositional approach models. Among females (number of observed days: 427, n = 104), long sleep was associated with the proportions spent in moderate- to vigorous-intensity physical activity (1.69%, p < .001, 95% CI [0.75, 2.64]) and in sedentary behavior (−3.02%, p < .01, 95% CI [−5.09, −0.96]), which was replicated by the compositional approach models. None of the associations between daytime activity and sleep were significant (number of obs.: 844, n = 204). Conclusions: Results indicate partial associations between sleep and the following day’s physical behaviors, and no associations between physical behaviors and the following night’s sleep.