bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of Structural Optimization for Inlet Pipe of Centrifugal Pump in CAP1400 Power Plant Auxiliary System
Authors: Qu Ting , Zhang Liang
Published: October 2020

The centrifugal pump is the key equipment for power conversion in the CAP1400 power plant. According to the equipment layout requirements in the nuclear power plant process system design manual, the pipe section at the entrance should be a straight pipe with a length at least five times the pipe diameter. However, in actual layout, due to factors such as plant space or modularity, the layout of the inlet pipes of some centrifugal pumps cannot meet this requirement, resulting in non-uniform incoming flow at the pump inlet, which affects the safe and stable operation of the pump and system. In this paper, two different structures of rectifiers are designed and numerically simulated for the elbow part of the inlet pipe section of the SFS system centrifugal pump in the CAP1400 power plant. Firstly, the variation of flow uniformity of the pump inlet pipe at different inlet speeds is studied. Then, the influence of different structure rectifiers on the uniformity of flow at the pump inlet under the same working conditions is studied. The results show that the addition of a rectifier in the elbow can effectively improve the flow uniformity of the pump inlet section and reduce the effect of uneven inlet flow on the pump performance.
A Review of Degradation Modeling of Key Components of Sensor Circuits Based on Physical Analysis
Authors: Zhu Yonlong , Huang Xiaojin , Zhou Shuqiao
Published: October 2020

Nuclear power plant (NPP) accidents can cause severe effects. In order to ensure the normal operation of NPP, instrument and control system (I&C) composed of multiple sensors plays an important role in it. The sensor consists of sensitive components and functional circuits. In this paper, temperature sensor commonly used in NPP, PT100, is used as an example, and a bottom-up based physical analysis method is used to review the degradation mechanism and physical model of key components in resistance temperature detector (RTD) circuits. Resistors, capacitors, and MOSFETs are the key components of sensor circuits. Thin film resistors are the most widely used resistors due to their good performance. The transformed Arrhenius’ equation is used to describe its degradation characteristics. For the most commonly used aluminum electrolytic capacitors, the model reviewed in this paper can accurately describe the changes in equivalent series resistance (ESR), and use this as a criterion for determining capacitor failure. MOS technology is widely used in analog circuits. We have summarized three physical degradation processes, channel hot carrier (CHC), negative bias temperature instability (NBTI), and time-dependent dielectric breakdown (TDDB), that affect MOSFET performance. The physical model of the key component degradation of the sensor circuit summarized in this paper provides a basis for the subsequent establishment of a circuit-level degradation model.
Investigation on Post Accident Heat Removal From Partial Core Relocation in Lower Plenum After CDA in SFRs: 3-D CFD Analysis
Authors: Jhade Vidhyasagar , Sharma Anil Kumar , Kasinathan N.
Published: October 2020

In the present article, authors have carried out a three-dimensional (3D) Computational Fluid Dynamics (CFD) analysis of turbulent natural convection heat transfer from relocated core debris, in typical Sodium cooled Fast Reactors (SFRs), following a Core Disruptive Accident (CDA). Full-Scale analysis of complete sodium pool, i.e., hot and cold pool including immersed decay heat exchanger, has been carried out. k–ω SST model is used for turbulence closure. The model is selected based on the validation exercise. Core catcher (CC) with multiple passive jets over the Heat Shield Plate (HSP) is considered for analysis. Earlier CFD analysis with the assumption of whole core relocation on CC gave a CC temperature higher than the allowable limit. Hence, in this study, the analysis of partial relocation of the core debris on the CC has been carried out. From this, the maximum extent of relocatable core debris on the CC, which conforms with the allowable criteria, has been observed. Therefore, we have investigated the cases where the percentage of core debris relocation varies from 30–100% on HSP and remaining in the original position. This configuration may influence the decay heat removal via the hot pool. Time-dependent decay heat sources are used. Isotherms and streamlines have been presented to understand heat transfer characteristics. It has been found that with the implementation of multi jets CC, debris settled on HSP does not cross the threshold sodium boiling (∼1200 K) temperature up to 70% debris relocated to HSP with single tray configuration. Heat source surface, which remains at the core and in direct contact with coolant (liquid sodium), reaches a maximum value ∼1031 K for the case where the two-third core is intact at the core region. For HSP, it has been found that the thermal design limit exceeds (∼923 K) when 50% of debris relocates to the lower plenum. The transient study shows that time to attain maximum temperature by debris and HSP is inversely proportional to the percentage of intact core.
Experimental Study on Transient Heat Transfer for Helium Gas Flowing in a Minichannel
Authors: Xu Feng , Liu Qiusheng , Kawaguchi Satoshi , Shibahara Makoto
Published: October 2020

The blanket modules of first wall need bear tremendous heat flux due to the very high temperature of plasma in the nuclear fusion reactor. Therefore, it is significant to clarify the knowledge of transient heat transfer process for helium gas flowing in the tubes installed in the blanket modules.

In this research, the transient heat transfer process of turbulent forced convection for helium gas flowing in a horizontal minichannel was experimentally investigated. The test tube made of platinum with the inner diameter of 1.8 mm, the wall thickness of 0.1 mm and the effective length of 90 mm was heated by a direct current from power source. The heat generation rate of the test tube, Q̇, was raised with an exponential function, Q̇ = Q0 exp(t/τ), where Q0 is the initial heat generation rate, t is time, and τ is e-folding time of heat generation rate. The heat generation rates of the test tube were controlled and measured by a heat input control system. The flow rates were adjusted by the bypass of gas loop and measured by the turbine flow meter. The experiment was conducted under the e-folding time of heat generation rate ranged from 40 ms to 15 s. Based on experimental data, it is obvious that the heat flux and temperature difference between surface temperature of test tube and bulk temperature of helium gas increased with the exponentially increasing of heat generation rate. At the same flow velocity, the heat transfer coefficients approached constant values when the e-folding time is longer than about 1 s (quasi-steady state), but increased with a decrease of e-folding time when the e-folding time is smaller than about 1 s (transient state). The heat transfer coefficients increased with the increase in flow velocities but showed less dependent on flow velocities at shorter e-folding time. Furthermore, the Nusselt number under quasi-steady and transient condition was affected by the Reynolds number and the Fourier number.
Deep Gouging Technique for Fuel Debris Retrieval in Fukushima Daiichi
Authors: Doyen Ioana , Chagnot Christophe , Journeau Christophe , Porcheron Emmanuel , Gelain Thomas , Roulet Damien
Published: October 2020

Laser cutting, a contactless remote controlled process, was assessed for nuclear decommissioning applications, in full through-thickness-cutting (emerging cutting) and deep gouging (non-emerging) conditions.

This work aims at presenting specific tools developed and implemented at CEA Saclay, to evaluate and to optimize new cutting strategies, in terms of robustness and reliability, in order to best adapt the laser cutting process to fuel debris retrieval specificities of Fukushima Daiichi reactors.

Several configurations for deep gouging have been tested in DELIA facility to reach more than 40 mm of cut-thickness in one pass with an 8kW laser power. First, the laser cutting process was assessed on fused cast zirconia blocks and then on 316L stainless steel and fuel debris simulant blocks. This paper presents the main results of the tests performed in representative conditions of “in site conditions” such as: edge or bulk start/stop cutting, complex surface (i.e. surface with a varying topology) cutting, stand-off variation, angle of cut, trajectories misalignment, and material heterogeneity. Moreover, the excellent performances achieved on 316L stainless steel and fuel debris simulants indicate that deep gouging applied to nuclear decommissioning is a promising technology.
Development and Application of Dose Assessment Methodology During IS-LOCA in BWR Plant
Authors: Iwanami Hironobu , Hashimoto Tomoharu , Tanaka Motoi , Tayama Ryuichi , Mizuno Satoshi , Uemura Takashi
Published: October 2020

A dose assessment methodology was developed for IS-LOCA (Interface System – Loss of Coolant Accident) event, which is one of the design basis accidents in BWR plants, and a dose assessment at site boundary was implemented for the accident scenario by applying the evaluation method. The main objective of the assessment is to review a conventional conservative dose assessment model in the accident scenario.

The conventional conservative model is a method due to considering all fission products (FP) in liquid migrate to airborne (i.e. 100%) when reactor water is discharged from piping break area, while the developed new methodology is a method to evaluate transition behavior of fission products precisely by using flash fraction (FF) from liquid to airborne and consider it.

As the result of dose assessment, it was confirmed that the calculated dose during IS-LOCA event was about one-fifteith reduced by adopting the new model from the conventional model. The content of this paper includes:

• Background and purpose that led to the dose assessment methodology development during IS-LOCA.

• An evaluation method by using discharged amount of reactor water at piping break area and flash fraction (FF) from liquid to airborne based on Regulatory guide 1.183 published by U.S. NRC.

• Another evaluation method that takes into account the fluctuation due to depressurization of reactor pressure per time step from the start of accident until completion of isolation at piping break area in addition to the above method.

• Comparison between dose results at site boundary based on these methods and conventional conservative model. This results will give a precise information for public and it will be useful for making emergency evacuation plan.
High-Energy X-Ray CT Measurement of Void Fraction Distribution Around Part Length Rods in a Rod Bundle at High Pressure and Temperatures
Authors: Arai Takahiro , Ui Atsushi , Furuya Masahiro , Okawa Riichiro , Iiyama Tsugumasa , Ueda Shota , Shirakawa Kenetsu , Kito Kazuaki
Published: October 2020

A boiling experiment was conducted to acquire a three-dimensional void fraction distribution in a rod bundle with part length rods. The test section was a 5 × 5 heated rod bundle that partially simulated a BWR rod bundle, and three PLRs were arranged together in the corner. The heated length of the full-length rod was 3.71 m, which is equal in length to an actual fuel rod in BWRs, whereas the heated length of the PLR was 1.85 m. The rod bundle exhibited an axially and radially uniform heat flux. Further, the local void fraction was quantified by normalizing the intensities in the CT images of the boiling two-phase flow with those obtained under the liquid-phase and gas-phase conditions. The cross-sectional void fraction distribution was acquired at six height levels. The experimental results exhibited the void distribution around PLRs with respect to a wide range of flow conditions, inlet temperatures, inlet flow rates, bundle thermal powers, and system pressures.
Theoretical Research on Two-Phase Flow Instability in Parallel Rectangular Channels Under Periodic Perturbation
Authors: Qian Libo , Deng Jian , Huang Tao , Cai Rong
Published: October 2020

A theoretical model for Density Wave Oscillations (DWOs) flow instability in parallel rectangular channels under periodic heaving motion is established with a lumped mathematical model based on homogenous hypothesis. The parallel rectangular channels comprise of the entrance section, the heating section, the riser section and the upper- and lower plenums, which guarantee the isobaric pressure drop condition between channels and the model consists of boiling channel model, pressure drop model, parallel channel model, additional pressure drop model generated by heaving motions, the constitutive and numerical models. The effect of periodic perturbation is introduced through additional pressure drop in the momentum equation. The model is validated with experimental data of a twin-rectangular-channel flow instability experiment under static condition. Then the flow instability in parallel-rectangular-channel system is studied under periodic perturbation and the margin of flow instability and the threshold power of the system under static condition is calculated as basis condition for comparison. The effect of the amplitude and period of perturbation is analyzed analytically and the results show that the amplitude and period of perturbation shows little effect on flow instability. While when the additional pressure difference introduced by heaving motion is comparable with that under static condition, the effect of amplitude becomes stronger. And the period of perturbation strongly effects the threshold power when it is identical to that of natural period of the system, which can be explained by resonance between the perturbation and the system. And this effect is even stronger when the asymmetric heating condition is introduced.
Preliminary Development on Thermal-Hydraulic Analysis Code for the Spent Fuel Rod Under the Condition of Spray Cooling
Authors: Chao Guo , Jian Deng , Rong Cai , Yugao Ma , Lili Liu , Yuhao Zhang , Siyu Lv
Published: October 2020

According to spray cooling characteristics for failure of the cooling system in the spent fuel pool, we establish a model for analyzing spray cooling of a single spent fuel rod and develop a code named SFSC which is used to calculate the thermal-hydraulic characteristics of film on the spent fuel rod under the condition of spray cooling. The results obtained from SFSC consist of film thickness, film temperature, film evaporation, fuel pellet temperature of spent fuel rod and cladding temperature of spent fuel rod at different height of spent fuel rod are shown in this paper. At the same time, we establish same model by RELAP and compare results calculated by RELAP with that calculated by SFSC. The good agreement of two results demonstrates that SFSC is effective. SFSC fills in the blanks of thermal-hydraulic calculation for the spent fuel rod under the condition of spray cooling.
Challenge to Investigation of Fuel Debris in RPV by an Advanced Super Dragon Articulated Robot Arm: Design and Prototyping of a Lightweight Super Long Reach Articulated Manipulator
Authors: Endo Gen , Takahashi Hideharu , Kikura Hiroshige
Published: October 2020

A long-reach articulated manipulator that can deploy various sensors in a large but confined workspace is urgently needed in decommissioning tasks at Fukushima Daiichi Nuclear Power Stations. The most critical problem involves managing the large gravitational torques acting on the manipulator’s joints. In previous studies, several prototype models were developed; however, they were extremely heavy and bulky. This paper presents fundamental ideas for creating a lightweight super long-reach articulated manipulator. First, a mechanical structure could be utilized to support gravity. Second, a vertical force could be generated to compensate for gravity. Third, a tendon-driven mechanism could be utilized because it permits the installation of heavy actuators on the base. The tendons can transmit the actuator power to each joint. Thus, the weight of the arm is significantly reduced. We have discussed the advantages and drawbacks of each recommendation based on the hardware prototyping.
Local Damage to Reinforced Concrete Panels Subjected to Oblique Impact by Projectiles: Outline of Impact Test
Authors: Nishida Akemi , Kang Zuoyi , Okuda Yukihiko , Tsubota Haruji , Li Yinsheng
Published: October 2020

Studies on the local damage to reinforced concrete (RC) panels subjected to projectile impact have mainly focused on collisions that occur at an angle normal to the structure; thus, research on oblique impact is scarce. Due to this, we conducted research focusing on oblique impact to enable more realistic impact assessment of projectile collisions. To date, the validity of the analytical method has been confirmed by comparing the results with those of previous tests, and the local damage to RC panels that have collided with projectiles has been analytically investigated focusing on the impact angle. Therefore, this study aims to confirm the validity of the analysis method by conducting specific impact tests under various conditions, including the impact angle, by obtaining the relevant data. This paper outlines the test for the local damage to RC panels subjected to both normal and oblique impacts.
Analytical Study on Dynamic Response of Reinforced Concrete Structure With Internal Equipment Subjected to Projectile Impact
Authors: Okuda Yukihiko , Kang Zuoyi , Nishida Akemi , Tsubota Haruji , Li Yinsheng
Published: October 2020

In case of a projectile impact on a reactor building of a nuclear power plant, stress waves propagate from the impacted wall to the structure’s interior. It is important to assess the effect of dynamic responses generated by the projectile’s impact on internal equipment, because stress waves are likely to excite high-frequency vibrations of internal equipment. The OECD (Organization for Economic Co-operation and Development) / NEA (Nuclear Energy Agency) launched the IRIS (Improving Robustness Assessment Methodologies for Structures Impacted by Projectiles) benchmark project in order to assess the dynamic response of a nuclear facility to projectile impact, and the third phase of IRIS (IRIS 3) [1] contributes to the investigation of the dynamic responses of reinforced concrete (RC) structures that house internal equipment. We have participated in IRIS 3 and have performed calibration analyses of projectile impact tests on a structure that models a reactor building that houses internal equipment. Specifically, we have developed and validated a numerical approach to investigation of impact responses of an RC structure that houses internal equipment through calibration correction. This paper presents partial simulation results of the dynamic responses of this structure and discusses the effects of support conditions of the internal equipment and stress wave propagation.
Experimental Study on Aerosol Collection by Spray Droplets: Application to Fission Products Removal in Containment
Authors: Sun Haomin , Leblois Yohan , Gelain Thomas , Porcheron Emmanuel
Published: October 2020

During a severe accident of a pressurized water reactor (PWR), fission products (FPs) may be released and transported to the containment. The containment spray can be utilized to remove the aerosols of FPs, which contributes to retaining the FPs in the sump. Therefore, it is important to develop an analytical model for predicting the aerosol removal efficiency by the containment spray for nuclear safety. The containment spray is required to have a very high spray coverage ratio where the droplets are expected to impact the containment side walls. In such condition, the gas flow induced by the droplets will behave differently from that in the other condition without the droplet impaction where a stable gas circulation is expected between the boundary of the spray and the side walls. Since the aerosol removal efficiency also depends on the gas flow behavior, to develop the aerosol removal model applicable for the containment spray from this viewpoint, several aerosol removal experiments were carried out in the TOSQAN IRSN facility. Based on the droplet mass flux measurements, it was confirmed that the spray coverage ratios were comparable to that of the containment spray and many droplets impacted the side wall. According to the aerosol measurement results, it was found the aerosol removal was more effective in higher spray water flow rates. Since larger particles were removed more quickly, the mean particle diameter was decreasing during the spray operation and approached to a value. Based on a CFD simulation for the experiment, gas velocity field was investigated. The measured and calculated particle number concentration decays agreed well.
Convolutional Neural Network Considering the Effects of Noise for Bearing Fault Diagnosis
Authors: Han Ilyoung , Chai Jangbom , Lim Chanwoo , Kim Taeyun
Published: October 2020

Convolutional Neural Network (CNN) is, in general, good at finding principal components of data. However, the characteristic components of the signals could often be obscured by system noise. Therefore, even though the CNN model is well-trained and predict with high accuracy, it may detect only the primary patterns of data which could be formed by system noise. They are, in fact, highly vulnerable to maintenance activities such as reassembly. In other words, CNN models could misdiagnose even with excellent performances.

In this study, a novel method that combines the classification using CNN with the data preprocessing is proposed for bearing fault diagnosis. The proposed method is demonstrated by the following steps. First, training data is preprocessed so that the noise and the fault signature of the bearings are separated. Then, CNN models are developed and trained to learn significant features containing information of defects. Lastly, the CNN models are examined and validated whether they learn and extract the meaningful features or not.
Critical Conditions for Secondary Droplets Generated by Droplets Colliding Walls With Different Angles
Authors: Wu Yikai , Ju Wenxuan , Liu Yusheng , Zhao Fulong , Tan Sichao
Published: October 2020

The single droplet phase change model during motion is developed based on the phenomena description and mechanism comprehension, which including the droplet phase change model as well as the droplet motion model. Then, the calculation of the droplet phase change characteristics during moving in the uniform flow in the gravity separation space is conducted. The results show that when the droplet are evaporating during its moving, the radius will decrease continuously and it will be carried more easily by the steam vapor, which will lead to the larger separation radii of the droplets and the reduced the gravity separation efficiency. In addition, this paper shows the three-dimensional map for the critical separation over the pressure difference and the steam vapor flow velocity, which can contribute to forecast the influence of the droplet phase change on the separation characteristics. The results can be applied in the design of the steam-water separation plants.
Stress Analysis of the Pressurized-Water Reactor Control Rod Under Operating Conditions
Authors: Carrilho Leo A.
Published: October 2020

This work aims to develop a finite element model of a PWR control rod at operating conditions for stress analysis of the rod cladding. The finite element model simulates a control rod exposed to high operating temperatures and pressure while portions of the rod are irradiated, resulting in accumulated fluence of neutrons by the rod materials. These high temperature and accumulated fluence induce thermal expansion and swelling of the rod materials, especially of the absorber, which may eventually interact with the rod cladding, generating stresses and strains in the wall of the cladding tube. Moreover, if the maximum stress or strain in the tube wall exceeds the design allowable limit, the absorber rod is considered failed. The author creates the control rod finite element model and apply the operating loads on two-dimensional axisymmetric elements to obtain displacements, temperatures, stresses, and strains. The model also includes contact surface elements to evaluate eventual mechanical interactions between absorber and cladding due to thermal expansion and swelling effects. This is a coupled nonlinear static analysis solution that includes thermal expansion effects to calculate temperature distribution and subsequent thermal strains in the absorber rod due to the heat generation rates and coolant temperature; swelling analysis to calculate absorber growth induced by irradiation; and creep analysis to calculate absorber stress relaxation under coolant pressure and temperature. The finite element model is capable of determining whether or not absorber-to-cladding gap closure will occur and if so, calculate maximum stress and strain in the rod cladding associated with mechanical interaction between the two components induced by the operating temperature and thermal fluence loads.
Optimization Design for the Configuration Parameters of Helical-Coil Steam Generator Volume
Authors: Fang Hongyu , Wang Li , Zhu Dahuan , Cai Rong , Jiang Xiaowei , Zhang Dan , Qian Libo , Wu Dan
Published: October 2020

With the development of the nuclear energy industry, small modular reactors (SMRs) have become an important option in China’s energy development due to their advantages in terms of safety and economics. The helical-coil steam generator is an important part of SMR, and the structure parameters need to be optimized urgently to reduce costs and improve safety.

In this paper, various thermohydraulic parameters were used as indicators for the design quality of the helical-coil steam generator, such as the volume of the equipment, velocity of the flow, maximum temperature of the tubes, and natural circulation capability. The optimization of these target parameters has important theoretical and practical values. The genetic algorithm method is widely used to processes data efficiently, and it is able to reach a optimum design rapidly, which makes it a good choice for the optimization of parameters. The results show that this method could efficiently reduce the volume of the helical coil steam generator.
Anomaly Detection for Network Traffic of I&C Systems Based on Neural Network
Authors: Si Wen , Li Jianghai , Qu Ronghong , Huang Xiaojin
Published: October 2020

Anomaly detection is significant for the cybersecurity of the I&C systems at nuclear power plants. There are a large number of network packets generated in the network traffic of the I&C systems. There are many attributes of the network traffic can used for anomaly detection. The structure of the network packets is analyzed in detail with examples. Then, Features are extracted from network packets. An unsupervised neural network called autoencoder is applied for anomaly detection. Training and testing database are captured from a physical PLC system which simulates a water level control system. The result of the test results shows that the neural network can detect anomaly successfully.
Identifying the Cause of and Fixing Ill-Conditioned Matrices in Nuclear Analysis Codes
Authors: Larsen Lance C.
Published: October 2020

Many of the analytical codes used in the nuclear industry, such as TRACE, RELAP5, and PARCS, approximate the equations that model the physics via a linearized system of equations. One common difficulty when solving linearized systems is that an accurately formulated system of equations may be ill-conditioned. Ill-conditioned matrices can result in significant amplification of error leading to poor, or even invalid, results. Ill-conditioned matrices lead to some challenging issues for the analytical code developers:

• An ill-conditioned matrix is often solvable, and there may be no obvious indication numerically that something has gone wrong even though numerical error is large. Thus, how can ill-conditioning be effectively detected for a matrix?

• When ill-conditioning is detected, how can the source of the ill-conditioning be determined so that it can be analyzed and corrected?

Ill-conditioning is fundamentally a geometric problem that can be understood with geometric concepts associated with matrices and vectors. Geometric concepts and tools, useful for understanding the cause of ill-conditioning of a matrix, are presented. A geometric understanding of ill-conditioning can point to the rows or columns of the matrix that most contribute to ill-conditioning so that the source of ill-conditioning can be analyzed and understood, and leads to techniques for building matrix preconditioners to improve the solvability of the matrix.
Deposition Velocity and Penetration Efficiency in a Square Channel Using a Lagrangian-Based Modeling Approach
Authors: Choi Byung-Hee , Orea Daniel , Nguyen Thien , Anand N. K. , Hassan Yassin , Sabharwall Piyush
Published: October 2020

Texas A&M University is working on the development of gas cooled fast reactor cartridge loop under the Department of Energy VTR program. Our research project aims to develop and implement techniques to quantify the transport and deposition of particle inside the cartridge loop. Before the developed techniques are applied in a complicated actual facility, it is essential to verify and validate their performance using numerical simulations and to quantify their uncertainties. This article presents a numerical study of particle transport and deposition in a proof-of-concept facility.

The proof-of-concept facility houses a series of three square duct test sections, each of which has a cross-section of 3 in.2 and a length of 24 in., for a combined total length of 72 in. The numerical simulation domain is based on the geometrical dimensions of the experimental facility. The main stream in the channel is solved using the Eulerian turbulence model, and the particle motion is interpreted in the Lagrangian framework. It is assumed that a well-mixed air–particle mixture at a constant temperature is injected into the horizontal channel. Lagrangian simulations of surrogate particles allow us to understand their behavior precisely.

The Reynolds stress model is selected to reproduce the secondary flow and the associated secondary drag force. The state-of-the-art Lagrangian approach, in combination with a random walk model coupled with a computational fluid dynamics model, is employed to investigate the behaviors of the surrogate particles within the square channel. Gravitational settling is also considered.

The deposition velocity and penetration efficiency are estimated for representing the characteristics of particle deposition in the proof-of-concept facility. Because the conventional method of measuring the deposition velocity is based on the Eulerian framework, it is not suitable for direct adoption in the Lagrangian framework. This study proposes a numerical technique to measure the deposition velocity; this technique can be efficiently used in the Lagrangian framework of the simulation. The results agree well with both our experimental measurements and correlations available in the literature. Using this technique, the correlations for the deposition velocity are established as functions of the normalized channel length, Stokes number, and Reynolds number. Finally, the relationship between the deposition velocity and penetration efficiency is examined, and a correlation is proposed. Consequently, the penetration efficiency can be directly compared with several conventional reference data based on the deposition velocity.
Development of an Efficient Tool for Evaluating Dose at Through-Holes
Authors: Watanabe Tatsuya , Iwanami Hironobu , Hashimoto Tomoharu , Tayama Ryuichi
Published: October 2020

In the design of nuclear power plants, it is demanded to quickly and calculate gamma ray scattering line (streaming) from the penetrating portion provided in the shielding such as electrical cables and ducts.

However, when conducting gamma-ray streaming calculations from multiple penetrations, MCNP, a detailed calculation code, requires a long calculation time. This is due to the nature of MCNP, where many particles must reach the evaluation point when calculating in order for the results to be within an acceptable accuracy. To shorten the computation time, an analysis code utilizing a simple calculation method is necessary.

Thus, we have developed a new method and a simple calculation tool (SVD-Dorc) for streaming computation. This method combines dose rate at an evaluation point with point kernel integration method and a simple streaming calculation formula for straight cylindrical ducts. Properties of SVD-Dorc are as follows:

• Point kernel integration method

• Simple streaming calculation formula for straight cylindrical ducts

• Manual and automatic meshing of rectangular and cylindrical sources

• Differentiation between direct line and non-direct sources

• 3D drawing of input data

• File output

The validity of SVD-Dorc was confirmed by comparison with MCNP calculations and measured values from benchmark tests [2].
Investigation of the Structure Velocity in a 3x3 Rod Bundle Under Bubbly and Cap-Bubbly Flow Regimes
Authors: Ruan Pei-Syuan , Chen Shao-Wen , Lin Min-Song , Lee Jin-Der , Wang Jong-Rong
Published: October 2020

This paper presents the experimental results and analyses of the structure velocity of air-water two-phase flow in a 3 × 3 rod bundle channel. A total of 56 flow conditions were tested and investigated for rod-gap, sub-channel, rod-wall and global regions of rod bundle geometry. The experimental tests were carried out under bubbly and cap-bubbly flow regimes with superficial gas and liquid velocities of 0–1 m/s and 1–1.7 m/s, respectively. The conductivity probes were set at different heights to measure the global and local void fractions. The structure velocity of air-water two-phase flow is the average bubble velocity calculated by the method in this study. The structure velocity were determined by utilizing the cross-correlation technique to analyze the time lags of the bubbles passing through the conductivity probes. The results of this study indicated that the structure velocity may increase with increasing superficial gas and liquid velocities. In low superficial gas velocity region, the structure velocity may first slightly increase and follow by a sudden jump which appear in most regions. After the sudden jump, the structure velocity may keep increasing mildly. The present structure velocities have been compared with the area-averaged gas velocities predicted by the drift flux model, and it appears that most structure velocities show a good agreement with the averaged gas velocities from the drift flux model after the jump.
Thermal Fatigue of Pressurized Water Reactor Coolant System Loop Drain Line Down Horizontal Elbow
Authors: Zou Yue , Derreberry Brian
Published: October 2020

Thermal cycling induced fatigue is widely recognized as one of the major contributors to the damage of nuclear plant piping systems, especially at locations where turbulent mixing of flows with different temperature occurs. Thermal fatigue caused by swirl penetration interaction with normally stagnant water layers has been identified as a mechanism that can lead to cracking in dead-ended branch lines attached to pressurized water reactor (PWR) primary coolant system. EPRI has developed screening methods, derived from extensive testing and analysis, to determine which lines are potentially affected as well as evaluation methods to perform evaluations of this thermal fatigue mechanism for the U.S. PWR plants. However, recent industry operating experience (OE) indicate that the model used to predict thermal fatigue due to swirl penetration is not fully understood. There are limitations with the EPRI generic evaluation. In addition, cumulative effects from various thermal transients such as the reactor coolant system (RCS) sampling and excess letdown may also contribute to the failure of RCS branch lines. In this paper, we report direct OE from one of our PWR units where thermal fatigue cracking is observed at the RCS loop drain line close to the welded region of the elbow. A conservative analytical approach that takes into account the influence of thermal stratification, in accordance with ASME Section III Class 1 piping stress formula, is also proposed to evaluate the severity of fatigue damage to the RCS drain line, as a result of various transients. Finally, recommendations are made for future operation and inspection based on results of the evaluation.
The sound insulation and directivity of the sound radiation from double glazed windows
Authors: Cambridge Jason E. , Davy John L. , Pearse John
Published: October 2020

The sound insulation and directivity of the radiated sound from double glazed windows have been measured by different researchers. Previously, airborne sound insulation models have been used to predict the associated measurement results with limited success. In this paper, the importance of accounting for the structure borne sound transmission between two glazing elements via the window frame on the prediction results is demonstrated. The decreased stiffness of the wall cavity as the depth is increased is the reason why sound transmission via the window frame needs to be considered. The reciprocity argument provided by Davy for the prediction of the directivity of sound radiating into a room is validated and it is shown that once the structure borne transmission is considered, an additional weighting term is not needed to compensate for the extra wall collisions which the sound experiences when radiated at grazing incidence.
Reverberation reduction based on multi-ping association in a moving target scenario
Authors: Zhu Yunchao , Duan Rui , Yang Kunde , Xue Runze , Wang Ning
Published: October 2020

Conventional reverberation reduction methods are conducted with single-ping data and may fail in a low signal-to-reverberation ratio (SRR) environment. To improve the performance of reverberation reduction, multi-ping data are fully considered in this paper. The reverberation can be treated as a combination of the steady component of reverberation and reverberation fluctuations, and then an alternating direction multiplier method is proposed to reduce the steady component of the reverberation. By exploiting the evolution of the target location along multiple pings, the reverberation fluctuation is reduced by the probabilistic data association method. The proposed method was verified by the field data, and the results show that compared with the accelerated proximal gradient method, the sparse coefficient is improved by a factor of 1.23, and the signal excess is improved by an average value of 2.0 dB. In addition, the performance of the proposed method is found to be closely related to the signal-to-reverberation-fluctuation ratio rather than only the SRR.
Aggregation as the Remedy for the Decline of Niche Sports Broadcasting: A Case Study of the European Championships
Authors: Meier Henk Erik , Hagenah Jörg , Jetzke Malte
Published: October 2020

As Hutchins and Rowe have emphasized, digital plenitude will fundamentally affect sports broadcasting. In particular, niche sports will be confronted with a more difficult media environment in which the chances of being telecast may increase, while the chances of finding an audience are likely to decrease. Therefore, niche sports face the need to further submit to a media logic. The current research is a case study involving an analysis of the 2018 European Championships from a mediatization perspective. While the findings show how aggregation helped to revitalize audience interest, the case study reveals that the future of niche-sport broadcasting is uncertain, because the audience habits that the European Championships exploited are fading.
Eight-Week Inspiratory Muscle Training Alters Electromyography Activity of the Ankle Muscles During Overhead and Single-Leg Squats: A Randomized Controlled Trial
Authors: Gholami-Borujeni Behnam , Yalfani Ali , Ahmadnezhad Leila
Published: October 2020

This study was conducted to evaluate the effects of 8-week inspiratory muscle training on activity in the ankle muscles of athletes with chronic low-back pain. A randomized controlled trial involving 45 men and women with chronic low-back pain was carried out. Electromyography activity in the tibialis anterior, peroneus longus, gastrocnemius medialis, and gastrocnemius lateralis muscles of the dominant leg was recorded. Secondary outcomes included biopsychosocial indices, such as pain, disability, anxiety and depression, fear-avoidance beliefs, and fear of (re)injury. Static and dynamic overhead squat tests showed that inspiratory muscle training decreased activity in the tibialis anterior, peroneus longus, and gastrocnemius medialis muscles. In the static single-leg squat test and the descending phase of the dynamic equivalent, such a decrease was observed in all the 4 muscles. Inspiratory muscle training significantly reduced pain severity and activity in the tibialis anterior, peroneus longus, and gastrocnemius medialis muscles during the ascending phase of the dynamic single-leg squat test. On the basis of the findings, 8 weeks of inspiratory muscle training may constitute useful rehabilitation for reducing excessive activity in ankle joint muscles and aiding chronic low-back pain recovery.
Encouraging “Active Learning”: Assessing Implementation of Head Start’s Physical Activity Requirements Within the Teaching and Learning Environment
Authors: Slater Sandy J. , Sanghera Anmol , Herrera Yadira , Chriqui Jamie F.
Published: October 2020

Background: Head Start serves over 1 million diverse low-income preschool children and is an ideal setting for developing and implementing obesity prevention efforts, which is expected to have positive impacts on behavior as youth age. This study examined how regional- and state-level Head Start offices have supported implementation of the recently updated physical activity (PA) requirement within the teaching and learning environment Head Start Program Performance Standard (1302.31).Methods: Key informant telephone interviews were conducted with 8 regional- and 36 state-level Head Start representatives. Interviews were recorded and professionally transcribed. Data were coded and analyzed using constant comparative methods in ATLAS.ti (version 8). Audit trails were maintained, and disagreements in codes were discussed and resolved among coders.Results: The following 3 overarching themes emerged: communication, resources and technical assistance, and challenges. Results showed variation in respondent knowledge regarding the Standards. Although regional contacts provide technical assistance, state-level contacts have many information sharing strategies for programs. Implementation challenges included the need for frequent professional development opportunities given staff turnover and low PA competency, and additional PA curricula.Conclusion: Findings can help identify existing or potential strategies that could be adopted more widely or developed to assist Head Start programs incorporate PA into daily activities.
Comparison of Trunk Flexion Proprioception Between Healthy Athletes and Athletes With Patellofemoral Pain
Authors: Heydari Armaki Reza , Abbasnia Keramatollah , Motealleh Alireza
Published: October 2020

Objective: Patellofemoral pain (PFP) is the most commonly reported musculoskeletal overuse injury in active individuals, such as athletes, and is a multifactorial problem with no definite cause identified to date. Some studies have shown a relationship between impaired core and trunk sensorimotor control and knee disorders, especially PFP. The aim of this study was to evaluate trunk flexion proprioception by comparing the repositioning error between healthy athletes and athletes with PFP. Design: Cross-sectional case–control study. Setting: Rehabilitation sciences research center. Participants: Twenty healthy athletes and 20 athletes with PFP. Main Outcome Measures: To examine proprioception of trunk flexors, the absolute active and passive repositioning error at 30° and 60° trunk flexion were evaluated with isokinetic dynamometry. The results were compared between the two groups. Results: In the PFP group, the active trunk repositioning error at 30° flexion was significantly greater than in the healthy individuals (P < .001). The mean absolute active repositioning error at 30° flexion was 3.04° (1.37°) in the PFP group and 1.50° (0.70°) in the control group. There was no significant difference between groups in the active trunk repositioning error at 60° flexion (P = .066). The mean absolute active repositioning error at 60° flexion was 2.96° (1.26°) in the PFP group and 2.18° (0.99°) in the control group. The passive trunk repositioning error at 30° and 60° flexion was significantly greater in the PFP group (P = .013 and P = .004, respectively). The mean absolute passive repositioning error at 30° and 60° flexion in the PFP group was 2.94° (0.80°) and 3.13° (1.19°), respectively, and was 2.08° (1.08°) and 1.96° (0.71°), respectively, in the control group. The calculated eta-squared value showed that joint repositioning errors had large effect sizes (0.15–0.32). Conclusion: Trunk proprioception in the flexion direction may be impaired in patients with PFP. This finding suggests that trunk proprioception training may be important in rehabilitation for athletes with PFP.
The Effectiveness of Isometric Contractions Compared With Isotonic Contractions in Reducing Pain For In-Season Athletes With Patellar Tendinopathy
Authors: Vang Chee , Niznik Alexander
Published: October 2020

Clinical Scenario: Patellar tendinopathy is a common musculoskeletal disorder affecting the lower-extremities and a difficult condition to manage for athletes that are in season. To facilitate improvement in function and to decrease pain, initial treatment for patellar tendinopathy is typically conservative. Traditional interventions may include eccentric training, cryotherapy, patellar counterforce straps, oral anti-inflammatories, injectable agents, phonophoresis, iontophoresis, orthotics, therapeutic ultrasound, and extracorporeal shockwave. In addition, recent literature suggests that implementing isometric and isotonic contractions may be effective in reducing patellar tendon pain. Focused Clinical Question: How effective are isometric contractions compared with isotonic contractions in reducing pain for in-season athletes with patellar tendinopathy? Summary of Key Findings: Implementation of isometric and isotonic exercises statistically reduced pain levels in the short term of 4 weeks for in-season athletes; however, isometric contractions provided statistically greater pain relief immediately for up to 45 minutes postintervention compared with isotonic contractions. Clinical Bottom Line: Current evidence supports the use of isometric and isotonic contractions to reduce pain for in-season athletes with patellar tendinopathy. Based on the reviewed literature, clinicians should consider utilizing heavy loaded isometrics or progressive heavy loaded isotonic exercises, which showed reduction in pain levels immediately after intervention and at 4-week follow-up for both intervention groups. Isometric contractions appear to provide greater pain relief immediately after intervention. Strength of Recommendation: There is Grade B evidence from 2 level 2 randomized controlled trials and 1 level 3 randomized crossover study supporting the use of isometric and isotonic contractions to reduce patellar tendon pain for in-season athletes.