bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling and Analysis of Loviisa NPP Pilot Operated Main Steam Safety Valves
Authors: Juntti Mika 
Published: October 2017

Loviisa NPP (unit 2) low pressure Main Steam Safety Valves (MSSV) were renewed during 2014 overhaul. New valves are pilot operated and qualified for two phase conditions. The old valves were spring loaded and qualified only for steam flow conditions.
During the testing of new MSSVs, unexpected behavior was detected. The opening of new MSSV included significant delay in case of repeated openings. This led to a need to investigate this phenomena more closely since such opening delay could have negative impact to plant safety.
This paper presents the aftermath of the discovered opening delay in the NPP and describes how thermal hydraulic modelling and analyses were used to gain in depth understanding of pilot operated MSSV. In addition, it is presented how the analysis work was used to solve the discovered challenges.
Modelling work was conducted using Apros Process Simulation Software [1] which is the main tool for deterministic safety and engineering analysis of Loviisa NPP [2–4].
An Advanced Method for Evaluating Risk From Seismically-Induced Internal Fires and Floods
Authors: Amico Paul J. , Macheret Pierre , Kassawara Robert P. 
Published: October 2017

It has been traditional in assessment of nuclear power plant safety that both deterministic safety analyses and probabilistic safety analyses treat the potential effects of various hazards individually. That is, the safety implications of internal events (e.g., randomly occurring transients and LOCAs), internal hazards (e.g., internal fire and flood), and external hazards (e.g., earthquakes, tornados) are treated as independent occurrences. With the occurrence of the Great Tohoku earthquake and the effects observed at nuclear plants in Japan, it was realized that this approach failed to provide a realistic representation of risk, and now there is a significant interest in correlated hazards.
As a result, EPRI embarked on the development of an improved methodology focusing on seismically-induced internal fires and internal floods. All the technical work on the methodology has been completed and draft technical guidance developed. This guidance has been provided to some plants that are interested in piloting the methodology. As of the date of paper submittal, two pilots are underway and three more are under consideration. Upon completion of the pilots, the methodology will be updated to incorporate the lessons-learned and published.
Development and Comparison of a Heat-Transfer Correlation for Supercritical Refrigerants
Authors: Tarsitano Nicholas , Sidawi Khalil , Pioro Igor 
Published: October 2017

The objective of this paper is to act as a collection of multiple different heat-transfer correlations and to check their accuracy when compared to experimental data obtained in supercritical-pressure refrigerants (R-22 and R-134a). This paper is also intended to collect as much relevant data of heat transfer in supercritical refrigerants as possible for future research. The experimental data have been retrieved from graphs within a wide range of operating parameters. This study is in support of potential use of supercritical refrigerants as modeling fluids instead of supercritical water. The use of refrigerants as modelling fluids instead of water will allow to decrease costs and technical difficulties during experiments at supercritical pressures and widen operating ranges, because the critical parameters of refrigerants are significantly lower than those of water.
The research was completed by collecting graphed data from several different experimental series using both R-22 and R-134a data. The advantage of comparing different refrigerants for determining correlation accuracy is to increase the predictability for other potential experiments using refrigerants. All data are taken from bare-tube experiments to produce a relative baseline for heat-transfer characteristics. These experiments have been performed within the following range: Inner tube diameter ranging between 4.4 mm to 13 mm, pressure ranging between 4.3 MPa to 5.5 MPa, and at a number of various mass and heat fluxes. Sixteen potential heat-transfer correlations have been selected and used in this assessment. The correlation by Watts and Chou [1] and Cheng et al. [2] were shown to have the lowest root-mean-square error. Other correlations with the reasonable accuracy include Mokry et al. [3] and Swenson et al. [4] correlations. However, it was decided to develop a new correlation based on these refrigerant data in an attempt to increase the prediction accuracy.
Therefore, based on the Mokry et al. [3] correlation a modified correlation was developed, which generalized the experimental Freon data with higher accuracy than the know correlations. This correlation is intended to create a basis for further study on the use of refrigerants as modeling fluids. While Freon has similar properties to water at supercritical conditions, the different molecular properties causes factors to affect each fluid differently. For refrigerants at supercritical conditions, the factors that seem to have the most effect are the dynamic viscosity and density of a fluid.
Studies on Sensitivity and Uncertainty Analyses for SCOPE and WAFT With Uncertainty Propagation Methods
Authors: Zhangli Wang , Benxue Hu , Guodong Wang , Zhe Wang , Chenxiao Ni , Xin Liu 
Published: October 2017

The purpose of Steam condensation on cold plate experiment facility (SCOPE) and Water film test (WAFT) is to verify the steam condensation and water film evaporation correlation within the parameter variation range of CAP1400 passive containment cooling system. These correlations were used for containment response analysis. Uncertainty and sensitivity analyses were performed for SCOPE and WAFT tests in this paper.
Sampling-based sensitivity analysis with uncertainty propagation is a new parameters sensitivity analysis method, and the importance of input parameters could be evaluated by calculating the correlation coefficients between input parameters and the output target parameter. This method was used to acquire the influence of the measured input parameters uncertainty on the output target parameter. The results show that air and steam flow rate, coolant flow rate, inlet and outlet water temperature are the main source of the uncertainty for SCOPE. Inlet film flow rate, inlet air flow velocity and plate surface temperatures are the main source of the uncertainty for WAFT. Sensitivity analysis results may provide support for experiment measurement system optimization to reduce the target parameter error range.
Uncertainty analysis is one important aspect of test data analyses, which is meaningful to the assessment of test results. Conventionally the partial derivative with respect to the input parameters is used to transfer uncertainty from the input parameters to the output parameter. However, in this method the partial derivatives of the output parameter sub the input parameters must be calculated. For complex engineering problems, it is usually difficult to acquire theoretical correlations for the partial derivatives. WILKs formula is used to determine the parameter tolerance interval with certain probability content and confidence level. The tolerance interval is a good way to well describe the uncertainty of parameters. The nonparametric statistics with WILKS correlation were widely used in the best-estimate plus uncertainty (BEPU) accident analyses. However, little work has been conducted on the experiment results uncertainty analysis with that method. In this paper nonparametric statistics with WILKS correlation was used to acquire key parameters uncertainty. And the results show that key output parameters uncertainty for SCOPE and WAFT are within the reasonable range.
Uncertainty Propagation Methods were implied for test results Sensitivity and Uncertainty Analysis in the paper, which may be conveniently applied to the other experiment data analyses and also valuable to the engineering project.
Research and Design of the Sodium Steam Filter System in Large Liquid Metal Cooled Fast Reactors
Authors: Leijian Wang , Yuan Lu , Changzhi Xiao 
Published: October 2017

This reactor uses liquid sodium as coolant owing to its good thermal physical properties, high boiling point and compatibility of cladding material. However, the sodium has a very active chemical properties, for which the free surface of sodium must be protected by inert gas. In the high temperature environment, the sodium atoms diffusion to cover gas slowly, forming a mixed atmosphere that contained large amount of sodium steam.
Sodium steam is covered with the free surface of sodium. Then metal sodium will solidify in the inner wall of the pipe or correlative valves with the reduced temperature. This reactor needs to collect and filter sodium steam in order to reduce the hazards to the equipment, piping system, valves and the other devices. Based on the previous research about the purification process of sodium, this paper compared different steam trapping filtration process and carried out the thermal calculation providing basis for research and design of large sodium cooled fast reactor sodium steam trapping filtration process and establishing a reliable sodium steam filtering system.
The Behavior of Aerosol Particle Inside a Rising Bubble During Pool Scrubbing
Authors: Fujiwara Kouta , Abe Yutaka , Kaneko Akiko , Yamamoto Kazuki 
Published: October 2017

In severe accidents of nuclear power plants such as the Fukushima Daiichi Unit 1 accident, aerosol containing massive amount of Fission Products (FP) could be created. Pool scrubbing is an effect of capturing these FP inside the water during the flow of aerosol. Such a situation may occur at the vent of containment vessel in the BWR as well as the heat-transfer-tube disrupted accident of steam generator in the PWR. The amount of FP released into the atmosphere could be reduced by the effect of pool scrubbing. Hence, the removal of aerosol by pool scrubbing is expected to evaluate the source terms stated below.
Although the importance of pool scrubbing has been recognized, the study for its mechanisms from the viewpoint of particle-bubble and two phase flow had not been carried out intensively. Furthermore, lack of experimental data for various conditions should be improved. Such a state leads to prevent us from analyzing the efficiency of pool scrubbing when advancing the model and testing the validation of it.
The aim of this study is to clarify the transfer of aerosol and bubble experimentally. The data from the experiment evaluates the influence of each parameter to remove the FP. The analysis code presently used adopts the model for the velocity which affect the particle to go out from the bubble. Each of them are written as (i) centrifugal deposition velocity, (ii) gravitational velocity, (iii) incoming vapor velocity, (iv) Brownian diffusion velocity. We choose our parameter which correspond to each of the velocities. Remarking that the experiment also include conditions e.g. the temperature stratification, the types of particle and gas, which is not been described in the manual. Based on the experimental result, our goal is to test validation and improve the model appropriate to the severe accidents predictive code such as the MELCOR by reflecting the study of flow mechanism and the effect of various conditions. To the end, this paper focuses on the rotation and its movement of aerosol particles inside the bubble.
This study focuses on the behavior of a single air bubble including aerosol by visualizing the inner flow of bubble containing particle. As a result for visualization of a single rising bubble, we were able to take a film of an area inside the particle where information of particle movement is seen. We also succeed in observing a clockwise rotation flow inside bubble just above the nozzle. As to avoid the refraction between air-water, we also made an experiment against rising oil droplets. From the series of experiment, the growth of upward flow from desorption to the stationary rising mode was been seen inside the droplet. As the flow grew, a top-to-bottom rotation was seen as it was mentioned in previous models.
Machine GTAW Ambient Temperature Temper Bead Technique for Ni-Based Weld Overlay Repairs of Nuclear Components: Assessment of Hydrogen Cracking by Implant Test
Authors: Consonni Marcello , Verdon Claire 
Published: October 2017

Repair by welding of a metallic component may be required during original fabrication, following in-service inspection or during planned maintenance operations. In some instances a post-weld heat treatment (PWHT) is required. Codes/standards that cover the repair of or alterations on nuclear components, such as Section XI of the ASME Boiler & Pressure Vessel code or the French RSE-M nuclear code for in-service inspection, include provisions for waiving the need for a PWHT by using a welding technique referred to as ‘temper bead’, but in the case of in-service repairs, the practical challenges may make any heating cycles, including pre or post-heating, undesirable. So, starting from the existing temper bead procedures, repair solutions that do not require preheat, PWHT or post-heating, have been developed, particularly in the nuclear sector, referred to as ‘ambient temperature temper bead’ (ATTB).
One of the most common applications of the ATTB technique is the deposition of full structural weld overlays (FSWOLs), made with Ni-based consumables on ferritic base materials, to repair piping components and nozzles susceptible to primary water stress corrosion cracking (PWSCC) and to mitigate the risk of further cracking. The ATTB technique is currently permitted for the repair of nuclear power plant components by the ASME code via Code Cases N-638-8 and N-740-2, provided the machine gas tungsten arc welding (GTAW) process is used, and it has been successfully applied on various occasions. However, the technique is currently not permitted by the RSE-M code. As the current rules in the RSE-M codes were established following experimental programs based on implant testing, the same type of tests would be expected by the French nuclear regulator to justify any changes. This paper presents the results of a research project carried out to explore the possibility of justifying the introduction of ATTB using the machine GTAW welding process to deposit austenitic weld overlays into the RSE-M code, based on implant testing. Externally loaded tests according to ISO 17642-3 (Implant test) were carried out to determine the effect of different preheat and stress levels on the cold cracking susceptibility in the parent metal. Test loads representative of actual residual stresses were determined through a review of published literature on the residual stresses associated with ATTB FSWOLs. Test pieces were obtained by depositing single beads with Inconel 52 filler metal (AWS A5.14 ERNiCrFe-7) on ASME SA 508 Grade 4N substrate. Conclusions are presented with regard to the possibility to waive preheat or to reduce the minimum preheat temperature specified for temper bead repairs, with respect to the current RSE-M code requirements. Recommendations for further work required to support a request for modification of the RSE-M code are provided.
Analysis of Sustainable Thorium Fuel Utilization in Molten Salt Reactors Starting From Enriched Uranium
Authors: Cui Deyang , Cai Xiangzhou , Chen Jingen , Yu Chenggang 
Published: October 2017

Molten salt reactor (MSR), as one of the six systems selected by the Generation IV International Forum (GIF) for future advantaged reactors research and development (R&D), has excellent performances such as high inherent safety, desirable breeding capacity, low radioactive waste production, flexible fuel cycle and non-proliferation. Meanwhile, thorium, as an appealing alternative nuclear fuel to uranium, is more abundant than uranium in the earth’s crust. Realization of thorium fuel cycle in MSRs will greatly contribute to sustainable energy supply for global development. The objective of this paper is to analyze and evaluate thorium fuel utilization in a program in which MSRs are expected to be developed step by step. The program can be described as follows:
1 The first stage is a converter reactor fueled with low enriched uranium. With limited processing based on current chemical partitioning technology and fuel-feeding techniques in the generation-I MSR;
2 The second stage is a 233U production reactor. By using the enriched uranium, it can produce 233U which does not exist in nature;
3 The third stage is a thorium breeding reactor. It is a breeder reactor with Th/233U fuel cycle, and sustainable thorium utilization for energy production is expected to be eventually realized.
By employing an in-house developed tool based on SCALE6.1, the performance of MSR fueled with low enriched uranium is firstly assessed. It is found that MSR is attractive regarding conversion ratio when compared with light water reactors. Then we illustrate the feasibility of 233U production in MSR. Enriched uranium with two enrichments are used as driver fuels to start MSR and produce 233U. The results show that 233U production can be achieved and the double time is about 79.1 years for 20% enriched uranium and 28.3 years for 60% enriched uranium. Finally, the performance of MSR based on pure Th/233U fuel cycle is evaluated. It is found that breeding fissile material is possible in MSR and the breeding ratio is desirable (1.049). Comparison of the three-stage MSRs is also conducted and the results indicate that the resource utilization efficiency is much higher in stage-III than that in the first two stages and much less minor actinides is produced in MSR operating on Th/233U fuel cycle than that in traditional light water reactor.
Effect of Thin Metal Film and Micro Structure of Surface on Condensation Pattern
Authors: Nishimura Tomohito , Mikoshiba Yuki , Ohtake Hiroyasu , Hasegawa Koji 
Published: October 2017

The water condensation is important for wide range of industrial systems such as condensers and heat exchangers of steam power plants and refrigerators. The condensation generally has two patterns; filmwise condensation (FWC) and drop-wise condensation (DWC). DWC has one-tenth higher heat transfer coefficient than that of FWC. It has been pointed out by many investigators that DWC occurs on the hydrophobic surface and FWC occurs on hydrophilic surface. However, the durability of those hydrophobic effects was not clear enough. In order to maintain a sufficiently long DWC, it is important to understand the effect of the surface property and structure on the condensation surface in more detail. The recent advancement of MEMS (Micro Electro Mechanical System) technology enables us to change the physical nature the surface in the micro scale. It is expected that the hydrophobic surface by the MEMS technology may kept DWC for a longer time. In the present paper, we experimentally investigate the effects of thin metal film and micro structured surface on condensation pattern. Especially, our condensation experiments were performed with the micro structured surfaces by using etching and the metal thin film surfaces by sputtering for approximately 24 hours. Silicon (Si) wafer was used as a basic surface. For the metal thin films surface, we used sputtered Lead (Pb) and Titanium (Ti) on Si surface. For the micro structured surfaces, micro-structured grid was etched on Si surface with several conditions. In order to obtain the relation between the condensation pattern and surface condition, the surface conditions were measured by laser micro-scope, contact angle meter and atomic force microscope (AFM).
For the metal thin films surface, condensation patterns on thin Pb film surface showed DWC. Meanwhile, condensation patterns on thin Ti surfaces showed FWC. From our results, the adsorption forces decreased with increasing contact angle on DWC for Pb. On the other hand, the adsorption forces increased with decreasing contact angle on FWC for Ti. For the micro structured surfaces, condensation pattern was FWC and contact angle decreased in our experimental results. This is because that the condensed water is accumulated in the groove on the micro structure surface.
Experimental and Numerical Study of Airflow Dynamics Through an Opening in a Depressurized Enclosure: Application to Nuclear Decommissioning
Authors: Kaissoun Salima , Climent Eric , Prevost Corinne , Ricciardi Laurent 
Published: October 2017

In order to understand airflow dynamics through small openings encountered in containment enclosures used for nuclear decommissioning operations, the results of experimental and numerical investigations are analyzed.
The main purposes of this work are to identify the required conditions likely to generate flow inversions at the studied opening which lead to pollutant leakage outside depressurized enclosures, and also to verify the ability of CFD1 simulations to predict these flow inversions by using U-RANS2 and LES3 approaches. All along this work, we tried to reproduce the conditions of leakage occurring at the opening in terms of aerodynamics and openings geometries.
Laser flow visualizations and CFD results show that an additional flow, such as a turbulent jet in competition with the directional flow and a disturbed level of pressure inside the enclosure are among the main causes leading to the leakage through the opening.
Review on Mechanical Design of Printed Circuit Heat Exchangers
Authors: Zhang Xiaoqin , Shi Shanbin , Christensen Richard N. , Sun Xiaodong 
Published: October 2017

As a critical component in the advanced non-light water nuclear power plants with indirect power cycles, an intermediate heat exchanger (IHX) is used to transfer the heat from the primary coolant system to the secondary system. Generally, such reactors are operated at very high temperatures and pressures. Therefore, IHXs are required to be able to provide high thermal effectiveness while withstanding demanding operating pressure and temperature combinations. A suitable IHX candidate needs to possess high mechanical integrity.
One of the promising IHX candidate is Printed Circuit Heat Exchangers (PCHEs). The compact diffusion-bonded PCHEs are characterized by mini- or micro-flow channels photo-chemically etched on flat metal plates. These etched plates are stacked up and diffusion-bonded to form a monolithic block. Therefore, the mechanical integrity of PCHEs are centered on the mechanical design of these etched flow channels.
To date, there are several flow channel geometries developed for PCHEs. Straight and zigzag channels, the first two designs, can be often seen in Heatric-manufactured PCHEs in compliance with ASME codes to ensure the mechanical integrity. To improve the fluid flow and heat transfer capability and reduce the associated pressure drop, straight and zigzag channels evolve to other two variants: S-shaped fin and airfoil fin channels. However, since the surface geometry of the flow channels become significantly complicated, the ASME code is not applicable any longer. Numerical simulation is then required to analyze the mechanical strength of the evolved flow channels under extremely harsh operating conditions.
This paper provides a review on the mechanical design of PCHEs with straight and zigzag channels, which refers to the ASME Boiler and Pressure Vessel Codes. In addition, numerical simulations of the mechanical stress for a case study of S-shaped fin will be presented with Inconel 617 as the construction material. Research plans at the Ohio State University are also presented. The aim of this paper is to summarize the common mechanical design method for PCHEs as well as introduce some of the ongoing research work related to the mechanical strength analysis of complicated flow channels with the aid of computer simulation.