bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments and Simulations on the Steady-State and Transient Behavior of Gas/Liquid Interfaces in Impulse Pipes for Hydrostatic Level Measurements
Authors: Schulz Stephan , Hampel Rainer
Published: October 2013

For Boiling Water Reactors (BWR) and steam generators, the water level is a safety-relevant process variable. The most commonly applied measuring method is based on the calculation of the liquid level from geodetic pressure differences to a reference column of defined height and density. However, transition processes occurring under operational and accident conditions may lead to dynamic changes in the reference level and therefore to fluctuations in the differential pressure signal.

This paper presents experiments and numerical simulations on the steady-state and transient behavior of gas/liquid phase boundaries in “Zero Chamber Level Vessels” (ZCLV). In these slightly inclined miniature tubes, the constant reference level is provided by surface tension forces and the capillary effect, respectively.

To investigate the basic topology of gas/liquid interfaces under simplified conditions (environmental parameters, no heat transfer), a test facility with optical access was developed. The construction allows for variations of the inner tube diameter, inclination angle and liquid mass flow rate, respectively. By this means, experiments on phase boundaries were carried out for ethanol/air and water/air. The results provide information about the impact of geometry parameters and their interactions on the interface topology. In addition, the dynamic draining of excess liquid mass at the free end of the tube and at artificial weld seams, which is supposed to be the reason for temperature fluctuations observed in ZCLV during power operation of BWR, was experimentally analyzed.

The measurements represent the basis for an experimental validation and optimizations of the numerical flow code ANSYS CFX 12.0. In the next step, water/vapor phase boundaries at 286 °C and 70 bar will be investigated by applying x-ray radiography to a scale model. The results will be discussed in context with the hydrostatic level measurement in BWR.
Pressure Drop and Flow Pulsation in Tight-Lattice Rod Bundle
Authors: Lee Chi Young , Shin Chang Hwan , Park Ju Yong , Oh Dong Seok , Chun Tae Hyun , In Wang Kee
Published: October 2013

In order to ensure the compactness and high-power density of a nuclear power reactor, the research on tight-lattice fuel bundle, with a narrow gap distance between fuels, has been highlighted. Recently, KAERI (Korea Atomic Energy Research Institute) has been developing dual-cooled annular fuel to increase a significant amount of the reactor power in OPR1000 (Optimized Power Reactor), a PWR (Pressurized Water Reactor) optimized in the Republic of Korea. The dual-cooled annular fuel is configured to allow a coolant flow through the inner channel as well as the outer channel. To introduce the dual-cooled annular fuel to OPR1000 is aiming at increasing the reactor power by 20% and reducing the fuel-pellet temperature by 30%, as compared to the cylindrical solid fuel, without a change in reactor components. In such a case, due to larger outer diameter of a dual-cooled annular fuel, the dual-cooled annular fuel assembly exhibits a smaller P/D (Pitch-to-Diameter ratio) than the conventional cylindrical solid fuel assembly. In other words, the dual-cooled annular fuel array becomes the tight-lattice fuel bundle configuration, and such a change in P/D can significantly affect the thermal-hydraulic characteristics in nuclear reactor core.

In this paper, the pressure drop and flow pulsation in tight-lattice rod bundle were investigated. As the test sections, the tight-lattice rod bundle of P/D = 1.08 was prepared with the regular rod bundle of P/D = 1.35. The friction factors in P/D = 1.08 appeared smaller than those in P/D = 1.35. For P/D = 1.08, the twist-vane spacer grid became the larger pressure loss coefficients than the plain spacer grid. In P/D = 1.08, the flow pulsation, quasi-periodic oscillating flow motion, was visualized successfully by PIV (Particle Image Velocimetry) and MIR (Matching Index of Refraction) techniques. The peak frequency and power spectral density of flow pulsation increased with increasing the Reynolds number. Our belief is that this work can contribute to a design of nuclear reactor with tight-lattice fuel bundle for compactness and power-uprate and a further understanding of the coolant mixing phenomena in a nuclear fuel assembly.
An Addendum: Probabilistic Failure Analysis of a Residual Heat Removal Heat Exchanger During Postulated Loss of Coolant Accident
Authors: Solom Matt , Pannier Christopher , Chance Christopher , Seager Robert , Lee Alan , Green Jordan , Duong Tam , Alicea Paola
Published: October 2013

The previous work analyzed Residual Heat Removal System (RHRS) heat exchanger pressure tube failure probabilities, which were calculated using a Monte Carlo simulation. In the analysis, Probabilistic Fracture Mechanics (PFM) was used along with a Monte Carlo Simulation (MCS) to estimate the failure probability of the pressurized tubes within the heat exchanger. The Monte Carlo simulation was first conducted in MATLAB. It has been rewritten in FORTRAN, now calculating the flow rate for each failed tube out of one million trials and outputs the flow rates with their respective initial flaw dimensions. But more importantly, this program calculates the probability of a single tube failure in the RHR heat exchanger. The results from FORTRAN are consistent with those of the earlier analysis in MATLAB, validating the previous findings. While the earlier study found that tube failure was expected to be improbable for straight tubes, questions remained regarding the model’s applicability to curved sections of tubing. This additional analysis addressed those questions. The analysis focused on comparing the stress and displacement developed between the curved section of flawed a U-tube and a flawed straight tube using SolidWorks. The results from this analysis are beneficial for further understanding of the stress distribution in RHR heat exchanger tubing.
Response Functions of a Boron-Loaded Plastic Scintillator to Neutron and Gamma Radiation
Authors: Khan Nafisah , Ali Muhammad , Hosny Ahmed , Machrafi Rachid
Published: October 2013

A boron-loaded plastic scintillator has been investigated for possible use in neutron spectrometry. The sensor composition of hydrogen and carbon leads to multiple scattering collisions that are useful for fast neutron spectroscopy, while its boron component can serve as a thermal neutron detector. Both simulation and experimental work have been carried out to investigate the response functions of the detector to neutrons and gamma radiation. The response functions of the detector have been simulated using Monte Carlo N-Particle eXtended code. For experimental tests, the sensor has been mounted on a photomultiplier tube connected to a compact data acquisition system. The system has been tested in different gamma and neutron fields at the University of Ontario Institute of Technology Neutron Facility. The simulation and experimental results have been compared and analyzed.
The Advantages of Using Hydraulic Coupling Bolts Over Standard Fitted Bolts in Steam Turbine Flange Couplings
Authors: Kennedy Tom
Published: October 2013

Every turbine engineer has encountered the nightmare situation in which during an outage, fitted bolts get stuck in the turbine flange holes. This will mean having to jack the bolts out resulting in valuable loss of time, damage to holes and the need for replacement fitted bolts.
A Probabilistic Assessment of Flow-Accelerated Corrosion Rate in Pipe Bends With Unknown Initial Thickness
Authors: Pandey M. D. , Lu D. , Riznic Jovica
Published: October 2013

In CANDU reactors, the feeder pipe system supplies the primary coolant from the reactor core to steam generator. The flow-accelerated corrosion (FAC) of the extrados of the first bend of the outlet feeder is a life limiting factor. Therefore, accurate prediction of FAC rate is needed to determine the scope of inspection and replacement of feeder pipes during an outage. To estimate the FAC rate, the initial wall thickness of the extrados of the bend is required. However, initial wall thickness is not known precisely, because the bending of pipe during installation causes the thinning of extrados section. Another difficult is the sizing error or noise in the wall thickness measurements introduced by the inspection probes.

The objective of this paper is to develop a sound probabilistic method for the FAC rate estimation considering uncertainties in the initial wall thickness of bend and the sizing error (or noise). A Bayesian model is developed and applied to predict the end of life of the outlet bend on a risk-informed basis. A practical case study is presented to illustrate the use of the proposed method.
Molecular Dynamics Simulations to Evaluate the Effect of the Difference in Material Properties on Irradiation-Induced Defect Formation Under Applied Strain
Authors: Horinouchi Toshihiro , Miyashiro Satoshi , Itakura Mitsuhiro , Okita Taira
Published: October 2013

The influence of applied strain on the defect production rate during a cascade process was evaluated for several FCC metals with different Stacking Fault Energy by the method of molecular dynamics. It was found that applied strain increases the number of surviving defects, which is caused by the enhanced formation of larger clusters. It was also found that the number of defects is almost independent of Stacking Fault Energy even under applied strain.
Boiling Heat Transfer and Critical Heat Flux Enhancement of Upward- and Downward-Facing Heater in Nanofluids
Authors: Sulaiman Muhamad Zuhairi , Takamura Masahiro , Nakahashi Kazuki , Okawa Tomio
Published: October 2013

Boiling heat transfer (BHT) and critical heat flux (CHF) performance were experimentally studied for saturated pool boiling of water-based nanofluids. In present experimental works, copper heaters of 20 mm diameter with titanium-oxide (TiO2) nanocoated surface were produced in pool boiling of nanofluid. Experiments were performed in both upward and downward facing nanofluid coated heater surface. TiO2 nanoparticle was used with concentration ranging from 0.004 until 0.4 kg/m3 and boiling time of tb = 1, 3, 10, 20, 40 and 60 minutes. Distilled water was used to observed BHT and CHF performance of different nanofluids boiling time and concentration configurations. Nucleate boiling heat transfer observed to deteriorate in upward facing heater, however, in contrast effect of enhancement for downward. Maximum CHF for upward- and downward-facing heater are 2.1 and 1.9, respectively. Reduction of mean contact angle demonstrate enhancement on the critical heat flux for both upward-facing and downward-facing heater configuration. However, nucleate boiling heat transfer shows inconsistency in similar concentration with sequence of boiling time. For both downward- and upward-facing nanocoated heater’s BHT and CHF, the optimum configuration denotes by C = 400 kg/m3 with tb = 1 minute which shows the best increment of boiling curve trend with lowest wall superheat ΔT = 25 K and critical heat flux enhancement of 2.02 times.
Break Size Effects on CET Response in an Upper Head SBLOCA Transient
Authors: Gallardo S. , Querol A. , Verdú G.
Published: October 2013

In the transients produced during Small Break Loss-Of-Coolant Accidents (SBLOCA), the maximum Peak Cladding Temperature (PCT) in the core could suffer rapid excursions which might strongly affect the core integrity. Most Pressurized Water Reactors (PWR) have Core Exit Thermocouples (CETs) to detect core overheating by considering that superheated steam flows in the upward direction when core uncovery occurs during SBLOCAs. Operators may start Accident Management (AM) actions to mitigate such accident conditions when the CET temperature exceeds a certain value. However, in a Vessel Upper Head SBLOCA, a significant delay in time and temperature rise of CETs from core heat-up can be produced.

This work is developed in the frame of OECD/NEA ROSA Project Test 6-1 (SB-PV-9 in JAEA) handled in the Large Scale Test Facility (LSTF) of the Japan Atomic Energy Agency (JAEA). Test 6-1 simulated a PWR pressure vessel Upper-Head SBLOCA with a break size equivalent to 1.9% of the cold leg break under the assumption of total failure of High Pressure Injection System (HPIS).

The paper shows several analyses about the geometry variables (size, location, flow paths and Upper Head nodalization) which can influence on the pressure vessel Upper Head SBLOCA model performed using the thermal-hydraulic code TRACE5.
Steady and Unsteady Flow Measurements Under Low Load Conditions in a Low Pressure Model Steam Turbine
Authors: Segawa Kiyoshi , Senoo Shigeki , Hamatake Hisashi , Kudo Takeshi , Nakamura Tateki , Shibashita Naoaki
Published: October 2013

Four-stage low pressure model steam turbine tests are carried out under the low load conditions of 0% to 20% load. In such low load conditions, the reverse flow is generated from turbine exit. Steady pressure measurements using multi-hole pneumatic probes are made to specify the outer boundary of the reverse flow region. The reverse flow regions are determined from the flow angles measured by the multi-hole pneumatic probes, traversing in the radial direction which rotates 360 deg around the longitudinal axis. The outer boundary of the reverse flow regions varies depending on turbine loads and has good agreement with the results of the numerical analyses.

The pressure fluctuations are measured using unsteady pressure transducers installed on both the inner and outer side walls of the outlet stage and on the next-stage stationary blade surfaces to investigate the relation between pressure fluctuation and volumetric flow. It is found that the pressure fluctuations, which are defined by the standard deviation of unsteady pressure, become larger with decreased volumetric flow at the outer side as well as the inner side which is the same as the tendency seen for blade dynamic stress characteristics. The authors have previously reported good agreement between the experimental and numerical results.

The unsteady pressure probe as another measurement technique is employed to investigate the spanwise pressure fluctuations at the outlet of the moving blade. The results show that as the load decreases, large pressure fluctuations are observed in the vicinity of the outer side after the stages where the reverse flow is observed. This is the same tendency as the results of wall pressure measurements. The generation of large pressure fluctuations, detected by the two different measurement techniques, might have a relationship with the effects of not only the vortex motion in the reverse flow region but also the overall flow field (including main forward flow) oscillated by the multiple vortex motions in the reverse flow region as seen in both experiments and computations. The large pressure fluctuations in the vicinity of the outer side after the blade lead to the increase of exciting force and vibration stress on moving blades.

Detailed aerodynamic investigations of these part-load conditions are needed to analyze a blade excitation for further improvement of reliability and availability of steam turbines. The complicated flow structures at low load conditions in a steam turbine can be understood with the aid of both the steady and unsteady flow measurements and calculations.
Simulation of the TMI-2 Accident With ATHLET-CD and Analysis of the Late-Phase Modeling
Authors: Hoffmann Mathias , Koch Marco K.
Published: October 2013

This paper provides the results of a simulation of the TMI-2 accident with the current version of ATHLET-CD Mod. 2.2A as part of code validation activities at Ruhr-Universität Bochum (RUB). The calculated plant behavior during the first four phases of the accident is discussed and analyzed in comparison to available post-accident data and measurements. The calculation captures the plant response in terms of the thermal-hydraulics very well during the first two phases. However, during the reflooding of the degraded core some discrepancies between the calculation and TMI-2 data are identified. The code basically underestimates the hydrogen generation in this phase. Moreover, the debris bed and molten pool behavior during this phase cannot be simulated yet. An essential limitation of the current capabilities of the code in terms of the late-phase is the lack of models addressing the relocation of molten materials to the lower plenum of the reactor pressure vessel. Based on this analysis, the next steps needed to model the relocation of molten core components to the lower plenum are identified. These are the lateral leveling of accumulated molten material inside molten pools as well as the slumping to the lower plenum via different paths.
Steam Turbine Overspeed Protection Failures, Causes, and Strategies to Avoid Them
Authors: Ebner Wallace F.
Published: October 2013

There have been a number of failures of overspeed protection schemes in recent years. This paper describes the basic protection schemes and the areas of weakness and provides an overview of the over speed losses that have taken place over the last several years as well as the causes. It presents some of the statistics regarding losses in the last 5 years and discusses some common themes. What does this data tells us? What are ways to improve the chances of avoiding these failures? What can owners and operators do to prevent them at their plants?
The Convergence of Squeeze: With Respectable Speed, a New Gas Turbine Power Plant Rises at an Arizona Mine
Authors: Baker John , Ralph Marshall
Published: October 2013

When muscular market forces and juicy resource opportunities fall into alignment, the usual pace of power plant capital development can give way to a literal sprint. The 2010 development by Mercator Minerals of a new 45 MW gas turbine power plant at the Mineral Park Mine in Arizona is an example of the respectable speed at which an LM6000 PF Sprint plant can be bought, fueled, built and fired up. In this case, a grand market opportunity dropped into the in-basket of a mine CEO prepared to pounce: Mercator Minerals got the opportunity to sell, in a short delivery window, a great amount of copper/molybdenum ore concentrate. The opportunity was blocked by a shortage of electricity needed to mine it and concentrate the ore. A long-planned 220kV transmission line could not be permitted and built in time. Mercator recognized that a gas pipeline could be built, however, and was within the capabilities of Mercator’s construction resources. Solution: a gas-fired mine-site power plant. On Christmas Eve, 2009, Mercator summoned its power supply consultant to the mine.

Power plant engineers earn part of their keep by inserting a moderating element into these spirited discussions. But when the engineers met with Mercator’s CEO on Christmas Eve, they found themselves pressed “vigorously” on the spot for a review of plant and equipment options, and an AFE-level cost of electricity estimate. The mad pace continued: the final consultant report, and Mercator’s command to proceed, came before New Year’s Day. After a multi-month scramble to find financing and an investigation into used, gray-market and new turbine availability, the engineers located a new LM6000 high in GE’s queue and temporarily homeless due to a schedule change. All parties agreed that EPC would be too slow. Mercator undertook to procure and build the entire project, employing the consultant as the design engineer. The plant’s completion and entry into service in 2010 was no surprise to Mercator. For others involved, the project seemed to finish before it had a chance to start. The project, now running productively, is a vivid testimony to Mercator’s ability to move decisively to develop a power plant crucial to the Mineral Park Mine’s production commitments.
Safety Assessment of the Implementation of a Five-Year Fuel Operation With Use of Enhanced-Algorithm at Ukrainian NPPs
Authors: Glushenkov R. S.
Published: October 2013

Nuclear power engineering of Ukraine’s nuclear energetic is based on thermal neutron reactors. WWER-1000 (water-cooled and water-moderated energy reactor) is the most common type of the reactors in Ukraine.
Research on Vortex Eliminating of the Sump of Cooling Pump by CFD
Authors: Cheng Li , Liu Chao
Published: October 2013

The main function of the open sump is to adjust flow pattern and provide good inflow condition for the cooling pump, which plays an important part in the pump performance. However, because of the defective design of the sump, it will lead to deterioration of flow pattern and cause the bad influence on normal operation of the pump. This paper elaborated kinds of vortex-elimination rectification measures and compute different kinds flow pattern after adding rectification measures based on steady incompressible flow CFD. The researches compare flow patterns of pre and post rectification and analyze the feasibility of vortex-suppressing rectification measures.
Visualization of Entrainment and Surface Behavior of High Speed Air Jet Blowing Out From a Hole to Stagnant Water
Authors: Nago Kohei , Koizumi Yasuo , Uchibori Akihiro , Ohshima Hiroyuki
Published: October 2013

A two dimensional air jet was blown out from a nozzle into water in a thin vessel. The behavior of the interface between water and the air jet and also the air jet were recorded with a high speed video camera. Filament-like ears and wisps pulled-out from the wavy water surface were noticed in the recorded photos. Droplets are formed from these. Droplet diameters were obtained from the recorded photos. As the air velocity increased, the number of droplets created by the air jet increased lineally and the smaller droplets increased. The correlation for the droplet diameter distribution developed for the annular dispersed two-phase flow in a pipe predicted well the present results. The correlations for the droplet diameter developed for the annular dispersed two-phase flow in a pipe and for the jet blowing out from the stagnant water pool considerably underpredict the experimental results.
Correlation Investigation of Condensation Heat Exchanger Design for Secondary Passive Cooling System
Authors: Lee Hee Joon , Kang Han-Ok , Lee Tae-Ho , Park Cheon-Tae
Published: October 2013

Recently vertical or horizontal type condensation heat exchangers are being studied for the application to secondary passive cooling system of nuclear plants. To design vertical condensation heat exchanger in water pool, a thermal sizing program of condensation heat exchanger, TSCON (Thermal Sizing of CONdenser) was developed in KAERI (Korea Atomic Energy Research Institute). In this study, condensation heat transfer correlation of TSCON is evaluated with the existing experimental data set to design condensation heat exchanger without non-condensable gas (pure steam condensation). From the investigation of the existing condensation heat transfer correlation to the existing experimental data, the improved Shah correlation showed most satisfactory results for the heat transfer coefficient and mass flow rate in a heat exchanger in both subcooled and saturated water pools without the presence of non-condensable gas.
High Pressure Feedwater Heater Hemi Head Manway Hoist
Authors: Michell Frank L. , Adkins David , Selby Tim , Winiger Curt
Published: October 2013

Removing and installing manway access doors on hemi-head style Feedwater Heaters can be very challenging/difficult with significant safety concerns handling components that weigh as much as 500lbs on large HP Supercritical Units. Original heater manufacturer supplied handling rigs typically require manual hands-on “grunt” methods to manipulate the rigs with the heavy doors hanging on the devices. American Electric Power (AEP) and Industrial Contractors Skanska (ICS) collaborated to design and construct a portable, hydraulically operated manway handling hoist that makes removal and installation safe and easier for plant personnel to use. The hoist has successfully been used to remove and re-install manway doors on HP Heaters on AEP 1300MW Supercritical Plants. Details of the OEM furnished rig and the AEP/ICS developed manway handling hoist will be discussed in the paper.
A Feasibility Study on Various Power-Conversion Cycles for a Sodium-Cooled Fast Reactor
Authors: Dragunov Alexey , Saltanov Eugene , Bedenko Sergey , Pioro Igor
Published: October 2013

One of the current engineering challenges is to design next generation (Generation IV) Nuclear Power Plants (NPPs) with significantly higher thermal efficiencies compared to those of current NPPs to match or at least to be close to thermal efficiencies reached at thermal power plants (43–55%). A Sodium-cooled Fast Reactor (SFR) is one of six concepts considered under the Generation IV International Forum (GIF). This concept is the only one from the Generation IV reactors, which is actually in operation in Russia.

In general, there are 3 possibilities for an SFR in terms of the secondary cycle:

1. Subcritical-pressure Rankine-“steam”-cycle through a heat exchanger (current approach used in Russian and Japanese power reactors).

2. Supercritical-pressure Rankine-“steam”-cycle through a heat exchanger (new approach).

3. Supercritical-pressure CO2 Brayton-gas-turbine-cycle through a heat exchanger (US approach).

The BN-600 reactor is a sodium-cooled fast-breeder reactor built at the Beloyarsk NPP in Russia. It has been in operation since 1980 and adopts the secondary subcritical-pressure Rankine-“steam”-cycle with heat regeneration. Steam extractions are taken from High-Pressure (HP), Intermediate-Pressure (IP) and Low-Pressure (LP) turbines.

The basic method of increasing the thermal efficiency of power plants is to improve it by increasing the operating pressure and temperature. With the advent of modern super alloys, the Rankine-“steam”-cycle has progressed into the supercritical region of the coolant and is generating net efficiencies into the mid 40% range. Calculations of thermal efficiency of a secondary sub- and supercritical-pressure Rankine-“steam”-cycle with heat regeneration are presented in the paper.

The Brayton-gas-turbine cycle is under consideration for future nuclear power reactors. The higher operating temperatures will be achieved, the higher thermal efficiency will be. Supercritical CO2 cycle is a new approach in Brayton-gas-turbine cycle. Carbon dioxide has a critical pressure of 7.38 MPa and a critical temperature of 31.0°C, which is significantly less than that of water (22.064 MPa and 373.95°C). However, liquid sodium is more compatible with SC CO2 than with water. Therefore, thermal efficiency of this SC CO2 cycle is also calculated.
Validation of TRACE Code for Flashing-Induced Density Wave Oscillations in SIRIUS-N Facility, Which Simulates ESBWR
Authors: Furuya Masahiro , Nishi Yoshihisa , Ueda Nobuyuki
Published: October 2013

The TRACE code was validated against the flashing-induced density wave oscillation in the SIRIUS-N facility at low pressure (from 0.1 to 0.5 MPa) as a part of the international CAMP-Program of USNRC. The SIRIUS-N facility is a scaled copy of natural circulation BWR (ESBWR). Stability map of TRACE agrees with that of SIRIUS-N facility at low subcooling region, though instability observed in the lower heat flux and higher subcooling region from the stability limit of experiment. The TRACE code demonstrates the flashing-induced density wave oscillation characteristics: The oscillation period correlates well with the transit time of single-phase liquid in the chimney regardless of the system pressure, inlet subcooling, and heat flux. Unlike Type-I and II density wave oscillations, the inlet or exit throttling does not affect stability boundary and oscillation amplitude of flashing-induced density wave oscillations significantly. Increasing pressure decreases oscillation amplitude. The comprehensive validation confirms that the TRACE code can demonstrate thermal-hydraulic stability of natural circulation BWRs.
Heat Transfer Characteristics of One Side Heated Vertical Rectangular Channel Inserting Porous Material
Authors: Takeda Tetsuaki , Sato Akihiro , Funatani Shumpei
Published: October 2013

The objective of this study is to not only investigate heat transfer characteristics of natural convection of a one-side heated vertical channel inserting the porous materials with high porosity but also develop the passive cooling system for the Very-High-Temperature Reactor (VHTR). An experiment and analysis was carried out using the one-side heated vertical rectangular channel. From the results obtained in the experiment and analysis, it was found that an amount of removed heat by forced convection using the copper wire (porosity>0.996) was about 15% higher than that without the wire. It was also found that the amount of transferred heat from the heated wall will be increased even if the heat removed by natural convection. Furthermore, the ratio between the amounts of heat removed of the rectangular channel with the porous material and without the porous material increases with increasing temperature of the channel wall. In order to obtain the heat transfer and fluid flow characteristics of the vertical channel inserting porous material, we have also carried out a numerical analysis using a commercial CFD code. This paper describes thermal performances of the one-side heated vertical rectangular channel inserting copper wire with high porosity. From a view point of economical and safety characteristics, the passive cooling system should be designed for the VHTR as the best way of the system. Therefore, the gas cooling system by natural convection is the one of candidate system.
Risk-Informed Approach to Debris Bed Coolability Issue
Authors: Yakush Sergey E. , Lubchenko Nazar T. , Kudinov Pavel
Published: October 2013

Coolability of an ex-vessel debris bed in severe accident conditions is considered from the risk perspective. The concept of “load versus capacity” is employed to quantify the probability of failure (local dryout). Possible choices of “load” and “capacity” in terms of heat fluxes, thermal power or melt mass are discussed. Results of Monte Carlo simulations of distribution functions for the local heat flux and the dryout heat flux at the debris bed top point (defined as the extensions of one-dimensional counterparts) are presented. A surrogate model for the dryout heat flux is developed by the generalization of two-dimensional simulation results. Dryout probabilities are obtained under the conservative assumptions (neglecting the coolability improvement due to side ingress of water into a non-flat debris bed), and from the surrogate model. Outlook is given for the prospective development of the risk-informed approach to debris bed coolability in the context of comprehensive severe accident risk analysis.
Steam Turbine, Boiler, and Valve Optimization Strategies to Recover Parasitic Load and Provide Life Extension
Authors: Smiarowski Michael W.
Published: October 2013

Coal-fired power plants that survive into the future and avoid being displaced by combined cycle plants and wind turbines will require air quality control (AQC) equipment to conform to EPA requirements per the Cross State Air Pollution Rule (CSAPR). This AQCS can consume 5–10% parasitic load of a coal-fired unit’s output.

This paper will provide discussion on recent industry trends of utilities pushing to implement modernization projects for parasitic load recapture and also other benefits such as life extension, improved maintenance, better efficiency, availability, and reliability. The three main strategies discussed will be:

• Boiler and Turbine Optimization options

• Steam Turbine Modernization with the latest technology steam path

• Steam Valve Modernization

Coal-fired plants have been careful to implement these types of projects without additional heat input in- order to avoid any new source review issues.

Recent industry examples and development efforts will be discussed in this paper to provide an overview of these options current available or that will be available in the near future for coal-fired power plants.
Thermal Analysis Technique for Coolers Operating in Off and Low Load Conditions
Authors: Muldoon Thomas J.
Published: October 2013

The most conservatively designed power plant heat exchangers are designed to meet a maximum heat load with minimum fluid temperature differences. When the input temperatures are less than design maximums, the cooler will usually be in a position of over performance. This relationship is especially true when the heat exchanger is a closed Component Cooling Water (CCW) heat exchanger with inlet fluid at ambient conditions.

Maintaining a consistent cooling temperature is an important concern in the operation of a power plant. It is important that the cooling needs of the equipment such as the hydrogen coolers are maintained at a set temperature. Overcooling may not be of benefit to the equipment. The component which cools the service water with the local cooling water is a component cooling water heat exchanger (CCW). The two primary methods of controlling the heat rejection performance on these vessels is to throttling the tubeside flow to get a consistent shell outlet temperature with control valves or leave the tubeside flow constant and by-pass a portion of the shellside flow.

Estimating the performance of the heat exchanger with given set of inlet conditions and a fixed design point can be accomplished using a the Number Transfer Units (NTU) method. Opening and closing the control valve is based on the estimated performance. This analysis can be used by power plant personnel to gauge the operation of these vessels over varying operating conditions. The analysis can also include the effect of different values of cleanliness and the extent of throttling. As a unit experiences fouling, additional flow is required to meet the thermal requirements. Depending upon the extent of fouling, the inlet valve will be either opened or closed. Plant personnel may observe the cooling water inlet temperature and the extent to which the inlet valve is open, and use that information to determine possible fouling and setup a maintenance schedule. The following analytical approach for evaluating low, critical, or off load conditions is important in the design and operation of these types of power plant heat exchangers, piping and control valve systems.
Sensitivity Study of the South Texas Project Power Plant Steady-State Simulations Using RELAP5-3D Coupled With Dakota
Authors: Rodriguez O. A. , Vaghetto R. , Hassan Y. A.
Published: October 2013

A RELAP5-3D input deck of the South Texas Project (STP) power plant was created in order to study the thermal-hydraulic behavior of the plant during normal operation (steady-state) and during a Loss of Coolant Accident (LOCA). It is important to study the sensitivity of selected output parameters such as the total coolant mass flow rate, the peak clad temperature, the secondary pressure, as a function of specific input parameters (reactor nominal power, vessel inlet temperature, steam generators primary side heat transfer coefficient, primary pressure etc.) in order to identify the variables that play a role in the uncertainty of the thermal-hydraulic calculations. RELAP5-3D, one of the most used best estimate thermal-hydraulic system codes, was coupled with DAKOTA, developed by Sandia National Laboratory for Uncertainty Quantification and Sensitivity Analysis in order to simplify the simulation process and the analysis of the results. In the present paper, the results of the sensitivity study for selected output parameters of the steady-state simulations are presented. The coupled software was validated by repeating one set of simulations using the RELAP5-3D standalone version and by analyzing the simulation results with respect of the physical expectations and behavior of the power plant. The thermal-hydraulic parameters of interest for future uncertainty quantification calculations were identified.
Function of Isolation Condenser of Fukushima Unit-1 Nuclear Power Plant
Authors: Naitoh Masanori , Suzuki Hiroaki , Okada Hidetoshi
Published: October 2013

The Tohoku Region Pacific Coast Earthquake with magnitude 9.0 occurred at 2:46 PM of March 11th, 2011, followed by a huge Tsunami. The Fukushima Daiichi nuclear power station suffered serious damages from the Tsunami, involving core melt and release of large amount of fission products to an environment. The station blackout (SBO) occurred due to submergence of emergency equipment by the sea water. The isolation condenser (IC) was the only device for decay heat removal at the unit-1 of the Fukushima Daiichi nuclear power station after the reactor scram. The IC function was analyzed with a severe accident analysis code SAMPSON. The analysis results showed that (1) core melt resulting in RPV failure occurred since the IC operation was limited because it was not designed as a countermeasure to mitigate severe accident progression in Japan and (2) even assuming the continuous IC operation after the SBO to mitigate severe accident progression, the RPV failure occurred at 18:52, March 12th. However, since the alternate water injection by a fire engine was actually ready to start at 5:46, March 12th, which was earlier than calculated RPV failure time, the RPV failure could be prevented by continuous IC operation.
Investigation of Hydrodynamic Loads Associated With Pyrotechnic Valve Actuation
Authors: Henry Christopher E. , Lim Jaehyok , Ozar Basar
Published: October 2013

Pyrotechnic-actuated valves are utilized for various applications requiring remote actuation with high reliability. One such application is passive safety injection (SI) within the emergency core cooling system (ECCS) within the Generation III+ advanced commercial nuclear power plant designs. The pyrotechnic (explosive) actuation within the valve internals, which opens the valve for water flow, creates a vertical force that must be supported by the surrounding piping restraints. This is a well-known phenomenon that is accommodated in the design.

However, there exists also a subsequent, lesser-known axial (horizontal) force that must be accommodated also. A RELAP5/MOD3.3 (patch03) code [1] model for the pyrotechnic valve and the broader injection system was configured to analyze the extent of this water hammer. Typically, the pyrotechnic actuation occurs at relatively low reactor coolant system pressure since the injection itself will eventually be a passive gravity-driven feed. However, even at this low actuation pressure, the RELAP5 analysis demonstrates that the hydrodynamic loads can be substantial. Furthermore, the analysis shows that staggered actuation of a two-valve parallel configuration can exacerbate and magnify the load, compared to a single valve actuation.
Unimolecular Dual Incretins Maximize Metabolic Benefits in Rodents, Monkeys, and Humans
Authors: Finan Brian , Ma Tao , Ottaway Nickki , Müller Timo D. , Habegger Kirk M. , Heppner Kristy M. , Kirchner Henriette , Holland Jenna , Hembree Jazzminn , Raver Christine , Lockie Sarah H. , Smiley David L. , Gelfanov Vasily , Yang Bin , Hofmann Susanna , Bruemmer Dennis , Drucker Daniel J. , Pfluger Paul T. , Perez-Tilve Diego , Gidda Jaswant , Vignati Louis , Zhang Lianshan , Hauptman Jonathan B. , Lau Michele , Brecheisen Mathieu , Uhles Sabine , Riboulet William , Hainaut Emmanuelle , Sebokova Elena , Conde-Knape Karin , Konkar Anish , DiMarchi Richard D. , Tschöp Matthias H.
Published: October 2013

Compared to best-in-class GLP-1 mono-agonists, unimolecular co-agonists of GLP-1 and GIP with optimized pharmacokinetics enhance glycemic and metabolic benefits in mammals.
Regulation of CTnDOT Conjugative Transfer Is a Complex and Highly Coordinated Series of Events
Authors: Waters Jillian L. , Salyers Abigail A.
Published: October 2013

CTnDOT is a 65-kb conjugative transposon that is found in
Bacteroides
spp., which are one of the more abundant members within the lower human gastrointestinal tract. CTnDOT encodes resistance to the antibiotics erythromycin and tetracycline (Tc). An interesting feature of CTnDOT is that exposure to low levels of Tc induces a cascade of events that ultimately results in CTnDOT conjugative transfer. However, Tc is apparently not a switch that activates transfer but rather a signal that appears to override a series of negative regulators that inhibit premature excision and transfer of CTnDOT. In this minireview, we summarize over 20 years of research that focused on elucidating the highly coordinated regulation of excision, mobilization, and transfer of CTnDOT.

IMPORTANCE
Bacteroides
spp. are abundant commensals in the human colon, but they are also considered opportunistic pathogens, as they can cause life-threatening infections if they should escape the colon.
Bacteroides
spp. are the most common cause of anaerobic infections and are rather difficult to treat due to the prevalence of antibiotic resistance within this genus. Today over 80% of
Bacteroides
are resistant to tetracycline (Tc), and a study looking at both clinical and community isolates demonstrated that this resistance was specifically due to the conjugative transposon CTnDOT.
The effect of fall prevention exercise programmes on fall induced injuries in community dwelling older adults
Authors: El-Khoury Fabienne , Cassou Bernard , Charles Marie-Aline , Dargent-Molina Patricia
Published: October 2013

STUDY QUESTION

Are fall prevention exercise interventions for older people living in the community effective in preventing different types of fall related injuries?

SUMMARY ANSWER

Exercise programmes designed to prevent falls in older adults seem also to prevent injuries caused by falls, including the most severe injuries. Such programmes also reduce the rate of falls leading to medical care.
Service providers’ perspectives, attitudes and beliefs on health services delivery for Aboriginal people receiving haemodialysis in rural Australia: a qualitative study
Authors: Rix Elizabeth F , Barclay Lesley , Wilson Shawn , Stirling Janelle , Tong Allison
Published: October 2013

Objective

Providing services to rural dwelling minority cultural groups with serious chronic disease is challenging due to access to care and cultural differences. This study aimed to describe service providers’ perspectives on health services delivery for Aboriginal people receiving haemodialysis for end-stage kidney disease in rural Australia.

Design

Semistructured interviews, thematic analysis

Setting

A health district in rural New South Wales, Australia

Participants

Using purposive sampling, 29 renal and allied service providers were recruited, including nephrologists, renal nurses, community nurses, Aboriginal health workers, social workers and managers. Six were Aboriginal and 23 non-Aboriginal.

Results

Improving cultural understanding within the healthcare system was central to five themes identified: rigidity of service design (outreach, inevitable home treatment failures, pressure of system overload, limited efficacy of cultural awareness training and conflicting priorities in acute care); responding to social complexities (respecting but challenged by family obligations, assumptions about socioeconomic status and individualised care); promoting empowerment, trust and rapport (bridging gaps in cultural understanding, acknowledging the relationship between land, people and environment, and being time poor); distress at late diagnosis (lost opportunities and prioritise prevention); and contending with discrimination and racism (inherent judgement of lifestyle choices, inadequate cultural awareness, pervasive multilevel institutionalised racism and managing patient distrust).

Conclusions

Service providers believe current services are not designed to address cultural needs and Aboriginality, and that caring for Aboriginal patients receiving haemodialysis should be family focused and culturally safer. An Aboriginal-specific predialysis pathway, building staff cultural awareness and enhancing cultural safety within hospitals are the measures recommended. Increasing patient support for home haemodialysis may improve health and the quality of care outcomes.
MAKESPAN MINIMIZATION ON THREE-MACHINE FLOW SHOP WITH DETERIORATING JOBS
Authors: WANG JI-BO , WANG MING-ZHENG
Published: October 2013

In this study, we consider a permutation flow shop scheduling problem on a three-machine with deteriorating jobs (a deteriorating job means that the job's processing time is an increasing function of its starting time) so as to minimize the makespan. We model job deterioration as a function that is proportional to a linear function of time. For some special cases, we prove that the problem can be solved in polynomial time. We develop branch-and-bound and heuristic procedures for the general case. Computational experiments for the branch-and-bound algorithm and heuristic algorithm are presented.
THE FORMULAE FOR PARAMETERS OF THE SECONDARY ELECTRON YIELD OF INSULATORS FROM 10 keV TO 30 keV
Authors: XIE AI-GEN , LI QING-FANG , CHEN YUN-YUN , WU HONG-YAN
Published: October 2013

Based on the formula for the average energy required to produce an internal secondary electron (ε) in emitter, the energy band of insulator and the assumption that the maximum exit energy of secondary electron in insulator is reverse to the width of forbidden band, the formula for ε in insulator is deduced. On the basis of the formula for the number of internal secondary electrons produced in the direction of the velocity of primary electrons per unit path length, the energy band of insulator and the characteristic of secondary electron emission, the formula for the probability of secondary electrons passing over the surface barrier of insulator into the vacuum (B) is also deduced. According to some relationship between the parameters of secondary electron yield from insulator, the formula for the mean escape depth (1/α) is successfully deduced. The formulae for ε and 1/α are experimentally proven, respectively, and thereafter the formula for B is indirectly proven to be true by the experimental results. It is concluded that the formulae for ε, B and 1/α are universal to estimate ε, B and 1/α under the condition that primary electrons from 10 keV to 30 keV hit on an insulator, respectively.
MULTIPLE BIFURCATIONS IN A PREDATOR–PREY SYSTEM OF HOLLING AND LESLIE TYPE WITH CONSTANT-YIELD PREY HARVESTING
Authors: HUANG JICAI , GONG YIJUN , CHEN JING
Published: October 2013

The bifurcation analysis of a predator–prey system of Holling and Leslie type with constant-yield prey harvesting is carried out in this paper. It is shown that the model has a Bogdanov–Takens singularity (cusp case) of codimension at least 4 for some parameter values. Various kinds of bifurcations, such as saddle-node bifurcation, Hopf bifurcation, repelling and attracting Bogdanov–Takens bifurcations of codimensions 2 and 3, are also shown in the model as parameters vary. Hence, there are different parameter values for which the model has a limit cycle, a homoclinic loop, two limit cycles, or a limit cycle coexisting with a homoclinic loop. These results present far richer dynamics compared to the model with no harvesting. Numerical simulations, including the repelling and attracting Bogdanov–Takens bifurcation diagrams and corresponding phase portraits, and the existence of two limit cycles or an unstable limit cycle enclosing a stable multiple focus with multiplicity one, are also given to support the theoretical analysis.