Shutdown Operations Research Articles

Behavioral accommodation of nesting hawks to wind turbines

ABSTRACTThe most direct effects of wind energy development on birds are rotor blade strikes and collisions with wind turbines. Probability of a blade strike is affected by the rates at which a bird visits the rotor swept zone (RSZ), and mitigated by the behaviors it uses to avoid being struck. Between 2011 and 2013, we studied the occurrence and nature of avoidance responses of 3 nesting ferruginous hawks (Buteo regalis), 5 Swainson's hawks (B. swainsoni), and 2 red‐tailed hawks (B. jamaicensis) to turbines built within their territories. Two of 10 breeding males we tracked with satellite telemetry were turbine‐collision fatalities, one during the study and the other in the following year. Collectively, nesting hawks displayed no macro‐avoidance of turbine projects and flew adjacent to or within RSZs at high rates ( = 0.8 visits/hr, 1.3 min/visit; n = 387 visits during 434 hr of observation) synchronized with morning and afternoon peaks in foraging activity. Passes through rotors accounted for 9.8% of responses. The turbine that hawks approached most closely from collective encounters on each territory accounted for an average of 29% of all visits to RSZs and visitation was greater than expected at turbines <0.8 km from nests (P < 0.001). As rotor speed increased, the frequency that hawks in RSZs flew between turbine rows increased relative to other avoidance behaviors and hawks that were potentially distracted (i.e., hunting or aggressive chasing) increased avoidance flights over and between turbines. The ability of hawks to employ evasive behaviors mitigated blade collision but allowed for close, hourly interaction with turbines that increased risk of collision. Where nesting populations of hawks are at risk, particularly ferruginous hawks, pre‐construction siting of wind turbines needs to account for nest locations and expected high rates of hawk visitation to turbines <800 m from nests. On existing projects collision risk can be reduced through operational shutdown of turbines in this zone during 2 daily peaks in hawk foraging in the vicinity where hawks nest, but a greater effectiveness can be achieved by shutdown of specific turbines associated with highest regular use. © 2018 The Wildlife Society.

A PC-based high temperature gas reactor simulator for Indonesian conceptual HTR reactor basic training

In planning for nuclear power plant construction in Indonesia, helium cooled high temperature reactor (HTR) is favorable for not relying upon water supply that might be interrupted by earthquake. In order to train its personnel, BATAN has cooperated with Micro-Simulation Technology of USA to develop a 200 MWt PC-based simulation model PCTRAN/HTR. It operates in Win10 environment with graphic user interface (GUI). Normal operation of startup, power maneuvering, shutdown and accidents including pipe breaks and complete loss of AC power have been conducted. A sample case of safety analysis simulation to demonstrate the inherent safety features of HTR was done for helium pipe break malfunction scenario. The analysis was done for the variation of primary coolant pipe break i.e. from 0,1% - 0,5 % and 1% - 10 % helium gas leakages, while the reactor was operated at the maximum constant power of 10 MWt. The result shows that the highest temperature of HTR fuel centerline and coolant were 1150 °C and 1296 °C respectively. With 10 kg/s of helium flow in the reactor core, the thermal power will back to the startup position after 1287 s of helium pipe break malfunction.

ISIS TS1 Project Summary

Following a feasibility phase which began in 2012, the TS1 upgrade project entered its implementation phase in April 2016. The project is, in essence, a circa £16.25M sustainability project for target station 1 (TS1) of the ISIS facility, Rutherford Appleton Laboratory (RAL), which has been in operation since 1984. Its aims are: to secure the future of TS1 and enable it to operate for many more years, to improve flexibility and future upgradability, to make operation of the target station easier, a neutron performance increase of up to a factor of 2 (on some instruments), as well as providing a strong technical foundation on which the facility can continue to build and develop in the coming years.This paper will provide a summary of the project structure and progress to date, as well as covering some of the encountered challenges and successes. It will further detail the motivations behind the project’s inception, including the critical success factors.The implementation phase includes design progression, procurement, verification and validation testing, pre-installation testing, along with a large number of other supporting activities. It is currently envisaged that a long operational shutdown of ISIS will occur in a window of 2019-2021, with the project looking to exploit this opportunity for the strip-out, installation and commissioning work required to bring to fruition the planned changes.

AC Loss Evaluation of a 10T Class Small REBCO Coil With Conduction-Cooled Configuration

In order to use a coil wound with REBCO-coated conductor in a conduction cooling configuration, ac loss of the coil should be quantitatively predicted and designed under the operating conditions, for example during charging-up and -down, or shutdown operation. A tape-shaped REBCO-coated conductor is suited to be composed of a stack of single pancake coils for generating high magnetic field. Various researchers have measured and evaluated the ac loss of REBCO tape; however, there are few reports about the ac loss of the coil as measured at liquid nitrogen temperature. In this report, the ac loss of REBCO coil composed of a stack of 22 single pancakes with 50 mm in inner diameter, 132 mm in outer diameter, and 105 mm in height, generating 13.5T at 10 K, was measured by electrical method and evaluated with conduction cooling configuration. The experimental results were compared with the calculated results and discussed.

Effect of input parameters intensity and duration on dynamic performance of MED-TVC plant

Multi-Effect-Desalination (MED) may be exposed to fluctuations (disturbances) in input parameters during operation. Therefore, there is a requirement to analyze the transient behavior of such MED systems. In this work, a dynamic model is developed and used to examine the effect of abrupt and ramp changes in the main operational parameters on the plant behavior and performance. The results show that the disturbance intensity variation has a major role in the desalination plant behavior. For the current MED-TVC configuration, it is recommended to limit the reduction in the seawater cooling flow rate to under 12% of the designed steady-state value to avoid dry out in the evaporators. A reduction in the motive steam flow rate and cooling seawater temperature of more than 20% and 35% of the nominal operating values, respectively, may lead to flooding in the evaporators and a complete plant shutdown. On the other hand, the disturbance period has a minimal effect on plant performance if it avoids the critical values of the disturbance intensity that can cause plant shutdown. Simultaneous combinations of two different disturbances with opposing effects result in a modest effect on the plant operation and they can be used to control and mitigate the flooding/drying effects of the disturbances. For simultaneous combinations of disturbances with similar effect, the plant needs an accurate control system to avoid an operational shutdown.

Durability of Ni/TiO2 catalyst containing trace chlorine for CO selective methanation

We investigated the durability of Ni/TiO2 catalyst in CO selective methanation reaction. In the reaction test up to 72 h, trace amounts of chlorine component contained in the catalyst gradually decreased. As a result, the progress of the methanation of CO2 increased, leading to a decrease in the reaction selectivity of the methanation of CO in the title reaction. By contrast, in the early stage of the reaction in which the elimination of chlorine component was small, it was confirmed that the number of active sites of metallic Ni increased, and the CO methanation activity was improved. Furthermore, it was found that the chlorine component in the catalyst was more remarkably removed by exothermic reaction heat under the methanation reaction atmosphere as compared with the case of heat treatment under other atmosphere. Catalyst durability under the conditions simulating a daily start-up and shut-down operation that repeated a cycle of cooling and heating the temperature of the catalyst layer to room temperature was also evaluated. As a result, we revealed that a trace amount of chlorine component was removed by exposure to condensed water, leading to a decrease in the reaction selectivity of the catalyst.

Innovative technologies for spent fuel safe management at Ignalina channel-type reactors

Abstract In Lithuania, all spent nuclear fuel (SNF) resulted from the operation of the Ignalina Nuclear Power Plant (INPP), which had two Russian Acronym for “Channelized Large Power Reactor”-type reactors. After the final shutdown, the total amount of SNF at the INPP was approximately 22,000 fuel assemblies. All these assemblies will be stored for about 50 years and disposed of after that. The decision to shut down and decommission both reactors in Lithuania before termination of design period raises a significant challenge for the treatment of accumulated SNF. Therefore, various techniques and technologies for SNF management were developed and justified for that specific case, and a set of special equipment was installed at the INPP, the effectiveness of which was demonstrated during its operation. This article presents unique techniques related to the management of SNF adopted and commissioned at the INPP after its operation shutdown, namely fuel rod cladding leak tightness control system and special equipment for collection of possible spillage during handling of SNF assembly in the hot cell. The operational experience and measurement results of fuel rod cladding leak tightness control system are presented.

Evolution of bi-Gaussian surface parameters and sealing performance for a gas face seal under a low-speed condition

Abstract A spiral groove gas face seal, serving as a typical non-contacting seal, commonly encounters face contact during a low-speed condition such as the startup, shutdown, barring and warming-up operations. By using a discrete manner, the surface-topography evolution of the two mated sealing rings during a low-speed barring process is achieved, and is in a great agreement with the previous standard tests. The bi-Gaussian surface-topography evolution is found to well identify the end running-in, material adhesion and deep scratches. Furthermore, the surface-topography evolution exhibits a high correlation with the recorded seal-performance indexes including leakage rate, torque and acoustic emission signal, which is helpful in exploring the deterioration mechanism of sealing performance.

Mechanical Fault Detection on Electrical Machine: Thermal Analysis of Small Brushed DC Motor with Faulty Bearing

Direct current motors (DC motor) are used in the small electric devices commonly. DC motor are cheap and easy to install, thus their popularity. Despite the popularity, faults occur which make diagnosis and detection of faults very important. It avoids financial loss and unexpected shutdown operation causes by these faults. This paper presents an analysis of temperature profile of the much famous small Brushed DC motor with a faulty bearing. The temperature data of healthy DC motor and DC motor with faulty bearing were measured by thermocouple and recorded using data logger in real time until steady state temperature, under different load. The analysis on the steady state temperature allow to conclude that bearing fault can clearly be recognised through characteristics temperature difference with a healthy motor.

Shape and operation optimization of a thick-walled power boiler component

The aim of this article is the proposition of a two-stage optimization of power boiler components subjected to transient thermo-mechanical loads. As the basis of transient load regime, the TRD 301 regulations are used. In the first stage of an investigation, the genetic algorithms are used to determine the optimal shape of the structure. As optimization constraints, the maximum total stresses in the whole cycle are assumed. In the next stage, the method for the start-up and shut-down operation optimization is shown. The problem is defined to minimize the time of start-up and shut-down processes with allowable stress constraints according to TRD regulations. These new methods are of high practical significance and can be implemented throughout the industry, wherever heating and cooling processes take place. The obtained optimization results translate directly into the power unit energy effectiveness because the shut-down and start-up losses are reduced.

Application of frequency response methods in separate and integral effects tests for molten salt cooled and fueled reactors

Molten salt cooled and fueled reactors can be distinguished from other reactor types by their low volatility liquid coolant, which remains single-phase under most operating and accident conditions, and by the substantial heat capacity of both the coolant and solid structures. Forced and natural circulation of the molten salt coolant provide the primary heat transport mechanisms under power and shutdown operation, but thermal coupling to solid heat structures has important effects on dynamic system response during transients. These characteristics make frequency response methods particularly suitable to characterizing and predicting system response to transients. Predicting the temperature of coolant boundary structures during transients, including accidents, is also important for assessing whether damage may occur due to thermal stresses or accelerated thermal creep. This paper discusses how frequency response methods may be used in separate effect and integral effect tests, particularly with simulant fluids to measure the thermal inertia and coupling properties of heat structures and to validate transient response models. The methodology is discussed, followed by examples for application. The scaling parameters developed in this paper can be expected to play a major role in the design of integral effect test facilities for FHRs and MSRs.

Extension of the group contribution NRTL-PRA EoS for the modeling of mixtures containing light gases and alcohols with water and salts

The offshore exploitation of petroleum fluids in normal conditions of pressure and temperature of transport and in presence of salt water is concerned with the prevention of gas hydrate formation, generally thanks to continuous injection of inhibitors, or punctual injection of methanol in start-up and shut-down operations. Hence, models of interest should provide both, satisfactory phase equilibrium estimations of hydrocarbon and alcohol mixtures with water and reliable predictions of their behavior in presence of salts.In this work, the NRTL-PRA EoS is extended to the prediction of phase equilibria in mixtures containing strong electrolytes. The proposed model assumes that the a and b parameters of the cubic EoS only depend on the solvent mole fractions (salt-free), while the gEoSE excess Gibbs energy describes all the interactions between solvents and ions with only two contributions: the SMR term, specific of “Short and Middle Range” interactions between solvents and salts, and the LR relation proposed by Pitzer-Debye-Hückel, for the description of “Long Range” electrostatic interactions. The proposed electrolyte version of the NRTL-PRA model was successfully extended to the modeling of phase behavior of mixtures of light gases at high pressures (methane, carbon dioxide, nitrogen and hydrogen sulfide) and alcohols (methanol, ethanol and 1-propanol) with water and salts (mainly, ternary mixtures containing sodium chloride). As far as possible, results were compared with those provided, for the same systems, by other literature models (cubic Eos, SAFT and CPA equations).

Numerical Investigation of Creep–Fatigue Behavior in a Steam Turbine Inlet Valve Under Cyclic Thermomechanical Loading

The aim of this study was to investigate the cyclic creep–fatigue interaction behavior in a steam turbine inlet valve under cyclic thermomechanical loading conditions. Three years and nine iterations of idealized startup–steady-state operation–shutdown process were chosen. The Ramberg–Osgood model, the Norton–Bailey law, and continuum damage mechanics were applied to describe the stress–strain behavior and calculate the damage. The strength of the steam valve revealed that significant stress variation mainly occurred at the joint parts between the valve diffuser and the adjust valve body, due to the combination of the enhanced turbulent flow and assembly force at these areas. The contact stress at the region of component assembly was sensitive to the cyclic loading at the initial iterations. The maximum decrease amplitude in the normalized contact stress between the second and the fourth iterations reached 0.12. The damage analysis disclosed that the notch of the deflector in the adjust valve had the maximum damage due to the stress concentration.

Comparison of ASME pressure–temperature limits on the fracture probability for a pressurized water reactor pressure vessel

The ASME Code Section XI-Appendix G defines the normal reactor startup (heat-up) and shut-down (cool-down) operation limits according to the fracture toughness requirement of reactor pressure vessel (RPV) materials. This paper investigates the effects of different pressure-temperature limit operations on structural integrity of a Taiwan domestic pressurized water reactor (PWR) pressure vessel. Three kinds of pressure-temperature limits based on different fracture toughness requirements – the KIa fracture toughness curve of ASME Section XI-Appendix G before 1998 editions, the KIC fracture toughness curve of ASME Section XI-Appendix G after 2001 editions, and the risk-informed revision method supplemented in ASME Section XI-Appendix G after 2013 editions, respectively, are established as the loading conditions. A series of probabilistic fracture mechanics analyses for the RPV are conducted employing ORNL’s FAVOR code considering various radiation embrittlement levels under these pressure-temperature limit conditions. It is found that the pressure-temperature operation limits which provide more operational flexibility may lead to higher fracture risks to the RPV. The cladding-induced shallow surface breaking flaws are the most critical and dominate the fracture probability of the RPV under pressure-temperature limit transients. Present study provides a risk-informed reference for the operation safety and regulation viewpoint of PWRs in Taiwan.

Pdaucu Nanobranches As Self-Repair Electrocatalysts for Oxygen Reduction Reaction

As an alternative solution to the low-temperature proton exchange membrane fuel cells (PEMFCs), alkaline fuel cells (AFCs) have regained attention recently.[1-3] However, the development of AFCs has been severely restricted by sluggish kinetics of the oxygen reduction reaction (ORR), catalyst degradation and carbon support corrosion of commercial Pt/C.[4-6] The deterioration of Pt/C, which is highly correlated with the long-term operation hurdle, is one of the key issues to solve. The deterioration is caused by electrochemical corrosion (oxidation) of the carbon support at the cathode.[7-9] The corrosion is particularly accelerated during start-up and shut-down operations, during which the cathode potential can reach voltage of as high as 1.5 V.[10-13] Under these conditions, the carbon material is oxidized to carbon dioxide and/or carbon monoxide. This also leads to the aggregation and migration of Pt nanoparticles as well as their detachment from the carbon support. Therefore, the design of catalysts that can repair themselves under severe conditions has been identified as a primary challenge for fuel cells.[14, 15] Especially the catalysts for ORR require maintaining high activity at high potential during start-up and shut-down operations. Self-repair electrocatalysts for oxygen evolution reaction have been studied.[16, 17] While the self-repair electrocatalysts for ORR have been rarely reported. Herein, we present for the first time a tri-metallic PdAuCu nanobranched heterostructure as self-repair catalyst for ORR. In this heterostructured PdAuCu, the AuCu alloy serves as a stable support for Cu oxide/Pd heterogeneous interface (AuCu@CuxO/Pd). By tuning the oxidation state of Cu via high potential treatment (HPT), Cu (Ⅱ) was in-situ formed, which is responsible for repairing the catalyst. As the high potential is inevitably experienced at cathode during start-up and shut-down operations of a fuel cell, we proposed this catalyst as a “self-repair” catalyst in a broad sense. This work provides a novel strategy for fabricating efficient ORR catalysts by smartly utilizing the high potential during start-up and shut-down operations. The ORR activity and durability of PdAuCu after high potential heat-treatment (PdAuCu-HPT) are shown in Figure 1. Figure 1. (A) Mass activities of Pt/C, Pd/C, PdAuCu and PdAuCu-HPT at different cycles. ORR polarization curves of (B) initial Pt/C, initial Pd/C, PdAuCu-2000th-HPT and (C) initial Pd/C and Pd/C-2000th-HPT in O2-saturated 0.1 M KOH solution at room temperature, with a rotation rate of 1600 rpm and a potential sweep rate of 10 mV s-1. Acknowledgements This work is supported by National Natural Science Foundation of China (Nos.51272167 and 21206101 ).

Unsteady heat transfer performance of heat pipe with axially swallow-tailed microgrooves

A mathematical model is developed for predicting the transient heat transfer and fluid flow of heat pipe with axially swallow-tailed microgrooves. The effects of liquid convective heat transfer in the microgrooves, liquid-vapor interfacial phase-change heat transfer and liquid-vapor interfacial shear stress are accounted for in the present model. The coupled non-linear control equations are solved numerically. Mass flow rate at the interface is obtained from the application of kinetic theory. Time variation of wall temperature is studied from the initial startup to steady state. The numerical results are verified by experiments. Time constants for startup and shutdown operation are defined to determine how fast a heat pipe responds to an applied input heat flux, which slightly decreases with increasing heat load.

FORMULASI DAN UJI KINERJA ASPHALTENE DISSOLVER DENGAN PENGGUNAAN SURFAKTAN ANIONIK DARI MINYAK SAWIT

Asphaltene deposition is a major problem in petroleum industry causing slow production or even operational shutdown for removal of deposits. This research was conducted to obtain the best formulation of asphaltene dissolver to dissolve asphaltene deposits with the use of an palm oil anionic surfactant and to obtain performance information of asphaltene dissolver formula. The tested formulation were methyl ester sulfonate acid (MESA) and methyl ester sulfonate (MES), each with concentrations of 0%, 1%, 3%, and 5% in toluene mixed at a temperature of 40°C for 30 minutes. The best asphaltene dissolver produced was MESA 1% in toluene with the lowest interfacial tension (IFT) value of 3.95E-03 dyne/cm and solubility degree of 69.58%. Asphaltene dissolver produced showed a good performance in changing the wettability of rocks with an increase on contact angle of 48,6o to 80,89o, and increase wettability on metal surface with asphaltene release of 99.32% as well as showed good performance on dispersion, desorption and filtration.Keywords : asphaltene, asphaltene dissolver, anionic surfactant, MESA, MES

Three dimensional thermal hydraulic characteristic analysis of reactor core based on porous media method

Thermal-hydraulic performance in the reactor core was an essential factor in the nuclear power plant design. In this study, we analyzed the three-dimensional (3-D) thermal-hydraulic characteristic of reactor core based on porous media method. Firstly, a 3-D rector pressure vessel (RPV) model was built, including the inlet leg nozzle, downcomer, lower plenum, reactor core, upper plenum and outlet leg nozzle. Porous media model was used to simplify the reactor core and upper plenum. The commercial CFD code ANSYS CFX was employed to solve the governing equations and provide the 3-D local velocity, temperature and pressure field. After appropriate parameters and turbulent model being carefully selected, the simulation was validated against the 1:5 scaled steady-state hydraulic test. The predicted hydraulic parameters (normalized flowrate distribution and pressure drop) were in good agreement with the test results. And the predicted thermal parameters agreed well with the designed values. The validation indicated that this method was practicable in analyzing the 3-D thermal-hydraulic phenomena in the RPV. Finally, the thermal-hydraulic features in reactor core were analyzed under the condition of the Steam Generator Tube Rupture (SGTR) accident. The simulation results showed that the coolant temperature increased gradually from the center to the periphery in the reactor core in the accident. But the temperature decreased to safety level rapidly after the reactor shutdown and safety injection operation. The reactor core could keep in a safe state if appropriate safety operations were performed after accidents.

Analysis of loss of residual heat removal system for CPR1000 under cold shutdown operation

After Fukushima accident, the safety assessments within the full range of operation conditions for the current fleet of nuclear power plants in China are requested to be performed by the national nuclear safety administration. Accordingly, twelve typical cases were simulated to study the thermal-hydraulic behavior of loss of residual heat removal system for CPR1000 under cold shutdown operation with RELAP5/MOD3.3 code. The transient behaviors of system pressure, coolant temperature, water inventory, coolant boiling and core uncovering time, and other important parameters under 12 different plant configurations are predicted. The results indicate that the system pressure of cases with intact system increases continuously to the set value of 3.8MPa for opening the relief valve in the RHR system without any mitigation action. The starting time of coolant boiling highly depends on the initial water inventory in the RPV as well as its behavior during the initial stage after losing the RHR system, while the starting time of core uncovering highly depends on the plant configurations. The results of the study can provide references for the plant safety improvement and guideline for an operator to strategize a mitigation action.

PdAuCu Nanobranch as Self-Repairing Electrocatalyst for Oxygen Reduction Reaction.

During start-up and shut-down operations of fuel cells, high potential is inevitably experienced at cathode, which leads to the deterioration of the oxygen reduction electrocatalyst. The design of catalysts that can repair themselves under severe conditions has been identified as a primary challenge for fuel cells. Herein, self-supported PdAuCu branched nanostructure is synthesized by a hydrothermal method. By smartly utilizing the high-potential treatment, the activity of PdAuCu is significantly enhanced owing to the synergistic effect between the Pd and CuII generated by such treatment. Moreover, the high activity of PdAuCu can be well maintained by repeating the high-potential treatment. We hence propose this catalyst as a "self-repairing" catalyst in a broad sense.