Power Shutdown Research Articles

An MILP Formulation for the Thermal Unit Commitment Problem Considering Start-Up and Shut-Down Power Trajectories

This paper presents a mixed-integer linear formulation for the thermal unit commitment problem considering the start-up and shut-down power trajectories. A realistic and accurate modeling of the unit’s operating phase is given, which includes the phases of start-up, dispatchable and shut-down. The start-up type is decided by the unit’s prior off-line time. The start-up costs and power trajectories depend on the type of start-up. A new set of binary variables is introduced to represent the dispatchable status, which can decrease the binary variables and constraints significantly. Finally, a test case study is analyzed to verify the correctness and show the computational performance of the proposed formulation.

Corrosion of ruthenium dioxide based cathodes in alkaline medium caused by reverse currents

A reverse current obtained during power shutdowns in industrial processes, such as chlor-alkali production or alkaline water electrolysis, is deleterious for hydrogen evolving ruthenium dioxide (RuO2) based cathodes. It has been observed that RuO2 coatings after a power shutdown, necessary for e.g. maintenance, are severely damaged unless polarization rectifiers are employed. In this work we show why these types of cathodes are sensitive to reverse currents, i.e. anodic currents, after hydrogen evolution. RuO2 coatings deposited on nickel substrates were subjected to different electrochemical treatments such as hydrogen evolution, oxygen evolution, or reverse currents in 8M NaOH at 90°C. Polarity inversion was introduced after hydrogen evolution to simulate the effect of reverse currents. Because of chemical interaction with hydrogen, a significant amount of the RuO2 coating was transformed into hydroxylated species during cathodic polarization. Our study shows that these hydroxylated phases are highly sensitive to electrochemical corrosion during anodic polarization after extended hydrogen evolution.

Sensitivity study on in-box LOCA for a Korean HCCR TBM in ITER

Korea has designed a Helium-Cooled Ceramic Reflector (HCCR)-based Test Blanket System (TBS) for International Thermonuclear Experimental Reactor (ITER). Among seven selected reference accidents in Korean TBS, in-box loss of coolant accident (LOCA) is one of them. This is initiated by a double-ended break of the coolant pipe in the Breeding Zone (BZ), pressurizing the BZ box structure, causing pressurization of the Tritium Extraction System (TES) and purging of pipelines. When the accident is detected, the Plant Safety System (PSS) isolates the Helium Cooling System (HCS) and TES, and requests plasma shutdown to Fusion Power Shutdown System (FPSS). To prevent aggravating failure of the system, the safety function is automatically activated when the accident is detected, the device being the isolation valve of HCS and TES. One important observation of this accident is that instant isolation is not a good measure to take. In terms of the possibility of aggravating failure, system isolation is an important safety procedure but isolated TES volume is exposed to high pressure and temperature conditions in the early move of the accident transient. The result of system safety analysis shows that delayed isolation keeps the system safe for a while. In this article, given the preliminary accident analysis results for the current HCCR TBS, case studies were performed regarding the delayed isolation timing effect. For this transient simulation, Korean nuclear fusion reactor safety analysis code (GAMMA-FR) was used.

원자력발전소 직류전원계통용 축전지 성능시험 분석

Function of battery bank stores energy for DC load in general, and DC power system of the nuclear power plant is used to supply DC loads for safety- featured instrumentation and control such as inverter, class 1E power system control and indication, and station annunciation. Class 1E DC power system must provide a power for the design basis accident conditions, and adequate capacity must be available during loss of AC power and subsequent safe shutdown of the plant. In present, batteries of Class 1E DC power system of the nuclear power plant uses lead-acid batteries. Class 1E batteries of nuclear power plants in Korea are summarized in terms of specification, such as capacity, discharge rate, bank configuration and discharge end voltage, etc. This paper summarizes standards of determining battery size for the nuclear power plant, and analyzes duty cycle for the class 1E DC power system of nuclear power plant. Then, battery cell size is calculated as 2613Ah according to the standard. In addition, this paper analyzes performance test results during past 13 years and shows performance degradation in the battery bank. Performance tests in 2001 and 2005 represent that entire battery cells do not reach the discharge-end voltage. Howeyer, the discharge-end voltage is reached in 14.7% of channel A (17 EA), 13.8% of channel B (16 EA), 5.2% of channel C (6 EA) and 16.4% of channel D (19 EA) at 2011 performance test. Based on the performance test results analysis and size calculation, battery capacity and degradation by age in Korearn nuclear power plant is discussed and would be used for new design.

Dissolved oxygen and idle time effects on sewage bioremediation

This paper explores the effects of dissolved oxygen (DO) concentrations and idle time on the performance of aerated-sludge portable sewage systems for rapid deployment during natural calamities or warfare. Using synthetic sewage, three different reactors were operated at DO levels of 2–6 mg/l to determine the optimum DO for reactor performance, chemical oxygen demand (COD) and total organic content (TOC) removal, pH, conductivity and biomass concentrations. Low DO values result in very low COD removal efficiency, while DO levels over 6 mg/l are not significantly more efficient. The oxygen utilisation rate and specific oxygen utilisation rate were in the ranges 0·87–1·08 mg O2/h and 0·44–0·895 mg O2/g MLSS (mixed liquor suspended solids) per hour respectively for the three reactors. The highest achieved specific removal rate was 14 mg/g MLSS per hour and 6 mg/g MLSS per hour for COD and TOC respectively. Investigation of idle time (no-aeration) revealed that an idle time of less than 24 h results in low removal efficiency (COD and/or TOC) but the system recovers in the next 24 h; however, an idle period of 48 h or greater results in very poor efficiency and may cause permanent failure of the bioremediation process. The results of the present study can be applied to avoid system failure in a sewage treatment system as a result of, say, intermittent or sudden power shutdown.

福島第一原子力発電所1号機事故の熱流動現象推定（熱力学モデルによる非常用凝縮器（IC）の挙動）

In order to investigate the process of accident of Fukushima Nuclear Power Plants, an accident scenario of Fukushima Daiichi Nuclear Power Plant, Unit 1 is analyzed from the data open to the public. Phase equilibrium process model and adiabatic expansion model were introduced. Original data reported in the first stage of the accident were examined to clarify the behavior of the isolation condensers (ICs) which are generally believed unfunctional after the arrival of Tsunami and station blackout. The original data and observation reports verified that the so called “fail safe” system to close the valves in IC did not work properly due to the shutdown of AC power. The reports also showed the evidence that the operators injected water to the storage tank of IC. We proposed a scenario that IC was operational until approximately at 3/12 3:00, small leakage occurred at the reactor pressure vessel (RPV) at the initial stage of the accident, the RPV ruptured at 3/12 6:20, and it ruptured again in approximately at 3/12 16:00. We assumed that PCV ruptured at 3/12 3:00, and the area of rupture did not change after the hydrogen explosion occurred at 3/12 15:36. The present analysis model describes the data measured at the accident, and many evidences and witnesses reported at the early stage of the accident. We also simulated according to the scenario of Tokyo Electric Power Company (TEPCO) that the ICs did not work after the Tsunami arrival. The estimation by the present analysis agrees with the TEPCO's one, however, there are many discrepancies that cannot explain the behavior of the reactor accident.

An MIP Formulation for Joint Market-Clearing of Energy and Reserves Based on Ramp Scheduling

The day-ahead unit-commitment (UC)-based market-clearing (MC) is widely acknowledged to be the most economically efficient mechanism for scheduling resources in power systems. In conventional UC problems, power schedules are used to represent the staircase energy schedule. However, the realizability of this schedule cannot be guaranteed due to the violation of ramping limits, and hence conventional UC formulations do not manage the flexibility of generating units efficiently. This paper provides a UC-based MC formulation, drawing a clear distinction between power and energy. Demand and generation are modeled as hourly piecewise-linear functions representing their instantaneous power trajectories. The schedule of generating unit output is no longer a staircase function, but a smoother function that respects all ramp constraints. The formulation represents in detail the operating reserves (online and offline), their time deployment limits (e.g., 15 min), their potential substitution, and their limits according to the actual ramp schedule. Startup and shutdown power trajectories are also modeled, and thus a more efficient energy and reserves schedule is obtained. The model is formulated as a mixed-integer programming (MIP) problem, and was tested with a 10-unit and 100-unit system in which its computational performance was compared with a traditional UC formulation.

FPGA Implementation of Adaptive Digital Predistorter With Fast Convergence Rate and Low Complexity for Multi-Channel Transmitters

This paper reports an adaptive digital predistorter (DPD) with fast convergence rate and low complexity for multi-channel transmitters, which is fully implemented in a field programmable gate array. The design methodology and practical implementation issues are discussed, with concerns about the impact caused by carrier power shutdown and transmission power control. The proposed DPD is composed of multiple adaptive lookup table (LUT) units of uniform structures, allowing configurability for desired memory depth. A simplified multiplier-free normalized least mean square algorithm for fast adapting the LUT is introduced. The proposed DPD is also experimentally exploited to linearize a Doherty amplifier. The adjacent channel leakage ratio reaches -60 dB for both lower and upper bands in the test applying a long-term evolution signal. It is also demonstrated in this paper that the proposed DPD shows high robustness when a multi-channel global system for mobile communications signal with occasional carrier power shutdown is applied.

DC Smart Grid Connected with Fuel Charging Station and AC Load by Hybrid MLI

This paper presents the Solar (photo voltaic) power Plant and Windmill plant with DC Smart Grid connected with an DC Fuel Charging Station For Electric Vehicle (EV), Plug in Hybrid Electric Vehicle (PHEV) and converted to AC load for Consumer single or Three phase ac load by means of Hybrid Multilevel Inverter (MLI). Solar Energy which store energy in lithium-ion battery and connected to Smart Grid .Wind Energy which get stored in Lithium-ion battery that Fixed DC Voltage connected with DC Smart Grid. Smart Grid which are Connected with DC Fuel Charging Station in Ring Topology with a certain distance for charging of Electric Vehicle (EV) and Plug-in Hybrid Electric Vehicle with On-Board (Integrated) Charger for faster charging of EV. In Power demand for Consumer the DC load from smart grid converted into an ac load by Hybrid Multilevel Inverter. In Consumers Place the small wind mill and PV panel are installed that energy can be used for consumers load at peak time or power Shutdown .Other than the power shutdown or peak time in the consumers place, stored DC Energy can be fed to Smart Grid. A major development in distribution automation is deployment of smart meters as a gateway between the utility and customer. With such capabilities the smart meter becomes not only a point of measurement of consumed kWh but also a controller capable of bidirectional communications with both the customer and utility. DOI: http://dx.doi.org/10.11591/ijpeds.v3i3.3884

Fracture and Creep in an All-Tungsten Divertor for ARIES

The ARIES project is currently proposing an all-tungsten divertor for their tokamak designs. In designing such a component, fracture will be a critical failure mechanism, due to the limited ductility of the tungsten. Hence, this paper presents a series of fracture mechanics-based analyses to demonstrate the feasibility of using an all-tungsten divertor in a commercial device. The analyses presented here employ a commercial finite element code (ANSYS) to carry out three-dimensional thermal, mechanical, and fracture calculations. Due to the inelastic deformations produced by the high temperatures and stresses in the component, the fracture calculations employ the J-Integral, a path-independent contour integral that estimates the strain energy release rate for a crack of assumed geometry. Elliptical surface cracks are introduced both inside and outside the coolant channel and steady state calculations are carried out for both full power and cold shutdown conditions. It is determined that the critical crack is on the inside of the coolant channel and the largest forcing is during full power. In addition, transient calculations are carried out to simulate edge localized modes (ELMs) in the plasma and conclusions are drawn with respect to the severity of these events and their effect on the lifetime of the component. Finally, thermal creep is considered as a potential failure mode.

Asynchronous Permanent Magnet Coupler Hydraulic Coupler and Performance Analysis

This paper analyzes the three major problems exist in the long-term use of hydraulic coupler, a temperature rise effect is the hidden trouble of the normal operation of equipment; two is the site difficult to accurately control the charging liquid, starting power balance and shutdown can not control the scraper conveyer; three is the property of medium effects factors of hydraulic coupling torque; introduces the working principle of asynchronous magnetic coupling and unique five technical characteristics. The asynchronous magnetic coupling and hydraulic coupler has obvious technical advantages compared, can solve the long-standing hydraulic coupler in the production practice expect to solve urgently and has failed to solve the problem. Conclusion is the soft starter for asynchronous magnetic coupling for scraper conveyor is completely feasible.

Temperature-Compensated dB-linear Digitally Controlled Variable Gain Amplifier With DC Offset Cancellation

This paper presents a compact digitally controlled variable gain amplifier (DVGA) with capabilities of both temperature compensated linear-in-decibel (dB-linear) gain control and dc offset cancellation (DCOC) without making use of either the feedback or the feed-forward loop. The proposed DVGA design is a three-stage inductorless cascaded amplifier that is integrated with a temperature-compensated dB-linear gain control, a DCOC, an output common mode feedback, a 6-bit digital gain control (with a 64-step resolution), a power shutdown mode, and a linearizer for improving the 1-dB gain compression point. The design is fabricated using a commercial 0.18-μm SiGe BiCMOS technology. The DVGA has a measured gain range of 18.4 dB with an average step size of 0.3 dB, a 3-dB bandwidth from 2 MHz to 1.9 GHz with a ±0.75-dB gain flatness from 2.75 MHz to 1.2 GHz, an input 1-dB gain compression point better than -12.5 dBm, an input return loss better than 12 dB, an output return loss better than 16 dB, and a dc power consumption of 12.2 mW from a 1.8-V supply. The core DVGA, by excluding the I/O measurement pads, occupies a die area of 160 μm × 300 μm.

Assessment of the economic impact of environmental constraints on annual hydropower plant operation

Environmental constraints imposed on hydropower operation are becoming increasingly restrictive. These constraints may reduce the operational flexibility of a hydro plant and therefore its revenue. The objective of this paper is to assess the economic impact of minimum environmental flows and maximum ramping rates on the annual operation of a hydropower plant. For this purpose, a revenue-driven annual optimization model based on discrete dynamic programming and mixed integer linear programming is used. The model considers hourly water inflows and energy prices, limits on reservoir level and water discharge, power generation dependence on the available head, wear and tear costs of hydro units caused by power variations, start-up and shut-down costs of hydro units, and the above-mentioned environmental constraints. In order to show the applicability of the proposed methodology, it is used in a real hydropower plant under five different water year types and 56 distinct combinations of the considered environmental constraints. The results indicate that the revenues of the hydropower plant are very sensitive to the presence and magnitudes of these constraints. Annual losses increase quadratically as a function of the maximum ramping rates and almost linearly as a function of the minimum environmental flows.

An assessment of nuclear power shutdown in Japan using the computable general equilibrium model

Following the Great East Japan earthquake and the resulting tsunami, the accident at the Fukushima Daiichi nuclear power station has caused public anxiety with respect to existing nuclear power reactors in Japan. Th is has made it difficult for the local government to give permission to allow the suspended nuclear power reactors to resume activity after their scheduled check up. Japan would have to balance its electricity supply and demand with zero or very few operating nuclear power reactors in 2012. In that case, the gap between electricity supply and demand would have to be closed using high-cost fossil fuel power generation. The purpose of this study is to assess the economy-wide impacts of total nuclear power shutdown in Japan using a multi-regional, multi-sectoral, static computable general equilibrium model. The results of this study indicate that immediate total nuclear power shutdown in Japan would have a considerable negative impact on the country’s economy and carbon dioxide emissions. The negative economic impacts would differ among regions depending on their nuclear dependency, and could further accelerate the rise in regional economic disparity.

Tight and Compact MILP Formulation of Start-Up and Shut-Down Ramping in Unit Commitment

This paper presents a mixed-integer linear programming (MILP) formulation of start-up (SU) and shut-down (SD) power trajectories of thermal units. Multiple SU power-trajectories and costs are modeled according to how long the unit has been offline. The proposed formulation significantly reduces the computational burden in comparison with others commonly found in the literature. This is because the formulation is 1) tighter, i.e., the relaxed solution is nearer to the optimal integer solution; and 2) more compact, i.e., it needs fewer constraints, variables and nonzero elements in the constraint matrix. For illustration, the self-unit commitment problem faced by a thermal unit is employed. We provide computational results comparing the proposed formulation with others found in the literature.

Concept design of fusion power shutdown system for ITER

ITER is a nuclear facility. It is essential to maintain operational safety or to bring this facility to a safe state in case of accidents or incidents. During plasma operation ITER plasma will generate significant heat loads on the plasma facing components. For a few reference accidents there is the need to stop plasma reliably within a certain time. Fusion power shutdown system is the safety system to implement this termination function for ITER. It is based on the concept of massive gas injection.This paper summarizes the safety requirements, logics and the physics requirements on this system for reliable termination of ITER plasma. With regard to the quantity of gas, transient behavior simulation is shown, subsequently providing guideline for laboratory bench-testing. Conceptual engineering design of the system is given together with instrumentation and control specifications.

A camera and multisensor automated station design for polar physical and biological systems monitoring: AMIGOS

AbstractThe Automated Meteorology–Ice/Indigenous species–Geophysics Observation System (AMIGOS) consists of a set of measurement instruments and camera(s) controlled by a single-board computer with a simplified Linux operating system and an Iridium satellite modem supporting two-way communication. Primary features of the system relevant to polar operations are low power requirements, daily data uploading, reprogramming, tolerance for low temperatures, and various approaches for automatic resets and recovery from low power or cold shutdown. Instruments include a compact weather station, single- or dual-frequency GPS, solar flux and reflectivity sensors, sonic snow gauges, simplified radio-echo sounder, and resistance thermometer string in the firn column. In the current state of development, there are two basic designs. One is intended for in situ observations of glacier conditions. The other supports a high-resolution camera for monitoring biological or geophysical systems from short distances (100 m to 20 km). The stations have been successfully used in several locations for operational support, monitoring rapid ice changes in response to climate change or iceberg drift, and monitoring penguin colony activity. As of August 2012, there are nine AMIGOS systems installed, all on the Antarctic continent or in the surrounding ocean.

Exit economics: The relatively low cost of Germany’s nuclear phase-out

The decision of the German government, post-Fukushima, to phase out the country’s nuclear power sector by 2022 builds on legislation in place since 2002. This earlier legislation was amended in 2010 to extend the lifetime of the nuclear plants, but the German parliament reversed this extension in the summer of 2011, slightly accelerating the original phase-out schedule; therefore, the market and the nuclear operators were prepared for the shutdown schedule. In this context, it is not surprising that the observed price impacts from the shutdown of 40 percent of the German nuclear power capacity in 2011 are smaller than some modeling exercises had projected. When empirical observation is analyzed in light of a range of economic models, the price effect of the nuclear phase-out can be expected to peak at 5 euros per megawatt-hour or less for a few years around 2020, a reasonably small increase compared with the uncertainties created by other fundamental determinants of Europe’s electricity prices. The macroeconomic effects attributable to the complete shutdown of nuclear power also appear likely to be relatively small, peaking at perhaps 0.3 percent of gross domestic product or less a few years before 2030. In the end, the management of the German transition to an energy mix dominated by renewable energies—and not the use of the existing nuclear reactor fleet for a decade more or less—will be the key determinant of whether that shift has larger or smaller effects on electricity prices or on the German economy overall.

Thermal–hydraulic and safety analysis for Chinese helium-cooled solid breeder TBM cooling system

The thermal–hydraulic behavior and safety performance of the Chinese helium-cooled solid breeder (CH HCSB) test blanket module (TBM) with helium cooling system (HCS) has been studied using RELAP5/Mod3.4 code. According to accident analysis specification for TBM, two design basis accidents including loss of off-site power and TBM first wall (FW) ex-vessel coolant pipe break are investigated. The influences of different break locations and plasma termination behaviors are analyzed comprehensively. The results show that natural circulation is established in helium cooling circuit and the TBM can be cooled effectively after loss of off-site power. It is much more critical when the pipe break occurs at the downstream side of the circulator compared with that of upstream side of the circulator. In case of a more serious accident that the ex-vessel break extends to the TBM FW, the results reveal that TBM could be cooled down by natural circulation and radiation. In addition, at the beginning of ex-vessel loss of coolant accident (LOCA), large temperature difference between break and intact TBM FW pipes is found. The accidental results finally show that the integrity of the FW can be guaranteed if the plasma is terminated with a 3s delay time by fusion power shutdown system (FPSS) in the case of ex-vessel LOCA.

EVALUATION OF GALVANIC CORROSION BEHAVIOR OF SA-508 LOW ALLOY STEEL AND TYPE 309L STAINLESS STEEL CLADDING OF REACTOR PRESSURE VESSEL UNDER SIMULATED PRIMARY WATER ENVIRONMENT

The article presented is concerned with an evaluation of the corrosion behavior of SA-508 low alloy steel (LAS) and Type 309L stainless steel (SS) cladding of a reactor pressure vessel under the simulated primary water chemistry of a pressurized water reactor (PWR). The uniform corrosion and galvanic corrosion rates of SA-508 LAS and Type 309L SS were measured in three different control conditions: power operation, shutdown, and power operation followed by shutdown. In all conditions, the dissimilar metal coupling of SA-508 LAS and Type 309L SS exhibited higher corrosion rates than the SA-508 base metal itself due to severe galvanic corrosion near the cladding interface, while the corrosion of Type 309L in the primary water environment was minimal. The galvanic corrosion rate of the SA-508 LAS and Type 309L SS couple measured under the simulated power operation condition was much lower than that measured in the simulated shutdown condition due to the formation of magnetite on the metal surface in a reducing environment. Based on the experimental results, the corrosion rate of SA-508 LAS clad with Type 309L SS was estimated as a function of operating cycle simulated for a typical PWR.