Normal Plant Operation Research Articles

Verification of digital models of coolant self-oscillation of NPP with VVER

The results of verification of VVER-440 digital acoustic model are presented. The vibration control system of the main equipment, named SÜS, which is used in normal operation of nuclear power plants (NPP), is used to measure coolant pressure pulsations and mechanical vibrations. The method of calculation of acoustic standing waves (ASW) generated in the equipment is developed; the calculated values of ASW frequencies are in agreement with the results of measurements of signals from pressure pulsation sensors. It is proved that in the nominal and start-up modes, as a result of transformation of stochastic random pulsations caused by turbulence and vortex formation into ordered oscillations, acoustic waves appear. It is shown that the frequencies of acoustic waves depend on the operating conditions and can coincide with the vibration frequencies of the equipment. It is proved that the acoustic properties of a nuclear reactor, regardless of the number of coolant circulation loops, are similar to the properties of a group of simultaneously used Helmholtz resonators. The use of the acoustic model of the reactor allows optimizing design and engineering solutions by creating equipment capable of minimizing unwanted cyclic loads. This capability is the most important to ensure long - term operation in manoeuvrable modes of small modular reactors.

A Case Study on Procedure Standardization of Heat Exchanger Retubing in KSA Oil and Gas Industries

Plant shutdown also known as “turnarounds”, is one of the most critical period in the oil gas refineries in the Kingdom of Saudi Arabia. Shutdowns have the ability to effect the plant’s financial future and commitments either in positive or negative way. A heat exchanger is a crucial and important equipment in the oil gas refineries used for various processes and heat transfers. It also impacts the duration of plant turnaround. When the operation of the plant starts the after turnaround, a failed heat exchanger within short duration of normal plant operation even though warranty of contractor exists, can create major loss in terms of money due to reduced downtime or production loss. Heat exchangers are subjected to different repairs including partial or full retubing by various methods or by simple plugging. Heat exchanger repair during the turnaround helps to reduce the down time loss (repair) of heat exchanger and will ensure the integrity for smooth running of plant. After studying the retubing of more than 75 heat exchangers, standardized procedure was incorporated to satisfy all the standard codes like ASME, TEMA, SAES, SES, NBIC and all the end users like Aramco, Sabic and its affiliates.

Полевые методы исследования радиационной обстановки в районе размещения Белорусской АЭС в предэксплуатационный период

The article presents the results of field studies in the area of the Belarusian NPP in the pre-operational period. The «background» contents of gamma-emitting radionuclides in individual components of the environment are determined. The main array of dose rate measurements in the area of the NPP construction site is in the range 0.048 ÷ 0.089 μSv/h. External radiation in the surveyed area is formed at 96% due to 40K, 226Ra and 232Th. The information obtained can be used to correctly interpret the data of future radiation monitoring during normal operation of nuclear power plants.

The Effect of Different Branch Angles and Different Branch Pipe Sizes on the Onset Law of Liquid Entrainment

The T-junction is widely used in nuclear power plant systems. In order to ensure the normal operation of nuclear power plant, it is very important to study the onset point of T-junction liquid entrainment. Previous researches on the onset point of liquid entrainment have been lucubrated, but most of them are for small branch pipes. This paper is about the onset law of large branch pipe. In addition, the effect of branch angle and branch size on the onset point of liquid entrainment was analyzed by comparing with other branch pipe sizes in this paper. The onset phenomenon of liquid entrainment is described and the effect of angle on onset is studied in this research. It is found that the effect of branch angle on the onset point of entrainment is consistent with that of other sizes: as the angle between the branch pipe and the horizontal direction decreases, the onset needs greater Frg on condition of the same hb. The reason is that the decrease of the inertial force in the vertical direction acting on the liquid phase by the gas phase as the angle decreases. In addition, by comparing with the onset point law of liquid entrainment with different branch pipe sizes, we found the effect of branch pipe size on the onset is that the smaller branch pipe needs the greater gas velocity when onset occurs. The reason is that there is different flow resistance of different sizes of branch pipe.

Treatment of Penicillin Wastewater by Sequencing Batch Reactor

During the treatment of penicillin wastewater, facultative and aerobic bacteria in intermittent aeration can effectively degrade the organic matter in the wastewater without physical and chemical pretreatment of SO4 2- and DTAB. When the highest COD concentration of the influent is 12 000 mg/L, the load is 8 kgCOD/(m3·d), and the maximum impact load is 13 kg COD/(m3·d), COD removal rate can reach over 87%. The foam produced by DTAB in penicillin wastewater will not affect the normal operation of the SBR treatment plant. The foam can disappear in the aeration process, and eventually the DTAB can achieve more than 97% removal rate. Therefore, sequencing batch reactor is an ideal way to treat penicillin wastewater.

Efficient recovery of rare earth elements from coal based resources: a bioleaching approach

Rare earth element (REE) resources in coal-related materials are vast. Assuming a coal production rate of 600 million short tons per year with an average REE content of 200 ppm, the potential REE resource is 120,000 tons per year, which is similar to the annual global production of REEs. Most of those resources that are associated with coal-related materials are found in association with the gangue or ash-based content from the coal ore. Under normal coal plant operation, the REEs often end up in refuse piles or tailings impoundments. In many cases, these REEs can be recovered at low cost using appropriate coal preparation, heap leaching, solvent extraction and/or selective precipitation, followed by subsequent separation and purification of individual REEs. In the present research, the processing approach uses a natural pyrite stream, which was removed during coal cleaning and used to enhance leaching. Bio-oxidation has been used commercially to accelerate leaching, and this approach has been applied to coal-based materials. The ferric ions generated from bio-oxidation oxidize sulfide minerals such as pyrite, which generates acid. Both acid and ferric ions are helpful for leaching REEs, as well as for removing residual sulfides, thereby preventing future acid mine drainage and related liabilities. It can be seen that, recovery of REEs from coal waste materials can enable coal producers to use untapped REEs resources to produce revenue and extend resource life while simultaneously reducing future environmental issues and costs.

Simultaneous state and fuel property estimation in biomass boilers - theory and practice

A key factor for the further distribution of biomass boilers in modern energy systems is the capability of changing the applied feedstock during normal plant operation. This is only possible with the application of advanced control strategies that utilize knowledge about the state variables and varying fuel properties. However, neither the state variables nor the fuel properties are measurable during plant operation and, thus, need to be estimated. This contribution presents a method for the simultaneous real-time estimation of the state variables and the fuel properties in fixed-bed biomass boilers which is a novel approach in the field of biomass boilers. The method bases on an Extended Kalman Filter using a nonlinear dynamic model and measurement data from the combustion process. The estimated variables are the masses of dry fuel and water in the fuel bed as well as the fuel’s bulk density, water content, chemical composition and lower heating value. The proposed method is easy to implement and requires moderate computational effort which increases the potential of its application at actual biomass boilers. The proposed method is verified with simulation studies and by test runs performed at a representative small-scale fixed-bed biomass boiler. The estimation results show a good agreement with the actual values, demonstrating that the proposed method is capable of accurately estimating the biomass boiler’s state variables and simultaneously its fuel properties. For this reason, the presented method is a key technology to ensure the further distribution of biomass boilers in modern energy systems.

Применение удельного показателя для оценки объемов образования РАО при нормальной эксплуатации АЭС России

Generation of radioactive wastes (RW) is viewed a most urgent problem of radiation safety under normal operation of nuclear power plants (NPP). The paper demonstrates the application of a specifi c indicator (rate) of RW generation per unit of generated power (m3/GW·h) for a retrospective assessment and forecasting of RW generation volumes at Russian NPPs. Mean and median values of annual specifi c RW generation rates were calculated for each NPP based on published environmental reports of JSC Rosenergoatom Concern for the period of 2008—2018. Advantage of applying median values in retrospective and forecast assessments was shown. Medians for solid very low-level, low-level, intermediate-level and high-level radioactive waste amounted to 1.5·10−2 m3/GW·h, 3.3·10−2 m3/GW·h, 3.3·10−3 m3/GW·h and 2.8·10−4 m3/GW·h, respectively; for liquid low-level and intermediate-level waste these values accounted for 1.4·10−3 m3/GW·h, 2.5·10−3 m3/GW·h, respectively. NPPs with RBMK reactor units are characterized by the highest mean and median values of specifi c RW generation rates for all RW categories. Given various types of reactor facilities and their characteristic specifi c rates, retrospective estimates for the total volume of liquid RW was increased by 8 % and for solid RW — by 12 %. The forecast estimates based on specifi c rate medians, as well as on increased power generation planned for Russian NPPs indicates probable increase in RW generation volumes by 0.8—7.1 % (depending on waste category) from 2020 to 2027.

Research review on Transformer Fire Protection Technology

Transformer is the core equipment in power plant and substation. Its safety problem directly affects the normal operation of the whole power plant or substation. In the event of fire, it not only affects the normal operation and system load of the system, but also affects the normal operation and load of the system. In this paper, the main causes of transformer fire, fire pre-warning technology and fire extinguishing technology are introduced comprehensively. A on-line detection fire warning technology without blackout is proposed by analyzing transformer operating noise. Finally, the substation fire protection technology from the aspect of civil engineering design is introduced briefly.

Developing Turnaround Maintenance (TAM) Model to Optimize TAM Performance Based on the Critical Static Equipment (CSE) of GAS Plants

Many oil and gas companies have suffered major production losses, and higher cost of maintenance due to the total shutdown of their plants to conduct TAM event during a certain period and according to scope of work. Therefore, TAM is considered the biggest maintenance activity in oil and gas plant in terms of manpower, material, time and cost. These plants usually undergo other maintenance strategies during normal operation of plants such as preventive, corrective and predictive maintenance. However, some components or units cannot be inspected or maintained during normal operation of plant unless plant facilities are a totally shut downed due to operating risks. These risks differ from a company to another due to many factors such as fluctuated temperatures and pressures, corrosion, erosion, cracks and fatigue caused by operating conditions, geographical conditions and economic aspects. The aim of this paper is to develop a TAM model to optimize the TAM scheduling associated with decreasing duration and increasing interval of the TAM of the gas plant. The methodology that this paper presents has three stages based on the critical and non-critical pieces of equipment. At the first stage, identifying and removing Non-critical Equipment pieces (NEs) from TAM activity to proactive maintenance types. During the second stage, the higher risk of each selected equipment is assessed in order to prioritize critical pieces of equipment based on Risk Based Inspection (RBI). At the third stage, failure probability and reliability function for those selected critical pieces of equipment are assessed. The results of development of the TAM model is led to the real optimization of TAM scheduling of gas plants that operated continuously around the clock in order to achieve a desired performance of reliability and availability of the gas plant, and reduce cost of TAM resulting from the production shutdown and cost of inspection and maintenance.

Radioiodine Release into the Atmosphere during Normal Operation of Nuclear Power Plants

The specific emission rates of iodine isotopes into the atmosphere during normal operation of European and Russian NPPs with different types of reactor facilities were analyzed. The probability distributions for the specific parameters are asymmetric, and their median values tend to decrease. Three categories of NPPs were distinguished: those with the best, worst, and stable practice of the 131I emission. The current global atmospheric release of 129I from all the NPPs in the world is estimated at 0.8 kBq year−1. With an increase in the total installed NPP capacity to 632 GW, the global release of 129I from the NPP emissions will increase to 1.4 kBq year−1, which is two times lower than the rate of natural production of this nuclide from atmospheric Xe isotopes under the action of cosmic rays. Based on the measurements performed at separate Russian NPPs, the contribution of the aerosol and gaseous iodine forms to the total volume activity of the released iodine isotopes was determined. Under the conditions of normal NPP operation, gaseous iodine compounds make the prevalent contribution to the radioiodine emissions (65–85%).

Hydrodynamic model of radionuclide dispersion during normal operation and accident of Bushehr nuclear power plant

Several numerical models have been developed to simulate the dispersion of radionuclides in the aqueous environments. In this research, the 2-dimensional depth averaged hydrodynamic model is applied to obtain the current components in a part of Persian Gulf taking into account the tidal effects. The hydrodynamic equations solved by a finite differential approach. In this model the time step is 5 s (totally for 3 days) and spatial step is 10 Km. From the mainstream in the study area, it is also found that the velocity of water in the central region and near Iran's shore lines is higher than the other places. Using the average value of the speed from hydrodynamic equation, the concentration of some radioactive elements is also obtained by CROM tool.

The health risk-benefit feasibility of nuclear power development

Although nuclear power has gradually played an important role in world's energy consumption, there is still controversy because of the threat of releasing harmful radioactive substances. The public's incomplete understanding of nuclear power's risks and benefits has led to the Not In My Back Yard (NIMBY) effects all over the world, especially in developing countries. It is important to analyze the role that nuclear energy plays for human society in a multidimensional manner. Previous studies have investigated the benefits and risks of nuclear power, which mainly focus on economic benefits, and carbon or pollution emissions reduction benefits. Quantitative study on the comparison of health risks and benefits has been lacking. By taking China as an example, we compared the health risks and benefits of nuclear power using a health impact assessment methodology framework. The results show that, under normal operating conditions, the maximum annual disability adjusted life years (DALYs) caused by a single nuclear power plant would be 2.2 h and 11.4 h in 2020 and 2030, respectively. In 2030, the DALYs of the population exposed for 8 h within approximately 80 km of a plant would be between 108 and 9199 years in a severe accident scenario. The health benefits of nuclear power were calculated by avoided DALYs of reduced SO2, NOX, and PM10 of coal-fired power substituted by nuclear power. The avoided DALYs would be 501.0–1658.1 years and 676.4–2942.4 years in 2020 and 2030, respectively. Considering that risk equals consequence multiplied by the probability, developing nuclear power is risk-benefit feasible. More precise risk prevention, control measures and emergency plans (for both normal operation and accident conditions) of nuclear power plant should be put into place, and risk communication should be strengthened (e.g., bringing the scientific-based risk-benefit assessment results to the public, etc.) to reduce the public's NIMBY effects.

Technical approaches to calculating different components of the annual effective dose due to release of actinides into air during long-term operation of a BN-type reactor

The aspect of ensuring NPP safety has always attracted scrupulous attention. Experience in operating power plants with different reactor types shows that radiation situation in the NPP area, environmental contamination depend very much on the integrity of the fuel cladding – one of the most important protective barriers.In practice, some fuel pins in the core can have certain cladding defects occurring during the normal plant operation, with a BN-type reactor used. Np, Pu, Am, Cm transuranic elements may take special part in contaminating the primary circuit with actinides. Presence of actinides in the process media of the reactor facility may have radiation effect not only on the NPP staff but also on the population living outside the buffer area.There is little information on the problem in scientific publications. Computer codes are mainly oriented to the calculation of the effective doses the population take as a result of release of radionuclides into the air during the first year of NPP operation. Increasing the duration of NPP operation results in significantly complicated calculations. This paper presents a simplified method of calculating the main components of the annual effective dose the population receive due to release of actinides into the air over «n» partial refuelings after reactor startup.

Study on Condition Monitoring and Evaluation of Auxiliary Engine of Steam Turbine Based on Matter-element Theory

As an important equipment in thermal production process of thermal power unit, auxiliary equipment of steam turbine, such as feed-water pump, whether it can operate safely and economically is very important for normal operation of thermal power plant. Considering that the auxiliary machine on the side of the steam turbine of a power plant has the characteristics of high failure rate, a state monitoring and evaluation method based on the matter-element theory is proposed. Based on the establishment of the monitoring index and evaluation model of the auxiliary engine on the side of the steam turbine, the correlation degree between the main operating parameters of the auxiliary engine and the monitoring model is determined. According to the value of correlation degree, the operating condition of auxiliary machine is judged to be excellent, good, qualified or malfunction. Finally, a 300MW steam feed pump is taken as an example to prove that this method has certain engineering application value.

Аналіз основних засобів забезпечення водно-хімічного режиму АЕС

Водно-хімічний режим (ВХР) повинен бути спрямований на забезпечення і підтримання норм якості водного теплоносія і стану внутрішніх поверхонь обладнання основного контуру для досягнення безаварійної роботи устатковання АЕС. Водно-хімічний режим АЕС повинен забезпечувати безпечну кількість відкладень на поверхнях тепловиділяючих елементів і технологічних каналів, допустимі швидкості корозії конструкційних матеріалів основного пароводяного тракту, а також високу якість насиченої пари, що не спричиняє неприпустимих відкладень у турбіні. До засобів забезпечення водно-хімічного режиму АЕС відносять післямонтажну підготовку обладнання основних і допоміжних контурів, безперервне продування контуру багаторазової примусової циркуляції (КМПЦ) за номінальних режимів установок спецводоочищення (СВО-1); очищення всього потоку турбінного конденсату на фільтрах конденсатоочищення; підготовку додаткової води на хімводоочищення і на (СВО-4); очищення підживлювальної води на установках спеціального водоочищення (СВО-5), дегазацію турбінного конденсату і живильної води в деаераторі турбіни; хімічний контроль, що полягає у визначенні нормовано контрольованих показників водного теплоносія для установлення рівня його якості та оцінювання засобів забезпечення водно-хімічного режиму. Тому від ступеня чистоти води і водяної пари та рівня підтримки корекційних добавок залежить надійна робота обладнання.

Failure analysis of subsidence in an effluent treatment plant in a thermosolar power plant

Abstract An essential section in the normal operation of a thermosolar power plant is the management of those effluents that are generated by the diverse processes that take place in the power plant equipment. Due to environmental regulations, it is necessary to develop an effluent treatment plant before all those fluids can be discharged into the environment. In such a plant, a neutralization process is performed, by adding certain chemicals, resulting in an environmentally safe spill. During the execution of this kind of facility in La Asturiana thermosolar power plant, all design requirements were fulfilled, without any incident. Nevertheless, during the commissioning of the facility, several pieces of equipment showed settlements that were much higher than the established limits, which led to a temporary shut-down of the facility. In order to discover the causes, evaluate the risk of repetition in other areas of the power plant and to be able to select the best corrective action, a forensic study was carried out. This study started with several field data tests and was concluded with the development of a computer model. The above mentioned study focused on one of the affected pieces of equipment, and on the surprising conclusions obtained with regard to the causes of the incident, which are developed in the present article.

Implementation and validation of a resuspension model in MELCOR 1.8.6 for fusion applications

In a fusion reactor, a continuous erosion of the Plasma Facing Surfaces (PFSs) occurs during normal plant operations. This erosion creates a particles debris (dust) spanning from 1μm to 50μm in dimension. These formed dust deposits on the bottom of the Vacuum Vessel (VV), i.e. on the divertor surface. In case of Beyond Design Basis Accident (BDBA), this dust may be mobilized and transported towards the confinement building, or even into the outer environment. Therefore, the evaluation of the maximum mobilized dust mass is a safety issue of main concern, because it may pose a radiological risk to plant operators and to the outer population. To investigate these incidental scenarios, lumped-parameters codes such MELCOR are commonly employed. A specific version of MELCOR, capable to treat the phenomena occurring in a fusion reactor, is developed by Idaho National Laboratory (INL). Although, a model to treat the mobilization of dust is still not yet implemented in this specific MELCOR version. This paper presents, after a review of the available resuspension models, the selection of a specific resuspension model and the efforts made for its validation against different experimental tests. The selected model is the semi-empirical “Force Balance” model, just implemented in the ASTEC and ECART codes, but specific modifications were introduced to allow its implementation in MELCOR through ad hoc developed Control Functions (CFs). Its validation shows a quite good agreement with most of the experimental tests investigated, highlighting its capabilities for the safety analysis of the forthcoming fusion reactors.

Calculating Technical and Economical Indexes and Providing Normal NPP Operation

In the nuclear power engineering, methods of detecting faults and diagnostics play increasing role, as well as systems of information operator support in order of increasing the safety and operation reliability. One of problems solved within the information support system, there is the task of calculating technical and economical indexes and its connection with providing the model of normal nuclear power plant operation.

Prediction of the moderator temperature field in a heavy water reactor based on a cellular neural network

Reactors with heavy water coolants and moderators have been used extensively in today's power industry. Monitoring of the moderator condition plays an important role in ensuring normal operation of a power plant. A cellular neural network, the architecture of which has been adapted for hardware implementation, is proposed for use in a system for prediction of the heavy water moderator temperature. A reactor model composed in accordance with the CANDU Darlington heavy water reactor design was used to form the training sample collection and to control correct operation of the neural network structure. The sample components for the adjustment and configuration of the network topology include key parameters that characterize the energy generation process in the core. The paper considers the feasibility of the temperature prediction only for the calandria's central cross-section. To solve this problem, the cellular neural network architecture has been designed, and major parts of the digital computational element and methods for their implementation based on an FPLD have also been developed. The method is described for organizing an optical coupling between individual neural modules within the network, which enables not only the restructuring of the topology in the training process, but also the assignment of priorities for the propagation of the information signals of neurons depending on the activity in a situation analysis at the neural network structure inlet. Asynchronous activation of cells was used based on an oscillating fractal network, the basis for which was a modified ring oscillator. The efficiency of training the proposed architecture using stochastic diffusion search algorithms is evaluated. A comparative analysis of the model behavior and the results of the neural network operation have shown that the use of the neural network approach is effective in safety systems of power plants.