Operation Of Nuclear Power Plants Research Articles

Waste-specific volume for retrospective, predictive assessments, and ranking of practices during normal operation of Russian nuclear power plants

Possibilities of applying the generated radioactive waste-specific volume per unit of produced electricity are shown. This waste specific volume is used for retrospective assessment and forecasting of radio active waste volumes generated at Russian nuclear power plants. According to the available data period covering 2008-2021, the mean and median values of the annual waste-specific volume for each nuclear power plant were obtained. The medians for solid radioactive wastes divided into the categories of very low-level wastes, low-level wastes, intermediate level wastes and high-level wastes are equal to 3.6?10-2, 3.2?10-2, 3.2?10-3, 3.0?10-4 m3(GWh)-1, respectively. For liquid radioactive wastes of the low-level waste and intermediate level waste categories - 1.3?10-3 m3(GWh)-1, 2.4?10-2 m3(GWh)-1, respectively. The highest mean and median values of waste-specific volume for all radioactive waste categories are typical for nuclear power plants with LWGR (RBMK) reactor installations. The forecast based on the plans to increase electricity production by Russian nuclear power plants indicates a likely increase in the volume of radioactive waste generation by 0.7-7.4 % (depending on the waste category) in the period from 2022 to 2027. The waste-specific volume use makes it possible to rank the existing practices of nuclear power plant operation by the volume of radioactive waste generation to justify the criteria for compliance with the International Project on Innovative Nuclear Reactors sustainability methodology.

A point cloud semantic segmentation method for nuclear power reactors based on RandLA-Net Model

The detection of foreign objects in nuclear power plant reactor is a key task in the operation and maintenance of nuclear power plants. Loose and falling foreign objects such as bolts can lead to fuel component damage and unplanned shutdown, posing serious hazards. Therefore, we propose a point cloud semantic segmentation method for foreign objects in nuclear power plant reactor based on the RandLA-Net model. Considering the correlation between point cloud collection error and curvature, the data augmentation method is improved to reduce the risk of model overfitting. By treating the boundary points of different classes as the hard examples, the hard example mining is designed to improve model generalization performance. Adding an improved test time augmentation method during model inference, the more reliable segmentation results are performed by multiple prediction on points. The experimental results indicate that the proposed method can achieve high-accuracy reactor point cloud semantic segmentation with mIoU of 0.992 and mAcc of 0.997.

Результати діяльності Інституту проблем безпеки атомних електростанцій НАН України у 2022 р.

The most important results of the scientific and scientific-organizational activities of the Institute for Safety Problems of Nuclear Power Plants of the National Academy of Sciences of Ukraine (ISP NPP, NAS of Ukraine) in 2022 are presented. It is shown that even under the extremely difficult conditions in which the entire country is due to the invasion of Russian troops into the territory of Ukraine, the employees of the Institute made great efforts to implement planned tasks to ensure nuclear and radiation safety of the destroyed fourth power unit of the Chornobyl nuclear power plant, handling of nuclear hazardous materials, as well as increasing the reliability and safety of nuclear power plants operation. The results of these studies were implemented in the fields of production, electric power industry and during the educational process, as well as highlighted in a number of publications and scientific events. Thus, despite the objective difficulties and guided by the development strategy, the ISP NPP plans to preserve the scientific and technical potential under the conditions of power outages, lack of heating and water supply in some places, disruption of the functioning of public transport, telecommunications and data transmission facilities, etc., as well as to become the leading organization of Ukraine for scientific and technical support of activities for the peaceful use of nuclear energy

Codes and methods improvements for safety assessment and LTO: varied approaches

Nuclear safety has always been at the heart of the concerns of nuclear power plant operators and developers, as well as of various nuclear research organizations and regulatory authorities. Over the last decades, all these nuclear actors have developed and integrated a large number of calculation codes and other tools into their safety work. From the system approach to the local understanding of a phenomenon on a given component, from neutronics to operation optimization for long-term operation, these methods and codes have been constantly evolving since their appearance, in order to be able to integrate new plant designs and components, to improve the results of modeling physical phenomena or quantify and thus reduce the uncertainties on these results. Currently, several H2020 Euratom projects are working on the improvement of these codes and methods. This article will focus on three of these projects: CAMIVVER (Codes And Methods Improvements for VVER comprehensive safety assessment), APAL (Advanced PTS Analysis for LTO), and sCO2-4-NPP (innovative SCO2-based heat removal technology for an increased level of safety of Nuclear Power Plants) in order to illustrate our thinking on the improvement of calculation frameworks. First, we will present the work and the approach adopted with regard to the different calculation codes and methods used in each of these three projects. We will then conclude with an overall analysis of these three approaches, highlighting the difficulties and successes of these three projects, and identifying areas of work for the general improvement of the calculation codes.

Role of HMS Research Division for resumption of nuclear power plant operations (2)

Role of HMS Research Division for resumption of nuclear power plant operations (2)

Role of HMS Research Division for resumption of nuclear power plant operations (1)

Role of HMS Research Division for resumption of nuclear power plant operations (1)

가상경계법과 중첩격자법을 활용한 스윙 체크 밸브의 동수력학적 특성 비교

Nuclear Power Plant operators regularly check the performance of pumps and valves to verify the safety functions, and to monitor the degree of vulnerability over time through In-Service Test(IST). The swing check valve is one of the representative IST-related valve type. This valve functions to flow the fluid in only one direction, and automatically closes when the backflow occurs. In this study, the swing check valve performance test is conducted, and the result is compared with the computational fluid dynamics analysis using the immersed boundary method(ANSYS CFX R19) and overset mesh method(ANSYS Fluent R19). Overall, the inlet pressure depending on the disc angle predicted by the Fluent(overset mesh method) showed less error than the measured data compared to the CFX(immersed boundary method).The difference in the flow pattern passing through the gap between the valve entrance and top of the valve disc predicted by both methods was estimated to be the cause of the error in the simulation result compared to the measurement.

Construction of the Software and Technical Complex of Control Basic Parameters of Reactor Installation

The main problem associated with the operation of nuclear power plants is the problem of correct and timely diagnosis of failure or violation. The mistakes of technologists can lead to severe damage to nuclear power plants, or simply to a reduction in the utilization rate of installed capacity. The personnel make the main mistakes in the conditions of time shortage and being in a stressful situation during the development of an accident, when assessing changes in emergency parameters is not always possible, which leads to incorrect diagnosis of initial events (IE). Any IE leads to the deviation of the monitored parameters from normal values (values that are inherent to normal operation). The operator-technologist needs as soon as possible to determine the parameter (or parameters) for which the change occurs and, by performing a certain sequence of actions, bring their values to the norm. For information support of the operator-technologist is the information computing system (ICS). In the ICS, it is possible to control all parameters affecting the safe operation of the equipment, for each of which there are certain values, the deviation from which may lead to an accident. The paper considers the issues of the need to separate the measured parameters of NPP into separate groups that uniquely characterize the state of the critical security features. In particular, the necessity of consideration as the most important mass parameter of the primary coolant is shown. The issues of level measurement problems in the pressure compensator are discussed as the most important from the point of view of determining the mass of the primary coolant. Methods are proposed for determining the operability of sensors, the method of calculating a reliable level in the volume compensator. Estimates of the computational efficiency of the proposed methods are given.

Simulation of Dispersion Modeling of 137Cs for the Possible Leakage of Malaysia’s Nuclear Power Plant Operation

The world’s energy needs increase in line with population growth. One alternative to overcome this problem is the construction of a nuclear power plant, a source of energy that is cheap, clean, and safe. Malaysia has a plan to construct nuclear power plants by 2025, which is located close to Indonesian waters. This study aimed to determine the distribution model of 137 Cs radionuclide released by the nuclear power plant in the event of a leak in east coast of Peninsular Malaysia and its impact on the presence of 137 Cs in Indonesian waters. A quantitative method was used in this study with a scenario 2D modeling using hydrodynamics module and transport module in MIKE software. The results showed that the highest concentration of 137 Cs would be found in the area around the nuclear power plant with a value of 10 11 PBq/m 3 , then it would decrease through diffusion and advection processes. On the 15 th day, the spread of 137 Cs would reach Indonesian waters with a distance of up to 76 km and would expand on the 30 th day with a distance of up to 130 km from the released source. The movement of 137 Cs follows the dominant current pattern due to its nature. The presence of 137 Cs in Indonesian waters after the 15 th and 30 th days would reach a value of 1 Bq/m 3 due to advection and diffusion processes.

Design and evaluation of ecological interface for Feedwater Deaerating Tank and Gas Stripper System based on cognitive work analysis

Abstract The investigation of nuclear power plants (NPPs) accidents in the past shows that most of the accidents mainly occur in unexpected events. In this study, in order to verify whether Ecological Interface Design (EID) improves the situational awareness of operators in NPPs, this paper first analyzes the system by using the first three stages of cognitive work analysis, and then applies EID to the operating interface of NPPs to develop an ecological interface. In order to make the test results more complete, an improved interface has also been developed. A process expert and six operators were invited to participate in our experiments to measure situational awareness. The results show that the situational awareness of ecological interfaces in unexpected events is significantly higher than that of traditional and advanced interfaces. The significance of this study is that EID, as a practical technology, can be widely used in operator control rooms to improve the ability of operators to solve unexpected events.

Study on radiation degradation of nuclear power cable materials

During the operation of nuclear power plants, it is necessary to monitor and evaluate the aging of cable materials. In this paper, we evaluate the irradiated use status of two types of cable insulation materials used in nuclear power plants-cross-linked polyethylene (XLPE) and ethylene propylene diene methylene (EPDM). Firstly, two kinds of cable materials are subjected to accelerated radiation aging with different cumulative doses, and the macro-mechanical properties and microstructure changes of the cable materials after different doses are studied. Analyze and test its hardness value, tensile strength, elongation retention at the break, scanning electron microscope, and oxidation induction temperature. The results show that after γ-ray irradiation, the cable hardness and the retention rate of elongation at break show a downward trend. Under the highest cumulative dose of 500kGy, the retention rate of elongation at break is greater than 50% of the failure index. The tensile strength decreases slightly, the microscopic morphology of the tensile section has holes, and the oxidation induction temperature decreases.

Interaction with the Public as a Condition for the Development of Nuclear Energy

The subject of the study is the practice of interaction of nuclear energy specialists with the public, whose representatives have different opinions on the need for further operation of nuclear power plants, the construction of new ones in modern conditions. On the one hand, the creators of nuclear power plants prove that modern nuclear reactors make it possible to minimize the threat of emergency situations. On the other hand, in the public opinion of different countries, the idea of the danger posed by these industrial facilities is steadily preserved. The purpose of the work is to disclose practical actions taken by the international atomic energy organization IAEA, Rosatom to ensure dialogue between specialists in this area and interested social groups. The object of study is publications that have appeared in recent years in foreign and domestic literature on this issue. It has been shown that there is a search for such interaction of atomic physicists with the public in the media, the Internet, which will overcome existing biases about the state and prospects of nuclear energy. The absence of an open discussion of current problems of NPP development as a way to solve not only problems related to the economic development of countries, but also the protection of nature from the harmful effects of enterprises using gas, coal, oil for energy production, is one of the main reasons for the public's wary attitude towards nuclear power plants. Data on new technologies for creating objective ideas about the safety of modern nuclear energy in different public groups used in Russia and supported by specialists from other countries are presented. Conclusions were drawn about the need to create a system for the formation of knowledge about the state of nuclear power plants among the population, modern means of preventing emergency situations. These issues should be considered in special educational programs for different groups of the population, in the media with the involvement of qualified specialists.

The Influence of the Radiation Background of City-Forming Settlements with NPPs on Public Health and the Environment

The radioactive decay of elements as a result of a nuclear reaction is a powerful source of energy used in the production of electricity and heat in cities close to NPPs. The problem of using this kind of energy is the danger of radiation exposure. The production of nuclear energy has many advantages, including the profitability of the final product and its low cost; on the other hand, the half-life products of radionuclides in the composition of gas-aerosol emissions from ventilation pipes settle in the environment on the territory of city-forming nuclear power plants. The duality of the problems of the impact of radiation background on the urban areas near NPPs has become the purpose of this study. It is necessary to investigate the negative effect of radioactive waste emissions during the normal operation of nuclear power plants. For this purpose, the method of a project experiment was used, during which, using laboratory monitoring of external radiation safety and an automated radiation monitoring system, indicators of exposure dose capacities were collected from points in the 30-kilometre zone around the NPP. As a result of the monitoring of radiation samples from soil, atmospheric air and precipitation, and reservoirs, it was revealed that the natural radiation background is insignificant; the probability of harm from radiation exposure is small and insufficient for the development of radiation sickness. However, potentially unsafe sources of radiation exposure have been identified, such as natural radiation – the consumption of contaminated food, solar and cosmic radiation from radioactive elements present in the bowels of the earth; radionuclides, whose emissions uncontrollably occur into the atmosphere; radioactive waste, the disposal and storage technology of which is economically costly. Therefore, it is justified to conduct regular design experiments to check the operability of automated radiation monitoring systems. The materials of the study are of practical value for chemists, environmentalists, and ecotechnologists working at NPPs that monitor safety for human health and environmental protection in the field of atomic energy use

Strategy to coordinate actions through a plant parameter prediction model during startup operation of a nuclear power plant

The development of automation technology to reduce human error by minimizing human intervention is accelerating with artificial intelligence and big data processing technology, even in the nuclear field. Among nuclear power plant operation modes, the startup and shutdown operations are still performed manually and thus have the potential for human error. As part of the development of an autonomous operation system for startup operation, this paper proposes an action coordinating strategy to obtain the optimal actions. The lower level of the system consists of operating blocks that are created by analyzing the operation tasks to achieve local goals through soft actor-critic algorithms. However, when multiple agents try to perform conflicting actions, a method is needed to coordinate them, and for this, an action coordination strategy was developed in this work as the upper level of the system. Three quantification methods were compared and evaluated based on the future plant state predicted by plant parameter prediction models using long short-term memory networks. Results confirmed that the optimal action to satisfy the limiting conditions for operation can be selected by coordinating the action sets. It is expected that this methodology can be generalized through future research.

Fault diagnosis based on gated recurrent unit network with attention mechanism and transfer learning under few samples in nuclear power plants

Fault diagnosis (FD) of rotating machines is critical to the safety and economic operation of nuclear power plants (NPPs). Gated Recurrent Unit (GRU) is a gating mechanism in recurrent neural network and is a deep learning model that excels in processing sequential information and can be used to learn potential fault features in the condition monitoring data for FD. However, lack of sufficient fault samples (i.e., few samples) in NPPs prevents the GRU network from being adequately trained, resulting in poor performance. This study proposes a new GRU network combined with attention mechanism (AM) and transfer learning (TL), called GRU-AM-TL method. The attention layer is introduced to adaptively assign different weights to the extracted features for discrepant processing and enhancing focus on valuable information. The TL strategy tries to make full use of diagnosis knowledge learned from relevant fault datasets under different operating conditions, different machines or different fault severity for improving new diagnosis task under few samples. The specific FD target is to identify the fault nature (location, size or severity) by pattern recognition. Bearing, gearbox and NPP simulated fault datasets are used to validate the proposed method. Case study shows that the AM and TL strategy can help GRU network improve diagnosis accuracy under few sample scenarios. Moreover, the proposed GRU-AM-TL method can achieve the best performance in all test cases compared with GRU-based methods and other classical methods, such as convolutional neural network, support vector machine and random forest, showing good FD advantage in NPPs.

A fault diagnosis methodology for nuclear power plants based on Kernel principle component analysis and quadratic support vector machine

The safety of nuclear power plant operation can be improved efficiently by developing the fault diagnosis applications. However, adopting single technique may restrict the flexibility and accuracy of the fault diagnosis module. This paper proposes a new fault diagnosis methodology for nuclear power plants based on Kernel Principle Component Analysis (KPCA) and Quadratic Support Vector Machine (QSVM). The nonlinearity between variables is analyzed and the importance of variables are quantified by standard deviations. Sensor faults are distinguished from system faults using contribution charts. In pre-process stage of classification, five normalization modes are compared to achieve better performance of classifiers. For fault identification, samples are transformed to QSVM classifier and the diagnosis results are compared with other classifiers. To further evaluate the performance, three typical case conditions are tested. QSVM outperforms other classifiers on all types of system faults. The findings are beneficial for fault diagnosis of nuclear power plant.

Thermal analysis of baffle jetting in fuel rod assembly

Baffle jetting plays a significant role when it comes to safe operation of nuclear power plants. The baffle jetting phenomenon is the generation of horizontal flow impingement on fuel/control rods during the outward flow of the primary coolant into a nuclear reactor. To understand the flow and heat transfer characteristics under the baffle jetting conditions, large eddy simulations (LES) of flow around a 6×6 fuel rod assembly were conducted. Three Reynolds numbers based on jet width and inlet velocity were considered 5010, 10 000, and 20 000. A temperature difference of 5°C between the inlet fluid and the heated rods was considered to analyze the heat transfer characteristics within the assembly under baffle jetting. Various flow parameters were computed such as pressure coefficients along different rods, mean and fluctuating forces, Strouhal number, local and averaged Nusselt numbers. LES results were validated against experimental measurements and other numerical data. It was observed that the effect of the baffle jet was more significant on the first stream-wise row of rods with the stagnation points at the lower part of these rods. Furthermore, the averaged Nusselt number was found to be higher on rods in the stream-wise direction of the jet, rather than at other locations.

Development and application of unplanned automatic shutdown fault tree model of nuclear power plant

In order to improve the operation performance of nuclear power plants, this paper introduces a modeling method of unplanned automatic shutdown of nuclear power units based on Fault Tree Analysis, and takes the shutdown signal of steam generator water level low-low as an example, analyzes the development process and application scenarios of unplanned automatic shutdown fault tree in detail. The results show that this method solves the huge and complex problems in the fault tree model of unplanned automatic shutdown in nuclear power units, and can be used to comprehensively and systematically identify the components that affect unit power generation. At the same time, combined with quantitative data, it can monitor the risk of unit power generation, and achieve targeted and efficient improvement of equipment reliability management level and power generation performance level.

Loading pattern design and economic evaluation for 24-month cycle operation of OPR-1000 in Korea

Due to the tightened regulatory environment since the Fukushima accident, the capacity factor of Korean nuclear power plants has been declining since 2011. To overcome this circumstance, a shift from 18-month to 24-month cycle operation is being considered in Korea. Therefore, in this study, loading patterns(LPs) for 24-month cycle operation of the Korean standard nuclear power plant(OPR-1000) are suggested and economic evaluations are performed. A single-zone LP with 89 fresh fuels was evaluated to be optimal for 24-month operation of OPR-1000 in terms of economic gain. The 24-month operation of OPR-1000 with this LP gives a profit of 7.073 million dollars per year compared to 18-month operation.

"Human factor" in emergency situations development at Nuclear Power Plants in the conditions of war

Since the beginning of Ukraine's full-scale war with the russian federation, the personnel of two Ukrainian Nuclear Power Plants (NPP) (Chornobyl and Zaporizhzhya) have been held hostage by the russian occupiers and subjected to intimidation and abuse. An additional strong stress factor can significantly affect the decision-making of NPP control panel operators, increases the probability of erroneous actions in the event of emergency situations, and can even become their cause. The purpose of our study was to determine the possible influence of the "human factor" on the development of emergency situations, as well as additional parameters for monitoring the health and psychological state of NPP operators working as hostages. Fourteen expert psychologists with at least 10 years of experience in the field of extreme psychology were involved in the study. After the introductory seminar, they were offered a questionnaire to determine the range of professionally important qualities that have the greatest impact on the effectiveness of professional activity. The results of the expert evaluation became a hypothesis for the next stage of research on the possible influence of the temperament of operators on resistance to the stress of captivity. The technique of professiograms and psychograms separation, methods of scaling and balancing, methods of mathematical statistics and system analysis were used for the research. One hundred and twenty-four anonymous psychological examination cards and occupational profiles of NPP control panel operators who received a license for professional activity in Ukraine or improved their qualifications within the period of 2017‒2020 were analyzed. The predominant types of psychological reactions according to subjective-objective indicators in response to significant stressful situations were studied, and the types of temperaments were determined. The ability to perform professional functions at high and medium levels was recorded in 79 sanguine operators (63.2% of the total number of examined), in 16 choleric operators (12.8%), and was not recorded in melancholic operators. Also, high and medium levels of neuropsychological stability of operators were recorded in 74 sanguine operators (59.2% of the total number of examined), in 6 choleric operators (4.8%), and was not recorded in melancholic operators. To assess the psychological state of NPP control panel operators, it is proposed to use a retrospective analysis of interrelated parameters necessary for the performance of professional functions and indicators of neuropsychological stability. The study of additional parameters of the psychological state will allow to reduce the influence of the "human factor" on the risks of creating or untimely correction of emergency situations. Keywords: professionally important qualities, nuclear terrorism, hostages, performance of professional functions, neuropsychological stability, NPP control panel operators.