Operation Of Nuclear Power Plants Research Articles

Effects of video display terminal fatigue on situational awareness ability of operators and modeling study

In order to study the changing pattern of the posture perception ability of video display terminal operators in the main control room of energy power plants such as nuclear power plants in a state of fatigue, subjective and objective data of 19 energy system operators were collected through experiments. The effect of video display terminal fatigue on the operator's level of situational awareness was analyzed, and the subjective and objective data were selected to construct an XGboost model to predict the identified operator's situational awareness capability. The study results showed that the subjective and objective data showed significant differences, and it could be inferred that the subjects had developed video display terminal fatigue. The combination of data showed that fatigue affected the manipulator's ability to perceive and understand, decreasing the manipulator's situational awareness. The XGboost model, based on subjective and objective data, achieved a validation rate of 88.90%, indicating that the model can identify and predict the situational awareness of video display terminal manipulators. The study's results can be used to assess the situational awareness of video display terminal operators in nuclear power plants and provide a scientific basis for safety training in nuclear power plants and other energy power plants.

Efficient processing of tritiated water by using a two-stage Pd membrane reactor with Pt/TiO2 catalyst

Large amounts of tritiated water (HTO) will be produced during the operation of nuclear power plants and fusion devices, which is harmful to the environment and human due to its radioactivity and toxicity. So, the tritium concentration of tritiated water must be reduced to a very low value before discharge. Hydrogen-water isotope exchange reaction (H2 + HTO→H2O + HT) based on palladium membrane reactor has been proposed to process tritiated water. However, a comprehensive study about the influence of operation parameters on the membrane reactor performance is insufficient, which is not conducive to the design of reactor in practical application. Moreover, the commonly used Pt/Al2O3 or Ni/SiO2 catalysts are not active for tritiated water dissociation, so the catalytic activity of these catalysts is not high. In order to process tritiated water more effectively, a two-stage membrane reactor has been designed and established in this work, and Pt/TiO2 catalyst with rich oxygen vacancies is used to catalyze the hydrogen-water isotope exchange reaction for the first time. The membrane reactor performance shows an approximate linear relationship with a new combined parameter S0.5P1.5R/F2 (S is membrane area, F is water flow rate, P is vapor partial pressure, R is swamping ratio), which can be used predict the membrane performance. The isotope exchange reaction activity of Pt/TiO2 is better than that of Pt/Al2O3 due to its good ability for water dissociation and the hydrogen spillover effect. At last, a tritiated water processing experiment by using two-stage membrane reactor with Pt/TiO2 catalyst with rich oxygen vacancies has been carried out. The tritium decontamination factor reaches 40588, which is the highest experimental value so far. The results indicate that the two-stage Pd membrane reactor based on hydrogen-water isotope exchange reaction is an efficient technology for tritiated water processing.

Development of metal radioactive liquid reference material for proficiency test

This study developed liquid reference materials containing various metals, to be used for quality assurance of radiation measurements of the most common metallic wastes generated during the operation or decommissioning of nuclear power plants. The liquid reference materials were prepared by assuming the dissolution of stainless-steel using acid and melting of the major metals present in the stainless steel, namely Fe, Ni, Cr, and Mn, along with the standard sources (134Cs, 137Cs, 60Co, 90Sr). The theoretical massic activity of the standard sources added to the samples and the measured reference values of the gamma and beta emitters in the samples were compared, and they showed good agreement within a one-sigma confidence interval (k = 1). Using the developed reference materials, a proficiency test was conducted on three domestic labs, and the results were evaluated using Z-score. While the evaluation results showed good agreement between the reference values and the reported values for 137Cs and 60Co, all participating labs reported lower values than the reference value for 134Cs. For 90Sr, two out of the three labs reported significantly higher values than the reference value. Based on the results of this study, the developed metal radioactive liquid reference material is expected to be registered as certified reference material (CRM) in the future. They will be used as the CRM for measuring and ensuring the quality of radioactive metal waste.

Development of nuclear power in Belarus: a sociological analysis of the elasticity of public opinion

The article discusses the results of sociological monitoring of public opinion on the use of nuclear energy in Belarus. The main part presents an analysis of the data obtained from the results of a sociological study conducted by the Institute of Sociology of the National Academy of Sciences of Belarus in 2022 on the assignment “Conduct sociological monitoring of public opinion of the population of the Republic of Belarus in order to form a positive attitude towards nuclear energy” of event 8 “Information and analytical support for the development of nuclear Energy in the Republic of Belarus” of subprogram 3 “Scientific support for the efficient and safe operation of the Belarusian nuclear power plant and promising areas for the development of nuclear energy” of the State Program “Science-intensive technologies and equipment” for 2021– 2025. The time intervals within which important events had a direct or indirect impact on public opinion about nuclear energy are characterized. A sociological method of calculation has been developed that makes it possible to trace the vector of public opinion’s response to nuclear energy (increase or decrease in the level of loyalty) to various internal or external factors. An assessment of the elasticity of public opinion about nuclear power is carried out with the construction of a typology of this elasticity. Also, self-assessments of the respondents’ formation and stability of their position regarding the implementation of the project “Belarusian NPP” were revealed. The need for systematic information and explanatory work among the population on all the main aspects of the practical use of nuclear energy is shown.

A method for searching the best static program for nuclear power unit control in the event of perturbations of different nature

Considering the current state of Ukraine's energy sector in a dangerous and unstable environment, the operation of nuclear power plants is one of the most important sources of electricity supply for the state. The development of the theory of optimal control and the technical level of automated process control systems in the current state of affairs make it possible not to reduce the efficiency of controlling a nuclear power unit, not only by changing the parameters at any load, but also by changing the structure of automation equipment capable of implementing a certain static control program of power, which currently eliminates the influence of internal and external disturbances, without reducing safety indicators. The article considers the situation when the linear programming method is not applicable for solving the control problem. In this case, the decision at each stage does not depend on the decision at the previous one. This is where target programming comes in handy –this is one of the methods of multi-criteria optimization, in the theory of which decision-making problems are solved simultaneously according to several criteria. The purpose of the work is to ensure the safe and efficient operation of a nuclear power unit in an energy system that is not constant in operational states. Using a mathematical model of a nuclear power unit, experiments were carried out to simulate the switching of controlprograms. The simulation model of the automated power control system, based on the bumpless switching of static programs according to the technological methods of operating power equipment, made it possible to form a change in the current model of the control program, as well as eliminate the static control error and get the response of process dependent parameters to program switching. Also, based on the results of the research, an objective function was proposed, which includes three normalized criteria with different objectives. In particular, the problem of optimizing the switching of static power control programs was solved by minimizing the objective function, which combines such characteristics as the efficiency and safety of the operation of a nuclear power unit.

Plutonium in sediments of the Eastern Guangdong coast-its sources and their contribution

The 239+240Pu activities and 240Pu/239Pu atom ratios of surface sediments from the Eastern Guangdong coast (EGDC) were determined by sector field ICP-MS in order to examine the sources of plutonium (Pu) and quantify their contributions. The 239+240Pu activities in the EGDC ranged from 0.113 to 0.451 Bq kg−1, with an average of 0.225 ± 0.090 Bq kg−1 (n = 17). Consistently high 240Pu/239Pu atom ratios, ranging from 0.218 to 0.274 (average = 0.254 ± 0.014, n = 17), indicate a non-global fallout Pu source in the EGDC. The horizontal distribution of the 240Pu/239Pu atom ratios in the EGDC sediment suggests the non-global fallout Pu is sourced from close-in fallout from the Pacific Proving Grounds (PPG). Using a simple two end-member mixing model, we calculated the relative proportions of Pu from the PPG and global fallout in the EGDC to be 57 ± 9 % and 43 ± 9 %, respectively. Moreover, from the well-defined relationship between 239+240Pu activity and total organic carbon content in sediments and a two end-member mixing model using δ13C, we further calculated the Terr-global fallout (riverine input) and Mar-global fallout (direct atmospheric deposition) to be 11 ± 2 % and 32 ± 6 %, respectively. Finally, from the activity levels and atom ratios of Pu isotopes in the EGDC, we established a baseline for future use in environmental risk assessment related to nuclear power plant operations.

A methodology to designate radiation‐controlled areas in decommissioning nuclear power plants

AbstractKori Unit 1, which was permanently shut down in 2017, is expected to be the first decommissioned commercial nuclear power plant (NPP) in Korea. Operating NPPs designate radiation‐controlled areas (RCAs) to protect workers from radiological hazards and provide appropriate measures. Decommissioning RCAs (DRCAs) in NPPs being decommissioned should also be designated by considering the radiological characteristics of workplaces and exposure routes of decommissioning workers, such as external and internal exposure. However, the criteria for the DRCAs in decommissioning Kori Unit 1 are presently the same as those during normal operation, according to the public‐hearing material of the final decommissioning plan for Kori Unit 1. This study analyzed criteria for RCAs in all Korean NPPs to propose criteria for DRCAs in decommissioning NPPs. Analysis results show that RCAs are classified into four, five, six, and eight zones in Korean pressurized water reactors with respective external radiation dose rates. The RCAs in Korean pressurized heavy water reactors are classified into six zones with external dose rates and derived air concentrations of tritium. This study proposes three classifications of DRCAs to keep occupational exposure as low as reasonably achievable while considering potential exposure routes, that is, external exposure, airborne contamination, and surface contamination areas. First, the external exposure areas are classified into several zones according to the levels of external radiation dose rates. Second, the airborne contamination areas are designated to prevent internal exposure to workers from the inhalation of radioactive material in the air during cutting and demolition. Last, the surface contamination areas are designated to minimize the skin contamination of workers as radioactive dust in the air is deposited on the surface of facilities and equipment over time.

AI-Driven approach for enhancing nuclear reactor safety predictive anomaly detection and risk assessment

Nuclear power plays a vital role in meeting global energy demands, but ensuring the safety of nuclear reactors remains a paramount challenge. In recent years, the emergence of artificial intelligence (AI) technologies has opened new avenues to significantly enhance nuclear reactor safety through predictive anomaly detection and risk assessment. This research proposes an innovative AI-driven approach that integrates machine learning techniques and data analytics to monitor, detect, and assess potential anomalies in nuclear reactors. The research begins with a comprehensive literature review on nuclear reactor safety and the application of AI in various industrial domains, emphasizing predictive maintenance and anomaly detection. It highlights the need for an AI-driven approach to enhance nuclear reactor safety proactively. In conclusion, this research establishes the transformative potential of AI in enhancing nuclear reactor safety. The proposed AI-driven approach empowers operators with powerful tools to ensure the safe and efficient operation of nuclear power plants. As AI technologies continue to advance, the research opens doors for further exploration and development, paving the way for a more sustainable and secure future in nuclear energy production.

Shaking Table Test for Seismic Response of Nuclear Power Plant on Non-Rock Site

In order to compare and analyze the seismic response characteristics of a safety-related nuclear structure on a non-rock site in the condition of raft and pile group foundations under unidirectional and multidirectional seismic motion input, a large-scale shaking table test of the soil-nuclear structure system was carried out in this paper. In the test, the soil was uniform silted clay, and the shear wave velocity was 213 m/s. Considering the similarity of the superstructure natural frenquency, the actual nuclear power structure was simplified to a three-story frame shear wall structure model. The annular laminated shear model box was used to take the boundary effect of soil into consideration; the seismic motions = were input in only one horizontal direction or three directions at the same time for the shaking table test, and the results were analyzed. The results of the test show that the acceleration response of the safety-related nuclear plant is affected by the directions of input seismic motion and the forms of the foundation. When the seismic motion is input simultaneously in three directions, the acceleration responses of the horizontal motion and vertical rocking of the safety-related plant are larger than those of the single-direction input. The acceleration response of the horizontal motion and vertical rocking of the safety-related structure with the pile group foundation is smaller than that with the raft foundation. The values of most frequency bands in the horizontal acceleration Fourier amplitude spectrum at the top of the pile-foundation structure are smaller than that at the top of the raft-foundation structure, while the displacement is basically the same as that of the raft-foundation structure. This is related to the relation between the frequency component of input seismic motion and the natural frequency of the structure system. Therefore, it is more reasonable to use three-dimensional seismic input in the seismic response analysis of nuclear power plants. The seismic performance of nuclear power plants can be enhanced by using pile group foundations.

Removal of gaseous methyl iodide using hexamethylenetetramine and triethylenediamine impregnated activated carbon: A comparative study

Radioactive iodine may be released into off-gas streams during both, the normal operation and severe accident of nuclear power plant in both organic and inorganic forms. Methyl iodide formation results from the reaction between radioactive iodine and organic products (like paint and cable coatings) present within the containment. For the removal of methyl iodide (MeI) gas, activated carbon (AC) was impregnated with 2, 5, 8 and 10 wt% of hexamethylenetetramine (HMTA) and triethylenediamine (TEDA). Characterization of the raw and impregnated activated carbon (IAC) was done by XRD, SEM, Raman, BET and TGA. Removal efficiency of MeI was evaluated using breakthrough experiments by varying weight percent of TEDA and HMTA. Both TEDA and HMTA-rich AC exhibited significant MeI adsorption capacity. TEDA-IAC was more effective for the elimination of MeI which adsorbed maximum 473 mg/g at low temperatures, whereas HMTA-IAC with high porosity had a comparatively high adsorption capacity at high temperatures due to its stability as compared to TEDA-IAC and adsorbed maximum 245 mg/g MeI. When raw AC was compared to IACs, results demonstrated that adsorption capacity of MeI improved up to 64 % for TEDA and 54 % for HMTA impregnated ACs.Langmuir model was well fitted to adsorption equilibrium data, and second-order model explained adsorption kinetics. Thermodynamic parameters study confirmed that the reaction is exothermic and spontaneous in nature.

Study on the Effect of Structural Parameters of Volume Control Tank on Gas–Liquid Mass Transfer

The volume control tank (VCT) is an important facility in the primary circuit of nuclear power plants. During the normal operation of nuclear power plants, the mass transfer between the gas and liquid phases occurs in the VCT at all times. It is driven by submerged jets, which may cause potential risks to the operational safety of nuclear power plants. It is necessary to conduct an in-depth study to gain a deeper understanding of the gas–liquid mass transfer behavior in the VCT. In this paper, a new gas–liquid mass transfer model is developed that combines a surface divergence model with a CFD model to accurately simulate the mass transfer process of the gas phase into the liquid phase. The simulation data were verified by the experimental results. The deviation between the simulation results and experimental results is less than 6.55%. Based on this model, a simulation study was carried out for the effect of structural parameters of the VCT on gas–liquid mass transfer. The results show that the double-vortex structure above the jet inlet, the surface jet at the gas–liquid interface, and the vortex at the end of the jet are the three factors dominating the gas–liquid mass transfer in the VCT. The gas–liquid mass transfer can be influenced by the jet diameter since the jet diameter has a remarkable effect on the Kolmogorov scale and the macroscopic flow field structure. Moreover, both the Kolmogorov scale and the macroscopic flow field structure can be affected by the jet height. However, these two effects cancel each other out. Thus, the influence of the jet height on the gas–liquid mass transfer rate is negligible.

Impact of long-term operation of nuclear power plants on the marine ecosystem of Daya Bay

Based on the monitoring data of Daya Bay in 2011–2017, the impact of long-term operation of nuclear power plants (NPPs) on the marine ecosystem was accessed. 137Cs and 90Sr in seawater and sediment of Daya Bay decreased with time. The environmental half-lives of 137Cs and 90Sr in seawater, 137Cs in sediment were 7.1 a, 11.7 a and 13.9 a, respectively. The total dose rates of the marine organisms ranged from 230.5 to 853.9 nGy/h, lower than the ERICA screening benchmark (10 μGy/h). 210Po, 226Ra and 232Th were the main dose contributors. 137Cs and 90Sr contributed to ~0.01 %–~0.06 % of the total radiation. 137Cs contributed to <0.6 ‰ of the committed effective dose for humans. There were almost no radiation effects on the marine ecosystem of Daya Bay from NPPs before 2017. In the future, there will be no radiation risk for the long-term discharge of low-level radioactive waste to Daya Bay.

Review on performance of chromium-coated zirconium and its failure mechanisms

The conventional Zircaloy cladding may react with coolant in light water reactors and elicit severe accident at high temperature, which constraint the safe and efficient development of nuclear energy. To avoid the tragedy happened in Fukushima, the concept of Accident Tolerant Fuel (ATF) was developed around the globe to secure the steady operation for nuclear power plants. As a short-term solution, deposition of protective coatings upon the cladding tubes are proved to be effective. Among the coatings, Chromium is one of the most outstanding choices. This paper reviews the recent study results about the performance and failure mechanisms of Cr-coated Zr cladding, including mechanical, irradiation, high-temperature oxidation tests, etc. under normal and/or accident conditions. The experiments and tests collectively suggest that Cr coating possesses excellent comprehensive properties for integrity protection of claddings and provides a promising future of the commercial application in reactor cores. Finally, this review proposes ambiguities and questions needed to be analyzed and clarified in future works.

Study on irradiation embrittlement behavior of reactor pressure vessels by machine learning methods

A reliable irradiation embrittlement model of reactor pressure vessel (RPV) is critical to the safe operation and life extension of nuclear power plants (NPP). In this study, 474 datasets from NUREG/CR-6551 and 6 machine learning (ML) methods were adopted to accurately predict the irradiation embrittlement behavior (ΔRTNDT) of RPV with comprehensive input factors involving irradiation conditions and metal composition. The GBDT model has the best prediction performance. The calculated result by GBDT model is close to those of JEAC-4201 and ASTM E900-15. Cu content is the most sensitive factor for ΔRTNDT, followed by neutron fluence. This work demonstrates a successful application of ML in promoting NPP safety and RPV materials design.

IMPACT OF URBAN LAND ON THE RISKS OF KARST PROCESSES IN THE NPP LOCATION AREA (ON THE EXAMPLE OF RIVNE NPP)

The aim of the article is to assess the impact of urbanized areas on the risk of developing karst processes in the area of nuclear power plant location and on the safety of the plant (using the example of the Rivne nuclear power plant). Karst features in the area around the Rivne nuclear power plant were visualized using GIS methods. Systematization of karst hazards was carried out with regard to their impact on the structural integrity and safety of the long-term operation of the Rivne nuclear power plant. The impact of urbanized areas on the geological environment was assessed, and a correlation was established between urbanization factors and the activation of karst-suffusion processes. It is shown that urbanization can contribute to the emergence of karst manifestations and, as a result, to threaten to the safety of NNP. Approaches aimed at improving the assessment of karst hazards, monitoring of the main factors of their activation, and managing urbanized areas to increase the safety of nuclear power plants were proposed.

Monitoring of tritium in surface waters in PC, Nuclear facilities of Serbia

The isotope of hydrogen, tritium, is a radioactive isotope, in most cases it is found bonded to molecules that replace hydrogen. It can be found in nature as a product interactions of cosmic radiation with air or atmospheric molecules nitrogen, such tritium is natural. There is also anthropogenic tritium that contributes increased levels of natural tritium. Artificially produced tritium is produced in testing of nuclear weapons, in the operation of nuclear power plants and processing nuclear fuel. This paper will describe the methods of tritium detection liquid scintillation detector Quantulus 1220 by direct method in duration of 300 minutes at the Department of Nuclear Physics. Surface water samples with tritium was taken from the location of PC Nuclear facilities of Serbia from the Mlaka stream. The monitoring recorded an increase in tritium content at two locations, which indicates failures of nuclear waste storage.

Modern approaches to strength design substantiation for critical elements of WWER NPP reactor internals

This study presents the theoretical and applied results on the development and application of refined models and methods for solving actual problems of mechanics related to the substantiation of strength and forecasting the service life of elements of the primary circuit equipment of WWER nuclear power plants (NPPs). The scientific and applied developments take into account current trends in global practice and contain new conceptual approaches to solving nonlinear boundary value problems in the mechanics of deformed structures. Refined mathematical models have been proposed and theoretically substantiated to describe non-isothermal inelastic deformation processes, taking into account the deformation history of thermal and power loading, radiation effects of hardening, swelling and creep of irradiated metal, and accumulated damage of brittle-ductile fracture. The obtained scientific results are the basis for the methodology of refined design strength analysis and residual life assessment of critical elements of the equipment of the first circuit of WWER reactor units to solve urgent problems of ensuring the conditions for safe operation of Ukrainian NPPs and justifying the terms of their service life extension

Deep reinforcement learning for a multi-objective operation in a nuclear power plant

Nuclear power plant (NPP) operations with multiple objectives and devices are still performed manually by operators despite the potential for human error. These operations could be automated to reduce the burden on operators; however, classical approaches may not be suitable for these multi-objective tasks. An alternative approach is deep reinforcement learning (DRL), which has been successful in automating various complex tasks and has been applied in automation of certain operations in NPPs. But despite the recent progress, previous studies using DRL for NPP operations have limitations to handle complex multi-objective operations with multiple devices efficiently. This study proposes a novel DRL-based approach that addresses these limitations by employing a continuous action space and straightforward binary rewards supported by the adoption of a soft actor-critic and hindsight experience replay. The feasibility of the proposed approach was evaluated for controlling the pressure and volume of the reactor coolant while heating the coolant during NPP startup. The results show that the proposed approach can train the agent with a proper strategy for effectively achieving multiple objectives through the control of multiple devices. Moreover, hands-on testing results demonstrate that the trained agent is capable of handling untrained objectives, such as cooldown, with substantial success.

Far-Field Influences Shadow the Effects of a Nuclear Power Plant’s Discharges in a Semi-Enclosed Bay

The sustainable development of society depends on the reliable supply of electricity while keeping impacts on the environment to a minimum. A 951 MWe nuclear power plant in the semi-enclosed Nanwan Bay at the southern tip of Taiwan began operating in May 1984. Part of the bay is in Kenting National Park, which is known for its coral reefs and abundant marine life; thus, thermal pollution from the cooling water discharge is a great concern. Fortunately, the bay opens south to face the Luzon Strait, where the world’s strongest internal tides are generated. Because the bay is deep enough, internal waves bring up cold deep water and reduce the surface temperature by as much as 10 °C for a few hours every day. These internal waves and topographically generated upwelling also bring nutrients to the euphotic layer from the depths, but the upwelled waters quickly leave the bay along with the cooling water. As a result, a thermal plume with a temperature of 1 °C or higher than the ambient temperature only covers 1 km. By way of comparison, El Niño—Southern Oscillation- or Pacific Decadal Oscillation-related interannual variations in temperature are as high as 5 °C. The rapid turnover of the upwelled waters also helps to prevent heat released by the power plant from accumulating and diminishes the thermal stress, thus sustaining corals and other marine life forms. Typhoons, even hundreds of kilometers away, could also induce the upwelling of cold subsurface water. Consecutive typhoons have been observed to reduce the water surface temperature by up to 10 °C for two weeks or longer. Furthermore, the currents are such that the thermal plume flows out of the bay most of the time. All of these factors make the surface waters in the bay about 0.5 °C cooler than the waters outside of the bay, despite the operation of a nearby nuclear power plant.

Resistance of Gable Structure of Nuclear Island to Progressive Collapse in Conventional Island Shield Building of Nuclear Power Plants

The gable wall of the conventional island of a nuclear power plant carries various pipeline loads connecting the nuclear island and the conventional island. If the gable wall collapses and is damaged due to the progressive collapse of the main plant structure of the conventional island, it will directly threaten the safety of the nuclear island. Therefore, it is of great significance to systematically study the resistance of the gable structure of the nuclear island to progressive collapse for the safe operation of nuclear power plants. Based on the SAP2000 finite element analysis platform, this paper established a model of the reinforced concrete frame structure of the first span of the shield building on the conventional island of a nuclear power plant, including the gable. According to the alternate path method, the node displacement and bearing capacity responses were used to determine the critical components in the gable, and single column failures of the top four in importance were selected as different analysis conditions. Nonlinear static and dynamic methods were used to analyze the displacement, internal force change, hinge sequence of the gable structure on the side of the nuclear island, and the ability of the gable to resist progressive collapse. The analysis results showed that the gable structure of the nuclear island had good resistance to progressive collapse under four single column failure conditions, whether by nonlinear static or dynamic analysis, and the overall vertical displacement obtained by the nonlinear static analysis was larger than that obtained by the dynamic analysis.