Operation Of Nuclear Power Plants Research Articles

Comparative experiment on the efficiency of water cooling in photovoltaic modules in the climatic conditions of Southern Russia

The problems of ensuring the safety of operation of nuclear power plants are always paid increased attention. In addition to the self-contained diesel generator sets used to maintain the operation of safety systems in case of loss of external power supply, it is also advisable to consider the use of more environmentally friendly self-contained photovoltaic units at this stage. The work is aimed at a comparative experimental study of the efficiency of water cooling in real natural climatic conditions of Southern Russia. In this experiment, cooled and uncooled photovoltaic modules are simultaneously exposed to a complex of variable weather factors: solar radiation, cloudiness, wind, pressure, temperature and humidity of the environment. Both modules have loads connected via MPPT controllers. The effect of water cooling on the energy efficiency of photovoltaic modules assembled from silicon heterojunction technology (HJT) solar cells was studied. The solar panels were made from 130 micron thick HJT cells interconnected using SmartWire contact technology. It reduces power loss due to possible defects such as cracks. The conditions for ensuring the highest degree of similarity between the parameters of the cooled and uncooled modules have been met. A comparative experimental study was conducted in Astrakhan State University using a long-term monitoring system for the characteristics of photovoltaic modules. This is a test photovoltaic system (TPS), built on the basis of the Paragraph PL2 electronic recorder. A significant increase in module output when working with cooling was established. At insolation of 987.5 W/m2, the power generated by the cooled module was 93.0297 W, while the power of the module without cooling was 79.306 W. The difference comprised 13.7237 watts. Power increased by 17%. In the experiment, the average efficiency value when the module was cooled was 0.15977. When uncooled, it was 0.13764. The efficiency intensified by 2.21%. This increase is significant. The results obtained confirm the fairly high efficiency of water cooling in photovoltaic modules in real natural operating conditions for regions with high ambient temperatures, Southern Russia, in particular

NUWARD SMR safety approach and licensing objectives for international deployment

Drawing on the deep experience and understanding of the principles of nuclear safety, as well as many years of nuclear power plant design and operation, the EDF led NUWARD SMR Project is developing a design for a Small Modular Reactor (SMR) of 340 MWe composed of two 170 MWe independent units, that will supplement the offering of high-output nuclear reactors, especially in response to specific needs such as replacement of fossil-fuelled power plants. NUWARD SMR is a mix of proven and innovative design features that will make it more commercially competitive, while integrating safety features that comply with the highest international standards. Following the principles of redundancy and diversity and rigorous application of Defence in Depth (DID), with an international view on nuclear safety licensing, the Project also incorporates new safety approaches into its design development.The NUWARD SMR Project has been in development for a number of years, it entered conceptual design formally in mid-2019 and entered Basic Design in 2023. The objective of the concept design phase was to confirm the project technological choices and to define the first design configuration of the NUWARD SMR product, to document it, in order to launch pre-licensing with the French Safety Authority (ASN) and to define its estimated cost and its subsequent development and construction schedules. As a delivery milestone the Safety Options file (called the Dossier d’Options de Sûreté (DOS)) has been submitted to ASN in July 2023 for their opinion.An integral part of the NUWARD SMR Project, is not only to deliver a design suitable for France and to satisfy French regulation, but to develop a product suitable and indeed desirable, for the international market, with a first focus in Europe. In order to achieve its objectives and realise its market potential, the NUWARD SMR Project needs to define and realise its safety approach within an international environment and that is the key subject of this paper. The following paper:• Summarises the foundation principles and technological background which underpin the design;•Contextualises the key design features with regard to the international safety regulatory framework with particular emphasis on innovative passive safety aspects;•Illustrates the Project activities in preparation for first licensing in France, and also a wider international view via the ASN led Joint Early Review of the NUWARD SMR design, including Finnish and Czech Republic regulators, recently joined by the Swedish, Polish and Dutch regulators;•Articulates the collaborative approach to design development from involvement with the Project partners (the Commissariat à l’énergie atomique et aux énergies alternatives (CEA), Naval Group, TechnicAtome, Framatome and Tractebel) to the establishment of the International NUWARD Advisory Board (INAB), to gain greater international insight and advice;•Concludes with the focus on next steps into detailed design development, standardisation of the design and its simplification to enhance its commercial competitiveness in a context of further harmonisation of the nuclear safety and licensing requirements and aspirations.

Public opinion on nuclear power plants in Japan, the United Kingdom, and the United States of America: A prescription for peculiar Japan

In attempts to solve climate change and energy security issues, many countries have made plans to invest in nuclear energy. Public opinion on nuclear energy is an important factor in building support for the construction and operation of new nuclear power plants (NPPs). In this study, public opinion surveys on existing NPP use and the new construction of NPPs were conducted simultaneously using the same method in Japan, the United Kingdom, and the United States of America. Japanese respondents were neutral on existing and new NPPs, citing “no strong reason”. In all three countries, the term “new construction” made the respondents anxious about NPP safety. This study also examined whether Japanese respondents’ attitudes change when the reasons for negative opinions toward NPPs are solved. By using the phrase “NPPs that no longer require evacuation,” respondent anxiety was resolved, and an increase in the respondents who agreed with the new construction of NPPs was observed. For Japanese respondents who believed that the problem of radioactive waste had not yet been resolved, the selection of a disposal site was not perceived as a solution. Based on these findings, this research provides valuable insights that can help advance energy policy in Japan.

Gamma Ray Spectrum by Software Methods for Radioactive Waste

The requirements of NTD (Neglected Tropical Diseases) and technological regulations for the operation of NPP (Nuclear Power Plant) power units (NP-001-97 (OPB-88/97), NP-082-07) define the requirements for monitoring the specific activity of iodine-131 (the amount of iodine) in the NPP primary circuit coolants. The advantages of laboratory control include accuracy of measurement and the radionuclide composition of the primary coolant, measured using high-precision laboratory equipment. Instrumental spectra were obtained for the detection units BDKG-205m with various options for the placement of waste in a container, their composition, mass of waste, average density, and various activity levels of waste. The basic idea behind gamma-ray spectroscopy is to detect and analyze the energy of incident gamma rays. Gamma rays of varying energy and intensity are emitted from radioactive sources. The gamma-ray energy spectrum is produced when gamma rays are detected and examined using a spectroscopy instrument. The initial stage in gamma-ray spectroscopy is to detect gamma rays using a suitable detector. The detector captures and measures the energy of incoming gamma rays. Scintillation detectors, semiconductor detectors, and gas-filled detectors are among the detectors used in gamma-ray spectroscopy. The incoming gamma-ray energy is converted into electrical signals that can be processed and studied by these detectors. The spectroscopic system measures and records the energy of gamma rays when they are detected. The derived energy spectrum depicts the intensity distribution of gamma rays as a function of energy. The spectrum is a visual representation of the different energy levels found in gamma-ray emission.

Prediction of the binding energy of self interstitial atoms in alpha iron by a graph neural network

The estimation of neutron irradiation embrittlement is crucial for the long-term operation of nuclear power plants. The jump of self-interstitial atoms is an essential process for understanding embrittlement, and their binding energy is critical to estimating the activation energy for jumping. This study presents a fast estimation method for the binding energy of self-interstitial atoms in iron using a graph neural network. The network assigns a self-interstitial atom to a node and the relationship between self-interstitial atoms to an edge. The graph neural network was trained using a large dataset of binding energies between self-interstitial atoms (∼0.5 % density) calculated using an embedded atom method interatomic potential. The network was also trained using smaller datasets of binding energies between self-interstitial atoms (∼2.0 % density) calculated using first principles calculations. The graph neural network accurately predicts binding energy with a mean absolute error of 0.05–0.06 eV and coefficient of determination (R2) of 0.9 without overfitting, using the large interatomic potential dataset. When trained on smaller first principles datasets, the network predicted binding energies with a mean absolute error of 0.15–0.16 eV and coefficient of determination (R2) of 0.6 with some degree of overfitting. The developed graph neural network provides a fast and accurate estimation method for the binding energy of self-interstitial atoms in iron.

Applying Visible Light Communication Co-location in Nuclear Power Plant: Architecture and Key Technologies

A nuclear power plant (NPP) is an important site to convert nuclear energy into electric energy. Wireless communication technologies can effectively promote more efficient and convenient constructions and operations of an NPP. However, the traditional wireless communication technologies have several possible risks such as radio-frequency electric sparks and electromagnetic interference, which may endanger the operation of NPPs. Recently, visible light communications (VLCs) and visible light positioning (VLP) have become two promising technologies for the nuclear power industry as they are electromagnetic-free and also highly secure. In this article we first present a multilayer architecture for an NPP, which includes a Macrocell layer, a Picocell layer, and an Attocell layer. The former two layers work in the radio-frequency spectrum to provide seamless coverage for outdoor and indoor unrestricted areas. The Attocell layer works in the visible spectrum to provide coverage for restricted areas, in order to prevent electromagnetic interference and ensure safety. A visible light communication co-location (VLCL) system is proposed in the Attocell layer to provide high-speed transmission and positioning services. Several key technologies are discussed, including light source layout, communication and positioning techniques, and multiplexing scheme. Finally, technical challenges and possible solutions are presented. This article demonstrates that VLCL system has potential great advantages in supporting the nuclear power industry.

Adsorption/Desorption Performances of Simulated Radioactive Nuclide Cs+ on the Zeolite-Rich Geopolymer from the Hydrothermal Synthesis of Fly Ash

The operation of nuclear power plants generates a large amount of low- and intermediate-level radioactive waste liquid. Zeolite-rich geopolymers, which are synthesized under hydrothermal conditions from industrial waste fly ash, can effectively immobilize radioactive nuclides. In this study, the synthesis law of zeolite-rich geopolymers and the adsorption/desorption performances of radioactive nuclide Cs+ were researched using XRD, SEM and ICP. The results show that the increase in curing temperatures and NaOH concentrations leads to the transformation of Y-type zeolite to chabazite and cancrinite at low NaNO3 concentrations. However, at high NaNO3 concentrations, NaOH above 2 M has no obvious effect on the phase transformation of the main zeolite of chabazite and cancrinite. In the adsorption and desorption experiment of Cs+ on the chabazite/garronite-rich geopolymer, it was found that the adsorption of Cs+ in the low initial concentration range is more suitable for the Freundlich equation, while the Langmuir equation fits in the adsorption process at the high initial concentration range. Moreover, the desorption kinetics of Cs+ are in good agreement with the pseudo-second-order rate equation. Thus, the adsorption of Cs+ on chabazite/garronite-rich geopolymers is controlled by both physical and chemical reactions, while desorption is a chemical process.

Machine learning-aided damage identification of mock-up spent nuclear fuel assemblies in a sealed dry storage canister

Spent nuclear fuel (SNF) assemblies (FAs) contain high-level radioactive waste from operation of nuclear power plants (NPPs). Their safe storage in dry casks is critical for nuclear waste management. However, interim storage or transportation of a canister in a cask, the FAs may be damaged due to human errors, extreme events, or long-term degradation. Therefore, non-destructive evaluation (NDE) methods are needed to monitor their structural integrity over time. In this paper, a novel machine learning (ML)-aided method is proposed to identify different levels of FA damage using measurements taken on the exterior surface of a 2/3-scale experimental canister mock-up. The frequency response functions (FRFs) of the fully loaded canister basket (FLCB) system and the canister with interior damage were computed from recorded input excitation and acceleration response measurements. Machine learning classifiers, including Random Forest (RF), Artificial Neural Networks (ANNs), and Gaussian Naive Bayes (GNB), were trained and tested using features extracted from the FRF difference between an intact FLCB and a damaged canister. The results indicated that the RF model produces the best performance with a testing accuracy of 0.916 and Macro-F1 score of 0.920. Notably, the RF model accurately predicted the damage levels regardless of sensor (i.e., accelerometer) locations. The GNB, however, provided a compromised performance due to its inability to handle correlated features and non-ideal Gaussian distribution of the data. The ANN model exhibited an intermediate performance between the RF and GNB models. Besides, ANN and GNB models had a higher rate of false negatives than the RF models. The accuracy of the model needs to be considered in a real-life implementation because false positives are likely to result in added costs in terms of further inspection while false negatives could potentially result in further degradation and failure.

Study of adsorption and immobilization of Cs+, Sr2+, Co2+, Pb2+, La3+ ions on Na-Faujasite zeolite transformed in solid state matrices

Zeolites have become promising adsorbents for wastewater treatment due to their enhanced adsorption capacity, stability of crystalline structure, high porosity and surface area. One of the primary goals of our study was to assess the effectiveness of employing NaY zeolite as a sorbent and potential solid matrix for immobilizing radionuclides. In this study NaY faujasite zeolite was obtained by hydrothermal synthesis and characterized by X-Ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) methods. The prepared zeolite had NaY faujasite crystalline structure, characterized by developed surface area (370 m2/g) with micro-mesoporous structure, and spherical-like morphology with particles of 1–4 μm in diameter. The isotherms adsorption modeling on Cs+, Sr2+, Co2+, Pb2+ and La3+ ions was performed. The isotherm well described by Langmuir equation with maximum adsorption capacity of q(Cs+) = 1,9 mmol/g, q(Sr2+) = 3,75 mmol/g, q(Co2+) = 1,82 mmol/g, q(Pb2+) = 2,54 mmol/g, q(La3+) = 3,83 mmol/g. Thermal behavior of metal-saturated adsorbents by differential thermal analysis (DTA) and thermal gravimetric (TG) techniques was studied. Each metal examined in this paper is responsible for the stable formation of radionuclides (137Cs, 90Sr, 60Co, La - generally, the group of active lanthanides was modelled, Pb - uranium fission residues) that are generated during the operation of nuclear power plants. To optimize sintering regimes, it has been proposed to achieve sorption saturation of stable ions such as Cs, Sr, Co, La, and Pb and transfer them into solid matrices. It was shown that the consolidation temperature for the obtained samples varies in the range of 935–1040 °C.

ON RADON ACTIVITY OF TECTONIC FAULTS IN THE AREA OF SITING THE SINOP NPP IN THE REPUBLIC OF TŰRKIYE

Problem statement. The paper provides an additional expanded justification for applying an innovative methodology in the area of the future Sinop NPP, planned to be deployed in the Republic of Tűrkiye, to identify the activity rate of tectonic faults in soil foundation based on comprehensive radon measurements using the PSACEA universal estimation scale. The purpose of the article. Current radon activity assessment of existing tectonic faults in Earth’s crust based on archival measurements of soil radon carried out earlier in Sinop Province. Conclusions and results. Current analysis of radon measurement results obtained previously by the track method made it possible to further assess the radon activity rate of tectonic faults existing in the area of the future nuclear power plant. The proposed methodology to assess radon activity of tectonic faults in Earth’s crust involves increasing safety during the construction and operation of the future nuclear power plant. The regulation on using this methodology as part of the subsurface monitoring at the Sinop NPP can be enshrined in job descriptions. This methodology can also be used as part of the seismic monitoring of other sites at the nuclear power plant, especially those located in high seismic risk zones.

Investigation of environmental radioactivity levels and human health risk around San'ao Nuclear Power Plant (China) before operation

Baseline study on environmental radioactivity levels and public health conditions are crucial before the operation of nuclear facilities. Our goal is to establish a baseline database before the operation of San'ao Nuclear Power Plant (SNPP). To achieve this, water and food samples collection was carried out around the SNPP from 2021 to 2022 for laboratory analysis to determine the radioactivity levels. Thereafter, annual effective dose (AED) to local residents were evaluated by the analysis results and cancer incidence rates were analyzed by health data of local residents. Our results showed that the gross α and β activity concentrations in water varied within < 0.016–0.023 Bq/L and 0.031–0.080 Bq/L, respectively. The 90Sr and 137Cs activity concentrations range from 3.1 to 9.7 mBq/L and 0.11–0.42 mBqg/L in water, and range from 0.037 to 0.95 Bq/kg and 0.015–0.38 Bq/kg in food. All obtained results of gross α and β, 90Sr and 137Cs were below the thresholds of World Health Organization (WHO) and Chinese national standard. The AED induced by ingestion of food or drinking water were below the thresholds of WHO or Chinese national standard, indicating that radiation exposure was at a safe level. The incidence rate of all cancer sites combined among the residents around the SNPP was slightly higher than other regions, but still remained at the same scale. However, the incidence rate of thyroid cancer stood out to be significantly higher than the national average value in China, presumably due to excessive iodine intake in the study region.

SiRENE: A new generation of engineering simulator for real-time simulators at EDF

For Safety Assisted Engineering works, real-time simulators have emerged as a mandatory tool among all the key actors involved in the nuclear industry (utilities, designers and safety authorities). EDF, Electricité de France, as the leading worldwide nuclear power plant operator, has a crucial need for efficient and updated simulation tools for training, operating and safety analysis support.This paper will present the work performed at EDF/DT to develop a new generation of engineering simulator to fulfil these tasks. The project is called SiRENE, which is the acronym of Re-hosted Engineering Simulator in French. The project has been economically challenging. Therefore, to benefit from existing tools and experience, the SiRENE project combines:- A part of the process issued from the operating fleet training full-scope simulator.- An improvement of the simulator prediction reliability with the integration of High-Fidelity models, used in Safety Analysis. These High-Fidelity models address Nuclear Steam Supply System code, with CATHARE thermal-hydraulics system code and neutronics, with COCCINELLE code.- And taking advantage of the last generation and improvements of instructor station.The intensive and challenging uses of the new SiRENE engineering simulator are also discussed. The SiRENE simulator has to address different topics such as verification and validation of operating procedures, identification of safety paths, tests of I&C developments or modifications, tests on hydraulics system components (pump, valve etc.), support studies for Probabilistic Safety Analysis (PSA). etc. It also emerges that SiRENE simulator is a valuable tool for self-training of the newcomers in EDF nuclear engineering centers.As a modifiable tool and thanks to a skillful team managing the SiRENE project, specific and adapted modifications can be taken into account very quickly, in order to provide the best answers for our users' specific issues.Finally, the SiRENE simulator, and the associated configurations, has been distributed among the different engineering centers at EDF (DT in Lyon, DIPDE in Marseille and CNEPE in Tours). This distribution highlights a strong synergy and complementarity of the different engineering institutes at EDF, working together for a safer and a more profitable operating fleet.

The effect of the future of nuclear energy on the decarbonization pathways and continuous supply of electricity in the European Union

Nuclear power plants play an extremely important role in the European Union's electricity supply. Nuclear power is the largest carbon neutral source of electricity and the most important baseload electricity producer in Europe. The existing 167 units represent a capacity of 148 000 MW, which in 2022 accounted for 22 % of the electricity generated in the EU-27. In most countries, there are plans to keep nuclear power plants in operation and then extend their lifetime. In most of the European countries that already have nuclear power the construction of new units is planned, as well as in Poland, which is a nuclear newcomer.Meanwhile, Germany has phased out nuclear power in 2023 and this move is also being considered in other countries. In this article, we address the question of what the impact would be in the EU member states if nuclear power plants were to be phased out and replaced by solar, wind and gas-fired capacities.To do this, energy strategies for EU countries with nuclear power were analysed, hourly resolution electricity supply models were constructed for 15 countries and the main electricity supply characteristics for year 2030 and 2040 were assessed for three different power plant portfolios in each country under study. For the different scenarios, specific results are presented on the primary energy mix, CO2 emissions, natural gas demand and high time resolution characteristics of electricity supply.

Time-dependent fragility analysis of a nuclear containment structure under internal pressure and chloride-induced corrosion

The prestressed concrete containment structure, serving as the ultimate barrier against nuclear fuel leakage, holds paramount importance in ensuring the uninterrupted operation of nuclear power plants. Particularly in the aftermath of the Fukushima nuclear disaster, the influence of material aging and degradation of containment structures has been emphasized. Consequently, a probabilistic performance assessment of containment structures under chloride-induced corrosion condition is of significant relevance. This study presents a method for time-dependent fragility analysis of nuclear containment structures subjected to internal pressure, considering the effect of chloride-induced corrosion of steel reinforcement. A highly efficient and accurate finite element model with multi-layered shell element is formulated for damage and failure analysis. Furthermore, a corrosion degradation model of reinforced concrete, aligned with the attributes of multi-layered shell elements, is derived to reduce the reduce parameter samples generated by Latin Hypercube sampling technique. Material uncertainties and time-dependent effects are jointly integrated into the finite element analysis process, culminating in the establishment of fragility curves for the containment structure under various service lifetimes. The results indicate that within first 40 years of service, the load-bearing capacity of the containment structure has slightly decreased, while the probabilities of functional and structural failures in the containment structure will significantly increase after 60 years of service.

Modeling and operation strategy of nuclear power plant with electric heat storage in the ancillary service market

In the power ancillary service market, power sources can participate in peak shaving and obtain profits. However, nuclear power plants (NPPs) cannot contribute sufficient peak-shaving capability to the power system and obtain peak-shaving profits due to their limited flexibility as the base load. To tackle this challenge, an electrothermal coupled model for NPPs is proposed in this paper, which combines the characteristics and constraints of nuclear power units and electric heat storage (EHS). The coupling model can enhance the flexible adjustment capability of NPPs by increasing their self-consumption. Meanwhile, the operation strategy of NPPs considering the electrothermal coupling model is developed to enhance the NPP operation profits. Moreover, a cost calculation method for NPPs is developed, which can calculate the peak-shaving compensation and cost-sharing of NPPs. The effectiveness of the proposed method is verified by numerous simulations using the model of the Hongyanhe Nuclear Power Plant in Liaoning, China. Compared with the three traditional methods, the profit of the EHS is increased by 3%, the peak-shaving compensation is enhanced by 4.4%. Meanwhile, the cost-sharing is reduced by 40%, and the total profits of the proposed method are improved by 18.9%.

Development and validation of machine learning-based transient identification models in a liquid-fueled molten salt reactor system

Safety is the most important aspect of nuclear power plants. Rapid identification and effective prevention of accidents in nuclear reactor system is a significant method to enhance the safety of the current fleet of reactors. Machine learning (ML) has been introduced in engineering applications of nuclear power plants and is becoming increasingly practical and powerful in recent years. Consequently, ML can also benefit rapid transient identification in nuclear power plants. The feasibility of ML-based identification models to identify transient events in liquid-fueled Molten Salt Reactor (MSR) is presented. Four transient identification models based on recurrent neural network (RNN), support vector machine (SVM), decision tree (DT) and k-nearest neighbor (KNN) were developed and validated. RELAP5-TMSR code was used to generate datasets including eleven operation conditions, and these datasets were used to train, optimize, and validate the identification models. Four metrics including accuracy, precision, recall and F1 score were utilized to evaluate all four identification models. Moreover, the robustness of the models under noise was tested. The four ML-based models were successfully applied to transient identification of liquid-fueled MSRs. The KNN-based model has the best performance and achieves high test scores under noise. In the future, these proposed intelligent identification models will have good potential and prospects in supporting the operation of nuclear power plants.

Management of the period of operation of hydro engineering facilities of hydro power plants

Introduction. In recent years, the issue of the need to make decisions regarding hydraulic structures of hydroelectric power plants (hereinafter referred to as GTS HPP) that are in operation, the estimated service life of which has ended, has become relevant. &#x0D; &#x0D; Aim. To focus attention on the lack of norms and rules for establishing the designated period of operation of hydraulic structures, on the importance of ensuring regulatory regulation by creating rules for determining the design service life and designated period of operation, criteria for the possibility of their extension, and also to outline an optimal approach to managing the period of operation of hydraulic structures of hydroelectric power plants during their operation.&#x0D; &#x0D; Materials and method. Federal laws and other regulatory legal acts are considered for the presence in them of provisions and requirements for the purpose of service life and period of operation, criteria for the possibility of extending the designated period of operation of GTS facilities for various purposes, including GTS hydroelectric power plants. According to SP 58.13330.2019 "Hydraulic structures. The main provisions. Updated version of SNiP 33-01-2003" the assigned estimated service life of the first and second class GTS is 100 years, the third and fourth class GTS is 50 years. This norm was established in 2013. The terms and definitions of service life, designated period of operation.&#x0D; &#x0D; Results. An analytical review is provided on the state of regulatory support in the Russian Federation in order to determine the rules for designate period of operation of hydraulic structures, information on the practice of decision-making abroad on managing the designated period of operation of hydraulic structures, their conservation, reconstruction or liquidation. The experience of managing the designated period of operation of nuclear power plants is considered. Proposals have been formulated for managing the established period of operation of hydraulic structures of hydroelectric power stations when the service life of hydraulic structures of hydroelectric power stations is exceeded.&#x0D; &#x0D; Conclusions. Proposals have been formulated to ensure regulatory regulation for the purpose of determining the period of operation, criteria for the possibility of extending the period of operation, and managing the designated period of operation of hydraulic structures of hydroelectric power stations during their operation.

Analysis of Crack Propagation Behaviors in RPV Dissimilar Metal Welded Joints Affected by Residual Stress.

In severe service environments, the presence of high local residual stress, significant organizational gradient, and nonlinear changes in material properties often leads to stress corrosion cracking (SCC) in dissimilar metal welded (DMW) joints. To accurately predict the crack growth rate, researching the initiation and propagation behavior of SCC cracks in DMW joints under residual stress (RS) is one of the most important methods to ensure the safe operation of nuclear power plants. Using the extended finite element method (XFEM), the crack propagation behaviors in DMW joints under different RS states are predicted and compared. The effects of RS, crack location, and initial crack length on crack propagation behavior are investigated. The crack in a DMW joint without RS deflects to the material of low yield strength. High residual stress urges the crack growing direction to deflect toward the material of high yield strength. Young's modulus has little impact on the crack deflection paths. The distance between the specimen symmetric line and the boundary line has little effect on the crack initiation and propagation within the RS field. A long initial crack is more likely to initiate and propagate than a short crack. To a long crack and the crack that is far from the interface of two materials, the impact of residual stress on the crack propagation path is significant when it is located in a material with high yield strength, while when the initial crack is located in the material with low yield strength, RS has a great influence on the deflection of a short crack growth direction on the condition that the crack is adjacent to the interface.

Когда кристаллизованный интеллект может быть профессионально «нежелательным» личностным качеством операторов

Purpose: To discuss the case of oppositely directed influences of the indicators of crystallized and fluid intelligence in the decisive rule designed to predict the professional success of the nuclear power plants (NPPs) operators. Material and methods: This paper analyzes the results of psychodiagnostic examinations of operators of main control rooms (MCR) of NPPs that functioned under normal conditions. All individuals were administered the J. Raven’s “Progressive matrices”, the Russian language adaptation of the Minnesota Multiphasic Personality Inventory (MMPI) and the Sixteen Personality Factor Questionnaire (16PF, form A). A cross-expert review using the ranking method revealed two groups of operators with relatively higher and lower levels of professional success. The method of canonical correlation analysis has been used to obtain the best linear discriminator for predicting the professional success of MCR operators based on indicators of psychodiagnostic tests. Results: Based on the results of the expert assessment, two groups of operators with the highest and lowest professional success were identified. Decisive rule were obtained that make it possible to predict the professional success of operators based on a system of signs (values of the psychodiagnostic tests scales multiplied by coefficients) after the data processing using canonical correlation analysis. Unexpected result was that the high values of 16PF factor «B» turned out to be «undesirable» for the prediction of professional success, that is, these values increased the probability of assigning the operator to the group of the lowest successful specialists. Conclusion: Factor «B» of 16PF was considered as a tool for assessing predominantly crystallized intelligence, and the Raven’s test – for the fluid one. At the same time, there are no methods that allow measuring these indicators in their purest form. Taking this fact into account, the author believes that the true role of factor B in the decisive rule did not reflect the undesirability of advanced crystallized intelligence among MCR operators. It is most likely that its opposition to the «desirable» indicator (the number of correctly solved tasks of the Raven’s test) made it possible to single out the role of fluid intelligence (or some of its lower-level aspects) as a professionally important quality for the particular operator activity.

Rocking stiffness of electrical cabinets with tubular base in nuclear power plants

Safe operation of nuclear power plants during an earthquake requires continued operation of safety related electrical equipment as intended. Such equipment are mounted in electrical cabinets and are seismically qualified by using an in-cabinet response spectra (ICRS). Generation of ICRS requires a good understanding of the cabinet’s dynamic characteristics. Past studies have shown that the rotational stiffness associated with the cabinet base and the mounting arrangement plays a primary role in the dynamic behavior of the cabinet. This rotational stiffness is needed to evaluate and characterize the global rocking mode of cabinet vibration. Existing studies have developed formulations to calculate the rocking stiffness for a few mounting arrangements that are typically found in United States and some other western countries. However, existing formulations could not be applied to cabinets in South Korean nuclear plants due to the differences in cabinet mounting type. This study is focused on consideration of tubular mounting arrangement that is typically found in South Korean plants. First, closed-form formulations are developed using fundamental principles of mechanics for two separate cases of this mounting arrangement. Then, detailed nonlinear finite element (FE) analyses are conducted for different mounting arrangements corresponding to different properties and dimensions of the tubular base. The FE models are used to calibrate the proposed closed-form formulations for various different configurations and structural or geometrical properties of tubular members. The proposed formulations provide a simple and accurate estimation of cabinet rocking stiffness which otherwise is difficult to evaluate without a shake table test or a detailed finite element analysis.