Nuclear Plant Research Articles

State-of-art review of beyond design basis evaluation approach of a generic nuclear power plant in the UK

Abstract The Fukushima accident prompted rapid development in the appreciation and codification of BDB methodology into regulatory guidance and this is still continuing, especially at IAEA, which has recently and is due to publish several new standards documents directly relevant to BDB analysis. The objective of this paper is to provide a state-of-art review on how BDB evaluations are undertaken in the UK nuclear industry. Then, using the work undertaken for the Generic Design Assessment (GDA) in the UK for UK HPR1000, this paper proposed a more systematic approach for “cliff-edge” evaluation based on a generic nuclear power plant design currently being developed in the UK.

Testing the thermal performance of water cooling towers

Abstract The essential service water system (ESWS) in nuclear power plants circulates the water that cools fan coolers, cooling water heat exchangers, and condensers and other components before dissipating the heat into the environment. Because this includes cooling the systems that remove decay heat from both the primary system and the spent fuel rod cooling ponds, the ESWS is a safety-critical system. In locations without a large body of water in which to dissipate the heat, water is recirculated via a cooling tower. Cooling towers fall into two main categories: Natural draft and Mechanical draft. Since, the mechanical draft cooling towers are much more widely used; the focus is on them in this work to measure its performance. Therefore; the present work addresses the thermal acceptance test for mechanical draft water cooling tower in order to determine its thermal capability in accordance with the cooling technology institute (CTI) code recommendations. Both the Characteristic Curve and the Performance Curve Methods are used. A detailed description of the test procedure according to the CTI ATC-105 test code is presented, and the test code is applied on the Egypt second research reactor (ETRR-2) cooling tower as a case study. All the instruments used in the reactor plant are calibrated prior the test and the measured data is collected at regular intervals according to the code recommendations. The test result shows a tower capability of about 105 % and so the tower is thermally accepted.

Research on the radioactive safety of industrial steam supplied by PWR nuclear power plant

The heating source of the nuclear power steam supply installation is PWR secondary steam, but the secondary steam is potentially radioactive, and the radioactive material may migrate to the industrial steam, which goes through the leakage of the heat exchanger. Compared with the conventional industrial steam, the steam supplied by the nuclear power has potential radioactivity. Nuclear power is first introduced to produce the industrial steam, in order to analyze the specific activity and radiation effects of the industrial steam on the staffs at the user side, an analytical model of industrial steam radioactivity is developed based on the technological process of industrial steam under operating conditions, and then the exposure pathways of the staff at the user side from the industrial steam is analyzed. The specific activity of the industrial steam and the exposure dose of the staff is evaluated. According to the evaluation results, it can be seen that the dose to staff caused by the industrial steam is far smaller than the radiation impact on the public caused by the nuclear power plant, and can meet the requirements of relevant regulations and standards. Therefore from the radiation safety point of view, the industrial steam supplied by the nuclear power steam supply installation is safe and acceptable for industrial use.

Pure metals for creation the nuclear structural materials

The paper presents the main results of research on the development of structural materials for equipment elements of existing and prospective nuclear power plants. The further development of nuclear energy largely depends on the development of advanced structural materials for new generation reactors and the improvement of materials for operating nuclear power plants. The high requirements for structural materials regarding the content of impurity elements can be met only when high-purity metals are used as initial components and new technologies for their production are used. The prospects of using new methods and approaches for evaluating and improving the physico-mechanical and physico-chemical properties (microhardness, corrosion resistance, radiation resistance, etc.) of structural materials for nuclear technologies were considered.

Measurement of neutron spectra in spent fuel storage

The neutron spectrum was measured at two locations in the spent fuel storage facility of the Temelín nuclear power plant. The measurement had two primary objectives: to map the neutron -γ field by quantifying the ambient dose equivalent H∗(10) and to identify methods that could improve the quality of the adjusted neutron spectrum using a Bonner Sphere Spectrometer (BSS). Three spectrometers were used: a BSS and two proton recoil spectrometers. Hydrogen-filled proportional counters and an EJ309 scintillator were used to construct the a priori spectrum for BSS adjustment. The details of this process and its results are discussed. The a posteriori spectrum was used to calculate the ambient dose equivalent H∗(10). The resulting spectrum is highly thermalised, but the predominant contribution to H∗(10) was in the 100 keV-1.3 MeV range. The use of hydrogen-proportional counters in combination with the BSS is recommended.

Multi-Scale Risk-Informed Comprehensive Assessment Methodology for Lithium-Ion Battery Energy Storage System

Lithium-ion batteries (LIB) are prone to thermal runaway, which can potentially result in serious incidents. These challenges are more prominent in large-scale lithium-ion battery energy storage system (Li-BESS) infrastructures. The conventional risk assessment method has a limited perspective, resulting in inadequately comprehensive evaluation outcomes, which impedes the provision of dependable technical support for the scientific appraisal of intricate large-scale Li-BESS systems. This study presents a novel Li-BESS-oriented multi-scale risk-informed comprehensive assessment framework, realizing the seamless transmission of assessment information across various scales. The findings from a previous smaller-scale analysis serve as inputs for a larger scale. The evaluation process of this method is more scientifically rigorous and yields more comprehensive results compared to assessment technologies just relying on a single perspective. By utilizing the proposed comprehensive assessment methodology, this study utilized the emergency power supply of nuclear power plants (NPPs) as an application scenario, demonstrating the complete implementation process of the framework and conducting a comprehensive assessment of Li-BESS feasibility as an emergency power source for NPPs. Our findings propose a novel paradigm for the comprehensive assessment of Li-BESS, which is expected to serve as a scientific foundation for decision-making and technical guidance in practical applications.

Cybersecurity in Prognostics and Health Management

PHM continues to show its value by improving operational efficiencies, increasing safety, reducing downtime, and decreasing cost of operations. PHM technologies are therefore not only being deployed as retrofit solutions but are being integrated into new systems as standard practice. Deployment covers areas such as medical equipment, nuclear power plants, aeronautics applications, oil and gas, mining, and many others. As the impact of PHM increases, it is imperative to also consider the potential vulnerabilities that are being exposed. Hackers have famously used Supervisory Control and Data Acquisition (SCADA) and Programmable Logic Controller (PLC) systems to sabotage industrial facilities. As such, it is important to understand the exposure to malfeasance to ensure that PHM does not end up being the enabling mechanism for unauthorized access to the system it is meant to keep in running order. It is also important to understand the measures that need to be taken to avoid or respond to an attack. These range from extensive penetration testing to conducting extensive counter-social engineering training, setting up a PHM-specific CERT plan and team in place. This paper discusses various threats that are emerging and that may have to be considered when designing a PHM solution. Additionally, the NIST cybersecurity framework is discussed in the context of PHM. Finally, this paper looks at the diagnostic capabilities of PHM systems to detect cyber security attacks and to contain these threats.

Presentación del Volumen 5 Número 3 - Octubre 2024 - enero 2025

Latest issue of Volume 5 of the journal, which highlights aspects of national security, reaffirming that in Peru there are multiple dimensions of the national reality in which risk scenarios develop. The national peculiarity lies in the increase of problems –in the internal sphere– that affect national security and development, which leads to maintaining the diversity of studies and research that highlight the interdependence of security and development, but does not neglect the analysis of the advance of war, as the case of the use of drones, mercenaries and nuclear plants in the conflict between the Russian Federation and Ukraine. In the anniversary month of CAEN-EPG, its important role in benefiting proposals to optimize our national security, overcoming the adversaries of the Homeland, is highlighted.

Rotor fault diagnosis of centrifugal pumps in nuclear power plants based on CWGAN-GP-CNN for imbalanced dataset

As a crucial device in nuclear power plants, centrifugal pumps undertake the critical role of cooling water circulation. Centrifugal pump rotor misalignment and unbalanced faults cause pump performance degradation, vibration increase, and equipment damage, thus seriously affecting the safety and reliability of nuclear power plants. In the process of centrifugal pump rotor fault, the difficulty in obtaining data samples and the limited amount of data can lead to an imbalance problem between the quantity of normal state and fault state samples in the dataset. In order to solve the problem, this paper proposed a CWGAN-GP model for generating rotor fault data based on CGAN and WGAN-GP models, and combined it with a two-stream CNN model to realize the rotor fault diagnosis with an imbalanced dataset. The quality and performance of the data generated by the proposed method were evaluated and validated in terms of visualization analysis, statistical indicators, and comparison with different data generation models. The results show that the CWGAN-GP model can generate high-quality data. Meanwhile, compared with other models on datasets with different degrees of imbalance, the two-stream CNN model is more effective in fault diagnosis on the expanded dataset by the CWGAN-GP model, and the improvement of fault diagnosis accuracy ranges from 1.40% to 13.33%.

Tri-training algorithm based nuclear power systems semi-supervised fault diagnosis under multiple restricted data conditions

An improved tri-training semi-supervised classification method was proposed as a solution to the restricted data conditions of supervised classification models relying on labeled data, semi-supervised models not considering imbalanced proportion of faults data and the presence of faults data with similar feature or varying severity in existing data-driven nuclear power system fault diagnosis studies. Based on the structure of three identical sub-classifiers in the original tri-training algorithm, data update paths have been added, the updated data selection has been strengthened, and the initial information and permissions of sub-models have been differentiated. The novel method only requires the dataset to meet the Smoothness Assumption, and through multiple strict data update paths, it improves the utilization of unlabeled training data while reducing Pseudo-labeling process errors. The difference in permissions and initial information between sub-classifiers is utilized to improve the training rigor for fault types with smaller sample sizes, in order to alleviate the problem of imbalanced data. Based on a marine nuclear power system secondary circuit model and a widely recognized nuclear power plant dataset, multiple nuclear power system common restricted fault diagnosis datasets faced in ships and power plants were obtained to verify the novel method's advantages and generalization. The conclusion is that under the same conditions, compared with the original tri-training method and other semi-supervised learning methods, the Accuracy, AUC, Precision Rate and Recall Rate of the novel method have improved by about 21 %, 10 %, 20 %, and 21 %, respectively, and can reduce about 25 % of misjudgments between similar feature faults.

Radiological Assessment of Loss of Coolant Accident from Saeul Nuclear Power Plant

Radiological Assessment of Loss of Coolant Accident from Saeul Nuclear Power Plant

Evolution mechanism of internal flow in the hump region and hump optimization of axial-flow reactor coolant pump

The Nuclear Reactor Coolant Pump (RCP) serves as a pivotal equipment in nuclear power plants, and its operational reliability is directly linked to the overall safety of the plant. When operating in the hump region, axial-flow reactor coolant pumps inevitably experience significant vibration and noise. Therefore, it is necessary to study the internal flow characteristics in the hump region to achieve effective control and increase the hump margin, keeping it away from the normal operating region. This study conducted analyses of pressure pulsation characteristics under various flow rates through experimentation. Additionally, numerical simulations were employed to scrutinize the internal flow of the pump under corresponding flow rates. Research has found that the disturbance of intermediate frequency signals is the main reason for the increase in pressure fluctuations in the hump region, rooted in the annular flow at the impeller inlet and vortex phenomena in the flow channel. Subsequently, the performance of the hump region was improved by optimizing the design of the vane inlet attack angle. The conclusions drawn from this study provide insights and a foundation for the optimal design of reactor coolant pumps.

Advancing Nuclear Research and Education in Slovenia and EU: From Operating the TRIGA Reactor to Building a New Generation Facility

AbstractThe TRIGA Mark II research reactor at the Jožef Stefan Institute in Slovenia achieved first criticality in 1966. Since then, the reactor has been playing an important role in developing nuclear technology. The reactor has been mainly used for research, education of university students, training of operators of the Krško nuclear power plant (start of operation in 1983) and other nuclear specialists, isotope production and beam applications. The reactor is experiencing a high level of activity today, engaging in a diverse range of experiments and studies across reactor physics, environmental research, radiation hardness testing as well training and education. The future of nuclear technology in Slovenia is focused on new NPPs, while the research community is looking forward to a possible new nuclear reactor. The basic initiatives are at a very preliminary stage: the primary choice is dual-core pool-type reactor, with a zero-power core and a separate MW-size core, cooled and moderated with light water. Such a dual-core configuration is designed to meet the varied requirements of the European Union member states. Another option would be hosting one or more micro-reactors with electrical and/or heating power producing capability that could offer stronger support toward demonstration of prototype small modular reactors in prototype future electrical grids.

Enhanced elastic stress solutions for junctions in various pipe bends under internal pressure and combined loading ([formula omitted] pipe bend, U-bend, double-bend pipe)

Piping systems in nuclear power plants normally operate under high pressure and high temperature. To efficiently manage space within these systems, pipe bends are extensively used. However, the welded joints connecting these pipes may be susceptible to flaws due to weld residual stress, transient loads, and operating environments. When flaws are present in such areas, analytical evaluation of flaws is to be carried out based on fracture mechanics parameters such as stress intensity factor. To calculate the stress intensity factor, distributions of the elastic stress are required. Therefore, this paper presents closed-form approximations of elastic stress in the junction between a pipe bend and a straight pipe under internal pressure. Review of the existing elastic stress solutions for estimating the stresses in pipe bends was carried out analyzing their limitations. Based on those limitations elastic stress solutions for thick to thin wall pipe bends were proposed and were validated against finite element (FE) analysis for thick-wall to thin-wall pipe bends under internal pressure and combined loading (i.e. internal pressure, in-plane bending, out-of-plane bending inflicted simultaneously). 90° pipe bend, U-bend and double-bend pipe configurations were considered and showed good agreement with the FE results exhibiting less than 5.8 % discrepancies. The accuracy of the elastic stress solutions for pipe bends provided in the existing code are summarized and validated in the appendix as well.

Analysis of the application of natural circulation of cooling media in shipboard reactor installations

In projects of floating facilities with a nuclear power plant, great importance is attached to the formation of a set of properties of the internal self-protection of the reactor, i. e. the development of properties that ensure its safety based on natural feedbacks, processes and characteristics. To do this, the RU project is based on physical patterns and technical solutions that prevent or minimize possible consequences from emergency situations. In particular, the natural circulation of the coolant in case of loss of power supply by the circulation pumps of the first round allows cooling the core after its transfer to a subcritical state. However, in order for a natural circulation to occur sufficient to ensure nuclear and radiation safety, certain conditions must be met in a particular case. The paper notes that the most important property of reactor installations of nuclear vessels is their ability to ensure natural circulation of the coolant in emergency situations, as well as when operating at capacity. This makes it possible to reduce the dependence of reactor plant safety on the technical condition of power supplies. Currently, natural circulation of auxiliary cooling media in passive safety systems is also widely used in reactor installations. These include emergency reactor cooling systems using an emergency cooling system, including using intermediate heat exchangers; reducing emergency pressure in the protective shell in case of an accident with a large coolant leak; cooling the reactor vessel in an out-of-design accident with the formation of corium. The paper proposes a method for preliminary analysis of the reactor plant’s ability to ensure natural circulation of the coolant, which allows us to compare various design solutions that contribute to an increase in coolant consumption during natural circulation. It is shown that for the operation of the reactor plant in stand-down mode and at energy power levels with natural circulation of the coolant, it is advisable to switch to boiling reactors. Passive safety systems using natural circulation have received special development on new nuclear vessels of projects 20870, 22220, 10510. Further development of safety systems using natural circulation to move cooling media is predicted.

A comprehensive review of radiation shielding concrete: Properties, design, evaluation, and applications

AbstractThis review paper provides a comprehensive analysis of radiation shielding concrete, covering its properties, design, evaluation, and applications. It begins with an introduction, stating the objective and scope. The paper explores radiation shielding basics, including ionizing radiation, shielding principles, and materials used for shielding. Concrete's properties relevant to shielding, radiation attenuation mechanisms, and factors affecting its efficiency are discussed. Different types of radiation shielding concrete are examined, along with their applications. The design and formulation of shielding concrete, including mix proportions, optimization techniques, and quality control, are presented. Evaluation methods and standards are discussed. Lastly, challenges, future directions, and emerging technologies are outlined. This review paper serves as a valuable resource for professionals involved in radiation shielding. The review on radiation shielding concrete highlighted its effectiveness in attenuating ionizing radiation, emphasizing material composition, density, and thickness as key design factors. Evaluation methods, such as gamma spectroscopy and Monte Carlo simulations, are discussed, demonstrating its versatile applications in nuclear facilities, healthcare, and space exploration.

Multiple relocation cases in disaster-related deaths after the Fukushima nuclear accident

IntroductionRelocation after a disaster often has negative health effects on vulnerable people, particularly older adults. However, little is known about the number of repeated evacuations and relocations after disasters among those experienced disaster-related deaths. This case series aimed to summarize the secondary problems and mortality risks in patients involved in relocation after disasters.MethodsWe analyzed and summarized the data on 520 disaster-related deaths in Minamisoma City, a municipality near the Fukushima Daiichi Nuclear Power Plant, focusing on the number of relocations. Herein, we describe the cases of three individuals over 80 years old, who died after eight or more relocations, which were certified as disaster-related deaths.ResultsWe discuss following three cases, which are (1) a female patient in her 90s who had a stroke and was completely disabled, (2) a female patient in her 80s whose cancer was detected later due to her failing to see her family doctor, and (3) a male patient in his 80s whose regular postoperative treatment was disrupted following cancer recurrence.DiscussionOur findings indicate that evacuation led to the worsening of chronic diseases and eventually to post-disaster death. Prolonged wide-area evacuation and repeated relocation likely interrupted the continuum of care and led to the failure of adequate care provision. To reduce the loss of human life, it is necessary to review the number of wide-area evacuations and relocations over the medium to long term after large-scale disasters, including nuclear disasters, which may occur in the future. Simultaneously, it is important to establish a medical system at the evacuation site so that disaster victims can continue to receive medical care even after evacuation or relocation.

Clinicopathological Findings of 220 Pediatric, Adolescent, and Young Adult Patients with Thyroid Cancer in Fukushima Medical University Hospital.

Background: Thyroid ultrasound examinations (TUEs), conducted as part of the Fukushima Health Management Survey (FHMS), were initiated to monitor the health status of residents after the Fukushima Daiichi Nuclear Power Plant accident owing to concerns regarding the increased incidence of thyroid cancer among children, as observed after the Chernobyl Nuclear Power Plant accident. This study reported the clinicopathological characteristics of patients with thyroid cancer diagnosed through the FHMS and treated at the Fukushima Medical University Hospital. Methods: Data regarding the clinicopathological characteristics of patients with thyroid cancer were collected and evaluated in this descriptive study. Results: Among the 263 patients diagnosed with thyroid cancer as of September 2021, 220 patients with cytologically diagnosed thyroid cancer were treated as referrals from the FHMS. The median (interquartile range) age at the time of diagnosis was 18.6 (16.2-20.3) years. The median maximum tumor diameter was 13.0 (10.4-18.0) mm. To reduce surgical invasiveness, 199 patients (90.1%) underwent unilateral lobectomy. Pathological findings were suggestive of papillary thyroid carcinomas (PTC) in 216 (98.2%) patients; among them, 205 patients had PTC of the classical type. In addition, 216 (98.2%) patients had stage I disease. Cancer cell extension in the sternothyroid muscle or perithyroidal soft tissues and microscopic lymphovascular invasion were observed in 112 (50.9%) and 123 (55.9%) patients, respectively. No differences were observed between the two age groups (<18.6 years and ≥18.6 years) in terms of the clinical or pathological characteristics of thyroid cancer: risk classification (p = 0.69) and American Thyroid Association pediatric risk level (p = 0.24). Compared with those from previous reports, few surgical complications were observed. Conclusions: Patients with thyroid cancer diagnosed with TUEs underwent safe and minimally invasive operations, and careful postoperative follow-up was provided. The pathological findings of the detected thyroid cancers indicated that the majority were classical papillary carcinomas, and approximately half of the patients had extrathyroidal or lymphovascular invasion. No differences were observed between the two age groups in terms of the clinical or pathological characteristics of thyroid cancer.

Experimental application of graphene quantum dots for the removal of nuclear materials from metal and plastic surfaces

This study explores the application of graphene quantum dots (GQDs) as innovative nanomaterials for the efficient removal of nuclear materials from metal and plastic surfaces, especially in contexts involving terrorist threats, such as &amp;ldquo;dirty bombs&amp;rdquo; and radiological dispersal devices (RDDs). These devices use conventional explosives combined with radioactive materials to contaminate large areas, posing significant risks to health and the environment. This investigation addresses the growing global concern about the use and threat of such weapons, particularly in the context of escalating wars and the increasing vulnerability of nuclear facilities to security breaches. Our focus is on the unique properties of GQDs&amp;mdash;such as their chemical stability, high surface area, quantum confinement effects, and electronic characteristics&amp;mdash;that enhance their ability to effectively adsorb radioactive isotopes. We examine the potential of GQDs to interact with various radioactive materials, focusing on isotopes commonly associated with RDDs, such as cesium-137, cobalt-60, strontium-90, and iridium-192. Functionalization techniques are employed to enhance the interaction of GQDs with specific isotopes, thus improving the decontamination process. Our findings reveal that GQDs can efficiently remove iodine-131 (I-131) from several metals: Aluminum (91.27%), zinc (98.67%), and monel (96.40%). They also demonstrate high efficiency in removing I-131 from rigid polyvinyl chloride. On the other hand, GQDs presented moderate efficiency in removing technetium-99m, with removal rates of 64.93% from monel, 55.11% from aluminum, and 41.80% from zinc. Overall, GQDs could play a crucial role in mitigating the consequences of dirty bomb detonations, offering a quick and effective method to reduce radiological impacts in affected areas. This research enhances our understanding of nanomaterials in responding to radiological emergencies, presenting GQDs as a viable solution to contemporary challenges in public health and safety. The implications of this study extend beyond immediate decontamination, suggesting broader applications of GQDs in environmental safety and nuclear safety protocols.

Fukushima nuclear wastewater discharge: An analysis of the international regulatory framework

This study examined the international legal framework that applies to Japan’s resolution to release nuclear wastewater from the Fukushima Nuclear Facility into the Pacific Ocean during the Summer of 2023. While the International Atomic Energy Agency (IAEA) published a report on July 4, 2023, asserting that Japan’s plans align with safety standards and would result in a minimal radiological impact on people and the environment, concerns over potential pollution of the global marine environment and opposition from neighboring countries persist. Notably, China disputed the IAEA’s findings and imposed a de facto ban on Japanese seafood imports. This incident has raised significant global environmental concerns and legal disputes. This analysis focused on the international norms and regulations governing marine environmental protection and nuclear safety relating to Japan’s decision. Various existing marine ecological protections, nuclear safety conventions, and specific articles were deemed pertinent to the situation. However, the application of these measures remains characterized by ambiguity and uncertainty. Consequently, the study argues for establishing a more effective and authoritative nuclear wastewater governance framework to address the distinct challenges associated with nuclear wastewater management.