Accident Situations Research Articles

Flexural Properties of Heat-Polymerized PMMA Denture Base Resins Reinforced with Fibers with Different Characteristics.

Polymethylmethacrylate (PMMA) has been the most-widely used denture base material in prosthetic dentistry for the last 80 years. It is still one of the best alternatives when new methods are inapplicable. Due to the lack of some physical inadequacies occurring during cyclic use and accidental situations, various reinforcement strategies such as using nanoparticles, wires, fibers, and meshes have been investigated and reported. In this study, it was aimed to conduct a comparative investigation of the effect of fiber additives with different characteristics on the flexural properties of heat-cured PMMA denture base resins. Glass fibers (GFs), polypropylene fibers (PPFs), and carbon fibers (CFs) having 3, 6, and 12 mm lengths and 0.25, 0.50, and 1.0% concentrations (v/v) were used for the reinforcement of PMMA denture base resins. The flexural properties (flexural strength, flexural modulus, and maximum deformation) were determined using a three-point bending test, and three-way ANOVA analyses with Bonferroni corrections were performed on the test results. The morphologies of the fracture surfaces were analyzed using scanning electron microscopy. All three fibers exhibited reinforcement in the flexural strength (p < 0.001) and flexural modulus (p < 0.001) regardless of their length and concentration. The group with 1.0% 12 mm CF-reinforced PMMA exhibited the greatest flexural strength (94.8 ± 8.8 MPa), and that with 1.0% 3 mm GFs displayed the lowest flexural strength (66.9 ± 10.4 MPa) among the fiber-reinforced groups. The greatest value of the flexural modulus was displayed by the 1.0% 3 mm CF-reinforced resin (3288.3 ± 402.1 MPa). Although the CF-reinforced groups exhibited better flexural properties, CFs are not favorable for use as reinforcement in practice due to the dark gray discoloration of the denture base resin. It was concluded that PPF is a promising material for the reinforcement of heat-cured PMMA denture base resins.

Numerical Study of the Robustness of Steel Frames with Bolted End-Plate Joints Subjected to Sudden and Gradual Internal Column Loss

The research project was carried out to estimate the robustness of flat steel-framed structures in a selected accidental situation. For this purpose, a multistage approach based on experimental tests and numerical analysis was performed. As the main objective of the work, a numerical dynamic analysis of the steel frames was performed under a sudden and gradual internal column loss scenario. FEA models were created in Abaqus software using solid and shell elements. Computer analyzes were carried out in a number of different cases, taking into account the size of the structure, the type of joints, and the method of removing the column from the structure. Detailed results on the axial forces and rotation of the joints under analysis are presented, and the robustness of the structures is estimated. In all cases of frames with flush end-plate joints, an insufficient level of robustness was observed and failures of the structures were obtained. In the cases of application of extended end-plate joints in frame analysis, the required level of robustness was reached in all cases and the stop of collapse was obtained. Finally, practical recommendations for designing robust joints and the whole frame structure are presented.

A Psychological Perspective on Risk and Crisis Management Skills

The primary concern of this article is to review the knowledge and ability of people to act to protect themselves and others in the face of various risks and hazards, and to manage accident and crisis situations. Relevant issues include the needs and requirements of emergency situations, people’s ability to respond to them, and factors that affect coping ability. The selected sub-areas are practiceoriented and defined in terms of real-world problems rather than theories or scientific concepts. One of the purposes of choosing to structure the review of risk, accident and crisis management psychology in this way is to emphasize the importance of human limitations and capabilities as an element in all areas of activity and responsibility. This approach, in turn, assumes that the review contains a broad theoretical base and multifaceted approaches, which are necessarily treated here rather generically.

Investigation of thermal hydraulic behavior of the High Temperature Test Facility's lower plenum via large eddy simulation

A high-fidelity computational fluid dynamics (CFD) analysis was performed using the Large Eddy Simulation (LES) model for the lower plenum of the High–Temperature Test Facility (HTTF), a ¼ scale test facility of the modular high temperature gas-cooled reactor (MHTGR) managed by Oregon State University. In most next–generation nuclear reactors, thermal stress due to thermal striping is one of the risks to be curiously considered. This is also true for HTGRs, especially since the exhaust helium gas temperature is high. In order to evaluate these risks and performance, organizations in the United States led by the OECD NEA are conducting a thermal hydraulic code benchmark for HTGR, and the test facility used for this benchmark is HTTF. HTTF can perform experiments in both normal and accident situations and provide high-quality experimental data. However, it is difficult to provide sufficient data for benchmarking through experiments, and there is a problem with the reliability of CFD analysis results based on Reynolds–averaged Navier–Stokes to analyze thermal hydraulic behavior without verification. To solve this problem, high-fidelity 3-D CFD analysis was performed using the LES model for HTTF. It was also verified that the LES model can properly simulate this jet mixing phenomenon via a unit cell test that provides experimental information. As a result of CFD analysis, the lower the dependency of the sub-grid scale model, the closer to the actual analysis result. In the case of unit cell test CFD analysis and HTTF CFD analysis, the volume-averaged sub-grid scale model dependency was calculated to be 13.0% and 9.16%, respectively. As a result of HTTF analysis, quantitative data of the fluid inside the HTTF lower plenum was provided in this paper. As a result of qualitative analysis, the temperature was highest at the center of the lower plenum, while the temperature fluctuation was highest near the edge of the lower plenum wall. The power spectral density of temperature was analyzed via fast Fourier transform (FFT) for specific points on the center and side of the lower plenum. FFT results did not reveal specific frequency-dominant temperature fluctuations in the center part. It was confirmed that the temperature power spectral density (PSD) at the top increased from the center to the wake. The vortex was visualized using the well-known scalar Q-criterion, and as a result, the closer to the outlet duct, the greater the influence of the mainstream, so that the inflow jet vortex was dissipated and mixed at the top of the lower plenum. Additionally, FFT analysis was performed on the support structure near the corner of the lower plenum with large temperature fluctuations, and as a result, it was confirmed that the temperature fluctuation of the flow did not have a significant effect near the corner wall. In addition, the vortices generated from the lower plenum to the outlet duct were identified in this paper. It is considered that the quantitative and qualitative results presented in this paper will serve as reference data for the benchmark.

Gameplayowe transgresje w grach cyfrowych

&#x0D; &#x0D; &#x0D; The latest and increasingly sophisticated digital simulations, often set in fantastical worlds, have become like laboratories in which players/ audiences can test their knowledge of culture, their ethical beliefs, interpretive skills, and anthropological imaginations. The article looks at games not just through the lens of their programmed poetics, but rather as laboratories in which experimentation becomes one of the elements of play, and gameplay touches the essence of the game – the activity, which is defined as dynamic competition within an adopted convention. One example of such experimentation is the transgressive way of conducting gameplay. However, creating a detailed typology of all possible transgressive gameplay is clearly not feasible, especially when taking into account accidental situations, such as when a player exploits a loophole or error in the programmed process without realizing that they are intentionally bypassing solutions designed by the creators. Nonetheless, intentional actions can be characterized in terms of three basic aspects – ingression (e.g., interference with computer programs), progression (e.g., fastrun, bypassing, etc.), and regression (transpositions, refunctionalizations, etc.). They concern both evidence of specific intentions and reveal ways of breaking rules, introducing one’s own rules, or forcing one’s own gameplay style.&#x0D; &#x0D; &#x0D;

Empirical modeling of ex-vessel debris bed formation in a pre-flooded reactor cavity

To secure the containment integrity of a nuclear power plant (NPP) in severe accident situation of ex-vessel corium release into the reactor cavity, a pre-flooding strategy of a reactor cavity has been adopted in various NPPs, including Korean PWRs. Molten corium released into the pre-flooded water pool is fragmentized and forms a particulate debris bed at the bottom of the cavity. To prevent the containment failure, it is important to properly remove the heat from the debris bed, which can be accomplished by water ingression into the bed. The water ingression characteristics are highly dependent on the debris bed shape. In this study, several main parameters affecting the debris bed shape were determined with respect to phenomena of free-fall & sedimentation, particle dispersion by steam spike and convection flow, and self-leveling. Then empirical model was developed and validated using the results of DEFCON (Debris bed Formation and COolability experimeNt) experiments. The model’s error was within ±10% when only free-fall & sedimentation were present. When steam-spike or convection was added to free-fall & sedimentation condition, the error increased to within ±20%. When all three were simultaneously present (free-fall & sedimentation, steam-spike, and convection), the model predicted most of the experimental results within ±20% error, except for several cases where convection had a significant impact. The effect of self-leveling itself was within ±10%. Considering all phenomena related to particulate debris bed formation, most cases had an error of ±20%. In addition, the debris bed shape formed by poly-disperse particles was predicted appropriately by the mode using the mass mean diameter of the particle size distribution, with an error range of ±20%. Consequently, it is expected that the proposed model of the debris bed shape can be utilized in an integrated severe accident analysis code for the evaluation on the ex-vessel debris bed coolability in the pre-flooded reactor cavity.

Validation of a carbon monoxide sampling method using polypropylene syringes: a reliable alternative method, easy to implement in the field or emergency situations

Carbon monoxide (CO) is a lethal gas, present during incomplete combustion of carbonaceous materials. CO may be present in certain occupational atmospheres or during accidental events such as fires. Colorless and odorless, its presence can only be detected analytically. Nevertheless, the measurement methods available today may either be lacking (not available, for example, for military people deployed in the field) or not completely adapted (interference for electrochemical detectors, cost for infrared detectors). Another solution is to take samples on the field and then analyze them in a laboratory. Tedlar® bags or canisters can be used for this purpose but are relatively cumbersome. An alternative, not well described in the literature and not metrologically validated, consists in using plastic syringes. In order to generalize the use of this system and to characterize it in terms of performance and stability over time, we conducted a validation study. This method was validated using a 50-cc polypropylene syringe, over a concentration range of 2 to 40ppm. The sampling system is efficient (sample yields between 101 and 102%) and repeatable (relative standard deviations under 2%). Storage tests were conducted on syringes containing 2 and 20ppm carbon monoxide, indicating that the syringes can be stored for up to 2weeks in the dark at room temperature. Coupled with a laboratory infrared analysis, this technique allows a high sensitivity and specificity. Easy to implement, rugged, inexpensive, and energy self-sufficient, this sampling system is attractive and offers a new solution for field or accidental situations.

Characteristics of coal resources in China and statistical analysis and preventive measures for coal mine accidents

In the process of green and smart mine construction under the context of carbon neutrality, China's coal safety situation has been continuously improved in recent years. In order to recognize the development of coal production in China and prepare for future monitoring and prevention of safety incidents, this study mainly elaborated on the basic situation of coal resources and national mining accidents over the past five years (2017–2021), from four dimensions (accident level, type, region, and time), and then proposed the preventive measures based on accident statistical laws. The results show that the storage of coal resources has obvious geographic characteristics, mainly concentrated in the Midwest, with coal resources in Shanxi and Shaanxi accounting for about 49.4%. The proportion of coal consumption has dropped from 70.2% to 56% between 2011 and 2021, but still accounts for more than half of the all. Meanwhile, the accident-prone areas are positively correlated with the amount of coal production. Among different levels of coal mine accidents, general accidents had the highest number of accidents and deaths, with 692 accidents and 783 deaths, accounting for 87.6% and 54.64% respectively. The frequency of roof, gas, and transportation accidents is relatively high, and the number of single fatalities caused by gas accidents is the largest, about 4.18. In terms of geographical distribution of accidents, the safety situation in Shanxi Province is the most severe. From the time distribution of coal mine accidents, the accidents mainly occurred in July and August, and rarely occurred in February and December. Finally, the "4 + 4" safety management model is proposed, combining the statistical results with coal production in China. Based on the existing health and safety management systems, the managements are divided into four sub-categories, and more specific measures are suggested.

Robustness of a full-scale precast building structure subjected to corner-column failure

Although many analytical and experimental studies have been carried out to date on the progressive collapse and robustness of cast-in-place reinforced concrete (RC) and steel building structures, very few experimental research works have been performed on precast concrete (PC) structures. The small number of publications on these experiments have focused on analysing the behaviour of subassemblies after the sudden loss of an internal column. This paper is the first to describe the construction of a full-scale purpose-built experimental PC building to study the sudden removal of corner columns and the structure’s ability to find alternative load paths (ALPs). The connections between the precast members were designed using existing simplified guidance for robustness. The results obtained from the test using gravity loads corresponding to typical load combinations defined in building codes for accidental design situations, showed a structural response governed by Vierendeel action with a clear contribution from the floor slabs. Load increase factors were obtained from the test results which can be applied by practitioners using simplified linear finite element models to account for non-linear dynamic effects in a simplified manner. This work is expected to form part of a large database of experimental results that are useful for developing advanced numerical simulations and parametric analyses.

Take a Swipe at Actinide Bioavailability: Application of a New In Vitro Method.

Filter swipe tests are used for routine analyses of actinides in nuclear industrial, research, and weapon facilities as well as following accidental release. Actinide physicochemical properties will determine in part bioavailability and internal contamination levels. The aim of this work was to develop and validate a new approach to predict actinide bioavailability recovered by filter swipe tests. As proof of concept and to simulate a routine or an accidental situation, filter swipes were obtained from a nuclear research facility glove box. A recently-developed biomimetic assay for prediction of actinide bioavailability was adapted for bioavailability measurements using material obtained from these filter swipes. In addition, the efficacy of the clinically-used chelator, diethylenetriamine pentaacetate (Ca-DTPA), to enhance transportability was determined. This report shows that it is possible to evaluate physicochemical properties and to predict bioavailability of filter swipe-associated actinides.

Türkiye'deki Havalimanlarında Yolcu ve Yük Taşımacılığı Faaliyetlerinde Yaşanan İş Kazalarının Durum Analizi

Air transport is of great importance in terms of both passenger and freight transport today. The aviation sector, which is growing and developing day by day, has a large share especially in terms of safety and security, occupational health and safety. This study has been prepared for the analysis of occupational accidents and occupational safety issues for both the sector and the employees, in the processes that are carried out meticulously in order to avoid any possibility of mistakes. Studies carried out at airports in Turkey with the code “51 – Air Freight” are grouped under two basic economic activity classifications in the Social Security Institution (SSI) system as “51/1 – Passenger Transportation by Air” and “51/2 – Freight Transportation by Air”. In the study, the situation of work accidents in these transportation activities at the airports in Turkey was analyzed and compared. With the analysis of the sector's occupational accidents data between the years 2013-2021; the number of workplaces, the number of insured personnel, the number of insured people who had a work accident, the period of temporary disability after work accident, the number of deaths after work accident, the number of employees per workplace, the number of work accidents per insured, the temporary incapacity period per work accident and the after-work accident are calculated. Lost working time was calculated. With the obtained data, the situation of occupational accidents in the sector was examined. According to the analysis of the data within certain periods, the passenger and freight transportation activities at the airports in Turkey were evaluated in terms of occupational health and safety.

Responding to disasters: about the governance of post-nuclear accident situations

Every society organizes itself to reduce the complexity of living together in order to ensure relative peace of mind for its members. Major technological accidents such as the Chernobyl or Fukushima nuclear accidents are violent disruptions that affect the quality of life of tens of thousands of people and generate increased distrust and anxiety among them as well as the questioning of the state system’s ability to restore some peace of mind. Past experience has shown that the measurement of radiation and the development of local projects with the support of professionals and experts prove to be effective levers for those affected to regain the ability to make decisions for their protection and to assess the protective actions implemented collectively. It also showed that restoring confidence and restoring the dignity of these people, seriously impaired by the accident, takes time.

BIOLOGICAL SAFETY AND BIOSECURITY SYSTEM IN RIBSP RESEARCH INSTITUTE FOR BIOLOGICAL SAFETY PROBLEMS

This article reflects the key aspects of the biological safety system and biological protection measures such as: biological risk assessment, engineering and technical means, personnel health control system, disinfection and disposal of solid and liquid waste, disinfection, disinfection and deratization, in industrial, scientific and experimental laboratories, insulators (vivarium’s) and facilities Research Institute for Biosafety Safety Problems in order to comply with the requirements of biosafety and biosecurity recommended by WHO, requirements of Sanitary rules and regulatory legal acts in the field of veterinary medicine. Search for information in Internet resources, for analysis, we used keywords in Russian and English. As a result, foreign and domestic literature sources on compliance with biological safety requirements and biological protection measures were analyzed.Analysis of literature sources has shown that failure to comply with these requirements and measures will lead to deliberate theft, leakage of strains of dangerous infectious diseases and failure to properly perform standard operating procedures, to an accident situation, laboratory infection of personnel. The measures taken to comply with the requirements of biosafety and biosecurity in the RIBSP significantly reduce the threat of infection of a person, the threat of the spread, penetration or theft of dangerous microorganisms.

Detecting Natural Disasters Using Deep Learning

Abstract: Natural disasters cannot be stopped, but they can be spotted, allowing people valuable time to flee to safety, as is often noted. One strategy is to utilize computer vision to supplement current sensors, which improves the accuracy of natural catastrophe detectors and, more significantly, enables people to take preparations, stay safe, and prevent/reduce the number of fatalities and injuries caused by these disasters. As a result, responding to natural disasters like earthquakes, floods, and wildfires requires extensive work by emergency responders and analysts who are on the ground. A low-latency data source for understanding crisis conditions has arisen in social media. While the majority of social media research just uses text, photos provide additional insight into accident and disaster situations.

Safety Benefits Assessment for Accident Tolerant Fuels in Consideration of Steam Generator Tube Degradation Using Dynamic Event Tree Analysis

Accident tolerant fuel (ATF) is expected to delay or prevent core damage by providing additional coping time under accidents involving loss of core cooling. The effect of extended coping time may vary depending on the plant response to accidents. Age-related component degradation that deteriorates plant performance over time could have an impact on the actual advantages of ATF. The potential safety benefits of two near-term ATF candidates, including Cr-coated Zr cladding and FeCrAl cladding, are assessed for a 2-in. loss-of-coolant accident with failed high-pressure safety injection using the dynamic event tree (DET) approach considering possible stress corrosion cracking of steam generator (SG) tubing under aging. The DET approach allows likelihood quantification of accident sequences leading to core damage, including stochastic variation of system response and human actions during accident mitigation. The safety benefits of the selected ATF claddings in terms of additional coping time and the core damage frequency reduction rate under specified accident situations were quantitatively estimated. The results show that the deployment of the two selected ATF claddings is expected to lead to longer coping times and lower core damage frequency due to the wider safety margin to peak cladding temperature they provide. The safety advantages would be greater as SG tube degradation proceeds. Thus, the two ATF candidates would lead to less severe consequences in terms of likelihood of core damage and susceptibility to the SG tube degradation than UO2-Zr fuel.

Analysis of RELAP5 prediction of countercurrent flow limitation in downcomer at upper plenum test facility

The relevance of the countercurrent flow limitation phenomenon is known in nuclear (emergency core cooling and accident situations) industries, such as a Loss of Coolant Accident (LOCA). The occurrence of countercurrent flow limitation (CCFL), which can exist in a host of places around the nuclear reactor system, will prevent the emergency cooling water, which is necessary to cool the core successfully flowing into the core from the downcomer of Pressurized Water Reactor (PWR) in the LOCA. Accurate prediction of the downcomer CCFL phenomenon is significant for the design and analysis of reactor safety. Among the experiments at Upper Plenum Test Facility (UPTF), various tests, test 6 and test 7 are studied in this research. Those tests are conservatively evaluated to predict the CCFL phenomenon at the downcomer. Above all, the methodology of node partition used in the RELAP5 model for the channels with cross-connections to represent the circumferential downcomer annulus was also studied. In particular, the nodes along the circumferential direction had a vital effect on the prediction of the steam velocity profile of downcomers. The influence of the CCFL model, including the most widely used Wallis-type and Kutateladze-type correlations, and the cooling-limited liquid-downflow behavior were analyzed. In addition, the pressure on the downcomer and steam flow rate of the break were monitored, and the predicted results were also analyzed.

Area Contamination Due to Dry Settling and Point Source Stack Effluents Washout by Precipitates

The article deals with an accidental situation development final stage accompanied by a powder explosion (combustion) incoming to a nuclear weapon part or dirty bomb and fissile nuclear materials dispergation with discharge in the air. The Formulas for impurity level express assessment fallen to the earth surface due to dry settling and stack effluents washout by precipitates are given.

Defect-Induced Adsorption Switching (p- to n- Type) in Conducting Bare Carbon Nanotube Film for the Development of Highly Sensitive and Flexible Chemiresistive-Based Methanol and NO2 Sensor.

Lightweight and flexible gas sensors are essentially required for the fast detection of toxic gases to pass on the early warning to deter accident situations caused by gas leakage. In view of this, we have fabricated a thin paper-like free-standing, flexible, and sensitive carbon nanotube (CNT) aerogel gas sensor. The CNT aerogel film synthesized by the floating catalyst chemical vapor deposition method consists of a tiny network of long CNTs and ∼20% amorphous carbon. The pores and defect density of the CNT aerogel film were tuned by heating at 700 °C to obtain a sensor film, which showed excellent sensitivity for toxic NO2 and methanol gas in the concentration range of 1-100 ppm with a remarkable limit of detection ∼90 ppb. This sensor has consistently responded to toxic gas even after bending and crumpling the film. Moreover, the film heat-treated at 900 °C showed a lower response with opposite sensing characteristics due to switching of the semiconductor nature of the CNT aerogel film to n-type from p-type. The annealing temperature-based adsorption switching can be related to a type of carbon defect in the CNT aerogel film. Therefore, the developed free-standing, highly sensitive, and flexible CNT aerogel sensor paves the way for a reliable, robust, and switchable toxic gas sensor.

Using ARGOS to simulate radioactive dispersion in the atmosphere from Fangchenggang nuclear power plant to Viet Nam

In this study, ARGOS software was used to simulate the atmospheric radioactive emissions from Fangchenggang nuclear power plant to Viet Nam. The simulated cases are hypothetical accidents with hypothetical source terms equivalent to level 6 of the International Nuclear and radiological Event Scale (INES). The results show the possibility of using ARGOS in simulating atmospheric dispersion, assessing radiation dose to humans from the Fangchenggang nuclear power plant accident to Viet Nam in some accident situations. Furthermore, the obtained results contribute to forecasting and supporting emergency response when an accident occurs in nuclear power plants.

Effect evaluation on performance issues of passive safety system – Part Ⅰ. Passive heat removal system

The passive safety system has advantages over active safety system since it has low dependence on the operator and external power supply. However, because the passive safety system operates with natural phenomena such as gravity, density difference, pressure difference, etc., the driving force is very low compared with active safety system. Therefore, the change of the internal/external environment of the system can have an effect on the performance of system. For this reason, it is necessary to evaluate whether the system can sufficiently perform the safety function in various accident situations. Since the existing safety standards for safety system have been developed for active safety systems, it is required to develop standards for performance evaluation of passive safety systems. For this reason, in this study, performance evaluation method for passive safety system is being developed. Since the identifying major performance issues is important for developing methodology, performance issues that can affect the natural circulation flow of the system, such as friction and heat loss of pipe within the system, are investigated and selected through the research related to safety regulation of passive safety systems. The effect of each performance issue on the system has analyzed by using conceptual problem for PHRS type passive safety system. For the effect analysis, passive safety systems using single/two phase natural circulation flow are conceptually designed by referring to the concept of the existing systems. For the effect evaluation, MARS-KS, which is system analysis code developed by KAERI, is used in this study. The main conclusions on the effect of each performance issues are drawn through the analysis. In addition, after the individual effect analysis of performance issues on passive safety system, a comprehensive assessment has performed to analyze the performance of system when several issues acted simultaneously.