Passive Safety Systems Research Articles

Оцінка динамічної навантаженості екіпажів моторвагонного поїзда з сис-темою пасивної безпеки при його зіткненні з великим транспортним засо-бом

A topical problem of the home railway transport is motor-car train renewval, speed increase, and safety improvement in accordance with the Ukrainian State Standards DSTU EN 12633 and DSTU EN 15227, which specify the passenger car crashworthiness and passive safety, respectively, in emergency collisions with various obstacles. Relying on the world experience, researchers of the institute of Technical Methanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine developed a passive protection concept for home high-speed passenger trains in emergency collisions according to the DSTU EN 15227 requirements, proposals on the passive propection of a home motor-car train head car, lower- and upper-level honeycomb energy-absorbing devoces (EAD 1 and UL EAD, respectively) for the head car front part, and EAD 2 and EAD 3 low-level devices to be installed in intercar connecteions. The upper- and lower-level protective devices for home motor-car trains were developed based on finite-element simulation results using previous experience in the development of a passive protection device for a high-speed passenger locomotive and the results of a successful crash test of its proptotype. For Scenario 3, which chraracterizes a collision of a reference motor-car train at 110 km/h with a 15 t large road vehicle at a railway crossing, a model of a large deformable obstacle (LDO) was developed in compliance with the DSTU EN 15227 requirements. Finite-element models were developed to determine the force characteristics of interaction between the proposed head car passive protection devices and an LDO. The aim of this paper is to determine dynamic loads on a motor-car train equipped with passive protection devices in its collision with a large road vehicle. Based on a mathematical collision model for identical motor-car trains, a mathematical model was developed for a collision of a reference train with a large road vehicle at a railway crossing (Scenario 3) with account for the determined force characteristics of obstacle ? two EAD 1 low-level devices and obstacle ? two UL EAD upper-level devices interaction and the in-collision work of the head car structure. Dynamic loads on the cars of a reference train with a passive safety system (a head car mass of 80 t and intermediate car masses of 50 t or 64 t) were analyzed for its collision by Scenario 3. Two EAD layouts in the head car front part were studied. It was found that the proposed passive protection of the reference train cars meets the DSTU EN 15227 criteria for Scenario 3 for both EAD layouts and the determined variants of lower- and upper-level EAD use according to the intermediate car masses. The proposed mathematical model of dynamic loads on a passenger train with a passive safety system in its collision with a large road vehicle and the results obtained may be used in designing an up-to-date high-speed motor-car train to the DSTU EN 15227 requirements.

Separate-effect drainage tests in a core make-up tank

Passive safety systems are widely used in the advanced nuclear reactors, such as AP1000 and CAP1400. As an important component in the passive safety system, the core make-up tank (CMT) plays a key role for the safety injection and the core decay heat removal. Although the structure of the CMT system is simple, it involves many thermal-hydraulic phenomena, most of which significantly impact the peak temperature of the fuel cladding and the liquid level of the core. Since the CMT not only provides full-pressure injection but also triggers the auto depressurization system by its liquid level signal during small-break loss of coolant accident (SBLOCA), its thermal hydraulic behaviors significantly affect the performance of the passive core cooling system (PXS). Therefore, separate effect tests are inevitable to verify the feasibility of CMT applied to passive safety and injection systems and to study its operating characteristics. In this work, a separate-effect CMT test facility was designed and constructed. Experiments were performed to investigate the CMT's thermal hydraulic characteristics under the effects of system pressure, steam condensation, and flow friction. The study found that the delay drainage phenomenon is the result of a pressure balance between the pipe line and the gravity head. Whether delayed drainage occurs depends on the degree of subcooling of the fluid at the top of the CMT. The flowrate is not affected by the heat transfer coefficient of steam direct contact condensation. The flow friction of the drainage pipeline has no effect on the delayed drainage process, but has a great influence on the gravity drainage process.

Passive safety systems analysis: A novel approach for inverse uncertainty quantification based on Stacked Sparse Autoencoders and Kriging metamodeling

In passive safety system analysis, it is important to provide the uncertainty quantification of the Thermal-Hydraulic (T-H) code output (e.g., the amount of energy exchanged by the passive safety system during an accidental transient). This requires setting proper Probability Density Functions (PDFs) to represent the uncertainty of selected code inputs and the propagation of this uncertainty through the code. One way to obtain the PDF is by Inverse Uncertainty Quantification (IUQ) methods, which rely directly on experimental data and code simulation results. In this work, we present an innovative IUQ method based on: (i) Stacked Sparse Autoencoders (SSAEs) to reduce the problem dimensionality; and (ii) Kriging metamodels to lower the computational burden associated with the sampling of the uncertain input parameters posterior PDF by Markov Chain Monte Carlo (MCMC) (for which many model simulations are typically required). The novelty stands in the use of SSAEs for dimensionality reduction: this allows using directly the raw data available from experimental facilities or computer codes (typically characterized by small signal-to-noise ratios) without having to resort to filtering techniques, whose choice and setting are nontrivial and bias the results. The proposed approach is applied to the power exchanged by the Heat Exchanger (HX) predicted by the RELAP5-3D model of the PERSEO facility, characterized by a small signal-to-noise ratio (SNR) value. Principal Component Analysis (PCA) and SSAE are compared to explain the application of these methodologies in the context of IUQ and highlight the main advantages and drawbacks while also showing the suitability to deal with non-filtered (raw) data.

Impact Energy Absorbtion by Active Braking

Abstract Due to urbanization and the significantly increasing number of vehicles, urban roads are becoming more congested day by day, with the result that the rear-end collision has become the third most common type of collision. By developing and integrating active and passive safety systems, car manufacturers are working to prevent accidents and reduce the consequences of an accident. The present study examines a braking procedure and its applicability based on the integration of a passive and active safety system and provides development guidelines for the reduction of personal injuries and property damage in the event of a rear-end accident.

Inherent safety enhancement by design optimization of a floating absorber for safety at transient (FAST) in an advanced burner reactor

A floating absorber for safety at transient (FAST) is a passive safety system to enhance the inherent safety of sodium-cooled fast reactors (SFRs). This study optimized and improved the original FAST design in terms of the initial position, barycenter, eccentricity, reactivity worth, and diameter ratio of FAST to pin (k) in advanced burner reactor (ABR) cores. In contrast to previous studies based on average assembly analysis, a comprehensive design optimization study was conducted through transient simulations based on multiassembly analysis. Applying a damped FAST, which is an improvement over the original FAST design, enhanced the negative reactivity feedback in the oxide cores depending on the diameter ratio. Oscillatory behaviors were observed when the k of the damped FAST system was within 0.1 ∼ 0.55 for $1 of the FAST reactivity under an unprotected loss of flow event (ULOF). A damped FAST with a k of 0.7 maintained the lowest coolant temperature while suppressing the oscillatory behavior for $1 of the FAST reactivity. The results showed that damped FAST systems support negative reactivity feedback for the ABR oxide core and should be properly designed to avoid power and temperature oscillations depending on the FAST reactivity worth.

Application of Chernoff bound to passive system reliability evaluation for probabilistic safety assessment of nuclear power plants

There is an increasing interest in passive safety systems to minimize the need for operator intervention or external power sources in nuclear power plants. Because a passive system has a weak driving force, there is greater uncertainty in the performance compared with an active system. In previous studies, several methods have been suggested to evaluate passive system reliability, and many of them estimated the failure probability using thermal–hydraulic analyses and the Monte Carlo method. However, if the functional failure of a passive system is rare, it is difficult to estimate the failure probability using conventional methods owing to their high computational time. In this paper, a procedure for the application of the Chernoff bound to the evaluation of passive system reliability is proposed. A feasibility study of the procedure was conducted on a passive decay heat removal system of a micro modular reactor in its conceptual design phase, and it was demonstrated that the passive system reliability can be evaluated without performing a large number of thermal–hydraulic analyses or Monte Carlo simulations when the system has a small failure probability. Accordingly, the advantages and constraints of applying the Chernoff bound for passive system reliability evaluation are discussed in this paper.

An approach to constructing effective training data for a classification model to evaluate the reliability of a passive safety system

Although passive safety systems (PSSs) significantly contribute to the safety of nuclear power plants, evaluating the reliability of PSSs remains difficult due to a lack of data and insufficient understanding of a phenomenon on natural forces, which are driving forces of their safety functions. Within this context, approaches that evaluate functional failures of PSSs by combining Monte Carlo simulation with a thermal-hydraulic code have been proposed. In addition, several studies are trying to develop artificial intelligence models to reduce computational burdens in evaluating functional failures of PSSs. Despite such efforts, a large amount of training data is still required to train the model accurately: class imbalance between success/failure of PSSs exacerbates this problem. To address these issues, this paper proposes a method of obtaining effective training data by dealing with the data imbalance to reduce the number of data required. Case studies were performed to show the effectiveness of the proposed method and confirmed that classification models can be efficiently constructed through effective training data.

Pilot numerical study of new design of passive residual heat removal heat exchanger tubes

A passive residual heat removal heat exchanger (PRHR HX) is an important component of the passive safety system in an advanced nuclear power plant. In the current design of PRHR HXs with C-shaped tubes, thermal stratification occurs, and it inhibits heat transfer process. Here, we propose replacing these tubes with spiral tubes not only to enhance the heat transfer performance, but also increase cooling capacity. In this pilot study, CFD was used to compute the single-phase natural convection of both designs for comparison and analysis. The computation of a PRHR HX with C-shape tubes is validated with experimental data, and the use of Boussinesq approximation is justified. The computational results of simplified models suggest that with the same inlet and outlet temperatures (difference <0.001%), the new design with a spiral-shape tube not only alleviates the thermal stratification by 10.57% up to 600 s but also improves heat transfer by 75.5 W/m2·K. In addition, the proposed design has a smaller pressure drop by 7.19%, and the volume of the proposed design is smaller by 22.0%. It suggests that the proposed design not only saves material of tubes, but also results in more water in the water tank to cool the reactor core in emergencies, increasing cooling capacity of a PRHR HX. Finally, sensitivity analysis suggests that the influence of inlet velocity oscillation on both designs was similar regarding the magnitude of pressure drop, the average heat transfer coefficient, and the outlet temperature. The results obtained may be used to inspire new design for PRHR HX tubes.

The Aachen Rail Shuttle ARS - Autonomous and energy self-sufficient feeder transport

This article is about a research and development project that deals with the rail bus of the 3rd generation. The vehicle concept is aimed to be energyself-sufficient and locally emission free. It has the dimensions of a standard city road bus and is designed to operate autonomously on sight in rural areas. The Aachen Rail Bus (ARS) is intended to provide a significantly better service by shorter headways in order to attract more passengers from the countryside to the rail. The research challenges are to prove that the ARS can operate at line of sight, that the energy storage system is suitable for the proposed operation concept and that the passive safety system protects the light and relatively weak passenger compartment, which shall be easily exchangeable by an adequate interface to the chassis that includes all technical equipment.

Geometry contributions to natural convection heat transfer enhancement by the chimney effect

Natural convection heat transfer enhancement continues to be an evolving problem in the design of passive safety systems in nuclear engineering. Increasing heat rejection rates guarantees safety and higher heat duty. This study numerically investigated the influence of the geometry of an adiabatic extension appended downstream of a vertical heated cylinder. Four geometries comprising straight, diffuse, hyperboloid, and compound adiabatic extensions were studied. Nusselt number ratios, temperature distribution ratios, and mass flow rates were presented. Results showed that the compound extension geometry exuded high heat transfer enhancement capabilities by the chimney effect, and reduced wall temperature by up to 16% for the range of parameters studied. These findings are presented as a contribution to the design improvements of air-cooled passive systems, especially in advanced nuclear reactors.

The combination method of functional failure and device fault for passive safety system in nuclear power plant

Functional failure is one of the important causes for passive system failure, and some methods are developed for functional failure evaluation based on the thermal–hydraulic (T-H) model. However, the system equipment configuration is the prerequisite of the T-H behavior analysis and setting in the model, and the system configuration and the functional failure have one-to-one logical relationship which should be considered in the passive system reliability evaluation. In this paper, a logical combination method is put forward based on Fault Tree (FT) tool, and the simplification way is also proposed to improve the calculation efficiency. The Passive Containment Cooling System (PCCS) in AP1000 is analyzed as an example, the result shows that the functional failure under the configuration of one or more of the three parallel lines in valve gallery are available is the main contributor to the system failure, for the plant site in a subtropical area.

Exploring European Heavy Goods Vehicle Crashes Using a Three-Level Analysis of Crash Data.

Heavy goods vehicles (HGVs) are involved in 4.5% of police-reported road crashes in Europe and 14.2% of fatal road crashes. Active and passive safety systems can help to prevent crashes or mitigate the consequences but need detailed scenarios based on analysis of region-specific data to be designed effectively; however, a sufficiently detailed overview focusing on long-haul trucks is not available for Europe. The aim of this paper is to give a comprehensive and up-to-date analysis of crashes in the European Union that involve HGVs weighing 16 tons or more (16 t+). The identification of the most critical scenarios and their characteristics is based on a three-level analysis, as follows. Crash statistics based on data from the Community Database on Accidents on the Roads in Europe (CARE) provide a general overview of crashes involving HGVs. These results are complemented by a more detailed characterization of crashes involving 16 t+ trucks based on national road crash data from Italy, Spain, and Sweden. This analysis is further refined by a detailed study of crashes involving 16 t+ trucks in the German In-Depth Accident Study (GIDAS), including a crash causation analysis. The results show that most European HGV crashes occur in clear weather, during daylight, on dry roads, outside city limits, and on nonhighway roads. Three main scenarios for 16 t+ trucks are characterized in-depth: rear-end crashes in which the truck is the striking partner, conflicts during right turn maneuvers of the truck with a cyclist riding alongside, and pedestrians crossing the road in front of the truck. Among truck-related crash causes, information admission failures (e.g., distraction) were the main crash causation factor in 72% of cases in the rear-end striking scenario while information access problems (e.g., blind spots) were present for 72% of cases in the cyclist scenario and 75% of cases in the pedestrian scenario. The three levels of data analysis used in this paper give a deeper understanding of European HGV crashes, in terms of the most common crash characteristics on EU level and very detailed descriptions of both kinematic parameters and crash causation factors for the above scenarios. The results thereby provide both a global overview and sufficient depth of analysis of the most relevant cases and aid safety system development.

Numerical study on CMT boron replenishment strategy for an AP1000 nuclear power unit

The passive safety system is adopted in an AP1000 nuclear power unit to improve the operation safety of the whole unit. However, due to boron diffusion and periodic sampling, boron dilution occurs in the core makeup tank. The boron replenishment process in the core makeup tank is essential and becomes particularly important. Based on the validated models, this article numerically investigates the influence of the replenishment flow rate and the position on the boron distribution in the core makeup tank. The thermal fatigue phenomenon of the “T” connection caused by replenishment is analyzed. Finally, the replenishment strategy is proposed to benefit both boron mixing in the core makeup tank and eliminating the thermal fatigue of the “T” connection.

ROLE OF PASSIVE SAFETY SYSTEMS IN PREVENTION AND MITIGATION OF SEVERE ACCIDENTS AT NUCLEAR POWER PLANTS

Fukushima Daiichi accidents led to the worldwide update of the NPP safety requirements. Particular attention was paid to severe accidents both during the design of new NPP units and during the safety reassessment of existing ones. Performed safety reassessment of operating units was focused on development and implementation of technical means and strategies directed to prevention and/or mitigation of severe accidents. Technical solutions that are used in modern designs of reactor facilities involve several options for providing of heat removal from the core and containment. Such options include heat removal systems from the reactor core and from the containment of reactor facility. Most of such systems are based on passive principals of operation and do not require or require a minimum action of operating personnel. At the same time, reactor facilities that are operated in Ukraine are based on old VVER designs, which do not include passive safety systems for long-term heat removal (especially for the case of total station blackout, which was in the focus during safety reassessments, so-called “stress tests”). Thus, the necessity of such systems at Ukrainian NPPs with VVER-1000 and VVER-440 was discussed together with analysis of existing types of passive systems and their prevalence. Based on the results of performed analysis the feasibility of implementation at Ukrainian NPPs of a passive heat removal system from the core for VVER-1000 and from the confinement for the VVER-440 was identified. The possibility of implementation of such systems at Ukrainian NPPs requires a separate analysis. In addition, a general information on current state of passive systems reliability assessment was described. It should be noted that despite the reliability of passive safety systems is one of the important issues it is still poorly studied and require additional analyses.

A Hybrid Surrogate Modeling Approach for Vehicle Crash Simulations

Integrated vehicle safety – a combination of active and passive vehicle safety systems has the potential to increase occupant safety dramatically. To adapt the passive safety components such as belt and airbag to a given collision scenario, the system requires a priori knowledge of the collision consequences, i.e. via a camera, radar or lidar system. Therefore, real-time capable surrogate models are needed, that predict the vehicle decelerations during a crash with high accuracy. To combine the strength of both data-driven and physics-based surrogate modeling techniques, a hybrid surrogate model consisting of a machine learning-enhanced spring-damper-mass model, is developed in this work. Thereby, the spring-damper-mass model describes the deformation behavior of the vehicle structure. A neural network is then trained to predict the stiffness and damping parameters of the simplified physical model based on the impact angle, the velocity and the offset of the vehicles.

Dynamics of frontal crash in/without the presence of passive safety systems

The paper aims to debate on experimental retrieved accelerations from real crash tests, based on different scenarios, to enable assessment on driver potential injury. Scenarios included the presence of passive safety systems (e.g., airbag, seat belt) and test data are being processed to estimate the head injury criteria (HIC) followed by its correlation with abbreviated injury scale values (AIS). A dummy, average male resemblance, was developed in-situ and used in the experimental configuration. Signals were being acquired by few accelerometers disposed on the dummy’s head and thorax using a Pic DAQ system (DSD, Linz, Austria). Data processing and values of injury criteria underline the importance of passive safety systems proven HIC experienced a consistent decrease in the presence of both air-bag and seatbelt.

SAFETY OF UKRAINE’S NUCLEAR POWER INDUSTRY IN EXTREME OPERATING CONDITIONS

An urgent issue of the state (level) of safety of Ukraine’s nuclear power industry in extreme conditions is the situation of the Zaporizhzhia NPP, the largest in Europe, due to the station’s location in the war zone and difficulties in its management and operation, as well as the safety regulation of the station in the occupied territory. In the proposed article, the possibility of Zaporizhia NPP industrial site flooding is analyzed from the elaborated hydrodynamic model and justifying calculation; the conditions of ZNPP industrial site possible flooding are determined depending on the warhead power producing a corresponding destructive effect. Probabilistic approaches to assessing the Zaporizhia NPP safety objective state (level) in extreme conditions are insufficiently justified taking into account the lessons of the largest nuclear and radiation accidents. On the basis of a deterministic approach, the conditions of Zaporizhia NPP industrial site critical flooding due to extreme military action are identified. Flooding of the plant’s industrial site may cause two initial emergency events: a complete long-term de-energization of power units and violation of heat exchange conditions in spent nuclear fuel dry storage facilities. Prevention of flooding of the Zaporizhia NPP industrial site can be based on the construction of protective flood barriers on the cooling pond coast. Prospective directions to increase the accident management efficiency related to the nuclear power units’ passive safety systems modernization and improvement of operational symptom-oriented emergency instructions/manuals for managing severe (nuclear) accidents have been identified. An effective accident management strategy with complete long-term de-energization of WWER power units can be based on a comprehensive modernization of emergency recharge systems of steam generators with steam driven pumps and natural circulation circuits of passive heat removal systems from the pressurized reactor unit.

Electronic Systems Design for Driver Alertness

Abstract: Automotive systems are getting more responsive and giving feedback to the driver and passengers with the help of electronic systems ensuring safety. As seen the growth towards electric mobility engineers are more indulged in electronic systems and presenting innovative ideas for future developments. The presented simulation model of an electronic system combines the engine coolant temperature sensor, oxygen sensor, and seat belt warning system. The system is proposed using TINKERCAD software and the software is designed through Arduino. The driver will be able to see the temperature of the coolant and also can find out whether the air and the fuel mixture is rich or lean as well as be alerted for wearing a seatbelt. Keywords: Engine Coolant Temperature Sensor, Oxygen Sensor, Seat Belt Warning System, Electronics System for Vehicle, Arduino, Software Design using Arduino, Passive Safety System.

Designing a Vehicle Collison-Avoidance Safety System using Arduino

Abstract: The future of automotive relies on the mechatronic and electronic systems. The worldwide growth of automotive towards electronic systems suggests that driverless cars would soon be the common commuters. With such improvements safety of the passengers becomes first priority for the manufacturers. Nowadays automobiles come with high end technologies and quick responsive electronic systems. In addition to the passive safety systems, active safety systems definitely avoid collision thereby reducing the chances of injury and death. This project shows the working of an active safety system that is collision avoidance system. To create the model, TINKERCAD software has been used and a detailed working is explained. As a result, the system detects traffic and can alert the driver and stop the vehicle before meeting the collision. Keywords: Active Safety System, Arduino, Tinkercad, Vehicle Electronics System, Automotive Safety System, Collision Avoidance System, Self-Driving Car, Driverless Vehicle.

ПРИМЕНЕНИЕ АЭРОЗОЛЬНОГО МЕЛКОДИСПЕРСНОГО СПРЕЯ ДЛЯ ПОВЫШЕНИЯ ЭФФЕКТИВНОСТИ ОХЛАЖДЕНИЯ ОРЕБРЕННЫХ ТРУБ

The article presents an overview of works on the experimental and computational study of the processes of heat removal from heated surfaces using a water-air mixture. A sharp increase in the heat transfer coefficient is shown even when adding water with a mass content of 0.1 % to the air flow. The factors that determine the efficiency of the heat exchange process are listed: the shape of the water spray jet, the distance from the outlet point of the water-air flow to the heat exchange surface, the characteristics of the heat exchange surface, the method of jet formation, the size of droplets and the location of the outlet points of the gas-droplet flow. The weak applicability of the data available in the literature is shown for calculating the cooling of finned tubes of industrial heat exchangers using a water-air mixture. It is substantiated that in order to establish the most optimal cooling modes for each for a separate heat exchange surface, it is necessary to conduct experimental studies, due to the complexity of heat transfer processes and the presence of a large number of influencing factors. It is shown that the finned tubes of heat exchangers of the passive heat removal system of WWER-1200 have a number of important features that affect the efficiency of their cooling using a water-air mixture. An experimental setup has been developed and a technique has been proposed for performing experiments to study these processes as applied to heat exchangers of a passive WWER safety system.