Passive Safety Systems Research Articles

Experimental Analysis on Safety System of a Simulated Small Scale Pressurized Water Reactor System with Intelligent Control

Reactors are widely used in the nuclear power plant due to the rapid demand for electricity by reducing the greenhouse effect. However, the effectiveness of the nuclear reactor depends on an adequate safety system. Hence, temperature and heat transfer are two critical parameters for any reactor in operation for which intelligent temperature control with an integrated safety system is essential. Therefore, the present study has emphasized the development of a simulated small-scale water-based reactor with intelligent control and safety system and examined through the analysis of thermal-hydraulic parameters. Radial heat transfer of an electric rod used as fuel in the primary circuit has been analyzed by taking sensor reading in various positions of the core. The developed system is self-controlled with all possible active and passive safety systems. Consecutively, the prototype has also been designed including manual adjustment to ensure a fail-safe environment. The system is capable to operate at temperatures between 80°C and 120°C, although the design can withstand up to 200°C. The data of the experiment are taken under the pressure of 200 kPa at 120°C temperature. Results show that heat output of 2116.09 kJ has been obtained from the system against heat input of 2514.80 kJ, which gives an efficiency around 16% of the developed system.

Optimasi Parameter Desain Multi-Cell Hexagonal Crash Box terhadap Absorbsi Energy Impact dengan Metode Taguchi

The crash box is a passive safety system placed between the bumper and the mainframe of the car that functions as an energy absorber to reduce the impact of driving accidents. The purpose of this study is to determine the optimal level of factors and analyze the factors that provide the most significant effect on energy absorption in a multi-cell hexagonal crash box. Identification of parameters that affect the crash box in energy absorption, namely: the position of placement hole (P), the distance of position hole (L), the thickness of crash box (t), and the hole diameter (D). The modeling method has used the design of the crash box by utilizing a computer simulation with software ANSYS 17.0. This research uses aluminum material type AA 6061-T4 and impactor material uses structural steel. Modeling loading using the frontal crash test method. In this modeling, the impactor with a speed of 7.67 m/s with a deformation length of 100 mm. This research uses the experimental design of the Taguchi method with the L27 orthogonal array. The optimization result were obtained optimum design parameter multi-cell hexagonal crash box with parameter settings P = inner wall; L = 112.5 mm; t = 2 mm, and D = 6.6 mm. Based on the calculated F value ≥ F Table, the factors P, t, and D affect the ability to absorb energy. Thickness crash box (t) has the highest contribution of 98.10% in increasing the value of energy absorption.

Safety cases for design-basis accidents in LWRs featuring passive systems Part 2 – Numerical investigations

This paper deals with the improvement and validation of numerical tools for the simulation of design basis accidents in nuclear power plants equipped with passive safety systems. Numerical models are implemented in the framework of the 1-D thermal–hydraulic system code ATHLET developed by GRS. Experimental reference data for the validation were obtained at the INKA test facility, a model of the KERENA reactor, reproducing the passive safety systems nearly at full scale.The validation effort focuses firstly on the accuracy of the models for the single passive components, and secondly on the ability of the numerical simulation to reproduce the interaction of all components of the KERENA design under realistic conditions as reproduced in the INKA test facility. Thermal-hydraulic models are presented and validated for two passive components of the KERENA reactor: the passive pressure pulse transmitter and the pressure-controlled flooding valve. Finally, the full model of the INKA facility, including these and other passive components, is discussed and numerical results for simulations reproducing three different design basis accidents are validated by comparison with the corresponding experimental data.

Визначення придатності пористих пресовок з алюмінію та алюмінієвих сплавів для використання в якості енергопоглинаючих елементів

This work reports the results of experimental studies on the applicability of porous pressings of aluminum alloys to passive safety systems. The porous pressings were made from aluminum and aluminum alloy powders with a particle size up to 200 ?m using a hydraulic press. The porosity was varied by varying the pressure in the press hydrosystem and the pressing force. The specimens were not sintered, and no plasticizer was added. To determine which specimen characteristic, the mass or the porosity, is more important, specimens of the same mass (0.01 kg) were used [the deviation did not exceed (2.7 ? 2.8) % ]. To determine the impact absorption ability of the porous pressings of aluminum and aluminum alloy powders, a vertical impact testing machine was used. The ram mass was 22.5 kg (weight 220 N), the fall speed was 5 m/s, and the fall energy was 300 J. The impact absorption ability of the porous pressings was determined by comparing the accelerations and rebound height of the ram in the presence of a porous pressing with their calculated free-fall values. The experiments showed that the use of specimens of maximum porosity decreases the impact energy by the value of the plastic work of deformation and the fracture energy. A comparison of the performance of different specimens showed that the energy absorption ability increases with porosity. As demonstrated by the experiments, porous pressings of aluminum and aluminum alloys can be used as energy -absorbing elements of passive safety systems for commercial and armored combat vehicles, and the impact absorption ability of porous fillers, in particular porous pressings of aluminum and aluminum alloys, can be determined using vertical impact testing machines. Using porous pressings of aluminum and aluminum alloys as an energy-absorbing material decreases the impact acceleration by a factor of 30 to 85 at an impact speed up to 5 m/s. The ability of a pressing to reduce the impact acceleration depends on its dimensions and porosity to a greater extent than on its mass. The greatest decrease in impact acceleration is provided by porous pressings of maximum porosity, in which the impact energy is converted to the plastic work of deformation and the fracture energy.

Numerical simulation of the crush behavior of tapered tubes

Abstract Traffic accidents are increasing as a result of an increasing number of vehicles and population growth in recent years. Active and passive safety systems are used in the vehicles we use today to reduce traffic accidents and prevent casualties. One of the passive security systems is the crush box (crashworthiness). It absorbs the energy generated during a crash by plastic deformation. In this study, tube height, diameter and thickness parameters were kept constant and degrees of conicity were varied 0°(flat tube),3°,7°,10°,12° and 15° The effects of conical crush boxes on axial crush behavior and their energy absorption ability, were investigated by Ls-Dyna explicit dynamic software.

Numerical simulation of the crush behavior of tapered tubes

Abstract Traffic accidents are increasing as a result of an increasing number of vehicles and population growth in recent years. Active and passive safety systems are used in the vehicles we use today to reduce traffic accidents and prevent casualties. One of the passive security systems is the crush box (crashworthiness). It absorbs the energy generated during a crash by plastic deformation. In this study, tube height, diameter and thickness parameters were kept constant and degrees of conicity were varied 0°(flat tube),3°,7°,10°,12° and 15° The effects of conical crush boxes on axial crush behavior and their energy absorption ability, were investigated by Ls-Dyna explicit dynamic software.

Road Safety: An Accident Prevention Using Intelligent Vehicular Network

The increasing rate of road fatalities has demanded the attention of the researchers, scientists, Industry and government organizations and technologies. The impact of accidents is simulated by rear-end collision with parameters such as vehicle position, direction, speed, inter-vehicle distance, and relative speeds, etc. Open source simulators have to be adopted to study and analyze various collision scenarios in vehicular networks. Safety mechanism proposed to minimize the possibility of accidents and mitigate the effect of the escalating incident. The proposed mechanism estimates the point of intersection, time to collision, and time to avoid accidents. Using parameters, the proposed mechanism able to determine accidents with 92.6% accuracy. The remaining 7.4% cases enable the passive safety system to help the people to stay alive, minimize the damage in case an accident.

Accident tolerant fuels (FeCrAl Cladding & Coating) performance analysis in Boiling Water Reactor (BWR) by the MELCOR 1.8.6 UDGC

Since the accident at Fukushima, one major goal of reactor safety research has been the development of more accident tolerant technologies that can mitigate or delay fuel degradation during a Beyond Design Basis Accident (BDBA). One major effort has been focused on increasing the capability of the fuel to be more tolerant of damage during an accident, i.e., Accident Tolerant Fuel (ATF) materials. In this work, we present the development of a generic BWR plant model, the modification of MELCOR to model ATF materials and the use of ATF materials (specifically FeCrAl alloy) as a coating on Zircaloy cladding or as a substitute material for cladding and fuel assembly canister material and its effect on severe accident progression, specifically, a Station Blackout accident. The analysis indicates that significant fuel degradation via fuel heat-up, clad oxidation, and hydrogen generation was delayed up to an hour if FeCrAl alloy was used as a clad and canister material. And, combined with the passive safety systems (i.e., the Reactor Core Isolation Cooling system, RCIC), the extended operation of these systems delayed fuel degradation further. However, an adverse effect should be emphasized for the monolithic FeCrAl design—it generated more hydrogen than the designs based on the Zircaloy due to the high reaction rate at a high temperature of FeCrAl. The design of the FeCrAl-coated-Zircaloy avoids this defect. Therefore, it is a promising choice to combine some of the beneficial traits of both materials.

Local flow structure and turbulence quantities inside a heated rectangular riser in turbulent forced and mixed convection heat transfers

Heat transfer deterioration in turbulent mixed convection affects the performance and safety of various pieces of industrial equipment. The reactor cavity cooling system (RCCS), a passive safety system in a very high temperature gas-cooled nuclear reactor (VHTR), incorporates rectangular riser channels to remove residual heat emitted from the reactor vessel, where turbulent mixed convection may occur under some emergency operation conditions. Understanding the heat transfer phenomena in the RCCS riser duct is, therefore, important to ensure the safety of the VHTR. To investigate the heat transfer phenomena inside a heated rectangular duct, a visualization experiment was carried out to obtain the local flow structure and turbulence quantities in turbulent forced and mixed convection heat transfers. Using the particle image velocimetry method, the velocity fields inside the heated test section were captured and time-averaged velocity distributions and root-mean-square velocity fluctuation distributions were obtained under various experimental conditions. Inside a rectangular test section, the flow had a nonaxisymmetric Reynolds shear stress distribution, related to secondary flows near the corner of the test section. According to the overall distributions of the local velocity and turbulence quantities under various experimental conditions, the mechanism of the heat transfer deterioration inside a heated rectangular riser was investigated in relation to the distribution of the Reynolds shear stress. Inside the rectangular test section with the intense buoyancy force, flow laminarization near the corner was preceded by that of the center with decreases in secondary flows and Reynolds shear stress distribution near the corner, which indicate a transition from forced to mixed convection. According to these results of the visualization experiments, it was estimated that the heat transfer deterioration in the rectangular riser would be affected by the aspect ratio of the test section.

A new design concept for ocean nuclear power plants using tension leg platform

This paper presents a new design concept for ocean nuclear power plants (ONPPs) using a tension leg platform (TLP). The system-integrated modular advanced reactor, which is one of the successful small modular reactors, is mounted for demonstration. The authors define the design requirements and parameters, modularize and rearrange the nuclear and other facilities, and propose a new total general arrangement. The most fundamental level of design results for the platform and tendon system are provided, and the construction procedure and safety features are discussed. The integrated passive safety system developed for the gravity based structure-type ONPP is also available in the TLP-type ONPP with minor modifications. The safety system fully utilizes the benefits of the ocean environment, and enhances the safety features of the proposed concept. For the verification of the design concept, hydrodynamic analyses are performed using the commercial software ANSYS AQWA with the Pierson-Moskowitz and JONSWAP wave spectra that represent various ocean environments and the results are discussed.

Development of passive protection devices for a power head of a high-speed multiple unit train at its collisions

Ukrainian passenger multiple-unit train upgrading supposes on creation of new power heads with passive safety systems (PSS) to save passengers lives, to reduce rolling stock damage and to minimize consequences at collisions. The purpose of this research is to develop energy absorption devices (EADs) for power head PSS according to DSTU EN 15227. EAD 1, EAD 2, EAD 3 designs have been developed with using successful experience of EP20 locomotive EADs creation and EAD prototype crash test results. EAD 1 design includes two elements which are located sequentially. Element 1 is a box with a single-layer package of hexagonal honeycombs inside. Element 2 is a truncated pyramid of honeycombs with triangular cells. EAD 2 design has three steps in element 2 form. EAD 3 design has been developed on the basis of element 1. It has been recommended to install two EAD 1 in a power head frontal part at the coupling level, two EAD 2 in power head window-sill part and two EAD 3 in the inter-car connection at the coupling level. Finite element simulation of EAD plastic deformation at an impact has been carried out for determination of design parameters.

Analysis of the influence of heat and mass transfer processes in the WWER equipment on the duration of effective operation of passive safety systems

The paper presents the results of an experimental study of the possibility of increasing the autonomous operation of passive safety systems of the WWER-1200 reactor facility. In the course of experiments conducted at IPPE JSC, processes that have a significant impact on the performance of these systems were studied. Non-condensing gases coming from the reactor negatively affect the operation of the steam generator in emergency condensation mode. They can significantly reduce the intensity of the condensation process and the duration of cooling the core. At a large-scale test facility HA-2M, the experiment was conducted to determine the maximum duration of a steam generator in the absence of removal of non-condensable gases from its tube bundle.

EXPERIMENTAL INVESTIGATION OF PAR DEVICE FOR HYDROGEN RECOMBINATION IN REKO-4 FACILITY

The Fukushima accident has proved that passive safety systems in reactors are necessary to avoid hydrogen accumulation. One of these systems are PAR (passive autocatalytic recombiner) to remove the hydrogen gases inside the containment in case of an accident. This paper aims to investigate a PAR device with catalyst sheets to calculate the hydrogen consumption, determine the temperature distribution, and PAR performance in the test facility. Test series were carried out in the test facility REKO-4 under atmospheric pressure and natural flow conditions. For the test purposes, hydrogen between 2.0 and 6.0 vol.% was injected into the vessel with the volumetric flow, 1.9 m3/h. The first rise in the temperature of the PAR inlet was found after 100 seconds of first hydrogen injection, this result demonstrated that hydrogen consumption started. The results from the test series show that the PAR device can remove hydrogen and the PAR performance can be determined from the test results.

Аналіз динамічної навантаженості екіпажів моторвагонного швидкісного поїзда з системою пасивної безпеки при його зіткненні з вантажним вагоном

The performance characteristics of the cars of a modern home high-speed motor-car train must meet Ukrainian State Standards DSTU EN 12663 and DSTU EN 15227 now in force in Ukraine, which regulate its crashworthiness and passive safety in emergency collisions. An integral part of new cars must be passive safety systems (PSSs) with energy-absorbing devices (EADs), which save the lives of the pasengers and the train crew and reduce car damage in a collision with an obstacle. The aim of this paper is to evaluate dynamic loads on the cars of PSS-equipeed motor-car train in its collision with a freight car according to Scenario 2 of DSTU EN 15227. The scientific novelty of the paper is a mathematical model for the study of a collision of a motor-car train with a freight car based on the authors’ model of a collision of identical motor-car trains (Scenario 1 of DSTU EN 15227) with account for the force characteristic of head car – freight car interaction in an emergency. The proposed mathematical model allows one to obtain the average values of the car accelerations and plastic deformations to compare them with their admissible values according to DSTU EN 15227. The paper presents the results of a study of dynamic loads on the cars of a PSS-equipped motor-car train in its collision at 36 km/h with a 80 t freight car for a reference train with a 80 head car and four intermediate cars of mass 50 t, which is the mass of the majority of cars on the 1,435 mm European railways, and 64 t, which is the typical mass of inremediate cars used in the 1,520 mm Ukrainian railways. The following protective devices developed at the Institute of Technical mechanics of the National Academy of Sciences of Ukraine and the State Space Agenccy of Ukraine are proposed for passive protection: EAD 1 devices of energy capacity 0.95 MJ to be mounted at the coupler level at the head car front end, EAD 2 devices of energy capacity 0.25 MJ and EAD 3 devices of energy capacity 0.3 MJ to be mouned at the coupler level at the head car rear end and at the ends of passenger cars of mass 50 t and 64 t, respectively, and EAD UL upper-level energy-absorbing devices of energy capacity of 0.12 MJ to be mounted at the head car front end under the window. It is shown that by the criteria of DSTU EN 15227 for a train with 50 t intermediate cars it is advisable to use the passive protection according to Scenario 1 (the front end of the head car is equipped wuth two EAD 1 and two EAD UL devices, its rear end is equipped with two EAD 2 devices, and the intermediate cars are equipeed with two EAD 2 devices at the front and at the rear), while for a train with 64 t intermediate cars it is advisable to use the passive protection according to Scebario 2 (the front end of the head car is equipped wuth two EAD 1 and two EAD UL devices, its rear end is equipped with two EAD 3 devices, and the intermediate cars are equipeed with two EAD 3 devices at the front and at the rear). The proposed mathematical model and the results obtained may be used in designing head and intermediate cars for a home motor-car passenger train in accordance with the DSTU EN 15227 requirements.

New Phase of Motor Vehicle Development

Development of motor vehicles has gone through several technological phases and today we are definitely in a new era that is primarily related to steering autonomy and vehicle propulsion systems. Although electric vehicles have become an absolute priority in some countries, their global expansion is happening and it is to be expected that they will become a near future in these regions as well. Today, special attention is drawn to advances in the development of autonomous driving systems, which will cause many changes in design, regulations and the environment. For the coming wave of change, we need to be adequately prepared and take part in global processes. In addition, it should be noted that the futuristic versions of vehicles capable of moving in multiple environments, on land, on or in water and in the air, are being widely promoted, and the EU is introducing mandatory application of some active and passive safety systems.

A system for the generation of in-car human body pose datasets

With the advent of autonomous vehicles, detection of the occupants’ posture is crucial to tackle the needs of infotainment interaction or passive safety systems. Generative approaches have been recently proposed for human body pose in-car detection, but this type of approaches requires a large training dataset for a feasible accuracy. This requirement poses a difficulty, given the substantial time required to annotate such large amount of data. In the in-car scenario, this requirement risk increases even further, since a robust human body pose ground-truth system capable of working in it is needed but inexistent. Currently, the gold standard for human body pose capture is based on optical systems, requiring up to 39 visible markers for a plug-in gait model, which in this case are not feasible given the occlusions inside the car. Other solutions, such as inertial suits, also have limitations linked to magnetic sensitivity and global positioning drift. In this paper, a system for the generation of images for human body pose detection in an in-car environment is proposed. To this end, we propose to smartly combine inertial and optical systems to suppress their individual limitations: By combining the global positioning of 3 visible head markers provided by the optical system with the inertial suit’s relative human body pose, we obtain an occlusion-ready, drift-free full-body global positioning system. This system is then spatially and temporally calibrated with a time-of-flight sensor, automatically obtaining in-car image data with (multi-person) pose annotations. Besides quantifying the inertial suit inherent sensitivity and accuracy, the feasibility of the overall system for human body pose capture in the in-car scenario was demonstrated. Our results quantify the errors associated with the inertial suit, pinpoint some sources of the system’s uncertainty and propose how to minimize some of them. Finally, we demonstrate the feasibility of using system generated data (which was made publicly available), independently or mixed with two publicly available generic datasets (not in-car), to train 2 machine learning algorithms, demonstrating the improvement in their algorithmic accuracy for the in-car scenario.

DRIVES ALERT SYSTEM IN THE CONDITION OF INFORMATION SHORTAGE

The article presents the results of an accident analysis in the Russian Federation. Trends in reducing the number of accidents have been identified, but over the past 5 years the severity of their consequences has remained at a high level, despite the development of vehicles active and passive safety systems. A new accident prevention system is proposed by informing drivers about the occurrence of an emergency in conditions of insufficient and limited visibility, based on measuring the parameters of the vehicle movement in real time using GLONASS/GPS technologies.

Study on the Performance of Primary Means of Measurement of the Hydrogen Concentration During Severe Accidents at NPP

This work is devoted to hydrogen safety security during severe accidents at NPP as well as the validation of equipment performance of passive safety systems under these conditions. The results of an experimental investigation of the performance of the primary means of measurement module of the hydrogen concentration control system under physicochemical actions on them due to the precipitation of insoluble aerosols, non-condensable gases, and oil vapor during severe accidents at NPP are presented. It is shown that the physicochemical actions do not significantly affect the performance of the primary means of measurement module of the hydrogen concentration control system.

Determination of the main parameters of the process of boric acid droplet entrainment from the WWER reactor in case of an accident

The article presents the results of a calculation study of the process of mass transfer of boric acid from a WWER reactor in the event of an accident. An analysis of the literature data in this field of study was carried out. As a result, it was found that studies of the mass transfer of boric acid were performed with parameters not typical for the emergency operation of passive safety systems of nuclear power plants with WWER. The results of the calculation of the main parameters in the WWER reactor in the event of an accident with a rupture of the main circulation circuit are shown. The calculation analysis allowed us to determine that the maximum diameter of the droplets entrained by the steam is in the range 0.11-0.23 mm.

Single-phase natural circulation in a rectangular loop with a finite capacity heat sink positioned below the heater section

One of the passive safety systems employed in nuclear reactors is a large water pool positioned at an elevation, which acts as a heat sink to remove decay heat from the reactor core in the event of an accident using the natural circulation phenomena. A large mass of water at an elevated position has concerns regarding the safety of support structure, and therefore an alternative methodology where the heat sink is positioned just below the heater section is investigated in this study. Results of an experimental and numerical investigation for the thermal-hydraulic behavior of single-phase natural circulation in a rectangular loop of height 4300 mm and width 1900 mm with the heat sink located at an elevation just below the heater section is reported here. The heat sink was a finite one, a constant volume insulated tank filled with water, whereas the heat source was a constant heat flux type. The loop was constructed with circular pipe elements with a nominal inner diameter equal to 40 mm. The heater section was 1m in height and three input power values equal to 1.15 kW, 1.55 kW, and 2 kW were used in the study. The flow behavior in a single and twin parallel heater system with a single riser was studied. The loop fluid is initially in a single-phase and becomes two-phase as the heat sink temperature rises, but only the results for the loop fluid in the single-phase regime are presented in the current study. The measured mass flow rate, after an initial transient, settles down to values which slowly decreases with time. The average temperature of the heat sink is shown to rise continuously with increasing time, demonstrating the effectiveness of the heat sink in removing the energy input to the working fluid in the heater section. However, the heat sink removes only 60–70% of the input heat while the rest is either lost to the ambient or utilized to raise the enthalpy of the working fluid.The Nusselt numbers in the heater section are also presented which steadily rise after an initial transient. In addition, the values are much higher than those for the corresponding Reynolds number values in forced convection due to the influence of buoyancy-induced convection. The Nusselt number is well correlated by the expression Nu‾=1.35(Ra*‾)0.3 for 2×105≤Ra*‾≤6.5×105and 600≤Re≤1000. Numerical predictions for loop flow rate, temperature variation, and sink temperature using the RELAP5/MOD3.2 code for the experimental configuration of the current study are presented which compare well with the measurements the maximum deviation being less than 10%. Numerical results for pressurizing the working fluid and permitting boiling in the heat sink to drive the system towards steady-state operation are also presented.