Safety Margin Research Articles

PCMI Uncertainty and Sensitivity Analysis of Es-Salam Reactor Fuel Rods During Steady-State Operations

Nuclear safety relies heavily on the quality of the results of numerical simulation codes. Among the various components of the simulation of the installation are the pellet-cladding mechanical interaction (PCMI), and the peak cladding temperature (PCT). Although the correlations describing the physical, mechanical, chemical, and thermal phenomena that occur in nuclear installations have reached a high level of quality, there remain uncertainties on the final results due to uncertainties in the input parameters which cannot be eliminated. A realistic estimate of these uncertainties is necessary to evaluate the reliability of the simulation results. When the best-estimate approach plus uncertainty (BEPU) is employed in the design of a nuclear installation, design-basis accidents are studied more realistically. This method must be used even in the design of research reactors because they are at the origin of any development of nuclear technology. We propose through this study an uncertainty and sensitivity analysis of PCMI and PCT of a heavy water nuclear research reactor fuel rod. To determine the input parameters that influence PCMI and PCT, we utilize the FEMAXI-6 code. The thermodynamic table of the FEMAXI-6 code is adapted to the case of heavy water. Two system codes are used for uncertainty and sensitivity analysis: RELAP5 and PARET. The study confirmed that in the event of a shortage of heavy water, light water can be injected in its place to remove decay heat from the core and shut down the reactor safely. The safety margin between the PCT and the saturation temperature is reduced from about 10°C in the conservative approach to less than 1°C by the BEPU approach.

Cyber-Physical Systems for High-Performance Machining of Difficult to Cut Materials in I5.0 Era-A Review.

The fifth Industrial revolution (I5.0) prioritizes resilience and sustainability, integrating cognitive cyber-physical systems and advanced technologies to enhance machining processes. Numerous research studies have been conducted to optimize machining operations by identifying and reducing sources of uncertainty and estimating the optimal cutting parameters. Virtual modeling and Tool Condition Monitoring (TCM) methodologies have been developed to assess the cutting states during machining processes. With a precise estimation of cutting states, the safety margin necessary to deal with uncertainties can be reduced, resulting in improved process productivity. This paper reviews the recent advances in high-performance machining systems, with a focus on cyber-physical models developed for the cutting operation of difficult-to-cut materials using cemented carbide tools. An overview of the literature and background on the advances in offline and online process optimization approaches are presented. Process optimization objectives such as tool life utilization, dynamic stability, enhanced productivity, improved machined part quality, reduced energy consumption, and carbon emissions are independently investigated for these offline and online optimization methods. Addressing the critical objectives and constraints prevalent in industrial applications, this paper explores the challenges and opportunities inherent to developing a robust cyber-physical optimization system.

Surge-Elimination Strategy for Aero-Engine Transient Control

Abstract The fundamental principle of the transient state control method for turbofan engines, which is based on the acceleration ratio of high-pressure rotational speed (N-dot), involves sacrificing a portion of the safety margin to obtain satisfactory acceleration performance. However, it could induce surge in the engine's compressor. To prevent the destructive damage caused by surge to both the engine and its components, a surge-elimination control strategy for the engine based on an N-dot controller is proposed. First, the engine mathematical model, which incorporates the effects of engine volumetric dynamics, stall zone characteristics, and combustion chamber flameout characteristics, is established to simulate surge mechanism. Subsequently, the acceleration schedule of the N-dot is calculated by employing sequential quadratic programming (SQP) algorithm to solve the multiconstraint optimization problem, while designing the transition state controller of N-dot based on a high-order filter. Finally, the surge detection logic and surge-elimination strategy based on the μ-correction method are proposed and designed to realize active control of surge elimination. The simulation results demonstrate that the N-dot control method offers significant advantages in mitigating the steady-state errors resulting from inevitable engine degradations. The surge state is effectively suppressed by the proposed surge-elimination control method, and the surge duration is significantly shorten during the acceleration phases. Furthermore, compared to the one without any surge-elimination control, the proposed method decreases the acceleration time by 5.53%.

Diminishing Safety Margins of Telescoping-Boom Aerial Lifts

Abstract As the height of telescoping-boom aerial lifts increase, the severity of tip-over accidents obviously increases. To reduce the probability of tip-over accidents, manufacturers use countermeasures such as outriggers and wheel axels that expand in width to provide a more stable base, counterweights to offset the moments generated by the telescoping boom, and controllers that limit the machine configurations to within stable envelopes. The size of stability margins is determined by industry standards that set the approved load capacity of the machine to less than the load that would induce tip-over. This paper investigates the effectiveness of such load-based safety margins for very tall aerial lifts with telescoping-booms. The results indicate that the industry standards result in both inconsistent and often low safety margins.

Hierarchical Lateral Planning With Minimum Curvature Peak for Autonomous Vehicles

Abstract This study focuses on the lateral safety of autonomous vehicles. The aim is to provide greater safety margins for the motion controller under hazardous conditions by improving the planning methods. The proposed lateral planning method employs a hierarchical structure. First, a graph search method that considers road curvature is presented. This method benefits from the design of jump nodes and can generate a safe corridor in real-time by backtracking. Next, a concise and effective optimization problem is constructed in the Frenet frame. It is designed to optimize the path by incorporating the peak, integral, and differential of curvature into the objective function. By solving this problem using CasADi, the path within the safe corridor is obtained. Finally, the proposed planning method is combined with a model predictive motion controller and tested through simulation and experimentation on a real vehicle platform. This planning method has good scalability, adaptability, and real-time performance. Simulation and experimental results show that this method can help avoid exceeding lateral limits of road surface friction, improve path-following accuracy, and enhance the safety of autonomous vehicles in dangerous conditions.

Inertization parameters for alcohols and ketones with nitrogen and carbon dioxide

A flammable fuel/air mixture can be successfully prevented from entering the explosion range of concentration by the addition of an inert gas. This method of inertization is commonly used in industrial plants to keep processes safe. For this purpose, the oxygen concentration in the over-all mixture is often monitored, taking an appropriate safety margin into account. The mixture would not become flammable, independent of the amount of fuel added, while the oxygen content is below the so-called limiting oxygen concentration (LOC). The aim of this paper is to investigate the inertization-related characteristics of the two different inert gases nitrogen (N2) and carbon dioxide (CO2). The LOC of a series of alcohols and ketones was therefore measured. The experimental determination of the LOCs was carried out according to EN 1839 (2017) using the tube method at ambient initial pressure and suitable initial temperature to evaporate the liquid sample. Triangular diagrams, which represent the explosion ranges, were constructed from the results and additional inertization-related parameters derived: the minimum inert gas/air ratio (IAR) and the minimum inert gas/combustible gas ratio (ICR). It is well-known that carbon dioxide exhibits a stronger inerting effect than nitrogen. In agreement, the ratio LOC(CO2)/LOC(N2) was now determined to be a constant value of 1.33 ± 0.04 in the applied temperature range at ambient pressure. In inertization applications, this ratio in future helps to calculate LOC(CO2) from the much more often known LOC(N2).

Laparoscopic Posterior Pelvic Exenteration with Radical Vulvectomy for Intestinal-type Vulvar Adenocarcinoma

Vulvar intestinal adenocarcinoma is a rare malignancy. The most significant predictor of advanced vulvar cancer is achieving complete resection, although determining the optimal treatment for this rare histologic type remains uncertain. We report the case of a 63-year-old woman with a primary vulvar tumor suspected of having rectal invasion and inguinal lymph node metastases based on preoperative magnetic resonance imaging and computed tomography scans. To achieve complete resection of stage IIIC intestinal-type vulvar adenocarcinoma, we performed a laparoscopic posterior pelvic exenteration (PPE) and radical vulvectomy, along with bilateral inguinal lymph node dissection. This case report highlights the use of a novel hybrid procedure that combines laparoscopic PPE with radical vulvectomy and bilateral inguinal lymph node dissection for vulvar adenocarcinoma of the intestinal type. Laparoscopic PPE can be considered a minimally invasive approach for vulvar tumor when complete resection is achievable with an appropriate safety margin.

Implementation of dynamic start-up test experimental data as a main part of the nuclear code validation procedure: Developed RELAP5 model for VVER-1000

The main purposes of start-up tests in nuclear power plants (NPPs) are to ensure safe and reliable operation, verify system functionality, comply with regulatory requirements, optimize performance, and establish a foundation for ongoing plant operation and maintenance. However, the start-up tests of NPPs also could be used as a main part of the nuclear code validation procedure for several reasons including: realistic simulation, comprehensive evaluation, detection of code limitations, validation of safety margins and confidence in code predictions. The main purpose of the current study is to define and assess the validation procedure based on actual start-up test data. In this regard, the developed RELAP5 model has been validated against the actual data of VVER-1000 plant during a dynamic start-up test. The results of this full-scale validation show a good agreement between the developed RELAP5 model results and actual plant data. Finally, by defining a step by step validation procedure, it has been recommended to use the start-up phase test data as a more robust validation process which allow for full-scale validation of the nuclear code by comparing its predictions with actual plant measurements and also other advantages which have been demonstrated in the current study.

A new sliding rotation flap for functional lip reconstruction after cancer ablation: A technical note

ObjectiveTo establish a new technique for ensuring preservation of orbicularis oris muscle continuity and facial nerve for the lip reconstruction after moderate lower lip cancer ablation. MethodsThe surgical procedure consists of three steps. First, a Z-shaped skin flap is created around the nasolabial groove. The incision is made on the skin and muscular side, but not down to the oral mucosa. The angle of the mouth, orbicularis oris muscle, and facial nerve are not affected by this approach. Next, a careful obtuse dissection is performed to preserve the facial artery, facial nerve and mental nerve and to allow freedom of the flap. Finally, changing of the flap allows sliding rotation of the perioral tissue to reconstruct the lip defect. ResultsThe replaced flap pulled new mouth angle outward, and a good morphology was formed. Opening the mouth was sufficiently to wear the dentures. The sphincter movement of the lips was good, and the patient's pronunciation and eating were good. ConclusionThis method may be a useful option for the reconstruction of lower lip after cancer ablation because the resection with safety margins creates a large lip defect.

Simulation Validation of an 8-Channel Parallel-Transmit Dipole Array on an Infant Phantom: Including RF Losses for Robust Correlation with Experimental Results.

It is crucial to demonstrate a robust correlation between the simulated and manufactured parallel-transmit (pTx) arrays performances to release the currently-used, very restrictive safety margins. In this study, we describe the qualitative and quantitative validation of a simulation model with respect to experimental results for an 8-channel dipole array at 7T. An approach that includes the radiofrequency losses into the simulation model is presented and compared to simulation models neglecting these losses. Simulated S-matrices and individual B1+-field maps were compared with experimentally measured quantities. With the proposed approach, an average relative difference of ~1.1% was found between simulated and experimental reflection coefficients, ~4.2% for the 1st coupling terms, and ~9.4% for the 2nd coupling terms. A maximum normalized root-mean-square error of 4.8% was achieved between experimental and simulated individual B1+-field maps. The effectiveness of the simulation model to accurately predict the B1+-field patterns was assessed, qualitatively and quantitatively, through a comparison with experimental data. We conclude that, using the proposed model for radiofrequency losses, a robust correlation is achieved between simulated and experimental data using the 8-channel dipole array at 7T.

Best Estimate Plus Uncertainty Analysis of Station Blackout Transient in Pool-Type Research Reactor

Simulation of a station blackout (SBO) scenario was carried out for an open pool–type nuclear research reactor. The SBO transient was analyzed using the best estimate (BE) thermal-hydraulic code RELAP5/MOD3.2 to evaluate the performance of safety systems and inherent thermal inertia provided by the reactor pool in ensuring adequate core cooling during a prolonged SBO condition lasting up to 7 days. This encompasses assessment of cooling provided by battery-operated auxiliary pumps in the initial phase followed by setup of the natural convection cooling mode for the extended period. Best Estimate Plus Uncertainty (BEPU) methodology was applied for assessment of safety margins. This involved estimation of required simulations using the Wilks first-order formulation to achieve results within the tolerance limit of 95/95. Identification of relevant uncertainties and their propagation was carried out; subsequently, a case matrix for 59 simulation runs was generated using the Latin hypercube sampling method. The upper/lower bounds of uncertainty results were analyzed and compared with the BE code results. Later, sensitivity analysis was carried out using sensitivity coefficients generated using the Pearson and Spearman coefficient. The results show that the values of the crucial thermal-hydraulic parameters obtained with the tolerance limit of 95/95 met the acceptance criteria, with adequate safety margins.

Structure Design and Strength Analysis of the Glass Reinforcement Plastic (GRP) Malay Traditional “Perahu Bedar”

The Perahu Bedar, a traditional fishing boat in the Terengganu region of Malaysia, has been historically crafted from Cengal wood. In response to challenges posed by wood scarcity and limitations in skilled craftsmen, this study pioneers the exploration of Glass Reinforced Plastic (GRP) as a novel alternative material for constructing the traditional Perahu Bedar, measuring 4.32 meters in length. Through a rigorous analysis, the research delves into the structural design intricacies and strength attributes of the GRP Perahu Bedar, marking a significant departure from conventional wood-based construction methods. The study conducts a comprehensive analysis of the structure design and strength characteristics of the GRP Perahu Bedar. The weight, buoyancy force, and load distribution along the boat are analyzed. The data shows varying weight and buoyancy forces along the stations, with positive load values indicating upward forces contributing to buoyancy and negative load values representing downward forces. This analysis provides insights into the boat’s stability and distribution of forces. The sheer force and bending moment along the Perahu Bedar are evaluated. The sheer force values gradually increase or decrease along the boat, while the bending moment is highest at the midsection and decreases towards the ends. These results indicate the distribution of forces and stress on the boat’s structure, aiding in understanding its integrity and stability. The Factor of Safety (FoS) analysis demonstrates a FoS value of 2.2368, indicating a safety margin greater than 1. This suggests that the GRP Perahu Bedar design meets safety requirements and can withstand applied 
 
 stresses without exceeding yield strength. The FoS value provides assurance of structural integrity and safety during normal operating conditions. In summary, this study underscores the groundbreaking potential of Glass Reinforced Plastic (GRP) as a viable alternative to traditional wooden Perahu Bedar due to very high cost of Cengal Wood (wood that been used to build Peahu Bedar). By meticulously analyzing critical factors such as weight, buoyancy, load, shear force, bending moment, and Factor of Safety (FoS), the research offers invaluable insights into the structural integrity and safety aspects of GRP Perahu Bedar. These revelations not only herald a new era of sustainable and cost-effective boatbuilding practices but also serve as a crucial step towards safeguarding and perpetuating the rich maritime heritage of the region.

A green hydrogen production system based on solar-assisted biogas steam reforming

In the context of a carbon–neutral world, biogas reforming technology has potential to realize the production of green hydrogen with distributed production. Traditional green hydrogen production system based on biogas reforming dependent on high temperature condition during the reforming process; besides, biogas is always identified as a free energy resource in existing studies. This study develops a new way for green hydrogen production based on solar-assisted biogas steam reforming. The heat demand in the digester is considered in the newly proposed system; thus, more reasonable conclusion in regard to system thermal performance could be draw compared with existing studies. An advanced biogas reforming process with high steam-to-carbon molar ratio by introducing a parabolic trough solar collector is designed. At the same time, coupled with the carbon capture scheme proposed by previous study, it has great potential to realize hydrogen production with negative carbon emissions. Combined with the carbon deposition analysis, system integrated thermal performances are compared within the margin of safety. High steam-to-carbon molar ratio in the new system obviously improves the hydrogen production rate, with a maximum increase of hydrogen yield reaching 24.21 kg/h. In addition, the heat supply capacity is also significantly enhanced, which can meet the heat load of the digester when the ambient temperature is 4.03 °C (the reference system is only 20.19 °C). In terms of the integrated thermal performance, the hydrogen production efficiency of the new system is 33.60 percentage points higher than that of the reference system. This study provides a new idea for green hydrogen production from the perspectives of low temperature condition and negative carbon emissions.

A New Moment-Resisting Glulam Beam-End Connection Utilizing Mechanically Fastened Steel Rods—An Experimental Study

A new moment-resisting mass timber connection was designed based on the principles of force equilibrium in applied mechanics. The connection configuration utilizing two mechanically fastened threaded steel rods embedded into the end of a glulam beam section was experimentally investigated in this study. A gradually increasing transverse load was applied to the free end of a cantilevered beam, causing a bending moment on the beam-end connection until failure. Four different connection configurations were examined, each replicated twice to verify results. The beam connection parameters investigated were rod anchorage length (200 and 250 mm) and square washer size (38.1 and 50.8 mm). Test results show that increasing the washer size increased the connection bending strength by increments more significantly than those due to increasing the rod anchorage length. However, the connection configurations with the smaller-size washer, which failed mainly due to wood crushing under the washer, had higher ductility ratios than those with the larger-size washer, which failed due to steel rod yielding. In a real-life scenario, a structural element such as a glulam beam is usually loaded to approximately 50% to 70% of its design capacity, considering a reasonable margin of safety. The study estimates a maximum possible bending moment utilization factor for the strongest connection configuration that ranged between 34% and 48% compared to the maximum moment resistance of a supported glulam beam spanning an average length of 4.0 m to 6.0 m (a common span length in framed timber buildings) and has a cross-section size same as the one utilized in this study. This utilization factor is quite large for a timber connection, and thus, confirms a considerable moment-resisting capability of the new configuration developed in this study.

Simulation of damage under cyclic loading for API 5L X70 steel pipelines (fatigue test)

The most efficient way to move large volumes of gas and oil is through pipelines, either from points of production to storage locations or from storage locations to distributed points of end use. One of the main materials of gas transportation pipes is X70 material. Base on the importance of in-service API 5L X70 pipelines, it is important for the safe operation of this system to know the lifespan of pipelines, and predict fatigue crack growth (FCG) of API 5L X70 steel pipeline. The objective of this theme is to study the lifespan of pipelines used for the transport of natural gas, oil and water, manufactured by the company ALFAPIPE in the wilaya of Ghardaïa. The judicious choice for manufacturing metal is a crucial factor to ensure prolonged life duration and improve resistance to fatigue, as materials respond to loading with elastic or plastic deformation. Stresses applied to materials can result in permanent deformation, rupture, cracking or progressive degradation. Understanding the effects of applied stresses is essential for the selection and implementation of materials in industrial applications. Fatigue tests were carried out on API 5L X70 steel using simulations using ANSYS software. The life of different samples was determined for different thicknesses after applying repeated stresses. The obtained results demonstrate the material API 5L X70's sensitivity to fatigue and emphasize the significance of designing pipelines with sufficient safety margins to prevent premature failures caused by fatigue.

Infantile Myofibroma of the Frontal Bone: A Case Report

Background: Infantile myofibroma stands as the most prevalent fibrous neoplasm within the pediatric population, despite its rarity. The majority of these tumors manifest within the initial 2 years of life. Clinically, myofibroma lesions are classified into solitary and multicentric tumors. Methods: We present a case of infantile myofibroma located within the frontal bone of a 16-month-old infant. Initial evaluation of the swelling and its spread was conducted using CT and MRI scans. Subsequently, the diagnosis was confirmed through a core needle biopsy. Results: The tumor underwent surgical excision with 1 cm safety margin and immediate reconstruction with strips of calvaria bone graft. Histopathology of the specimen showed complete tumor clearance with actual margin of 7 mm. Conclusion: The surgical resection of cranial benign bone tumors should be meticulously planned with a multidisciplinary approach. Wherever possible, immediate reconstruction should be conducted to avoid the morbidity of a subsequent procedure.

Preliminary analysis of in-orbit operation accidents for an ultra-small Lithium-cooled space reactor power system

To study the safety characteristics of an ultra-small (5.2 MWt) lithium-cooled space reactor power system (ULCR) under postulated accidents, a transient analysis code for the ultra-small space reactor coupled with a closed Brayton cycle dynamic conversion and heat pipe radiator was established. A preliminary analysis of four typical postulated accidents occurring at 100 percent power in-orbit operation of the ULCR system was conducted to define postulated problem areas and establish safety requirements. The postulated accidents mainly include (1) reactivity insertions, (2) coolant partial flow loss, (3) turbomachinery failure, and (4) radiator partial failure. The results showed that: a) since the ULCR system was designed to operate at high-temperature conditions (coolant temperature greater than 1500 K), the safety margin of the ULCR system was small. Emergency shutdown control or reduced power operation action should be taken proactively to ensure ULCR's safety in different accidents. b) When the control rod was misoperated and large reactivity was inserted, the maximum temperature of the lithium coolant was very close to the saturation temperature (the difference was 24 K), and the system was operated at extremely high temperatures (the average temperature of the core coolant was 1750 K); c) In coolant flow loss accident, when the coolant flow of the system dropped below 40% of the rated mass flow, the lithium coolant boiling would occur in the primary loop system, and the emergency shutdown control action was required to ensure the safety of the system.

The method of research nuclear installation conversion at the decommissioning stage

The article examines the problem of forming scientific and technical programs for the conversion of research nuclear installations at the decommissioning stage, which arose in the aspect of justifying the possibility of extending the designated service life of all existing research nuclear reactors in Russia. To solve this problem, a methodology is proposed, which includes an information model and a process description of the necessary step-by-step actions, as well as a set of appendices in the form of documents justifying the most optimal ways to form a project for managing the quality of nuclear reactor conversion processes in relation to special life cycle conditions of specific nuclear reactors. The general view of the methodology is described: principles and methods of construction, structure. An example of the application of this technique in the conversion of the Hydra salt solution pulsed research reactor for the decommissioning stage is given. The purpose of the conversion of the Hydra reactor is to extend the designated service life by replacing non-repairable equipment ­ the vessel. The main criteria for justifying the residual life of the housing are formulated, which are the presence of a safety margin of the housing material, taking into account the accumulated fluence on more vulnerable areas and the justification of the integrity and tightness of the housing. For clarity, the conceptual information model of the methodology for justifying the safety of the process of replacing the Hydra reactor vessel is presented in the form of an Ishikawa diagram. The methodology represents a series of sequential scientific and technical activities, research and a finite number of step-by-step actions to achieve the final goal – extending the service life. The stages of the methodology for justifying the safety of replacing the Hydra reactor vessel are described, such as «clarification of initial data», «performing computational studies and laboratory experiments», «clarification of the requirements of methodological documentation» and «formation of a work plan» and «registration of licensing documents for operation».

Experimental Study on Optimizing Grouting Material Ratio for Rebar Sleeve Connections

In response to the inadequate performance reliability of existing prefabricated sleeve grouting materials, this study used an orthogonal experimental design method to prepare 16 sets of grouting materials based on C52.5 cement and ordinary river sand, with different water-cement ratios and varying amounts of additives including silica fume, defoamers, water reducers, and expansive agents. The effects of silica fume, defoamers, water reducers, expansive agent dosage, and water-cement ratio on the compressive strength, vertical expansion rate, and fluidity of the grouting material were studied. Based on the experimental results and comprehensive analysis, a formulation for high-performance grouting material with high reliability was determined, providing a greater safety margin for practical engineering applications.

Application Of Break Even Point (Bep) In Determining Profit Planning At Pt. Panorama Sentra Wisata Tbk

Break Even Point (BEP) analysis with profit planning has a strong relationship and can help companies determine optimal sales targets so that the company's goal of achieving maximum profits can be met. PT. Panorama Sentrawisata Tbk is a company that has gone public, it is hoped that the profits obtained will attract investors to invest in the company. For this reason, it is necessary to analyze the application of BEP in determining profit planning at PT. Panorama Sentrawisata Tbk. This research is quantitative with a descriptive approach. The data used in this research is secondary data. The data analysis method uses the BEP analysis tool which is equipped with MoS analysis. The level of data analysis carried out starts from cost classification, BEP analysis, and margin of safety. The research results obtained in achieving the 2023 profit plan of 80 billion are by selling a minimum of IDR. 2.727.418.455,56, with a Margin of safety or decline in sales that can be tolerated so that the Company is at the break-even point that it does not experience losses of IDR. 888,888,888.89 or 33%.