• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2670-2677
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• 2023

In the nuclear safety studies, a new trend refers to the evaluation of uncertainties as a mandatory component of best-estimate safety analysis which is a modern and technically consistent approach being known as BEPU (Best Estimate Plus Uncertainty). The major objectives of this study consist in performing a study of uncertainties/sensitivities of the major analysis results for a generic CANDU 6 Nuclear Power Plant during Station Blackout (SBO) progression to understand and characterize the sources of uncertainties and their effects on the key figure-of-merits (FOMs) predictions in severe accidents (SA). The FOMs of interest are hydrogen mass generation and event timings such as the first fuel channel failure time, beginning of the core disassembly time, core collapse time and calandria vessel failure time. The outcomes of the study, will allow an improvement of capabilities and expertise to perform uncertainty and sensitivity analysis with severe accident codes for CANDU 6 Nuclear Power Plant.

• Journal of Mechanical Science and Technology
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• 제15권10호
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• pp.1417-1422
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• 2001

Since fracture surface presents clear evidence to describe the circumstances of material failure event, analysis of fracture surface should provide plenty of useful information for failure prevention. Thus if we extract proper information from the fracture surface, the safety evaluation, for plant component could be more accurate. In general, the chaotic morphology of fracture surface is determined by the degree of material degradation as well as by other factors such as type of load, geometry of specimen, notch condition, microstructure of material and environment. In this research, we developed a fractal analysis technology for the fracture surface of aged turbine rotor steel based on the slit-island technique using an image analyzer. Moreover the correlation between the fractal dimension and the aging time was studied.

• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.499-507
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• 1988

The pressure suppression pool of BWR(Boiling Water Reactor) is subjected to hydrodynamic impact in the event of a LOCA(Loss of Coolant Accident). The pressure increase in the reactor dry cell would force the existing water of a vent pipe into the suppression pool. When the water is ejected through the pipe opening into the suppression pool, an abrupt downward force is transmitted to the suppression pool floor. Consequently, many structures installed within the pool must be able to withstand these forces. In order to determine the optimum safe locations of the pool structures, numerical analysis have been carried out to investigate the hydrodynamic behavior of the water jet. In the present analysis, a two-dimensional numerical model is utilized to solve transient flow equations.

• Structural Engineering and Mechanics
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• 제89권4호
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• pp.399-409
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• 2024

Assessment of existing concrete bridges is a challenge for owners. It has greater economic impact when compared to designing new bridges. When using conventional linear analyses, judgment of the engineer is required to understand the behavior of redundant structures after the first element in the structural system reaches its ultimate capacity. The alternative is to use a predictive tool such as advanced nonlinear finite element analyses (ANFEA) to assess the overall structural behavior. This paper proposes a new reliability framework for the assessment of existing bridge structures using ANFEA. A general framework defined in previous works, accounting for material uncertainties and concrete model performance, is adapted to the context of the assessment of existing bridges. A "shifted" reliability problem is defined under the assumption of quasi-deterministic dead load effects. The overall exercise is viewed as a progressive pushover analysis up to structural failure, where the actual safety index is compared at each event to a target reliability index.

• Journal of Korean Neurosurgical Society
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• 제67권3호
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• pp.299-307
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• 2024

Cerebral cavernous malformation (CCM) is a vascular anomaly commonly found in children and young adults. Common clinical presentations of pediatric patients with CCMs include headache, focal neurological deficits, and seizures. Approximately 40% of pediatric patients are asymptomatic. Understanding the natural history of CCM is crucial and hemorrhagic rates are higher in patients with an initial hemorrhagic presentation, whereas it is low in asymptomatic patients. There is a phenomenon known as temporal clustering in which a higher frequency of symptomatic hemorrhages occurs within a few years following the initial hemorrhagic event. Surgical resection remains the mainstay of treatment for pediatric CCMs. Excision of a hemosiderin-laden rim is controversial regarding its impact on epilepsy outcomes. Stereotactic radiosurgery is an alternative treatment, especially for deep-seated CCMs, but its true efficacy needs to be verified in a clinical trial.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2017년도 추계학술대회
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• pp.34-35
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• 2017

Under the STCW Convention, marine engineers are required to have a satisfactory level of maritime English proficiency so that they can successfully perform their duties on board or maintain and operate the various equipment and facilities installed in the ship. More specifically, the importance of the engineers' written communication skills has been highlighted since their documents (for instance, post-work records, legal, and/or internal reports) have a significant legal impact in the event of a marine casualty or maritime crime. To suggest the necessity of developing standard engineering logbook phrases (SELP), therefore, this paper will closely analyse three-month authentic marine engineers' work records written by Korean officers. From the analysis, the problems and errors in the logbook will be analysed, and considerations to be taken into account in the development of SELP will be illustrated. Finally, the future actions for this standardised written communication for the logbook entry will be sought.

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.313-326
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• 2017

The systematic management of plant risk is crucial for enhancing the safety of nuclear power plants and for designing new nuclear power plants. Accident sequence precursor (ASP) analysis may be able to provide risk significance of operational experience by using probabilistic risk assessment to evaluate an operational event quantitatively in terms of its impact on core damage. In this study, an ASP methodology for two operation mode, full power and low power/shutdown operation, has been developed and applied to significant accident precursors that may occur during the operation of nuclear power plants. Two operational events, loss of feedwater and steam generator tube rupture, are identified as ASPs. Therefore, the ASP methodology developed in this study may contribute to identifying plant risk significance as well as to enhancing the safety of nuclear power plants by applying this methodology systematically.

• 한국시뮬레이션학회논문지
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• 제1권1호
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• pp.87-102
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• 1992

This paper presents the development of event-driven system level simulation tool SMPLE(Smpl Extende, an extention fo smpl) and its application to the performance analysis of multiprocessor computer systems. Because of its data structure, it is very difficult to change, expand or add new functions to simulation language smpl implemented by MacDougall. In SMPLE, we change data structure with structure and pointer, add new functions, and enable dynamic memory management. Using new data structure, facilities, and functions added in SMPLE, we simulate job processing of a shared bus multiprocessor system with autonomous hierarchical I/O subsystem. We set system performance contribution of subsystems and units. The impact of disk I/O on system performance is evaluated under vairous conditions of number of processors, processing power, memory access time and disk seek time.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2295-2297
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• 2003

The major problem encountered in satellite design is EMI (Electro-Magnetic Interference) and EMC (Electro-Magnetic Compatibility). Here, our focus is on the effects of protons on the electronic system. The SEU (Single Event Upset) results from the level change of stored information due to photon radiation and temperature in the space and the nuclear power plant environment. The impact of SEU on PLD (Programmable Logic Devices) technology is most apparent in ROM/SRAM/DRAM devices wherein the state of storage cell can be upset. In this paper, a simple and powerful test techniques is suggested, and the results are presented for the analysis and future reference. The test results are compared with that of JPL test report. In our experiment, the proton radiation facility available at KIRAMS (Korea Institute of Radiological Medical Sciences) has been applied on a commercially available SRAM manufactured by Hynix Semiconductor Company.

• 무역상무연구
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• 제37권
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• pp.217-250
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• 2008

The International Ship and Port Facility Security (ISPS) Code which was developed as the main response of the shipping sector to the miserable event of 11 September 2001 came into effect on 1 July 2004. The ISPS Code designed to detect and eliminate security threats affecting ships and port facilities used in international trade will significantly impact not only on the management and operation of the shipping industry but also on maritime law despite the fact that it is the regulatory framework of public law. It is expected that implementing the ISPS Code will contribute to reinforcement of maritime security on the one hand. However, on the other hand, more intensified security inspection and control measures of port states will also cause delay and additional costs which cause uncertainty in allocating security risk and cost between the contracting parties. Therefore, it is desire to insert new security clause dealing with main security issues or adapt existing clauses to new shipping environments to minimize disputes.