Search

• Korea's first dynamic discrete event tree methodology-based tool, DICE, developed. • Validation shows DICE reproduces results of conventional event trees. • DICE simulation highlights potential in analyzing success criteria issues. Although conventional probabilistic safety assessment (PSA) makes a sufficient contribution to evaluating the safety of nuclear facilities, it suffers some limitations in performing optimal assessments close to the actual behavior by reflecting time dependencies in accident management. However, integrated deterministic and probabilistic safety assessment (IDPSA) literally combines two methodologies to enable synchronized evaluation based on physical behavior, system availability of facilities, and operator's response. Dynamic integrated consequence evaluation (DICE) is one of the IDPSA tools developed for this purpose, which is the first achievement in South Korea and supported by a regulatory authority. Based on dynamic discrete event tree (DDET) methodology, DICE consists of a scheduler that supports the exchange of information between modules, including a physical module that computes thermal-hydraulic simulations, a diagnosis module that specifies branching points for safety systems, and a reliability module that provides system availability. This paper deals with numerical validation comparing the conventional deterministic and probabilistic results for a sample scenario with those of DICE, and discusses an application of DICE to support and extend the scope of conventional PSA through a case study. It is expected that DICE emphasizes the compliance with conventional PSA methodologies while providing magnified perception in investigating unforeseen scenarios. [ABSTRACT FROM AUTHOR]

• The change in the internal/external environment of the system can have an effect on the performance of PECCS. • This study has conducted the effect evaluation on performance issues as part of the performance evaluation methodology for PSS development. • Major performance issues (such as modeling of PECCS pressure, wall condensation in the system, and check valve) were identified through impact evaluation using the system analysis code, and the effects of major performance issues on the system were analyzed. • In this paper, the evaluation of performance issues has led to the identification of the main factors to consider in PECCS modeling. In this study, the effect of performance issues on the Passive Emergency Core Cooling System (PECCS), a type of Passive Safety System (PSS), was evaluated. The PECCS relies on natural phenomena such as gravity, density difference, and pressure difference to operate. Its driving force is lower compared to that of the active safety system, making it necessary to evaluate its performance in various transient situations. Major performance issues were identified through effect evaluation using a conceptual problem for the PECCS, and their effects on the system were analyzed using the system analysis code MARS-KS. Therefore, there are concerns about whether the PSS can sufficiently perform safety functions in various situations. In Korea, performance evaluation methodology for PSSs is being developed to dispel these concerns. As part of the methodology development, this study conducted the effect evaluation on performance issues. The study identified several major performance issues for the PECCS, including those related to pressure and heat loss of piping within the system, uncertainties in tank wall condensation modeling, and checks valve modeling. The evaluation of performance issues has led to the identification of the main factors to consider in PECCS modeling, which include: 1) the geometry and pressure drop of PECCS, 2) the occurrence of wall condensation in pipes and tanks, and 3) the behavior of check valves. Proper modeling of these factors is important in achieving accurate analysis results and preventing potential issues, such as premature check valve closure or incomplete coolant injection. In conclusion, the results of this study are expected to contribute to deriving safety analysis modeling guidelines for PSSs and design considerations for NPPs that utilize PSSs by improving the completeness of the developing performance evaluation methodology. [ABSTRACT FROM AUTHOR]

District 2-2 (or Saerom-dong), located in Sejong smart city, is designated as a 'Specially Designed Zone for Women'. The purpose of this paper is to investigate the gendered dimensions of this smart city district through gender analysis. This paper analyzes the planning, implementation, and post-occupancy stages of the district through a review of guidelines of gender-mainstreaming policies of Korean cities, interviews of experts involved, and a survey of 100 residents to gain an insight into how users perceive the spatial aspects of the women-friendly walking environment. Results show that, at the planning stage, little interprofessional communication occurs between smart city experts and 'women-friendly city' experts. At the implementation stage, this leads to incomplete gender-mainstreaming of the district. Post-occupancy survey results reveal, however, that despite these shortcomings, both women and men perceive the 'Specially Designed Zone for Women' to be safe. Even so, there is a gender difference in the perception regarding smart installations. CCTVs are more important to men than women, while on-site emergency bells are more significant to women than men. This indicates that women need more active safety systems than passive surveillance systems. This paper argues that a gendered perspective is needed for the more inclusive planning of smart cities. • The gendered dimensions of Sejong's smart city district are investigated in three stages. • There is little interprofessional communication at the planning stages. • This led to incomplete gender-mainstreaming of the district at the implementation stage. • Post-occupancy survey results reveal that both women and men perceive the 'Specially Designed Zone for Women' to be safe. • A gendered perspective is needed as women need more active safety systems than passive surveillance systems. [ABSTRACT FROM AUTHOR]

A Radioactive Waste Information Management System (RAWINGS) currently in operation mainly manages the inventory and history of the operating waste. The system has the disadvantages of the entered information needing to be transferred manually from the site to the system, information getting incorrectly entered during the process or information going missing. Recently, the Nuclear Safety and Security Commission (NSSC) and Korea Radioactive Waste Agency (KORAD) called for the development of a digital system that can show information transparently in real-time regarding the preliminary inspections of RAdioactive Waste (RAW) and the assessment of its suitability for disposal before the radioactive waste is delivered to the disposal site. A Digital Twin (DT)system is being developed for the safety management of radioactive waste to address the problems that these systems have and meet the needs of disposal operators. This paper introduces the DT technology that uses Augmented Reality (AR) technology enabling users to check the contents of small-packaged wastes in radioactive waste drums without opening them, Internet of Things (IoT) sensor technology that checks the status of the drums in the radioactive waste storage and the RAWINGS system. Based on the performance of a prototype Digital Twin consisting of three modules (AR, IoT and RAWINGS), the augmented reality enables users to see the shape information and filling rate of small-packaged wastes in the radioactive waste drums and includes Quick Response (QR) code management. The basic data of the radioactive waste used in the augmented reality, as well as small packaged wastes and repackaged drums, were processed in conjunction with RAWINGS. In addition, real-time monitoring of radioactive waste drums loaded in the designated space (Y zone: an area where combustible waste is loaded within radioactive waste storage and TEST area: a section where drums scheduled to be transported to the disposal site are loaded) of the radioactive waste storage was possible by transmitting IoT sensor signals attached to the drum to the digital twin. Currently, augmented reality has an important role in enhancing the visibility and intuitiveness of radioactive waste information for radioactive waste managers and workers by overlapping digital information about radioactive waste storage. Due to the nature of radioactive waste, it is difficult to know what waste is inside the enclosed drum. However, the results of this study confirmed that waste contained in radioactive waste drums can be identified in real time in the Digital Twin rather than in the radioactive waste storage. This technology will be useful in determining the conformity of the radioactive waste acceptance criteria required by KORAD before the delivery of radioactive waste drums to disposal sites. [ABSTRACT FROM AUTHOR]

• Development of long term cooling safe shutdown analysis methodology using passive safety system. • Long term cooling safe shutdown performance analysis for the SMART reference plant. • Sensitivity analyses of the passive system failures on the long term cooling safe shutdown performance. Passive safety systems have been adopted in reactor design to enhance safety especially in SMRs after the TMI-2 accident in 1979. The passive system has high operational reliability with natural driving forces such as gravity, natural circulation and stored energy. In recent years, development of innovative SMRs has emerged as a global R&D initiative for sustainable energy to challenge the carbon neutrality of climate change. The passive safety system makes reactor design simple and thus enhances the reliability of the reactor. As advanced reactors adopt passive safety systems, regulatory requirements and guides are required. Thus, development of regulatory guide and detailed regulatory review methodology for the passive safety systems is needed. In this paper, long term cooling safe shutdown acceptance criteria and performance analysis methodology are proposed for the regulatory standard design approval for the SMART100 integral reactor with fully passive system which has been jointly developed by KAERI in Korea and K.A.CARE in Saudi Arabia. The long term cooling safe shutdown performance analyses are performed until 72 hours to evaluate the methodology, and sensitivity analyses are also performed to provide a technical basis for the regulatory independent review for the long term cooling performance of the SMART100 passive safety systems. [ABSTRACT FROM AUTHOR]