• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2534-2546
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• 2021

Nuclear emergency preparedness and response is an essential part to ensure the safety of nuclear power plant (NPP). Key support technologies of nuclear emergency decision-making usually consist of accident diagnosis, source term estimation, accident consequence assessment, and protective action recommendation. Source term estimation is almost the most difficult part among them. For example, bad communication, incomplete information, as well as complicated accident scenario make it hard to determine the reactor status and estimate the source term timely in the Fukushima accident. Subsequently, it leads to the hard decision on how to take appropriate emergency response actions. Hence, this paper aims to develop a method for rapid source term estimation to support nuclear emergency decision making in pressurized water reactor NPP. The method aims to make our knowledge on NPP provide better support nuclear emergency. Firstly, this paper studies how to build a Bayesian network model for the NPP based on professional knowledge and engineering knowledge. This paper presents a method transforming the PRA model (event trees and fault trees) into a corresponding Bayesian network model. To solve the problem that some physical phenomena which are modeled as pivotal events in level 2 PRA, cannot find sensors associated directly with their occurrence, a weighted assignment approach based on expert assessment is proposed in this paper. Secondly, the monitoring data of NPP are provided to the Bayesian network model, the real-time status of pivotal events and initiating events can be determined based on the junction tree algorithm. Thirdly, since PRA knowledge can link the accident sequences to the possible release categories, the proposed method is capable to find the most likely release category for the candidate accidents scenarios, namely the source term. The probabilities of possible accident sequences and the source term are calculated. Finally, the prototype software is checked against several sets of accident scenario data which are generated by the simulator of AP1000-NPP, including large loss of coolant accident, loss of main feedwater, main steam line break, and steam generator tube rupture. The results show that the proposed method for rapid source term estimation under nuclear emergency decision making is promising.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.833-837
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• 1998

This paper presents preliminary findings regarding a modeling framework under development for use in a multi-attribute decision model for advanced emergency operating procedures(EOPs). This model provides a means for optimal decision making strategy for advanced emergency operating procedures conceptualizing the dynamic coordination of responsibilities and information in the human system interactions with advanced reactor systems. For the purpose of evaluation of the applicability of this modeling framework, an empirical case study for a post-cooldown strategy during an steam generator tube rupture (SGTR) accident was carried out. As a result, it was found empirically that the multi-attribute decision model is a useful tool for establishing advanced EOPs that reduce the operator's cognitive and decision making burden during the accident mitigation process.

• Nuclear Engineering and Technology
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• v.44 no.6
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• pp.653-662
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• 2012

We evaluate the technical and organizational aspects of the severe accident management guideline (SAMG), focusing on the decision-making process in the technical support center (TSC). From the technical aspects, we conclude that the present SAMG is a good tool that can assist the TSC in efficiently managing probable severe accidents. However, we suggest that the clear separation of the emergency operating procedure (EOP) and SAMG, which shifts plant control from the main control room (MCR) to the TSC, might not be an effective framework from an organizational perspective. Studies on organizational behavior demonstrate that a group decision made under a risky situation might be polarized in either a risky or cautious way. We recognize that we cannot be free from the polarization effect since the current SAMG recommends that the TSC evaluate the advantages and disadvantages of strategies to be implemented and choose the best one based on a group decision process. Illustrative examples of accident management under risky conditions are recapitulated from previous studies of the authors and we propose that the SAMG should be more proceduralized to remove this polarization from the decision-making process.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.104-118
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• 2003

It has been criticized that conventional human reliability analysis (HRA) methodologies for probabilistic safety assessment (PSA) have been focused on the quantification of human error probability (HEP) without detailed analysis of human cognitive processes such as situation assessment or decision-making which are crticial to successful response to emergency situations. This paper introduces a new human reliability analysis (HRA) methodology, AGAPE-ET (A guidance And Procedure for Human Error Analysis for Emergency Tasks), focused on the qualitative error analysis of emergency tasks from the viewpoint of the performance of human cognitive function. The AGAPE-ET method is based on the simplified cognitive model and a taxonomy of influencing factors. By each cognitive function, error causes or error-likely situations have been identified considering the characteristics of the performance of each cognitive function and influencing mechanism of PIFs on the cognitive function. Then, overall human error analysis process is designed considering the cognitive demand of the required task. The application to an emergency task shows that the proposed method is useful to identify task vulnerabilities associated with the performance of emergency tasks.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.929-938
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• 2012

The Computerized Procedure System (CPS) is one of the primary operating support systems in the digital Main Control Room. The CPS displays procedure on the computer screen in the form of a flow chart, and displays plant operating information along with procedure instructions. It also supports operator decision making by providing a system decision. A procedure flow should be correct and reliable, as an error would lead to operator misjudgment and inadequate control. In this paper we present a modeling for the CPS that enables formal verification based on Petri nets. The proposed State Token Petri Nets (STPN) also support modeling of a procedure flow that has various interruptions by the operator, according to the plant condition. STPN modeling is compared with Coloured Petri net when they are applied to Emergency Operating Computerized Procedure. A converting program for Computerized Procedure (CP) to STPN has been also developed. The formal verification and validation methods of CP with STPN increase the safety of a nuclear power plant and provide digital quality assurance means that are needed when the role and function of the CPS is increasing.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.409-414
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• 1996

A model to estimate economic consequence of severe accident provides some measure of the impact on the accident and enables to know the different effects of the accident described as same terms of cost and combined as necessary. Techniques to assess the consequences of accidents in terms of cost have many applications, for instance in examining countermeasure options, as part of either emergency planning or decision making after an accident. In this study, a model to estimate the accident economic consequence is developed appropriate to our country focused on PWR accident costs from a societal viewpoint. Societal costs are estimated by accounting for losses that directly affect the plant licensee, the public, the nuclear industry, or the electric utility industry after PWR accident.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.770-780
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• 2022

In 1993 the University of Extremadura initiated the design, construction and management of the Radiological Alert Network of Extremadura (RAREx). The goal was to acquire reliable near-real-time information on the environmental radiological status in the surroundings of the Almaraz Nuclear Power Plant by measuring, mainly, the ambient dose equivalent. However, the phased development of this network has been carried out from two points of view. Firstly, there has been an increase in the number of stations comprising the network. Secondly, there has been an increase in the number of monitored parameters. As a consequence of the growth of RAREx network, large data volumes are daily generated. To face this big data paradigm, software applications have been developed and implemented in order to maintain the indispensable real-time and efficient performance of the alert network. In this paper, the description of the current status of RAREx network after 30 years of design and performance is showed. Also, the performance of the graphing software for daily assessment of the registered parameters and the automatic on real time warning notification system, which aid with the decision making process and analysis of values of possible radiological and non-radiological alterations, is briefly described in this paper.

• Journal of Radiation Protection and Research
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• v.13 no.2
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• pp.67-77
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• 1988

The necessity of developing a rapid dose assessment system has been emphasized for an effective emergency response of mitigation of off-site radiological consequences. A microcomputer program based on a rapid dose assessment model of the off-site radiological consequences is developed for various accdident sinarios for the Nuclear Power Plants in Korea. This model, which is consists of the user answering-question input format as a menu driven method and the output format of table and graphic types, is helpful to decision-making on Emergency Preparedness by being more rapidly able to implement the off-site dose assessment and to interpret the result.

• The Korean Journal of Nuclear Medicine
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• v.34 no.4
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• pp.366-369
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• 2000

We report a case of a patient with cystic subdural hygroma who underwent pre-operative Tc-99m DTPA cistrenoscintigraphy to determine the course of operation. A 68-year-old female was admitted to the department of neurosurgery because of acute subarachnoid hemorrhage. After emergency ventricular drainage, the hydrocephalus and cystic subdural hygroma in the right fronto-temporal area developed. She underwent Tc-99m DTPA cisternoscintigraphy to evaluate the type of hydrocephalus, which revealed obstructive communicating hydrocephalus and the communication between the subdural hygroma and the subarachnoid space. As a result of these findings, she underwent the ventriculo-peritoneal shunt operation without removal of the subdural hygroma. Post-operative brain CT showed nearly normalized shape and size of the right ventricle and disappearance of subdural hygroma. We recommend the pre-operative cisternoscintigraphy in patients with complex hygroma to evaluate the communication between subdural hygroma and the subarachnoid space.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2147-2155
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• 2022

Nuclear safety-related underground liquid storage tanks, such as those used to store fuel for emergency diesel generators, are critical components for safety of hundreds of existing nuclear power plants (NPP) worldwide. Since most of those NPP will continue to operate for decades, a beyond design base (BDB) seismic screening of safety-related underground tanks in those NPP is beneficial and essential to public safety. The analytical methodology for buried tank subjected to seismic effect, including a BDB seismic evaluation, needs to consider both soil-structure and fluid-structure interaction effects. Comprehensive analysis of such a soil-structure-fluid system is costly and time consuming, often subjected to availability of state-of-art finite element tools. Simple, but practically and reasonably accurate techniques for seismic evaluation of underground liquid storage tanks have not been established. In this study, a mechanics based solution is proposed for the evaluation of a cylindrical underground liquid storage tank using hand calculation methods. For validation, a practical example of two underground diesel fuel tanks in an existing nuclear power plant is presented and application of the proposed method is confirmed by using published results of the computer-aided System for Analysis of Soil Structural Interaction (SASSI). The proposed approach provides an easy to use tool for BDB seismic assessment prior to making decision of applying more costly technique by owner of the nuclear facility.