• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.66-68
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• 2007

The regulatory guide, RG-1.204 and its underlying or confirmatory research, NUREG/CR-6866 were studied for Korean application to LPGS of NPPs. However they excluded the application to that of NPPs. So US-NRC approved selectively industrial standards to that of NPPs on Nov 2005. It is necessary to understand the basis of regulatory technology related regulatory positions on LPGS and important to implement the guidance on LPGS as a resonable standard. The paper is examined what and how state of the art of relevant technology applied to the LPGS as well as the trip-out events related to electrical system were involved with LPGS. We reviewed the relevant standards applicable to Korean NPPs. Following are concluded to recommend. (1) IEEE 510-1050 is recommended as a guide for I&C grounding against EMI and lighting transients (2) IEEE Std-665, 510-666, Std-C62.23 for electrical grounding against voltage surges and lighting transients (3) Inspection should be thoroughly be implemented a frequency of 3-5 year period according to NFPA780 or KSC-IEC 61024.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1372-1386
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• 2018

Despite recent advances in multi-hazard analysis, the complexity and inherent nature of such problems make quantification of the landslide effect in a probabilistic safety assessment (PSA) of NPPs challenging. Therefore, in this paper, a practical approach was presented for performing an earthquake-induced landslide PSA for NPPs subject to seismic hazard. To demonstrate the effectiveness of the proposed approach, it was applied to Korean typical NPP in Korea as a numerical example. The assessment result revealed the quantitative probabilistic effects of peripheral slope failure and subsequent run-out effect on the risk of core damage frequency (CDF) of a NPP during the earthquake event. Parametric studies were conducted to demonstrate how parameters for slope, and physical relation between the slope and NPP, changed the CDF risk of the NPP. Finally, based on these results, the effective strategies were suggested to mitigate the CDF risk to the NPP resulting from the vulnerabilities inherent in adjacent slopes. The proposed approach can be expected to provide an effective framework for performing the earthquake-induced landslide PSA and decision support to increase NPP safety.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.866-878
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• 2021

Procedures play a key role in ensuring safe operation at nuclear power plants (NPPs). Development and maintenance of a large number of procedures reflecting the best knowledge available in all relevant areas is a complex job. This paper introduces a newly developed methodology and the implemented software, called iExtractor, for the extraction of syntactic and semantic information from NPP procedures utilizing natural language processing (NLP)-based technologies. The steps of the iExtractor integrated with sets of rules and an ontology for NPPs are described in detail with examples. Case study results of the iExtractor applied to selected procedures of a U.S. commercial NPP are also introduced. It is shown that the iExtractor can provide overall comprehension of the analyzed procedures and indicate parts of procedures that need improvement. The rich information extracted from procedures could be further utilized as a basis for their enhanced management.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.8-22
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• 1999

This study was performed to comparatively evaluate selected Human Reliability Analysis (HRA) methods which mainly focus on cognitive error analysis, and to derive the requirement of a new human error analysis (HEA) framework for Accident Management (AM) in Nuclear Power Plants (NPPs). In order to achieve this goal, we carried out a case study of human error analysis on an AM task in NPPs. In the study we evaluated three cognitive HEA methods, HRMS, CREAM and PHECA, which were selected through the review of the currently available seven cognitive HEA methods. The task of reactor cavity flooding was chosen for the application study as one of typical tasks of AM in NPPs. From the study, we derived seven requirement items for a new HEA method of AM in NPPs. We could also evaluate the applicability of three cognitive HEA methods to AM tasks. CREAM is considered to be more appropriate than others for the analysis of AM tasks, HRMS is also applicable to the error analysis of AM tasks. But, PHECA is regarded less appropriate for the predictive HEA technique as well as for the analysis of AM tasks. In addition to these, the advantages and disadvantagesofeachmethodaredescribed.

• Fire Science and Engineering
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• v.32 no.6
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• pp.141-149
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• 2018

The perception of risk that firefighters have is closely related to their performance and emergency preparedness in nuclear power plant accidents. This study investigated the unique risk perception among firefighters working in nuclear power plants (NPPs) using a concept mapping method. Thirty three firefighters in NPPs participated in this study. Two core axes, "fear and control" and "coping resource", emerged in the firefighters' risk perception. In particular, the risk perception consisted of six clusters: fear of radiation exposure and low controllability; anxiety caused by the lack of control and authority; lack of trust and cooperation; lack of authority and professionals; lack of equipment, manual, and information; and lack of knowledge and training. Catastrophic expectation and a low sense of control caused by the lack of responsive resources were the main factors that increase the risk perception. The theoretical and practical contributions of this study were discussed.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.211-221
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• 2020

One fundamental element of probabilistic safety assessment (PSA) is the initiating event (IE) analysis. Since IE frequencies can change over time, time-trend analysis is required to obtain optimized IE frequencies. Accordingly, such time-trend analyses have been employed to estimate industry-average IE frequencies for use in the PSAs of U.S. nuclear power plants (NPPs); existing PSAs of Korean NPPs, however, neglect such analysis in the estimation of IE frequencies. This article therefore provides the method for and results of estimating Korean industry-average IE frequencies using time-trend analysis. It also examines the effects of the IE frequencies obtained from this study on risk insights by applying them to recently updated internal events Level 1 PSA models (at-power and shutdown) for an OPR-1000 plant. As a result, at-power core damage frequency decreased while shutdown core damage frequency increased, with the related contributions from each IE category changing accordingly. These results imply that the incorporation of time-trend analysis leads to different IE frequencies and resulting risk insights. The IE frequency distributions presented in this study can be used in future PSA updates for Korean NPPs, and should be further updated themselves by adding more recent data.

• Journal of the Ergonomics Society of Korea
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• v.32 no.1
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• pp.37-45
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• 2013

Objective: This study describes the change of operator performance in drastic change of illumination level, and proposes an alternative method to cope with it. Background: The control standard of illumination for nuclear power plants(NPPs) is based on the set of limit criteria for maintaining a specific illumination level. However, there is a possibility to cause human errors according to the psychological and physiological influences to operators in the situation of drastic change of illumination such as SBO(Station Black Out), so a basic study is necessary to review the current approach. Method: We assessed the visual fatigue, subjective work load and task performance according to the three illumination situations(Normal Illumination, Emergency Illumination, and Drastic Change of Illumination). Result: Research finding shows that there are not significant differences in task performance between normal illumination (1,000lx level) and emergency illumination (100lx level), only if beyond the dark adaptation limit. However, subjective work load on mental demand and visual fatigue show a potential challenge to visual performance in drastic change of illumination. Conclusion/Application: Several trials can complement this challenge in NPPs by applying 3-way communication, enhancing readability of procedures, and managing the visual factors affecting the operators' performance through a Visual Environment Management Program including visual health aspects, etc.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1176-1179
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• 2019

Measurements of activity concentrations of radionuclides in atmospheric releases were performed in 2017-2018 at vent stacks of seven Russian nuclear power plants. The selected instruments and research methods, with detection limits significantly lower than the existing detection limit of Russian NPPs routine control, allowed to reliably determine up to 26 radionuclides. Analysis of experimental data allows to determine the list of radionuclides for calculation the effective dose rates to public and the permissible annual discharge levels for each Russian NPP. Radiocarbon is determined as major contributor for the dose from the atmospheric releases of LWGR reactors - up to 98% for EGP-6 and RBMK-1000 (Smolensk NPP) reactors. For PWR reactors (VVER) radionuclides contribution to the annual dose from atmospheric releases is more complicated, but, in general, dose is formed by tritium, $^{14}C$ and noble gases. The special monitoring results with ranking of measured radionuclides according to their contribution to the effective dose makes it possible to optimize the list of controlled radionuclides in airborne releases of Russian NPPs from 94 to 8-16 for different NPPs.

• Journal of the Ergonomics Society of Korea
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• v.34 no.1
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• pp.29-43
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• 2015

Objective: The aim of this study is to develop management guidelines and a procedure for an anthropometric suitability assessment of the main control room (MCR) in nuclear power plants (NPPs). Background: The condition of the MCR should be suitable for the work crews in NPPs. The suitability of the MCR depends closely on the anthropometric dimensions and ergonomic factors of the users. In particular, the MCR workspace design in NPPs is important due to the close relationship with operating crews and their work failures. Many documents and criteria have recommended that anthropometry dimensions and their studies are one of the foremost processes of the MCR design in NPPs. If these factors are not properly considered, users can feel burdened about their work and the human errors that might occur. Method: The procedure for the anthropometric suitability assessment consists of 5 phases: 1) selection of the anthropometric suitability evaluation dimensions, 2) establishment of a measurement method according to the evaluation dimensions, 3) establishment of criteria for suitability evaluation dimensions, 4) establishment of rating scale and improvement methods according to the evaluation dimensions, and 5) assessment of the final grade for evaluation dimensions. The management guidelines for an anthropometric suitability assessment were completed using 10 factors: 1) director, 2) subject, 3) evaluation period, 4) measurement method and criteria, 5) selection of equipment, 6) measurement and evaluation, 7) suitability evaluation, 8) data sharing, 9) data storage, and 10) management according to the suitability grade. Results: We propose a set of 17 anthropometric dimensions for the size, cognition/perception action/behavior, and their relationships with human errors regarding the MCR design variables through a case study. The 17 selected dimensions are height, sitting height, eye height from floor, eye height above seat, arm length, functional reach, extended functional reach, radius reach, visual field, peripheral perception, hyperopia/myopia/astigmatism, color blindness, auditory acuity, finger dexterity, hand function, body angle, and manual muscle test. We proposed criteria on these 17 anthropometric dimensions for a suitability evaluation and suggested an improvement method according to the evaluation dimensions. Conclusion: The results of this study can improve the human performance of the crew in an MCR. These management guidelines and a procedure for an anthropometric suitability assessment will be able to prevent human errors due to inadequate anthropometric dimensions. Application: The proposed set of anthropometric dimensions can be integrated into a managerial index for the anthropometric suitability of the operating crews for more careful countermeasures to human errors in NPPs.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.723-730
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• 2019

Acquiring instrumentation signals generated from nuclear power plants (NPPs) is essential to maintain nuclear reactor integrity or to mitigate an abnormal state under normal operating conditions or severe accident circumstances. However, various safety-critical instrumentation signals from NPPs cannot be accurately measured on account of instrument degradation or failure under severe accident circumstances. Reactor vessel (RV) water level, which is an accident monitoring variable directly related to reactor cooling and prevention of core exposure, was predicted by applying a few signals to deep neural networks (DNNs) during severe accidents in NPPs. Signal data were obtained by simulating the postulated loss-of-coolant accidents at hot- and cold-legs, and steam generator tube rupture using modular accident analysis program code as actual NPP accidents rarely happen. To optimize the DNN model for RV water level prediction, a genetic algorithm was used to select the numbers of hidden layers and nodes. The proposed DNN model had a small root mean square error for RV water level prediction, and performed better than the cascaded fuzzy neural network model of the previous study. Consequently, the DNN model is considered to perform well enough to provide supporting information on the RV water level to operators.