Hazard analysis of typhoon-related external events using extreme value theory

AbstractBackgroundAfter the Fukushima accident, the importance of hazard analysis for extreme external events was raised.MethodsTo analyze typhoon-induced hazards, which are one of the significant disasters of East Asian countries, a statistical analysis using the extreme value theory, which is a method for estimating the annual exceedance frequency of a rare event, was conducted for an estimation of the occurrence intervals or hazard levels. For the four meteorological variables, maximum wind speed, instantaneous wind speed, hourly precipitation, and daily precipitation, the parameters of the predictive extreme value theory models were estimated.ResultsThe 100-year return levels for each variable were predicted using the developed models and compared with previously reported values. It was also found that there exist significant long-term climate changes of wind speed and precipitation.ConclusionA fragility analysis should be conducted to ensure the safety levels of a nuclear power plant for high levels of wind speed and precipitation, which exceed the results of a previous analysis

Polaribacter lacunae sp. nov., isolated from a lagoon

An aerobic, Gram-stain-negative, rod-shaped bacterium, designated strain HMF2268T, was isolated from a lagoon in the Republic of Korea. Comparative 16S rRNA gene sequence analysis showed that strain HMF2268T belonged to the genus Polaribacter and was most closely related to Polaribacter huanghezhanensis SM1202T (96.8 % similarity). Cellular fatty acids were dominated by iso-C15 : 0, iso-C15 : 0 3-OH, anteiso-C15 : 0 and iso-C15 : 1 G. The predominant respiratory quinone was menaquinone-6 (MK-6). The major polar lipids were phosphatidylethanolamine, three unidentified aminolipids and two unidentified polar lipids. The DNA G+C content was 34.3 mol%. Based on the polyphasic taxonomic analyses, it is concluded that strain HMF2268T represents a novel species of the genus Polaribacter , for which the name Polaribacter lacunae sp. nov. is proposed. The type strain is HMF2268T (=KCTC 42191T=CECT 8862T)

A Guideline to HRA Data Collection from Simulations

Including the Fukushima disaster, most accidents that have occurred for several decades in nuclear power plants (NPPs) commonly pointed out the criticality of an inappropriate human performance to their operational safety. Consequently, a huge amount of effort has been spent to reduce the possibility of critical human errors that probably contribute to the safety of NPPs, and one of the most disseminated approaches is to conduct an HRA (Human Reliability Analysis). Unfortunately, although HRA practitioners generally require a lot of information pertaining to the comprehension of contexts being exposed to human operators, one of the frequently raised problems is a lack of available information. For this reason, KAERI (Korea Atomic Energy Research Institute) issued a standardized guideline that can be applied to clarify how to systematically collect HRA data in the full-scope simulator of NPPs. To this end, through the review of existing documents that specify (or suggest) required data items for supporting HRA practitioners, a total 89 generic HRA data items are identified. After that, a detailed data collection guideline that allows us to distinguish collectable HRA data items with the associated fact-based measurements (i.e., direct observables and objective surrogates) is proposed. In addition, in order to demonstrate the role of the proposed guideline, a couple of worksheets that are helpful for collecting HRA data from simulations in a systematic way are designed based on simulation records gathered from the requalification training sessions of domestic NPPs. As a result, although several pending problems still exist, it is possible to expect that fact-based HRA data can be secured from simulations, which will be useful for HRA practitioners to reduce the uncertainty (or subjectivity) of HRA results