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• To validate the newly implemented FFR model in the SPACE code, the Halden IFA-650 test is calculated. • Overall prediction with the FFR model in SPACE is well matched with experimental results. • For some tests, the best estimated clad deformation model is necessary to validate the FFR model better. • Sensitivity analyses are conducted for fragmentation, packing fraction, and threshold gap to better understand the FFR model in SPACE. The new ECCS regulations were recently considered in South Korea. One of the major concerns in this revision is the consideration of fuel fragmentation, relocation, and dispersal (FFRD) phenomena during a loss of coolant accident (LOCA). In response, the FFR model was newly implemented in the SPACE code, which is a safety analysis code. The FFR model based on the QT model, which was developed by Quantum Technology Corporation, was developed with a threshold size of fuel fragments for fuel relocation, fuel power distribution, and so on. In this study, to validate the newly developed FFR model in SPACE code, calculations using Halden IFA-650 tests are conducted. Overall, the results show that the newly developed FFR model yields results that are consistent with experimental results in terms of fuel relocation and their effects on cladding temperature. However, when the cladding deformation is not well predicted, the fuel relocation prediction is poor. Thus, the cladding deformation is the most critical parameter for the FFR phenomena. In addition, for a fresh fuel condition, the threshold fragment size is additionally proposed in the fuel relocation model. For a better understanding of the FFR model behavior during a LOCA, some sensitivity tests for major FFR model parameters are conducted. This can give valuable information to develop FFR modeling in safety analysis methodology. [ABSTRACT FROM AUTHOR]

In this study, the spatio-temporal characteristics of the minimum rest time for the safety of South Korean outdoor workers during hot summer months (June to August) are examined based on the hourly wet-bulb globe temperature (WBGT) across 27 weather stations in South Korea. The WBGT thresholds in the work-rest recommendation of the Korea Occupational Safety and Health Agency (KOSHA 2017) for the quantification of the minimum rest time are evaluated through a comparison of the given thresholds with the occurrences of occupational heat-related illness patients due to outdoor work during hot summer months in South Korea. The long-term (2009–2018) average of the hourly WBGT values during summer months shows that outdoor workers with a moderate workload are exposed to heat stress during approximately 30% of the entire daytime working hours (06:00–18:00). According to the WBGT thresholds modified from the KOSHA (2017) guidelines, the daily minimum rest time for a moderate workload noticeably increases up to 18% (11 min/h) in mid-summer (late July and early August). During mid-summer, the minimum rest time for a continuous moderate outdoor workload even increases up to 31% (18 min/h) between 12:00 and 13:00 and is regionally higher in the southwestern than in the southeastern regions of the Korean Peninsula. These results suggest that in summertime high-heat environments, a mandatory rest time must be provided according to appropriate heat management programs for the safety of workers. [ABSTRACT FROM AUTHOR]

The metal water reaction between the fuel clad and the coolant has been deemed important to safety analyses for transients for several decades. A Loss-of-coolant accident would cause the overheating of fuel clad which might involve a vigorously exothermic chemical reaction. The zirconium is widely used as a clad material and the element reacts remarkably with steam at high temperature of above 1000 K. The results of this reaction are the heat generation of level of fuel decay power, oxidized metal, and hydrogen generation. The system transient analysis code SPACE (Safety and Performance Analysis Code) which has been developed at the Korea nuclear industry has the correlation set modeling the metal-water oxidation, but the hydrogen generated by the reaction is not considered in the governing equations of the code. The governing equations were modified to model the hydrogen influx and steam extinction due to the reaction. The verification calculations for the code modification were performed using two conceptual problems. First, the modification of governing equations about the steam extinction corresponding to an inflow of hydrogen gas was reviewed by the forced hydrogen injection without a fuel model. Second, the hydrogen generation and temperature excursion due to the reaction were examined by the simulation of fuel without a nuclear heat source to investigate the validity of the redistribution of the reaction heat. Finally, the hypothetical accident of LBLOCA (Large break loss-of-coolant-accident) for the APR-1400 and the LOFT L2-5 test were calculated for a comparison with the calculation results by the original and modified codes. [ABSTRACT FROM AUTHOR]

This study assessed the potential impact of heat stress on labor productivity in South Korea; as such, stress is expected to increase due to climate change. To quantify the future loss of labor productivity, we used the relationship between the wet-bulb globe temperature and work-rest cycles with representative concentration pathways (RCPs) 4.5 and 8.5 as the climate change scenarios. If only climate factors are considered, then future labor productivity is expected to decline in most regions from the middle of the twenty-first century onwards (2041-2070). From the late twenty-first century onwards, the productivity of heavy outdoor work could decline by 26.1% from current levels under the RCP 8.5 climate scenario. Further analysis showed that regional differences in labor characteristics and the working population had noteworthy impacts on future labor productivity losses. The heat stress caused by climate change thus has a potentially substantial negative impact on outdoor labor productivity in South Korea. [ABSTRACT FROM AUTHOR]

Objective. Although endoscopic treatment for early gastric cancer (EGC) is an accepted therapy in South Korea and Japan, long-term outcomes remain unknown. We evaluated the clinical outcome of endoscopic submucosal dissection (ESD) for gastric dysplasia and EGC. Material and methods. A total of 402 patients with gastric dysplasia and EGC were treated with ESD at a single hospital from January 2004 to December 2007. The patients underwent ESD and then received periodic endoscopic follow-up and metastatic surveys for 9--49 months (median 30 months). Resectability (en bloc or piecemeal resection), curability (complete or incomplete), local recurrence, and disease-free survival rates were estimated. Results. There were 107 patients with low-grade dysplasia (LGD), 97 with high-grade dysplasia (HGD) and 198 with EGC. In EGC patients, en bloc resection was achieved in 89.7% (177/198), the complete resection rate was 87.9% (174/198), and the local recurrence rate was 5.1% (10/198). Tumor size >20 mm was significantly associated with local recurrence (odds ratio 6.45; 95% CI 1.20--20.11; p=0.001). There were significant correlations between the incidences of a piecemeal or incomplete resection and that of local recurrence (odds ratio 5.23; 95% CI 1.02--18.34; p=0.001; and odds ratio 6.99; 95% CI 1.22--21.65; p=0.002, respectively). The 3-year cancer-free survival rate was 94.9%. Conclusions. Curative treatment with successful en bloc resection can reduce the local recurrence of gastric neoplastic lesions after ESD. Clinical outcome may be excellent, although longer follow-up studies are warranted. [ABSTRACT FROM AUTHOR]

Abstract: Fetal and maternal exposure levels of two emerging pollutants, polybrominated diephenyl ethers (PBDEs) and synthetic musks, were measured in Korean general population to assess prenatal and postnatal exposures in infants. For this purpose, paired samples of breast milk, maternal and cord blood were collected from 20 Korean women in 2007. In comparison to data from other countries and previous data from Korea, relatively higher and gradually increasing concentrations for PBDEs were found in Korean breast milk (

• A PIRT process is performed for an open-tank-in-pool research reactor. • The process includes the most commonly postulated events of research reactors. • The process is intended to extend the SPACE applicability to the research reactors. • A preliminary data set for V&V are proposed for code assessment. • Proposal on further research is given to increase knowledge levels of the RRs. The benefits of research reactor technology are always essentially accompanied by nuclear safety, which is ensured by a series of supporting analysis such as safety analysis. In order to extend the applicability of the Safety and Performance Analyzing Code (SPACE code) to safety analysis of typical open-tank-in-pool type research reactors using plate-type fuels, a Phenomena Identification and Ranking process was performed for most of the relevant internal event scenarios of a reference research reactor, i.e., the KiJang Research Reactor, designed and under development by the Korea Atomic Energy Research Institute (KAERI). The Structures, Systems, and Components (SSCs) important to nuclear safety of the reactor were included in the PIR processes. A summary of important results from the PIRT study on the research reactors is presented with a proposal on a preliminary set of data bases for a validation and verification matrix in addition to research issues. [ABSTRACT FROM AUTHOR]