• Nuclear Engineering and Technology
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• 제31권1호
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• pp.68-79
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• 1999

The YGN Units 3&4 plant conditions during shutdown operation were reviewed to identify the possible event scenarios following the loss of shutdown cooling (SDC) event. For the five cases of typical reactor coolant system (RCS) configurations under the worst event sequence, such as unavailable secondary cooling and no RCS inventory makeup, the thermal hydraulic analyses were performed using the RELAP5/MOD3.2 code to investigate the plant behavior following the event. The thermal hydraulic analyses include the estimation of time to boil, time to core uncovery, and time to core heat up to determine the containment closure time to prevent the uncontrolled release of fission products to atmosphere. The result indicates that the containment closure is recommended to be achieved within 42 minutes after the loss of SDC for the steam generator (SG) inlet plenum manway open case or the large cold leg open case under the worst event sequence. The containment closure time is significantly dependent on the elevation and size of the opening and the SG secondary water level condition. It is also found that the containment closure needs to be initiated before the boiling time to ensure the survivability of the workers in the containment. These results will provide useful information to operators to cope with the loss of SDC event.

• Safety and Health at Work
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• 제9권2호
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• pp.210-215
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• 2018

Background: The aims of this study were to determine the extent of workplace bullying perceptions among the employees of a Faculty of Medicine, evaluating the variables considered to be associated, and determining the effect of workplace bullying perceptions on their psychological symptoms evaluated by the Brief Symptom Inventory (BSI). Methods: This cross-sectional study was performed involving 355 (88.75%) employees. Results: Levels of perceived workplace bullying were found to increase with the increasing scores for BSI and BSI sub-dimensions of anxiety, depression, negative self, somatization, and hostility (all p < 0.001). One point increase in the workplace bullying perception score was associated with a 0.47 point increase in psychological symptoms evaluated by BSI. Moreover, the workplace bullying perception scores were most strongly affected by the scores of anxiety, negative self, depression, hostility, and somatization (all p < 0.05). Conclusion: The present results revealed that young individuals, divorced individuals, faculty members, and individuals with a chronic disease had the greatest workplace bullying perceptions with our study population. Additionally, the BSI, anxiety, depression, negative self, somatization, and hostility scores of the individuals with high levels of workplace bullying perceptions were also high.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.815-819
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• 2018

In this study, criticality safety assessments of the potential for storing transuranic element (TRU) ingots via a pyroprocess were evaluated to determine the appropriate TRU storage design parameters, in this case the ratio of the TRU ingot height to the radius and the number of TRU ingot canisters stacked within a container. Various accident situations were modeled over a modeling period of 5 years for a cumulative inventory of TRU ingots with various water densities in submerged containers and with various pitches between the containers in the facility. Under these combinations, we calculated the threshold of TRU height and radius ratio depending on the number of canisters in a container to keep the stored TRU in a subcritical state. The ratio of the TRU ingot height to radius should not exceed 4.5, 1.1, 0.5, 0.3, and 0.2 for two, three, four, five, and six levels of stacked canisters in a container, respectively.

• Safety and Health at Work
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• 제13권2호
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• pp.201-206
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• 2022

Background: The present objective was to verify whether burnout (emotional exhaustion [EE], depersonalization [DP] and low professional efficacy [PE]) is a risk factor for long-term sickness absence (LTSA; 30 consecutive days) from the teaching role. Methods: This was a prospective cohort study with two years of follow-up that investigated 509 elementary and high-school teachers. Burnout was identified by Maslach Burnout Inventory. Poisson regression with robust variance was used to adjust for possible confounders. Results: The incidence of LTSA was 9.4%. High EE levels were associated with LTSA in the crude analysis, but the association lost statistical significance after adjustments (for sex, age, perception of work-life balance, general self-rated health, chronic pain and depression). High DP levels were associated with this outcome, even after all adjustments (relative risk = 1.80; 95% confidence interval: 1.05-3.09). Low PE levels were not related to LTSA. Conclusion: The results reinforce the need to improve teachers' work conditions to reduce burnout, particularly DP, and its consequences.

• 한국유체기계학회 논문집
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• 제17권6호
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• pp.104-108
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• 2014

The recent Fukushima nuclear power plant accidents shows that the core make up at high RCS pressure condition is very important to prevent core melting. The core make up flow at high pressure condition should be driven by gravity force or passive forces because the AC-powered safety features are not available during a Station Black Out (SBO) accident. The reactor Coolant System (RCS) mass inventory is continuously decreased by releasing steam through the pressurizer safety valves after reactor trip during a SBO accident. The core will be melted down within 2~3 hours without core make up action by active or passive mode. In the new design concept of a Hybrid Safety Injection Tank (Hybrid SIT) both for low and high RCS pressure conditions, the low pressure nitrogen gas serves as a charging pressure for a LBLOCA injection mode, while the PZR high pressure steam provides an equalizing pressure for a high pressure injection mode such as a SBO accident. After the pressure equalizing process by battery driven initiation valve at a high pressure SBO condition, the Hybrid SIT injection water will be passively injected into the reactor downcomer by gravity head. The SBO simulation by MARS code show that the core makeup injection flow through the Hybrid SIT continued up to the SIT empty condition, and the core heatup is delayed as much.

• Nuclear Engineering and Technology
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• 제41권1호
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• pp.53-62
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• 2009

A set of experiments has been conducted on the performance sensitivity of the passive residual heat removal system (PRHRS) for an advanced integral type reactor, SMART, by using a high temperature and high pressure thermal-hydraulic test facility, the VISTA facility. In this paper the effects of the opening delay of the PRHRS bypass valves and the closing delay of the secondary system isolation valves, and the initial water level and the initial pressure of the compensating tank (CT) are investigated. During the reference test a stable flow occurs in a natural circulation loop that is composed of a steam generator secondary side, a secondary system, and a PRHRS; this is ascertained by a repetition test. When the PRHRS bypass valves are operated 10 seconds later than the secondary system isolation valves, the primary system is not properly cooled. When the secondary system isolation valves are operated 10 or 30 seconds later than the PRHRS bypass valves, the primary system is effectively cooled but the inventory of the PRHRS CT is drained earlier. As the initial water level of the CT is lowered to 16% of the full water level, the water is quickly drained and then nitrogen gas is introduced into the PRHRS, resulting in the deterioration of the PRHRS performance. When the initial pressure of the PRHRS is at 0.1MPa, the natural circulation is not performed properly. When the initial pressures of the PRHRS are 2.5 or 3.5 MPa, they show better performance than did the reference test.

• Journal of Radiation Protection and Research
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• 제28권2호
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• pp.109-116
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• 2003

본 연구에서는 최근 국내 원자력발전소의 해체시 방사화 생성물 재고량의 평가 필요성이 대두됨에 따라 원자로 수명종로가 가까워지고 있는 고리1호기를 대상으로 원자로 각 구조물의 방사라 생성물 재고량을 ANISN과 ORIGEN2 코드를 이용하여 예비평가를 수행하였다. 코드 입력자료로는 노심에서부터 차폐콘크리트까지 반경방향으로 8개 영역으로 나누어 ANISN 코드를 사용하여 중성자속을 계산하였다. 또한 압력용기의 중성자속 분포를 가지고 주요 핵종의 단일 그룹 반응단면 적을 보정하였다. 본 연구의 결과 압력용기의 경우 원자로 정지시점에서 약 10년까지는 $^{55}Fe,\;^{59}Ni,\;^{63}Ni,\;^{60}Co$ 핵종이 총 방사능의 약 95%정도를 차지하였으며, 약 50년 이상 냉각 후의 총 방사능은 원자로 정지시점과 비교하여 약 0.2 % 이하로 감소하는 것으로 평가되었다. 또한 압력용기의 무게가 210 ton임을 고려해 볼 때, 압력용기의 총 방사화생성물 재고량은 $5.25{\times}10^6GBq$로 계산되었다. 또한 차폐콘크리트의 경우 약 10년 이상 냉각 후의 총 방사능은 원자로 정지시점과 비교하여 1 %이하로 급격히 감소하는 것으로 평가되었다.

• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3236-3246
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• 2021

Lessons learned from the Fukushima Daiichi nuclear power plant accident directed that multiple failures should be considered more seriously rather than single failure in the licensing bases and safety cases because attempts to take accident management measures could be unsuccessful under the high radiation environment aggravated by multiple failures, such as complete loss of electric power, uncontrollable loss of coolant inventory, failure of essential safety function recovery. In the case of the complete loss of electric power called station blackout (SBO), if there is no mitigation action for recovering safety functions, the reactor core would be overheated, and severe fuel damage could be anticipated due to the failure of the active heat sink. In such a transient condition at CANDU-6 plants, the seal failure of the primary heat transport (PHT) pumps can facilitate a consequent increase in the fuel sheath temperature and eventually lead to degradation of the fuel integrity. Therefore, it is necessary to specify the regulatory guidelines for multiple failures on a licensing basis so that licensees should prepare the accident management measures to prevent or mitigate accident conditions. In order to explore the efficiency of implementing accident management strategies for CANDU-6 plants, this study proposed a realistic accident analysis approach on the SBO transient with multiple-failure sequences such as seal failure of PHT pumps without operator's recovery actions. In this regard, a comparative study for two PHT pump seal failure modes with and without coolant seal leakage was conducted using a best-estimate code to precisely investigate the behaviors of thermal-hydraulic parameters during transient conditions. Moreover, a sensitivity analysis for different PHT pump seal leakage rates was also carried out to examine the effect of leakage rate on the system responses. This study is expected to provide the technical bases to the accident management strategy for unmitigated transient conditions with multiple failures.

• Korean Journal of Acupuncture
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• 제28권3호
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• pp.151-163
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• 2011

Objectives : Our aim is to evaluate feasibility for massive clinical research and to make basic analysis of efficacy and safety of acupuncture treatment for chronic fatigue syndrome and idiopathic chronic fatigue. Methods : This study is a protocol for a pilot randomized controlled trial. It was developed through literature searches and discussions among researchers. Results : Forty participants allocated to acupuncture group and wait-list group. Participants allocated to acupuncture group will be treated three times per week for a total of 12 sessions over four weeks. Eight points (GV20; bilatral GB20, BL11, BL13, BL15, BL18, BL20, BL23) have been selected for the acupuncture group. Participants in the wait-list group will not receive acupuncture treatment during study period and follow-up will be made in the 5th and 9th weeks after random allocation. Then the same acupuncture treatment as that performed to the acupuncture group will be made to the wait-list group. Fatigue Severity Scale, a short form of Stress Response Inventory, Beck Depression Inventory, and Insomnia Severity Index will be used as outcome variables to evaluate the efficacy of acupuncture. Safety will be assessed at every visit. Conclusions : The trial based on this study will be performed. The results of the trial will provide basis for the efficacy and safety of acupuncture treatment for chronic fatigue syndrome and idiopathic chronic fatigue.

• 한국대기환경학회지
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• 제33권5호
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• pp.497-514
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• 2017

This study quantitatively analyzes the effects of emission inventory choices on the simulated particulate matter (PM) concentrations and the domestic/foreign contributions in the Seoul Metropolitan Area (SMA) with an air quality forecasting system. The forecasting system is composed of Weather Research and Forecasting (WRF)-Sparse Matrix Operator Kernel Emissions (SMOKE)-Community Multi-Scale Air Quality (CMAQ). Different domestic and foreign emission inventories were selectively adopted to set up four sets of emissions inputs for air quality simulations in this study. All modeling cases showed that model performance statistics satisfied the criteria levels (correlation coefficient >0.7, fractional error <50%) suggested by previous studies. Notwithstanding the apparently good model performance of total PM concentrations by all emission cases, annual average concentrations of simulated total PM concentrations varied up to $20{\mu}g/m^3$ (160%) depending on the combination of emission inventories. In detail, the difference in simulated annual average concentrations of the primary PM coarse (PMC) was up to $25.2{\mu}g/m^3$ (6.5 times) compared with other cases. Furthermore, model performance analyses on PM species showed that the difference in the simulated primary PMC led to gross model overestimation in general, which indicates that the primary PMC emissions need to be improved. The contribution analysis using model direct outputs indicated that the domestic contributions to the annual average PM concentrations in the SMA vary from 44% to 67%. To account for the uncertainty of the simulated concentration, the contribution correction factor method proposed by Bae et al. (2017) was applied, which resulted in converged contributions(from 48% to 57%). We believe this study shows that it is necessary to improve the simulated concentrations of PM components in order to enhance the accuracy of the forecasting model. It is deemed that these improvements will provide more accurate contribution results.