• Nuclear Engineering and Technology
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• 제56권3호
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• pp.886-892
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• 2024

The cladding temperatures and axial mass distribution computed by MAAP5 were compared with their measured values in the test bundle of the Phebus Test FPT0. The computed cladding temperatures were in good agreed with the measured values in the pre-transient phase. In the transient heat-up phase, the computed temperatures were overestimated by the Baker-Just correlation in MAAP5, but the computed temperatures could simulate the subsequently measured values. The computed mass distribution in the axial direction was in qualitative agreement with the measured one for post-test fuel damage observations. The calculated flow areas of inner and outer regions in the test bundle were compared with the photographic observations. MAAP5 computed them at the height of 0.2 m where the molten pool formed was in qualitative agreement with the photographic observations. It was found that the remaining steam flow paths might be caused by the gas-liquid two-phase flow counter-current flow limitation.

• 한국안전학회지
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• 제27권5호
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• pp.229-234
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• 2012

Operator's action time is evaluated from MAAP4 analysis used in conventional probabilistic safety assessment(PSA) of a nuclear power plant. MAAP4 code which was developed for severe accident analysis is too conservative to perform a realistic PSA. A best-estimate code such as RELAP5/MOD3, MARS has been used to reduce the conservatism of thermal hydraulic analysis. In this study, operator's action time of core cooling recovery operation is evaluated by using the MARS code, which its Fussell-Vessely(F-V) value was evaluated as highly important in a small break loss of coolant(SBLOCA) event and loss of component cooling water(LOCCW) event in previous PSA. The main conclusions were elicited : (1) MARS analysis provides larger time window for operator's action time than MAAP4 analysis and gives the more realistic time window in PSA (2) Sufficient operator's action time can reduce human error probability and core damage frequency in PSA.

• Nuclear Engineering and Technology
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• 제56권11호
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• pp.4880-4886
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• 2024

The approach for determining the break size of recirculation loops in a multiple-loop power plant in the event of a loss of coolant accident (LOCA) is presented in this study. In this study, the MAAP5 simulation program was used. An approach to measuring the size of a crack or break in the cooling system is the temperature difference between the recirculation loops. This method does not require any additional facilities; it compares the temperatures of the cooling loops to determine which one has a rupture. The best data source was the loop monitoring system, which sends temperature data for analysis to the main control room. A real operating power reactor training simulator and the FSAR are applied to evaluate MAAP5, the methodology's engine. The results of the MAAP5 simulation code were consistent with those of the power plant simulator. Therefore, MAAP5 could produce enough analytical data to create the relationship diagram between temperature difference and break size. The study hypothesized that there exists a maximum value of temperature difference corresponding to each break size and suggested that applying the absolute maximum temperature difference can aid in identifying the break size. This approach proposes an assistive method for determining the size of a fracture or break in the recirculation system by leveraging the temperature difference between each loop. This approach eliminates the need for additional facilities, as temperature data from the recirculation loops can be transmitted to the main control room. After the reactor scram, operators can monitor the maximum temperature differences at the inlet to estimate the break size. Although the fitting curve used to preliminary estimate the Large Break Loss of Coolant Accident break size may overestimate the break size, it still provides valuable insights. This novel tool offers a rapid and comprehensive method for detecting LOCA events in the recirculation loops.

• 방사선산업학회지
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• 제18권3호
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• pp.217-221
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• 2024

This study aims to evaluate the radiation dose received by workers within the auxiliary building of the Saeul Units 1 and 2 during a severe accident. To achieve this, representative accident scenarios were selected, and operator actions required by the severe accident management guidelines were derived to present a methodology for dose assessment. The study utilized MAAP5.06 to analyze severe accidents and employed MAAP DOSE to evaluate worker radiation exposure. Among the three operator actions considered, the direct spray action on the reactor building outer wall-side penetration resulted in the highest estimated radiation dose. This is likely because the workers are deployed near the reactor building penetration, exposing them to higher radiation levels. Future plans include the optimization of dose performance by comparing these findings with evaluations conducted using MCNP, and the development of a data-driven ALARA decision support system for predicting and diagnosing radiation exposure on nuclear sites to ensure worker safety during severe accidents.

• 대한기계학회논문집B
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• 제38권1호
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• pp.17-24
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• 2014

본 연구에서는 교외지역 대기 에어로졸의 특성을 파악하기 위하여 지구온난화와 밀접한 관련이 있다고 알려진 블랙카본 농도를 측정하였고, 그 결과들을 기상 요소들과 비교하였다. 필터 기반 측정 장치인 MAAP (Multi Angle Absorption Photometer)를 이용하여 측정된 블랙카본 농도와 황사농도, 습도, 온도 및 풍속을 비교하였다. 블랙카본 농도는 4~5월에 높으며 6~9월에 낮은 경향을 보였다. 블랙카본 농도는 PM10(직경 $10{\mu}m$ 이하 입자상 물질) 농도 및 습도와는 비례관계를 보였으며 온도 및 풍속과는 반비례 관계를 보였다. 또한 디젤엔진에서 발생한 블랙카본의 직경 및 광흡수 계수 및 수농도를 측정하여 흡수 단면적을 도출 하였고 이를 통하여 교외 지역 블랙카본의 수준을 평가 할 수 있는 방법을 소개하였다.

• 한국입자에어로졸학회지
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• 제13권2호
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• pp.97-104
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• 2017

In order to characterize atmospheric aerosols in Chungcheong area, black carbon concentration, which is known to be closely related to global warming, was measured and compared with $PM_{10}$, $PM_{2.5}$ concentrations and various meteorological parameters such as wind velocity and wind direction. Multi Angle Absorption Photometer (MAAP), a filter-based equipment, was used for the black carbon measurement, and the $PM_{10}$, $PM_{2.5}$ concentrations, wind velocity and wind direction were provided by the local monitoring stations. Black carbon concentration was monitored to be high in spring and winter but low in fall. $PM_{10}$ concentration was observed to be high when westerly wind was strong.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.547-548
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• 2004

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.589-596
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• 2013

In a pressurized heavy water reactor, following loss of the primary coolant, severe core damage would begin with the depletion of the liquid moderator, exposing the top row of internally-voided fuel channels to steam cooling conditions on the inside and outside. The uncovered fuel channels would heat up, deform and disassemble into core debris. Large inventories of water passively reduce the rate of progression of the accident, prolonging the time for complete loss of engineered heat sinks. The efficacy of available backup and ultimate heat sinks, available in a CANDU 6 reactor, in mitigating the consequences of a prolonged station blackout scenario was analysed using the MAAP4-CANDU code. The analysis indicated that the steam generator secondary side water inventory is the most effective heat sink during the accident. Additional heat sinks such as the primary coolant, moderator, calandria vault water and end shield water are also able to remove decay heat; however, a gradually increasing mismatch between heat generation and heat removal occurs over the course of the postulated event. This mismatch is equivalent to an additional water inventory estimated to be 350,000 kg at the time of calandria vessel failure. In the Enhanced CANDU 6 reactor ~2,040,000 kg of water in the reserve water tank is available for prolonged emergencies requiring heat sinks.

• 한국대기환경학회지
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• 제31권5호
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• pp.472-481
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• 2015

Black carbon (BC) aerosols were monitored at the KIST site ($37.603^{\circ}N$, $127.046^{\circ}E$) and Cheonan-KOREATECH site ($36.766^{\circ}N$, $127.281^{\circ}E$) during the pre KORea-US Air Quality Study (KORUS-AQ) campaign using a couple of Muliti Angle Absorption Photometers (MAAP). BC mass concentrations were presented as $2.14{\pm}1.06{\mu}g/m^3$ and $0.94{\pm}0.60{\mu}g/m^3$ at KIST site (Seoul) and KOREATECH site (Cheonan), respectively. BC mass concentrations measured at KIST and KOREATECH sites from 22:00 on May 22 to 12:00 on May 23, 2015 showed 80% and 72% higher than average BC mass concentrations measured during campaign period, respectively. It indicates both sites could be influenced by a remote source. Similar patterns of BC concentrations between two sites from 20:00 to 24:00 on June 6, 2015 implies that the BC could be transported into both sites and then be stagnant inside the Korean Peninsula. Diurnal variation of BC in weekdays and weekends were also presented for the KIST and KOREATECH sites. Morning rush hour peak was observed at KIST site located in metropolitan area though no distinct morning rush hour peak was not observed at KOREATECH site located in a suburban area. This study revealed transport pathways of BC near the Korean Peninsula using back-trajectory analysis of BC measured both in a metropolitan area and in a suburban area.

• 한국산업정보학회논문지
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• 제27권6호
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• pp.95-103
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• 2022

원자력발전소의 중대사고 발생 시 신속하고 정확하게 사고 상황을 파악해야 하며, 이러한 사고진단 정보를 획득했을 때 적절한 사고관리 및 대응을 수행할 수 있다. 본 연구에서는 국가원자력 재난관리 시스템인 AtomCARE (Computerized technical Advisory system for a Radiological Emergency)로 전송되는 주요 발전소 정보로부터 중대사고 상황을 진단하는데 있어 딥러닝 기술의 접목을 고려하였다. 이를 위하여 주요 시나리오를 선정하고 사고 진행에 따른 상세 시나리오에 대하여 중대사고 해석 코드인 MAAP5 다량 계산을 통한 학습 DB를 구축하였다. 그리고 이 DB의 학습을 통하여 주요 발전소 정보로부터 중대사고 상세 시나리오를 분류할 수 있는, 즉 중대사고 상황을 진단할 수 있는 기술을 개발하였다. 또한 블라인드 테스트와 주성분분석을 통한 검증을 수행하였다. 본 연구에서 개발한 기술은 향후 전체 중대사고 시나리오로 확장 및 적용 가능할 것으로 판단되며 신속하고 정확한 사고진단의 기반기술로 활용 가치가 높을 것으로 기대된다.