데이터 기반 경험적 모델의 원전 계측기 고장검출 민감도 평가

허섭(Seop Hur),김재환(Jae-Hwan Kim),김정택(Jung-Taek Kim),오인석(In-Sock Oh),박재창(Jae-Chang Park),김창회(Chang-Hwoi Kim) 대한전기학회 2016 전기학회논문지 Vol.65 No.5

When an accident occurs in the nuclear power plant, the faulted information might mislead to the high possibility of aggravating the accident. At the Fukushima accident, the operators misunderstood that there was no core exposure despite in the processing of core damage, because the instrument information of the reactor water level was provided to the operators optimistically other than the actual situation. Thus, this misunderstanding actually caused to much confusions on the rapid countermeasure on the accident, and then resulted in multiplying the accident propagation. It is necessary to be equipped with the function that informs operators the status of instrument integrity in real time. If plant operators verify that the instruments are working properly during accident conditions, they are able to make a decision more safely. In this study, we have performed various tests for the fault detection sensitivity of an data-driven empirical model to review the usability of the model in the accident conditions. The test was performed by using simulation data from the compact nuclear simulator that is numerically simulated to PWR type nuclear power plant. As a result of the test, the proposed model has shown good performance for detecting the specified instrument faults during normal plant conditions. Although the instrument fault detection sensitivity during plant accident conditions is lower than that during normal condition, the data-drive empirical model can be detected an instrument fault during early stage of plant accidents.

원전 안전필수 계측제어시스템의 주기적 자동고장검출기능에 따른 고장허용 평가모델

허섭(Seop Hur),김동훈(Dong-Hoon Kim),최종균(Jong-Gyun Choi),김창회(Chang-Hwoi Kim),이동영(Dong-Young Lee) 대한전기학회 2013 전기학회논문지 Vol.62 No.7

This study suggests a generalized availability and safety evaluation model to evaluate the influences to the system"s fault tolerant capabilities depending on automatic fault detection function such as the automatic periodic testings. The conventional evaluation model of automatic fault detection function deals only with the self diagnostics, and supposes that the fault detection coverage of self diagnostics is always constant. But all of the fault detection methods could be degraded. For example, the periodic surveillance test has the potential human errors or test equipment errors, the self diagnostics has the potential degradation of built-in logics, and the automatic periodic testing has the potential degradation of automatic test facilities. The suggested evaluation models have incorporated the loss or erroneous behaviors of the automatic fault detection methods. The availability and the safety of each module of the safety grade platform have been evaluated as they were applied the automatic periodic test methodology and the fault tolerant evaluation models. The availability and safety of the safety grade platform were improved when applied the automatic periodic testing. Especially the fault tolerant capability of the processor module with a weak self-diagnostics and the process parameter input modules were dramatically improved compared to the conventional cases. In addition, as a result of the safety evaluation of the digital reactor protection system, the system safety of the digital parts was improved about 4 times compared to the conventional cases.

원자력발전소 안전필수시스템 고장허용능력에 대한 자가진단기능 저하 영향 분석

허섭(Seop Hur),황인구(In-Koo Hwang),이동영(Dong-Young Lee),최헌호(Heon-Ho Choi),김양모(Yang-Mo Kim),이상정(Sang-Jeong Lee) 대한전기학회 2010 전기학회논문지 Vol.59 No.8

The safety critical systems in nuclear power plants should be designed to have a high level of fault tolerant capability because those systems are used for protection or mitigation of the postulated accidents of nuclear reactor. Due to increasing of the system complexity of the digital based system in nuclear fields, the reliability of the digital based systems without an auto-test or a self-diagnostic feature is generally lower than those of analog system. To overcome this problem, additional redundant architectures in each redundant channel and self-diagnostic features are commonly integrated into the digital safety systems. The self diagnostic function is a key factor for increasing fault tolerant capabilities in the digital based safety system. This paper presents an availability and safety evaluation model to analyze the effect to the system's fault tolerant capabilities depending on self-diagnostic features when the loss or erroneous behaviors of self-diagnostic function are expected to occur. The analysis result of the proposed model on the several modules of a safety platform shows that the improvement effect on unavailability of each module has generally become smaller than the result of usage of conventional models and the unavailability itself has changed significantly depending on the characteristics of failures or errors of self-diagnostic function.

고 선량율 감마선 조사에 따른 렌즈의 열화

조재완(Jai-Wan Cho),이준구(Joon-Koo Lee),허섭(Seop Hur),구인수(In-Soo Koo),홍석붕(Seok-Boong Hong) 대한전기학회 2009 전기학회논문지 Vol.58 No.7

Assumed that an IPTV camera system is to be used as an ad-hoc sensor for the surveillance and diagnostics of safety-critical equipments installed in the in-containment building of the nuclear power plant, an major problem is the presence of high dose-rate gamma irradiation fields inside the one. In order to uses an IPTV camera in such intense gamma radiation environment of the in-containment building, the radiation-weakened devices including a CCD imaging sensor, FPGA, ASIC and microprocessors are to be properly shielded from high dose-rate gamma radiation using the high-density material, lead or tungsten. But the passive elements such as mirror, lens and window, which are placed in the optical path of the CCD imaging sensor, are exposed to a high dose-rate gamma ray source directly. So, the gamma-ray irradiation characteristics of the passive elements, is needed to test. A CCD camera lens, made of glass material, have been gamma irradiated at the dose rate of 4.2 kGy/h during an hour up to a total dose of 4 kGy. The radiation induced color-center in the glass lens is observed. The degradation performance of the gamma irradiated lens is explained using an color component analysis.

원전 극한환경적용 센서 통신망 구조

조재완(Jai Wan Cho),이준구(Joon-Koo Lee),허섭(Seop Hur),구인수(In Soo Koo),홍석붕(Seok-Boong Hong) 대한전기학회 2008 대한전기학회 학술대회 논문집 Vol.2008 No.10

원자력 발전소 격납구조(containment) 내에 설치되는 센서, 구동기(actuator) 및 설비는 원전의 안전운전과 함께 방사능 누출사고와 같은 중대사고(severe accident) 를 예방하기 위한 것이다. 격납구조 내부는 Category I 등급으로 분류되며, 격납구조 내부에 설치되는 센서, 구동기, 기기 및 통신망은 IEEE Std. 323-1974에서 정의하는 극한환경(harsh environment) 요건에서 생존할 수 있는 내환경성이 요구된다. 이러한 엄격한 내환경성 요건으로 인해 일반 산업의 IT 기반 센서통신망이 원전 격납건물 내부에는 적용되지 않고 있다. 최근에 이르러 독일을 중심으로 신규로 건설 중이거나 계획 중인 원전에서는 일빈 산업의 IT 기반 센서통신망 적용이 검토되고 있다. 본 논문에서는 IT 기반의 첨단 센서 통신망 기술을 격납 구조내부와 같은 극한 환경에 적용하기 위한 방안을 제시하고자 한다. 정상운전중의 원전 격납 건물 내부의 환경(온도, 감마선, 습도) 특성과 중대 사고를 가정한DBA (설계 기준사고) 요건에서의 환경 특성을 조사하였다. 또한 설계기준사고에서 정의한 감마선 조사 환경에서 통신 시스템의 생존성을 실험하였다. 이를 토대로 격납구조 내부의 원전 극한 환경 통신망의 개선방안을 제시하고자 한다.

원전 극한 환경적용을 위한 필드버스 통신망 요건

조재완(Jai Wan Cho),이준구(Joon-Koo Lee),허섭(Seop Hur),구인수(In Soo Koo),홍석붕(Seok-Boong Hong) 한국IT서비스학회 2009 한국IT서비스학회지 Vol.8 No.2

As the result of the rapid development of IT technology, an on-line diagnostic system using the fieldbus communication network coupled with a smart sensor module will be widely used at the nuclear power plant in the near future. The smart sensor system is very useful for the prompt understanding of abnormal state of the key equipments installed in the nuclear power plant. In this paper, it is assumed that a smart sensor system based on the fieldbus communication network for the surveillance and diagnostics of safety-critical equipments will be installed in the harsh-environment of the nuclear power plant. It means that the key components of fieldbus communication system including microprocessor, FPGA, and ASIC devices, are to be installed in the RPV(reactor pressure vessel) and the RCS(reactor coolant system) area, which is the area of a high dose-rate gamma irradiation fields. Gamma radiation constraints for the DBA(design basis accident) qualification of the RTD sensor installed in the harsh environment of nuclear power plant, are typically on the order of 4kGy/h. In order to use a fieldbus communication network as an ad-hoc diagnostics sensor network in the vicinity of the RCS pump area of the nuclear power plant, the robust survivability of IT-based micro-electronic components in such intense gamma-radiation fields therefore should be verified. An intelligent CCD camera system, which are composed of advanced micro-electronics devices based on IT technology, have been gamma irradiated at the dose rate of about 4.2kGy/h during an hour up to a total dose of 4 kGy. The degradation performance of the gamma irradiated CCD camera system is explained.