• Nuclear Engineering and Technology
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• 제45권5호
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• pp.637-652
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• 2013

Instrumentation and control systems in nuclear power plants have been digitalized for the purpose of maintenance and precise operation. This digitalization, however, brings out issues related to cyber security. In the most recent past, international standard organizations, regulatory institutes, and research institutes have performed a number of studies addressing these systems cyber security.. In order to provide information helpful to the system designers in their application of cyber security for the systems, this paper presents methods and considerations to define attack vectors in a target system, to review and select the requirements in the Regulatory Guide 5.71, and to integrate the results to identify applicable technical security control requirements. In this study, attack vectors are analyzed through the vulnerability analyses and penetration tests with a simplified safety system, and the elements of critical digital assets acting as attack vectors are identified. Among the security control requirements listed in Appendices B and C to Regulatory Guide 5.71, those that should be implemented into the systems are selected and classified in groups of technical security control requirements using the results of the attack vector analysis. For the attack vector elements of critical digital assets, all the technical security control requirements are evaluated to determine whether they are applicable and effective, and considerations in this evaluation are also discussed. The technical security control requirements in three important categories of access control, monitoring and logging, and encryption are derived and grouped according to the elements of attack vectors as results for the sample safety system.

• 플랜트 저널
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• 제4권2호
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• pp.60-65
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• 2008

As the operating conditions in a supercritical oxidation reactor are set in high temperature with high pressure causing a reactor suffering from the harsh circumstances. It means the reactor adopts itself with Fe-Cr alloy in acidic atmosphere with low pH value and Ni alloy in basic atmosphere with high pH value due to its superior corrosion resistance. The study, whose target waster water is pertinent to the latter part, has selected Ni alloy such as ostenite type stainless steel 304 and 316, superstainless steel AL6XN, Inconel 625, MAT 21, and titanium Gr. 5 in order to measure corrosion resistance against those samples under the same conditions of temperature and pressure applied for a supercritical oxidation reactor. The result shows the identifiable difference in corrosion resistance by observing the surface states through a scanning probe microscope as well as measuring the weight loss through making the samples above deposited in wastewater for two-week and four-week stay. The purpose of this corrosion experiment is to identify the most corrosion-resistant material among sample species pre-selected according to pH concentration of wastewater in pursue of applying for a reactor exposed to the extreme corrosion environment. It is because such a reactor made of a verified material enables to safeguard a stable operation under the supercritical wastewater processing facility.

• 대한조선학회논문집
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• 제52권3호
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• pp.265-274
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• 2015

International organizations and classification societies established rules and regulations to which shipbuilders and ship operators should comply during design, construction, even operation keeping from hazard to life of crews and ocean environment. Hence, rules and regulations could be guidelines for design and construction of ship sometimes. In practical wise, ship structure designers be predisposed to design lightest and easy-to-product structures which satisfy rules and regulations. Therefore, changes of rules and regulations are remarkably important issue to related industries. In 2006, IACS established and released Common Structural Rules for Bulk Carrier and Common Structural Rules for Double Hull Oil Tanker. These CSRs are consolidated and unified rules of class society's rules. But these two rules are different from each other. IACS has plan to release unified rule of two ship type called Harmonized Common Structural Rule for Bulk Carriers and Oil Tankers. This new rule will be effective from July 2015. Hence, bulk carrier and double hull oil tanker whose contract date is on and thereafter July 2015 should be complied with CSR-H. Therefore, it is highly important to be aware of consequences and cause of consequences with respect to CSR-H. The object of this research is to compare requirements of structure scantling in way of midship area for selected target ship according to CSRs and CSR-H and to analysis cause of deviation between two rules.

• The Korean Journal of Pain
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• 제8권2호
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• pp.350-353
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• 1995

The first lesion in neural tissue produced by electrical currents were made in the 19th century by workers using direct current. In 1953, Sweet and Mark clearly demonstrated that DC lesions have unpredictable and ragged borders and may vary in size. They, as well as Hunsperger and Wyss, suggested that the use of high frequency currents might provide improved results and were proved correct. However, $Bovie^{(R)}$ electrosurgical unit may also be used in percutaneous medial branch neurotomy if a lesion made at a point or the dorsal surface of the transverse process just caudal to the most medial end of the superior edge of the transverse process (Bogduk's method). At this point the medial branch lies on the bone and its depth and medial displacement are defined by the bone which precludes the need for lateral radiographs to check placement. A lesion was made at same target point using the $Bovie^{(R)}$ electrosurgical unit in a 41 year male patient who had received a Kaneda operation because of L2 compression fracture. The patient was relieved of pain without any adverse effects.

• 방사성폐기물학회지
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• 제12권1호
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• pp.79-88
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• 2014

원자력이용시설에서 발생한 작은 크기의 금속 조각들을 효과적으로 제염하는 스마트 장치를 개발하였다. 이 장치는 자성연마재를 포함한 영역의 자속밀도를 연속적으로 변화시키는 방법과 초음파를 이용하는 다중 제염장치이다. 한편, 제염 효율을 높이기 위해 제염 장치가 제염 대상 전체에 작용하도록 장치들의 구성을 수정하였다. 개발된 장치들의 최적 작동조건을 도출하여 샘플로 선정한 소형의 금속방사성페기물에 대하여 자기장과 초음파제염을 각각 15분간 실시하였다. 그 결과 제염계수의 범위는18~56으로 크게 향상되었으며 제염 후 모든 샘플은 백그라운드(BKG)값 이하로 확인되었다.

• 대한환경공학회지
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• 제31권10호
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• pp.865-872
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• 2009

슬러지의 감량과 최종처분 기술 개발을 위해 실험실 규모 호기성 소화공정을 279일간 운전하였다. 혐기성 소화 슬러지를 원료로 $40^{\circ}C$에서 120분간 알칼리 전처리하여 호기성 소화조에 유입시켰다. 유입 슬러지 성상과 HRT의 변화에 따라 소화효율의 변화가 있었으며 적정 HRT는 6일인 것으로 나타났다. 이때 $NH_3$-N, SCOD, TKN, TCOD, SS, VSS의 평균 제거율(소화조 유입 슬러지 기준)은 각각 97.4%, 81.7%, 68.7%, 61.4%, 50.6%, 47.0% 이었다. SS는 전처리와 호기성 소화를 통해 원료 슬러지(23,920 mg/L)의 73.9% 감량화가 가능하였다. 처리 슬러지는 약 350 mg/L의 SCOD를 포함하고 있어 액비로 활용하기에 무리가 없을 것으로 판단되었다. HRT를 5일 이상으로 유지할 경우 질산화 반응이 활성화되었으며 최대 658 mg/L의 유출 슬러지 질산성 질소 농도를 얻을 수 있었다. 암모니아성 질소 농도는 20 mg/L 내외로 크게 감소하였다.

• 한국인터넷방송통신학회논문지
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• 제16권2호
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• pp.151-155
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• 2016

우리는 이 논문에서 ADPCM (adaptive differential pulse code modulation)을 적용함으로써 디밍 콘트롤러를 갖는 LED 드라이버의 설계를 제시한다. ADPCM 장비는 고해상도를 가지고 LED 전류를 정확하게 제어하며, 고조파 전류 펄스의 퍼짐으로 인하여 초래되는 RFI 를 감소시켜 준다. 또한 제어 동작의 정밀도를 높여준다. 이 연구에서 LED에 펄스 전류를 인가함으로써 고효율 에너지의 LED를 제어하는 디지털 제어회로의 설계를 제시한다. 우리가 설계한 LED 전류구동시스템은 디지털 제어 부와 아날로그 SMPS (스위치 모드 파워 서플라이)를 별도로 구현한 두개의 시스템이다. 입력레벨이 0.7 인 경우의 시뮬레이션 결과는 시그마 델타 변조를 하여 얻은 D/A 컨버터의 출력을 나타내었다. 개수가 510 개인 펄스신호의 경우 0.15 % 의 정밀도를 얻을 수 있었다.

• 한국철도학회논문집
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• 제20권4호
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• pp.474-481
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• 2017

국내에서 태양광 발전설비 설계 시 설계 단계에서의 태양광발전소의 발전량 예측은 국내 현장임에도 불구하고 PVsyst, PVWatts 등 해외 발전량 예측 프로그램과 해외 기상 자료를 이용하여 발전량을 예측하는 경우가 대부분을 차지하고 있는 실정이다. 본 논문에서는 기상정보를 활용한 발전량 예측 비교 연구를 위하여 현재 운영중인 2개 지역의 국내 태양광발전소를 대상지로 선정하였다. 발전량 예측 프로그램인 PVsyst를 활용하여 Meteonorm 7.1과 NASA-SSE의 해외 기상정보를 이용한 발전량 예측값과 국내 기상청 (Korea Meteorology Administration) 기상정보를 활용한 발전량 예측 정확성을 비교하였다. 추가적으로, 기상자료 비교 분석을 통한 발전량 예측 개선 방안을 연구하고, 최종적으로 실제 발전량과의 비교 분석을 통해 기후요소가 고려된 태양광 발전량 예측 수정 모델을 제시하였다.

• Journal of Radiation Protection and Research
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• 제19권1호
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• pp.13-22
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• 1994

CANDU 6 중수형 원자로 운전중에 Calandria Shell내에서 발생하는 $(n,\;{\gamma})$ 반응유발 열중성자속분포와 CANDU 6 발전소의 측면 및 하단 차폐구조에서의 방사선 선량률을 계산하기 위하여 몬테칼로 방법을 이용한 MCNP 4.2 코드를 사용하였다. 계산결과, Mainshell, Annular Plate와 Subshell내 의 열중성자속분포는 $10^{11}{\sim}10^{13}\;neutrons/cm^2-sec$로 나타났고, 이는 DOT 4.2 코드의 계산결과와 비교해 볼 때 약간 큰 값들의 분포를 보여주고 있다. 이 계산결과의 응용으로서 작업자 접근가능지역 (Worker Accessible Areas)에서의 감마선량률을 계산해본 결과 설계목표치인 $6{\mu}Sv/h$보다 낮은 값을 주는 것으로 나타났다. $(n,\;{\gamma})$ 반응유발 열중성자속분포에 대한 MCNP 4.2 코드의 계산결과는 CANDU 6형 원자로의 방사선 차폐해석에 중요한 자료로 널리 이용될 수 있을 것이다.

• Journal of Radiation Protection and Research
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• 제42권3호
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• pp.141-145
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• 2017

Background: The concrete walls inside the vaults of cyclotron facilities are activated by neutrons emitted by the targets during radioisotope production. Reducing the amount of radioactive waste created in such facilities is very important in case they are decommissioned. Thus, we proposed a strategy of reducing the neutron activation of the concrete walls in cyclotrons during operation. Materials and Methods: A polyethylene plate and B-doped Al sheet (30 wt% of B and 2.5 mm in thickness) were placed in front of the wall in the cyclotron room of a radioisotope production facility for pharmaceutical use. The target was Xe gas, and a Cu block was utilized for proton dumping. The irradiation time, proton energy, and beam current were 8 hours, 30 MeV, and $125{\mu}A$, respectively. To determine a suitable thickness for the polyethylene plate set in front of the B-doped Al sheet, the neutron-reducing effects achieved by inserting such sheets at several depths within polyethylene plate stacks were evaluated. The neutron fluence was monitored using an activation detector and 20-g on de Au foil samples with and without 0.5-mm-thick Cd foil. Each Au foil sample was pasted onto the center of a polyethylene plate and B-doped Al sheet, and the absolute activity of one Au foil sample was measured as a standard using a Ge detector. The resulting relative activities were obtained by calculating the ratio of the photostimulated luminescence of each foil sample to that of the standard Au foil. Results and Discussion: When the combination of a 4-cm-thick polyethylene plate and B-doped Al sheet was employed, the thermal neutron rate was reduced by 78%. Conclusion: The combination of a 4-cm-thick polyethylene plate and B-doped Al sheet effectively reduced the neutron activation of the investigated concrete wall.