Fault Detection and Diagnosis (FDD) for Heating, Ventilation and Air Conditioning (HVAC) Systems: A Review of Current Research Trends and Insight for Nuclear Fuel Cycle (NFC) Facilities

Hyojik Lee,Woo Jin Jo,Eui Young Kim,Seok Jun Seo 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

In the nuclear fuel cycle (NFC) facilities, the failure of Heating Ventilation and Air Conditioning (HVAC) system starts with minor component failures and can escalate to affecting the entire system, ultimately resulting in radiological consequences to workers. In the field of air-conditioning and refrigerating engineering, the fault detection and diagnosis (FDD) of HVAC systems have been studied since faults occurring in improper routine operations and poor preventive maintenance of HVAC systems result in excessive energy consumption. This paper aims to provide a systematic review of existing FDD methods for HVAC systems therefore explore its potential application in nuclear field. For this goal, typical faults and FDD methods are investigated. The commonly occurring faults of HVAC are identified through various literature including publications from International Energy Agency (IEA) and American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). However, most literature does not explicitly addresses anomalies related to pressure, even though in nuclear facilities, abnormal pressure condition need to be carefully managed, particularly for maintaining radiological contamination differently within each zone. To build simulation model for FDD, the whole-building energy system modeling is needed because HVAC systems are major contributors to the whole building’s energy and thermal comfort, keeping the desired environment for occupants and other purposes. The whole-building energy modeling can be grouped into three categories: physics-based modeling (i.e., white-box models), hybrid modeling (i.e., grey-box models), and data-driven modeling (i.e., black-box models). To create a white-box FDD model, specialized tools such as EnergyPlus for modeling can be used. The EnergyPlus is open source program developed by US-DOE, and features heat balance calculation, enabling the dynamic simulation in transient state by heat balance calculation. The physics based modeling has the advantage of explaining clear cause-and-effect relationships between inputs and outputs based on heat and mass transfer equations, while creating accurate models requires time and effort. Creating a black-box FDD model requires a sufficient quantity and diverse types of operational data for machine learning. Since operation data for HVAC systems in existing nuclear cycle facilities are not fully available, so efforts to establish a monitoring system enabling the collection, storage, and management of sensor data indicating the status of HVAC systems and buildings should be prioritized. Once operational data are available, well-known machine learning methods such as linear regression, support vector machines, random forests, artificial neural networks, and recurrent neural networks (RNNs) can be used to classify and diagnose failures. The challenge with black-box models is the lack of access to failure data from operating facilities. To address this, one can consider developing black-box models using reference failure data provided by IEA or ASHRAE. Given the unavailability of operation data from the operating NFC facilities, there is a need for a short to medium-term plan for the development of a physics-based FDD model. Additionally, the development of a monitoring system to gather useful operation data is essential, which could serve both as a means to validate the physics-based model and as a potential foundation for building data-driven model in the long term.

Mass Spectrometry Imaging of Microbes

( Hyojik Yang ),( David R Goodlett ),( Robert K Ernst ),( Alison J Scott ) 한국질량분석학회 2020 Mass spectrometry letters Vol.11 No.3

Microbes influence many aspects of human life from the environment to health, yet evaluating their biological processes at the chemical level can be problematic. Mass spectrometry imaging (MSI) enables direct evaluation of microbial chemical processes at the atomic to molecular levels without destruction of valuable two-dimensional information. MSI is a label-free method that allows multiplex spatiotemporal visualization of atomic- or molecular-level information of microbial and microberelated samples. As a result, microbial MSI has become an important field for both mass spectrometrists and microbiologists. In this review, basic techniques for microbial MSI, such as ionization methods and analyzers, are explored. In addition, we discuss practical applications of microbial MSI and various data-processing techniques.

Monitoring the reactive oxygen species risk assessment in aquatic environment

Hyojik Yoon,Sungpyo Kim 대한환경공학회 2019 대한환경공학회 학술발표논문집 Vol.2019 No.-

Comparison of Inert Hot Cell Atmospheric Systems

Hyojik Lee,Byung Suk Park,Seung Nam Yu 한국방사성폐기물학회 2019 한국방사성폐기물학회 학술논문요약집 Vol.2019 No.10

Advancement Strategies for Nuclear Fuel Cycle Facility Operations

Hyojik Lee,Eui Young Kim,Woo Jin Jo,Seok Jun Seo 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

The domestic representative nuclear fuel cycle facilities are post-irradiation examination facility (PIEF) and Irradiated Examination Facility (IMEF) at KAERI. They have regularly operated since 1991 and 1993, respectively. Due to the long period of use, the facilities are ageing, and maintenance costs are increasing every year. The maintenance methods have mainly been breakdown maintenance (BM) and partially preventive maintenance (PM). They involve replacing components that have problems through periodic inspections by on-site inspectors. However, these methods are not only uncertain in terms of replacement cycles due to worker’s deviation on the inspection results, but also make it difficult to respond accidents developed through failures on the critical equipment that confines radioactive material. Therefore, an advanced operation and maintenance studied in 2022 through all of nuclear facilities operated at KAERI. Advancement strategy in four categories (safety, sustainability, performance, innovativeness) was analyzed and their priorities according to a facility environment were determined so a roadmap for advanced operation and maintenance could be developed. The safety and sustainability are higher importance than the performance and innovativeness because facilities at KAERI has an emphasis on research and development rather than industrial production. Thus, strategy for advancement has focused even more on strengthening the safety and sustainability. To enhance safety, it has been identified that immediate improvement of aged structures, systems, and components (SSCs) through large-scale replacement is necessary, while consideration of implementing an ageing management program (AMP) in the medium to long term is also required. Facility sustainability requires strengthening operation expertise through training, education, and cultivation of specialized personnel for each system, and addressing outstanding regulatory issues such as approval of radiation environment report on the nuclear fuel processing facilities and improvement work according to fire hazard analysis. One of the safety enhancement methods, AMP, is a new maintenance approach that has not been previously applied, so it had to be thoroughly examined. In this study, an analysis was conducted on the procedure and method for introducing an AMP. An AMP for nuclear fuel cycle facilities was developed by analyzing the AMP applied to the BR2 research reactor in Belgium and modifying it for application to nuclear fuel cycle facilities. The ageing management for BR2 has the objective to maintain safety, availability and cost efficiency and three-step process. The first step is the classification of SSCs into four classes to apply graded approach. Secondly, ageing risk is assessed to identify critical failure modes, their frequency and precursors. Final step involves defining measures to reduce the ageing risk to an acceptable level in order to integrate the physical and economic aspects of ageing into a strategy for inspection, repair, and replacement. Similar approach was applied to the nuclear fuel cycle facility. Firstly, the SSCs of nuclear fuel cycle facilities have been classified according to their safety and quality classifications, as well as whether they are part of the confinement boundary. The SSCs involved in the confinement boundary were given more weight in the classification process, even if they are not classified as safety-class. A risk index for ageing was introduced to determine which prevention and mitigation measure should be chosen. By multiplying the health index and the impact index, the ageing risk matrix provides a numerical score that represents guidance on the prevention and mitigation of ageing effect. The health index is determined by combining the likelihood of failure and engineering evaluation of the current condition of SSCs, whereas the impact index is calculated by taking into account the severity of consequences and the duration of downtime resulting from a failure. This ageing management has to be thoroughly reviewed and modified to suit each facility before being applied to nuclear fuel cycle facilities.

환경 내 변화에 따른 활성산소종 발생 모니터링

윤효직 ( Hyojik Yoon ),김성표 ( Sungpyo Kim ) 한국물환경학회(구 한국수질보전학회) 2018 한국물환경학회·대한상하수도학회 공동 춘계학술발표회 Vol.2018 No.-

보안전문인력 양성을 위한 직업분류체계별 정보보호 핵심지식 설계

이효직(Hyojik Lee),나원철(Onechul Na),성소영(Soyoung Sung),장항배(Hangbae Chang) 한국전자거래학회 2015 한국전자거래학회지 Vol.20 No.3

최근 발생하는 정보보안 사고는 정보통신기술의 발전과 더불어 전파속도나 그 피해규모 역시 빠른 속도로 증가하고 있다. 또한 미래 환경이 산업융합의 시대로 발전함에 따라 가상의 사이버 환경이 물리적인 환경까지 확장되면서 다양한 형태의 새로운 보안 위협이 발생하고 있다. 새롭게 대두되는 보안 위협을 해결하기 위해서는 전통적인 기술 위주의 단편화된 보안인재를 넘어서, 기술적 보호와 물리적 보호를 관리적 관점에서 아우를 수 있는 다차원적 보안역량을 가진 보안전문인력이 필요한 시점이다. 따라서 본 논문에서는 기존의 기술위주의 단편화된 정보보호 교육을 넘어서 산업융합 환경에 맞는 보안전문인력을 양성하기 위하여 직업분류체계별로 특색 있는 정보보호 교과목을 도출하고 이를 이용하여 각 직업군간의 이동시 추가로 교육이 필요한 교과목에 대한 분석을 실시하고자 한다. 본 연구결과는 기술적 관점의 정보보호 교과목과 경영·관리적 관점의 정보보호 교과목의 조화로운 융합을 통해 산업융합환경에 어울리는 다차원적 보안인력을 육성하고, 정보보호 직업군간의 이동 시 각 직업군별 핵심 지식을 효과적으로 습득할 수 있는 교육훈련과정을 개발하는 데에도 긍정적인 영향을 미칠 것으로 기대된다. Information Security Incidents that have recently happen rapidly spread and the scale of that incidents’ damage is large. In addition, as it proceeds to the era of converged industry in the future environment and the virtual cyber world expands to the physical world, new types of security threats have occurred. Now, it is time to supply security professionals who have a multi-dimensional security capabilities that can manage the strategies of technological security and physical security from the management point of view, rather than the ones who primarily focus on the traditional technologic-centered strategies to solve new types of security threats. In conclusion, in this paper we try to produce the curriculum of information security featured in the occupational classification system and analyze the subjects that are additionally required for those who move to other occupations to cultivate security professionals who suited to the converged-industrial environment. It is expected that multi-dimensional security professionals who suited to the converged-industrial environment will be cultivated by harmoniously integrating information security subjects from technological and business/managerial perspectives, and education training courses will be developed that effectively provide core knowledges per occupational classification when people moves to other occupations in the areas of information security.

연구보안 수준측정 모형 설계에 관한 연구

이효직 ( Hyojik Lee ),김자원 ( Jawon Kim ),나원철 ( Onechul Na ),장항배 ( Hangbae Chang ) 한국정보처리학회 2017 한국정보처리학회 학술대회논문집 Vol.24 No.1

최근 국가연구개발사업은 개방형 연구환경으로 변화되어지고 있다. 이러한 변화는 연구개발 자원 및 시간 절감, R&D 투자효과 증대 등 긍정적인 효과를 동반하지만 연구 수행 과정, 연구성과물 유출과 같은 역기능이 발생하고 있다. 따라서 본 연구에서는 연구환경 변화에 따른 연구성과물 유출 가능성을 줄이기 위해서 자체적으로 보안관리 및 평가를 할 수 있는 연구보안 수준측정 모형을 설계하고자 한다. 이는 연구기관의 보안 수준 파악과 향상을 위해 유용하게 활용될 것으로 기대된다.

수계 내 향정신성 의약품의 독성 평가 : Zebrafish 행동성 및 뇌파 분석

윤효직 ( Hyojik Yoon ),김정연 ( Jungyeon Kim ),신준녕 ( Junnyeong Shin ),김성표 ( Sungpyo Kim ) 한국물환경학회 2021 한국물환경학회·대한상하수도학회 공동 춘계학술발표회 Vol.2021 No.-

Oxidative stability of chia seed oil and flax seed oil and impact of rosemary (Rosmarinus officinalis L.) and garlic (Allium cepa L.) extracts on the prevention of lipid oxidation

Jung Hyojik,Kim Inhwan,Jung Sunghyeon,Lee Jihyun 한국응용생명화학회 2021 Applied Biological Chemistry (Appl Biol Chem) Vol.64 No.1

Chia seed and flax seed oils are rich in polyunsaturated fatty acids, but are susceptible to oxidative deterioration. The aim of this study was to determine the oxidative stability of chia seed and flax seed oils and enhance the stability using rosemary or garlic extracts. During accelerated storage at 65 °C for 14 days, the antioxidant abilities of rosemary or garlic extracts were evaluated and compared with those of butylated hydroxy toluene, ascorbyl palmitate, and α-tocopherol using peroxide value, conjugated dienoic acids, free fatty acid, thiobarbituric acid value analysis. The profile of volatiles, fatty acid composition, and the tocopherol contents in the treated and/or untreated oils were also determined. Active ingredients of rosemary and garlic extracts were also determined. Rosemary extract was found to provide higher oxidative stability than garlic extract after 14 days in most assays (e.g., the CDA values of 4.8% for rosemary extract and 5.2% for garlic extract in chia seed oil). The contents of γ-tocopherol, linoleic acid, and α-linolenic acid were well retained in the functional oils treated with the two extracts. After accelerated storage, the content of the major odor-active volatiles varied based on the type of oil. Our findings show the potential of natural aromatic plant extracts with respect to improving the oxidative stability of functional oils.