As the demand for p-type semiconductors increases, much effort is being put into developing new p-type materials. This demand has led to the development of novel new p-type semiconductors that go beyond existing p-type semiconductors. Copper iodide (CuI) has recently received much attention due to its wide band gap, excellent optical and electrical properties, and low temperature synthesis. However, there are limits to its use as a semiconductor material for thin film transistor devices due to the uncontrolled generation of copper vacancies and excessive hole doping. In this work, p-type CuI semiconductors were fabricated using the chemical vapor deposition (CVD) process for thin-film transistor (TFT) applications. The vacuum process has advantages over conventional solution processes, including conformal coating, large area uniformity, easy thickness control and so on. CuI thin films were fabricated at various deposition temperatures from 150 to 250 °C The surface roughness root mean square (RMS) value, which is related to carrier transport, decreases with increasing deposition temperature. Hall effect measurements showed that all fabricated CuI films had p-type behavior and that the Hall mobility decreased with increasing deposition temperature. The CuI TFTs showed no clear on/off because of the high concentration of carriers. By adopting a Zn capping layer, carrier concentrations decreased, leading to clear on and off behavior. Finally, stability tests of the PBS and NBS showed a threshold voltage shift within ±1 V.

This study aims to classify R&D activities related to the nuclear fuel cycle using the deep learning methodology. First, R&D data of the Republic of Korea were collected from the National Science & Technology Information Service (NTIS) for the years 2021, 2022, and 2023. We use keywords such as ‘nuclear,’ ‘uranium,’ ‘plutonium,’ and ‘thorium’ to find nuclear-related R&D projects in the NTIS database. Among the numerous R&D projects found through keyword searches, overlapping and medical-related R&D projects were excluded. Finally, 495 R&D projects conducted in 2021, 430 R&D projects conducted in 2022, and 296 R&D projects conducted in 2023 were obtained for analysis. After that, Safeguards experts determine whether the R&D projects are subject to declaration under the AP. The values of the content validity index (CVI) and content validity ratio (CVR) were used to verify whether the experts’ judgments were valid. The 1,218 collected and labeled data were then divided 8:2 into training and test datasets to see if deep learning could be applied to classify nuclear fuel cycle-related R&D activities. We use the Python and TensorFlow packages, including RNN, GRU, and CNN methods. First, the collected text information was preprocessed to remove punctuation marks and then tokenized to make it suitable for deep learning. After 20 epochs of training to classify the nuclear fuel cycle-related R&D activities, the RNN model achieved 97.30% accuracy and a 5.85% error rate on the validation dataset. The GRU model achieved 96.53% accuracy and a 9.06% error rate on the validation dataset. In comparison, the CNN model achieved 94.61% accuracy and a 2.57% error rate on the validation dataset. When applying the test dataset to each model, the RNN model had a test accuracy of 83.20%, the GRU test accuracy of 82.79%, and the CNN model had a test accuracy of 85.66% for the same dataset. This study applied deep learning models to labeled data judged by various experts, and the CNN model showed the best results. In the future, this study will continue to develop an optimum deep learning model that can classify nuclear fuel cycle-related R&D activities to achieve the purpose of safeguards measures from open-source data such as papers and articles.

Cesium lead iodide (CsPbI3) with a bandgap of ~1.7 eV is an attractive material for use as a wide-gap perovskite in tandem perovskite solar cells due to its single halide component, which is capable of inhibiting halide segregation. However, phase transition into a photo inactive δ-CsPbI3 at room temperature significantly hinders performance and stability. Thus, maintaining the photo-active phase is a key challenge because it determines the reliability of the tandem device. The dimethylammonium (DMA)-facilitated CsPbI3, widely used to fabricate CsPbI3, exhibits different phase transition behaviors than pure CsPbI3. Here, we experimentally investigated the phase behavior of DMA-facilitated CsPbI3 when exposed to external factors, such as heat and moisture. In DMA-facilitated CsPbI3 films, the phase transition involving degradation was observed to begin at a temperature of 150 °C and a relative humidity of 65 %, which is presumed to be related to the sublimation of DMA. Forming a closed system to inhibit the sublimation of DMA significantly improved the phase transition under the same conditions. These results indicate that management of DMA is a crucial factor in maintaining the photo-active phase and implies that when employing DMA designs are necessary to ensure phase stability in DMA-facilitated CsPbI3 devices.

The licensee of nuclear facilities in the Republic of Korea should ensure the functionality of Critical Digital Assets (CDAs) is maintained and minimize the negative impact of cyber-attacks by establishing a cyber security contingency plan. The contingency plan should include detailed response guidelines for each stage of detection, analysis, isolation, eradication, and recovery and comply with the requirements specified in KINAC’s “Regulatory Standard 015 - Security for Computer and Information System of Nuclear Facilities”. However, since the cyber security contingency plan describes the overall response guidelines for CDA, it may be difficult to respond practically to cyberattacks. This paper suggests a method to address this issue by performing exercises based on the classification of CDA types. CDAs in nuclear facilities can be classified according to their characteristics. The criteria for classifying CDA types include whether the asset is a PC, whether communication ports (RS-232, 422, 485) exist, whether storage devices can be connected through USB/memory card ports and whether internal settings can be changed through HMI devices such as built-in buttons. By classifying CDA types based on the proposed criteria, the attack vectors of CDAs can be defined. By defining the attack vectors, a list of cyber-attacks that CDAs may face can be created, and abnormal symptoms of CDAs resulting from the listed cyber-attacks can be defined. By using the defined abnormal symptoms of CDAs, the response measures of detection, analysis, isolation, eradication, and recovery can be concretized and reflected in the contingency plan. This may enable a more practical emergency response. This paper presents an improvement to the cyber security emergency response plan through the definition of cyber-attacks based on the classification of CDA types. By improving the contingency plan for CDAs as a whole using the proposed method, it is expected that more effective response measures can be taken in the event of a cyber-attack.

The purpose of this study is to detect future signals and changes in nuclear-related research to apply safeguards by design to new nuclear facilities or to determine nuclear fuel cycle-related research and development (R&D) activities. First, a total of 2,029 scientific articles published between 2015 and 2022 in the journal of “Nuclear Engineering and Technology” by the Korean Nuclear Society were collected. The authors of the scientific article used their expertise and knowledge to select keywords that can properly represent the article. Therefore, in this study, the keywords of each scientific article were analyzed using the technique of text mining. We then calculated the “word frequency” and “term frequency-inverse document (TF-IDF)” values of the keywords. Consequently, significant words such as “reactor,” “nuclear,” and “fuel” were extracted, which were represented as word clouds. Furthermore, keywords extracted through text mining were quantitatively classified into weak or strong signals using a keyword emergence map (KEM). The KEM is a tool that can explore future signals because essential keywords have a high frequency of appearance, and newer keywords are more important than older keywords. The KEM results showed no keywords in the strong-signal area in the field of nuclear academia. However, keywords such as “deep learning,” “earthquake,” “zircaloy,” and “CFD” were confirmed to be distributed in the weak signal area. A weak signal indicates the most probable topic that could become a strong signal in the near future. The weak signal methodology can be applied to predict future nuclear scientific trends in the rapidly changing world. Based on the results of the study, changes in the subject of nuclear-related scientific articles over the past eight years and future signals were interpreted. The results confirmed that this method can be applied to safeguards measures of new nuclear facilities in the design stage and can be used to detect R&D activities related to the nuclear fuel cycle in advance.

Halide perovskite solar cells (PSCs) have improved rapidly over the past few years, and research on the optoelectrical properties of halide perovskite thin films has grown as well. Among the characterization techniques, photoluminescence (PL), a method of collecting emitted photons to evaluate the properties of materials, is widely applied to evaluate improvements in the performance of PSCs. However, since only photons emitted from the film in the escape cone are included, the photons collected in PL are a small fraction of the total photons emitted from the film. Unlike PSCs power conversion efficiency, PL measuring methods have not been standardized, and have been evaluated in a variety of ways. Thus, an in-depth study is needed of the methods used to evaluate materials using PL spectra. In this study, we examined the PL spectra of the perovskite light harvesting layer with different measurement protocols and analyzed the features. As the incident angle changed, different spectra were observed, indicating that the PL emission spectrum can depend on the measuring method, not the material. We found the intensity and energy of the PL spectra changes were due to the path of the emitted photons. Also, we found that the PL of halide perovskite thin films generally contains limited information. To solve this problem, the emitted photons should be collected using an integrating sphere. The results of this study suggest that the emission spectrum of halide perovskite films should be carefully interpreted in accordance with PL measuring method, since PL data is mostly affected by the method.

Kori unit 1, Korea’s first light-water nuclear power plant, was permanently shut down in June 2017. The operator, Korea Hydro & Nuclear Power Co. (KHNP), submitted a final dismantling plan for Kori unit 1 to the Nuclear Safety and Security Commission (NSSC) in May 2021. Pursuant to this procedure, the NSSC is preparing regulations for the decommissioning stage of large nuclear facilities for the first time in the Republic of Korea. The Korea Institute of Nuclear Non-proliferation and Control (KINAC) is also considering applying regulations on safeguards. Moreover, the International Atomic Energy Agency (IAEA) developed the “International Safeguards Guidelines for Nuclear Facilities under Decommissioning” in 2021. The guidelines describe the detailed application of safeguards measures to be considered when decommissioning nuclear facilities, dismantling essential equipment, and providing relevant information to the IAEA, as well as the scope of IAEA inspections. In addition, Dr. R. Bari of the Brookhaven National Laboratory (BNL) proposed the Facility Safeguardability Assessment (FSA), a methodology that reflects facility characteristics from the design stage to ensure that designers, national regulators, and the IAEA communicate smoothly regarding safeguards measures. The FSA process derives expected problems with safeguards measures considering new nuclear facilities by analyzing the gap of safeguards measures applied to existing similar nuclear facilities. This study uses the existing FSA methodology to predict problems related to safeguards measures when decommissioning nuclear facilities and to analyze deviations from safeguards measure requirements according to IAEA guidelines. To this end, the reference facility is set as an operating pressurized light water reactor; the issues with the safeguards measures are summarized using the FSA Process; and a draft safeguards concept for nuclear facilities under decommissioning is designed. Furthermore, validity is confirmed through a simple analysis of the diversion path, and implications and lessons are derived. Through this, it is possible to anticipate new safeguards measures to be applied when decommissioning nuclear facilities in the Republic of Korea and review problems and considerations in advance.

In accordance with the Enforcement Decree of the Act on Physical Protection and Radiological Emergency, operators of Nuclear Power Plants (NPP)s must conduct full cyber security exercise once a year and partial exercise at least once every half year. Nuclear operators need to conduct exercise on systems with high attack attractiveness in order to respond to the unauthorized removal of nuclear or other radioactive material and sabotage of nuclear facilities. Nuclear facilities identify digital assets that perform SSEP (Safety, Security, and Emergency Preparedness) functions as CDA (Critical Digital Assets), and nuclear operators select exercise target systems from the CDA list and perform the exercise. However, digital assets that have an indirect impact (providing access, support, and protection) from cyber attacks are also identified as CDAs, and these CDAs are relatively less attractive to attack. Therefore, guidelines are needed to select the exercise target system in the case of unauthorized removal of nuclear or other radioactive material and sabotage response exercise. In the case of unauthorized removal of nuclear or other radioactive material, these situations cannot occur with cyber attacks and external factors such as terrorists must be taken into consideration. Therefore, it is necessary to identify the list of CDAs that terrorists can use for cyber attacks among CDAs located in the path of stealing and transporting nuclear material and conduct intensive exercise on these CDAs. A typical example is a security system that can delay detection when terrorists attack facilities. In the case of sabotage exercise, a safety-related system that causes an initiating event by a cyber attack or failure to mitigate an accident in a DBA (Design Basis Accident) situation should be selected as an exercise target. It is difficult for sabotage to occur through a single cyber attack because a nuclear facility has several safety concepts such as redundancy, diversity. Therefore, it can be considered to select an exercise target system under the premise of not only a cyber attack but also a physical attack. In the case of NPPs, it is assumed that LOOP (Loss of Offsite Power) has occurred, and CDA relationships to accident mitigation can be selected as an exercise target. Through exercise on the CDA, which is more associated with unauthorized removal of nuclear or other radioactive material and sabotage of nuclear facilities, it is expected to review the continuity plan and check systematic response capabilities in emergencies caused by cyber attacks.

For the peaceful use of nuclear energy, the international community has devoted itself to fulfilling its obligations under the Safeguards Agreement with IAEA. In this regard, uranium in a radioactive waste drum should be analyzed and reported in terms of mass and 235U enrichment. In order to characterize radioactive wastes, gamma spectroscopy techniques can be effectively applied. In the case of high-resolution gamma spectroscopy, because an HPGe detector can provide excellent energy resolution, it can be applied to analyze a mixture having a complicated isotopic composition. However, other substances such as wood, concrete, and ash are mixed in radioactive waste with various form factors; hence, the efficiency calibration is difficult. On the other hand, In Situ Object Counting System (ISOCS) has a capability of efficiency calibration without standard materials, making it possible to analyze complex radioactive wastes. In this study, the analysis procedure with the ISOCS was optimized for quantification of radioactive waste. To this end, a standard radioactive waste drum at KEPCO NF and low-level radioactive waste drums at Korea Radioactive Waste Agency (KORAD) were measured. The performance of the ISOCS was then evaluated by Monte Carlo simulations, Multi-Group Analysis for Uranium (MGAU) code, and destructive analysis. As a result, the ISOCS showed good performance in the quantification of uranium for a drum with the homogenized simple geometry and long measurement time. It is confirmed that the ISOCS gamma spectroscopy technique could be used for control and accountancy of nuclear materials contained in a radioactive waste drum.

This is a comparative study of Byung-Kwa-Ryu (Korean rice cake and cookie) of the Chungcheon Province Area in the late Joseon Dynasty, based on「Jusiksiui」 in the late 1800s,「Eumsikbangmunnira」 in 1891, and 「Banchandeungsok」 in 1913. This study was also compared with the recipes of「Suunjapbang」 of 1540,「Eumsikdimibang」 of around 1670, 「Siuijeonseo」, and Gyuhabchongseo of the late 1800s. As for the Byung-Kwa-Ryu(Korean rice cake and cookie) introduced in the recipe book,「Eumsikbangmunnira」 recorded the most with 18 types of rice cakes and two types of Korean sweets, followed by「Jusiksiui. There were 14 types of rice cakes, and two types of Korean sweets. 「Banchandeungsok」 had eight types ofrice cakes and six types of Korean sweets. Yogi-tteok in「Jusiksiui」 and「Banchandeungsok」 were foods that could not be found in other recipes. Yakgwa and Jeungpyeon were in all three books as well as 「Eumsikdimibang」. These were also included in「Siuijeonseo」 and were introduced to most cookbooks. The materials used and the method of making it differed for each recipe. Many studies on cookbooks have focused on the Yeongnam region so far. This study served as an opportunity to confirm the dietary life data of the Chungcheong-do region through a review of the recipe books containing food from the Chungcheong-do region. In addition, it was possible to examine the ingredients and cooking methods used in each cookbook at the time through comparative analysis with the cookbooks in the Yeongnam region.

교통카드 데이터는 도시 유동 패턴 분석을 가능하게 하는 양질의 대용량 데이터를 제공한다. 하지만 유동 클러스터링의 방법론적 어려움으로 인해 기존의 연구들은 데이터의 이점을 최대로 활용하지 못하고 있다. 이러한 한계를 극복하고자, 본 연구는 교통카드 데이터에 기반한 효율적인 유동 클러스터 탐지 기법을 제시하고, 이를 서울시 대중교통 통행 데이터에 적용하여 유의미한 유동 통행 클러스터를 도출하고자 한다. 사례 분석 결과, 서울 전체에 걸쳐 있는 다양한 대중교통 통행 클러스터를 도출할 수 있었고, 특히 공간상에서는 인접하지만 서로 다른 교통수단과 노선 하에서 이루어진 개별 유동들을 하나의 유동 통행 패턴으로 탐지할 수 있었다, 더 나아가, 일반적인 빈도분석으로는 뚜렷하게 나타나지 않지만 공간적으로 인접한 여러 다발의 유동이 모였을 때 유의미한 통행량을 가지게 되는 주요 통행 패턴을 포착할 수 있었다. 본 연구는 유동 현상을 분석하는데 중요한 방법론적 시사점을 제시하고 있으며, 제시된 알고리즘은 향후 보다 진보된 유동 클러스터링 기법을 개발하는데 필요한 기초 결과로 활용될 수 있을 것으로 기대된다.