Most of the radioactive wastes generated during the nuclear fuel processing activities conducted by KEPCO Nuclear Fuel Co., Ltd. are classified as the categories of intermediate and low-level radioactive waste. These radioactive waste materials are intended for permanent disposal at a designated disposal site, adhering strictly to the waste acceptance criteria. To facilitate the safe transportation of radioactive waste to the disposal site, it is necessary to ensure that the waste drums maintain a level of criticality that complies with the waste acceptance criteria. This necessitates the maintenance of subcritical conditions, under immersion or optimal neutron moderation conditions. This paper presents a criticality safety assessment of concrete radioactive waste under the most conservative conditions of immersion and moderation conditions for waste drums. Specifically, In order to send radioactive waste, which is the subject of criticality analysis, to a disposal facility, pre-processing operations must be performed to ensure compliance with waste accepatance criteria. To meet the physical characteristics required by the accepance criteria, particles below 0.2 mm should not be included. Thus, a 0.3 mm sieve is used to separate particles lager than 0.3 mm, and only those particles are placed in drums. The drums should be filled to achieve a filling ratio of at least 85%. A criticality analysis was conducted using the KENO-VI of SCALE. The Criticality Safety Analysis Results of varying the filling ratio of concrete drums from 85% to 100% presented in an effective multiplication factor of 0.22484. Additionally, the effective multiplication factor presented to be 0.25384 under the optimal moderation conditions. This demonstrates full compliance with the USL and criticality technology standards set as 0.95.

In KNF, fuel performance analysis modules were developed to predict the overall behavior of a fuel rod under normal operating conditions. Their main focus is to provide information on initial conditions prior to dry storage. Potential degradation mechanisms that may affect sheath integrity of spent CANDU fuel during dry storage are: creep rupture under internal gas pressure, sheath oxidation in air environment, stress corrosion cracking, delayed hydride cracking, and sheath splitting due to UO2 oxidation for a defective fuel. To upgrade the developed modules that address all the damage mechanisms, the first step was a review of the available technical information on phenomena relevant to fuel integrity. The second step was an examination of the technical bases of all modules, identify and extend the ranges of all modules to required operating ranges. The 300°C spent CANDU fuel sheath temperature metric for dry storage ensures spent CANDU fuel element integrity from the failure mechanisms of creep rupture, oxidation and stress corrosion cracking at a failure probability of 2×10-5 for a dry storage time of 100 years. The 300°C sheath temperature metric for dry storage has relatively a lower failure rate than the target criteria for dry storage of spent LWR fuel. Although different modes of failure were treated separately for simplicity, ignoring possible synergistic effects, these results are conservative because of the conservative assumptions that have been made for evaluating spent fuel element conditions, and because of the inherent conservatism of the applied models. Additional conservatism of the model comes from the fact that isothermal conditions do not prevail in actual storage conditions. Further R&D being considered includes acquisition of new functional models to implement overall fuel behavior evaluation and cover spent CANDU fuel in dry storage, and upgrades of the analysis module to achieve sufficient accuracy in key output parameters. The developed modules provide a platform for research and industrial applications, including the design of fuel behavior experiments and prediction of safe operating margins for spent CANDU fuel.

Currently, in the United States, Spent Nuclear Fuel (SNF) is stored at the Independent Spent Fuel Storage Installations (ISFSIs) at 73 Nuclear Power Plants (NPPs). The SNF inventory stored on-site either in pools or dry storage was 84,500 MTU in 2020. The inventory stored in on-site dry storage facilities was 39,207 MTU (46% of the total), and it is growing at a rate of approximately 3,500 MTUs per year. However, because a site for geologic repository for permanent disposal of SNF has not been constructed in the U.S., the SNF will need to be stored in dry storage facilities across the U.S. for a much longer period of time than originally planned. During this time, the dry storage facilities could experience earthquakes of a different magnitude than the one for which they were originally designed. However, there is little data on the response of SNF inside dry storage systems to seismic loads in the U.S., and the various gaps and nonlinearities between storage containers, canisters, baskets, aggregates, and fuel make it very difficult to evaluate by analytical methods. Therefore, a full-scale shake table test is being planned as an international joint research project led by Sandia National Laboratories (SNL) in the U.S. In Korea, KNF decided to participate in this seismic test through the project of SNF integrity evaluation under road and sea normal transportation conditions organized by KNF and conducted by KORAD, KAERI, and Kyung-Hee University, and has provided the KNF 17ACE7 and PLUS7 test assemblies for the tests to SNL. The test will be conducted at the LHPOST6 shake table test facility operated by University of California in San Diego (UCSD) from 2023 to 2024, with the participation of KNF, CRI, and KAERI in Korea. The test units consist of a NUHOMS 32 PTH2 canister, a mockup of a generic vertical cask, a mockup of a generic horizontal storage module, 4 surrogate fuel assemblies, and 28 dummy assemblies. The seismic inputs for the tests will consist of ground motions (acceleration time histories) representative of hard rock, soft rock, and soil sites and seismic conditions in moderately tectonically active Central and Eastern US and highly tectonically active Western US. Ground accelerations for soft rock and soil conditions will be developed taking in account soil-structure interaction. Not only is this test almost impossible to conduct independently in Korea in terms of scale, facilities and costs, but it is also considered an essential test for those of us who are preparing for dry storage of spent nuclear fuel, given the increasing social concern about earthquakes due to the recent earthquake in Turkey.

Maintaining fuel sheath integrity during dry storage is important. Intact sheath acts as the primary containment barrier for both fuel pellets and fission products over the dry storage periods and during subsequent fuel handling operations. In KNF, in-house fuel performance code was developed to predict the overall behavior of a fuel rod under normal operating conditions. It includes the analysis modules to predict temperature, pellet cracking and deformation, sheath stress and strain at the mid-plane of the pellet and pellet-pellet interfaces, fission gas release and internal gas pressure. The main focus of the code is to provide information on initial conditions prior to dry storage, such as fission gas inventory and its distribution within the fuel pellet, initial volumes of storage spaces and their locations, radial profile of heat generation within the pellet, etc. To upgrade the developed code that address all the damage mechanisms, the first step was a review of the available technical information on phenomena relevant to fuel integrity. Potential degradation mechanisms that may affect sheath integrity of CANDU spent fuel during dry storage are: creep rupture under internal gas pressure, sheath oxidation in air environment, stress corrosion cracking (SCC), delayed hydride cracking (DHC), and sheath splitting due to UO2 oxidation for a defective fuel. The failure by creep rupture, SCC or DHC is in the form of small cracks or punctures. The failure by sheath oxidation or sheath splitting due to UO2 oxidation results in a gross sheath rupture. The second step was to examine the technical bases of all modules of the in-house code, identify and extend the ranges of all modules to required operating ranges. This step assessed the degradation mechanisms for the fuel integrity. The objective of this assessment is to predict the probability of sheath through-wall failure by a degradation mechanisms as a function of the sheath temperature during dry storage. Further improvements being considered include upgrades of the analysis module to achieve sufficient accuracy in key output parameters. The emphasis in the near future will be on validation of the inhouse code according to a rigorous and formal methodology. The developed models provide a platform for research and industrial applications, including the design of fuel behavior experiments and prediction of safe operating margins for CANDU spent fuel.

Prior to the investigations on fuel degradation it is necessary to describe the reference characteristics of the spent fuel. It establishes the initial condition of the reference fuel bundle at the start of dry storage. In a few technology areas, CANDU fuels have not yet developed comprehensive analysis tools anywhere near the levels in the LWR industry. This requires significantly improved computer codes for CANDU fuel design. In KNF, in-house fuel performance code was developed to predict the overall behavior of a fuel rod under normal operating conditions. It includes the analysis modules to predict temperature, pellet cracking and deformation, clad stress and strain at the mid-plane of the pellet and pellet-pellet interfaces, fission gas release and internal gas pressure. The main focus of the code is to provide information on initial conditions prior to dry storage, such as fission gas inventory and its distribution within the fuel pellet, initial volumes of storage spaces and their locations, radial profile of heat generation within the pellet, etc. Potential degradation mechanisms that may affect sheath integrity of CANDU spent fuel during dry storage are: creep rupture under internal gas pressure, sheath oxidation in air environment, stress corrosion cracking, delayed hydride cracking, and sheath splitting due to UO2 oxidation for a defective fuel. To upgrade the developed code that address all the damage mechanisms, the first step was a review of the available technical information on phenomena relevant to fuel integrity. The second step was an examination of the technical bases of all modules of the in-house code, identify and extend the ranges of all modules to required operating ranges. Further improvements being considered include upgrades of the analysis module to achieve sufficient accuracy in key output parameters. The emphasis in the near future will be on validation of the in-house code according to a rigorous and formal methodology. The developed models provide a platform for research and industrial applications, including the design of fuel behavior experiments and prediction of safe operating margins for CANDU spent fuel.

가상 현실은 몰입감과 존재감을 극대화시킬 수 있다는 장점이 있어 비디오 게임, 교육, 치료 목적을 가진 다양한 콘텐츠에 널리 활용되고 있다. 또한 GearVR, DayDream, Occulus Quest 2 등의 HMD 등이 개발됨에 따라 가상 현실은 널리 보급되었다. 그러나 이러한 장비들을 사용하면 사용자가 실제 물리적인 세계를 볼 수 없다는 단점이 있어 실제 물체와 충돌하거나 넘어지는 위험한 상황에 빠질 수 있다. 만약 사용자가 시스 루 HMD를 사용하면 실제 물리적인 세계를 볼 수 있으므로 물체를 피할 수 있고 이러한 위험을 피할 수 있 는데 이러한 시스루 HMD는 광학 기반 방식이나 비디오 기반 방식으로 분류된다. 이러한 광학 기반 HMD는 렌즈를 통과하는 물리적 물체들을 볼 수 있지만 비용 문제가 있으며 비디오 기반 HMD는 비용과 카메라의 원본 이미지에 다양한 가상 효과를 추가할 수 있다는 장점이 있다. 본 논문은 이러한 장점들을 활용하여 저 렴한 비용으로 게임에 활용될 수 있도록 개발된 시스루 HMD를 설명하였으며 해당 HMD를 활용하는 게임 을 설명하였다. 본 논문을 통하여 개발된 비디오 시스루 HMD를 통해 더 많은 사용자가 저렴한 비용으로 혼합 현실 기반 게임을 즐길 수 있을 것으로 예상된다.

벼메뚜기는 분류학적으로 메뚜기목(Orthoptera), 메뚜기과(Acrididae)에 속하는 곤충으로 작물에 피해를 주는 해충으로 인식하고 있지만 예로부터 단백질 보충을 위하여 채집하여 튀기거나 볶음요리 로 이용해 왔다. 벼메뚜기는 갈색거저리, 쌍별귀뚜라미 등과 함께 식품공전에 등록되어 있으나 1년 1세대로 가을철에 채집하여 이용하는 실정으로 공급확대에 한계가 있다. 최근 우리나라에서 벼메뚜기를 사육하고자 하는 농가와 다양한 용도로 가공을 통해 이용하려는 수요가 점차 증가하고 있으나 연중사육기술이 개발되지 않아 대량사육하는 농가가 거의 없는 실정이다. 이에 벼메뚜기의 연중대량사육기술 뿐만 아니라 인공사료 및 자동화 사육시설 개발에 따른 생산비 절감 기술 개발이 필요한 실정이다. 벼메뚜기의 먹이로는 여름작물로 옥수수, 수단그래스, 겨울작물로 밀, 보리 등의 볏과작물이 있으며 많은 양의 생엽과 발육에 적합한 작물의 선발 및 볏과작물의 통곡실 가루를 이용한 인공사료의 개발로 먹이공급 부족 시 15~20일 급여 가능하며, 벼메뚜기 사육시설로 단독형, 연결형, 절충형 등의 사육시설을 개발하여 연결형 사육시설의 수확량과 생존율이 가장 높았으며, 예취 급이 노동력이 단독형의 16% 소요되었다.

Porcine spermatogonial stem cells (SSCs) prefer three-dimensional (3D) culture systems to 2D ones for the maintenance of self-renewal. Of the many 3D culture systems, agar-based hydrogels are candidates for supporting porcine SSC self-renewal, and there are various types of agar powder that can be used. In this study, we sought to identify an agar-based 3D hydrogel system that exhibited strong efficacy in the maintenance of porcine SSC self-renewal. First, 3D hydrogels with different mechanics were prepared with various concentrations of Bacto agar, lysogeny broth (LB) agar, and agarose powder, and the 3D hydrogel with the strongest alkaline phosphatase (AP) activity and greatest increase in colony size was identified for the different types of agar powder. Second, among the porcine SSCs cultured in the different 3D hydrogels, we analyzed the colony formation, morphology, and size; AP activity; and transcription and translation of porcine SSC-related genes, and these were compared to determine the optimal 3D hydrogel system for the maintenance of porcine SSC self-renewal. We found that 0.6% (w/v) Bacto agar-, 1% (w/v) LB agar-, and 0.2% (w/v) agarose-based 3D hydrogels showed the strongest maintenance of AP activity and the most pronounced increase in colony size in the culture of porcine SSCs. Moreover, among these hydrogels, the strongest transcription and translation of porcine SSC-related genes and largest colony size were detected in porcine SSCs cultured in the 0.2% (w/v) agarose-based 3D hydrogel, whereas there were no significant differences in colony formation and morphology. These results demonstrate that the 0.2% (w/v) agarose-based 3D hydrogel can be effectively used for the maintenance of porcine SSC self-renewal.

This studies was conducted to compare functional diversity of terrestrial arthropods in commercial apple orchards under conventional and organic practices. We collected terrestiral arthropods using pitfall traps in four conventional and seven organic apple orchards from April to October, 2012-2014. Sampled arthropods were identified at the species level and then classified three functional groups (detritivores, herbivores and beneficial arthropods included pollinators, parasitoids and predators). Biodiversity was analyzed with species richness, abundance and shannon index for each group and compared between conventional and organic orchards. In results, species richness of detritivores and benefical arthropods were higher in organic orchards than in conventional orchards (detritivores: t=-2.68, df=9, P=0.03; beneficial arthropods: t=-3.98, df=9, P=0.003). Organic orchards showed significant difference at abundance of beneficial arthropods (t=-3.33, df=9, P=0.008) and higher shannon index at detritivores (t=-2.36, df=9, P=0.04) than conventional orchards. However, all biodiversity indices of herbivores were not significantly different between conventional and organic orchards at 95% confidence level.

저장조에 위치한 사용후핵연료는 가혹한 원자로 조건에 의해 구조적 건전성이 와해되므로 외력에 취약하다. 따라서 운반 및 취급 중 사고 상황이 고려되어야 한다. 극단적인 경우, 핵연료 취급 중 사고로 인해 핵연료 저장조에서 핵연료집합체 낙하 가 발생할 수 있다. 이러한 사고 상황 하에서 연료봉 파손 등을 평가하기 위해서 수조에 충돌할 때 발생하는 충돌력을 분석 할 필요가 있다. 이는 핵연료가 수조 바닥에 충돌할 때의 속도를 입력으로 하여 평가될 수 있다. 연료봉이 핵연료 중량 및 부 피의 대부분을 차지하고 있으므로, 연료봉 다발은 수중 항력을 예측하는데 중요한 역할을 한다고 볼 수 있다. 본 연구에서는 3×3 의 짧은 연료봉 다발을 모델로 사용하여 수중에서 낙하할 때 받는 수력을 계산하였고, 이를 전산모사와의 비교를 통하 여 검증하였다. 본 방법론을 사용후핵연료 건전성 평가에 적용할 수 있을 것으로 기대된다.

This studies was conducted to define community structure and diversity of epigeal spiders in apple orchards under different farming practices (organic and conventional). In 11 commercial apple orchards, epigeal spider community structure was investigated during 2012-2014 (3 orchards, 2012; 3 orchards, 2013, 5 orchards, 2014). Epigeal spiders were collected by pitfall traps from April to October, 2012 in Danyang-gun, Chungcheongbuk-do; 2013 in Muju-gun, Jeollabuk-do; 2014 in Cheongsong-gun and Uiseong-gun, Gyeongsangbuk-do, Korea. Sampled spiders were identified to the species level. Biodiversity was analyzed with species richness (total numbers of spider species), abundance (total numbers of individuals) and Shannon-Wiener diversity index (H΄) for each site and compared between organic and conventional orchards. In all regions, abundance of the spider communities were relatively higher in organic orchards than in conventional orchards. But, no significant difference in species richness and specie diversity (H΄) between organic and conventional orchards. Lycosidae was the most dominant family in all orchards regardless farming practices. However, Linyphiidae dominated in organic orchards only. The most dominant species were Pardosa laura (Lycosidae), Erigone koshiensis (Linyphiidae) in organic, Piratula procurvus (Lycosidae) in conventional orchards.