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Thermal Evaluation of Consolidation Storage Canister for Spent Nuclear Fuel
Taehyeon Kim,Eunjin Sim,Donghee Lee,Sunghwan Chung,Yongdeog Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
There have been a variety of issues related to spent nuclear fuel in Korea recently. Most of the issues are related to intermediate storage and disposal of spent nuclear fuel. However, recently, various studies have been started in advanced nuclear countries such as the United States to reduce spent nuclear fuel, focusing on measures to reduce spent nuclear fuel. In this study, a simple preliminary assessment of the thermal part was performed for the consolidation storage method which separates fuel rods from spent nuclear fuel and stores them. The preliminary thermal evaluation was analyzed separately for storing the spent fuel in fuel assembly state and separating the fuel rods and storing them. The consolidation storage method in separating the fuel rods was advantageous in terms of thermal conductivity. However, detailed evaluation should be performed considering heat transfer by convection and vessel shape when storing multiple fuel bundles simultaneously.
Calculation of Decay Heat in SNF Using the Latest ANSI/ANS-5.1 Method
Taehyeon Kim,Donghee Lee,Eunjin Sim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
In the 3rd revision of NUREG-0800, which was revised in 2007, the calculation method for decay heat in the design of the Ultimate Heat Sink (UHS) for a pressurized water reactor is recommended to be based on the ANSI/ANS-5.1 method. This method employs a more complex decay heat calculation formula compared to the one introduced in Branch Technical Position ASB 9-2, which was presented in the 2nd revision. While most of the variables for decay heat calculation in ANSI/ANS-5.1 can be inferred from the methods outlined in the appendices, determining the fractions of fission products is not straightforward despite their significant impact on the results. When reviewing documents that evaluate decay heat using the ANSI/ANS-5.1 method, it is observed that they often adopt a conservative approach by assuming that the fraction of the most influential fission product is 100%. In this study, the fractions of each fission product presented in LLNL’s 2016 report were used to calculate decay heat, and the results were compared with the ASB 9-2 method and ORIGEN code results. The comparison showed that ANS 5.1 tends to yield higher decay heat values than ANS 9-2, particularly at the reference time of 1M seconds, while ORIGEN-ARP generally produced lower values. Therefore, it is concluded that even when using the ANSI/ANS-5.1 method with the fractions of each fission product for decay heat calculations in spent nuclear fuel wet or dry storage facility assessments, it provides a sufficiently conservative thermal evaluation.
Scaled-Down Test Model Using CFD on the On-Site SNF Dry Storage Module
Taehyeon Kim,Donghee Lee,Kiyoung Kim,Sangil Ahn,Dong-gyu Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
Korea Hydro & Nuclear Power (KHNP) is currently developing a vertical concrete dry storage module for the dry storage of used nuclear fuel within nuclear power plants. This module is designed with a structure consisting of cylinders, which can block the ingress of external air, thereby preventing Chloride-Induced Stress Corrosion Cracking (CISCC). However, due to the presence of these cylinder structures, unlike conventional dry storage systems, it cannot directly dissipate heat to the external atmosphere, making thermal evaluation an important issue. The SF dry storage module being developed by KHNP is a massive concrete structure of approximately 20 m × 10 m × 7 m in size, employing a vertical storage system. To demonstrate the safety of such a large structure, there is no alternative to conducting experiments with scaled-down models. Furthermore, according to NUREG-2215 Section 5.5.4, it is explicitly mentioned that design-verification testing can be performed using scaled-down models. In this paper, a 1/4 scaled-down model was constructed to perform thermal performance verification experiments, and the effectiveness of this model was analyzed using Computational Fluid Dynamics (CFD) methods. The analysis results indicated that there was not a significant difference in terms of maximum concrete temperature and air outlet temperature. However, a considerable difference was observed in the canister surface temperature. Therefore, it is concluded that careful consideration of natural convection heat transfer is necessary for the full application of the scaled-down model.
Taehyeon Kim,Seung-Chul Lee,박우상 한국광학회 2020 Current Optics and Photonics Vol.4 No.2
A novel method is proposed for controlling the distance of an image plane in Fourier holograms using varifocal electric-field-driven liquid-crystal (ELC) lenses. Phase Fresnel lenses are employed to reduce the thickness and response time of the ELC lenses. The voltages applied to the electrodes of the ELC Fresnel lens are adjusted so that the lens has the same retardation distribution as an ideal lens. The focal length can be controlled by changing the retardation distribution with the applied voltages. Simulations were conducted for the image reconstruction of Fourier holograms with various focal lengths of the ELC Fresnel lenses. The simulation results indicate that the distance of the image plane can be properly controlled with the varifocal ELC Fresnel lens.