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A Case Study on the Remediation of Embedded Piping of Trojan Decommissioning NPP
Jihwan Yu,Hyung-woo Seo,Gi-lim Kim,Hyein Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Trojan Nuclear Power Plant (NPP), a four-loop PWR designed by Westinghouse and owned by Portland General Electric (PGE), reached its initial threshold in 1975 and was operational until November 1992. PGE received a Possession Only License from the NRC in May 1993. In 1995, limited decommissioning activities began at the Trojan, including the completion of a large components removal project to remove and dispose of four steam generators and pressurizers from the containment building. In April 1996, the NRC approved a plan to dismantling the Trojan NPP and began more aggressive component removal activities. At the end of 1998, part of the radioactive drainage system began to be removed, and embedded piping decontamination and survey activities began. Trojan NPP has more than 8,840 m of contaminated pipelines throughout the power block. Most of Trojan NPP’s contaminated embedded piping can generally be divided into four categories drainage piping, ventilation ducts, buried process piping, and other items. For the Trojan NPP, the complete removal of contaminated and embedded piping without damaging the building would have significantly increased costs due to the structural considerations of the building and the depth of the embedded pipe. Therefore, Trojan NPP has chosen to conduct the Embedded Pipe Remediation Project (EPRP) to clean and in situ survey of most of the embedded piping to meet the Final Site Survey (FSS) acceptance criteria, with much success. This study provides a discussion of EPRP activities in the Trojan NPP, including classification and characterization of affected piping, modeling of proposed contamination acceptance criteria, and evaluation of various decontamination and survey techniques. It describes the decontamination tools, techniques, and survey equipment and the condition of work and cost estimate costs used in these projects. To identify embedded piping and drains at the Trojan NPP, based on frequent site surveys, plan sketches showing an overview of system flow paths and connections and database were developed to identify drain inputs and headers. This approach effort has been a successful method of remediation and site survey activities. The developed database was a valuable asset to the EPRP and a Work Breakdown Structure (WBS) code was assigned to each drains and headers, allowing the embedded piping to be integrated into the decommissioning cost estimation software (Decon. Expert) and schedule, which aided in decommissioning cost estimation. Also, regular database updates made it easy to check the status of the decommissioning project data. The waste system drain at Trojan NPP was heavily contaminated. The goal of the remediation effort is to completely remove all removable contamination and to reduce the fixed contamination below the decided contamination acceptance criteria. Accordingly, Hydrolysis, Media blast, Chemical decontamination and Pipe removal were considered as remediation option. Trojan NPP’s drainage pipe decontamination option did not cause a significant corrosion layer inside the pipe and media blast was chosen as the main method for stainless steel pipe. In particular, the decommissioning owner decontaminates most of the embedded piping in-situ to meet the FSS acceptance criteria for economic feasibility in Trojan NPP. The remaining pipe was filled with grout to prevent leaching and spreading of contamination inside the pipe. In-situ decontamination and survey of most of these contaminated pipes are considered the most cost-effective option.
Jihwan Oh,김범상 한국유변학회 2020 Korea-Australia rheology journal Vol.32 No.1
Novel gelatin-containing polymer hydrogels that can be used as mucoadhesive delivery systems were developed. Poly(acrylic acid) hydrogels were modified by copolymerizing gelatin as adhesion promoter, to improve the adhesion to the mucus layer and the synthesized copolymer of acrylic acid (AA) and methacrylated gelatin (GelMA) were designated as P(AA-co-GelMA). The pH-sensitivity and the mucoadhesive property of the P(AA-co-GelMA) hydrogel were investigated as carries of an oral protein delivery system activated by pH changes of the human GI tract. There was a drastic change in the weight swelling ratio of P(AA-co-GelMA) hydrogels at a pH of around 5, that is, low swelling ratios at a pH below 5, while high swelling ratios at a pH greater than 5. In addition, the swelling ratio increased at a pH above 5, when the AA content in the hydrogel increased. In mucoadhesive experiments using the rheometer, when the GelMA concentration in the P(AA-co-GelMA) hydrogel increased, the maximum force of detachment increased, indicating that the mucoadhesion of the hydrogel was improved. The P(AA-co-GelMA) hydrogels also showed a pH-responsive release behavior. The ratio of the cumulative amounts of Rh-B released from P(AA-co-GelMA) hydrogels at pH 2.6 to pH 7.0 increased, when the AA content in the hydrogel decreased.
Separation of tetrahydrofuran and water using pressure swing distillation: Modeling and optimization
Jihwan Lee,조정호,김동민,박상진 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.2
Computer simulations were performed to obtain highly pure tetrahydrofuran (THF) with over 99.9 mole%from the mixture of THF and water. Pressure swing distillation (PSD) was used since the azeotropic point between tetrahydrofuran and water can be varied with pressure. A commercial process simulator, PRO/II with PROVISION release 8.3, was used for the simulation studies. The Wilson liquid activity coefficient model was used to simulate the low pressure column, and the Peng-Robinson equation of state model was added to correct the vapor phase non-idealities for the modeling of the high pressure column. The most optimal reflux ratios and the most optimal feed stage locations that could minimize the total reboiler heat duties were determined.
The Two Koreas after U.S. Unipolarity: In Search of a New North Korea Policy
Jihwan Hwang 서울대학교 국제학연구소 2013 Journal of International and Area Studies Vol.20 No.1
The global and East Asian orders of power are now represented by China's economic, military, and diplomatic rise and America's decline. While U.S.-China relations represent a set of the most important variables in world politics, the meaning of China's rise is much greater on the Korean Peninsula. Given the recurring balance of power shift from the U.S. preponderance of power for the last two decades, it is necessary to rethink the security environment in the region. In this vein, South Korea may need to examine the meaning of the rise of China for the Korean Peninsula, especially with regard to the North Korean issue. In reality, China's rise has presented South Korea with a complex and difficult challenge in dealing with North Korea. As a result of the rise of China and changes in Chinese-North Korean relations, the North Korean problem can no longer be seen from the post-Cold War framework of the 1990s. North Korea is now a nation strongly dependent on and supported by a rising China. Thus, it is high time for South Korea to think again about its North Korea policy. The South Korean government needs to reassess the changing balance of power on the Korean Peninsula and seek a new North Korea policy that can increase its influence on North Korea.