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RISS 인기검색어
- 검색키워드
- 저자 : ( Ryoichi Furuta ) (검색결과 1 건)
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( Hirofumi Nakayama ),( Yasuyuki Kimura ),( Takayuki Shimaoka ),( Ryoichi Furuta ),( Ichiro Hiura ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 심포지움 Vol.2017 No.1
Radioactive materials were widely spread as a result of a nuclear accident at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant initiated by the 2011 Tohoku Earthquake, which occurred on March 11. Radioactive decontamination work for the same is still underway. At the temporary storage sites, decontamination wastes are stored in flexible containers and gas-permeable waterproof sheets are used for capping to cover the waste. However, currently, 6 years after the accident, several capping sheets are being reported as damaged, raising concerns about the contamination of surrounding environment because of rain leaking through the capping sheet. Large puddles formed on top of the capping sheets are the main cause for their damage. The reported damages include tears in the capping sheet materials and separation of joints caused by the tension generated by the puddles. More than 1000 temporary storage sites have been constructed and more than 100,000 mountains have been built. At these sites, it is necessary to monitor the puddles formed on the capping sheets and inspect the resulting damages. Although visual inspection of temporary storage sites is currently being conducted approximately once a month, the number of temporary storage sites is vast and conducting inspection by climbing on degraded capping sheets involves a risk in terms of the safety of the workers. Therefore, this study investigates a monitoring method to locate a site with a high probability of damages on the capping sheets via measurement of the strain generated by the puddles on the sheets and using a drone to photograph and analyze the temporary storage sites. This study generated 3D models via SfM analysis of the images photographed by drones and aimed to develop a method to estimate the damage endangered area by estimating the stress and strain distribution with FEM using the coordinate data of the point groups forming the 3D models as the input data. The results of this study are as follows: Strain and stress generated by the puddles are concentrated at the edges of the puddles. For mock temporary storage site, we were able to confirm a strain of approximately 20% and stress of 9 MPa measured by adhering a strain gauge to the capping sheet. This is five times greater than 1.75 MPa, the self-standard value of the capping sheet strength set by the Japan Water Sealing Association, and therefore, monitoring of the sheet is considered to be of utmost importance. There was an increase in the strain and stress values near the vicinity of the puddle center; however, they were only about half of the values at the edges. Strain and stress distribution for mock temporary storage sites were calculated via FEM analysis. Because the measured results and the analytically calculated values were consistent in terms of the location and the degree of strain, we can infer that there is a constant validity and believe that it is possible to apply this to an actual site. The method developed in this study was applied for the detection of damage endangered area at an actual temporary storage site for decontamination waste in Fukushima. Concentration of the strain and stress near the top of the slope at the edge of the temporary storage site was confirmed and the strain value was recorded up to a maximum of 4%, while a maximum of 1.8 MPa was attained for the stress. These values slightly exceed 1.75 MPa, which is the self-standard tensile strength set by the Japan Water Sealing Association.
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