深地層最終處置場緩衝材料小型熱-水耦合實驗之分層含水量量測改善

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Title:	深地層最終處置場緩衝材料小型熱-水耦合實驗之分層含水量量測改善
Authors:	林柏吾;Bor-Wu-Lin
Contributors:	土木工程學系
Keywords:	深地層處置;緩衝材料;TDR時域反射法;有限元素分析;熱-水耦合效應
Date:	2017-08-24
Issue Date:	2017-10-27 12:18:56 (UTC+8)
Publisher:	國立中央大學
Abstract:	核能發電為各國主要電力來源之一，但由於核能發電所產生之用過核子燃料具有高度放射性，且燃料棒內部核種其半衰期長達千百年乃至數十萬年，其衰變過程中所伴隨之衰變熱(Heat decay)，會形成一定範圍的溫度場效應。國際間目前對於用過核子燃料之最終處置方式一致採用「深層地質處置」(Deep Geologic Disposal)概念，並以工程障壁系統(Engineered Barrier System ,EBS)阻滯放射性核種之遷移，使其達成與人類生活圈完全隔離之設計目標，最終處置場之主要功能為利用緩衝材料所具備之功能性質包括高回脹潛能、低水力傳導特性、適當的熱傳導性以及遲滯核種遷移能力，以阻滯及延緩高放射性核種之遷移，而放射性廢棄物深地層處置場近場與遠場的演化程序主要受到四大因素所影響，包含T熱學(Thermal)、H水力(Hydraulic)、M力學(Mechanical)、C化學(Chemical)等因素，常為兩項或兩項以上交互作用，簡稱為T-H-M-C耦合效應，進而影響最終處置場之預期功能。本研究針對T-H耦合效應將實驗分為兩部份，首先實驗上使用TDR時域反射法含水量即時監測系統進行SPV200膨潤土之電學性質量測，以及進行TDR感測器之改良，再針對深地層處置場內緩衝材料周圍地下水回注近場環境後之再飽和狀態，提出以實驗室小型實驗與模擬分析。SPV200膨潤土之電學性質量測實驗發現在高含水量且溫度增加下，TDR波型受高導電度影響出現波型衰減情形，因此本研究使用保鮮膜與熱縮管兩種絕緣材料進行鎢鋼棒感測器表層絕緣處理，測試後發現保鮮膜絕緣鎢鋼棒擁有良好的絕緣能力。而在分層含水量監測實驗中觀察到25 ℃系統與40 ℃系統之膨潤土浸水後，底部試體體積含水量有高於飽和膨潤土體積含水量理論界限值47%之情況，原因為膨潤土具有高回脹能力，吸水後體積產生膨脹，於體積固定之模具內，下層之高飽和度之膨潤土吸水膨脹後向上擠壓上層低飽和度膨潤土，導致膨潤土產生擠壓變形，使孔隙體積與土壤顆粒體積發生改變。膨潤土試體之位移量與飽和度歷時分析結果其趨勢與ABAQUS有限元素分析模擬趨勢相符，乾密度與相對位移成正比關係，與飽和度及孔隙比成反比關係，顯示本研究建置之TDR分層含水量監測量測系統能夠有效進行膨潤土試體與TH耦合下之體積含水量歷時監測。 ;Nuclear power which is used as each countrasies one of the main sources of electricity, but the Nuclear power plant produces highly radioactive sSpent nNuclear fFuel eventually., tThe fuel rods haveinside nuclear half-life of thousands or even hundreds of thousands of years, and . Tthe decay of the heat generated by spent nuclear fuel in decay process, will form aaffect the environment in a certain range of temperature field effect. Thus, most countries use the concept of Internationally, the use of nuclear fuel for the final disposal of the nuclear fuel infinal use of "deep geological disposal" , and the migration of radioactive nuclei was blocked bywith Engineered Barrier System (EBS) to reach the completely isolatedtion from with the human life circle design goals. TheOne of the main functionobjective of EBS the final disposal site is the use ofapplying the buffer material with the functional properties including high expansion potential, low hydraulic conductivity characteristics, appropriate thermal conductivity, and hysteresisdecreasing nuclear migration ability to block and delay the migration of highly radioactive nuclear species, and t. The evolution of near-field and far-field in deep-site treatment of radioactive wasteEBS, however, isare mainlystill affected by four factors, including Thermal, Hydraulic, Mechanical, and Chemical and other factors, influences. Tthese factors are often two or more interactionsed, referred to as T-H-M-C coupling effect, and thus affecting the fexpected functionality of the final disposal of the expected function. In this study, the experiment was divided into two parts for the T-H coupling effect. First, we use the TDR time domain reflection (TDR) method tois employed to monitor the electrical properties of SPV200 bentonite, as well as the improvement of the TDR sensor. This research haveThen a small scale laboratory experiment and a the related simulation analysis of the re-saturation of bentonite state under T-H coupling of were conductedthe groundwater around the near-field environment. The second part is to study the relationship between the decay heat generated by the waste tank and the water-thermal coupling(T-H coupling) state formed by the groundwater entering the near-field environment. Three TDR sensors with a resolution of 1 cm were embedded in the bentonite samples. The samples were immersed in 25 ℃, 40 ℃, 60 ℃ three kinds of constant temperature water tank system for 120 hours to remove and observe the test Body flooding condition. SPV200 bentonite electrical properties of the testwas found to have high electrical conductivitythat in as high water content bentonite, TDR wave with theand temperature increase. increase began to wave attenuation phenomenon, In this study,T the uses of plastic wrap and heat shrinkable two kinds ofas coating materials for the TDR probe were therefore proposed to monitor the layer volumetric water content of the bentonite as the re-saturation experiment. The results stated that insulating materials for tungsten steel bar sensor surface insulation treatment. Insulation treatment, the test found that plastic wrap tungsten steel rods have good insulation capacity and the amount of dielectric constant measured close to the SPV200 bentonite curve, so choose plastic film insulation tungsten steel bar under different temperature systems under the layered water content monitoring experiment.the plastic wrap can maintain the sensitivity of the measurement. In the re-saturation experiment of bentonite under T-H couplingstratified water content monitoring experiment, it was observed that the volumeetric water content of the bentonite in the bottom layer was higher than that of the theoretical saturated bentonite volume water contentone of (47%) when the bentonite was immersed from the bottom in the 25 ℃ and 40 ℃ systems. The reason is that the bentonite has high swelling ability, the volume of Bentonite expansion after water absorptionre-saturated. In the volume of the fixed mold, tThe bottom lower layer of high degree of saturated bentonite extruded upper layer of low saturation bentonite, resulting in bentonite extrusion deformation,. tVhe poreoid volume and dry densitysoil particle volume changes. TheT trends of the displacement and saturation of the bentonite sample isare consistent with thatthe results of the ABAQUS finite element analysis, . tThe dry density is proportional to the relative displacement, whichwhile it is inversely proportional to the saturation and porevoid ratio. It is showsn that the stratification of this study The moisture content monitoring and measuring systemusing TDR canis effectively carry out the monitoring of the volume water content of bentonite test specimen in T-H coupling small scale experiment.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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