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.
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