Yoon Seok, Jeon Jun-Seo, Lee Gi-Jun
Disposal Safety Evaluation Research Division, Korea Atomic Energy Research Institute (KAERI), Daejeon, 34057, Republic of Korea.
Department of Geotechnical Engineering Research, Korea Institute of Civil Engineering and Building Technology (KICT), Goyang, 10223, Republic of Korea.
Heliyon. 2023 Jul 22;9(8):e18447. doi: 10.1016/j.heliyon.2023.e18447. eCollection 2023 Aug.
Bentonite buffer materials are important components of engineered barrier systems for the disposal of high-level radioactive waste produced during nuclear power generation. The design temperature of the buffer material is < 100 °C, and increasing the design temperature can reduce the required disposal area. This characteristic necessitates the evaluation of the thermal-hydraulic-mechanical properties of the buffer at temperatures above 100 °C to increase its target temperature. Therefore, the hydraulic properties of Gyeongju (KJ) bentonite buffer material were evaluated in this study, including the soil-water characteristic curve (SWCC) and hydraulic conductivity. An experimental system was manufactured to measure the suction and saturated hydraulic conductivity of KJ bentonite buffer material above 100 °C; the relative humidity of KJ bentonite buffer material was measured at 25-149 °C with an initial water content of 0, 0.06, and 0.12 under constant saturation conditions. The suction decreased as the temperature increased (10%-25% reduction at 99 °C-149 °C). The Van-Genuchten SWCC fitting parameters were also derived at 25 °C-149 °C using previously reported and newly generated experimental results, and the applicability of the modified Van-Genuchten SWCC model in this temperature range was verified. The hydraulic conductivity was proportional to temperature up to 100 °C, in agreement with the theoretical model results. Between 100 °C and 150 °C, the hydraulic conductivity increased nonlinearly because of molecular motion and structural changes inside the sample.
膨润土缓冲材料是用于处置核能发电过程中产生的高放废物的工程屏障系统的重要组成部分。缓冲材料的设计温度<100°C，提高设计温度可减少所需的处置面积。这一特性使得有必要评估缓冲材料在100°C以上温度下的热-水-力学性能，以提高其目标温度。因此，本研究对庆州（KJ）膨润土缓冲材料的水力学性能进行了评估，包括土-水特征曲线（SWCC）和水力传导率。制造了一个实验系统来测量KJ膨润土缓冲材料在100°C以上的吸力和饱和水力传导率；在恒定饱和度条件下，测量了初始含水量为0、0.06和0.12的KJ膨润土缓冲材料在25-149°C时的相对湿度。吸力随温度升高而降低（在99°C-149°C时降低10%-25%）。还利用先前报道的和新生成的实验结果，推导了25°C-149°C时的Van-Genuchten SWCC拟合参数，并验证了修正后的Van-Genuchten SWCC模型在该温度范围内的适用性。水力传导率在100°C以下与温度成正比，这与理论模型结果一致。在100°C至150°C之间，由于样品内部的分子运动和结构变化，水力传导率呈非线性增加。
