On thermohydrologic conditions near high‐level nuclear wastes emplaced in partially saturated fractured tuff: 1. Simulation studies with explicit consideration of fracture effects
On thermohydrologic conditions near high‐level nuclear wastes emplaced in partially saturated fractured tuff: 1. Simulation studies with explicit consideration of fracture effects
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DOI：
10.1029/wr026i006p01235
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发表时间：
1990-06
影响因子：
5.4
通讯作者：
K. Pruess;J. S. Wang;Y. Tsang
中科院分区：
文献类型：
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作者：
K. Pruess;J. S. Wang;Y. Tsang
我们对部分饱和的裂隙多孔岩石中热量、液态水、蒸汽和空气的同时传输进行了建模研究。选择地层参数作为丝兰山凝灰岩 Topopah Spring 单元潜在核废料储存库地点的代表。裂缝的存在使得传输问题在流动几何和物理方面都变得非常复杂。用于流动计算的数值模拟器考虑了大多数被认为在多相流体和热流中很重要的物理效应。它可以处理相变、成分消失和断裂面毛细管不连续性中出现的极端非线性。我们对核废料罐的无限线性串周围的区域进行建模，同时考虑离散裂缝和多孔基质。研究发现，废物包附近的热水文条件很大程度上取决于裂缝的相对渗透率和毛细管压力特征，而这些特征目前尚不清楚。如果假定保留在排水裂缝的粗糙壁上的液体是可移动的，则可以预测强烈的热管效应。在这些条件下，主岩直到就位孔为止都将保持两相状态，地层温度将达到 100°C 附近的峰值。如果假设液体不能沿着排干的裂缝移动，则废物包周围的区域预计会干涸，并且地层温度将上升到 200°C 以上。如果安放孔保持开放和通风，则可以去除大部分废热，而不是回填和密封安放条件。将我们的模型预测与齐默尔曼及其同事报告的原位加热器实验的观察结果进行比较，发现了一些有趣的相似之处。然而，为了进行定量评估，需要额外仔细控制的实验室和现场实验。
We have performed modeling studies on the simultaneous transport of heat, liquid water, vapor, and air in partially saturated, fractured porous rock. Formation parameters were chosen as representative of the potential nuclear waste repository site in the Topopah Spring unit of the Yucca Mountain tuffs. The presence of fractures makes the transport problem very complex, both in terms of flow geometry and physics. The numerical simulator used for our flow calculations takes into account most of the physical effects believed to be important in multiphase fluid and heat flow. It has provisions for handling the extreme nonlinearities that arise in phase transitions, component disappearances, and capillary discontinuities at fracture faces. We model a region around an infinite linear string of nuclear waste canisters, taking into account both the discrete fractures and the porous matrix. Thermohydrologic conditions in the vicinity of the waste packages are found to depend strongly on relative permeability and capillary pressure characteristics of the fractures, which are unknown at the present time. If liquid held on the rough walls of drained fractures is assumed to be mobile, strong heat pipe effects are predicted. Under these conditions the host rock will remain in two-phase conditions right up to the emplacement hole, and formation temperatures will peak near 100°C. If it is assumed that liquid cannot move along drained fractures, the region surrounding the waste packages is predicted to dry up, and formation temperatures will rise beyond 200°C. A substantial fraction of waste heat can be removed if emplacement holes are left open and ventilated, as opposed to backfilled and sealed emplacement conditions. Comparing our model predictions with observations from in situ heater experiments reported by Zimmerman and coworkers, some intriguing similarities are noted. However, for a quantitative evaluation, additional carefully controlled laboratory and field experiments will be needed.