The high-level nuclear waste, HLW, from Swedish and Finnish reactors will be deposited in crystalline rock at depths around 500 m. The waste is enclosed in steel canisters protected against corrosion by a 5 cm thick copper shell, which ensures a lifetime far longer than 100 000 years. Should some canister be breached any leaking nuclides will have decayed to so low activity that even if they reached the biosphere, they would cause minimal risk to humans. The cost of the copper is significant. The dismantling of the nuclear reactors, with induced activity must also be disposed of and this waste volume is much larger than that of the HLW, which makes it impossible to protect it in the same way. This paper explores if by locating the waste at larger depth where the ground water is more saline, and where the hydraulic conductivity of the rock is lower up-flow of contaminated water can be ensured to be negligible because the denser water at larger depth counteracts up-flow due to negative buoyancy. Several processes that could cause local up-flow are addressed, such as infiltration of meteoric water, impact of surface topology, heat production of the waste, geothermal gradient, salinity gradient, hydraulic conductivity heterogeneities and salt migration between seeping water and salt in matrix pore water. Flow and transport simulations using data from extensive field investigations over more than ten years with scores of km deep boreholes suggest that a HLW repository at around one km depth may be sufficient to hinder up-flow to the biosphere.

中文翻译：

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咸水地下水抵消了污染物的上流——对放射性核素储存库的影响？

来自瑞典和芬兰反应堆的高放核废料 HLW 将沉积在 500 m 深处的结晶岩中。废物被封装在钢罐中，并用 5 厘米厚的铜壳防止腐蚀，确保使用寿命远远超过 10 万年。如果某个罐子被破坏，任何泄漏的核素都会衰变到如此低的活性，即使它们到达生物圈，对人类造成的风险也很小。铜的成本很高。具有诱发活动的核反应堆的拆除也必须进行处理，并且这种废物量比高放废物大得多，这使得不可能以同样的方式对其进行保护。本文探讨了如果将废物放置在地下水含盐量较高且岩石导水率较低的较深位置，是否可以确保污染水的上升流可以忽略不计，因为较大深度的密度较大的水会抵消- 由于负浮力而产生的流动。讨论了可能导致局部上升流的几个过程，例如大气水的渗透、表面拓扑的影响、废物的产热、地温梯度、盐度梯度、水力传导率不均匀性以及基质孔隙中渗透水和盐之间的盐迁移水。使用十多年来对数十公里深的钻孔进行的广泛现场调查的数据进行的流动和传输模拟表明，大约一公里深度的高放废物储存库可能足以阻碍向上流到生物圈。