Development and preliminary tests of Mini-MACRO (MAss transport Characterization in host ROck)

Takasu, Tamio*; Maekawa, Keisuke  

It is necessary for safety assessment of high-level radioactive waste geologic disposal to understand groundwater flow in deep underground accurately. Groundwater flow in the coastal area especially considered to be quite complex that involves density and hydraulic gradient driven flow of freshwater and seawater. Furthermore, bentonite, which is one of the favored engineered barrier materials, may not swell very well in seawater as it does in freshwater, and therefore may not provide a reliable seal if salinity is high enough. Therefore it is important to understand saltwater behavior in deep underground. In order to understand the behavior of seawater intrusion into freshwater in deep underground, we constructed a laboratory equipment "Mini-MACRO" named after the original large scale MACRO (MAss transport Characterization in host ROck) and aimed to increase a precision and efficiency of experiment. In this report we summarize the procedures of the equipment construction and the results of preliminary tests of saltwater intrusion into a freshwater body.