Use of psychrometers, capacitive sensors and vapour transfer technique to determine the water retention curve of compacted bentonite

Abstract

The FEBEX large-scale test simulating an underground repository of nuclear waste excavated in granite was dismantled after 18 years of operation. The engineered barrier between the heaters and the host rock consisted of compacted blocks of FEBEX bentonite which were retrieved during dismantling. The water content, dry density and suction of some of these blocks were measured at the laboratory and retention curves (WRC) were inferred from these values. The WRC of samples trimmed from the blocks was also determined using the vapour transfer technique. The results obtained with both methodologies were compared with the WRC obtained previously for the reference untreated FEBEX bentonite. The results are comparable, which indicates, on the one hand, that both methodologies give consistent results and, on the other, that the water retention capacity was not altered by 18 years operation under barrier conditions.