ABOUT THE PERMEABILITY OF FAULTS AND FRACTURES IN CLAY FORMATIONS
Clay formations are being considered in a number of European countries as possible geological host rocks for radioactive wastes disposal. Risk analysis studies have pointed out that faulting of the formation followed by water intrusion could constitute a possible radioactivity release scenario. In this context field studies were undertaken to investigate fractures and faults in clay formations. The objectives of the present study, conducted on a number of samples taken from clay fractures, were: a) to date existing fractures where percolation of water has occurred, b) to study the diffusion profile on the various elements both sides of the fracture planes. The results are presented for a series of samples taken from the quarry front of a surface clay formation in central Italy, where a number of fractures exhibiting clear traces of percolation were investigated. The main achievements of the study were to point out which analyses are more effective to discriminate between perturbed clay, where elements have been diffusing, and unperturbed clay and to estimate the order of magnitude of the active lifetime of the percolation phenomenon. This ranged between some tens to some hundreds of years, depending on the considered profiles. Two types of element concentration profile were identified: Cs, Te, U, Fe, having Kd values strongly dependent on the redox conditions show a stepwise profile in correspondence to the redox front. Co, which is not affected by redox conditions of the medium, shows a more regular profile indicating a depletion near the water percolation plane.
Bibliographic Reference: 1985 INTERNATIONAL CLAY CONFERENCE, DENVER, COLORADO (USA), JULY 29-AUG. 5, 1985 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32297 ORA
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Record Number: 1989124015500 / Last updated on: 1987-01-01
Available languages: en