Hydrodynamic dispersion in a single fracture : final report on CRNL experiment
This report concerns the safe long-term disposal of radioactive waste by deep burial in stable fractured rock formations. Radio-nuclides from waste could return to the biosphere by leaching and dissolution of the waste-form, then transport by ground water. Two experiments were conducted, using 82Br as a conservative tracer, on a discrete fracture identified by hydraulic interference tests at approximately 100 m depth in moderately-fractured monzonitic gneiss. The selected fracture intersects two boreholes in a relatively horizontal attitude over a distance of about 10 m. Approximately dipole flow fields were used. The experiments were designed to minimise the mixing effects in both the injection and sampling intervals. A numerical model was developed including the effects of a dipole flow field with unequal injection and withdrawal flowrates and hydrodynamic dispersion within the fracture, modelled by a dispersion length. The wide variation of travel times in the dipole field was a major dispersal mechanism in these experiments, masking the effects of pure hydrodynamic dispersion and diffusion of tracer into stagnant water in pores in the rock surrounding the fracture.
Bibliographic Reference: EUR 11454 EN (1988)
Record Number: 198910079 / Last updated on: 1994-12-01
Original language: en
Available languages: en