Performance assessment of geological isolation systems for radioactive waste disposal in clay formations
In the framework of the PAGIS project studies have been undertaken on the geological disposal of vitrified high-level waste in clay layers. The calculations performed for the reference site show that most radionuclides decay to negligible levels within the first meters of the clay barrier. Only Tc-99, Cs-135 and Np-237 with its daughter nuclides U-233 and Th-229 can eventually reach the biosphere. The maximum dose rates are about 1.0 E-11 Sv/y for river pathways. If the sinking of a water well into the 150 m deep aquifer layer in the vicinity of the repository is considered together with a climatic change, the maximum calculated dose rate rises to 3x1.0 E-7 Sv/y. The calculated maxima arise between 1 million and 15 million years after disposal. In case of the Boom clay the estimated consequences of a fault scenario are of the same order of magnitude as the results obtained for the normal evolution scenario. The sensitivity analysis has shown that the effective thickness of the clay layer, the retention factors of Tc, Cs and Np, and the Darcy velocity in the aquifer are parameters which strongly influence the calculated dose rates. For the other site, the maximum dose rates are about 1x1.0 E-6 Sv/y for river pathways and 6x1.0 E-5 Sv/y for water well pathways after about 1 million years.
Bibliographic Reference: EUR 11776 EN (1988) FS, 752 pp., ECU 57.50
ISBN: ISBN 92-825-9254-5;CD-NA-
Record Number: 198910702 / Last updated on: 1994-12-01
Original language: en
Available languages: en