Physico-chemical characterisation and calculated in situ porewater chemistries for a low permeability Palfris marl sample from Wellenberg

摘要

Wellenberg (Gemeinde Wolfenschiessen, NW) has been chosen by Nagra as a repository site for short lived low- and medium-level radioactive waste. In certain regions of this Palfris marl formation, foreseen as actual locations for the repository, the water flow rates are so low that reliable water samples for chemical analysis were not obtainable. A sample of Palfris marl was provided from such a region and a physico-chemical characterisation technique, developed and tested in previous work, was applied. The measurements, coupled with a geochemical modelling study, yielded a NaCl type porewater with an ionic strength of (approx equal)0.12 M. In addition, a matrix marl porosity of (approx equal)1.5% was deduced using the chloride concentrations in the calculated porewater and measurements on the chloride content of marl. (author) 2 figs., 14 tabs., 12 refs. (Atomindex citation 26:007757)