RD&D-Programme 2004 - SKB

19.2.11 Advection/mixing – groundwater chemistry
This section deals with the mixing that occurs due to the fact that the water moves at varying
velocity in the fracture system in the rock and how the process influences the groundwater
chemistry. The next section deals with advection and dispersion in connection with radionuclide
transport.
Conclusions in RD&D 2001 and its review
Mixing calculations, utilizing for example the code M3, that were originally carried out with
data from the Äspö area have been supplemented by calculations including data from other
investigated sites in Sweden and Finland. It turns out that the mixing pattern is similar, but the
proportions of the different “typical waters” vary from site to site. However, there are clear
similarities in the probable hydrological and chemical evolution undergone by the sites. Modern
meteoric and glacial water can always be identified. Often, though not always, deep saline water
is present, and in coastal locations modern and old seawater is always present.
Results from the modelling exercise within the international Task 5 Äspö Task Force on
Modelling of Groundwater Flow and Transport of Solutes showed that it is possible to numerically
handle the advection/mixing process on a large scale and thereby utilize both hydrological
and chemical data.
SKI points out that SKB should also report the calculated salinity evolution for scenarios that
involve extensive climate changes over long periods of time.
Newfound knowledge since RD&D 2001
New models for groundwater flow have been developed, see also section 19.2.3 concerning
groundwater flow.
Programme
The computer code M3, which is used for statistical processing by multivariate analysis, has
been developed with support from SKB. M3 is planned to undergo a number of updates and
verifications within the next six years.
One of the models developed for groundwater flow (Darcy Tools) will be evaluated in a recently
started project. The purpose is to model the conditions around Äspö by including both chemical
parameters and hydrological data, see 19.2.3.
Within the site investigations, site-specific mixing calculations will be important for understanding
the evolution of the water on the site. Calculations of salinity evolution in connection with
extensive climate changes over long periods of time will be carried out within the framework of
the next few safety assessments. An attempt will be made to link hydrochemistry with hydrogeological
data and calculations in coming site modellings and safety assessments.
19.2.12 Advection/mixing – radionuclide transport
Conclusions in RD&D 2001 and its review
No questions for further research were identified in RD&D-Programme 2001 or its review.
RD&D-Programme 2001 dealt with flow-related transport parameters under the two headings
“Groundwater transport” and “Radionuclide transport – molecular diffusion and matrix
diffusion”.
256 RD&D-Programme 2004