RD&D-Programme 2004 - SKB

and reported. The composition and microbial content of the groundwater are fairly typical of
groundwaters at this depth. It is possible to work anaerobically in the laboratory in a box. Three
systems with circulating groundwater from fractures inside the rock permit studies of microbial
processes under repository conditions (in situ conditions with regard to pressure, chemistry and
temperature). A gas chromatograph and equipment for gas extraction are installed in the laboratory.
Measurements of gas can take place directly after sampling in the laboratory’s culturing
system or after sampling along the tunnel. Artificial ditches have been installed at a depth of
300 metres for investigations of Bios (bacteriogenic iron oxides). A series of different experiments
is planned at these two sites.
Bios have proved to have very high affinity for trace metals. Anaerobic biofilms (thin layers
of microbes on surfaces) consist of substances similar to those in Bios. Experiments are
being conducted where immobilization of different radionuclides, including cobalt-60 and
promethium-147, is being studied. Continued experiments include studies of biofilms on
different minerals.
Complexing agents have been identified from bacteria that grow with oxygen. These ligands
are formed so that the microorganisms can obtain vital trace elements, many of which have
very low solubility under oxic conditions, such as iron. The availability of trace metals
increases under anoxic conditions, which should mean little or no need for complexing agents.
Experiments will be conducted on microbes that grow anoxically in the Microbe laboratory
at the 420-metre level in the Äspö HRL. We intend to study whether complexing agents are
produced under repository-like anoxic conditions.
In the Rex experiments /19-87/ it was found that microbial oxygen reduction is an important
process. In a new project we are investigating the occurrence and activity of methane-oxidizing
microbes in the Äspö HRL and on the investigation sites. Methods for measurement of microbial
oxygen reduction are being developed.
The knowledge base on microbial processes in host rock is growing continuously. There is now
so much information that meaningful modelling work is possible. Several different important
microbial processes will be modelled. Microbial oxygen reduction with methane and organic
matter is being calculated. Calculations of sulphate reduction near deposition holes are being
performed. The contribution made by microbial processes to the rock’s long-term barrier
performance is also in focus.
19.2.19 Decomposition of inorganic engineering material
Conclusions in RD&D 2001 and its review
The process is of importance for the geosphere in an initial phase and close to the repository,
when the conditions are affected by the construction of the repository.
Newfound knowledge since RD&D 2001
An in situ experiment is being conducted in Grimsel, Switzerland, for the purpose of studying
how concrete pore water reacts with rock minerals. The results obtained so far are presented in
Chapter 25.
Programme
A project has been started in cooperation with Posiva to develop and test grouting materials that
yield leachate with a pH lower than 11.
The other principal inorganic engineering material is steel. This field is judged today not to
require any further research, development or demonstration.
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