Mixing and sulphate-reducing activity of bacteria in swelling, compacted bentonite clay under high-level radioactive waste repository conditions.
OBJECTIVE
The fate of micro-organisms in the bentonite clay surrounding high-level radioactive waste (HLW)-containing copper canisters in a future Swedish underground (500 m) repository were investigated.


RESULTS
Laboratory experiments were designed in which the mixing of various bacterial species with swelling bentonite was studied. A clear trend of fewer cultivable bacteria at depth was seen in the clay. This trend was consistent as the incubation time was increased from 8 h to 28 weeks. Sulphate-reducing bacteria were found to be active, reducing sulphate at the lowest density studied, 1.5 g cm-3, but sulphate reduction activity ceased at higher densities.


CONCLUSIONS
The number of viable micro-organisms in an HLW repository bentonite clay buffer will decrease rapidly during swelling and very few viable cells will be present at full compaction.


CONCLUSIONS
Sulphate-reducing bacteria will most probably not be able to induce corrosion of HLW-containing copper canisters.
Pedersen
K
K
Department of Cell and Molecular Biology, Microbiology Section, Göteborg University, Göteborg and Clay Technology AB, Ideon Research Centre, Lund, Sweden. pedersen@gmm.gu.se
Motamedi
M
M
Karnland
O
O
Sandén
T
T
D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism; D001546:Bentonite; D015169:Colony Count, Microbial; D003300:Copper; D010084:Oxidation-Reduction; D011850:Radioactive Waste; D012834:Silver; D013431:Sulfates / Q000378:metabolism*; D013440:Sulfides / Q000378:metabolism; D013462:Sulfur Radioisotopes; D016999:Sulfur-Reducing Bacteria / Q000254:growth & development* / Q000378:metabolism; D014867:Water; D014871:Water Microbiology
D011850:Radioactive Waste; D013431:Sulfates; D013440:Sulfides; D013462:Sulfur Radioisotopes; D014867:Water; D001546:Bentonite; D012834:Silver; D003300:Copper