The aim of the present research was to isolate and identify bacteria from spent nuclear fuel pools of a Spanish nuclear power plant. Water samples were collected and inoculated onto different culture media to isolate the highest number of species. 16S rDNA fragments from colonies growing on solid media were amplified and analysed by denaturing gradient gel electrophoresis. Sequencing revealed the presence of 21 different bacteria belonging to several phylogenetic groups (alpha, beta, and gamma-Proteobacteria, Actinomycetales, Flavobacterium, and the Bacillus/Staphylococcus group). The isolation of these microorganisms in this particular environment (oligotrophic and radioactive) is highly interesting because of the possibility of their being used for the bioremediation of radionuclide-contaminated waters.

Microbial activity in spent nuclear fuel pools which contain ultrapure and radioactive water has been previously observed. The aim of the present research was to isolate and identify the microorganisms attached to the nuclear pool wall of a Spanish nuclear power plant. Amplification of 16S rDNA fragments from the culturable microorganisms by PCR using universal primers for the domain 'Bacteria', followed by Denaturing Gradient Gel Electrophoresis analysis revealed the presence of six different bacteria. The complete gene for 16S rDNA of each one was sequenced and identified as belonging to three different phylogenetic groups, viz. beta-Proteobacteria, Actinomycetales and the Bacillus/Staphylococcus group. A fungus was also found and identified as Aspergillus fumigatus by sequencing the D2 region of the large subunit rDNA gene. The isolation of these microorganisms in oligotrophic and radioactive conditions is of great interest due to the possibility of their use in bioremediation processes of radionuclide-contaminated environments.

The objective of this study was to investigate the biofilm formation on three different types of austenitic stainless steel (UNS S30400, S30466 and S31600) submerged in a spent nuclear fuel pool. The presence of microorganisms in coupons was characterised using standard culture microbiological methods, microscopic techniques (epifluorescence microscopy and scanning electron microscopy), and molecular biology techniques (denaturing gradient gel electrophoresis and sequencing fragments of 16S rDNA). The microscopy techniques showed signs of colonisation of stainless steels in spite of these extreme conditions. Based on sequencing of cultured microorganisms, different bacteria belonging to a, b, c-Proteobacteria, Bacilli, and Actinobacteria classes have been identified. The biofilm radioactivity was measured using gamma-ray spectrometry and, according to the data gathered, the radionuclides present in the water pool were entrapped in the biofilm increasing the amount of radiation at the surface of the different materials.

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The aim of the present research was to study the biofilms developed in a Spanish nuclear power plant and their ability to entrap radionuclides. In order to carry this out, a bioreactor, which was then submerged in a spent nuclear fuel pool, was designed. To characterise the biofilm on two different metallic materials (stainless steel and titanium), standard culture microbiological methods and molecular biology tools, as well as epifluorescence and scanning electron microscopy were used. The bacterial composition of the biofilm belongs to several phylogenetic groups (alpha, beta, and gamma-Proteobacteria, Actinobacteridae, and Firmicutes). The radioactivity of the biofilms was measured by gamma-ray spectrometry. Biofilms were able to retain radionuclides from radioactive water, especially (60)Co. The potential use of these biofilms in bioremediation of radioactive water is discussed.