Development and characterization of biofilms on stainless steel and titanium in spent nuclear fuel pools.

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.

Biofilm formation in spent nuclear fuel pools and bioremediation of radioactive water.

Microbiological studies of spent nuclear fuel pools at the Cofrentes Nuclear Power Plant (Valencia, Spain) were initiated to determine the microbial populations in the pools' water. Biofilm formation at the nuclear power plant facilities and the potential use of those microbial populations in the bioremediation of radioactive water were also studied. Biofilm formation was analyzed by immersing different austenitic stainless steel coupons (UNS S30400, UNS S30466, UNS S31600), as well as balls of stainless steel (UNS S44200) and titanium (99.9%) in a spent nuclear fuel pool (under static and dynamic conditions) for 34 months. Epifluorescence microscopy and scanning electron microscopy revealed that biofilm formed on the samples, in spite of the radioactive and oligotrophic conditions of the water. Based on standard culture methods and sequencing of 16S rDNA fragments, 57 bacteria belonging to alpha-, beta-, and gamma-Proteobacteria, Firmicutes and Actinobacteridae were identified in the biofilms. The radioactivity of the biofilm was measured using gamma-ray spectrometry, which revealed that biofilms were able to retain radionuclides, especially (60)Co. Using metallic materials to decontaminate radioactive water could become a new approach for bioremediation.

Biofilm formation in spent nuclear fuel pools and bioremediation of radioactive water / Formación de biopelículas en piscinas de combustible nuclear gastado y biorremediación de aguas radiactivas

Microbiological studies of spent nuclear fuel pools at the Cofrentes Nuclear Power Plant (Valencia, Spain) were initiated to determine the microbial populations in the pools' water. Biofilm formation at the nuclear power plant facilities and the potential use of those microbial populations in the bioremediation of radioactive water were also studied. Biofilm formation was analyzed by immersing different austenitic stainless steel coupons (UNS S30400, UNS S30466, UNS S31600), as well as balls of stainless steel (UNS S44200) and titanium (99.9%) in a spent nuclear fuel pool (under static and dynamic conditions) for 34 months. Epifluorescence microscopy and scanning electron microscopy revealed that biofilm formed on the samples, in spite of the radioactive and oligotrophic conditions of the water. Based on standard culture methods and sequencing of 16S rDNA fragments, 57 bacteria belonging to α-, β-, and γ-Proteobacteria, Firmicutes and Actinobacteridae were identified in the biofilms. The radioactivity of the biofilm was measured using γ-ray spectrometry, which revealed that biofilms were able to retain radionuclides, especially 60Co. Using metallic materials to decontaminate radioactive water could become a new approach for bioremediation (AU)

Los estudios microbiológicos de las piscinas de combustible nuclear gastado en la Central Nuclear de Cofrentes (Valencia, España) se iniciaron para determinar las poblaciones microbianas del agua de dichas las piscinas. También se estudió la formación de biopelículas en las instalaciones de la central nuclear y del posible uso de esas poblaciones microbianas para la biorremediación de aguas radiactivas. Para analizar la formación de las biopelículas en una piscina de combustible nuclear gastado, se sumergieron durante 34 meses (en condiciones estáticas y dinámicas) cupones de acero inoxidable austenítico (UNS S30400, UNS S30466, UNS S31600), así como ovillos de acero inoxidable (UNS S44200) y titanio (99.9%). La observación al microscopio de epifluorescencia y al microscopio electrónico de barrido reveló la formación de biopelículas sobre las muestras a pesar del carácter radioactivo y oligotrófico del agua. De acuerdo con los métodos estándar de cultivo y secuenciación de los fragmentos del 16S rDNA, en las biopelículas se identificaron 57 bacterias diferentes pertenecientes a los grupos α-, β-, y γ-Proteobacteria, Firmicutes y Actinobacteridae. La radiactividad de las biopelículas se midió por espectrometría gamma y esta técnica demostró que las biopelículas son capaces de retener radionucleidos, especialmente 60Co. El empleo de materiales metálicos para descontaminar aguas radiactivas podría ser un nuevo método de biorremediación (AU)

Isolation and identification of bacteria from spent nuclear fuel pools.

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.

Biofouling on the walls of a spent nuclear fuel pool with radioactive ultrapure water.

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.