Microbiota of spent nuclear fuel pool water with emphasis on their biofilm forming ability on stainless steel (SS-304L).

Spent nuclear fuel (SNF) pool is an essential unit of a nuclear power plant infrastructure, where radioactive fuel rods are kept for cooling and shielding, before reprocessing. This study explored the presence of bacteria in SNF pool water with emphasis on their capability to form biofilms on pool wall cladding material stainless steel (SS-304L). Bacteria were isolated from SNF pool water and were characterized using 16S rRNA gene sequencing. The six bacterial isolates (Bacillus subtilis, Staphylococcus sps., S. arlettae, S. epidermidis, S. auricularis and Chryseobacterium gleum) can grow and form biofilms at very low nutrient condition as well as in chronic radioactivity. The bacterial isolates formed biofilm on SS-304L and glass. However, the biofilm parameters assessed by CLSM microscopy showed that the strains preferred SS-304L surface for biofilm formation. On SS-304L, the maximum biomass (0.45 l μm3/l μm2) was formed by S. arlettae when compared to maximum biomass (0.054 l μm3/l μm2) by Staphylococcus sp., on glass. Maximum biofilm thickness on SS- 304L was observed by Staphylococcus sp. (8.81 l μm) when compared to that of S. epidermidis (4.16 l μm) on the glass surface. The biofilm formation on SS-304L surface suggests the possible risk of microbial-induced corrosion of SNF pool cladding material. This study highlights the need for mandatory monitoring of microbial biofilm formation in an extreme environment such as SNF pool.