The BR2 nuclear research reactor consists of different watery environments: the primary cooling circuit consists of a closed loop containing water that cools down the fuel rods in the reactor core. An open basin surrounds the reactor vessel, whereas spent nuclear fuel is stored in the contiguous spent nuclear fuel pool (SNFP) in order to cool down before being safely disposed. Remarkably, despite the low-nutrient environment combined with the radioactive character of the water, microbial growth is not fully prevented. Indeed, several microbes appear to be able to survive and thrive in such conditions. Microorganisms identified in those environments thus provide a unique opportunity to acquire new insights into survival strategies and radiation-resistance mechanisms. In addition, the study of those organisms could lead to the discovery op suitable candidates to be used in the bioremediation of contaminated effluents.
The objective of this work is to explore the bacterial communities present in the described environments of the BR2 nuclear research reactor. In parallel, this research also focuses on following up these communities over time during and outside reactor operation to monitor the long-term effect of ionizing radiation.
For the characterization and the follow-up of the bacterial communities, a 16S rRNA amplicon sequencing approach was adopted. Results from a long-term follow-up experiment highlighted a clear shift in the bacterial community profile during and outside reactor operation, both for the basin and the primary water. This is due to the change in physico-chemical parameters that these waters undergo when transitioning from one state to the other.