Direct Meta-Analyses Reveal Unexpected Microbial Life in the Highly Radioactive Water of an Operating Nuclear Reactor Core.

Pauline C M Petit,Claude Alban,Corinne Rivasseau,Mohamed Mysara,Valérie Van Eesbeeck,Jean Armengaud,Pieter Monsieurs,Gérard Steinmetz,Olivier Pible

doi:10.3390/microorganisms8121857

Abstract

The pools of nuclear reactor facilities constitute harsh environments for life, bathed with ionizing radiation, filled with demineralized water and containing toxic radioactive elements. The very few studies published to date have explored water pools used to store spent nuclear fuels. Due to access restrictions and strong handling constraints related to the high radioactivity level, nothing is presently known about life in water pools that directly cool nuclear cores. In this work, we investigated the microbial communities in the cooling pool of the French Osiris nuclear reactor using direct meta-omics approaches, namely, DNA metabarcoding and proteotyping based on 16S ribosomal RNA gene sequencing and on peptide analysis, respectively. We identified 25 genera in the highly radioactive core water supply during operation with radionuclide activity higher than 3 × 109 Bq/m3. The prevailing genera Variovorax and Sphingomonas at operation were supplanted by Methylobacterium, Asanoa, and Streptomyces during shutdown. Variovorax might use dihydrogen produced by water radiolysis as an energy source.

Highlights

Nuclear reactor facilities constitute extreme environments for life and little information is available on the species capable of surviving in there
The concentration of gamma-emitters was 1000 to 10,000 times higher than that prevailing in the spent nuclear fuel pools (SNFPs), such as in the one previously investigated by our team [5]
We detected the presence of diverse microorganisms in the extreme environment of a working nuclear core pool

Summary

Introduction

Nuclear reactor facilities constitute extreme environments for life and little information is available on the species capable of surviving in there. The few studies published to date on this type of environment have focused on pools used to store spent nuclear fuels once the fuel has been used for energy production These water coolant pools sustain high levels of ionizing radiation originating from the cooling fuels, contain radioactive elements in solution including toxic metals, and are filled with demineralized water. The very few studies investigating the microbial diversity in such environments highlighted the presence of Proteobacteria, Firmicutes, Actinobacteria, Deinococcus-Thermus, and a Chlorophyta [1,2,3,4]. Due to the access restrictions and the difficulty in handling such samples, nothing is currently known about life in water used to cool nuclear reactor cores Such an environment is subject to even more severe conditions than spent nuclear fuel pools (SNFPs) since the water directly flows around the fuel rods, sustaining enormous amounts of radiation and exhibiting extremely large radionuclide concentrations during reactor operation. We explored the microbial communities present in the Osiris reactor core coolant water during operation and compared them with those present at shutdown

Methods

Results

Conclusion