Radiosensitivity of subterranean bacteria in the Hungarian upper permian siltstone formation

The main purpose of this work was to study the radioresistance of subterranean aerobic and anaerobic isolates from the Hungarian Upper Permian Siltstone (Aleurolite) Formation, in order to assess the safety of potential sites of future underground repositories for nuclear waste. A total of 93 isolates were studied. The radiosensitivities of these aerobic and anaerobic bacteria isolates were determined: the D10 values (decimal reducing doses) of the aerobic spore-formers lay in the range 0.80–2.44 kGy, and those of the anaerobic spore-formers lay in the range 1.86–4.93 kGy. The D10 values of the aerobic and anaerobic vegetative isolates were much lower, in the ranges 0.11–0.57 and 0.22–0.40 kGy, respectively. The variability in bacterial radioresistance indicates the biodiversity at this potential disposal site. These results can affect the construction of a future underground repository, since knowledge of the most resistant microorganism may be of importance as concerns calculation of the time required to inactivate the bacteria surrounding the containers.