Team:Lyon-INSA-ENS/Safety/PublicEnvironmentalS

We considered Public and Environmental safety from both hazard and probability point of view. To measure how nuclear power plants related procedures and nuclear waste treatments are strictly regulated we organised two visits. First we visited the nuclear power plant of Tricastin to have an idea of how radioactive compounds are confined and how human workers are protected. Then we chose to visit the Centraco site which attend to a part of radioactive waste management.

Hazard

In usual working conditions, our strain will accumulate radioactive cobalt. Cobalt is toxic by inhalation and contact. It has been proven to cause cancer, respiratory system damage, skin damage among others on humans and various effects on other species including plants, [1] . It is important to notice that cobalt in our bacteria could be more concentrated than in usual resins. Radioactivity of the compound adds to the danger, with various damages that can’t be neglected : nausea, cerebral edema, sterility, foetal damage... Only low-dose effects can be effectively treated. A previous study [2] showed that cobalt accumulation capacity of the bacteria is not infinite and that bacteria death will conduce to the liberation of cobalt in the medium with the potential health issues that have been described if it ends up in the environment. For these reasons it is very important to ensure that the “Cobalt Buster” bio-filter will not release bacteria in environment after the processing.

In case of an unexpected release of the bacteria in the environment before it has fixated cobalt, we consider that hazard is low. Indeed, adding to the difficulties for the bacteria to survive in the Environment, none of the parts we will construct present a direct danger for Public as they will not modify the biosafety level of the E. coli strain and the bacteria does not produce any human toxic element by itself. However, antibiotic resistances carried by the different parts we will add to the E. coli strain may provide a selective advantage in environments where antibiotic selective pressure is high. Antibiotic resistances could be transferred to other bacteria strains, potentially human pathogens which would be favored by natural selection in such environments.

If a serious nuclear incident occurs (as INES scale level 7 nuclear disaster), the presence of our “Cobalt Buster” bio-filter will not enhance adverse consequences on health and environment. Indeed, in this case radioactivity level of the bio-filter can be neglected compared to releases generated by the incident and bacteria will probably be killed.

Probability

Once in working conditions, our strain will form a biofilm and be bound to a confined filter. As the biofilter is intended to work in nuclear power plants to capture radioactive cobalt, every steps of the industrial use of the “Cobalt Buster” strain will be done in confined conditions with a very strict procedure. Indeed, after the capture of radioactive cobalt in nuclear waste-water, our “Cobalt Buster” filter will be considered as nuclear waste and it will be supported following a very strict and highly regulated procedure.

Strict radioactive discharge protocols and storage conditions ensure that the probability of unintentional release is close to zero. Nuclear power plants are extremely confined and regulated areas. This implies that the probability of an unexpected event is extremely low. Moreover, water systems treated by the filter are isolated from each other and especially isolated from the environment which greatly reduces the risk of release.

All procedures in place in nuclear power plants are made to respect the precautionary principle and reduce the exposure of humans and environment to the minimum. The presence of our “Cobalt Buster” bio-filter will not increase the probability that a nuclear incident occurs in the power plant. We must notice that only two major nuclear incidents have occurred in the last fifteen years of nuclear power plants exploitation : is it low or high incident probability ?

Conclusion

As a conclusion, despite the danger due to the accumulation of radioactive metal in a non pathogenic E. coli strain, the potential hazard is rather low compared to other damage that an accident in a nuclear power plant would produce. Moreover, our device would change very little to the processes already implemented in nuclear power plants, that work with minimum exposure. Confinement in nuclear areas ensures a very low probability : the discharge is thoroughly controlled. The potential benefits of the “Cobalt Buster” bio-filter, reducing the volume of nuclear waste by 100 and decreasing costs of waste disposal, are greater than the risk we run, and according to us justifies the addition of such a device in nuclear power plants.

References :

[1] Cobalt et ses dérivés, INERIS, 2006 april, available here

[2] Bioremediation of trace cobalt from simulated spent decontamination solutions of nuclear power reactors using E. coli expressing NiCoT genes. Raghu G, Balaji V, Venkateswaran G, Rodrigue A, Maruthi Mohan P. Appl Microbiol Biotechnol. 2008 Dec.