Microbiological assessment of spent nuclear fuel pools: An in-perspective review
Highlights
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The review describes about nuclear energy and the spent nuclear fuel (SNF) facility.
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Isolation of various bacteria from SNF pool water and their identification.
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Role of SNF pool bacteria in biofilm formation.
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Microbiologically induced corrosion and its plausible impact on SNF structural material.
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Use of SNF bacteria in bioremediation of radioactive toxic waste.
Abstract
Atomic or nuclear energy is one of the major sources of clean energy worldwide when compared to polluting fossil fuels. After thermal, hydroelectric, and renewable sources of energy, nuclear power is the fourth-largest source of electricity generation. The increased use of atomic energy warrants safety guidelines and also efficient management of nuclear waste. While studying the pros and cons of nuclear energy production, one of the major apprehensive areas is the spent nuclear fuel (SNF) facility. The SNF pool is the place where the spent nuclear fuel clusters are stored temporarily. SNF pool has a significant role in preserving the spent fuel components for nuclear waste management. Likewise, another completely neglected perspective as far as SNF is concerned is the pool water quality and the presence of microorganisms. In this review article, we describe the SNF facility, the physico-chemical parameters of pool water, the isolation and quantification of microorganisms in the SNF pool water, and their biofilm-forming potential. Finally, the consequences of SNF pool water microorganisms in causing structural material corrosion as well as their putative role in the bioremediation process are described.
Section snippets
Nuclear energy and its importance
Mankind’s ever-increasing demand for energy and its drive towards greener energy sources has led to an increase in the number of nuclear power plants worldwide. Atomic or nuclear energy is derived through nuclear fission or fusion processes and is largely used to generate electricity. The operational phase of a nuclear power plant is generally the longest phase of its life cycle, while the back-end process involves preserving the fuel components through spent fuel management systems such as
Spent nuclear fuel
Spent nuclear fuel is the nuclear fuel that has been removed after being used for energy generation in a nuclear reactor. Commonly, nuclear fuel is composed of specific isotopes that can undergo fission reactions to release energy. Fissionable elements used in nuclear fuel are Uranium-235 (Thermal reactors) or Plutonium-239 (Fast breeder reactors). Used or ‘spent fuel’ term generally refers to the uranium fuel that has been burnt in a commercial nuclear reactor to generate electricity. The
Microbiology of spent nuclear fuel storage facility
Based on radiation monitoring devices, nuclear power plant facilities can be constituted into different radiation level zones [16]. In nuclear reactors, primary and secondary water circulation systems and the SNF pool water are extreme environments and it is theoretically difficult for microbial life to thrive. The SNF pools of nuclear power plants constitute a very harsh environment for life, covered with radiation and toxic radioactive elements, and are filled with demineralized water. There
Biofilms
“A biofilm is defined as a conglomerate of bacteria, fungi, cyanobacteria and algae that are attached to a substratum by the exopolymeric matrix which entraps soluble and particulate organic and inorganic matter, concentrate nutrients, exo-enzymes, and eDNA”. Biofilms are transient adherent microbial communities that develop on immersed surfaces in aquatic environments. A biofilm is a heterogeneous unit, composed of organic and inorganic entities as well as microorganisms and larvae of
Microbiologically influenced corrosion
Corrosion of metallic surfaces affects many industries and services globally, corrosion is estimated to the tune of ~3.5% of the GNP of a nation. The potential for electrochemical corrosion of SNF is obviously an important concern; however, strict focus on the management of bulk water physicochemical factors (temperature, conductivity, chloride levels, and radioactivity) may have a tendency to ignore the fact that microbiological pathways can also deteriorate fuel components during wet storage.
Metal ion contamination in SNF pool water
As stated earlier, water quality is an important factor for the structural reliability of SNF pool structural material and cladded fuel assemblies during long-term storage. Based on published literature, it is inferred that the episodic changes in the physical and chemical properties of the SNF pool water contribute to the polymerization of chemicals, which in turn can chemisorb available nutrients, and attract the bacterial cells from the surrounding aqueous phase to form microbial aggregates.
Spent nuclear fuel pool: a repertoire for potential bioremediation bacteria
It is important to emphasize that the bacteria isolated from SNF pool water could be useful in the bioremediation of radionuclides [7]. The microbe’s ability to grow on different materials and ability to form biofilms in the radioactive environment makes them good candidates for bioremediation purposes. The microorganism present in the SNF pool water needs to be characterized so a better understanding of positive applications in waste treatment occur. The applications of SNF pool water isolates
Conclusion
The nuclear power system provides safe and clean energy to the world since there are no CO2 emissions or global warming issues. Another essential aspect of nuclear power generation is that the technology is maturing with much advancement, a very high quantity of electrical energy can be produced in a single plant and the waste generated is very less. The essential factors taken into account from various studies are the design and chemical aspects of nuclear reactor operation. Another important
CRediT authorship contribution statement
Dugeshwar Karley: Writing – draft review, Data curation. Sudhir Kumar Shukla: Writing – original draft, Data curation. Toleti Subba Rao: Supervision, Writing – review, Data interpretation, editing and correspondence.
Declaration of Competing Interest
The authors have no competing financial interest to declare.
Acknowledgments
The authors acknowledge Madras Atomic Power Station, NPCIL, Kalpakkam for the permissions and support extended in sampling SNF pool water.