speciation and mineralization by various enzymatic or non-enzymatic processes.
Microbial interaction with radionuclides has a great potential in detoxification of
radionuclides via mineralization, accumulation and transformation (Kumar et al.
2007). A variety of microorganisms such as Deinococcus radiodurans, Rhodotorula
taiwanensis MD1149, Mucor mehei, Chlorella vulgaris, and Parachlorella sp. binos
have been studied for remediation of radioactive wastes (Fredrickson et al. 2000;
Shimura et al. 2012; Tkavc et al. 2018; Kumar et al. 2007). Microorganisms adopt
various mechanisms like biotransformation, biomineralization, bioaccumulation,
etc. to degrade and detoxify radioactive wastes (Singh and Kumar 2020). Microorganisms have the ability to reduce or precipitate the radionuclides in aqueous
condition, and this is done by extracting electrons from organic compounds and
transferring it to the radionuclides as a final electron acceptor (Kumar et al. 2007).
This procedure basically makes the radionuclides stable and prevents spilling from
contaminated sites. In this chapter, we will discuss about sources of radioactive
wastes, impacts of radioactive wastes on environment and potential role of microbes
in remediation of radioactive wastes.
13.1.1 Sources of Radioactive Wastes
Radioactive wastes are the wastes which contain radioactive materials. Radioactive
materials are the compounds of unstable atoms which emit ionizing radiations as
they decay. Radioactivity is a natural process and any atom which is not in its stable
form will give off its extra energy to become stable. This process is known as
radioactive decay. The process of decaying is atom specific and no two atoms have
similar rate of radioactive decay (Bryant 2019).
Radioactive wastes typically generate from nuclear fuel cycle required for electrical power generation, research, medical, military and industrial applications and
also from accidents.
13.1.2 Nuclear Fuel Cycle
Nuclear fuel cycle is a series of processes, resulting in the production of electricity
from uranium in nuclear power plant (NPP). Two steps are involved in this process,
one when the nuclear fuel arrives at NPP which is regarded as front end and other
when the spent nuclear fuel (SNF) leaves the reactor, known as back end. Front-end
process is comprised of uranium mining, milling, refining, enrichment and fuel
fabrication to be used in nuclear reactor, whereas in contrast back-end process
involves storage of used fuel, recycling, reprocessing and ultimately disposal
(Rodríguez-Penalonga and Moratilla Soria 2017).
Two main strategies are involved globally to decide the fate of SNF: one is oncethrough cycle or direct disposal or open cycle and another is twice-through cycle or
13 Role of Microbes in Bioremediation of Radioactive Waste
331
Microbial interaction with radionuclides has a great potential in detoxification of
radionuclides via mineralization, accumulation and transformation (Kumar et al.
2007). A variety of microorganisms such as Deinococcus radiodurans, Rhodotorula
taiwanensis MD1149, Mucor mehei, Chlorella vulgaris, and Parachlorella sp. binos
have been studied for remediation of radioactive wastes (Fredrickson et al. 2000;
Shimura et al. 2012; Tkavc et al. 2018; Kumar et al. 2007). Microorganisms adopt
various mechanisms like biotransformation, biomineralization, bioaccumulation,
etc. to degrade and detoxify radioactive wastes (Singh and Kumar 2020). Microorganisms have the ability to reduce or precipitate the radionuclides in aqueous
condition, and this is done by extracting electrons from organic compounds and
transferring it to the radionuclides as a final electron acceptor (Kumar et al. 2007).
This procedure basically makes the radionuclides stable and prevents spilling from
contaminated sites. In this chapter, we will discuss about sources of radioactive
wastes, impacts of radioactive wastes on environment and potential role of microbes
in remediation of radioactive wastes.
13.1.1 Sources of Radioactive Wastes
Radioactive wastes are the wastes which contain radioactive materials. Radioactive
materials are the compounds of unstable atoms which emit ionizing radiations as
they decay. Radioactivity is a natural process and any atom which is not in its stable
form will give off its extra energy to become stable. This process is known as
radioactive decay. The process of decaying is atom specific and no two atoms have
similar rate of radioactive decay (Bryant 2019).
Radioactive wastes typically generate from nuclear fuel cycle required for electrical power generation, research, medical, military and industrial applications and
also from accidents.
13.1.2 Nuclear Fuel Cycle
Nuclear fuel cycle is a series of processes, resulting in the production of electricity
from uranium in nuclear power plant (NPP). Two steps are involved in this process,
one when the nuclear fuel arrives at NPP which is regarded as front end and other
when the spent nuclear fuel (SNF) leaves the reactor, known as back end. Front-end
process is comprised of uranium mining, milling, refining, enrichment and fuel
fabrication to be used in nuclear reactor, whereas in contrast back-end process
involves storage of used fuel, recycling, reprocessing and ultimately disposal
(Rodríguez-Penalonga and Moratilla Soria 2017).
Two main strategies are involved globally to decide the fate of SNF: one is oncethrough cycle or direct disposal or open cycle and another is twice-through cycle or
13 Role of Microbes in Bioremediation of Radioactive Waste
331