DECOMPOSITION OF RADIOACTIVE WASTES

              Radioactive wastes are usually the waste materials containing radioactive material. It is the product of a nuclear process such as nuclear fission. The issue of disposal methods for nuclear waste was one of the most pressing current problems the international nuclear industry faced while trying to establish a long term energy production plan.

              Radioactive waste typically comprises of number of radio isotopes which can be harmful to human health and to the environment.

               Exposure to high levels of radioactive waste may cause serious harm of death. Treatment of adult animal with radiation can cause cancer in animals. In human it is calculated that a 5 seivert dose is usually fatal.

               The main objective in managing and disposing or destruction of radioactive waste is to protect people and the environment.

RADIATION AFFECTED BABY

SOURCES OF RADIOACTIVE WASTES:

EXPLOSION OF AN ATOMIC BOMB

NUCLEAR REACTORS

        
        Radioactive waste comes from a number of sources. The majority of waste originates from the nuclear fuel cycle and nuclear weapons. Nuclear fuel cycle is the progression of nuclear fuel through a series of differing steps. It is also called as nuclear fuel chain. Some other sources are medical and industrial wastes and naturally occurring radioactive materials concentrating as a result of the processing or consumption of coal,oil,gas and some other minerals.

TYPES OF RADIOACTIVE WASTES:

• Low level waste
• Intermediate level waste
• High level waste

LOW LEVEL RADIOACTIVE WASTES

HIGH LEVEL RADIOACTIVE WASTE

RADIOACTIVE WASTES ARE RICH IN:

                  The most important components which are present in the radioactive wastes are as follows. This does not mean that it is rich only in these components. If we are decomposing these components then the decomposition of the radioactive wastes will become an easier task.                                               

• Hydro carbons
• Radio isotopes
• Uranium
• Mercury
• Cyanide                                             

              The view here is to implement BIO REMEDIATION in the disposal of radioactive wastes. Bio remediation is the process that uses micro organisms to return the natural environment altered by the contaminants. So during the disposal of radioactive wastes if bio remediation is implied then it would be easy to reduce the complexity of these waste materials. Since the decomposition of the nuclear wastes are a great hazard for us if we implement this method then the disposal of the nuclear waste would be easier. Let's see some of the micro organisms that are able to decompose the compounds of the radioactive wastes.

BIO REMEDIATION

MICROBES THAT DECOMPOSES MERCURY:

                 Specific stable isotope of mercury can be degraded by a mercury resistant marine bacteria Pseudomonas aeruginosa CH07. By these bacteria the mercury content of the radioactive wastes can be minimized. The volatilization of the mercury content can be reduced by the activity of these bacteria.

PSEUDOMONAS AERUGINOSA

MICROBES THAT DECOMPOSES HYDRO CARBONS:

                   Pseudomonas putida is a type of gram negative bacteria which can effectively degrade the content of the hydrocarbon present in the waste materials. This bacteria is aerobic in nature. These bacteria break down the hydrocarbons into carbon dioxide and water. Hence by using this bacteria the content of the hydrocarbon present in the radioactive waste can be considerably minimized. Bacteria's such as pseudomonas aeruginosa and serratia marcescens species can degrade the content of the hydrocarbons in an effective manner.

PSEUDOMONAS PUITDA

MICROBES THAT DECOMPOSES URANIUM:

                 There is a sulphate reducing bacteria named Desulfovibrio desulfuricans. It can reduce the amount of sulphates present in the radioactive wastes. Desulfovibrio desulfuricans rapidly reduces the uranium content from the acetate components present in the radioactive substances. Uranium here will form an aromatic complex here which can easily degrade by Shewanella alga. So to reduce the uranium present in the waste materials these bacteria's and some type of Shewanella algae should be used.

   DESULFOVIBRIO DESULFURICANS         SHEWANELLA ALGA                                                         

MICROBES THAT DECOMPOSE CYNIDE:

               The bacteria's such as Pseudomonas putida, Pseudomonas pickettii, Pseudomonas paucimobilis, oxidizes the cyanide, breaking it down into harmless compounds.

               These can be carried out only by the aerobic conditions. The process can be explained by the following equations. The aerobic degradation of hydrogen cyanide is given by

1.  2HCN+O2=2HCNO
2. HCNO+H2O=NH2+CO2                                                                                                                                                                                                                     The direct oxidation of cyanide produces cyanate ions and it is being given by the equation                    
3. 2CN2+O2=2CNO2

              These bacteria's can also react with cyanide in the anaerobic condition also. The process can be explained by the following equations.

1. CN2+H2S+HCNS+H2
2. HCN+HS2=HCNS+H2

             The HCNS then hydrolyze to form NH2, H2S and CO2.

KLEBSEILLA PNEUMONIA           PSEUDOMONAS PICKETTII

MICROBES DEGRADING RADIO ISOTOPES:

              The degradation of the radio isotopes can be carried out by a fungus Sporotrichum pulverlentum. These microbes can degrade the content of these radio isotopes up to less than 4%. Pseudomonas bacteria such as pseudomonas fluorescens UKI is used to degrade the methionine which is one of the important radio isotopes. Pseudomonas Sp. can metabolize not only the alpha and gamma isomers but also the beta isomers which in turn liberate chloride as a product.

PSEUDOMONAS FLUORESCENS

DID MICROBES SURVIVE IN RADIATIONS:

              The bacteria's which are used for the degradation of the radioactive wastes will be radiation resistant. So it is known that these bacteria's can survive in radiations and do their reactions without any mutation.

MICROBES RESISTING RADIATIONS

REACTIONS:

              Mostly the reactions caused by these bacteria's are either oxidation or reduction only. Because oxidation and the reduction are the two basic reactions for all bacteria's during these actions.If so all the products formed by these bacterial actions are combined together to form a strong acid or base so that it is easy to eliminate those acids of a base by adding another strong base or acid respectively. Thus the complex nature of the radioactive waste can be eliminated and converted into simpler form to decompose it in an efficient manner.

CONCLUSION:

             Since the nuclear and the radioactive wastes are more dangerous and causes very harmful effects the most common method of disposing the waste is collecting these wastes in a hard concrete barrels and closing that barrel with a hard substrate and then burying those barrels into the deep sea or ocean. This method is probably called as ocean dumping.

             If we do so some times due to the improper disposal there may be a chance of contamination of the sea and ocean which will affect the aquatic life to the most. The transportation accidents during the disposal of these wastes will cause serious consequences due to the exposure of the harmful radiations. The exposure of these radiations will affect the human's life as well.

             If we implement bio remediation in the disposal of nuclear waste or radioactive wastes then it would be easy to overcome all the above mentioned problems.

DISPOSAL OF RADIOACTIVE WASTES

REFERENCES:

1. Microbes degrading Mercury-Springer Link Journal article.
2. Pseudomonas bacteria degrading carbon- Pseudomonas putida  encyclopedia citizendium, current microbiology-Springer Link Journal article.
3. Pseudomonas bacteria degrading uranium- Article from American Society of Micro biology.
4. Cyanide decomposing bacteria-Cyanide-Wikipedia
5. Energy citation database- Environ.Sci.Technol.(United States) Journal Volume:19:1.
6. Journal of general microbiology(1976),94,Applied and Environmental Microbiology, Nov 1990,p.3620- American Society of Microbiology.
7. Did Pseudomonas resist radiation- JSTOR research, vol.15, No.6(Dec.,1961) by Radiation Research Society.
8. Oxidation and Reduction reaction of bacteria- Article from American Society of Microbiology.
9. Radioactive wastes- Wikipedia.