radioactive waste management
TRANSCRIPT
Nuclear WASTE:
Radioactive wastes are usually the waste materials containing radioactive material. It is the product of a nuclear process such as nuclear fission.
INTRODUCTION
Radio activity Certain elements that compose matter emit
particles and radiations spontaneously. This phenomenon is referred to as ‘radioactivity’
Three different kinds of rays; Alpha, Beta and Gamma rays are associated with radioactivity. The alpha rays consist of particles (nuclei of helium atoms) carrying a +ve charge, beta rays particles have –ve charge (streams of electrons) and gamma rays are charge less EM radiation
Radioactive elements decay at different rates.
Rates are measured as half-lives – that is, the time it takes for onehalf of any given quantity of a
radioactive element to disintegrate.
The longest half-life is that of the‘isotope’ 238U of uranium. It is 4.5 billion years. Some isotopes have half-lives of years, months, days, minutes, seconds, or even less than millionths of a second.
Introduction
Radio active waste
Radioactive wastes are waste that
contain radioactive material.
Radioactive wastes are usually by-
products of nuclear power generation
and other applications of nuclear
fission or nuclear technology, such
as research and medicine.
Radioactive waste is hazardous to
human health and the environment, and
is regulated by government agencies in
order to protect human health and the
environment.
So for the disposal of this radio active
waste lot of steps are needed
TYPE OF RADIO ACTIVE WASTE High activity, long life Medium activity, Long lifeLow activity, Long lifeMedium activity, Short life Low activity, Short life
RELATIVE WASTE VOLUME:
90% low level
waste
7% intermediate level waste
3% high level waste
low level waste
intermediate level waste
high level waste
Classification of radioactive waste Characterization
high intensity of β- or γ- radiation,
I. HIGH ACTIVITY, large α- activity
LONG LIFE high radio toxicity,
large making of heat
medium intensity of β- or γ- radiation,
II. MEDIUM ACTIVITY, large α- activity
LONG LIFE medium radio toxicity,
medium making of heat
low intensity of β- or γ- radiation,
III. LOW ACTIVITY, large α- activity
LONG LIFE low or medium radio toxicity,
negligible making of heat
medium intensity of β- or γ- radiation,
IV. MEDIUM ACTIVITY, negligible α- activity
SHORT LIFE medium radio toxicity,
medium making of heat
low intensity of β- or γ- radiation,
V. LOW ACTIVITY, negligible α- activity
SHORT LIFE low radio toxicity,
negligible making of heat
nuclear WASTE DISPOSAL
Currently, internationally preferred solution is for
geological disposal by interment in a mined and
engineered, multi-barrier repository . Engineered
disposal system has generally been constructed at
or near the surface for wastes with low-level
radioactivity and wastes with short-lived radioactivity.
It is being built or is planned to built deep
underground in geological formation for high-level
and long-lived wastes
Transport of Radio Active nuclear waste
The radioactive wastes can be transported to the repositories or mines with the help of lead castle. The burial of radioactive waste has been an efficient method for its disposal, but the risks involved in it also have to be taken into account.
One of the problems that can occur is that a leakage in
the repositories can cause contamination in the water
table thereby which when reaching the surface can
affect crops.
Microbial action on nuclear waste
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.
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.
MICROBES THAT DECOMPOSES CYANIDE:
The bacteria's such as Pseudomonas putida, Pseudomonas pickettii, Pseudomonas paucimobilis, oxidizes the cyanide, breaking it down into harmless compounds.
2HCN+O2=2HCNO
HCNO+H2O=NH3+CO2
The direct oxidation of cyanide produces cyanate ions and it is being given by the equation
2CN2+O2=2CNO
These bacteria's can also react with cyanide in the anaerobic condition also. The process can be explained by the following equations
CN2+H2S+HCNS+H2
HCN+HS2=HCNS+H2
The HCNS then hydrolyze to form NH2, H2S and CO2.
URANIUM-EATING BACTERIAThe bacterial species of Geobacter are able to precipitate radionuclieds
like Uranium , Technium, and many other heavy metals. This bacteria not only nullifying the toxicity of Uranium also able to produce
electricity from it as they oxidize Uranium in order to gain energy.
Production of Energy The production of energy by the Geobacter is by the
process of transfer of electrons through their pili. Energy from bacteria can be collected through forced induction or with the help of bacteria present in water which is able to convert water into their respective components,hydrogen and oxygen. Thereby the produced hydrogen can be used a source of energy.