16-02-2010, 07:37 PM
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HAZARDOUS WASTE MANAGEMENT
INTRODUCTION
Nuclear power is characterized by the very large amount of energy available from a very small amount of fuel.
The amount of waste is also relatively small. However; much of the waste is radioactive and therefore must be carefully managed as hazardous waste.
Radioactivity arises naturally from the decay of particular forms of some elements called isotopes.
There are three types of radiations to consider alpha, beta and gamma.
A fourth kind neutron radiation, generally only occurs inside a nuclear reactor.
HAZARDOUS WASTE “DEFINITION
A product is considered to be HAZARDOUS if it is defined as toxic, flammable, corrosive and irritant.
A hazardous waste is a substant which causes a hazard to human health or the environment when improperly managed.
WASTE MANAGEMENT-DEFINITION
Waste management is the collection, transport, processing or disposal of waste materials, usually ones produced by human activity, in an effort to reduce their effect on human health or local amenity.
Waste management can involve solid, liquid or gaseous wastes, with different methods and fields of expertise for each.
RADIO ACTIVE WASTE MANAGEMENT
The multiple aspects of Radio active waste management include physical and value oriented issues.
What radios active waste is, where it is, how it has been generated and handled, what some of the difficulties are in handling, treating and disposing of the stuff-these are central issues in radio active management.
Understanding both values and physical aspects of radioactive waste will help foster an understanding of the bureaucratic problem involved in meaning this material.
RADIO ACTIVE WASTES-CLASSIFICATION
1. Mine Tailings
2. High-level Wastes (HLW)
3. Low-level Wastes (LLW)
4. Intermediate -level Wastes (ILW)
1.MINE TAILINGS
Traditional uranium mining generates fine sandy tailings, which contain virtually all the naturally occurring radioactive elements normally found in uranium ore.
These are collected in engineered tailings dams and finally covered with a layer of clay and rock to inhibit the leakage of radon gas and ensure long-term stability.
In the short term, the tailings material is often covered with water.
After a few months, the tailings material contains about 75% of the radioactivity of the original ore.
Strictly speaking these are not classified as radioactive wastes.
2.LOW “LEVEL WASTE
These are generated from the hospitals and industry as well as the nuclear fuel cycle.
It comprises paper, rags, tools, clothing, filter etc, which contains small amounts of mostly short-lived radioactivity.
it does not require shielding during handling and is suitable for shallow land burial.
It comprises some 90% of the volume but only 1% of the radio activity of all radioactive wastes.
3.INTERMEDIATE- LEVEL WASTE
It contains higher amounts of radio activity and some requires shielding.
It typically comprises resins, chemical sludge and metal fuel claddings as well as contaminated materials from the reactor decommissioning.
It makes up some 7% of the volume and has 4%of the radioactivity of all radwastes.
4. HIGH-LEVEL WASTE
It arises from the use of uranium fuel in a nuclear reactor.
It contains the fission products and transuranic elements generated in the reactor core.
It is highly radioactive and hot, so requires cooling and shielding.
It accounts for over 95% of the total radioactivity produced in the process of electricity generation.
WASTE FROM NUCLEAR FUEL CYCLE
All parts of the nuclear fuel cycle produce some radioactive waste and the cost of managing and disposing of this is the part of the electricity cost.
At each stage of the fuel cycle there are proven technologies to dispose the radioactive waste safely.
The fuel cycle is often split in to two parts.
The front end which stretches from mining through to the use of uranium in the reactor.
The back end which covers the removal of spend fuel from the reactor and its subsequent treatment and disposal.
WASTE DISPOSAL
Final disposal of high-level waste is delayed to allow its radioactivity to decay.
Forty years after removal from the reactor less than one thousand of its initial radioactivity remains, and it is much easier to handle.
Hence canisters of vitrified waste or spent fuel assemblies are stored under water in special ponds or in dry concrete structures or casks for at least this length of time.
The most favorable method for the disposal of spent fuel is the burial in dry, stable geological formations some 500 meters deep.
STORAGE OF WASTE
Proper storage of chemical waste shall include separation of incompatible materials.
Collect spent, halogenated solvents in a separate container from non halogenated solvents.
Do not mix aqueous solutions with organic solvents. Keep all wastes in well-ventilated areas.
Flammable and combustible liquids should be stored in a flammable liquids cabinet.
Waste containers must be capped at all times and may be uncapped only for the addition of more wastes.
LABELLING AND CONTAINER MANAGEMENT
All hazardous materials, including chemical wastes, must be properly labeled.
A label listing all of the chemicals present and their concentration or percentage, if known, must be securely affixed to all waste containers.
Symbols, chemical formulas, structures, trade names and abbreviations are not acceptable.
Each container should be clearly marked with words Waste (name of the chemical) and labeled with the date waste is first placed into that container.
All containers must be kept closed unless adding or removing waste missing, corroded or broken lids or containers will not be accepted until waste is transferred to an appropriate container for disposal
WASTE MINIMIZATION
Waste minimization means a reduction in both the volume and physical hazards or toxicity of the material.
The benefit of waste minimization include reduced disposal cost, decreased liability, improved working conditions and less impact on the environment at the time of disposal.
The waste minimization policy requires investigations to make every effort to minimize the volume of their wastes.
Substitutions can be made to eliminate or reduce the amount of hazardous wastes.
The last step of an experimental procedure can include treatment to reduce the toxicity of experimental by-products.
CONCLUSION
Radioactive waste is not a single thing that can be isolated and dealt with a magic bullet.
Rather, radioactive waste management involves numerous physical, political, and cultural factors in a dynamic, on going process.
A recent development in the field of pollution control and hazardous waste management is the beginning of a new approach altogether namely GREEN CHEMISTRY.
Today expert systems which can provide alternate routes that generate little or zero hazardous waste for chemical manufacture have taken birth.
