Disposal of High Level Nuclear Waste
High Level Nuclear Waste (HLW) is the intensely radioactive residue from nuclear fission. The fission process provides heat used to generate electricity in nuclear fueled power plants. For disposal, the waste is enclosed in very strong, corrosion-resistant, metallic containers and put in underground chambers (the repository). The whole system is engineered to contain the waste intact and undisturbed for thousands of years.
According to federal regulation, used or “spent” reactor fuel from power plants is considered to be high level nuclear waste.
The US federal government is required to take title to the HLW and provide the physical facilities for its disposition. The cost of such facilities and the cost of the research and engineering studies required for licensing, construction, operation and closure are borne by all users of nuclear electricity. They pay a tenth of one cent per kilowatt hour used.
The Origin of High Level Nuclear Wastes
Following are principal steps in the formation and disposal of high level nuclear waste:
1.Manufacture of nuclear fuel from uranium slightly enriched in the fissionable isotope U-235
2.Use of the fuel in a nuclear reactor
3.Discharge of the fuel when no longer useful in the reactor
4.Temporary storage in a water pool while the heat output of the spent fuel declines
5.Transfer of the spent fuel to a reprocessing facility. If no reprocessing is done, step 8 comes next, after packaging the fuel in sturdy containers.
6. Chemical separation and isolation of the fission products and other elements from the rest of the spent fuel
7.Conversion and encapsulation of the isolated fission products to the form required for disposal
8.Emplacement of the packaged spent fuel/high level waste in a qualified and licensed underground repository.
Early in the development of commercial nuclear power production, it was an accepted belief that the spent nuclear fuel -- fuel no longer useful in the nuclear reactor -- would be chemically processed to recover plutonium and uranium for possible recycle, and to prepare the highly radioactive fission product wastes for disposal.
Such a “reprocessing” plant was built in New York state and in the 1960's operated for a number of years. The separated fission products were the first commercial HLW and they were stored (as dissolved solids and sludge in water) in underground tanks at the site of the reprocessing plant, pending development of a disposal procedure. They remained there until recent years when incorporation of the fission products into a stable glass was completed.
Later, when a policy not to reprocess spent fuel was adopted by the United States, the definition of HLW was extended to the spent fuel itself.
Today the HLW designation is applied to the spent nuclear fuel (fuel no longer useful for powering the reactor), or the fission products after separation from the spent fuel by a chemical process.
Amounts of High Level Nuclear Waste Produced. One of the most startling facts about HLW is the incredibly small amount produced for the quantity of electricity produced. This is readily apparent from comparison of the relative yearly amounts of wastes produced by power plants of the same size (1,000 MWe), one burning coal and the other fueled by uranium.
All values in the table below are approximate, especially those for coal