POLLUTION AND ITS CONTROL 433
- Power generation in the reactor, resulting in irradiated or spent fuel.
- Short-term storage of the spent fuel.
- Reprocessing of the irradiated fuel and conversion of the residual uranium to uranium
hexafluoride, UF 6 (for recycling through the gaseous diffusion plant for reenrichment) and/or
extraction of Pu^239 (converted from U^238 ) for recycling to the fuel-fabrication plant.
Reprocessing can reuse up to 96 percent of the original material in the irradiated fuel with 4
percent actually becoming waste.
- Waste management, which includes long-term storage of high-level wastes.
Step 8, reprocessing, may be bypassed, which results in disposal of both reusable fuel and wastes.
This is the current (1982) U.S. Department of Energy process for dealing with irradiated fuel. The fuel
assemblies are stored for at least 10 years and then buried. This is the so-called throw-away fuel cycle.
Leak
Detection pit
Instrument
probes
Rein concrete
Vit enculators
below grade7 ft
Primary tank
Secondary tank
Sludge
75-ft diameter
Fig. 13.5. A typical low-level liquid-waste storage tank with double-walled containment.
13.17.2 Wastes
The wastes associated with nuclear power can be summarized as:
- Gaseous effluents. Under normal operation, these are released slowly from the power plants
into the biosphere and become diluted and dispersed harmlessly.
- Uranium mine and mill tailings. Tailings are residues from uranium mining and milling
operations. They contain low concentrations of naturally occurring radio-active materials. They are
generated in large volumes and are stored at the mine or mill sites.
- Low-level wastes (LLW). These are classified as wastes that contain less than 10 nCi
(nanocuries) per gram of transuranium contaminants and that have low but potentially hazardous con-
centrations of radioactive materials. They are generated in almost all activities (power generation, medi-
cal, industrial, etc.) that involve radioactive materials, require little or no shielding, and are usually
disposed of in liquid form by shallow land burial (Fig. 13.5).
- High-level wastes (HLW). These are generated in the reprocessing of spent fuel. They con-
tain essentially all the fission products and most of the transuranium elements not separated during
reprocessing. Such wastes are to be disposed of carefully.
- Spent fuel. This is unreprocessed spent fuel that is removed from the reactor core after reach-
ing its end-of-life core service. It is usually removed intact in its fuel element structural form and then
stored for 3 to 4 months under water on the plant site to give time for the most intense radioactive
