Power Plant Engineering

Fig. 13.4. A typical nuclear fuel cycle (a) with reprocessing and (b) without reprocessing.
The different process are briefly explained below:
1. Mining of the uranium ore.
2. Milling and refining of the ore to produce uranium concentrates, U
3
O
8
.
3. Processing to produce of uranium hexafluoride, UF
6
, from the uranium concen-trates. This
provides feed for isotopic (U
235
) enrichment.
4. Isotopic enrichment of uranium hexafluoride to reach reactor enrichment require-ments. This
is done invariably now by the gaseous diffusion process.
5. Fabrication of the reactor fuel elements. This includes conversion of uranium hexafluoride to
uranium dioxide UO
2
, pelletizing, encapsulating in rods, and assembling the fuel rods into
subassemblies.

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6. Power generation in the reactor, resulting in irradiated or spent fuel.
7. Short-term storage of the spent fuel.
8. 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.
9. 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
7 ft
below grade
Primary tank
Secondary tank
Sludge
75-ft diameter