TRANSPORTATION OF RADIOACTIVE MATERIALS - Environmentally Conscious Materials Handling - page 220

Constituents of Spent Nuclear Fuel

Long-lived I and Tc
0.1%

Plutonium
0.9%

Uranium
95.6%

Minor actindes
0.1%
Other long-lived
fission products
0.1%

Other
4.4%

Stable fission
products
2.9%

Cs and Sr
0.3%

Figure 8.4 Constituents of spent nuclear fuel (Ryskamp 2003).

high levels of penetrating radiation emitted by used nuclear fuel. Because of the
fission products present, casks for transporting used nuclear fuel must have thick
shielding. The remaining 1 percent of the used fuel is plutonium. Plutonium is
formed when a neutron released during fission is absorbed by a U-238 atom. The
probability of such an absorption is low, but the absorption does occasionally
occur. Like uranium, plutonium emits primarily alpha and beta particles, but it
does emit some energetic gamma rays that require shielding.

2.3 Reprocessing, Recycling, and High-Level Waste

When nuclear power was introduced in the United States in the late 1950s,
developers expected to reprocess and recycle the used fuel, resulting in a closed
fuel cycle. There are three reasons for reprocessing and recycling:
1. The uranium in the used fuel could be utilized.
2. Plutonium, much of which fissions like U-235, could be used to generate
power.
3. Less than 5 percent of the used fuel would be sent to the repository, vastly
reducing the amount of repository space needed.
Reprocessing technology was developed in the United States in the 1940s, and
several reprocessing methods have been used. The PUREX (Plutonium Uranium
Extraction) process was used by the U.S. government to reprocess used fuel
taken from reactors that were run by the federal government (not commercial
reactors) with the goal of extracting plutonium and using it to make nuclear
weapons. In the PUREX process, used nuclear fuel is chopped up and dissolved
in concentrated nitric acid. The uranium and plutonium are removed and the
remaining 3 percent of the used fuel, which is still dissolved in the nitric acid
solution, is pumped to underground tanks. To prepare the high-level waste for