| Fig. 7-5 |
Concept of an actinide transmutation (burning) cycle using the
nitride/pyrochemical process
Actinide salts (nitrate) are partitioned from high-level radioactive
wastes which are fed into the first-stratum commercial fuel cycle.
These salts are converted to solid microspheres by a sol-gel technique.
The gel microsphere is formed as a mixture of actinide oxide and
carbon, and is converted to mononitride by heating in a N2+H2 stream. The microstructure of uranium mononitride produced is
shown in the photograph. In this carbothermic reduction process,
15N2 enriched nitrides can be synthesized, by using 15N2 gas instead of natural nitrogen. The nitride fuel is completed
in the form of TiN-coated particles.
After irradiation to high burnup in a dedicated actinide burner,
the spent nitride fuels are reprocessed with the pyrochemical
process in the second stratum actinide burner cycle. The nitrides
are fed into the molten-salt electro-refiner, as shown in this
figure. Since the solubility of nitrogen in molten salt is small
(~100 ppm), 15N2 gas enriched in the nitrides is readily recovered. While the
nitrides are anodically dissolved, purified actinide metals are
recovered at the cathode. |
