Dissolution of uranium and plutonium oxide using TBP-HNO complex

Miyahara, Sachiko ; not registered; Shiba, Masanori*; not registered; not registered  ; not registered; not registered 

The current technology for the selective separation of plutonium and uranium from spent nuclear fuel (MOX) using TBP-HNO complex is being developed (Powdered fuel extraction process). It is promising to simplify the reprocessing process for the selective separation because of its potential to unite the chemical processes, dissolution process using nitric acid and co-extraction process using TBP solvent, and to operate under the ambient pressure and at relatively "mild" temperature. Plutonium oxide has reported to provide slower dissolution than uranium oxide in nitric acid. In this work dissolution behaviors of plutonium into TBP-HNO complex from powdered plutonium and uranium mixed oxide were examined. The powdered MOX fuel (average particles size 10m) was prepared from PuO-O pellets by heating for 4 hours at 400C. The prepared powder was dissolved into TBP-4.74mol/L HNO complex and was stirred for 300 minutes. In the test with 6 grams of powdered MOX fuel and 20 mL of the TBP-HNO complex, the concentration of plutonium reached 0.17 mol/L and about 90 percent of plutonium was dissolved. It is experimentally confirmed plutonium was dissolved into the TBP-HNO complex from plutonium and uranium mixed oxide. The early dissolution rate was almost the same as that obtained with nitric acid solution. It is likely to predict the dissolution rate from the rate for nitric acid solution. Americium that was contained in the MOX fuel was also dissolved into the TBP-HNO complex, but was slower than plutonium.