COMPARISON OF DIALKYL PHENYLPHOSPHONATES WITH TRI-n-BUTYL PHOSPHATE IN NITRATE SYSTEMS: EXTRACTION PROPERTIES, STABILITY, AND EFFECT OF DILUENT ON THE RECOVERY OF URANIUM AND THORIUM FROM SPENT FUELS
Di-n-butyl phenylphosphonate (DBPP) and di-sec-butyl phenylphosphonate (DSBPP) were investigated as possible substitutes for tri-n-butyl phosphate (TBP), the reagent presently employed in the reprocessing of uranium and thorium nuclear reactor fuels. The phenylphosphonates form complexes with uranium and thorium that are mostly insoluble in the aliphatic solvents commonly used as diluerts for TBP but that are soluble in other diluert type, for example, aromatics and CCl/sub 4/. Therefore, the phosphonates were diluted with aromatics and the TBP was diluted with both aliphatic and aromatic diluents. DSBPParomatic solutions showed advantages over TBP-aromatic solutions during batch contact with nitric acid systems in the following respects: higher uranium extractability (1.2 to 1.8 times higher); better stability to radiation and chemical degradation (1.3 times better); higher separation of uranium from thorium (U/Th, 10 times higher) and from flssion products (U/gross BETA , about 2.4 times higher; U/ gross gamma , about 1.4 times higher). Plutonium extractiong with DSBPP and with TBP were nearly identical. The TBP-aromatic solvent combination also showed advantages over the TBP-aliphatic solvert combination in regard to radiation stability (2.4 times better), uranium extractability (1.5 times better), plutonium(IV) extractabtlity (twice as good), U/gross gamma separation (3.1 times higher) and U/ gross BETA separation (2.4 times higher). The comparison of the DSBPP-- aromatic solvent combination with TBP in the usual aliphatic diluent was consequently much more favorable to DSBPP than comparison with the TBParomatic. DBPP-aromatic solutions extracted uranium, thorium, plutonium, and fission products better than did TBP in either diluert system, The uranium--thorium separability was between those of the two TBP systems, and the urarium-gross BETA - gamma separability was about the same as for the TBP-aromatic but better than the TBPaliphatic combination. Under irradiation the DBPParomatic was slightiy more stable than the TBP-aliphatic, but not as stable as the TBP-aromatic. Countercurrert batch testing with simulated Purex feeds verified the single-batch contact data pertaining to uranium extractions with each reagent system and also verified the differences between TBP-aliphatic and TBP-aromatic systems. The higher uranium extractability ahown by DSBPP and by BBPP in comparison with TBP suggests their use to permit lower aqueous nitric acid or nitrate salting concertrations in a urarium recovery operation, for example, to effect reduction in chemical costs and/or to alleviate problems in nitric acid evaporation and recovery from high-level radioactive waste solutions. Since use of aromatic instead of aliphatic diluents with TBP improves its uranium extractability and fission product separabtlity, such dtluents can be considered where the performance of the TBP-aliphatic combination is marginal. (auth)
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- US Atomic Energy Commission (AEC)
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-17-010738
- OSTI ID:
- 4732916
- Report Number(s):
- ORNL-3374
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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