Hydrothermal synthesis of hydroxyapatite and pollucite from calcium phosphate
- Toshiba Corp., Kawasaki (Japan)
- Kochi Univ. (Japan)
One of the methods of recovering uranium and plutonium in reprocessing plants is solvent extraction. Usually, TBP (tributyl phosphate: 2(C{sub 4}H{sub 9}O){sub 3}PO)/n-dodecane mixture has been used in such a solvent extraction process. Spent solvent premixed with calcium hydroxide (Ca(OH){sub 2}) is supplied to the pyrolysis reactor, where the TBP thermally decomposes and reacts with Ca(OH){sub 2} to form a powder of calcium phosphate. This powder consists of calcium pyrophosphate (Ca{sub 2}P{sub 2}O{sub 7}) and calcium metaphosphate (Ca(PO{sub 3}){sub 2}). It is desirable that these phosphates should be converted into the stable structure of hydroxyapatite and the radioactive materials should be immobilized into a stable compound which is highly durable, in order to maintain long-term radioactive waste stability. Hydroxyapatite (HAP:Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}) and aluminosilicate were easily synthesized using a hydrothermal process with mixing ratios of Ca/P = 1.67 (Ca(PO{sub 3}){sub 2} and Ca(OH){sub 2}) and Si/Al = 4 (SiO{sub 2} and Al(OH){sub 3}). The temperature was kept constant at 573 K for 60 minutes. Cesium (Cs) and Cerium (Ce) contained in Ca(PO{sub 3}){sub 2}, were found to take on a stable form in the pollucite (CsAlSi{sub 2}O{sub 6}) structure and the monazite (CePO{sub 4}) structure.
- OSTI ID:
- 382853
- Report Number(s):
- CONF-941075-; ISBN 1-55899-253-7; TRN: 96:025745
- Resource Relation:
- Conference: 18. international symposium on the scientific basis for nuclear waste management, Kyoto (Japan), 23-27 Oct 1994; Other Information: PBD: 1995; Related Information: Is Part Of Scientific basis for nuclear waste management 18. Part 2; Murakami, Takashi [ed.] [Ehime Univ., Matsuyama, Ehime (Japan). Dept. of Earth Sciences]; Ewing, R.C. [ed.] [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences]; PB: 690 p.; Materials Research Society symposium proceedings, Volume 353
- Country of Publication:
- United States
- Language:
- English
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