Containment of uranium in the proposed Egyptian geologic repository for radioactive waste using hydroxyapatite.

Conference · Fri Aug 01 04:00:00 EDT 2003

OSTI ID:1004367

Moore, Robert Charles; Hasan, Ahmed Ali Mohamed ^[1]; Headley, Thomas Jeffrey; Sanchez, Charles Anthony ^[2]; Zhao, Hongting; Salas, Fred Manuel; Hasan, Mahmoud A ^[1]; Holt, Kathleen Caroline

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1. Egyptian Atomic Energy Authority, Cairo, Egypt
2. University of Arizona, Yuma, AZ

Currently, the Egyptian Atomic Energy Authority is designing a shallow-land disposal facility for low-level radioactive waste. To insure containment and prevent migration of radionuclides from the site, the use of a reactive backfill material is being considered. One material under consideration is hydroxyapatite, Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}, which has a high affinity for the sorption of many radionuclides. Hydroxyapatite has many properties that make it an ideal material for use as a backfill including low water solubility (K{sub sp} > 10{sup -40}), high stability under reducing and oxidizing conditions over a wide temperature range, availability, and low cost. However, there is often considerable variation in the properties of apatites depending on source and method of preparation. In this work, we characterized and compared a synthetic hydroxyapatite with hydroxyapatites prepared from cattle bone calcined at 500 C, 700 C, 900 C and 1100 C. The analysis indicated the synthetic hydroxyapatite was similar in morphology to 500 C prepared cattle hydroxyapatite. With increasing calcination temperature the crystallinity and crystal size of the hydroxyapatites increased and the BET surface area and carbonate concentration decreased. Batch sorption experiments were performed to determine the effectiveness of each material to sorb uranium. Sorption of U was strong regardless of apatite type indicating all apatite materials evaluated. Sixty day desorption experiments indicated desorption of uranium for each hydroxyapatite was negligible.

• Research Organization: Sandia National Laboratories
• Sponsoring Organization: USDOE
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 1004367
• Report Number(s): SAND2003-3104C
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ACTINIDES
AFFINITY
APATITES
CALCINATION
CARBONATES
CATTLE
CHEMISTRY
CONTAINMENT
DESORPTION
FISSION PRODUCTS
LOW-LEVEL RADIOACTIVE WASTES
MORPHOLOGY
NUCLEAR ENERGY
RADIOACTIVE WASTES
RADIOISOTOPES
SOLUBILITY
SORPTION
SURFACE AREA
URANIUM