TAILORING INORGANIC SORBENTS FOR SRS STRONTIUM AND ACTINIDE SEPARATIONS: OPTIMIZED MONOSODIUM TITANATEPHASE II INTERIM REPORT FOR EXTERNAL RELEASE
This document provides an interim summary report of Phase II testing activities for the development of a modified monosodium titanate (MST) that exhibits improved strontium and actinide removal characteristics compared to the baseline MST materials. The activities included determining the key synthesis conditions for preparation of the modified MST, preparation of the modified MST at a larger laboratory scale, demonstration of the strontium and actinide removal characteristics with actual tank waste supernate and characterization of the modified MST. Key findings and conclusions include the following: (1) Samples of the modified MST prepared by Method 2 and Method 3 exhibited the best combination of strontium and actinide removal. (2) We selected Method 3 to scale up and test performance with actual waste solution. (3) We successfully prepared three batches of the modified MST using the Method 3 procedure at a 25-gram scale. (4) Performance tests indicated successful scale-up to the 25-gram scale with excellent performance and reproducibility among each of the three batches. For example, the plutonium decontamination factors (6-hour contact time) for the modified MST samples averaged 13 times higher than that of the baseline MST sample at half the sorbent concentration (0.2 g L{sup -1} for modified MST versus 0.4 g L{sup -1} for baseline MST). (5) Performance tests with actual waste supernate demonstrated that the modified MST exhibited better strontium and plutonium removal performance than that of the baseline MST. For example, the decontamination factors for the modified MST measured 2.6 times higher for strontium and between 5.2 to 11 times higher for plutonium compared to the baseline MST sample. The modified MST did not exhibit improved neptunium removal performance over that of the baseline MST. (6) Two strikes of the modified MST provided increased removal of strontium and actinides from actual waste compared to a single strike. The improved performance exhibited by the modified MST indicates that fewer strikes of the modified MST would be needed to successfully treat waste that contain very high activities of {sup 90}Sr and alpha-emitting radionuclides compared to the baseline MST. (7) Reuse tests with actual waste confirmed that partially loaded MST exhibits reduced removal of strontium and actinides when contacted with fresh waste. (8) Samples of modified MST prepared by Method 3 and the baseline MST exhibited very similar particle size distributions. (9) Dead-end filtration tests showed that the modified MST samples exhibited similar filtration characteristics as the baseline MST sample. (10) Performance testing indicated no change in strontium and neptunium removal after storing the modified MST for 6-months at ambient temperature. The results suggested that plutonium removal performance may be decreased slightly after 6-months of storage. However, the change in plutonium removal is not statistically significant at the 95% confidence limit. Based on these findings we recommend continued development of the modified MST as a replacement for the baseline MST for waste treatment facilities at the Savannah River Site.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC09-96SR18500
- OSTI ID:
- 891993
- Report Number(s):
- WSRC-STI-2006-00072; TRN: US0605509
- Country of Publication:
- United States
- Language:
- English
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