WSRC-TR-2000-00162

Fused Glass Former Evaluation in the
5" Cylindrical Induction Melter

M. E. Stone
Westinghouse Savannah River Company
Aiken, SC 29808

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

This report has been reproduced directly from the best available copy.

Available for sale to the public, in paper, from:  U.S. Department of Commerce, National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161,  phone: (800) 553-6847,  fax: (703) 605-6900,  email:  orders@ntis.fedworld.gov   online ordering:  http://www.ntis.gov/support/ordering.htm

Available electronically at  http://www.osti.gov/bridge/

Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from: U.S. Department of Energy, Office of Scientific and Technical Information, P.O. Box 62, Oak Ridge, TN 37831-0062,  phone: (865 ) 576-8401,  fax: (865) 576-5728,  email:  reports@adonis.osti.gov

The bed expansions noted during processing with the fused glass former were similar to expansions noted during baseline process runs utilizing 25SrABS cullet. The fused glass former successfully mitigated the severe bed expansions noted during calcination interlock recovery. The fused glass former reduced the severity of the expansion during high cerium runs, but still required manual intervention to keep the expansion in the melter.

A batch process to vitrify the americium and curium currently stored in F-canyon has been developed and tested. The batch process utilizes an induction melter to dry, calcine, and vitrify a batch utilizing 25SrABS cullet as the glass former. Severe bed expansions were noted during recovery from upset conditions in the vitrification process at the 5" Cylindrical Induction Melter (CIM) pilot facility. A series of crucible tests were conducted to investigate the cause of the severe bed expansions during recovery from an interlock during the calcination phase of the process [14].

Bed expansions were noted in the crucible tests between 1100 and 1250°C, apparently caused by surrogate oxides trapped in a highly viscous glass at the bottom of the crucible. The 25SrABS cullet was added to the crucible, then dried oxalate added on top. Some of the dried oxalate sank into the pores of the cullet and became trapped when the cullet slumped and formed a glassy block at the bottom of the crucible. When the cerium in the feed was thermally reduced, the oxygen was trapped in the glass causing a highly porous expansion. Fusing the cullet into a solid block prior to adding the dried oxalate prevented the oxalate from penetrating into the cullet bed and eliminated the expansions. Based on the success of these crucible tests, full-scale tests were conducted in the 5" CIM pilot facility.

Ten full-scale tests of the fused glass former process were conducted, see Table 1 in Attachment I. The fused glass former is formed by melting 25SrABS beads or cullet to form a 2 3/4" deep glass pool in the melter, then allowing the melter to cool to room temperature. During the tests, the fused glass former for most runs was formed by adding 1315.4 grams of 25SrABS beads to the melter prior to initiating the cool-down sequence of the prior run, allowing 25 minutes for the beads to melt, then initiating the cool-down sequence. The fused glass former created in this manner had a milky appearance, was sealed along the sides of the melter, and typically contained several small cracks along the surface. The oxalate slurry was fed on top of the fused glass former and the run was dried, calcined, and vitrified using the standard vitrification cycle.

Observations of the bed expansion through the bubbler penetration were made during processing with 25SrABS cullet and fused glass former tests. Measurements of the height of the foam in the melter were obtained during some runs with an alumina dipstick to augment the visual observations. The thermal profile of the melter was also used as an indirect indication of the height of the bed expansion.

Baseline Runs

The initial test (CIM5 TTR Run #34) of the fused glass former process in the 5" CIM was curtailed by the failure of the melter drain tube just after beginning the 75 minute soak period. The temperature profile indicated that the bed expansion was reduced by the fused glass former versus cullet. During a normal cullet run, the temperature as indicated by thermocouple T1B (see Figure 11 for T/C locations) initially decreases as the foam in the melter insulated the top of the melter from heat in the bottom of the melter, but then rises sharply as the foam reaches the same elevation as T1B. The fused glass former run showed a temperature decrease without the subsequent sharp increase typical during a cullet run, indicating that the foam did not reach T1B.

After installation of CIM5-A, the replacement platinum melter vessel, adjustments were required to the standard vitrification cycle to re-establish the desired thermal profile [15]. Three fused glass former runs were conducted during the transition to the new vitrification cycle (CIM5A-5, CIM5A-9, and CIM5A-13). The bed expansions during these runs showed no improvements over cullet processed with the same power profiles, as shown in Table 2. The bed expansion with fused glass former was worse during CIM5A-9 than a cullet run with the same profile.

Two baseline runs were conducted after establishment of the revised vitrification cycle (CIM5A-16 and CIM5A-17). The bed expansions during these runs also showed no improvements over cullet, although the onset of the expansion was delayed approximately 10 minutes during fused glass former tests, with onset typically near run time 355 minutes versus 345 minutes for cullet tests.

The bed expansions occurred as the surrogate oxalate was incorporated into the melt pool at temperatures between 1300 and 1400°C. The expansions could be the result of a shift in equilibrium for 4Ce⁺⁴O_{2 ®} 2Ce⁺³₂O₃ + O₂ in the glass matrix versus the oxide bed or could be caused by cerium reduction as a cold region in the oxide bed is absorbed into the melt pool. The results suggest that trapping cerium oxides in the cullet bed is not likely the primary mechanism causing the bed expansions experienced during baseline processing.

Calcination Interlock Recovery

When cullet is used as the glass former, recovery from a calcination interlock results in a severe bed expansion [14]. Three runs employing fused glass formers were conducted with interlocks during the calcination phase of the vitrification cycle. Two runs were interlocked 251 minutes into the vitrification cycle (CIM5A-18 and CIM5A-20) while CIM5A-19 was interlocked at 150 minutes. All runs were allowed to cool to room temperature overnight prior to restarting. The runs with fused glass former produced small expansions that were very similar to the expansions noted during baseline runs.

High Cerium Run

CIM5A-23 was conducted with cerium as the surrogate for americium and curium instead of erbium. The feed solution (SURR-1616) contained 1.87 times the typical amount of cerium. The onset of the bed expansion was delayed ten minutes to run time 370 minutes and installation of the bubbler was delayed during the run to allow the bed expansion to run its course. The expansion lifted the melter cover and required manual intervention to push the glass foam back into the melter. A high cerium run with 25SrABS cullet (CIM5A-32) was conducted with the same surrogate feed. The bed expansion during the cullet run lifted the melter cover and required repeated manual intervention to push the glass back into the melter.

The following conclusions were drawn from the tests:

1. The fused glass former produced bed expansions that were similar to that experienced with cullet runs during baseline tests.
2. The fused glass former process mitigated expansions during recovery from an interlock that occurs during the calcination phase of the heat cycle.
3. The fused glass former did not prevent high cerium (1.87X) concentrations from causing a severe bed expansion, although the expansion was less severe than experienced with a cullet run.

1. WSRC-NB-99-00173, ITS Research and Development 5" Cylindrical Induction Melter Development 11/1/99 – 3/13/2000.
2. WSRC-NB-2000-00068, ITS Research and Development 5" Cylindrical Induction Melter (CIM5A).
3. WSRC-NB-99-00135, Coupled Precipitator One.



Run Plans

4. T. M. Jones and D. C. Witt, CIM5 TTR Run #34 – Oxalate Precipitate on Solid 25SrABS Puck (U), SRT-AMC-2000-00005, January 21, 2000.
5. T. M. Jones and D. C. Witt, CIM5A-5 Oxalate Precipitate on Solid 25SrABS Puck (U), SRT-AMC-2000-00016, February 10, 2000.
6. T. M. Jones and D. C. Witt, CIM5A-9 Fused Glass Former Characterization Run by Modified Power Input (U), SRT-AMC-2000-00020, February 24, 2000.
7. T. M. Jones and D. C. Witt, CIM5A- 49 wt% Ln 25SrABS Fused Glass Former Run (U), SRT-AMC-2000-00024, March 3, 2000.
8. T. M. Jones and D. C. Witt, CIM5A-16 49 wt% Ln 25SrABS Fused Glass Former Run with Elevated Vessel Coil (U), SRT-AMC-2000-00028, March 13, 2000.
9. T. M. Jones and D. C. Witt, CIM5A-17 Repeat Fused Glass Former Run with Elevated Vessel Coil (U), SRT-AMC-2000-00029, March 14, 2000.
10. T. M. Jones and D. C. Witt, CIM5A-18 Fused Glass Former Calcination Interlock at Run Time =251 (U), SRT-AMC-2000-00030, March 15, 2000.
11. T. M. Jones and D. C. Witt, CIM5A-19 Fused Glass Former Calcination Interlock at Run Time =150 (U), SRT-AMC-2000-00031, March 20, 2000.
12. T. M. Jones and D. C. Witt, CIM5A-20 Repeat Fused Glass Former Calcination Interlock at Run Time =251 (U), SRT-AMC-2000-00033, March 22, 2000.
13. T. M. Jones and D. C. Witt, CIM5A-23 1.87X Cerium/No Erbium Fused Glass Former Run (U), SRT-AMC-2000-00035, March 28, 2000.
    

Other References

14. M. E. Stone and J. W. DuVall, Bed Expansion Crucible Tests, WSRC-TR-2000-00050, February 7, 2000.
15. T. M. Jones, "Am/Cm Melter Processing Evaluation Following Reposistioning of the Vessel within the Induction Coils (U) WSRC-TR-2000-00138.

Attachment 1.  Run Data

Table 1.  5" CIM Runs with Fused Glass Former Process

Table 2.  Bed Expansions Noted during Fused Glass Former Tests

Attachment 2.  Temperature Plots

Figure 1.  CIM5 TTR Run #34: Fused Glass Former Run in Original Melter

 

Figure 2.  CIM5A-5: Fused Glass Former Run with New Melter and Original Power Profile.

 

 

Figure 3.   CIM5A-9: Fused Glass Former Run with Modified Power Profile

 

 

Figure 4.  CIM5A-13: Fused Glass Former Run with New Standard Power Profile

 

 

Figure 5.   CIM5A-16: Fused Glass Former Run with Raised Coil and Standard Power Profile

 

 

Figure 6. CIM5A-17: Repeat Fused Glass Former Run with Raised Coil and Standard Power Profile

 

 

Figure 7. CIM5A-18: Fused Glass Former Run with Calcination Interlock at Run Time = 251

 

 

Figure 8. CIM5A-19: Fused Glass Former Run with Calcination Interlock at Run Time = 150

 

 

Figure 9. CIM5A-20: Repeat Fused Glass Former Run with Calcination Interlock at Run Time = 251

 

 

Figure 10. CIM5A-23: Fused Glass Former Run with High Cerium Concentration

 

 

Figure 11. T/C Locations on 5" CIM Vessel