Tc Reductant Chemistry and Crucible Melting Studies with Simulated Hanford Low-Activity Waste

Kim, Dong-Sang; Soderquist, Chuck Z.; Icenhower, Jonathan P.; McGrail, B. Peter; Scheele, R.D.; McNamara, Bruce K.; Bagaasen, Larry M.; Schweiger, Michael J.; Crum, Jarrod V.; Yeager, John D.; Matyáš, Josef; P, Darnell, Lori; Schaef, Herbert T.; Owen, Antionette T.; Kozelisky, Anne E.; Snow, Lanee A.; Steele, Marilyn J.

doi:10.2172/15020035

Cited by 31 publications

(69 citation statements)

References 26 publications

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“…The engineering-scale tests ES-32A and 32B used both Re and Tc and found an overall good correlation between Re and Tc except for CRB migration: the CRB extraction measurements resulted in a significantly lower Tc concentration than Re (Pierce et al 2005), indicating that Re is a conservative CRB migration surrogate in engineering-scale tests. The crucible tests performed in a previous study on the Re/Tc volatilization (Kim et al 2005) also used both Re and Tc and obtained a very good agreement between Re and Tc. Therefore, Re was used for all the tests performed in this study because a broader set of non-radioactive Re tests could be conducted for less cost than radioactive Tc tests.…”

Section: Introductionmentioning

confidence: 85%

“…The simulant used in this study was the same as used in a previous study (Kim et al 2005), 5 M sodium "6 tank composite" simulated Hanford LAW developed by Rassat et al (2003). Table 4.1 shows the reagent masses used to prepare 1 L of liquid simulant.…”

Section: Simulant Descriptionmentioning

confidence: 99%

“…Table 4.2 also shows the compositions of HRTS soil and the resulting glass from the baseline formation. The soil composition given in Table 4.2 (designated as HRTS05) has been updated since the last study (Kim et al 2005), resulting in a slightly different target glass composition. …”

Section: Simulant Descriptionmentioning

confidence: 99%

“…Tasks 14 and 15 helped identify which mechanisms play an important role in the migration of Tc in the BV process. Task 14 focused on the volatilization of Tc from the melting feed and molten glass (Kim et al 2005), and Task 15 focused on the migration of Tc into the CRB (Hrma et al 2005). Based on the results from these scoping tests, additional tests were identified that will improve the understanding of Tc migration and clearly identify the dominant mechanisms.…”

Section: Introductionmentioning

confidence: 99%

“…Theses scoping tests helped identify which mechanisms play an important role in the migration of Tc in the BV process (Hrma et al 2005;Kim et al 2005). Based on the results from these scoping tests, additional tests were identified that will improve the understanding of Tc migration and clearly identify the dominant mechanisms.…”

mentioning

confidence: 99%

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Investigation of Tc Migration Mechanism During Bulk Vitrification Process Using Re Surrogate

Kim¹,

Bagaasen²,

Crum³

et al. 2006

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SummaryAs a part of bulk vitrification (BV) performance enhancement tasks, laboratory scoping tests were performed in FY 2004FY -2005 to explore possible ways to reduce the amount of soluble Tc in the BV waste package. Theses scoping tests helped identify which mechanisms play an important role in the migration of Tc in the BV process (Hrma et al. 2005;Kim et al. 2005). Based on the results from these scoping tests, additional tests were identified that will improve the understanding of Tc migration and clearly identify the dominant mechanisms.The additional activities identified from previous studies were evaluated and prioritized for planning for Tasks 29 and 30 conducted in FY 2006. Task 29 focused on the improved understanding of Tc migration mechanisms, and Task 30 focused on identifying the potential process changes that might reduce Tc/Re migration into the castable refractory block (CRB). This report summarizes the results from the laboratory-and crucible-scale tests in the laboratory for improved understanding of the Tc migration mechanism using Re as a surrogate performed in Task 29. Other tests performed in Task 30, which specifically aimed at testing changes to the BV process that might reduce Tc/Re migration into the CRB, will be reported in a separate report. The FY 2004 work also showed that Re is an excellent surrogate for Tc. Therefore, Re was used for all the tests performed in this study because a broader set of non-radioactive Re tests could be conducted for less cost than radioactive Tc tests.The water and molten ionic salt (MIS) capillary experiments suggested that the capillary force is a dominant mechanism for MIS penetration in the CRB, which was also supported by the preliminary modeling results.Hot-stage microscopy observations of the feed-melting and liquid-formation processes showed that the behavior of a dry blended feed and a feed prepared from liquid simulant was significantly different. A dry blended feed seemed to form a higher fraction of liquid than a feed prepared from liquid simulant, which could cause an increase in MIS migration into CRB. This may suggest that the information obtained in the full-scale tests conducted with dry blended feed may need to be verified with drier prepared feed in future operations.Thin-section MIS/Re profile measurements with FS-38B CRB samples provided new information on how the MIS and Re penetrate as the melt progresses.• For the CRB above the melt line, Re penetrates into the CRB by a vapor disposition mechanism, i.e., Re deposits when the CRB is cold, becomes molten as the temperature increases, and then penetrates further into the CRB by capillary action. The extent of penetration and the concentration of Re above the melt line is small.• For the CRB at the melt line, Re penetrates into the CRB through both the vapor deposition at the early stages of processing and then liquid MIS formation and penetration at later processing stages. The CRB at the melt line close to the glass interface exhibited the highest soluble Re concentration.• For...

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Section: Introductionmentioning

confidence: 85%

Section: Simulant Descriptionmentioning

confidence: 99%

Section: Simulant Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Investigation of Tc Migration Mechanism During Bulk Vitrification Process Using Re Surrogate

Kim¹,

Bagaasen²,

Crum³

et al. 2006

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Ab Initio Study of the Electronic Structure and Lattice Dynamics of Scheelite Type AgTcO₄

Mukherjee

Mondal

Kennedy

et al. 2023

Physica Status Solidi (b)

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Recently, ABO 4 -type ternary metal oxides have received considerable attention because of their wide range of properties and applications in fundamental physics, chemistry, and materials science. [1][2][3] Exploring the ABO 4 materials is both challenging and interesting because of the variety of structures that have been observed in these oxides. The most common structural types are scheelite, zircon, wolframite, monazite, baryte, fergusonite, and pseudoscheelite. These all contain BO 4 tetrahedra and temperature-and/or pressure-induced structural phase transitions between these are well documented; for example, the transformation from monazite to scheelite to zircon with increasing temperature and from zircon to monazite to scheelite with increasing pressure. [4] This structural versatility leads to a variety of physical features that enables a diverse and broad range of applications, distinguishing ABO 4 -type compounds from other materials. Applications include phosphors (ZrGeO 4 and HfGeO 4 ), battery materials (CaMoO 4 and SrWO 4 ), laser host materials (BaWO 4 and GdTaO 4 ), and scintillators (CdWO 4 and PbWO 4 ). [5] High pressure studies show that the scintillating properties of orthovanadates are better when compared to periodates. [6][7][8] Our recent study suggests that thallous perchlorate and perbromate can be used as inorganic scintillators, since there exists a charge-transfer character in the bands. [9] It is generally found that the structure of the ABO 4 oxides favored under ambient conditions is dependent on the smaller, more highly charged, B-type cation. Phosphates, silicates, vanadates, chromates, and arsenates are known to crystallize in the zircon-type structure, although several phosphates and arsenates crystallize in the quartz structure, whereas the scheelite structure is observed for numerous molybdates, tungstates, iodates, and germanates. [10] The ABO 4 -type compounds where B is technetium (Tc), that is, the pertechnetate group (TcO À1 4 ) have been less well explored. Tc is the first man-made transition metal, and it is the lightest radioactive synthetic element. Tc is the mostly widely utilized radiopharmaceutical and it has been found useful as a corrosion inhibitor in the steel industry, as a superconductor at a very low temperature [11] and also as an environmental water tracer. [12,13] Transition-metal oxides are fascinating to study because of their high melting temperatures and densities, and the capacity of transition metals to form compounds with other elements as well as the potential for transmutation from one compound to another. [14,15] Of the 21 known isotopes of Tc, 99 Tc is the most abundant, and it is a significant by-product of the fission of

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Behavior of technetium in nuclear waste vitrification processes

Pegg

2015

J Radioanal Nucl Chem

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Nearly 100 tests were performed with prototypical melters and off-gas system components to investigate the extents to which technetium is incorporated into the glass melt, partitioned to the off-gas stream, and captured by the off-gas treatment system components during waste vitrification. The tests employed several simulants, spiked with 99mTc and Re (a potential surrogate), of the low activity waste separated from nuclear wastes in storage in the Hanford tanks, which is planned for immobilization in borosilicate glass. Single-pass technetium retention averaged about 35 % and increased significantly with recycle of the off-gas treatment fluids. The fraction escaping the recycle loop was very small.

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Tc Reductant Chemistry and Crucible Melting Studies with Simulated Hanford Low-Activity Waste

Cited by 31 publications

References 26 publications

Investigation of Tc Migration Mechanism During Bulk Vitrification Process Using Re Surrogate

Investigation of Tc Migration Mechanism During Bulk Vitrification Process Using Re Surrogate

Ab Initio Study of the Electronic Structure and Lattice Dynamics of Scheelite Type AgTcO₄

Behavior of technetium in nuclear waste vitrification processes

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Tc Reductant Chemistry and Crucible Melting Studies with Simulated Hanford Low-Activity Waste

Cited by 31 publications

References 26 publications

Investigation of Tc Migration Mechanism During Bulk Vitrification Process Using Re Surrogate

Investigation of Tc Migration Mechanism During Bulk Vitrification Process Using Re Surrogate

Ab Initio Study of the Electronic Structure and Lattice Dynamics of Scheelite Type AgTcO4

Behavior of technetium in nuclear waste vitrification processes

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Product

Resources

About

Ab Initio Study of the Electronic Structure and Lattice Dynamics of Scheelite Type AgTcO₄