Buoyant Response of the Tank 241-SY-101 Crust to Transfer and Back-Dilution

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The mixer pump installed in Hanford Tank 241-SY-101 (SY-101) in July 1993 has prevented the large buoyant displacement gas release events (BD GRE) it has historically exhibited. But the absence of periodic disruption from GREs and the action of mixing have allowed the crust to grow. The accelerated gas retention has resulted in over 30 inches of waste level growth and the flammable gas volume stored in the crust has become a hazard. To remediate gas retention in the crust and the potential for buoyant displacement gas releases from below the crust, SY-101 will be diluted in the fall of ... continued below

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36 p.

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Stewart, CW November 8, 1999.

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Description

The mixer pump installed in Hanford Tank 241-SY-101 (SY-101) in July 1993 has prevented the large buoyant displacement gas release events (BD GRE) it has historically exhibited. But the absence of periodic disruption from GREs and the action of mixing have allowed the crust to grow. The accelerated gas retention has resulted in over 30 inches of waste level growth and the flammable gas volume stored in the crust has become a hazard. To remediate gas retention in the crust and the potential for buoyant displacement gas releases from below the crust, SY-101 will be diluted in the fall of 1999 to dissolve a large fraction of the solids in the tank. The plan is to transfer waste out and back-dilute with water in several steps of about 100,000 gallons each. Back-dilution water may be added at the transfer pump inlet, the base of the mixer pump, and on top of the crust. The mixer pump will continue to be required to prevent formation of a deep nonconnective layer and resumption of BD GREs. Therefore, it is vital to ensure that the transfer and back-dilution processes do not significantly degrade the pump's effectiveness. Part of the strategy to avoid mixer pump degradation is to keep the base of the crust layer well above the pump inlet, which is 236 inches above the tank bottom. The maximum transfer for which an equal back-dilution is possible without sinking the crust is 90 kgal if water is injected at the 96-inch transfer pump inlet and 120 kgal for injection at the 9-inch mixer pump burrowing ring. To keep the crust base above the lowest observed elevation of 295 inches, transfer and back-dilution must be limited to 143 kgal and 80 kgal, respectively, for the 96-inch back-dilution and 175 kgal with a 112 kgal back-dilution using the 9-inch back-dilution elevation. These limits can be avoided by adding water to the top of the crust to dissolve the negatively buoyant layers. If 20 kgal of water is placed on top of the crust and the rest of the back-dilution is placed under the crust, back-dilution becomes limited by crust sinking at a 128 kgal transfer using the 96-inch injection point and at 160 kgal at 9 inches. The crust base remains well above the 295-inch minimum, and crust base elevation does not limit transfer volume. This result shows that top dilution is very beneficial in providing operational flexibility to the transfer and back-dilution process.

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36 p.

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INIS; OSTI as DE00014408

Medium: P; Size: 36 pages

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  • Other Information: PBD: 8 Nov 1999

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  • Report No.: PNNL-13066
  • Report No.: 820201000
  • Grant Number: AC06-76RL01830
  • DOI: 10.2172/14408 | External Link
  • Office of Scientific & Technical Information Report Number: 14408
  • Archival Resource Key: ark:/67531/metadc622151

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Creation Date

  • November 8, 1999

Added to The UNT Digital Library

  • June 16, 2015, 7:43 a.m.

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  • April 12, 2017, 2:10 p.m.

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Stewart, CW. Buoyant Response of the Tank 241-SY-101 Crust to Transfer and Back-Dilution, report, November 8, 1999; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc622151/: accessed September 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.