Dynamics of Crust Dissolution and Gas Release in Tank 241-SY-101

Rassat, Scot D.; Stewart, Charles W.; Wells, Beric E.; Kuhn, W.L.; Antoniak, Z.I.; Cuta, Judith M; Recknagle, Kurtis P.; Terrones, Guillermo; Viswanathan, Vilayanur V; Sukamto, Johanes H; Mendoza, Donaldo P

doi:10.2172/965217

Cited by 13 publications

(43 citation statements)

References 7 publications

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“…(3 m) after a redistribution event in April to May 1999. Based on comparison of neutron data and crust buoyancy calculations, the average void fraction in the submerged part of the crust was estimated to be 0.24, which resulted in a gas volume of about 10,000 scf (Rassat et al 2000).…”

Section: -8mentioning

confidence: 99%

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Data Observations on Double Shell Tank (DST) Flammable Gas Watch List Tank Behavior

Hedengren¹

2000

115

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Section: -8mentioning

confidence: 99%

“…The floating crust layer consists of the same material as the nonconvective layer but contains a higher gas fraction and is somewhat stronger based on experience with the crust in SY-101 (Rassat et al 2000).…”

Section: Characteristics and Properties Of The Main Waste Layersmentioning

confidence: 99%

Data Observations on Double Shell Tank (DST) Flammable Gas Watch List Tank Behavior

Hedengren¹

2000

115

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“…However, with both the pumping and water spray shut off, the only mechanisms available to mix the water with the brine and continue dissolution are diffusion and natural convection. Diffusion is extremely slow in a liquid, and convection is limited to thin layers by the density gradient until mixing is almost complete (Rassat et al 2000). Therefore, while the presence of excess solvent could delay and reduce the response of gas release to cessation of pumping and water addition, the physical mechanisms involved in the mixing process dictate that gas release would fall far below the rate induced during pumping.…”

Section: Headspace Hydrogen Concentrationmentioning

confidence: 99%

“…Rassat et al (2000), Mahoney et al (2000) and Johnson et al (2001) describe in detail the process, theory, and events. The initial 120-inch crust layer in this tank was comparable in thickness to the non-supernate waste in U-107 but contained almost twice the gas.…”

Section: Gas Releases During Dissolution Of Sy-101 Crustmentioning

confidence: 99%

Gas Releases During Saltcake Dissolution for Retrieval of Single-Shell Tank Waste

Stewart¹

2001

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It is possible to retrieve a large fraction of soluble waste from the Hanford single-shell waste tanks (SST) by dissolving it with water. This retrieval method will be demonstrated in U-107 and S-112 in the next few years. If saltcake dissolution proves practical and effective, many of the saltcake SSTs may be retrieved by this method. Many SSTs retain a large volume of flammable gas that will be released into the tank headspace during retrieval as the waste dissolves. This report describes the physical processes that control dissolution and gas release. Calculation results are shown describing the headspace hydrogen concentration transient during dissolution. The observed spontaneous and induced gas releases from SSTs are summarized, and the dissolution of the crust layer in SY-101 is discussed as a recent example of full-scale dissolution of saltcake containing a very large volume of retained gas. The report concludes that the dissolution rate is self-limiting, and gas release rates are relatively low. iv v Executive SummarySaltcake dissolution is a proposed method for retrieving water-soluble salts from the Hanford SSTs. Water will be sprayed on the waste surface to dissolve the soluble fraction of the waste while the resulting brine is pumped out of the tank with an existing saltwell pumping system. Because a large fraction of typical saltcake waste is soluble, most of the waste in an SST can, in principle, be retrieved with almost the same time and cost as a typical interim stabilization campaign. A proof-of-concept test (limited to approximately 100,000 gal of brine) is planned in U-107 during the fall of 2001. A full-tank retrieval demonstration system is being planned for S-112 in 2002. If saltcake dissolution proves practical and effective, many of the saltcake SSTs may be retrieved by this method.Many of the SSTs contain a large volume of flammable gas that will be released into the tank headspace as the waste dissolves. U-107 contains 180 ± 60 cubic meters (6,400 ± 2,000 scf) of retained gas, and S-112 is estimated to retain a much smaller volume of 46 ± 23 cubic meters (1,600 ± 800 scf). This report investigates the potential hazard of flammable gas that will be released during the dissolution process.Dissolution is expected to release this gas in proportion to the fraction of the waste in which the soluble solids are dissolved. This process is self-limiting and controllable. Water or dilute brine capable of dissolving solids is less dense than the saturated liquid in equilibrium with the solids. Therefore, the solvent cannot penetrate below the pre-existing interstitial liquid in the waste; and dissolution can only occur in waste that is not saturated with liquid. Once the solvent has become saturated, it is no longer capable of further dissolution and forms a barrier to the less dense liquid from above.This means that dissolution, and the associated gas release, can proceed no faster than the interstitial liquid can drain away. This is the primary mechanism that limits dissolution-induced g...

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“…Prior to the transfer activities, SY-101 had the most concentrated waste of any of the DSTs and had developed a crust layer approximately 3 m thick. Approximately 15,000 scf of gas was retained in the tank (Rassat et al 2000). SY-102 continues to serve as a receiver tank for process water and salt-well pumped liquid from other 200 West Area tanks.…”

Section: • Heterogeneous Waste Distributionmentioning

confidence: 99%

Material Balance Assessment for Double-Shell Tank Waste Pipeline Transfer

Onishi¹,

Wells²,

Hartley³

et al. 2001

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SummaryPacific Northwest National Laboratory researchers developed a material balance assessment methodology based on conservation of mass to detect possible waste leaking and mis-routings during the pipeline transfer of double-shell tank waste with variable waste properties and tank conditions at Hanford. It is intended to be a backup method to pit leak detectors.The main factors causing variable waste properties and tank conditions are waste density changes caused by chemical reactions and gas generation/retention/release, the existence of a crust layer, and waste surface disturbance due to mixer pump operation during the waste transfer. If waste properties and tank conditions were constant, this mass-based material balance methodology could be simplified to a volume-based material balance.The material balance assessment methodology was applied to three waste transfers: AN-105 first transfer of 911,400 gallons of in-line diluted supernatant liquid; AN-105 second transfer with 673,000 gallons of liquid waste; and AZ-102 slurry transfer of 150,000 gallons. Three instrumentation setups were considered: (A) feed and receiver tank levels and diluent flow meter; (B) flow meter at the beginning of the transfer pipeline and receiver tank level; and (C) diluent, feed, and receiver tank levels.

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Dynamics of Crust Dissolution and Gas Release in Tank 241-SY-101

Cited by 13 publications

References 7 publications

Data Observations on Double Shell Tank (DST) Flammable Gas Watch List Tank Behavior

Data Observations on Double Shell Tank (DST) Flammable Gas Watch List Tank Behavior

Gas Releases During Saltcake Dissolution for Retrieval of Single-Shell Tank Waste

Material Balance Assessment for Double-Shell Tank Waste Pipeline Transfer

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