Measurements of waste tank passive ventilation rates using tracer gases

Huckaby, J.L.; Olsen, K.B.; Sklarew, D.S.; Evans, J. C.; Remund, K.M.

doi:10.2172/552792

Cited by 21 publications

(44 citation statements)

References 7 publications

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“…Only a single estimate of breathing rate based on tracer gas studies is usually available for most tanks (Huckaby et al 1997). That estimate may be based on the average of multiple measurements taken over a number of different days, but usually the data do not span the seasonal variation of ventilation.…”

Section: Conceptual Modelmentioning

confidence: 99%

Dryout modeling in support of the organic tank safety project

Simmons¹

1998

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Section: Conceptual Modelmentioning

confidence: 99%

Dryout modeling in support of the organic tank safety project

Simmons¹

1998

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“…(Ventilation rates in DCRTs are currently being measured, and the results will be incorporated into future versions of this document.) This "administrative" ventilation is significantly less than even the 2-15 scfm passive ventilation rates that have been measured in SSTs (Huckaby et al 1997). Because of this limited ventilation, flammable gas concentrations in DCRTs are often calculated to be significantly higher than they are in SSTs, where under normal circumstances those gases are at concentrations well below the level of concern.…”

Section: Dcrtsmentioning

confidence: 95%

“…Huckaby et al (1997) found that mixing times in S-102 (an SST) were about one hour, apparently because of natural convection. The TEMPEST modeling of the same tank (Antoniak and Recknagle 1997) was in agreement with the observations.…”

Section: 1mentioning

confidence: 99%

“…To avoid the tendency of ammonia to collect on any available surface, a non-condensable gas like helium could be used as a tracer using the same method as is currently being used to assess passive ventilation flow rates in SSTs (Huckaby et al 1997). A volume of helium could be injected into the catch tank through the high DP tube that would bring the average concentration to a few hundred ppm.…”

Section: Confirming Ventilation Flow Ratesmentioning

confidence: 99%

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Flammable gas issues in double-contained receiver tanks. Revision 2

Peurrung¹,

Mahoney²,

Stewart³

et al. 1998

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SummaryFour double-contained receiver tanks (DCRTs) at Hanford will be used to store salt-well pumped liquids from tanks on the Flammable Gas Watch List. This document was created to serve as a technical basis or reference document for flammable gas issues in DCRTs. The document identifies, describes, evaluates, and attempts to quantify potential gas carryover and release mechanisms. It estimates several key parameters needed for these calculations, such as initial aqueous concentrations and ventilation rate, and evaluates the uncertainty in those estimates. It justifies the use of the Schumpe model for estimating vapor-liquid equilibrium constants. It identifies several potential waste compatibility issues (such as mixing and pH or temperature changes) that could lead to gas release and provides a basis for calculating their effects. It evaluates the potential for gas retention in precipitated solids within a DCRT and whether retention could lead to a buoyant displacement instability (rollover) event. It discusses rates of radiolytic, thermal, and corrosive hydrogen generation within the DCRT. It also describes in detail the accepted method of calculating the lower flammability limit (LFL) for mixtures of flammable gases.The report incorporates these analyses into two models for calculating headspace flammability, one based on instantaneous equilibrium between dissolved gases and the headspace and one incorporating limited release rates based on mass-transfer considerations. Finally, it demonstrates the use of both models to estimate headspace flammable gas concentrations and minimum ventilation rates required to maintain concentrations below 25% of the LFL. The report describes the methodology, the results at the only known (but probably highly underestimated) ventilation rate of 3 cfh, and the parametric sensitivity of the results.However, no actual predictions of DCRT headspace flammability are implied. This document is intended to provide background information for future DCRT modeling and recommendations for improving the technical basis of modeling. Although modeling results are presented here, the waste properties and potential pumping scenarios are so variable as to require case-by-case modeling for a safety basis. This document, therefore, does not and cannot provide a safety basis but rather guidance (based on current knowledge) as to conditions that a safety basis should meet.We have identified no major flaws in the approach previously published in a calc-note by Hedengren et aL (1997). Although we developed a somewhat different mathematical model for predicting flammable gas concentrations within the DCRT, we found little difference between our predictions and those from Hedengren et aL when the same initial dissolved gas concentrations were assumed. We also found that for most purposes the assumption of equilibrium does not produce large overestimates of DCRT headspace flammability until ventilation rates are much higher than the 3 cfh assumed in the other analyses. The analyses in this document in...

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“…Gas tracer studies have been conducted to determine the passive ventilation rates of U-102, U-103, U-105, U-106, and U-111 over periods of one to two months (Huckaby et al 1997 the U-farm tanks range from 1.3 to 5.2 ft 3 /min with an average of 2.5 ft 3 /min. The tracer tests on S-102 showed a range of 1.2 to 3.4 scfm with an average of 2.1 scfm.…”

Section: Estimated Ventilation Ratesmentioning

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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Measurements of waste tank passive ventilation rates using tracer gases

Cited by 21 publications

References 7 publications

Dryout modeling in support of the organic tank safety project

Dryout modeling in support of the organic tank safety project

Flammable gas issues in double-contained receiver tanks. Revision 2

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

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