Gas retention and release behavior in Hanford double-shell waste tanks

Abstract

DISCLAIMER'letter reporting refinement of flammable gas generatiodretention models using void meter and retained gas sampling data."The data obtained from operating the void fraction instrument 0 (Stewart et al. 1996a), and retained gas sampler (RGS) (Shekarriz et al. 1997) have determined the amount and composition of gas retained in the wastes in the six double-shell tanks on the Flammable Gas Watch List (Johnson et al: 1997). The interpretation of those data and the models for gas retention and release developed or improved as a result represent significant progress toward an adequate understanding of the mechanisms of gas generation, retention, and release. This report summarizes the VFI and RGS data and presents the models these data have enabled us to develop.. iii AbstractThis report describes the current understanding of flammable gas retention and release in Hanford double-shell waste tanks AN-103, AN-104, AN-105 The applicable data available from the void fraction instrument, retained gas sampler, ball rheometer, tank characterization, and field monitoring are summarized. Retained gas volumes and void fractions are updated with these new data -Using the retained gas compositions from the retained gas sampler, peak dome pressures during a gas burn are calculated as a function of the fraction of retained gas hypothetically released instantaneously into the tank head space. Models and criteria are given for gas generation, initiation of buoyant displacement, and resulting gas release; and predictions are compared with observed tank behavior. V Summary .The gas retention and release behaviors of Hanford double-shell tanks (DSTs) on the Hammable Gas Watch List (FGWL), were characterized in detail using the ball rheometer and void fraction instrument 0 from December 1994 to May 1996. These are reported in Stewart et al. (1996a). Additional data on gas .composition and void fraction have since become available on four of these tanks (AW-101, AN-103, AN-104, and AN-105) using the retained gas sampler (RGS) from March through September 1996 and are described in Shekarriz et al. (1997).The main objective of the work presented in this report is improving the models for gas retention and release based on these data and updating the original gas retention and release calculations with the new RGS and core sample data-Because of this extensive characterization effort, we have a better knowledge and understanding of these DSTs than of any other Hanford tanks. We include models that help explain current gas retention and release behavior and examine the potential for other tanks to exhibit hazardous episodic gas releases. The models developed for gas generation based on waste sample testing are also summarized. While none of these models have been formally ve$i,ed and validated for safety analysis, they are consistent with the extant body of data and observations. The updates to earlier calculations and improvements to gas generation, retention, and release models are summarized below. G a s Generation Models and ...

Flammable Gas Refined Safety Analysis Tool Software Verification and Validation Report for Resolve Version 2.5

“…Average BD GRE volumes for the six BD positive tanks are reported in Meyer et al (1997). These values were compared with the mean (average) of the spontaneous BD GRE release volumes calculated for 200 trials in Resolve.…”

“…Historical monitoring data or values inferred from monitoring data are available for the BD GRE behavior of some tanks. These data include the following: Model predictions for average BD GRE volume, the average peak hydrogen concentration after a release, and average period between BD GREs were compared against the monitoring data (Meyer et al 1997, Stewart 1998) for double-shell tanks (DSTs) in which BD GRE behavior has historically been observed. In addition, the AT'S evaluation of BD GRE potential-whether BD behavior will or will not occur in a tank-was compared to the list of tanks in which BD GRE behavior has historically been observed.…”

“…References and Inputs: Gas Retention and Release Behavior in Hanford Double-Shell Waste Tanks (Meyer et al 1997). "shmsgred.xls" (Stewart 1998), a spreadsheet containing monitoring data and derivation of peak hydrogen concentration for tanks with observed buoyant displacement GRE behavior.…”

“…These values were removed electronically from the debug output file using the "FilterResolveResults.sh' (McCornak 1999) filter tool. Meyer et al (1997) reports average BD GRE periods as well. These were compared to the spontaneous BD GRE frequencies reported in the GUI calculated statistics.…”

“…Except for the Tank 241-SY-101 analysis, the average of Resolve-calculated BD GRE release volumes for a tank vary from the average of BD GRE volumes inferred from headspace hydrogen measurement histories for the same tank (Meyer et al 1997) by no more than a factor of 2 (Table 4-1 1). This is within the acceptable range for this comparison.…”