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DOE OSTI2019

Analysis of Tank 30H (HTF-30-18-96, -97), Tank 32H (HTF-32-18-98, -99), and Tank 37H (HTF-37-18-100, -101) Samples for Support of the Evaporator Feed Qualification and Corrosion Control Programs for the 3H-Evaporator

SRNL analyzed samples from Tank 30H, Tank 32H, and Tank 37H to support the Evaporator Feed Qualification and Corrosion Control Programs for the 3H-Evaporator system. The six samples from Tanks 30H, 32H, and 37H all contain highly concentrated salt solutions with sodium concentrations ranging from 11.8 M to 15.7 M. The samples from Tank 30H show somewhat higher concentrations of the major cations and anions in the sub-surface sample than the surface sample indicating some stratification within the tank. The two Tank 32H samples show similar concentrations of the major anions and cations between the surface and sub-surface samples. The sub-surface sample from Tank 37H shows higher concentrations for most species than the surface sample indicating some stratification within this tank as well. For all six samples, the sum of the major cations versus the sum of the major anions shows a difference of <10% providing an indication of good data quality. The VDS and surface samples from Tank 30H, Tank 32H, and Tank 37H all show silicon concentrations below 30 mg/L except for the Tank 30H VDS with a concentration of 87 mg/L.

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DOE OSTI2019

Tank 9H Salt Solution Supernatant Characterization in Support of Potential Operating Strategies of Tank 9H Supernatant Through the Tank Closure Cesium Removal System

Savannah River Remediation (SRR) recently initiated an ion exchange process to remove radioactive cesium from dissolved salt solution in Tank 10H, known as Tank Closure Cesium Removal (TCCR). As part of that ongoing campaign, the salt in Tank 9H will be dissolved and transferred to Tank 10H for processing through the TCCR system, and SRR requested the characterization of the dissolved salt solution in Tank 9H prior to the transfer to Tank 10H. On July 18, 2019, Savannah River Remediation Engineering (SRR-E) delivered two variable depth Tank 9H salt solution samples, identified as samples HTF-9-19-74 and HTF-9-19-75 (combined total sample volume of about 400 mL) to the Savannah River National Laboratory (SRNL) for characterization. These two Tank 9H variable depth samples (HTF-9-19-74 and HTF-9-19-75 taken at ~180” and 42”, respectively) were retrieved from Riser 7 after hydro-lancing activities were complete. Approximately 4200 gallons of water were added to the tank during this activity. This report presents the analytical characterization results for the Tank 9H salt solution variable depth samples HTF-9-19-74 and HTF-9-19-75 and contains mainly the filtrate analytical results for anions, elements, mass spectral data, total cesium characterization results and select radionuclide results, along with the X-ray diffraction characterization of the solid fractions from the liquid /solid separation of the variable depth salt solutions. Most of these analyses were performed in duplicate with the percent relative standard deviation (%RSD), a measure of the variability between each duplicate data set expressed as a percentage, used to estimate the analytical result quality for each analyte.

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DOE OSTI2015

Disposition of Hanford Tank Waste sludge from tank 241-AY-102 and the 241-Aa/241-AX farm tanks - 15298

WRPS must retrieve the waste from double-shell tank 241-AY-102 and the single-shell tanks in the 241A and -AX Tank Farms, while finishing the ongoing retrieval of tanks in the 241-C Tank Farm. Given the limited availability of double-shell tank space, the challenge is to identify an optimum combination of double-shell tanks that can safely and efficiently serve as receiver tanks for the combined inventory of sludge wastes from these source tanks. A multiple-criteria, weighted-sum decision-making process, in conjunction with sensitivity analysis and a Pareto evaluation, was used to determine the optimum set of receiver tanks. (authors)

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DOE OSTI2019

Analysis of Tank 30H (HTF-30-19-33, -34), Tank 32H (HTF-32-19-35, -36), and Tank 37H (HTF-37-19-53, -54) Samples for Support of the Evaporator Feed Qualification and Corrosion Control Programs for the 3H-Evaporator

SRNL analyzed samples from Tank 30H, Tank 32H, and Tank 37H to support the Evaporator Feed Qualification and Corrosion Control Programs for the 3H-Evaporator system. The six samples from Tanks 30H, 32H, and 37H all contain highly concentrated salt solutions with sodium concentrations ranging from 13.8 M to 16.9 M. Hydroxide is the dominant anion in all of the samples followed by nitrate and nitrite. The preponderance of the analytical determinations (density, anions, cations) on all three tanks show slightly higher concentrations of solute in the sub-surface sample than in the surface sample, indicating some stratification within the tanks. With the exception of the Tank 30H VDS, all of the samples are somewhat more concentrated compared with the compositions of the previous samples. The sum of the major cations versus the sum of the major anions show a difference of <5% for all of the samples indicating good data quality for the non-radioactive analytes in the table. The silicon concentrations measured in the VDS and surface samples from Tank 30H, Tank 32H, and Tank 37H were all below detection.

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DOE OSTI2019

Analysis of Tank 30H (HTF-30-19-33, -34), Tank 32H (HTF-32-19-35, -36), and Tank 37H (HTF-37- 19-53, -54) Samples for Support of the Evaporator Feed Qualification and Corrosion Control Programs for the 3H-Evaporator

SRNL analyzed samples from Tank 30H, Tank 32H, and Tank 37H to support the Evaporator Feed Qualification and Corrosion Control Programs for the 3H-Evaporator system. The six samples from Tanks 30H, 32H, and 37H all contain highly concentrated salt solutions with sodium concentrations ranging from 13.8 M to 16.9 M. Hydroxide is the dominant anion in all of the samples followed by nitrate and nitrite. The preponderance of the analytical determinations (density, anions, cations) on all three tanks show slightly higher concentrations of solute in the sub-surface sample than in the surface sample, indicating some stratification within the tanks. With the exception of the Tank 30H VDS, all of the samples are somewhat more concentrated compared with the compositions of the previous samples. The sum of the major cations versus the sum of the major anions show a difference of <5% for all of the samples indicating good data quality for the non-radioactive analytes in the table. The silicon concentrations measured in the VDS and surface samples from Tank 30H, Tank 32H, and Tank 37H were all below detection.

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DOE OSTI2026

Analysis of Tank 38H (HTF-38-26-16, -17), Tank 43H (HTF 43-26-18, -19) and Tank 22 (HTF-22-26-20, -21) Samples for Support of the Enrichment Control and Corrosion Control Programs

Savannah River National Laboratory (SRNL) analyzed samples from Tank 38H, Tank 43H and Tank 22H to support the Enrichment Control Program (ECP) and Corrosion Control Program (CCP). The results indicate the concentrations of most soluble species in the Tank 38H surface sample are ~ 76% of the concentrations in the previous Tank 38H surface sample. The current Tank 38H subsurface sample is a clear solution with soluble species that are ~ 70% of the concentrations in the previous Tank 38H subsurface. Significant differences in the concentrations of major components between the current Tank 38H surface and subsurface samples indicate stratification of solution species between these two locations within Tank 38H.

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DOE OSTI2015

Results of Hg Speciation Testing on 2Q15 Tank 50 and Tank 21 TCLP Extraction Fluid Samples and Tank 49 Material

The Savannah River National Laboratory (SRNL) was tasked with preparing and shipping samples for Hg speciation by Eurofins Frontier Global Sciences, Inc. in Seattle, WA on behalf of the Savannah River Remediation (SRR) Mercury Task Team. The sixth shipment of samples was designated to include SRNL Toxicity Characteristic Leaching Procedure (TCLP) extraction fluids from the 2Q15 Tank 50 and Tank 21 saltstone waste forms as well as Tank 49 material (HTF-49-15-45) collected on May 7, 2015. The TCLP extraction fluid samples were collected from duplicate extractions of two crushed saltstone fractions, one designated as “large” and one designated as “normal”. Both fractions of 2Q15 Tank 50 and Tank 21 saltstones (eight samples) were collected with the minimum possible free headspace and refrigerated prior to final dilution. The Tank 49 sample was left in its stainless steel dip bottle until it was opened and an aliquot diluted 1:100 with Eurofins deionized water on May 21, 2015. Following initial dilution in the Shielded Cells, the diluted Tank 49 sample was immediately moved to refrigeration and kept in the dark until prepared for shipment to Eurofins.

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DOE OSTI2018

Analysis of Tank 30H (HTF-30-18-54, -55), Tank 32H (HTF-32-18-56, -57), and Tank 37H (HTF-37-18-58, -59) Samples for Support of the Evaporator Feed Qualification and Corrosion Control Programs for the 3H-Evaporator

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DOE OSTI2018

Heat Pump Water Heater Using Wrapped-Tank Microchannel Condenser Coil for Charge Reduction – FY19 1st Quarter (Regular) Milestone Report: Development of Wrapped-Tank Condenser Model (Round Tube and Microchannel), Coupled with Water Tank Model

We recently grew the DOE/HPDM model library to enhance its heat pump water heater (HPWH) design and simulation capability. The new additions include wrapped-tank round tube coil, microchannel coil and a one-dimensional stratified water tank. A wrapped-tank condenser coil has strong coupling with a stratified water tank, which leads HPWH simulation a transient process. The new one-dimensional stratified water tank model is an improvement to the open-source EnergyPlus water tank model, by introducing a calibration factor to account for bulk mixing effect due to water draws and circulations, etc. The wrapped-tank condenser coil model, using a segment-to-segment modeling approach to simulate round tubes or microchannel ports. The heat exchanger models can accept arbitrary refrigerant types, e.g. HFCs, HFOs, natural refrigerants like CO 2 and propane, etc.

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DOE OSTI2025

Evaluation of Hanford 200 West Area Tank Farms (241-S/241-SX-/241-U tank farms) Physical Properties Data for Use in Development of West Area Tank Treatment (WATT) Processing

With the recent acceptance of West Area Tank Treatment disposition alternative for 200 West Area tanks at the Hanford Site by the State of Washington and the U.S. Department of Energy, a review was initiated to identify the physical properties data available in the literature for the Hanford 241-S, 241-SX, and 241-U tank farms. The literature reviewed indicated that there is a relatively small set of useful data on physical properties of 200 West Area tanks, and the data that do exist are biased around a narrow range of tank samples. Much of the testing between the 1990s and mid-2010s was intended to support either enhanced sludge washing or feed delivery to the Pretreatment Facility at the Hanford Waste Treatment and Immobilization Plant. As such, some physical properties of 200 West Area samples were measured under conditions that are no longer relevant. Because of the distinctly different nature of many past processes at the 200 West Area compared to the 200 East Area, insight from waste testing in the 200 East Area waste should be used with caution, as there may be significantly different qualities in the physical properties data between these two areas (both in situ and as measured in laboratory analyses). Based on this assessment, there is a need to collect additional physical property data to support planning for 200 West Area retrievals.

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DOE OSTI2022

Analysis of Tank 38H (HTF-38-22-91, -92) and Tank 43H (HTF-43-22-93, -94) Samples for Support of the Enrichment Control and Corrosion Control Programs

SRNL analyzed samples from Tank 38H and Tank 43H to support ECP and CCP. The results indicate the concentrations of most soluble species in the Tank 38H surface sample increased slightly from the previous surface sample. The Tank 38H sub-surface sample shows changes in concentration for soluble species in the solution with some increasing and some decreasing. The current Tank 38H sub-surface sample contains more sludge solids than the previous sample based on visual appearance. The small differences in the concentrations of major components between the Tank 38H surface and sub-surface samples indicate only minimal stratification of solution species within the tank. The Tank 43H surface and sub-surface samples are similar in composition to the previous samples. The similar solution compositions measured in the Tank 43H surface and sub-surface samples indicate a minimal stratification within the tank. The total uranium and plutonium in the current Tank 38H surface sample remains similar to the previous analysis. The Tank 38H sub-surface sample shows an increase in uranium and plutonium concentrations compared to the previous sample likely because of an increase in sludge solids in the current sample. The total uranium concentration in the two Tank 43H samples is essentially unchanged from previous sample results. The plutonium concentration in the Tank 43H surface sample is similar to the previous sample results while the plutonium in the Tank 43H sub-surface sample increased relative to the previous analysis. The sum of the major cations versus the sum of the major anions shows a difference of <10% for both samples from Tank 38H and for both samples from Tank 43H providing an indication of good data quality for the non-radioactive analytes in the samples. The silicon concentrations measured in the Tank 38H sub-surface sample increased compared with the previous sample results likely due to the presence of more sludge solids in the current sample. The Tank 38H surface sample silicon concentrations is similar to the previous sample results. The Tank 43H surface and sub-surface sample silicon concentrations both increased compared to the previous sample results. The samples analyzed from Tanks 38H and 43H show silicon concentrations ranging from 61.5 to 97.3 mg/L.

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DOE OSTI2019

Analysis of Tank 38H (HTF-38-19-77, -78) and Tank 43H (HTF-43-19-79, -80) Samples for Support of the Enrichment Control and Corrosion Control Programs

SRNL analyzed samples from Tank 38H and Tank 43H to support ECP and CCP. Overall, the results indicate the concentrations of most species in the Tank 38H surface and sub-surface samples increased significantly from the previous sample results. The Tank 38H sub-surface sample is more concentrated than the surface sample indicating stratification within the tank. Both the Tank 43H surface and sub-surface samples are similar in composition to the previous samples for most species analyzed. The Tank 43H subsurface sample remains slightly more concentrated than the surface sample indicating a small amount of stratification remains in the tank. The total uranium concentrations for the two Tank 38H samples differ significantly due to the presence of sludge solids in the sub-surface sample that markedly increased the uranium concentration. Both the Tank 38H surface and sub-surface samples have higher uranium concentrations than the previous samples from the tank. The weight percent water insoluble solids on the Tank 38H sub-surface sample show the sample contained 0.30 wt% insoluble solids, well below the 1 wt% limit. The total uranium concentrations of the two Tank 43H samples differ by <10% and are similar to the previous sample results. The sum of the major cations versus the sum of the major anions shows a difference of ~1% for the both the Tank 38H and Tank 43H surface samples providing an indication of good data quality for the nonradioactive analytes in the surface samples. The silicon concentrations measured in the Tank 38H surface and sub-surface samples are higher than the previous sample results. Due to the presence of sludge solids, the Tank 38H sub-surface sample show a silicon concentration an order of magnitude higher than the previous result. The Tank 43H surface and sub-surface samples have similar silicon concentrations and are similar to the previous Tank 43H samples. The silicon concentration was below detectable levels in the process blank. The five samples analyzed show silicon concentrations ranging from 88 to 710 mg/L.

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DOE OSTI2023

Analysis of Tank 38h (HTF-38-23-19, -20) and Tank 43H (HTF-43-23-21, -22) Samples for Support of the Enrichment Control and Corrosion Control Programs

SRNL analyzed samples from Tank 38H and Tank 43H to support ECP and CCP. The results indicate the concentrations of most soluble species in the Tank 38H surface sample decreased significantly from the previous surface sample. The Tank 38H sub-surface sample shows changes in concentration for soluble species in the solution with some increasing and some decreasing. The current Thank 38H sub-surface sample contains visible sludge solids similar to the previous sample, i.e., less than 1%, based on visual appearance. The significant differences in the concentrations of major components between the Tank 38H surface and sub-surface samples indicate significant stratification of solution species between these two locations within the tank. Savannah River Mission Completion personnel indicate that ~ 150,000 gallons of Tank 22 supernate were received in Tank 38H since its last analysis during which time the 2H evaporator was not operated, so the observed stratification is expected. The Tank 43H surface and sub-surface samples are similar in composition to the previous samples. The similar solution compositions measured in the Tank 43H surface and sub-surface samples indicate a minimal stratification within the tank. The total uranium and plutonium in the current Tank 38H surface sample remains similar to the previous analysis. The Tank 38H sub-surface sample shows an increase in uranium and plutonium concentrations compared to the previous sample likely because of an increase in sludge solids in the current sample. The total uranium concentration in the Tank 43H surface sample is similar to the previous sample results while the plutonium in the Tank 43H sub-surface sample increased relative to the previous analysis. The sum of the major cations versus the sum of the major anions shows a difference of <10% for both samples from Tank 38H sub-surface sample (174 mg/L) increased compared with the previous sample. The Tank 38H surface sample silicon concentrations (27.5 mg/L) is one-half of the previous sample results. The Tank 43H surface sample silicon concentrations compared to the previous sample results indicate Si in the concentration range of 60 to 83 mg/L. Thus, these current samples analyzed from Tanks 38H and 43H show overall silicon concentrations ranging from 27.5 to 174 mg/L.

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DOE OSTI2016

SNL API-653 In-Service Tank Inspection and Evaluation Tank ID: 981-A2-T0 (West)

An API Standard 653 In-Service inspection was completed on Tank 981-A2-T0 (West) located at the Sandia National Laboratories TAIV tank farm in Albuquerque, NM on September 22, 2015. The inspection was completed to collect data to evaluate the mechanical integrity and fitness for continued service of the tank. No indication or records of any previous inspection were identified for this tank. The inspection and engineering evaluation were completed using API-653, 5 th Edition and conservative engineering practices. The tank was not removed from service, so an internal inspection could not be completed. The tank was also fully insulated. The insulation was removed in specified areas of the tank shell and tank chime to accommodate an acoustic emission scan of the tank and an ultrasonic thickness evaluation of portions of the tank. The acoustic emission scan resulted in a grade of B / I - II indicating an overall TANKPAC grade B and composite grade II indicating minor active damage with highly concentrated sources related to corrosion found in the southeast and west side section of the tank. Eight Potential Localized Damage sources were found mainly in the west side (re-test in 2 years). The tank chime could not be inspected due to the configuration of the insulation welded angle support. An ultrasonic guided bulk wave inspection was completed on the tank shell to assess the lower shell section. At the time of the inspection the limited data collected showed minimal material loss from the shell at the thickness monitoring locations, however, visual inspection and pit depth gauge measurements showed > 3/16” inch pitting and significant general external surface corrosion on the shell at the shell to floor joint. This corrosion is caused by the insulation sheeting support welded angle iron trapping moisture and dirt against the tank shell. This tank should be removed from service, internally inspected, and repaired. Ultrasonic thickness measurement locations were established on this tank and the data is included in this report. The limited data collected indicated minimal material loss at these locations, with the only noted corrosion occurring on the tank shell to floor joint as noted above. An API-653 Annex B Evaluation of Tank Bottom Settlement was completed and the results are included in this report. No significant settlement issues were identified.

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DOE OSTI2025

Analysis of Tank 38H (HTF-38-25-36, -32) and Tank 43H (HTF-43-25-33, -35) Samples for Support of the Enrichment Control and Corrosion Control Programs

Savannah River National Laboratory (SRNL) analyzed samples from Tank 38H and Tank 43H to support the Enrichment Control Program (ECP) and Corrosion Control Program (CCP). The results indicate the concentrations of most soluble species in the Tank 38H surface sample are similar to the previous Tank 38H surface sample. The current Tank 38H subsurface sample shows similar Na, free hydroxide, and anions in comparison to the previous subsurface sample. The current Tank 38H subsurface sample appears brown in color. Measurement of the wt.% insoluble solids in the Tank 38H subsurface sample and associated uncertainty analysis indicates that the calculated average wt.% insoluble solids is 5.5 ± 3.6 wt.%. Significant differences in the concentrations of major components between the Tank 38H surface and subsurface samples indicate stratification of solution species between these two locations within the Tank 38H. The current Tank 43H surface sample is ~ 10% diluted versus the previous Tank 43H surface sample and the Tank 43H subsurface sample is similar in composition to the previous Tank 43H subsurface sample. Information provided by SRMC on tank additions since the last ECP sampling indicates that a total of about 4,062 gallons of water was added to Tank 43H. This addition could account for the observed relatively small dilution of ~ 10% in the Tank 43H surface sample. Similar solution compositions measured in the current Tank 43H surface and subsurface samples indicate a minimal stratification within the tank.

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DOE OSTI2020

Characterization of Tank 11H samples from tank closure cesium removal (TCCR) Batch 3 - intermediate and final samples

Savannah River Remediation (SRR) is currently operating the Tank Closure Cesium Removal (TCCR) process to remove 137 Cs from tank waste supernate using an ion exchange process. The TCCR unit processes dissolved salt from Tank 10H through a series of ion exchange columns containing crystalline silicotitanate (CST) and the effluent is then discharged to Tank 11H. Four interim samples pulled from Tank 11H during and just after the completion of processing of Batch 3 through the TCCR process have been analyzed for 137 Cs activity and density. The 137 Cs activity was found to decrease with each subsequent sample, which is consistent with the addition of decontaminated solution to Tank 11H. When compared to the expected composition from mixing the Tank 10H Batch 3 feed with the material already present in Tank 11H, the bulk chemical composition was as expected. A corrosion control sample collected from Tank 11H in June 2020 showed changes in the chemical composition and 137 Cs activity when compared to the composition measured at the end of Batch 2 processing. As there were no additions made to the tank during this period, these changes were attributed to leaching of the solids present in Tank 11H. Revision 1 of this report contains additional analyses of the fourth interim sample including inductively coupled plasma – mass spectrometry (ICP-MS) results and activities of other radionuclides. These results are consistent with the previously reported results, showing leaching from the Tank 11H heel. Notably, the 90 Sr activity was about 2.7x higher than calculated from a mixture of the original Tank 11H supernate and the Tank 10H supernate as treated by TCCR, suggesting additional leaching of Sr from the Tank 11H heel solids. In addition, Revision 1 includes analysis results for the Batch 3 Post-Production surface and variable depth samples collected in October of 2020. The Post-Production surface sample was similar in composition to the fourth interim surface sample, except for the increased Cs-137 and oxalate concentrations that were presumably associated with leaching of the Tank 11H heel solids.

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DOE OSTI2022

Characterization of Tank 11H Samples from Tank Closure Cesium Removal 1A (TCCR 1A) Batch 1

Savannah River Mission Completion (SRMC) is currently operating the Tank Closure Cesium Removal 1A (TCCR 1A) process to remove 137 Cs from tank waste supernate using an ion exchange process. The TCCR 1A unit processes dissolved salt fed from Tank 10H through a series of ion exchange columns containing crystalline silicotitanate (CST, IONSIV TM R9120-B, 30x60) and the effluent is then discharged to Tank 11H. In support of the TCCR 1A program, SRNL analyzed samples taken from Tank 11H (without tank mixing) before, during, and at the completion of TCCR 1A Batch 1 processing. Tank 11H serves as the receipt tank for the filtered and cesium removed product from the TCCR 1A system. Processing of Batch 1 commenced on January 13, 2022 and completed on February 17, 2022, after processing approximately 70,100 gallons. A pre-production sample was collected from the heel remaining in Tank 11H just before Batch 1 processing began. In addition, five interim surface samples were collected from Tank 11H during processing, and both a surface and a variable depth sample (VDS, ~7” from tank bottom) were collected just after processing completed. Analysis of all samples included density and gamma spectroscopy, in addition to a more comprehensive suite of analytes for the pre- and post-production samples. The density of the pre-production sample was the highest of all samples measured and was then observed to decrease for the first two interim samples, followed by becoming fairly consistent for the remainder of the samples (~1.3 g/mL). The density of 1.3 g/mL is similar to the density measured for one of the three Tank 10H qualification samples (HTF-10-21-126). The 137 Cs activity was found to decrease as additional decontaminated effluent from the TCCR columns was added to Tank 11H during processing; however, an increase in activity was observed during periods of no processing which can be attributed to leaching of 137 Cs from the known solids in Tank 11H. The Cs isotope concentrations in the Tank 11H postproduction surface sample were determined to be 99.7-99.8% lower than the concentrations measured in the Tank 10H feed as measured by mass spectrometry.

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DOE OSTI2020

Modeling Efforts to Gain Insight into Historical Leak Events from the Single-Shell Tank A-105 in the Hanford 241-A Tank Farm - 20113

The 241-A Tank Farm is a single-shell tank (SST) farm constructed to store process waste from Hanford nuclear operations. Millions of gallons of nuclear waste were stored in the 241-A Tank Farm SSTs and some of the SSTs leaked in the past. In addition, spills and pipeline leaks during transfers and storage and intentional discharges to cribs and trenches resulted in releasing waste to the ground. Tank liner leaks are referred to as 'leaks' and all other discharges to the soil are referred to as 'releases.' Liquid waste that could be removed by pumping has been removed from all of the SSTs to reduce the potential for future leaks. The most significant historical leak event in 241-A Tank Farm occurred in 1965 when tank A-105 experienced a pressurized steam event. This event resulted in damage to the inner steel liner flooring of A-105, which was separated from the sidewalls over part of its circumference and buckled up to 2.5 m, vertically. During this event up to 7,570 L of contaminated liquid may have leaked to the adjacent soil. This leak occurred under extreme temperature and pressure conditions. Modeling efforts to better understand the nature and extent of historical leaks from subsurface SSTs that were used to store highly radioactive, self-boiling liquid wastes at 241-A Tank Farm have recently been undertaken. These efforts have compiled the available historical information to support a preliminary non-isothermal, multiphase flow and chemical transport modeling effort to re-create the conditions under which the leaks occurred and to formulate a conceptual model as to the extent and distribution of leaked radioactive contaminants in the adjacent soil material. The focus of this work was on developing an understanding of the key features, processes and bounding conditions related to tank A-105 leak events that occurred in the 1960's. The activities include estimation of leak composition, non-isothermal multiphase flow and transport modeling, and geochemical modeling. The STOMP{sup C} Water-Air-Energy modeling code was utilized to implement the three-dimensional representation of the subsurface tank and the surrounding flow field. Once constructed, the model was used to evaluate the conceptual understanding of leaks originating from different parts of the tank under the elevated temperature boundary conditions that were imposed by surrounding tanks at the time of the historical leaks. The chemical evolution of the liquid waste was also evaluated as it leaked from the tank under transient pressure and temperature gradients. The results of the preliminary evaluation suggested the presence of a heat-pipe effect beneath tank A-105 in which water vapor at an elevated temperature is driven away from the base of the tank to a position where water vapor cools, condenses and is then drawn back toward the tank by the strong capillary attraction of the dry soil. A non-sorbing contaminant (Tc-99) was introduced into this flow field to better understand the potential distribution patterns of leaked contaminants that may have occurred during the historical leak events. (authors)

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