Performance Properties of Saltstone Produced Using SWPF Stimulants

The overwhelming majority of waste to be immobilized at the Saltstone Production Facility will come from the waste stream exiting the Salt Waste Processing Facility (SWPF). These SWPF batches are salt solutions that result from pretreatment of the High Level Waste (HLW) supernate by an Actinide Removal Process followed by Caustic Side Solvent Extraction. The concentration of aluminate within these streams will vary and be determined by (1) the concentration in the incoming salt waste stream, (2) the degree of aluminum leaching from the HLW, (3) the method for introducing the aluminate into the waste stream (continuous or batch) and (4) and any operational or regulatory limitations. The overall Performance Assessment outcome for the Saltstone Disposal Facility will depend significantly on the performance properties of the SWPF Saltstone grouts. This report identifies and quantifies, when possible, those factors that drive the performance properties of the projected SWPF grouts. Previous work has identified aluminate concentration in the salt waste stream as a key factor in determining performance. Consequently, significant variation in the aluminate concentration to a maximum level of 0.65 M was investigated in this report. The SWPF baseline grout is a mix with a 0.60 water to cementitious ratio and a premix composition of 45 wt % slag, 45 wt % fly ash and 10 wt % portland cement. The key factors that drive performance of the SWPF mixes were determined to be (1) the time/temperature profile for curing, (2) water to cementitious materials ratio, (3) aluminate concentration in the waste stream, and (4) wt % slag in the premix. An increase in the curing temperature for mixes with 45 wt % slag resulted in a 2.5 times decrease in Young's modulus. The reduction of Young's modulus measured at 60 C versus 22 C was mitigated by an increase in the aluminate concentration but was still significant. For mixes containing 60 wt % slag, the reduction in Young's modulus between these two curing temperatures was significantly lessened. The importance of curing conditions can not be overemphasized. The gain realized in performance by, e.g., a higher level of aluminate or wt % slag or a reduction in w/cm ratio, can be offset by the effects of a higher curing temperature. In fact, the final performance properties of a mix cured at 60 C can be lower than the initial values before any of the performance enhancing changes are introduced. Control of the time/temperature curing profile can be managed by pour schedules and other temperature control measures. The reduction in performance at higher curing temperatures is consistent with results obtained in a separate study. Although preliminary, results from this task on the measurement of hydraulic conductivity at MACTEC showed that curing of a Saltstone mix at 60 C increased the hydraulic conductivity by several orders of magnitude. The permeability data are based on only one mix but, were consistent with a measured reduction in Young's modulus for these same samples. Therefore, it is recommended that impact of curing temperature on performance properties be further investigated. An increase in dynamic Young's modulus (indicator of performance) is observed as the water to cementitious materials (w/cm) ratio decreases. The w/cm ratio is a process parameter which can be adjusted to improve performance as long as the processing properties of the grout are still within an operational window that will lead to successful placement. The same conclusions apply to wt % slag in the premix. That is, an increase in the wt % slag at the expense of fly ash in the premix increases Young's modulus and performance. An increase in wt % slag (as with a decrease in w/cm ratio) increases viscosity and yield stress and a final mix design must be balanced such that acceptable processing properties are obtained. The performance properties of SWPF mixes show a non-linear dependence on aluminate concentration. As the aluminate concentration is increased from 0.1 M to 0.25 M, the Young's modulus and compressive strength increase and the porosity is reduced. Consistent with this improvement in performance is an increase in the heat of hydration, reflective of an increase in the degree of hydration. Higher degrees of hydration in mixes generally lead to better performance. In the region of 0.25 to 0.45 M aluminate, very little additional change is observed in any of the properties. A further increase in the aluminate concentration from 0.45 M to 0.65 M leads to a slight reduction in Young's modulus. It was observed however, that the values of Young's modulus for samples cured at 22 C decreased after approximately 50 days. This was the first time a reduction in Young's modulus was observed as a function of time and is most likely correlated with the high levels of aluminate present in these mixes. This reduction can be accounted for by cracking of the Saltstone samples with time

A Real-Time Ethernet Network at Home

This paper shows the current state of our research into a home network which provides both real-time and non-real-time capabilities for one coherent, distributed architecture. It is based on a new type of real-time token protocol that uses scheduling to achieve optimal token-routing in the network. Depending on the scheduling algorithm, bandwidth utilisations of 100% are possible. Token management, to prevent token-loss or multiple tokens, is essential to support a dynamic, plug-and-play configuration. Our network will support inexpensive, small appliances as well as more expensive, large appliances. Small appliances, like sensors, would contain low-cost, embedded processors with limited computing power, which can handle lightweight network protocols. All other operations can be delegated to other appliances that have sufficient resources. This provides a basis for transparency, as it separates controlling and controlled object

HEAT OF HYDRATION OF SALTSTONE MIXES-MEASUREMENT BY ISOTHERMAL CALORIMETRY

This report provides initial results on the measurement of heat of hydration of Saltstone mixes using isothermal calorimetry. The results were obtained using a recently purchased TAM Air Model 3116 Isothermal Conduction Calorimeter. Heat of hydration is an important property of Saltstone mixes. Greater amounts of heat will increase the temperature of the curing mix in the vaults and limit the processing rate. The heat of hydration also reflects the extent of the hydraulic reactions that turn the fluid mixture into a ''stone like'' solid and consequently impacts performance properties such as permeability. Determining which factors control these reactions, as monitored by the heat of hydration, is an important goal of the variability study. Experiments with mixes of portland cement in water demonstrated that the heats measured by this technique over a seven day period match very well with the literature values of (1) seven day heats of hydration using the standard test method for heat of hydration of hydraulic cement, ASTM C 186-05 and (2) heats of hydration measured using isothermal calorimetry. The heats of hydration of portland cement or blast furnace slag in a Modular Caustic Side Solvent Extraction Unit (MCU) simulant revealed that if the cure temperature is maintained at 25 C, the amount of heat released over a seven day period is roughly 62% less than the heat released by portland cement in water. Furthermore, both the blast furnace slag and the portland cement were found to be equivalent in heat production over the seven day period in MCU. This equivalency is due to the activation of the slag by the greater than 1 Molar free hydroxide ion concentration in the simulant. Results using premix (a blend of 10% cement, 45% blast furnace slag, and 45% fly ash) in MCU, Deliquification, Dissolution and Adjustment (DDA) and Salt Waste Processing Facility (SWPF) simulants reveal that the fly ash had not significantly reacted (undergone hydration reactions) after seven days (most likely less than 5%). There were clear differences in the amount of heat released and the peak times of heat release for the three different simulants. It turns out that SWPF simulant mixes give off greater heat than does MCU and DDA simulant mixes. The temperature dependence of the heat of hydration was measured by carrying out these measurements at 25, 40 and 55 C. In general, the peak times shifted to shorter times as the isothermal temperature increased and the amount of heat released was independent of temperature for DDA and MCU but slightly higher at higher temperatures for SWPF. The goal of this study is to apply this technique to the measurement of the heat of hydration of mixes that will be made as part of the variability study. It is important to understand which variables will impact (and to what extent) the amount of heat generated and the peak times for the heat release. Those variables that can be controlled can then be tuned to adjust the heat of hydration as long as the other properties are still acceptable. The first application of heat of hydration measurements to the variability study was completed and the results presented in this report. These measurements were made using Phase VI mixes (SWPF simulants) following a statistical design that included variation in the compositional and operational variables. Variation in both the amount of heat released and the peak times for the heat release were observed. The measured ranges were 23 Joules per gram of premix for the heat release and 23 hours for the peak time of heat release at 25 C. Linear models with high R{sup 2} values and no statistical evidence for lack of fit were developed that relate the amount of heat release and the peak time for heat release for the Phase VI mixes to certain variables. The amount of heat released was a function of the aluminate and portland cement concentrations as well as the temperature of mixing. The peak time for heat release was a function of aluminate, portland cement and total nitrate plus nitrite concentrations. A comparison was made of the measured values of heat release by isothermal calorimetry to a previous study of the measurement of the heat of hydration using adiabatic calorimetry by Steimke and Fowler. After 80 hours of reaction time, the two techniques provided heat release results that were roughly in the same range. However, additional experiments at higher isothermal temperatures will be required to see how well the two measurements agree for longer times. This is due to the higher temperatures that are experienced in adiabatic calorimetry ({approx}105 C)

PERMEABILITY OF SALTSTONE MEASUREMENT BY BEAM BENDING

One of the goals of the Saltstone variability study is to identify (and, quantify the impact of) the operational and compositional variables that control or influence the important processing and performance properties of Saltstone mixes. A performance property for Saltstone mixes that is important but not routinely measured is the liquid permeability or saturated hydraulic conductivity of the cured Saltstone mix. The value for the saturated hydraulic conductivity is an input into the Performance Assessment for the SRS Z-Area vaults. Therefore, it is important to have a method available that allows for an accurate and reproducible measurement of permeability quickly and inexpensively. One such method that could potentially meet these requirements for the measurement of saturated hydraulic conductivity is the technique of beam bending, developed by Professor George Scherer at Princeton University. In order to determine the feasibility of this technique for Saltstone mixes, a summer student, David Feliciano, was hired to work at Princeton under the direction of George Scherer. This report details the results of this study which demonstrated the feasibility and applicability of the beam bending method to measurement of permeability of Saltstone samples. This research effort used samples made at Princeton from a Modular Caustic side solvent extraction Unit based simulant (MCU) and premix at a water to premix ratio of 0.60. The saturated hydraulic conductivities for these mixes were measured by the beam bending technique and the values determined were of the order of 1.4 to 3.4 x 10{sup -9} cm/sec. These values of hydraulic conductivity are consistent with independently measured values of this property on similar MCU based mixes by Dixon and Phifer. These values are also consistent with the hydraulic conductivity of a generic Saltstone mix measured by Langton in 1985. The high water to premix ratio used for Saltstone along with the relatively low degree of hydration for MCU based mixes leads to high total and capillary porosities. These two conditions generally lead to higher permeabilities as has been well documented in the literature for typical cementitious pastes in water. Therefore, it is not unexpected that the hydraulic conductivities of these Saltstone mixes are relatively high

The physical properties and chemical composition of the gas within the free volume of canistered waste forms

The DWPF must meet Waste Acceptance Preliminary Specifications (WAPS) for acceptance of the DWPF canistered waste forms. A number of these specifications deal with the exclusion of non-wasteglass (or foreign) materials within the canistered waste forms. Those material which are specifically excluded include the following: Free Liquids, Free Gases, other than cover or radiogenic gases, Explosives, Pyrophorics and Combustibles, and Organics. This report documents the results obtained by carrying out an assigned task as described in three task plans. The task plans cover the determination of pressure, gas composition and relative humidity of SRL canistered waste forms; and organic and inorganic analysis of volatilized and condensed species within SRL canistered waste forms. These results provide evidence to demonstrate compliance with these specifications and will be included in the Waste Form Qualification Report (WQR). In all, four canistered waste forms, produced during the Scale Glass Melter (SGM) campaigns, were examined. The internal gas pressure, dewpoint temperature and gas composition were determined for each canistered waste form. The experience gained in these experiments will be used to generate procedures for obtaining the same information on canistered waste forms produced during the Integrated Cold Runs (ICR). 10 refs., 2 figs., 1 tab

Dew point, internal gas pressure, and chemical composition of the gas within the free volume of DWPF canistered waste forms

The Defense Waste Processing Facility (DWPF) produced 55 canistered waste forms containing simulated waste glass during the four Waste Qualification campaigns of the DWPF Startup Test Program. Testing of the gas within the free volume of these canisters for dew point, internal gas pressure, and chemical composition was performed as part of a continuing effort to demonstrate compliance with the Waste Acceptance Product Specifications. Results are presented for six glass-filled canisters. The dew points within the canisters met the acceptance criterion of < 20{degrees}C for all six canisters. Factors influencing the magnitude of the dew point are presented. The chemical composition of the free volume gas was indistinguishable from air for all six canisters. Hence, no foreign materials were present in the gas phase of these canisters. The internal gas pressures within the sealed canisters were < 1 atm at 25{degrees}C for all six canisters which readily met the acceptance criterion of an internal gas pressure of less than 1.5 atm at 25{degrees}C. These results provided the evidence required to demonstrate compliance with the Waste Acceptance Product Specifications

IL-22–producing neutrophils contribute to antimicrobial defense and restitution of colonic epithelial integrity during colitis

IL-22 plays an important role in mucosal epithelial cell homeostasis. Using a dextran sodium sulfate-induced mouse model of acute colitis, we observed an IL-23–dependent up-regulation of IL-22 in the middle and distal colon at the onset of epithelial cell damage. This heightened IL-22 correlated with an influx of innate immune cells, suggesting an important role in colonic epithelial protection. Freshly isolated colon-infiltrating neutrophils produced IL-22 contingent upon IL-23 signaling, and IL-22 production was augmented by TNF-α. Importantly, the depletion of neutrophils resulted in diminished IL-22 levels in the colon, and the transfer of IL-22–competent neutrophils to Il22a-deficient mice protected the colonic epithelium from dextran sodium sulfate-induced damage. In addition, IL-22–producing neutrophils targeted colonic epithelial cells to up-regulate the antimicrobial peptides, RegIIIβ and S100A8. This study establishes a role for neutrophils in providing IL-22–dependent mucosal epithelial support that contributes to the resolution of colitis

IMPACT OF ALUMINATE IONS ON THE PROPERTIES OF SALTSTONE GROUT MIXES

It is important to identify and control the operational and compositional variables that impact the important processing and performance properties of Saltstone grout mixes. The grout that is produced at the Saltstone Production Facility (SPF) is referred to as Saltstone and is a waste form that immobilizes low concentrations of radionuclides as well as certain toxic metals. The Saltstone will be disposed of in vaults at Savannah River Site (SRS). An effort referred to as the Saltstone Variability Study has been initiated to achieve this goal. The protocols developed in this variability study are also ideally suited as a tool to assess the impact of proposed changes to the processing flow sheet for Liquid Waste Operations at SRS. One such proposal that is currently under consideration is to introduce a leaching step in the treatment of the High Level Waste (HLW) sludge to remove aluminum prior to vitrification at the Defense Waste Processing Facility (DWPF). This leachate would significantly increase the soluble aluminate concentration in the salt feed that will be processed at the SPF. Consequently, an initial study of the impact of increased aluminate concentration on the Saltstone grout properties was performed. Prior work by Lukens (1) showed that aluminate in the salt solutions increases the amount of heat generation

IMPACT OF INCREASED ALUMINATE CONCENTRATIONS ON PROPERTIES OF SALTSTONE MIXES

One of the goals of the Saltstone variability study is to identify the operational and compositional variables that control or influence the important processing and performance properties of Saltstone mixes. The protocols developed in this variability study are ideally suited as a tool to assess the impact of proposed changes to the processing flow sheet for Liquid Waste Operations (LWO). One such proposal that is currently under consideration is to introduce a leaching step in the treatment of the High Level Waste (HLW) sludge to remove aluminum prior to vitrification at the Defense Waste Processing Facility (DWPF). This leachate would significantly increase the soluble aluminate concentrations as well as the free hydroxide ion concentration in the salt feed that will be processed at the Saltstone Processing Facility (SPF). Consequently, an initial study of the impact of increased aluminate concentration on the Saltstone grout properties was performed. The projected compositions and ranges of the aluminate rich salt stream (which includes the blending strategy) are not yet available and consequently, in this initial report, two separate salt stream compositions were investigated. The first stream starts with the previously projected baseline composition of the salt solution that will be fed to SPF from the Salt Waste Processing Facility (SWPF). The second stream is the solution that results from washing of the current Tank 51 sludge and subsequent transfer of the salt solution to Tank 11. The SWPF simulant has higher nitrate and lower free hydroxide than the Tank 11 simulant. In both of these cases, the aluminate was varied up to a maximum of 0.40 to 0.45M aluminate in order to evaluate the impact of increasing aluminate ion concentration on the grout properties. In general, the fresh grout properties of mixes made with SWPF and Tank 11 simulants were relatively insensitive to an increase in aluminate concentration in the salt solutions. However, the overall trends observed as the aluminate concentration increased in the salt solution were decreased Bingham Plastic yield stress and plastic viscosity, greater flowability of the grout, and reduced gel times and bleed volume for SWPF based mixes. On the other hand, the set times increased significantly with increasing aluminate concentration in the salt solutions. For the SWPF mixes, the set time increased from 1 to 4 days and for the Tank 11 mixes, the set time increased from 1 to 2 days. Heat of hydration measurements were consistent with the increased set times with extended induction periods (2 to 4 days) as aluminate concentration increased in the salt solution. This extended induction period of heat evolution observed with increasing aluminate concentrations must be addressed for Saltstone operations to avoid exceeding temperature limits. It is anticipated that the induction period will be temperature dependent and should be measured for future projections and included in the thermal modeling. The overall heat generation was greater in the mixes containing higher concentrations of aluminate. In fact, for the total heat release values calculated using curve fitting for longer times, the amount of heat was increased by 33% for SWPF based solutions and by 46% for Tank 11 based solutions. The larger amount of heat from mixes containing higher aluminate concentration must be accounted for in the modeling effort which determines the pour schedule for Saltstone. The increased induction periods were shown to be associated with hydration reactions of the blast furnace slag. The rate of heat generation with high aluminate solutions and Portland cement were only accelerated whereas high aluminate mixes containing blast furnace slag only showed the characteristic increase in induction time that was observed with mixes prepared using the premix blend of cementitious materials. It was shown that fly ash does not react significantly during the first seven days of curing but then undergoes an accelerated burst for 15 days before beginning to level off. The total amount of heat generated from a fly ash only mix with SWPF solution containing aluminate at 0.33 M is approximately 100 J/g vs. 87 J/g for SWPF with 0.11 M aluminate. Finally, the heat of hydration measurements revealed that the ternary system of cementitious materials (premix) leads to interactions between the hydration reactions of these three components that actually reduce the overall heat generation compared to the summation of the heats of hydration for mixes made only from portland cement, blast furnace slag or fly ash

Vitrification of cesium-loaded crystalline silicotitanate (CST) in the shielded cells melter

Through the Tanks Focus Area, the Savannah River Technology Center (SRTC) and the Oak Ridge National Laboratory participated in a joint project in which supernate waste from the Melton Valley Storage Tanks at Oak Ridge was treated by passage through a crystalline silicotitanate (CST) ion exchange column. CST was designed to sorb Cs- 137, Sr-90 and several other radionuclides from highly alkaline solutions containing large quantities of sodium.2 After demonstrating the effectiveness of CST as an ion exchange medium, ORNL shipped some of the loaded sorbent to SRTC where it was mixed with glass formers and processed in a joule-heated melter within the SRTC Shielded Cells. This report details the results of the melter run, along with the preparations that were required to complete the campaign