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DOE OSTI2022

Summary of Results from November 2021 Qualification Samples for Tank Closure Cesium Removal 1A (TCCR 1A)

Savannah River Remediation (SRR) 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. As part of that process, Savannah River National Laboratory (SRNL) receives and analyzes samples in support of the qualification of each batch to be processed. SRNL recently received supernate samples retrieved from Tank 10H as well as in-tank batch contact samples for characterization in support of qualifying Batch 1 for processing through the TCCR 1A unit.

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DOE OSTI2020

DECOVALEX-2019 (Task B Final Report)

The DECOVALEX Project is an on-going international research collaboration, established in 1992, to advance the understanding and modeling of coupled Thermal (T), Hydrological (H), Mechanical (M) and Chemical (C) processes in geological in geological systems. DECOVALEX was initially motivated by the recognition that prediction of these coupled effects is an essential part of the performance and safety assessment of geologic disposal systems for radioactive waste and spent nuclear fuel. This document is the final report of Task B which was proposed and coordinated by the Swiss Federal Nuclear Safety Inspectorate (ENSI) and Lawrence Berkeley National Laboratory (LBNL), presenting the technical definitions of the problems studied, approaches applied, achievements made and outstanding issues for future research. Task B focused mainly on modelling of fault activation experiments (FS experiment) recently performed at the Mont Terri underground research laboratory, Switzerland. The FS experiment explores the coupling between fault reactivation in a clay host rock and the potential-enhanced fluid displacement through a previously low-permeability formation. Based on this experiment, the DECOVALEX-2019 Task B addresses how the change in permeability induced by the fault activation and the resulting fluid flow within the fault can be simulated including the dependence on its mechanical behavior. This will support the understanding of the processes during fault activation itself and it can help to determine consequences for contaminant transport due to potentially created permeable flow paths in otherwise low permeability argillaceous rocks.

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DOE OSTI2013

Opportunities and challenges for structural health monitoring of radioactive waste systems and structures

Radioactive waste systems and structures (RWSS) are safety-critical facilities in need of monitoring over prolonged periods of time. Structural health monitoring (SHM) is an emerging technology that aims at monitoring the state of a structure through the use of networks of permanently mounted sensors. SHM technologies have been developed primarily within the aerospace and civil engineering communities. This paper addresses the issue of transitioning the SHM concept to the monitoring of RWSS and evaluates the opportunities and challenges associated with this process. Guided wave SHM technologies utilizing structurally-mounted piezoelectric wafer active sensors (PWAS) have a wide range of applications based on both propagating-wave and standing-wave methodologies. Hence, opportunities exist for transitioning these SHM technologies into RWSS monitoring. However, there exist certain special operational conditions specific to RWSS such as: radiation field, caustic environments, marine environments, and chemical, mechanical and thermal stressors. In order to address the high discharge of used nuclear fuel (UNF) and the limited space in the storage pools the U.S. the Department of Energy (DOE) has adopted a 'Strategy for the Management and Disposal of Used Nuclear Fuel and High-Level Radioactive Waste' (January 2013). This strategy endorses the key principles that underpin the Blue Ribbon Commission's on America's Nuclear Future recommendations to develop a sustainable program for deploying an integrated system capable of transporting, storing, and disposing of UNF and high-level radioactive waste from civilian nuclear power generation, defense, national security, and other activities. This will require research to develop monitoring, diagnosis, and prognosis tools that can aid to establish a strong technical basis for extended storage and transportation of UNF. Monitoring of such structures is critical for assuring the safety and security of the nation's spent nuclear fuel until a national policy for closure of the nuclear fuel cycle is defined and implemented. In addition, such tools can provide invaluable and timely information for verification of the predicted mechanical performance of RWSS (e.g. concrete or steel barriers) during off-normal occurrence and accident events such as the tsunami and earthquake event that affected Fukushima Daiichi nuclear power plant. The ability to verify the conditions, health, and degradation behavior of RWSS over time by applying nondestructive testing (NDT) as well as development of nondestructive evaluation (NDE) tools for new degradation processes will become challenging. The paper discusses some of the challenges associated to verification and diagnosis for RWSS and identifies SHM technologies which are more readily available for transitioning into RWSS applications. Fundamental research objectives that should be considered for the transition of SHM technologies (e.g., radiation hardened piezoelectric materials) for RWSS applications are discussed. The paper ends with summary, conclusions, and suggestions for further work. (authors)

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DOE OSTI2015

Lessons learned in the hot cell at the transuranic waste processing center - 15336

The hot cell at the Transuranic Waste Processing Center (TWPC) has been in operation for seven years. Its mission is to empty, process, and repackage the contents Remote Handled (RH) concrete waste casks. The sequence of operation for processing the RH casks includes using a remotely operated manipulator (manipulator) to remove the cask contents and deliver them to a work table where operators process the waste into RH-TRU, CH-TRU, LLW drums using Master Slave Manipulators (MSMs). The manipulator is the only piece of equipment that can remove material from the cask and represents a single point failure that can shut down hot cell processing should it fail. During the first six years of operation the project processing goals were constantly in jeopardy due to the high frequency and extent of manipulator failures that forced unplanned down time in the hot cell to facilitate repairs. In 2013 a hot cell maintenance outage was planned and executed to improve the operability and reduce the equipment failure rate. A new remotely operated manipulator, purchased as a spare before the outage, was installed in the hot cell during the outage. Prior to installing the manipulator into the hot cell several major and minor modifications were made to the manipulator to incorporate improvements manipulator reliability and maintainability based upon operating and maintenance lessons learned from the previous years of operation. Additionally a maintenance glovebox was added to the hot cell for servicing the removable manipulator components. (authors)

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DOE OSTI2013

Precious metals and rare earth elements in municipal solid waste – Sources and fate in a Swiss incineration plant

Highlights: ► We carefully addressed all the very valuable comments and suggestions of the reviewers. ► We also have shortened the size of the paper and tried simplify it substantially, as requested by the reviewers (introduction 25% reduced!). ► We have decided to take the chance and have replaced the data for the “additional” elements (Cu, Cd, Zn, Pb, Sn, Cr, Ni, Fe, Al) of the earlier MFA (Morf, 2011) with data that belong to the samples of this study. ► We are convinced that with the revision the paper has significantly improved in quality and attractiveness. - Abstract: In Switzerland many kinds of waste, e.g. paper, metals, electrical and electronic equipment are separately collected and recycled to a large extent. The residual amount of municipal solid waste (MSW) has to be thermally treated before final disposal. Efforts to recover valuable metals from incineration residues have recently increased. However, the resource potential of critical elements in the waste input (sources) and their partitioning into recyclable fractions and residues (fate) is unknown. Therefore, a substance flow analysis (SFA) for 31 elements including precious metals (Au, Ag), platinum metal group elements (Pt, Rh) and rare earth elements (La, Ce, etc.) has been conducted in a solid waste incinerator (SWI) with a state-of-the-art bottom ash treatment according to the Thermo-Re® concept. The SFA allowed the determination of the element partitioning in the SWI, as well as the elemental composition of the MSW by indirect analysis. The results show that the waste-input contains substantial quantities of precious metals, such as 0.4 ± 0.2 mg/kg Au and 5.3 ± 0.7 mg/kg Ag. Many of the valuable substances, such as Au and Ag are enriched in specific outputs (e.g. non-ferrous metal fractions) and are therefore recoverable. As the precious metal content in MSW is expected to rise due to its increasing application in complex consumer products, the results of this study are essential for the improvement of resource recovery in the Thermo-Re® process.

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DOE OSTI2012

A Review of Recent Impurity Measurements of LANL Material

The Applied Computational Engineering and Statistics (ACES) group of the Savannah River National Laboratory (SRNL) was asked to review recent measurements performed by the Los Alamos National Laboratory (LANL) on material from that facility that is being considered for processing through the Mixed Oxide (MOX) Fuel Fabrication Facility (MFFF) at the Savannah River Site (SRS). There are specification limits for impurities in the feed to the MOX facility: a maximum limit and an exceptional limit. The limits for an impurity apply to the population of concentration values for that impurity for a class of material that is to be processed through MOX. For the purposes of this report, these limits were defined as follows. The concentration of an elemental impurity, expressed as micrograms of the element per gram of plutonium (µg/g Pu), is to be no more than the maximum limit for that element for 98% of the material coming through MOX; that is, 98% of the material processed at MOX is to have a concentration of the given element less than the maximum limit. In addition, the concentration for a given element is to be no more than the exceptional limit for that element for 99.9% of the material processed through MOX. The measurements evaluated as part of this study included LANL blend lots 1 through 29 and cover carbon (C), chlorine (Cl), fluorine (F), nitrogen (N), phosphorous (P), and sulfur (S). Note that all of the measurements for each impurity were below their respective maximum (and obviously, therefore, their exceptional) limits. Thus, there is no immediate concern regarding the LANL material being suitable for processing through MOX. Two approaches were used to investigate the quantiles of the impurity populations. The first approach used was a nonparametric approach. While the results from this approach did not indicate any problems for any of the impurities, there was too little data available to lead to confident statements about satisfying the maximum and exceptional limits. Impurity data from additional random samples of the LANL material would be needed to increase the confidence level associated with the results from a nonparametric approach for investigating the population quantiles of interest. For S, F, and Cl, only a nonparametric approach was used. A second approach, a parametric approach, was attempted for C, P, and N. However, the results for the P and N measurements indicated that each of their respective populations was not well modeled by a normal or by a lognormal distribution. Thus, the conclusions for the P and N populations were those provided by the nonparametric approach. From the parametric approach, the results for C indicated no issue in the LANL material meeting the maximum limit for this element assuming that the measurements for this element follow a lognormal distribution.

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DOE OSTI2013

The Environmental Protection Agency's Safety Standards for Disposal of Spent Nuclear Fuel: Potential Path Forward in Response to the Report of the Blue Ribbon Commission on America's Nuclear Future - 13388

Following the decision to withdraw the Yucca Mountain license application, the Department of Energy created a Blue Ribbon Commission (BRC) on America's Nuclear Future, tasked with recommending a national strategy to manage the back end of the nuclear fuel cycle. The BRC issued its final report in January 2012, with recommendations covering transportation, storage and disposal of spent nuclear fuel (SNF); potential reprocessing; and supporting institutional measures. The BRC recommendations on disposal of SNF and high-level waste (HLW) are relevant to the U.S. Environmental Protection Agency (EPA), which shares regulatory responsibility with the Nuclear Regulatory Commission (NRC): EPA issues 'generally applicable' performance standards for disposal repositories, which are then implemented in licensing. For disposal, the BRC endorses developing one or more geological repositories, with siting based on an approach that is adaptive, staged and consent-based. The BRC recommends that EPA and NRC work cooperatively to issue generic disposal standards-applying equally to all sites-early in any siting process. EPA previously issued generic disposal standards that apply to all sites other than Yucca Mountain. However, the BRC concluded that the existing regulations should be revisited and revised. The BRC proposes a number of general principles to guide the development of future regulations. EPA continues to review the BRC report and to assess the implications for Agency action, including potential regulatory issues and considerations if EPA develops new or revised generic disposal standards. This review also involves preparatory activities to define potential process and public engagement approaches. (authors)

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DOE OSTI2011

Investigations on Repository Near-Field Thermal Modeling - Repository Science/Thermal Load Management & Design Concepts (M41UF033302) (Rev.1)

The modeling tools generated in MathCAD, Excel, and MatLab were used to calculate the temperature evolution for combinations of waste form and geologic medium, assuming a particular emplacement layout for each concept (Sutton et al. 2011). Two types of spent nuclear fuel assemblies (SNFA) were considered, namely UOX from an open fuel cycle and MOX from a modified-­‐open fuel cycle. Four types of high level waste (HLW) canisters were considered, namely “co-­‐extraction” glass from a modified-­‐open fuel cycle and “new extraction” glass, electrochemical ceramic (EC-­‐C) and electrochemical metal (EC-­‐M) from a closed fuel cycle. While the “coextraction” process is similar in function to the industrial Co-­‐Extraction™ (COEX) process deployed by AREVA, the two processes assume different processing methods and steps and so the product and waste streams cannot be directly compared. Similar is true for the “new extraction” process documented in this report and the NUEX industrial process proposed by Energy Solutions, which also cannot be directly compared.

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DOE OSTI2015

Numerical modeling of groundwater flow in the Navajo sandstone aquifer at the Tuba city, Arizona, disposal site - 15167

A numerical model is being developed to describe groundwater flow in the Navajo Sandstone aquifer that underlies the US DOE Office of Legacy Management Tuba City disposal site that is located near Tuba City, Arizona. The site is a former uranium-ore processing mill that operated from 1956 until 1966. Resulting groundwater contamination extends approximately 457 meters (1,500 feet) off the site. The primary contaminants are nitrate, sulfate, and uranium. Onsite solid waste encapsulation was completed by 1990 and pump-and-treat groundwater remediation was implemented in 2002. A site conceptual model, along with an approach to numerically simulate groundwater flow and advective transport of contaminants at the site, is being developed. Numerical model calibration will address transient periods of active and inactive groundwater withdrawal during the remedial action. The calibrated model will be applied to forecast contaminant capture under the current and hypothetical groundwater extraction scenarios. (authors)

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DOE OSTI2024

Glass Formulation and Testing with RPP-WTP HLW Simulants (Final Report)

This report presents the results from HLW glass formulation work that was conducted at the Vitreous State Laboratory of The Catholic University of America during Part B1 of the RPP-WTP Project (formally known as TWRS-P) in support of the Privatization contractor, BNFL, Inc. Glass formulation development is required to provide data that are essential for design of the vitrification facility in the near term and for safe and reliable operation of that facility in the longer-term. These data also form the bases from which contractually and technically acceptable immobilized high-level waste (IHLW) products will be devised. Glass formulation therefore impacts many aspects of the vitrification facility design, overall process economics, and contractual compliance. As an integral part of the overall system design, development of glass formulations requires input from many sources including tank waste characterization, pretreatment process definition, flow sheet development, and processing schedules. Accordingly, the glass formulation effort must be responsive to new information as the facility design basis evolves.

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DOE OSTI2021

Distribution of U, Pu and Np in a Mo-99 Recovery Process using Sachtopore NP (titania based) Absorbent Material

A laboratory scale mockup of a prototypical Mo-99 recovery process has been operated in a radioactive materials hood at Savannah River National Laboratory. This equipment has been operated with realistic concentrations of uranium (U-238), plutonium (94% Pu-239), neptunium (Np-237), and non-radioisotopes of common fission products (including Mo). The goal of this work was to determine the amounts of U, Pu, and Np in the liquid waste streams created by the wash streams for the production process. The key question was how the initial acid wash volume will be handled, as this solution contains residual raffinate which amounted to ~ 3% ofthe mass ofthe feed solution in this experiment. If the initial 1.9 bed volumes (BV) of acid wash were recycled as in this experiment then the combined wash solutions can be expected to contain 0.4 g U/L, 2.7 pg Pu/L and < 14 pg Np/L. If, on the other extreme, the entire acid wash solution was discarded as waste, then the combined wash solutions can be expected to contain 11 g U/L, 3.8 pg Pu/L and ~ 80 pg Np/L. The Sachtopore NP absorbent (for Mo-99 recovery) retains a minuscule fraction ofthe U (2.3 mg U per g titania or 0.03% ofthe U in the feed). The uncertainties are too large to determine how close the absorbent is to saturation with U. Less mass but a higher fraction ofthe total Np was retained by the absorbent (0.7 pg Np per g titania or ~2% of the Np in the feed). As has been reported elsewhere, a large fraction ofthe Pu fed to the titania bed was retained by the absorbent (92% of Pu in the feed or 20 pg per g titania).

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DOE OSTI2012

F-Tank Farm Performance Assessment Updates through the Special Analysis Process at Savannah River Site - 12169

The F-Area Tank Farm (FTF) is owned by the U.S. Department of Energy and operated by Savannah River Remediation, LLC (SRR), Liquid Waste Operations contractor at DOE's Savannah River Site (SRS). The FTF is in the north-central portion of the SRS and occupies approximately 22 acres within F-Area. The FTF is an active radioactive waste storage facility consisting of 22 carbon steel waste tanks and ancillary equipment such as transfer lines, evaporators and pump tanks. An FTF Performance Assessment (PA) was prepared to support the eventual closure of the FTF underground radioactive waste tanks and ancillary equipment. The PA provides the technical basis and results to be used in subsequent documents to demonstrate compliance with the pertinent requirements identified below for final closure of FTF. The FTank Farm is subject to a state industrial waste water permit and Federal Facility Agreement. Closure documentation will include an F-Tank Farm Closure Plan and tank-specific closure modules utilizing information from the performance assessment. For this reason, the State of South Carolina and the Environmental Protection Agency must be involved in the performance assessment review process. The residual material remaining after tank cleaning is also subject to reclassification prior to closure via a waste determination pursuant to Section 3116 of the Ronald W. Reagan National Defense Authorization Act of Fiscal Year 2005. The projected waste tank inventories in the FTF PA provide reasonably bounding FTF inventory projections while taking into account uncertainties in the effectiveness of future tank cleaning technologies. As waste is removed from the FTF waste tanks, the residual contaminants will be sampled and the remaining residual inventory is characterized. In this manner, tank specific data for the tank inventories at closure will be available to supplement the waste tank inventory projections currently used in the FTF PA. For FTF, the new tank specific data will be evaluated through the Special Analysis process. The FTF Special Analyses process will be utilized to evaluate information regarding the final residual waste that will be grouted in place in the FTF Tanks and assess the potential impact the new inventory information has on the FTF PA assumptions and results. The Special Analysis can then be used to inform decisions regarding FTF tank closure documents. The purpose of this paper is to discuss the Special Analysis process and share insights gained while implementing this process. An example of an area of interest in the revision process is balancing continuous improvement versus configuration control of agreed upon methodologies. Other subjects to be covered include: 1) defining the scope of the revisions included in the Special Analysis, 2) determining which PA results should be addressed in the Special Analysis, and 3) deciding whether the Special Analysis should utilize more qualitative or quantitative assessments. For the SRS FTF, an FTF PA has been prepared to provide the technical basis and results to be used in subsequent documents to demonstrate compliance with the pertinent requirements for final closure of FTF. The FTF Special Analyses process will be utilized to evaluate the impact new information has on the FTF PA assumptions and results. The Special Analysis can then be used to inform decisions regarding FTF tank closure documents. In preparing SAs, it is crucial that the scope of the SA be well defined within the SA, since the specific scope will vary from SA to SA. Since the SAs are essentially addendums to the PA, the SA scope should utilize the PA as the baseline from which the SA scope is defined. The SA needs to focus on evaluating the change associated with the scope, and not let other changes interfere with the ability to perform that evaluation by masking the impact of the change. In preparing the SA, it is also important to let the scope determine whether the Special Analysis should utilize more qualitative or quantitative assessments and also which results from the PA should be addressed in the Special Analysis. These decisions can vary from SA and should not be predetermined. (author)

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DOE OSTI2013

Setting and stiffening of cementitious components in Cast Stone waste form for disposal of secondary wastes from the Hanford waste treatment and immobilization plant

Cast Stone is a cementitious waste form, a viable option to immobilize secondary nuclear liquid wastes generated from the Hanford Waste Treatment and Immobilization Plant. However, no study has been performed to understand the flow and stiffening behavior, which is essential to ensure proper workability and is important to safety in a nuclear waste field-scale application. X-ray diffraction, rheology, and ultrasonic wave reflection methods were used to understand the specific phase formation and stiffening of Cast Stone. Our results showed a good correlation between rheological properties of the fresh mixture and phase formation in Cast Stone. Secondary gypsum formation was observed with low concentration simulants, and the formation of gypsum was suppressed in high concentration simulants. A threshold concentration for the drastic change in stiffening was found at 1.56 M Na concentration. It was found that the stiffening of Cast Stone was strongly dependent on the concentration of simulant. Highlights: • A combination of XRD, UWR, and rheology gives a better understanding of Cast Stone. • Stiffening of Cast Stone was strongly dependent on the concentration of simulant. • A drastic change in stiffening of Cast Stone was found at 1.56 M Na concentration.

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DOE OSTI2015

Designing Pay-As-You-Throw schemes in municipal waste management services: A holistic approach

Highlights: • Pay-As-You-Throw (PAYT) schemes are becoming widespread in several countries. • Economic, organizational and technological issues have to be integrated in an efficient PAYT model design. • Efficiency refers to a PAYT system which support high citizen participation rates as well as economic sustainability. • Different steps and constraints have to be evaluated from collection services to type technologies. • An holistic approach is discussed to support PAYT systems diffusion. - Abstract: Pay-As-You-Throw (PAYT) strategies are becoming widely applied in solid waste management systems; the main purpose is to support a more sustainable – from economic, environmental and social points of view – management of waste flows. Adopting PAYT charging models increases the complexity level of the waste management service as new organizational issues have to be evaluated compared to flat charging models. In addition, innovative technological solutions could also be adopted to increase the overall efficiency of the service. Unit pricing, user identification and waste measurement represent the three most important processes to be defined in a PAYT system. The paper proposes a holistic framework to support an effective design and management process. The framework defines most critical processes and effective organizational and technological solutions for supporting waste managers as well as researchers.

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DOE OSTI2016

Experimental Evaluation of Dual-Opposed Jet Mixer Pump Performance for Slurry Mixing

Million-gallon double-shell tanks at Hanford are used to store transuranic, high-level, and low-level radioactive wastes. These wastes consist of a large volume of salt-laden solution covering a smaller volume of settled sludge primarily containing metal hydroxides. These wastes will be retrieved and processed into immobile waste forms suitable for permanent disposal. Retrieval is an important step in implementing these disposal scenarios. The retrieval concept evaluated is to use submerged dual-nozzle jet mixer pumps with horizontally oriented nozzles located near the tank floor that produce horizontal jets of fluid to mobilize the settled solids. The mixer pumps are oscillated through 180 about a vertical axis so the high velocity fluid jets sweep across the floor of the tank. After the solids are mobilized, the pumps will continue to operate at a reduced flow rate producing lower velocity jets sufficient to maintain the particles in a uniform suspension (concentration uniformity). Several types of waste and tank configurations exist at Hanford. The jet mixer pump systems and operating conditions required to mobilize sludge and maintain slurry uniformity will be a function of the waste type and tank configuration. The focus of this work was to conduct a 1/12-scale experiment to develop an analytical model to relate slurry uniformity to tank and mixer pump configurations, operating conditions, and sludge properties. This experimental study evaluated concentration uniformity in a 1/12-scale experiment varying the Reynolds number (Re), Froude number (Fr), and gravitational settling parameter (Gs) space. Simulant physical properties were chosen to obtain the required Re and Gs where Re and Gs were varied by adjusting the kinematic viscosity and mean particle diameter, respectively. Test conditions were achieved by scaling the jet nozzle exit velocity in a 75-in. diameter tank using a mock-up of a centrally located dual-opposed jet mixer pump located just above the tank floor. Concentration measurements at sampling locations throughout the tank were used to assess the degree of uniformity achieved during each test. Concentration data was obtained using a real time in-situ ultrasonic attenuation probe and post-test analysis of discrete batch samples. The undissolved solids concentration at these locations was analyzed to determine whether the tank contents were uniform (≤ ±10% variation about mean) or nonuniform (> ±10% variation about mean) in concentration. Concentration inhomogeneity was modeled as a function of dimensionless parameters. The parameters that best describe the maximum solids volume fraction that can be suspended were found to be 1) the Fr based on nozzle average discharge velocity and tank contents level and 2) the dimensionless particle size based on nozzle diameter. The dependence on the jet Re does not appear to be statistically significant.

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DOE OSTI2011

A design for a V&V and UQ discovery process.

There is currently sparse literature on how to implement systematic and comprehensive processes for modern V&V/UQ (VU) within large computational simulation projects. Important design requirements have been identified in order to construct a viable 'system' of processes. Significant processes that are needed include discovery, accumulation, and assessment. A preliminary design is presented for a VU Discovery process that accounts for an important subset of the requirements. The design uses a hierarchical approach to set context and a series of place-holders that identify the evidence and artifacts that need to be created in order to tell the VU story and to perform assessments. The hierarchy incorporates VU elements from a Predictive Capability Maturity Model and uses questionnaires to define critical issues in VU. The place-holders organize VU data within a central repository that serves as the official VU record of the project. A review process ensures that those who will contribute to the record have agreed to provide the evidence identified by the Discovery process. VU expertise is an essential part of this process and ensures that the roadmap provided by the Discovery process is adequate. Both the requirements and the design were developed to support the Nuclear Energy Advanced Modeling and Simulation Waste project, which is developing a set of advanced codes for simulating the performance of nuclear waste storage sites. The Waste project served as an example to keep the design of the VU Discovery process grounded in practicalities. However, the system is represented abstractly so that it can be applied to other M&S projects.

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DOE OSTI2012

Characterization and evaluation of caustic wash tank and solvent hold tank samples from MCU from august to september 2011

During processing of Salt Batches 3 and 4 in the Modular Caustic-Side Solvent Extraction Unit (MCU), the decontamination efficiency for cesium declined from historical values and from expectations based on laboratory testing. This report documents efforts to analyze samples of solvent and process solutions from MCU in an attempt to understand the cause of the reduced performance and to recommend mitigations. CWT Solutions from MCU from the time period of variable decontamination factor (DF) performance which covers from April 2011 to September 2011 (during processing of Salt Batch 4) were examined for impurities using chromatography and spectroscopy. The results indicate that impurities were found to be of two types: aromatic containing impurities most likely from Modifier degradation and aliphatic type impurities most likely from Isopar{reg_sign} L and tri-n-octylamine (TOA) degradation. Caustic washing the Solvent Hold Tank (SHT) solution with 1M NaOH improved its extraction ability as determined from {sup 22}Na uptake tests. Evidence from this work showed that pH variance in the aqueous solutions within the range of 1M nitric acid to 1.91M NaOH that contacted the solvent samples does not influence the analytical determination of the TOA concentration by GC-MS.

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