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Molten Salt Reactors and Electrochemical Reprocessing: Synthesis and Chemical Durability of Potential Waste Forms for Metal and Salt Waste Streams
The molten salt reactor (MSR) is one of the leading advanced nuclear reactor candidates to replace current nuclear reactor technologies in the U.S. Besides having more economical and reliable designs, MSRs have are amenable to a closed fuel cycle, in which electrochemical reprocessing can be performed to recycle the used nuclear fuel. This review intends to provide information about potential waste forms for metal and salt waste streams from these salt-based nuclear processes. Metal waste streams arise from reactor components and structural materials. Salt waste streams are generated during reactor operations as fission products build up in salt-fueled systems. Waste forms that have the highest waste loading and/or have shown the most commercial promise are discussed with an emphasis on the current state of efforts to understand the synthesis and chemical durability of metal and ceramic waste forms.
SRNL CRP progress report [Development of Melt Processed Ceramics for Nuclear Waste Immobilization]
A multi-phase ceramic waste form is being developed at the Savannah River National Laboratory (SRNL) for treatment of secondary waste streams generated by reprocessing commercial spent nuclear. The envisioned waste stream contains a mixture of transition, alkali, alkaline earth, and lanthanide metals. Ceramic waste forms are tailored (engineered) to incorporate waste components as part of their crystal structure based on knowledge from naturally found minerals containing radioactive and non-radioactive species similar to the radionuclides of concern in wastes from fuel reprocessing. The ability to tailor ceramics to mimic naturally occurring crystals substantiates the long term stability of such crystals (ceramics) over geologic timescales of interest for nuclear waste immobilization [1]. A durable multiphase ceramic waste form tailored to incorporate all the waste components has the potential to broaden the available disposal options and thus minimize the storage and disposal costs associated with aqueous reprocessing.
Evaluation of Technologies for Destruction of LDR Organics in Hanford Tank Waste
Aqueous Hanford tank wastes contain soluble organics and some tanks contain small amounts (<100 mg/L) of organics that are regulated under the Land Disposal Restrictions (LDR) portions of the Resource Conservation and Recovery Act (RCRA). Most of these organics can be removed by evaporation, but some are not. Methods to destroy/remove organics that are regulated by the LDR section of the RCRA and that are not removed by evaporation may be needed if ambient temperature waste treatment processes are used to immobilize aqueous Hanford tank wastes. To identify viable and compatible organic removal or destruction pretreatment methods an evaluation was performed by a team of researchers. The team utilized a Systems Engineering Approach that examines all aspects of the technology, based on information available in the literature and the experience of the team members. That evaluation led to recommendations by the team to perform testing on technologies to determine efficacy in destroying organics in Hanford tank waste liquids. The primary technologies recommended are chemical oxidants, including permanganate, peroxymonosulfate or peroxydisulfate (PMS/PDS), hydrogen peroxide, and ozone. Ultraviolet light irradiation of the stream with a solid catalyst sorbent is also recommended for testing. A generalized description of the test program is also included.
Raw Liquid Waste Treatment System and Process
A raw sewage treatment process is disclosed in which substantially all the non-dissolved matter, suspended in the sewage water is first separated from the water, in which at least organic matter remains dissolved. The non-dissolved material is pyrolyzed to form an activated carbon and ash material without the addition of any conditioning agents. The activated carbon and ash material is added to the water from which the non-dissolved matter was removed. The activated carbon and ash material adsorbs the organic matter dissolved in the water and is thereafter supplied in a counter flow direction and combined with the incoming raw sewage to at least facilitate the separation of the non-dissolved settleable materials from the sewage water. Carbon and ash material together with the non-dissolved matter which was separated from the sewage water are pyrolyzed to form the activated carbon and ash material.
Prototype wash water renovation system integration with government-furnished wash fixture
The requirements of a significant quantity of proposed life sciences experiments in Shuttle payloads for available wash water to support cleansing operations has provided the incentive to develop a technique for wash water renovation. A prototype wash water waste renovation system which has the capability to process the waste water and return it to a state adequate for reuse in a typical cleansing fixture designed to support life science experiments was investigated. The resulting technology is to support other developments efforts pertaining to water reclamation by serving as a pretreatment step for subsequent reclamation procedures.
Waste Management Improvement Initiatives at Atomic Energy of Canada Limited - 13091
Atomic Energy of Canada Limited's (AECL) Chalk River Laboratories (CRL) has been in operation for over 60 years. Radioactive, mixed, hazardous and non-hazardous wastes have been and continue to be generated at CRL as a result of research and development, radioisotope production, reactor operation and facility decommissioning activities. AECL has implemented several improvement initiatives at CRL to simplify the interface between waste generators and waste receivers: - Introduction of trained Waste Officers representing their facilities or activities at CRL; - Establishment of a Waste Management Customer Support Service as a Single-Point of Contact to provide guidance to waste generators for all waste management processes; and - Implementation of a streamlined approach for waste identification with emphasis on early identification of waste types and potential disposition paths. As a result of implementing these improvement initiatives, improvements in waste management and waste transfer efficiencies have been realized at CRL. These included: 1) waste generators contacting the Customer Support Service for information or guidance instead of various waste receivers; 2) more clear and consistent guidance provided to waste generators for waste management through the Customer Support Service; 3) more consistent and correct waste information provided to waste receivers through Waste Officers, resulting in reduced time and resources required for waste management (i.e., overall cost); 4) improved waste minimization and segregation approaches, as identified by in-house Waste Officers; and 5) enhanced communication between waste generators and waste management groups. (authors)
Impact of Corrections to the Spallings Volume Calculation on Waste Isolation Pilot Plant Performance Assessment - 16135
The numerical code DRSPALL (from direct release spallings) is written to calculate the volume of Waste Isolation Pilot Plant solid waste subject to material failure and transport to the surface (i.e., spallings) as a result of a hypothetical future inadvertent drilling intrusion into the repository. An error in the implementation of the DRSPALL finite difference equations was discovered and documented in a software problem report in accordance with the quality assurance procedure for software requirements. This paper describes the corrections to DRSPALL and documents the impact of the new spallings data from the modified DRSPALL on previous performance assessment calculations. Updated performance assessments result in more simulations with spallings, which generally translates to an increase in spallings releases to the accessible environment. Total normalized radionuclide releases using the modified DRSPALL data were determined by forming the summation of releases across each potential release pathway, namely borehole cuttings and cavings releases, spallings releases, direct brine releases, and transport releases. Because spallings releases are not a major contributor to the total releases, the updated performance assessment calculations of overall mean complementary cumulative distribution functions for total releases are virtually unchanged. Therefore, the corrections to the spallings volume calculation did not impact Waste Isolation Pilot Plant performance assessment calculation results. (authors)
One System Overview - 16579
The U.S. Department of Energy (DOE), Office of River Protection (ORP) is responsible for managing and completing the River Protection Project mission, which is to 'safeguard the nuclear waste stored in Hanford's 177 underground tanks, and to manage the waste safely and responsibly until it can be treated in the Waste Treatment and Immobilization Plant for final disposition'. The Office of River Protection's work scope is currently performed through two primary contracts: - The Tank Operations Contract, held by Washington River Protection Solutions LLC, (WRPS) includes the construction, operation, and maintenance activities necessary to safely store, retrieve, and transfer tank wastes; provide supplemental tank waste treatment; provide storage and/or disposal of primary and secondary waste streams; design, construction and commissioning of the Low-Activity Waste Pretreatment System; and support ORP to integrate Hanford Tank Waste Treatment and Immobilization Plant (WTP) completion and startup with Tank Farms operations. - The WTP Contract, held by Bechtel National, Inc. (BNI), includes the design, construction, and commissioning of a Pretreatment Facility, two vitrification facilities (one for high-level waste and one for low-activity waste), a dedicated analytical laboratory, and supporting facilities to treat radioactive tank wastes by immobilizing them into a stable glass waste form. One System was established as a means to improve the integration between the tank farms and the WTP project to support its safe and successful startup. One System's scope and purpose focus on mission integration consistent with DOE's plans to treat tank waste in phases, starting with direct feed of the low-activity waste stream to the WTP's Low-Activity Waste (LAW) Vitrification Facility (referred to as DFLAW). The One System organization now has four major focus areas: - Flowsheet Integration? Integrated River Protection Project (RPP) flowsheet development and management; developing a gaps, risks, and opportunities management plan and technical roadmap; and waste feed qualification. - Mission Analysis and Planning? Strategic planning, system planning, and modeling integration. - WTP Startup, Commissioning, and Operations Integration? Interface Control Document (ICD) management, coordinating facilities startup-to-commissioning-to-operations, contract directives and standards identification, and DFLAW program integration. - Project Integration and Controls? Integrated schedule, metrics/dashboards monitoring, and One System risk register. ORP established the DFLAW Program Office in February 2015 as one of its key performance goals. ORP staff, along with contractor managers, have identified roles and responsibilities for the each of the four major focus areas. One System has established an Executive Council and Governance Board to drive program progress and make decisions on DFLAW. This approach allows appropriate government and contractor senior management involvement in the DFLAW Program. Monthly critical path analysis on the integrated DFLAW schedule is being performed. Interface control documents specific to DFLAW have been developed, and system planning and modeling tools are being used to help define the DFLAW flowsheet. (authors)
Qualification of Numerical and Semi-Analytical Modeling Codes for Thermal Design of HLW Repository - 18455
Disposal in a geological repository is a viable option for safely isolating high-level radioactive waste. Thermal processes induced by decay heat from the radioactive waste may impact the integrity of the engineered barrier system, and may lead to fluid flow and transport; and the associated migration of radionuclides. This study looks at an analysis of thermal conduction for the emplacement of high-level waste in a repository located in bedded salt. The simulations used analytical and numerical methods to study conductive heat transport in a repository. This study concentrated on heat flow in a central waste package with contributions from adjacent waste packages and drifts. Of particular importance to this work is comparison of predictions of peak temperature at the drift wall and at the waste package surface using different solution methods. Simulation results of analytical and numerical modeling methods are compared. The results show that predictions of the codes were comparable under identical initial and boundary conditions. (authors)
Development of a Comprehensive and Centralized Waste Management System - 19412
Information Systems Laboratories (ISL) has designed a new single, integrated, waste management and control system to administer all aspects of nuclear waste management. The overriding goal of the initiative is to provide federal, state, and local agencies with operational awareness, management, and programmatic support for all functions related to nuclear waste management. Over decades of waste management federal agencies have sponsored or directly paid for the development, operation, and control of multiple systems to track and control its waste - with varied success. Multiple contractors have generated disparate control systems/databases and literally mountains of data. Past approaches have not provided a single, integrated, real time data management system. ISL's analysis of past failed efforts has reveal four common symptoms: - Control/management systems that are not compatible; - Programmatic costs that increase with systems use and re-work; - Systems focused on specific sets of data; - Inaccurate or outdated data sets. An integrated waste management and control system that collects and displays real-time, accurate inventory, waste container certification, transportation certification, emplacement, and shipment related data improve operational awareness and overcomes these limitations. Using its vast knowledge and experience in developing numerous waste tracking and management systems, ISL has leveraged its own in-house knowledge and gathered requests from stakeholders all across the industry to design a system that meets the needs of users at all levels of the nuclear waste management process. Using the highly successful and widely used Waste Data System (WDS) designed for the Waste Isolation Pilot Plant as a core component, ISL has designed a system that greatly expands on the functionality of the WDS to exceed its current focus of management of Transuranic Waste shipments. The new system is designed to provide the ability to track a wide range of waste types from Transuranic, High Level, Low Level, Mixed, and any nuclear related material. The main focus of the system is to provide federal regulators a comprehensive and real-time oversight into the handling of all nuclear waste materials. Oversight activities include, but are not limited to, strategy development, projections, metrics, incentive development, tracking, budget review, government cost estimating, and integrated schedules. The major components of the system are summarized below: - The Centralized Waste Management System (CWMS), which will include assimilating and validating known sources of data into the CWMS. - The programmatic reporting support component, which will handle queries from regulators, track compliance with regulatory requirements, and maintain the dashboard for federal management. - Both the CWMS and the programmatic reporting support component will use a standard set of business rules that govern system operations and allow site and program specific needs and limits for all waste programs and types to be captured and maintained. This presentation will provide details of each component of the system detailing its use, interfaces with other components, and value to stakeholders. (authors)
Enhanced LAW Glass Correlation - Phase 1
About 50 million gallons of high-level mixed waste is currently stored in underground tanks at the United States Department of Energy’s (DOE’s) Hanford site in the State of Washington. The Hanford Tank Waste Treatment and Immobilization Plant (WTP) will provide DOE’s Office of River Protection (ORP) with a means of treating this waste by vitrification for subsequent disposal. The tank waste will be separated into low- and high-activity waste fractions, which will then be vitrified respectively into Immobilized Low Activity Waste (ILAW) and Immobilized High Level Waste (IHLW) products. The ILAW product will be disposed in an engineered facility on the Hanford site while the IHLW product is designed for acceptance into a national deep geological disposal facility for high-level nuclear waste. The ILAW and IHLW products must meet a variety of requirements with respect to protection of the environment before they can be accepted for disposal. Acceptable glass formulations for vitrification of Hanford low activity waste (LAW) must meet a variety of product quality, processability, and waste loading requirements. To this end, The Vitreous State Laboratory (VSL) at The Catholic University of America (CUA) developed and tested a number of glass formulations during Part A, Part B1 and Part B2 of the WTP development program. The testing resulted in the selection of target glass compositions for the processing of eight of the Phase I LAW tanks. The selected glass compositions were tested at the crucible scale to confirm their compliance with ILAW performance requirements. Duramelter 100 (DM100) and LAW Pilot Melter tests were then conducted to demonstrate the viability of these glass compositions for LAW vitrification at high processing rates.
Numerical modeling of Joule heated ceramic melter
Computational fluid dynamics and heat transfer models of waste glass melters are being developed to support the vitrification campaign at the Waste Treatment and Immobilization Plant (WTP) as part of the United States nuclear waste stewardship and environmental protection programs. The WTP mission aims to achieve the stable and durable processing of vitrified waste in the safest, most efficient, and economical manner possible. Hanford’s tank waste is far more complex and varied than the waste treated by other vitrification facilities and both startup and long-term operational challenges are likely to be even greater than prior experience has shown. There are thousands of different waste compositions, which makes processing the waste a complex and challenging task. Models of test melters, pilot-scale, and full-scale melters have been developed to provide understanding and insight into the various physical and chemical phenomena occurring during vitrification. So the results of these modeling activities will be used to support the WTP operations to process legacy nuclear waste into a stable form for disposal.
Life Extension Program for the Modular Caustic Side Solvent Extraction Unit at Savannah River Site - 13179
Caustic Side Solvent Extraction (CSSX) is currently used at the U.S. Department of Energy (DOE) Savannah River Site (SRS) for removal of cesium from the high-level salt-wastes stored in underground tanks. Currently, the Actinide Removal Process (ARP) and the CSSX process are deployed in the (ARP)/Modular CSSX Unit (MCU), to process salt waste for permanent disposition. The CSSX technology utilizes a multi-component organic solvent and annular centrifugal contactors to extract cesium from alkaline salt waste. The original plant was permitted for a three year design life; however, given the successful operation of the plant, a life extension program was completed to continue operations. The program included detailed engineering analyses of the life-expectancy of passive and active components, resulting in component replacement and/or maintenance and monitoring program improvements. The program also included a review of the operations and resulted in a series of operational improvements. Since the improvements have been made, an accelerated processing rate has been demonstrated. In addition, plans for instituting a next-generation solvent are in place and will enhance the decontamination factors. (author)
Investigations for improved tank characterization and cleaning - 15454
In the process of tank closure, significant waste characterization and chemical cleaning occur. Costly characterization is performed at numerous processing stages. A need exists for new strategies and technologies to understand, optimize, scale, and speed up tank waste characterization with the end goal of reducing costs through implementation of programmatic changes that accelerate tank waste processing and tank closure schedules. This paper will explore a possible alternative to waste characterization methodologies and cleaning technologies to reduce costs and improve processing efficiency. (authors)
Estimating Residual Solids Volume In Underground Storage Tanks
The Savannah River Site liquid waste system consists of multiple facilities to safely receive and store legacy radioactive waste, treat, and permanently dispose waste. The large underground storage tanks and associated equipment, known as the 'tank farms', include a complex interconnected transfer system which includes underground transfer pipelines and ancillary equipment to direct the flow of waste. The waste in the tanks is present in three forms: supernatant, sludge, and salt. The supernatant is a multi-component aqueous mixture, while sludge is a gel-like substance which consists of insoluble solids and entrapped supernatant. The waste from these tanks is retrieved and treated as sludge or salt. The high level (radioactive) fraction of the waste is vitrified into a glass waste form, while the low-level waste is immobilized in a cementitious grout waste form called saltstone. Once the waste is retrieved and processed, the tanks are closed via removing the bulk of the waste, chemical cleaning, heel removal, stabilizing remaining residuals with tailored grout formulations and severing/sealing external penetrations. The comprehensive liquid waste disposition system, currently managed by Savannah River Remediation, consists of 1) safe storage and retrieval of the waste as it is prepared for permanent disposition; (2) definition of the waste processing techniques utilized to separate the high-level waste fraction/low-level waste fraction; (3) disposition of LLW in saltstone; (4) disposition of the HLW in glass; and (5) closure state of the facilities, including tanks. This paper focuses on determining the effectiveness of waste removal campaigns through monitoring the volume of residual solids in the waste tanks. Volume estimates of the residual solids are performed by creating a map of the residual solids on the waste tank bottom using video and still digital images. The map is then used to calculate the volume of solids remaining in the waste tank. The ability to accurately determine a volume is a function of the quantity and quality of the waste tank images. Currently, mapping is performed remotely with closed circuit video cameras and still photograph cameras due to the hazardous environment. There are two methods that can be used to create a solids volume map. These methods are: liquid transfer mapping / post transfer mapping and final residual solids mapping. The task is performed during a transfer because the liquid level (which is a known value determined by a level measurement device) is used as a landmark to indicate solids accumulation heights. The post transfer method is primarily utilized after the majority of waste has been removed. This method relies on video and still digital images of the waste tank after the liquid transfer is complete to obtain the relative height of solids across a waste tank in relation to known and usable landmarks within the waste tank (cooling coils, column base plates, etc.). In order to accurately monitor solids over time across various cleaning campaigns, and provide a technical basis to support final waste tank closure, a consistent methodology for volume determination has been developed and implemented at SRS.
Fluid bed gasification – Plasma converter process generating energy from solid waste: Experimental assessment of sulphur species
Highlights: • We investigate gaseous sulphur species whilst gasifying sulphur-enriched wood pellets. • Experiments performed using a two stage fluid bed gasifier – plasma converter process. • Notable SO{sub 2} and relatively low COS levels were identified. • Oxygen-rich regions of the bed are believed to facilitate SO{sub 2}, with a delayed release. • Gas phase reducing regions above the bed would facilitate more prompt COS generation. - Abstract: Often perceived as a Cinderella material, there is growing appreciation for solid waste as a renewable content thermal process feed. Nonetheless, research on solid waste gasification and sulphur mechanisms in particular is lacking. This paper presents results from two related experiments on a novel two stage gasification process, at demonstration scale, using a sulphur-enriched wood pellet feed. Notable SO{sub 2} and relatively low COS levels (before gas cleaning) were interesting features of the trials, and not normally expected under reducing gasification conditions. Analysis suggests that localised oxygen rich regions within the fluid bed played a role in SO{sub 2}’s generation. The response of COS to sulphur in the feed was quite prompt, whereas SO{sub 2} was more delayed. It is proposed that the bed material sequestered sulphur from the feed, later aiding SO{sub 2} generation. The more reducing gas phase regions above the bed would have facilitated COS – hence its faster response. These results provide a useful insight, with further analysis on a suite of performed experiments underway, along with thermodynamic modelling.
A Review of Existing Policies Affecting the Jettison of Waste in Low Earth Orbit and Deep Space
The management of waste generated onboard spacecraft during future long-duration deep-space missions will require different solutions from those currently implemented on the International Space Station which consist exclusively of collecting, storing, and returning the waste to Earth. Alternative options for managing spacecraft waste are to process it for recycling and recovery of resources, and to jettison it overboard in a solid form (such as a compacted tile) or in a gaseous form after torrefaction or other trash-to-gas technologies. The waste generated during a deep-space mission is derived mainly from spacecraft logistics supplies, food and beverage residues, personal or scientific items used by the crew, human metabolic waste, and unused spare components. Uncontained and unprocessed trash is a potential health hazard and a habitat volume liability, which makes onboard long-term storage an inefficient and non-optimal option. However, the jettison of solid, processed waste appears to be an effective solution for crewed deep-space missions, leading not only to volume reduction and habitat safening, but also to considerable mass savings in the spacecraft’s propulsion system. However, the disposal of trash overboard also creates a navigation hazard for spacecraft and the potential risk of contamination of planetary bodies, interfering with the search for life. This paper investigates the requirements covered by existing policies that could affect the jettison concept of operations and system design.