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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

RCRA Part A Permit Application for Waste Management Activities at the Nevada National Security Site Hazardous Waste Storage Unit (HWSU), Explosive Ordnance Disposal Unit (EODU), Mixed Waste Storage Unit (MWSU), and Mixed Waste Disposal Unit (MWDU)

This document is the first volume in a Resource Conservation Recovery Act (RCRA) Permit Application to the Nevada Division of Environmental Protection for continued operation of certain facilities on the Nevada National Security Site (NNSS), owned by the U.S. Department of Energy, National Nuclear Security Administration Nevada Field Office (NNSA/NFO). This RCRA permit application pertains to the Hazardous Waste Storage Unit (HWSU), the Explosive Ordnance Disposal Unit (EODU), the Mixed Waste Storage Unit (MWSU), and the Mixed Waste Disposal Unit (MWDU). This volume lists the relevant permits for each of these facilities and provides maps and drawings of many aspects of them. The companion volumes, which provide descriptive text and discussion and additional graphics, are jointly considered Part B of the permit application. Those volumes are identified by the following document numbers: DOE/NV/25946--2442, DOE/NV/25946--2448, DOE/NV/25946--2425, and DOE/NV/25946--2429.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Host-guest prospects of neodymium and gadolinium ultraphosphate frameworks for nuclear waste storage: Multi-temperature topological analysis of nanoporous cages in RP{sub 5}O{sub 14}

Highlights: • The temperature-dependent cage topologies of RP{sub 5}O{sub 14} (R = Nd or Gd) were examined. • A topological analysis revealed similar cage structure for RP{sub 5}O{sub 14} (R = Nd or Gd). • One exception: the 8/4 cage topology of NdP{sub 5}O{sub 14} lacks structural cross-linking. • Volume (UO{sub 2} or PuO{sub 2}) ≫ 8/4 topology in RP{sub 5}O{sub 14} (R = Nd or Gd). • RP{sub 5}O{sub 14} (R = Nd or Gd) are good prospective host media for nuclear waste storage. - Abstract: Rare-earth ultraphosphate (RP{sub 5}O{sub 14}) framework materials are potential host media for nuclear waste storage, since cages within their nanoporous structures have volumes that match well those of prospective guests such as uranium or plutonium ions. Good volume matches of host cages and guest compounds are nonetheless not the only structural requirement for ensuring viable nuclear waste storage. Host structures also need to be stable enough to withstand the typical environmental conditions of long-term storage of spent nuclear fuel. To this end, the nanoporous cage topologies of neodymium and gadolinium ultraphosphate, NdP{sub 5}O{sub 14} and GdP{sub 5}O{sub 14}, are investigated as a function of temperature. Topological analysis shows that, while both compounds are essentially isostructural, thus displaying the same type of cage structures, the cage volumes of NdP{sub 5}O{sub 14} are significantly larger than those of GdP{sub 5}O{sub 14}, with one stark exception. This exception concerns the cage of NdP{sub 5}O{sub 14} whose 8/4 topology lacks structural cross-linking that would otherwise give it much more strength. This 'squashed' cage appears to owe its origins to the specific nature of crystallographic twinning in NdP{sub 5}O{sub 14}, which causes strain that needs alleviating; squashing the 8/4 cage in NdP{sub 5}O{sub 14} would be the most susceptible option towards this end, since its cage manifests the weakest structural construct. GdP{sub 5}O{sub 14} succumbs to a gradual contraction of its 8/4 cage only with increasing temperature above 300 K; this is well below its second-order monoclinic-to-orthorhombic phase transition at 420–430 K; which is 420 K for NdP{sub 5}O{sub 14}. Fortunately, the volumes of heavy metal ions that arise from spent nuclear fuels do not match the size requirements of cages with 8/4 topology in RP{sub 5}O{sub 14} hosts needed for encapsulation; otherwise, radiation leakage of such containment would present a risk. Both NdP{sub 5}O{sub 14} and GdP{sub 5}O{sub 14} would therefore seem to offer good prospects as host media for nuclear waste storage.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

ADMINISTRATIVE AND ENGINEERING CONTROLS FOR THE OPERATION OF VENTILATION SYSTEMS FOR UNDERGROUND RADIOACTIVE WASTE STORAGE TANKS

Liquid radioactive wastes from the Savannah River Site are stored in large underground carbon steel tanks. The majority of the waste is confined in double shell tanks, which have a primary shell, where the waste is stored, and a secondary shell, which creates an annular region between the two shells, that provides secondary containment and leak detection capabilities should leakage from the primary shell occur. Each of the DST is equipped with a purge ventilation system for the interior of the primary shell and annulus ventilation system for the secondary containment. Administrative flammability controls require continuous ventilation to remove hydrogen gas and other vapors from the waste tanks while preventing the release of radionuclides to the atmosphere. Should a leak from the primary to the annulus occur, the annulus ventilation would also serve this purpose. The functionality of the annulus ventilation is necessary to preserve the structural integrity of the primary shell and the secondary. An administrative corrosion control program is in place to ensure integrity of the tank. Given the critical functions of the purge and annulus ventilation systems, engineering controls are also necessary to ensure that the systems remain robust. The system consists of components that are constructed of metal (e.g., steel, stainless steel, aluminum, copper, etc.) and/or polymeric (polypropylene, polyethylene, silicone, polyurethane, etc.) materials. The performance of these materials in anticipated service environments (e.g., normal waste storage, waste removal, etc.) was evaluated. The most aggressive vapor space environment occurs during chemical cleaning of the residual heels by utilizing oxalic acid. The presence of NO{sub x} and mercury in the vapors generated from the process could potentially accelerate the degradation of aluminum, carbon steel, and copper. Once identified, the most susceptible materials were either replaced and/or plans for discontinuing operations are executed.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2011

Study of the VOC emissions from a municipal solid waste storage pilot-scale cell: Comparison with biogases from municipal waste landfill site

Highlights: > Follow-up of the emission of VOCs in a municipal waste pilot-scale cell during the acidogenesis and acetogenesis phases. > Study from the very start of waste storage leading to a better understanding of the decomposition/degradation of waste. > Comparison of the results obtained on the pilot-scale cell with those from 3 biogases coming from the same landfill site. > A methodology of characterization for the progression of the stabilization/maturation of waste is finally proposed. - Abstract: The emission of volatile organic compounds (VOCs) from municipal solid waste stored in a pilot-scale cell containing 6.4 tonnes of waste (storage facility which is left open during the first period (40 days) and then closed with recirculation of leachates during a second period (100 days)) was followed by dynamic sampling on activated carbon and analysed by GC-MS after solvent extraction. This was done in order to know the VOC emissions before the installation of a methanogenesis process for the entire waste mass. The results, expressed in reference to toluene, were exploited during the whole study on all the analyzable VOCs: alcohols, ketones and esters, alkanes, benzenic and cyclic compounds, chlorinated compounds, terpene, and organic sulphides. The results of this study on the pilot-scale cell are then compared with those concerning three biogases from a municipal waste landfill: biogas (1) coming from waste cells being filled or recently closed, biogas (2) from all the waste storage cells on site, and biogas (3) which is a residual gas from old storage cells without aspiration of the gas. The analysis of the results obtained revealed: (i) a high emission of VOCs, principally alcohols, ketones and esters during the acidogenesis; (ii) a decrease in the alkane content and an increase in the terpene content were observed in the VOCs emitted during the production of methane; (iii) the production of heavier alkanes and an increase in the average number of carbon atoms per molecule of alkane with the progression of the stabilisation/maturation process were also observed. Previous studies have concentrated almost on the analysis of biogases from landfills. Our research aimed at gaining a more complete understanding of the decomposition/degradation of municipal solid waste by measuring the VOCs emitted from the very start of the landfill process i.e. during the acidogenesis and acetogenesis phases.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2026

Hydrogen Recombiner Catalyst Evaluations for Waste Storage

Radiolysis of water in nuclear waste storage generates hydrogen gas that can accumulate within sludge style waste and be rapidly released during agitation events, creating a significant flammability hazard. Engineering controls are therefore required to limit hydrogen concentrations during both quiescent storage and transient disturbances. Catalytic recombination of hydrogen in waste storage offgas is a proven mitigation strategy, maintaining hydrogen levels below flammability limits and managing sudden concentration spikes. Conventional recombiners rely on platinum and/or palladium catalysts, with development efforts focused on extending service life, increasing active surface area, and ensuring safe deployment in radioactive environments. Savannah River National Laboratory (SRNL) is evaluating a newly developed hydrogen recombiner catalyst from Canadian Nuclear Laboratories as a cost-effective and durable alternative for nuclear waste applications. Testing was conducted in SRNL’s Shielded Cells facility, which enables reduced-scale experimental modeling under radiation fields and near-use-case conditions relevant to radioactive waste storage. Catalyst performance was evaluated using a custom offgas characterization system designed for near-zero flow conditions. The experimental apparatus consisted of a gas-tight 2.7 L PTFE vessel equipped with temperature monitoring, gas flow controls, and a variable-speed mixer to simulate sludge agitation. Offgas composition was monitored using a dedicated gas chromatograph with argon carrier gas and a krypton internal standard. Measurements were obtained for an empty vessel, the vessel containing a well characterized radioactive tank waste sample, and the same configuration with the candidate catalyst installed. Results demonstrate that the new catalyst effectively reduced hydrogen concentrations in the offgas within the constraints of the experimental design. In addition to confirming catalytic activity, the testing provided valuable insights into experimental optimization and considerations for future performance evaluations. These findings support the potential scalability of the technology and highlight its applicability to broader nuclear waste management operations, offering improved safety and reduced operational costs through enhanced catalyst durability and lower replacement frequency.

Tener, Zachary P. [Savannah River National Laborat↗
DOE OSTI2014

Technical Safety Requirements for the Waste Storage Facilities May 2014

This document contains the Technical Safety Requirements (TSR) for the Radioactive and Hazardous Waste Management (RHWM) WASTE STORAGE FACILITIES, which include Area 625 (A625) and the Building 693 (B693) Yard Area of the Decontamination and Waste Treatment Facility (DWTF) at LLNL. The TSRs constitute requirements for safe operation of the WASTE STORAGE FACILITIES. These TSRs are derived from the Documented Safety Analyses for the Waste Storage Facilities (DSA) (LLNL 2011). The analysis presented therein concluded that the WASTE STORAGE FACILITIES are low-chemical hazard, Hazard Category 2 non-reactor nuclear facilities. The TSRs consist primarily of inventory limits and controls to preserve the underlying assumptions in the hazard and accident analyses. Further, appropriate commitments to safety programs are presented in the administrative controls sections of the TSRs. The WASTE STORAGE FACILITIES are used by RHWM to handle and store hazardous waste, TRANSURANIC (TRU) WASTE, LOW-LEVEL WASTE (LLW), mixed waste, California combined waste, nonhazardous industrial waste, and conditionally accepted waste generated at LLNL as well as small amounts of waste from other DOE facilities, as described in the DSA. In addition, several minor treatments (e.g., size reduction and decontamination) are carried out in these facilities.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Decommissioning of a Historic Waste Storage Facility in Austria - 19059

Nuclear Engineering Seibersdorf Ltd. (NES) performed decommissioning of an old waste storage facility, the so called 'bunker', which was commissioned in 1968 and used until 1978 for the storage of radioactive waste from medical, industrial and research activities, as well as from the operation of the Austrian research reactor ASTRA. Due to the layout of the bunker the initial decommissioning plan was to decontaminate the inner walls of the caverns and afterwards perform clearance measurements on the standing structure. However, throughout the first phase of decommissioning it turned out, that contaminations penetrated deeper into the concrete structure as initially anticipated, which made an adoption of the decommissioning strategy necessary. By changing the workflow and to remove non-contaminated parts of the structure first, also the strategy for the clearance measurements had to be adapted. The selective decommissioning strategy and the demand that measurements shall be performed by an accredited body, required to set up an adequate communication structure to keep the workflow going. Moreover, a fast communication between NES, the competent authority and the authority's (external) experts was necessary to receive clearance licenses on time, and to prevent backlog of dismantled material. The paper reports on the initial and the adapted decommissioning strategy and the challenges within the changed approach. Applied decontamination and decommissioning methods and the implemented radiation protection measures will be discussed. Furthermore, information on the methodologies for clearance measurements, the collaboration of the accredited body with the decommissioning team, as well as on the communication between NES and the competent authority will be given. Finally, a balance of radioactive waste vs. conventionally disposed waste will be shown. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Radioactive Waste Storage Facility at the Armenian NPP - 12462

We present a detailed contaminant transfer dynamics model for radionuclide in geosphere and biosphere medium. The model describes the transport of radionuclides using full equation for the processes of advection, diffusion, decay and sorption. The overall objective is to establish, from a post-closure radiological safety point of view, whether it is practical to convert an existing radioactive waste storage facility at Armenian NPP, to a waste disposal facility. The calculation includes: - Data sources for: the operational waste-source term; options for refurbishment and completion of the waste storage facility as a waste disposal facility; the site and its environs; - Development of an assessment context for the safety assessment, and identification of waste treatment options; - A description of the conceptual and mathematical models, and results calculated for the base case scenario relating to the release of contaminants via the groundwater pathway and also precipitation especially important for this site. The results of the calculations showed that the peak individual dose is < 7 E-8 Sv/y arising principally from I-129 after 700 years post closure. Other significant radionuclides, in terms of their contribution to the total dose are I-129, Tc-99 and in little C-14 (U- 234 and Po-210 are not relevant). The study does not explore all issues that might be expected to be presented in a safety case for a near surface disposal facility it mainly focuses on post- closure dose impacts. Most emphasis has been placed on the development of scenarios and conceptual models rather than the presentation and analyses of results and confidence building (only deterministic results are presented). The calculations suggest that, from a perspective the conversion of the waste-storage facility is feasible such that all the predicted doses are well below internationally recognized targets, as well as provisional Armenian regulatory objectives. This conclusion applies to the disposal of the ANPP present and future arising of L/ILW operating wastes. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Case study in corporate memory recovery: Hanford tank farms miscellaneous underground waste storage tanks - 15344

In addition to managing the 177 underground waste storage tanks containing 212,000 m{sup 3} (56 million gal) of radioactive waste at the U. S. Department of Energy's Hanford Site 200 Area Tank Farms, Washington River Protection Solutions LLC is responsible for managing numerous small catch tanks and special surveillance facilities. These are collectively known as 'MUSTs' - Miscellaneous Underground Storage Tanks. The MUSTs typically collected drainage and flushes during waste transfer system piping changes; special surveillance facilities supported Tank Farm processes including post-World War II uranium recovery and later fission product recovery from tank wastes. Most were removed from service following deactivation of the single-shell tank system in 1980 and stabilized by pumping the remaining liquids from them. The MUSTs were isolated by blanking connecting transfer lines and adding weatherproofing to prevent rainwater entry. Over the next 30 years MUST operating records were dispersed into large electronic databases or transferred to the National Archives Regional Center in Seattle, Washington. During 2014 an effort to re-acquire the historical bases for the MUSTs' published waste volumes was undertaken. Corporate Memory Recovery from a variety of record sources allowed waste volumes to be initially determined for 21 MUSTs, and waste volumes to be adjusted for 37 others. Precursors and symptoms of Corporate Memory Loss were identified in the context of MUST records recovery. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

RCRA Part B Permit Application Nevada National Security Site (NNSS) for Waste Management Activities at the NNSS Mixed Waste Storage Unit (MWSU)

This volume of the Resource Conservation and Recovery Act (RCRA) permit application to the Nevada Division of Environmental Protection focuses on continued operation of the Mixed Waste Storage Unit at the Nevada National Security Site (NNSS), under the auspices of DOE’s National Nuclear Security Administration Nevada Field Office (NNSA/NFO). Low-level mixed waste (LLMW) accepted at the NNSS contains both radioactive and hazardous material components as defined by various laws and regulations. The Mixed Waste Storage Unit (MWSU) is located at the Area 5 Radioactive Waste Management Complex (RWMC). Existing facilities at the RWMC are used to store LLMW generated at or shipped to the NNSS prior to disposal at the Mixed Waste Disposal Unit (MWDU). The document describes the MWSU, its general design, its operation, the materials it stores, and relevant health and safety regulations with which NNSS complies. The currently permitted MWSU has been operated since December 2010. Each of the four designated storage areas is RCRA-compliant for the storage of hazardous waste. This application represents a renewal request by DOE for the permitted MWSU. For security reasons, some of the contents of the full application are not available for public viewing. This version of the application contains most but not all of the contents as submitted to the regulatory agencies.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Case Study in Corporate Memory Recovery: Hanford Tank Farms Miscellaneous Underground Waste Storage Tanks - 15344

In addition to managing the 177 underground waste storage tanks containing 212,000 m3 (56 million gal) of radioactive waste at the U. S. Department of Energy’s Hanford Site 200 Area Tank Farms, Washington River Protection Solutions LLC is responsible for managing numerous small catch tanks and special surveillance facilities. These are collectively known as “MUSTs” - Miscellaneous Underground Storage Tanks. The MUSTs typically collected drainage and flushes during waste transfer system piping changes; special surveillance facilities supported Tank Farm processes including post-World War II uranium recovery and later fission product recovery from tank wastes. Most were removed from service following deactivation of the single-shell tank system in 1980 and stabilized by pumping the remaining liquids from them. The MUSTs were isolated by blanking connecting transfer lines and adding weatherproofing to prevent rainwater entry. Over the next 30 years MUST operating records were dispersed into large electronic databases or transferred to the National Archives Regional Center in Seattle, Washington. During 2014 an effort to reacquire the historical bases for the MUSTs’ published waste volumes was undertaken. Corporate Memory Recovery from a variety of record sources allowed waste volumes to be initially determined for 21 MUSTs, and waste volumes to be adjusted for 37 others. Precursors and symptoms of Corporate Memory Loss were identified in the context of MUST records recovery.

Washenfelder, D. J.↗
DOE OSTI2024

Long-Term Performance of Reference Electrodes in Alkaline Radioactive Waste Storage Environments

Accurate measurements of corrosion potential are important for assessing the likelihood of internal localized corrosion and stress corrosion cracking of carbon steel tanks used for storing radioactive wastes. Reference electrodes in underground radioactive waste storage tanks are challenging to deploy, and more difficult to extract and replace frequently due to radiological exposure and disposal constraints. Hence, electrodes that exhibit stable performance over long periods of immersion in these waste environments are desirable. The present study evaluates the stability of reference electrodes used in radioactive waste storage tanks over a much longer period than previously studied. Long-term tests on Ag/AgCl and Hg/HgO reference electrodes were performed in nonradioactive simulants formulated from wastes stored at the Hanford site. Electrode degradation, which was studied by various in situ and ex situ evaluation techniques, was correlated to changes in electrode fill chemistry from waste intrusion via the porous frit junction. An intentional contamination study was performed to better understand and predict contamination effects on electrode potential drift.

Materials Science↗
DOE OSTI2015

RCRA Part B Permit Application Nevada National Security Site (NNSS) for Waste Management Activities at the NNSS Hazardous Waste Storage Unit (HWSU)

This volume of the permit application by the DOE’s National Nuclear Security Administration Nevada Field Office (NNSA/NFO) to the Nevada Division of Environmental Protection (NDEP) focuses on the Area 5 Hazardous Waste Storage Unit (HWSU). The HWSU was established to support testing, research, and remediation activities at the Nevada National Security Site (NNSS), a large-quantity generator of hazardous waste. The HWSU, located adjacent to the Area 5 Radioactive Waste Management Complex (RWMC), is a prefabricated, rigid steel-framed, roofed shelter used to store hazardous nonradioactive waste generated on the NNSS. No offsite-generated wastes are managed at the HWSU. Waste managed at the HWSU includes the following: Flammables/Combustibles, Acid Corrosives, Alkali Corrosives, Oxidizers/Reactives, Toxics/Poisons, and Other Regulated Materials (ORMs). A list of regulated waste codes accepted for storage at the HWSU is provided in this volume. Hazardous wastes are stored at the HWSU in containers that are compliant with U.S. Department of Transportation (DOT) regulations and compatible with the stored waste. Waste packages (e.g., drums) without inner closed containers of waste remain closed except during inspection or sampling. Transfer of uncontainerized waste between waste packages at the HWSU is prohibited. Closed inner containers may be transferred or consolidated into larger waste packages, and small closed containers may be placed into larger containers. Containers are stored on secondary containment pallets, and the unit is inspected monthly. For safety and security reasons, some of the contents of the full application are not available for public viewing. This public version of the application contains most, but not all, of the contents as submitted to the regulatory agencies.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Review of Mercury in the SRS Tank Waste Storage and Treatment Processes for Applicability to Hanford Waste Processing

The Savannah River Site (SRS) and Hanford produced large quantities of plutonium and other radioisotopes. The separations processes recovered plutonium and produced large quantities of High- Level Waste (HLW) that accumulated at each site in large, underground storage tanks. SRS has been retrieving the stored HLW, pretreating the waste for immobilization, and immobilizing the waste in glass or grout waste forms since the mid-1990s. Treatment of the waste at Hanford is expected to start in the early 2020s. Mercury is present in both the SRS and Hanford tank waste. SRS has recently completed an evaluation of mercury speciation throughout the tank waste treatment and immobilization flowsheet. This study was reviewed to determine what information from the study can be applied to the Hanford tank waste treatment program.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

LABORATORY TESTING TO SIMULATE VAPOR SPACE CORROSION IN RADIOACTIVE WASTE STORAGE TANKS

Radioactive liquid waste has been stored in underground carbon steel tanks for nearly 70 years at the Hanford nuclear facility. Vapor space corrosion of the tank walls has emerged as an ongoing challenge to overcome in maintaining the structural integrity of these tanks. The interaction between corrosive and inhibitor species in condensates/supernates on the tank wall above the liquid level, and their interaction with vapor phase constituents as the liquid evaporates from the tank wall influences the formation of corrosion products and the corrosion of the carbon steel. An effort is underway to gain an understanding of the mechanism of vapor space corrosion. Localized corrosion, in the form of pitting, is of particular interest in the vapor space. CPP testing was utilized to determine the susceptibility of the steel in a simulated vapor space environment. The tests also investigated the impact of ammonia gas in the vapor space area on the corrosion of the steel. Vapor space coupon tests were also performed to investigate the evolution of the corrosion products during longer term exposures. These tests were also conducted at vapor space ammonia levels of 50 and 550 ppm NH{sub 3} (0.005, and 0.055 vol.%) in air. Ammonia was shown to mitigate vapor space corrosion.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Refinement of Modeling Techniques for the Structural Evaluation of Hanford Single-Shell Nuclear Waste Storage Tanks

Abstract: A total of 149 tanks out of 177 at the Hanford Site (in Washington State, USA) belong to the first generation of underground nuclear waste storage tanks known as single shell tanks (SSTs). These tanks were constructed between 1943 and 1964 and are well beyond their design life. All the SSTs had been removed from active service by November 1980 and have been later interim stabilized by removing the pumpable liquids. The remaining waste in the tanks is in the form of salt cake and sludge awaiting r permanent disposal.. The evaluation of the structural integrity of these tanks is of utmost importance not only for the continued safe storage of the waste until waste retrieval and closure, but also to assure safe retrieval and closure operations. This article discusses the structural analysis approach, modeling challenges and issues encountered during the ongoing analysis of record (AOR) for evaluating the structural integrity of the SSTs. There are several geometrical and material nonlinearities and uncertainties to be dealt with while performing the modern finite element analysis of these tanks. Several studies were conducted to refine the models in order to minimize modeling artifacts introduced by soil arching, boundary effects, concrete cracking, and concrete-soil interface behavior. The analysis takes into account the temperature history of the tanks and allowable mechanical operating loads of these tanks for proper estimation of creep strains and thermal degradation of material properties. The loads imposed in the AOR models also include anticipated loads that these tanks may see during waste retrieval and closure. Due to uncertainty in a number of inputs to the models, sensitivity studies were conducted to address questions related to the boundary conditions to realistically or conservatively represent the influence of surrounding tanks in a tank farm, the influence of backfill excavation slope, the extent of backfill and the total extent of undisturbed soil surrounding the backfill. The article also discusses the criteria and design standards used for evaluating the structural integrity of these underground concrete tanks. Because of the non-availability of complete data on the thermal and operating history for many of the individual tanks, some of the data was assumed or interpolated. However, the models developed for the analysis of record represent the bounding scenarios and include the worst and extreme loading cases that the tanks were subjected to or anticipated. The modeling refinement techniques followed in the AOR resulted in conservative estimates for force and moment demands at various sections in the concrete tanks. The SSTs are classified into 4 types as per their configuration and capacity. This article discusses the modeling aspects related to two types of SSTs that have been analyzed until now. The TOLA results combined with seismic demands from seismic analysis for the analysis of record indicate that the tanks analyzed are structurally stable as per the evaluation criteria established. These results are presented in a separate article. The modeling techniques, methodology and evaluation criteria developed for evaluating the structural integrity of SSTs at Hanford are in general applicable to any similar tanks or underground concrete storage structures.

Single Shell Tank, Structural analysis, Structural↗
DOE OSTI2015

Bare Fiber Bragg Gratings embedded into concrete buffer Supercontainer concept for nuclear waste storage [ANIMMA--2015-IO-337]

Nuclear power plants have been generating electricity for more than 50 years. In Belgium, 55% of the current energy supply comes from nuclear power. Providing for the safe storage of nuclear waste, including spent fuel (SF) and vitrified high level radioactive waste (HLW), remains an important challenge in the life cycle of nuclear fuel. In this context, the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS) is investigating a reference conceptual design called the Supercontainer (SC) for the packaging of SF and HLW. This conceptual design is based on a multiple-barrier system consisting of a hermetically-sealed carbon steel overpack and a surrounding highly-alkaline concrete buffer. The first one is developed to retain the radionuclides. The two main functions of the buffer are (a) to create a high pH environment around the carbon steel overpack in order to passivate the metal surface and so to slow down the corrosion propagation during the thermal phase and (b) to provide a radiological shielding during the construction and the handling of the Supercontainer. A recent test has been performed to investigate the feasibility to construct the SC. This test incorporated several kinds of sensors including Digital Image Correlation (DIC), Acoustic Emission (AE), corrosion sensing techniques and optical fibers with and without fiber Bragg gratings (FBGs). In particular, several single-mode optical fibers with 4 mm long FBGs with different Bragg wavelengths and distributed along the optical fibers were used. For casting and curing condition monitoring, a number of gratings were incorporated inside the concrete buffer during the first stage of construction. Then other sensors were embedded near a heat source installed in the second stage to simulate the effects of heat generated by radioactive waste. The FBGs were designed to measure both temperature and strain effects in the concrete. To discriminate between these effects special packaging was used for some sensors that were installed very close to the unpackaged ones. Sensors placed in plastic tubes have reduced sensitivity to strain, while the ones inserted in metal tubes are only temperature sensitive and their readings can be directly compared with those obtained from thermocouples located nearby. In addition to monitoring temperature and strain behaviour, embedding also had as objective to determine the impact of the high alkaline environment on the silica fibers over a very long time. This article presents the preliminary results obtained with the different FBGs and provides recommendations for future improvement. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

Refinement of Modeling Techniques for the Structural Evaluation of Hanford Single-Shell Nuclear Waste Storage Tanks

ABSTRACT Several tanks at the Hanford Site (in Washington State, USA) belong to the first generation of underground nuclear waste storage tanks known as single shell tanks (SSTs). These tanks were constructed between 1943 and 1964 and are well beyond their design life. This article discusses the structural analysis approach and modeling challenges encountered during the ongoing analysis of record (AOR) for evaluating the structural integrity of the SSTs. There are several geometrical and material nonlinearities and uncertainties to be dealt with while performing the modern finite element analysis of these tanks. The analysis takes into account the temperature history of the tanks and allowable mechanical operating loads of these tanks for proper estimation of creep strains and thermal degradation of material properties. The loads prescribed in the AOR models also include anticipated loads that these tanks may see during waste retrieval and closure. Due to uncertainty in a number of inputs to the models, sensitivity studies were conducted to address questions related to the boundary conditions to realistically or conservatively represent the influence of surrounding tanks in a tank farm, the influence of backfill excavation slope, the extent of backfill and the total extent of undisturbed soil surrounding the backfill. Because of the limited availability of data on the thermal and operating history for many of the individual tanks, some of the data was assumed or interpolated. However, the models developed for the analysis of record represent the bounding scenarios and include the loading conditions that the tanks were subjected to or anticipated. The modeling refinement techniques followed in the AOR resulted in conservative estimates for force and moment demands at various sections in the concrete tanks. This article discusses the modeling aspects related to Type-II and Type-III SSTs. The modeling techniques, methodology and evaluation criteria developed for evaluating the structural integrity of SSTs at Hanford are in general applicable to any similar tanks or underground concrete storage structures.

Waste Managament, Single Shell Tanks, Structural E↗