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At least 397 records · Page 22
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DOE OSTI2016

Enhancing Fire Resiliency of Fixatives and Coatings for D and D Activities to Mitigate Potential Release of Radioisotopes during Fire and Extreme Heat Conditions - 16393

In discussions with officials from the Department of Energy's Office of Environmental Management and Savannah River National Laboratory (SRNL), the requirement for enhancing the operational performance of fixatives, coatings, and decontamination gels to better address the unique deactivation and decommissioning (D and D) challenges being faced by the SRS 235-F Project, and other high priority D and D efforts across the DOE Complex such as the Waste Isolation Pilot Plant (WIPP), has been identified as a priority focus area for research and development (R and D). Of particular interest is the immediate operational requirement to enhance a fixative's fire resiliency and survivability under fire and extreme heat conditions in order to mitigate the potential release of radioisotopes into the environment when subjected to these conditions. In support of the DOE-FIU Cooperative Agreement, under the Waste and D and D Engineering and Technology Development Project, Task 2: D and D Support for Technology Innovation, Development, Evaluation and Deployment, the FIU Applied Research Center (ARC), in close collaboration with SRNL, is leading the development, implementation, and execution of a phased effort to improve the operational effectiveness of fixative technologies in the critical areas highlighted above, and specifically focusing on enhancing fire resiliency without degrading fixing capacity or decontamination factor (DF). The research area being explored involves the analysis, laboratory experimentation, and testing of existing products, which through layering/combining with an intumescent coating, could possibly produce a synergistic effect, resulting in a new and improved process / material with characteristics that significantly improve operational performance in this area. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

AVANTech's Innovative LLW Concentrate Treatment System Reducing Environmental Releases - 16416

Russian Water-Water Energetic Reactors (VVER) and some Pressurized Water Reactors (PWR) utilize evaporator or reverse osmosis units to generate concentrate that must be disposed as LLRW. The new AVANTech Concentrate Treatment System (CTS{sup TM}) was developed to decontaminate the concentrate to the point where the dry solids after evaporation are free releasable to the environment and the radioactive waste generated represents less than 3% of the original concentrate volume, thus decreasing disposal costs substantially. These concentrate solids can be recycled to non-nuclear applications or disposed as industrial waste. Bench-scale testing has been completed with actual concentrate waste from two VVER plants with final results less than the IAEA General Safety Requirements (GSR) Part 3 discharge requirements. The VVER plants utilize chelants to conduct periodic decontamination of the piping systems that must be destroyed before utilizing precipitants and ion exchange to remove most of the isotopes. (authors)

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DOE OSTI2016

Liquid Waste Cell Decommissioning at the West Valley Demonstration Project - 16454

CH2M HILL BWXT West Valley, LLC (CHBWV) began decontamination and deactivation activities in the Liquid Waste Cell in the Main Plant Process Building (MPPB) at the West Valley Demonstration Project (WVDP) in 2013. The work is being done under CHBWV's Phase 1 Facility Disposition Contract with the U.S. Department of Energy, and is a prerequisite for demolition of the 3,716 square meter (40,000 square foot) MPPB, which is planned to begin in 2018. At the start of deactivation activities, the Liquid Waste Cell contained nine large contaminated vessels and approximately 1,220 meters (4,000 linear feet) of piping. Due to high levels of contamination and high radiation dose rates, frequent or prolonged manned entries into the cell were undesirable. CHBWV's strategy for preparing the cell for building demolition was based on conducting dose reduction and contamination stabilization activities using remotely deployed long-reach tools where possible, supported by manned entries where situations warrant or conditions were favorable. This paper discusses the conditions, challenges, decontamination approach, specialized tooling and expected end result of the Liquid Waste Cell deactivation project. (authors)

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DOE OSTI2016

Remediation of Occupied Commercial Property Subject to Widespread Radium-226 Contamination: Update from WM2012 Paper - 16652

Amec Foster Wheeler was contacted by a company that managed commercial office space. High Rn-222 measurements had been observed throughout the facility and the landlord had been advised to commission a radiological survey of the site. The site had been purchased by the client in the 1990's. Initial desk studies found that the building had operated for around 50 years as a compass factory. Non-intrusive investigation identified widespread Ra-226 contamination. Ra-226 was found in the fabric of the building, in attic spaces, buried under floor boards and underlying car parks. Intrusive investigation was undertaken to estimate volume(s) of waste, waste categories, activity concentrations and the total inventory of radioactive materials on site. This work identified the presence of 180 GBq of Ra-226 on site. A programme of work is currently underway to remediate the site tackling areas posing the greatest risk to site occupants as a priority. We have worked closely with Regulators, our client, and tenants, to decontaminate the fabric of the building whilst areas of the building remain occupied. Early decontamination works identified that radon levels within the building were stubbornly high despite the removal of radium contamination. An independent radon source was suspected. A contaminated drain was discovered leading to a blocked-off river race running under the old mill building. A significant quantity of radium contaminated sludge was identified within the river race. This was believed to be the source of the excessive radon concentrations within the building. The paper will present work undertaken to investigate and remediate the inventory of sludge from beneath the building. It will describe the operational difficulties of working within a dynamic environment impacted by high dose rates, high radon concentrations, water ingress and waste retrieval challenges. The paper will present the radiological and environmental impacts of the work and detail the achieved end points. This was a challenging project working in confined spaces impacted by physical and radiological constraints. The remedial action undertaken significantly reduced radon concentrations in the building metres above the river race. It also significantly reduced the likelihood of radium contamination being mobilised into the river and the wider environment. The achieved end point permitted the building to return to uncontrolled commercial use. The end point achieved within the river race will ensure a safe working environment for future regular structural survey work. (authors)

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DOE OSTI2018

Preliminary Planning of Radwaste Management for the Decommissioning of Chinshan NPP in Taiwan - 18201

The Chinshan NPP was the first commercially operated nuclear power plant in Taiwan since 1978. There are two BWR units in Chinshan NPP, which each unit has electrical output of 636 MWe. After 40 year's period of license, the final shutdown date of Unit No. 1 and Unit No. 2 will be in December, 2018 and in July, 2019, respectively. According to 'Nuclear Reactor Facilities Regulation Act' in Taiwan, decommissioning of nuclear reactor facilities should be implemented by the strategy of DECON (Decontamination followed by dismantling) within 25 years when the permission is approved by Atomic Energy Council (AEC). The decommissioning plan of Chinshan NPP has been permitted by AEC in the end of June, 2017. The implementation of Chinshan NPP decommissioning will be started while the Environmental Impact Assessment is approved by EPA. In this study, the Turbine Building in Chinshan NPP is selected as a case study for the preliminary planning of decommissioning. First, we thoroughly examine the inventory of all macro-components in the Turbine Building to estimate the waste amounts. Accordingly, the work breakdown structure (WBS) for dismantling of facilities is scheduled. Then, considering to minimize waste amounts, several suitable decontamination techniques, such as chemical and mechanical methods, which are developed by INER are considered to be adopted. As for the estimation of man hours of dismantling facilities, all events during the decommissioning tasks are classified into 16 work procedures and appropriative factors of corresponding team hours are gotten. In addition, the detailed methodology of the preliminary plan of decommissioning is also discussed. Finally, we hope the results of this planning can provide practical benefits to upcoming decommissioning work in Taiwan. (authors)

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DOE OSTI2018

Interactions of Chemical Contaminants to Steel and Concrete Via Spectroscopic and Computational Methods - 18398

There is limited understanding of the scientific interaction of the chemical contaminants to DOE facility materials which can alter the stability of the materials, and in turn, affecting the general safety. In addition, the materials themselves can be considered secondary waste and decontamination is necessary. Therefore, the overall goal of this project is to determine the physiochemical interactions of Hg and Cs to steel and concrete using spectroscopic, adsorption and computational studies. To achieve the overall goal, this proposal has the following objectives: 1) Evaluate the physicochemical interactions of Hg and Cs to steel and concrete using spectroscopic techniques under standard conditions and 2) Evaluate the impact of environmental conditions (temp., salt content, pH, and time) on the physicochemical interactions of Hg and Cs to steel and concrete using spectroscopic techniques. Less labor intensive than traditional wet chemical analyses, spectroscopic methods have the advantage of elucidating both structural and chemical changes at the micro to nano-scale. The potential impacts of the proposed work could lead to cost effective decontamination methods, minimize secondary waste, and reduce worker exposure. (authors)

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DOE OSTI2018

Integrating Multiscale Datasets for Monitoring Air Dose Rates in Fukushima - 18437

Six years has passed since the radionuclide release occurred at the Fukushima Daiichi NPP. Measurements and monitoring of air dose rates (i.e., ambient dose equivalent rates) in the region around the Fukushima Daiichi NPP have been performed continuously since the accident. Such mapping efforts are essential to protect the public, to guide decontamination efforts, and to plan the return of evacuated residents. An extensive monitoring program has enabled to develop a data-driven environmental decay model for describing and predicting the decay of radiation air dose rates in the environment. However, it has been difficult to quantify the heterogeneity of environmental decay in the regional scale, since spatially extensive airborne survey datasets often have discrepancy with the ground-based measurements and have a larger uncertainty. Recently, a Bayesian hierarchical modeling approach was developed to integrate multiscale datasets (i.e., car, walk and airborne surveys), and also to estimate the spatial distribution of air dose rates in high resolution over space. The integrated air dose rate maps have been contributed to planning of the future decontamination and resident's return as well as associated cost. In this study, we aim to extend this approach and predict the area of the evacuation zone in the future. WE coupled the integrated map with the data-driven ecological decay model. Results show that the area of vacuation zone (i.e., the area above 3.8 micro-Sv/yr) will shrink significantly in the next twenty years, and it will be fully contained in the non-residential forested area by 2040. (authors)

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DOE OSTI2018

Innovative Decommissioning Strategies for Large Components - 18535

Within decommissioning projects the dismantling of steam generators as well as of the reactor pressure vessel with its internals form important and time consuming tasks. In order to optimize these, the reactor pressure vessel will be segmented into larger pieces in-situ and the larger pieces will be further segmented in a post segmentation area in order to suit the dimensional and radiological requirements of the final waste package. A similar approach is used also for the dismantling of Steam Generators. NUKEM Technologies Engineering Services has combined the two principles 'Rip / Store / Ship' and 'In-situ segmentation' to firstly segment the steam generator in-situ and then pack and ship all resulting parts allowing decontamination within 20' container to an existing decontamination facility. The aim is to free release 90 - 95% of the material. (authors)

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DOE OSTI2016

C-400 and C-409 Criticality Incredible Road Map

Many guides and standards describe a process for evaluating process operations with known quantities of fissile material. The accepted industry guides and standards for performing criticality evaluations for fissile material operations are not well suited for operating systems that may contain residual fissile material. The Paducah Site deactivation activities includes large process components that have unfavorable geometries for the {sup 235}U enrichment levels present. The fissile material holdup in these components can range from negligible residual quantities to significant deposits weighing several hundred pounds. The purpose of this white paper is to outline a methodology that can be used to declare a facility as criticality incredible (CI). For the purpose of this paper, criticality incredible means that the inventory and its form and distribution within the facility does not need Nuclear Criticality Safety Evaluation (NCSE) type (e.g., administrative or engineered) controls. This assumes of course that certain project assumptions are maintained. For example in the facilities that will be discussed within this paper, wet decontamination is not part of the planned demolition and disposal operations. The proposed methodology for deactivation of a facility to the point that criticality incredible can be declared will be applied to the C-400 Chemical Cleaning Building and to the C-409 Decontamination Facility at the Paducah Gaseous Diffusion Plant (PGDP). The purpose and intent of the CI declaration is to release a facility from Nuclear Criticality Safety (NCS) requirements and simplify the demolition of the facility. In practical terms, this means the facility can be re-categorized as < a Hazard Category 3 facility per DOE-STD-1027-92 Hazard Categorization and Accident Analysis Techniques for compliance with DOE Order 5480.23, Nuclear Safety Analysis Reports, NCS controls are not needed, and the Criticality Accident Alarm Systems (CAAS) can be removed from service. The only involvement from the site NCS program following the declaration would be to ensure that the underlying assumptions are not violated through discovered conditions or project changes. This includes the institutional control of preventing new fissile material from being introduced into the facility. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Solving Operational Challenges with INL's Integrated Waste Treatment Unit (IWTU) - 19003

In 2005, the THOR steam reforming fluidized-bed reactor technology was selected by the U.S. Department of Energy for treatment of sodium-bearing waste at the INL. The initial commissioning was typical, until June of 2012 when an over-pressurization event resulted in a significant release of solids. Recovery and subsequent testing systematically dealt with challenges associated with operation of three primary vessels: the denitration and mineralization reformer, the process gas filter, and the carbon reduction reformer. Additional challenges with the following ancillary systems surfaced during testing: the auger/grinder, sample system, and the approach to decontamination of the process vessels prior to outages. The major operational challenges covered fluidization issues, premature refractory failure, high-temperature gaseous filter element blinding, cementitious material formation in solids handling equipment, sampling reliability, and vessel decontamination. The purpose of this paper is to share the lessons learned during the extended commissioning of the Integrated Waste Treatment Unit. (authors)

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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 OSTI2019

Decommissioning Status and Preliminary Engineering Planning for Chinshan NPP in Taiwan - 19114

The Chinshan Nuclear Power Plant, which consists of two BWR units and was owned by Taiwan Power Company (TPC), has an electrical output of 636 MWe for each unit. Unit No. 1 and Unit No. 2 were licensed till December 2018 and July 2019, respectively. According to regulations of decommissioning in Taiwan, decontamination and dismantling of a NPP should be completed within 25 years. Therefore, TPC had started compiling the decommissioning plans (DP, 17 chapters) with INER, national engineering companies and international consultants since 2012. The DP of Chinshan NPP has been approved by the regulator, Atomic Energy Council (AEC), in the end of June, 2017. There are 17 chapters in the decommissioning plans, which deal with all aspects of safety-related considerations during the decommissioning period, such as spent fuel management, waste management, personnel/workers planning, schedules/working items, environmental management and monitoring. Those items are discussed in detail in this paper in accordance with the approved DP. The implementation of decommissioning will be started while the Environmental Impact Assessment (EIA) is still under approval by EPA, which is expected to be completed in the end of 2018 or the mid of 2019. Once the decommissioning be started, all dismantling, decontamination, management teams, and preparation would be kicked off simultaneously in a very short period of time. In this paper, the planning assumptions, strategies from INER and TPC, management of radioactive waste, conversion of Turbine Building and detailed description of turbine-generator set are discussed. For the Turbine Building dismantling, inventories of equipment, cutting technology determination, storage logistics, container options and radwaste treatment and reduction would be important factors to be evaluated in the beginning. Afterwards, WBS (work breakdown structure) would be determined and be the basis for working bids, construction of a new storage warehouse, an incinerator and a super high pressure compactor. This preliminary engineering planning would be applied in the decommissioning of Chinshan NPP for the first time and be duplicated in Kuosheng NPP and Maanshan NPP in Taiwan as well. (authors)

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DOE OSTI2019

Measurement Concept for a Possible Clearance of Mercury Waste from Nuclear Facilities - 19138

This paper describes the development of a measurement concept for a clearance of mercury waste from the decommissioning of nuclear facilities. A decontamination of mercury is performed after which large parts of the waste could possibly be released into reuse or conventional mercury disposal. The focus of this work is on the development and validation of a gamma-spectrometric measurement setup that is used for decision-making measurements for a possible clearance procedure. The measurement system is validated by a comparison of experimental measurements with nuclear simulations using Monte Carlo N-Particle{sup R} Transport Code (MCNP{sup R}). The validated MCNP{sup R} simulation model is used to determine the energy-dependent photopeak efficiencies and subsequently the sensitivity of the measurements. Preliminary results of gamma spectrometry in combination with MCNP{sup R} simulations indicate that a clearance of elemental mercury should be possible after decontamination. (authors)

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

Rad Waste Cost/Volume Reduction Using New Monitoring/Decon Techniques, Launderable Items and Recycling - 19297

The use of improved radiation monitoring and decontamination techniques significantly reduces the cost and volume of Canadian radioactive waste via recycling/reuse. Over 2,700 metric tons of scaffolding and tooling have been released for unrestricted use back to the owners or recycled as non-radioactive scrap metal over the last 10 years. Additionally, using reusable launderable items reduces the cost over single use Radiological Personal Protective Equipment (RPPE) and plastic wraps and has eliminated thousands of cubic meters of Canadian station waste each year for over 10 years. The combined effect is the significant volume reduction of radioactive waste in a low risk, cost effective, manner. This paper and presentation will highlight the processes and showcase the types of materials decontaminated. The intent is to make waste generators aware of new processes that could be applied to the waste materials stored in their vaults or generated during a refurbishment/decommissioning project as well as day-to-day power generation operations. (authors)

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DOE OSTI2019

Comparing Ecological Risk between D and D Facilities and Operating Facilities at the Hanford Site - 19531

Many countries are faced with a large remediation task resulting from World War II, the Cold War, and subsequent industrial development. In the U.S. the Department of Energy (DOE) faces the largest hazardous waste remediation tasks, with a commitment to protect human health and the environment during and following remediation. DoE's biggest challenge is remediation of the many remaining cleanup areas at the Hanford Site, Washington. Some Hanford sites have extensive ecological resources and ecosystems that require protection or restoration. We briefly 1) describe a rapid evaluation method for ecological resources on units slated for cleanup that allows comparison among the different areas at the Hanford Site, 2) examine some D4 (deactivation, decommissioning, decontamination and demolition) facilities and Operating facilities that require remediation, 3) describe potential ecological harm to resources on these sites, and 4) compare how risks from potential harm vary at the Hanford Site. The ecological evaluation includes three phases: 1) general steps (identify resource categories, identify cleanup areas), 2) ecological descriptions (describe resources on the site to be cleaned up), and 3) ecological ratings (rate the value of the resources on a scale that can be applied across remediation sites). After completion of these steps for the sites requiring cleanup, a comparison of potential risks can be made among types of facilities (e.g. D4 facilities, legacy waste sites, operating facilities). D4 facilities are those slated for deactivation, decommissioning, decontamination and demolition, while operating facilities at Hanford include waste treatment plants, sludge basins, waste trenches, Central Waste Complex, storage facilities, and disposal facilities, among others required to support the D4 and other remediation activities, before they too are remediated. Currently the potential harm to ecological (and eco-cultural) resources on the Hanford Site for remediation at D4 facilities is very low, but increases to very high (for reactors) during remediation when there is physical disruption, increased traffic and personnel, and possible increased contamination. Following remediation, the potential harm to ecological resources is low, and the value may increase due to restoration of native vegetation on sites that were largely industrial prior to remediation. In contrast, the potential harm to ecological resources at Operating Facilities was higher currently than for D4 facilities, but was low to medium following cleanup. The higher harm (risk) at D4 facilities partly derives from the location of the reactors near the Columbia River, a resource extremely important to Tribal Nations and to other peoples in the Northwestern United States, as well as for the iconic and threatened salmon populations. Methods described in this paper provide Congress, DOE managers, regulators, Tribes, and the general public with assurance that ecological and eco-cultural resources and the environment are being protected during and following remediation. The analysis of specific sites provides managers, regulators and the public with information to make cost-effective decisions about remediation that continues to enhance ecological value while protecting human health. (authors)

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DOE OSTI2019

Transport and Treatment of Chapelcross Gas Ducts for Clearance and Recycling - 19662

In the summer of 2018, Cyclife, the EDF group's specialist radioactive waste management and decommissioning company, transported sixteen gas ducts and associated equipment from the shutdown Chapelcross nuclear power plant to treatment facilities in the UK and Sweden. The client requested a full removal, treatment and disposal service for approximately 820 te of low level metallic waste comprising Upper Gas Duct Assemblies (including bellows), Upper Gas Duct elbows, Filter Pots and Convoluted pipework. The complex scope involved heavy lifting, transport by road and sea, processing and recycling on a large scale, thereby necessitating involvement of a wide range of suppliers at different tiers all managed by Cyclife. The purpose of the entire project was to safely handle and treat all of the components for clearance and recycling into the public domain for the manufacture of new steel products. Most of the treatment took place in Cyclife's nuclear licensed metal treatment facility in Sweden. Cyclife has a long and unique experience of arranging safe transport of large contaminated components on road and sea. The metal treatment facility in Sweden can, without special arrangements, receive components up to 30 meters long with a weight of up to 400 tonnes for decontamination, size reduction and melting. The actual treatment of the components consisted of the following steps: a) Separation of a gas duct from the gantry, b) size reduction, radiological verification measurements and clearance of the gantry, c) stepwise segmentation of the gas duct and elbow including removal of asbestos, d) decontamination, e) melting, f) radiological assessment and clearance of the metal ingots, g) management of the secondary waste for return to UK. The result of the project, upon completed treatment of all the material, demonstrates a high recycling rate of the material. 5-10% of the original mass of material will have to disposed as radioactive waste. This number include all residues, untreatable material (asbestos, mineral wool, filters etc.) and two melt batches with a too high activity content for clearance. The paper takes the reader through the entire project from the initial planning to the clearance of the metal and the return of the secondary waste to UK for disposal. It will also present and discuss pros and cons for alternative management approaches in several perspectives. (authors)

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DOE OSTI2020

Certifying the Performance of Fixative Technologies under Open Air Demolition Activities for D and D - 20096

Department of Energy (DOE) facilities undergoing deactivation and decommissioning (D and D) activities struggle with safety concerns of residual radioactive contamination leftover after gross decontamination efforts have concluded. The positive effects of implementing fixative technologies for decommissioning and maintenance is known across the DOE complex. However, there is no standardized metric in place that quantifies the performance of these technologies such as incombustible fixative platforms that immobilize the contamination in a solid polymer material under normal operating conditions or when exposed to stressors. The primary focus of this research is to provide the empirical data necessary to properly characterize the effects of implementing fixative technologies on mitigating the release of contamination. In addition, this effort has been used to identify and establish uniform testing protocols to quantify operational parameters of fixating platforms and properly credit such systems under a variety of operational conditions and stressors that can arise during open air demolition efforts (e.g. impact, water, thermal, etc.). The established protocols will be provided to the ASTM International E10.03 Subcommittee on Radiological Protection for Decontamination and Decommissioning of Nuclear Facilities and Components for the potential of formal standardization. Attributes to be addressed during testing are material compromise from impact stress, thermal stress for incombustible fixative materials, and immobilization factors (how well an immobilizing platform is capable of retaining fixated material during thermal and impact stressors). In developing these test methods, a greater understanding of the material's behavior under anticipated and unanticipated events, such as decommissioning activities and contingency events as outlined in the Basis of Interim Operations (BIO), can be successfully characterized. There are several key components of the experimental methodology that is essential in empirically certifying fixative technologies. A surrogate contaminant with a unique signature has been utilized with the implementation of a uniform contamination process of test coupons that is quantifiable and replicable for direct fixative comparisons. A modular test chamber has also been used to apply the various stressors of interest. Collection of released contamination that includes airborne and resettled contaminant particles and analyzed using mass spectrometry. This research directly supports DOE complex-wide concerns in terms of final disposition of nuclear facilities and the considerations made during their time between ceasing facility operation and final disposition. The results of this effort aims to provide a standardized road map and logical decision flow to better facilitate fixative technologies into D and D activities required to achieve the desired facility end state. (authors)

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DOE OSTI2020

The TRANSCEND University Consortium: Theme 2 - Site Decommissioning, Deconstruction and Remediation - 20329

This paper will discuss the aims, objectives and progress to-date under Theme 2 of the TRANSCEND consortium project: Site decommissioning, deconstruction and remediation. Decommissioning nuclear sites involves waste retrieval, decontamination, deconstruction and, where necessary, containment and/or remediation of the remaining structure and surrounding land. Critical to management of these processes is limiting radiation exposure for the workforce, restricting the spread of radionuclides in groundwater, surface water and airborne particulates, and minimising the volume of contaminated waste for disposal. The aim of Theme 2 research is to develop new technologies for monitoring, remediation and containment that serve to minimise the volume of radioactively contaminated waste for disposal, for application prior to, during and after retrieval, deconstruction and decontamination operations. Prior research, conducted under the previous DISTINCTIVE project, demonstrated that colloidal silica grout can penetrate low permeability materials (including cement) for hydraulic barrier formation, and improved sorption capacity. The silica grout can be injected at surface using extremely small (potentially gravity-driven) fluid pressures, without the need for borehole drilling. Current work is investigating the erodibility of silica-grouted soils for inhibition of airborne and water-borne particulates as well as enhancing the grout's sorption capacity by addition of other materials to provide a chemical, as well as hydraulic, barrier to subsurface migration. EK remediation uses low voltage DC current to control migration of contaminants in porous media as well as to remove or degrade them. Researchers in the consortium have already demonstrated that low-energy ex-situ EK techniques can be used to provide remediation and volume minimisation for AWE legacy wastes in the UK. Under the current project researchers are building EK test cells containing simulated site materials at laboratory and intermediate(m)-scales to: remove, focus or degrade contaminants (remediation or waste minimisation); and direct subsurface water, chemical and colloid flow (fencing/containment or forced migration). This lab-based research is being informed by numerical models of EK processes that can subsequently be used to design full-scale on-site applications by nuclear site holders. Research under theme 2 of TRANSCEND will ultimately combine novel non-invasive detection technologies with EK techniques and colloidal silica grout barriers, to optimise the containment of radionuclide contamination in soils. Thus, allowing us to detect in-situ contamination, mobilise it to a selected location and grout it in-situ, prior to the initiation of decommissioning and deconstruction operations. (authors)

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