Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Waste management”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Long history of Cl-36 Assessment of Graphite Waste by EDF Engineering and the Latest Suggested Developments - 17043

Prior to 2005, the EDF initial version for the radiological inventory of graphite was based on the maximum values of the measures, namely a very pessimistic way. In 2008, a scientific method was developed by EDF to evaluate the inventory by reverse activation calculation, in order to limit the overestimation. The radiological inventory computation principles can be compared to those of all engineering studies. First, the calculation is simplified by taking margins, and if the results are not satisfactory enough, some simplifications are suppressed to reduce these margins even if computation becomes more complicated. On EDF piles, the gain obtained in 2008 represented a factor 50 relative to the initial version of Cl-36, even with a very penalizing multiplicative factor for uncertainty. Today, the accurate calculation of the uncertainty no longer justifies such a factor. A gain of about 150 now occurs compared to the initial version of Cl-36. It is more than 2 orders of magnitude, which is already enough to assess again the necessary type of disposal because Cl-36 is one of the key radionuclides. After global presentation of graphite waste management in France, the paper focuses on the inventory scientific process of EDF nuclear graphite, the purity of graphite and its consequences, its particular sampling, the lessons learned, the initial method description, the link with the demonstration of the completely random point process of chlorine in nuclear graphite and the last suggested precise uncertainty computation of inventory of Cl-36. The method confirmation for concentration assessment, the history of the EDF method development and its benefits are also emphasized. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Stakeholder Involvement in the Revegetation of the 92-Acre Area - 17152

The U.S. Department of Energy, National Nuclear Security Administration Nevada Field Office (NNSA/NFO) works closely with stakeholders that have an interest in the revegetation of a closed landfill on the Nevada National Security Site (NNSS). Located at the Radioactive Waste Management Complex on the NNSS, the 92-Acre Area was operational from 1961 to 2010. In 2009, the Nevada Division of Environmental Protection (NDEP) and NNSA/NFO agreed on a closure path consisting of a vegetative cover. Closure activities were initially completed in 2012. Although revegetation was initially promising, subsequent monitoring revealed that a viable plant community had not been established. Subsequently, sections of the site were chosen as test plot locations to determine the best path forward. Despite various seeding methods, mulching techniques, and irrigation frequencies, the test plots failed to produce viable plant communities in 2013 and 2014. NNSA/NFO had been in communication with one stakeholder, NDEP, during the revegetation process. NDEP agreed that after three failed revegetation attempts, a change in strategy was necessary. The Consolidated Group of Tribes and Organizations (CGTO), a coalition of tribal members representing seventeen culturally affiliated tribes and one organization, agreed to provide guidance using traditional ecological knowledge for re-vegetating the 92-Acre Area. A Tribal Revegetation Committee (TRC) was formed and tasked with developing guidance from a unique tribal perspective. After visiting the 92-Acre Area and receiving background information, the TRC held several meetings and deliberated on how to address the revegetation challenges. The TRC submitted recommendations to NNSA/NFO identifying approaches that incorporate tribal perspectives in re-vegetating the site. The Nevada Site-Specific Advisory Board (NSSAB), which is made up of community members who represent Nevada stakeholders, was also asked for input regarding the 92-Acre Area. After a public meeting in May 2016, the NSSAB submitted recommendations, which included a suggestion to consider input from the CGTO. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Improving Decommissioning Success using the Tool of Virtual Reality; Increasing Worker Safety and Project Schedule Stability - 17193

operations, especially underwater, is essential. Equally essential is a precise game plan for disassembly which focuses attention on the skilled remote handling operators who must produce the results. Project success is based on clean, efficient cuts and take-aways, prepared paths for waste placement and containment, programmed return paths; and practice, practice, practice on the part of the operators. Recently, our Partner, WAK Ruackbau- und Entsorgungs- GmbH (Decommissioning and Waste Management Company) was tasked with dismantling and decommissioning the Karlsruhe Reprocessing Plant. The most difficult task in this project is the dismantling of the vitrification plant. Waelischmiller was selected to address this high-consequence project. Together, WAK and Waelischmiller determined that development of a virtual reality suite, where management and operators could create a virtual vitrification layout and subsequently map and rehearse their dismantling plan was essential. This approach, using Virtual Reality (VR) as a tool in streamlining operations and rehearsing difficult moves and cuts, will be a game changer for this and future projects. It will be a first-of-a-kind in Germany. The VR suite is contained in a room at the Karlsruhe facility with a large screen, control cabinet, simulation computer, a Waelischmiller Joyarm and Masterarm. To support the dismantling of the vitrification plant, WAK/HWM will conduct interactive feasibility studies for each dismantling step. All movements; cuts, take-aways and vessel segment insertion into transportation and disposal casks will be established, programed and practiced within virtual test suite. This allows savings in cost-intensive and complex construction of test rigs. Operating personnel can be trained in the VR suite, without taking the risk of damaging expensive remote handling equipment.While the operators are working on the operating element, they stand in front of a wide screen. Instead of a real TELBOT{sup R}, a virtual TELBOT{sup R} is moving on the screen in virtual reality. While practicing, the operators cannot damage the arm and the equipment, which is a big advantage. Moreover an interactive feasibility study can be realized without building a real test rig (mock-up). Consequently significant cost-expenses can be reduced. This paper will describe the virtual suite used by the WAK in Karlsruhe and the advantages of this new and innovative approach, which is unique in decommissioning of nuclear facilities. The viewpoint of each (WAK and HWM), and the decisions and benefits realized along the project path will be detailed in the paper. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Ecological Resource Value, Remediation Options, and Impacts: Functional Remediation at Hanford Site - 17226

Governmental agencies, Tribes, regulators, resource trustees and other stakeholders are interested in understanding the risk to the environment from remediation and restoration, particularly at large DOE sites with complex remediation tasks lasting decades. While each remediation project has the usual environmental impact assessment that include risk to eco-receptors, a piece-meal approach to examining the effect of remediation does not provide an overview of remaining tasks that would aid in sequencing these tasks. The Consortium for Risk Evaluation with Stakeholder Participation (CRESP) developed a risk methodology for Hanford Site that included ecological resources between 2014 and 2015. The ecological methodology included a comparison of the value of on-site resources with the eco-region, with state and federal threatened and endangered species, and with rare and unique habitats. Potential remediation options for particular evaluation units were used in conjunction with the resource level values to determine the risk of remediation of ecological resources. The methodology developed for Hanford Site also considered functional remediation (e.g. number of trucks, personnel, heavy equipment), initiating events (e.g. earthquakes, volcanos) and future land use. These factors were combined to rate the risk to ecological resources on a scale of not-discernible to very high. In this paper seven evaluation units (waste sites requiring remediation) were evaluated to explore the efficacy of the methodology to provide useful information on the comparative risk for decommissioning and waste management sites. The evaluation of resource levels was based on prior site information, state and federal data bases, and field investigations. The final determination of a risk rating for each evaluation unit depended upon both quantitative data, field experience, and professional judgement. It provides a method that can be applied to many remediation sites within a large DOE facility such as Hanford, as well as across the DOE complex. This will provide information for sound decision-making with stakeholder participation, and will allow DOE to reassure stakeholders that they are protecting human and ecological health on the Hanford Site. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Upfront Update on Barsebaeck 1-2 Reactor Internals Segmentation Project - 17382

Westinghouse is currently executing a contract, awarded in June 2015 from Barsebaeck Kraft AB, to segment all the reactor vessel (RV) internal parts in the two units 1 and 2. The scope of work covers the dismantling and segmentation of the RV internals under water, including the upfront engineering studies and equipment manufacturing and qualification. It also includes the loading of the segmented parts into waste cassettes, handling the cassettes, reactor internals sampling (73 samples), complementary water filtration system to catch the segmentation chips and contribute to maintaining water clarity during the segmentation work. Before leaving the site, the pool environment must be restored to the initial condition and all equipment will be decontaminated and shipped off site. The site work started in August 2016 with the mobilization on the Unit 2 and the actual cutting of the first component (steam dryer) started in September. Cutting will be performed with different types of Westinghouse designed cutting equipment. This paper presents the conceptual design of the reactor internals segmentation and packaging process that will be implemented at Barsebaeck, including the planning, methodology, equipment, waste management and packaging strategy. A first feedback on the site work will be provided for the segmentation of the Unit 2 reactor internals. (authors)

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

National contribution to the organization and carrying out monitoring activities on assessment of radiation and ecological situation in uranium tailings of SE 'Vostokredmet' - 15068

In this paper, the legislation governing radiation safety and radioactive waste management in Tajikistan is described. The role and responsibilities of both the regulator and the user as they apply to the remediation of legacy sites are presented, as is the infrastructure for the monitoring of legacy sites. The challenges presented by radiological contamination in Tajikistan and Central Asia are discussed. National and regional commitments with respect to legacy sites remediation in Tajikistan are described. (authors)

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

Uncertainty in decommissioning, the benefits of 3D simulation - 15124

Any industrial plant whatever the industry is will face its end of life. In the nuclear field decommissioning is inevitable for returning to green. Because of the specificity of each plant, decommissioning projects are never the same. The choice of a specific strategy for each operation during a scenario has cascade consequences on the generated waste, extension of due date, costs and risks. Decommissioning in nuclear industry is a new domain where countries have a limited experience. When starting a decommissioning project engineers have to gather some data needed for planning and realizing the best scenario strategy. Scenario which should consider the costs, waste management, received dose and the planning. The quality of the input data has a strong influence on the risks and should be analyzed with care to reduce all doubts for the study. Nuclear plants running decommissioning programs concerns old plants with poorly documented history resulting in missing or uncertain data. The ambient dose rate is not always well-known as dose measurement or samples have not been taken or updated for many years. This kind of data may vary quite a lot when radiological events happen. An efficient way to reduce contingencies is to go through simulations. It allows determining the best scenario strategy for each set of data while evaluating the influence of all uncertainties. (authors)

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

Evaluation of waste arising from future nuclear fuel cycle - 15197

A comprehensive study was recently completed at the request of the US Department of Energy Office of Nuclear Energy (DOE-NE) to evaluate and screen nuclear fuel cycles. The final report was issued in October 2014. Uranium- and thorium-based fuel cycles were evaluated using both fast and thermal spectrum reactors. Once-through, limited-recycle, and continuous-recycle cases were considered. This study used nine evaluation criteria to identify promising fuel cycles. Nuclear waste management was one of the nine evaluation criteria. The waste generation criterion from this study is discussed herein. The fundamental characteristics of nuclear fuel cycles were used to create a comprehensive set of fuel cycle options. These options were categorized into 40 Evaluation Groups based on similarities in their physics-based performance. These Evaluation Groups, listed below, comprehensively represent all fuel cycle options: - 8 once-through Evaluation Groups: 5 uranium-based fuel cycles and 3 thorium-based fuel cycles - 10 limited-recycle Evaluation Groups: 6 uranium-based fuel cycles and 4 thorium-based fuel cycles, and - 22 continuous-recycle Evaluation Groups: 14 uranium-based fuel cycles and 8 thorium-based fuel cycles. The study focused on the quantity and characteristics of radioactive wastes generated by the different fuel cycles, examining 5 metrics characterizing waste generation: - mass of spent nuclear fuel (SNF) plus high level waste (HLW) disposed per energy generated, - activity of SNF + HLW (at 100 years) per energy generated, - activity of SNF + HLW (at 100,000 years) per energy generated, - mass of depleted uranium (DU) + recovered uranium (RU) + recovered thorium (RTh) disposed per energy generated, and - volume of low level radioactive waste (LLW) per energy generated. (authors)

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

Portland cement paste behaviour under gamma radiation field in geological repository - 15272

The Radioactive Waste Management Laboratory at the Nuclear and Energy Research Institute in Sao Paulo, Brazil (IPEN-CNEN-SP), is developing the concept of a repository for disposition of disused sealed radioactive sources in a deep borehole in which cement paste is intended to be used as a backfill between the steel casing and the geological formation around the borehole. The cement paste is intended to function as structural material, a blockage against the transport of water between the different strata of the geological setting, and as an additional barrier against the migration of radionuclides. The assessment of the cement paste behaviour in long term is necessary to increase the confidence that the material will perform as required during the service life of the facility. Under radiation, pore water present in cement paste suffers radiolysis and some products can be highly reactive, as electrons and hydroxyl radicals and hydrogen peroxide. These radiolysis products will interact with cement paste and its hydration products, forming a wide range of compounds. Previous work focused on assessing the synergic effects of radiation and environmental conditions, like higher temperature and aggressive groundwater chemicals, on cement paste. Examination of samples detected small differences in mineralogy and microstructure. However, the radiation dose to which samples were exposed (400 kGy) was only a fraction of the expected accumulated dose in cement paste until complete decay of some sealed sources in the repository. Therefore, several thousand kilo-grays must be tested the possibility of radiation to alter cement mineralogy and, as a consequence, its durability The objective of this research is to evaluate the changes in mineralogy and microstructure of irradiated cement paste specimens, in an attempt to establish a relationship between irradiation and durability. Cubic Portland cement specimens were casted and exposed to the gamma radiation of a 60 Co multipurpose irradiator, at IPEN-CNEN/SP. The effects of doses between 1000 kGy and 4000 kGy are evaluated by X-Ray Diffraction, Scanning Electron Microscopy, X-ray micro tomography, neutrongraphy and neutron scattering. This report presents the changes in cement paste mineralogy when samples are examined by XRD. Results indicate that durability can be affected because of the observed changes. Results are expected to indicate the induced changes in cement paste under high radiation doses and to provide hints on its behaviour in the long-term and service-life. The results can be used in safety analysis for deep geological repositories that use cement based materials as engineered barriers. (authors)

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

Operational plant lifetime assessment - UK national nuclear laboratory experience - 15366

Inspection and monitoring of the condition of key plant assets at the Sellafield Site is an important task in helping to enable the continued operation of the reprocessing and waste management facilities. This takes place within a range of environments, from non-active areas to highly active black cells where no man-access is possible. NNL staff work closely with the plant operators and other contractors in carrying out inspection and monitoring tasks, and have a particular expertise in the black cell environments where increased challenges exist. As plants age more work is required in order to underpin ongoing operations and understand the operational lifetime of key assets in order to achieve maximum throughput and utilisation. This paper discusses how expertise in a variety of different technical disciplines is combined in order to both understand and extend the operational life of the Highly Active (HA) evaporators at Sellafield, and a small number of further similar examples are also discussed. (authors)

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

Submersible ROVs pioneer decommissioning of a legacy nuclear fuel storage pond - 15368

Submersible Remote Handling Vehicles (ROVs) are being used in innovative ways at the Sellafield decommissioning, reprocessing and nuclear waste management facility in the UK in a legacy fuel storage pond in support of pond decommissioning. A wide range of sensors and tooling attached to submersible ROVs are being used to characterise the contents of the pond and perform a wide range of maintenance and material retrieval tasks. Visual surveys, sludge and liquor sampling and radiological surveys are just some of the characterisation projects undertaken with the help of the ROVs. The ROVs have also been deployed with tooling including manipulators which can retrieve debris from the pond floor. A variety of mini and work class ROVs are used in the ponds and these can access areas of the pond that the traditional technologies such as long reach tooling and manipulators from overhead cranes cannot reach safely, efficiently and cost effectively. The ROVs are controlled at a distance from the pond to minimise operator exposure to radiation and avoid potential radiological contamination. (authors)

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

System-level logistics modeling of DPC direct disposal - 15511

The U.S. Department of Energy (DOE), Office of Used Nuclear Fuel Disposition, has been conducting a study of the technical feasibility of direct disposal of existing dual-purpose canisters (DPCs) loaded with commercial spent nuclear fuel (SNF). The system-level logistical modeling described here is a part of this study with the primary goals to project the inventory of DPCs in the future and to understand the timing of DPC disposal constrained by thermal power limits for disposal and other key parameters of the waste management system. The logistics simulations also allow for estimating fuel age at emplacement, an important consideration if storage time is limited. This analysis evaluated the effects on DPC direct disposal from uncertainty in repository emplacement power limits, the repository start date, and whether or when the nuclear industry could transition to loading SNF into the smaller capacity multi-purpose canisters (MPCs). MPCs implemented at a future date would likely contain the youngest fuel with highest burnup, but smaller MPCs would cool to the emplacement power limits relatively quickly. The results of this analysis demonstrate that DPC direct disposal could be complete by about 2070 to 2170 depending on the repository emplacement power limit. These completion dates can be expedited by approximately 10 to 40 years in some scenarios through the transition to MPCs. The greatest average SNF age at emplacement is 88 years in the scenarios with the smallest repository thermal power limit in which no transition to MPCs is considered. Transition to MPCs could decrease the average age at emplacement, to as low as 42 years in some scenarios. (authors)

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

Preparation of Waste Fingerprints for the Miscellaneous Beta Gamma Waste Feeds to the Box Encapsulation Plant at Sellafield - 16080

There are a number of legacy pond and silo storage facilities on Sellafield Site that contain a broad range of ILW arising from the early Windscale Pile and Magnox Fuel Reprocessing Programmes. The waste comprises of solid Miscellaneous Beta Gamma Waste (MBGW) from operations (including filters, containerised waste, thermocouple wire, support struts, pumps, soft wastes) and associated sludges that have arisen from the corrosion of the fuel, Magnox Swarf cladding and the MBGW. It is intended to retrieve and package this waste to meet the requirements of interim storage and final disposal in the Box Encapsulation Plant (BEP) at Sellafield. As part of this process each package must be assigned a realistic and justifiable radionuclide and material inventory. These inventories can either be assigned by radiometric measurements including the associated errors or developed by fundamental data underpinning these assessments and a 'chain of custody' approach of knowing where the waste has been and how it has evolved. The subject of this paper is concerned with the development of the waste fingerprints for these legacy waste streams. As the wastes have arisen over a ∼70 year period there have been an assortment of different working practices and developments in equipment design that have led to significant variations in the waste condition and its composition. During storage the waste items have become mixed, corroded and sludge deposits have arisen. Because of this, and that early consignment records are either incomplete or missing, the task of assigning material and radionuclide fingerprints has been very challenging. In addition, to comply with regulatory requirements the inventory assignment has to be sufficiently robust to meet the processing envelope of the encapsulation process i.e. to allow controls to be made on the amounts of reactive materials (e.g. aluminium, Magnox and uranium) that can be processed within each product and allow identification of excluded items from being consigned from the donor plants. Also, as the waste comprises actinides, fission and activation products it was noted that whilst the UK standard inventory code FISPIN10 predicts the actinides and fission products well, there was a significant discrepancy in the prediction of activation products when compared with those predicted by the specialised fusion code FISPACT. It should be noted that the use of FISPACT to predict actinides and fission products is not recommended. To address these issues, - position statements were produced for each of the waste streams that would be consigned to BEP; - gaps within the data were assessed and where possible inactive trial work was identified to address it; - material and radionuclide fingerprint justification documents were developed from the position statements based upon available data, the experimental work and justified assumptions; - where FISPIN runs were required, these were run with a modified activation data library based on the European Activation File 2010 (EAF2010) to model the activation products. This paper summarises the BEP process, discusses examples of how the material and radionuclide waste stream fingerprints have been justified by revisiting the sample data, original consignment records, engineering drawings and recent remotely operated vehicle (ROV) pond surveys and making reasoned assumptions based on operational practices and non-active experimental work. Incorporation of the EAF2010 library within the FISPIN code has offered significant benefits to BEP and indeed other plants processing mixed fission and activated wastes as it allows comparable predictions of activation products compared with that made by FISPACT and for the plant to maintain one data processing stream rather than two if it had to utilise both modelling codes. This work will underpin the inventory submission in support of the Interim Letter of Compliance (ILoC) to Radioactive Waste Management Limited (RWM). The process of examining the original records, plant operation schedules and engineering drawings has enabled removal of some of the pessimisms that have been made in previous assessments. (authors)

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

Simulating Regional Groundwater Flow in the Vicinity of the Nevada National Security Site, Nye County, Nevada - 16104

The Death Valley Regional Groundwater Flow System (DVRFS) occupies an area of about 70,000 km{sup 2} in south-central Nevada and southeastern California. Interest in this system stems from the need to (1) understand the groundwater flow paths and travel times associated with potential migration of radioactive material from the Nevada National Security Site (NNSS) where underground nuclear testing was conducted from 1956 to 1992; (2) characterize the groundwater system in the vicinity of the proposed high-level radioactive waste repository at Yucca Mountain, Nev.; and (3) address a variety of potential effects from NNSS activities on users down gradient from the NNSS and Yucca Mountain. A single groundwater flow model of the DVRFS has been developed that integrates data and results of two previous regional-scale models and supports Department of Energy (DOE) programs at the NNSS. The numerical model was constrained by organizing hydrogeologic data and interpretations in three-dimensional (3D) geographic information systems and constructing a digital three-dimensional (3D) hydrogeologic framework model (HFM) to represent 27 hydrogeologic units (HGUs) and major structures in the DVRFS region. The 3D hydrogeologic data sets were discretized to 1,500 meters (m) grid cell resolution for input arrays required for the model. The DVRFS was simulated using the USGS 3D groundwater-flow modeling code MODFLOW-2000. Two examples showing how the DVRFS regional model is used by the DOE as part of waste management activities at the NNSS: (1) use of the regional model to provide the boundary conditions for site-scale models, and (2) use of the regional model to assess changes in hydraulic gradient and flow paths in the regional flow system resulting from changes in pumping in various areas of interest. (authors)

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

Environmental Characterization Scans Using Sodium-Iodide Gamma Spectroscopy to Determine Ra-226 Concentration in Surface Soil - 16326

The recent natural gas drilling boom has brought heightened attention to the issue of TENORM waste management. Radioactive residues from the extraction, treatment, and purification of materials containing uranium and thorium, or their progeny, pose a public health hazard primarily in the form of ground water contamination. Hydraulic fracturing can liberate formation waters from shale; the high salinity of which can cause radium to move with the water to the surface. The disposal and handling of this water has been a subject of public controversy. For soil remediation projects, radium-226 is generally one of the radionuclides of concern due to its alpha emissions. However performing a survey scan for Ra-226 is difficult because its photon emissions are low energy and have minimal probability of emission per decay (186.2 keV, 3.3% abundance). Additionally resolving its emission from U-235 (185.7 keV, 57% abundance) with field instrumentation is not feasible. Therefore detection of Ra-226 relies on the presence and photon emissions of its progeny. This paper outlines methodology for calculating the minimum detectable concentration of Ra-226 in characterization scans using a sodium-iodide detector array coupled with a multi-channel analyzer. Using progeny ingrowth as a detection proxy requires knowing decay time in order to determine progeny emission rates. Knowledge of site history, process, and prior survey results can be key in determining an accurate decay time. However in the absence of such information in-situ measurements can be used to estimate decay time by comparing observed progeny emission ratios against established values. These values are determined using Oak Ridge National Laboratory's ORIGEN-ARP program to generate photon energy spectra for Ra-226 and its progeny at specified time intervals. Once decay time is established, the detector's minimum detectable concentration can be calculated by synthesizing the expected emission spectra and Los Alamos National Laboratory's Monte Carlo N-Particle transport code to simulate detector response. Traditionally, one of the steps in calculating a system's minimum detectable concentration is to place an appropriate button source under the detector, record the response, and then move the source by a specified increment. This process is repeated until the detector's spatial efficiency has been mapped. Due to the impracticality of performing this with Ra-226 button sources of varying decay times, Monte Carlo N-Particle transport code was utilized to determine the detector's spatial efficiency. A dime sized source with the established emission spectra was placed into the center of a rectangle of soil. This rectangle, including the source, was used as a lattice element to fill the region of space below the detector. The simulation was designed to track the energy distribution of pulses created in the sodium iodide crystal using the F8 tally, and was setup to isolate each source; thereby correlating detector response to source position. The simulation output required post-processing to determine conversion factors from counts per second to disintegrations per second. Post-processing accounted for subtraction of the Compton continuum, and average the data over the scanning pattern to obtain the expected spatial sensitivity during a characterization study. This was performed for the following photo-peaks: 609 keV (Bi-214), and 1764 keV (Bi-214). For calculation of the scan minimum detectable concentration, the surveyor efficiency coefficient from NUREG 1507 was supplanted in favor of a scan speed deviation factor. This was used because the detector utilizes computerized data collection (spatial and spectral). This report finds that, for two shielded 10.16 cm x 10.16 cm x 40.64 cm sodium-iodide crystals with integrated multi-channel analyzers, the minimum detectable concentration in surface soils is less than 1 pCi per gram Ra-226 for a 1 second survey measurement. These results assume a volumetric source with a maximum depth of 15.24 cm and a minimum decay time of 21 days. Verification of the system's capabilities was performed by sending soil samples from scanned areas, and locations where in-situ measurements were performed, to an independent laboratory for analysis. The laboratory results demonstrated that scanned area was principally comprised of soil containing less than 1 pCi per gram Ra-226. This borders the system MDC and it underestimated the concentration of radium in the soil. The probable causes of this is escape of radon gas from the surface soil. Radon is the daughter of radium, and has a high mobility in soil. If the gas escapes, then the progeny used as the detection proxy will be present in lower than expected concentrations. Radionuclide identification using high volume sodium-iodide crystals in low level characterization scans is demonstrated to be possible. Further system refinement will focus on developing a methodology to estimate a radon escape factor for site specific use. Accounting for radon escape in the top 15.24 cm of soil will allow the system to better estimate Ra-226 concentrations in soil. This is a significant advancement over the gross counting statistics used in most studies to satisfy MARSSIM survey requirements, because it will increase stakeholder confidence. (authors)

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

Choosing Your Nuclear Fuel Cycle: A Life Cycle Assessment Perspective - 16425

Nuclear waste management has always been a much debated topic and a key driver for decisions within the nuclear industry. A standardised global approach has not yet been developed and at present many countries are re-considering their position. In the UK the reprocessing of Spent Nuclear Fuel is projected to stop, but no clear indication about the future approach has been given. This contribution sets out the early stages of an approach to compare the possible alternatives based on Life Cycle Assessment (LCA), which is widely used in other sectors to assess the overall environmental burdens of a product or a service across the whole life cycle - i.e. from cradle to grave. The LCA may serve to support decision-making processes within the nuclear industry and, provided that it is used in an open and transparent way, to improve public attitudes towards nuclear energy. To date few LCA studies within the nuclear industry have been carried out, the main issue being the lack of a standardised methodology to evaluate the impacts of radionuclides. The present study proposes a new framework for this purpose, and demonstrates its application in an LCA study of the current UK approach to the management of spent nuclear fuel based on specific data from plants at Sellafield. The final results of the study will show the overall environmental footprint of the reprocessing of spent nuclear fuel, in terms of both radiological and non-radiological impacts. A 'hot spot' analysis will also be performed to highlight the critical processing steps. (authors)

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

Downgrading Nuclear Facilities to Radiological Facilities - 16428

Based on reduced radiological inventories, SNL downgraded 4 SNL Hazard Category 3 nuclear facilities to less-than-Hazard-Category 3 radiological facilities. SNL's Waste Management and Pollution Prevention Department managed the Hazard Category 3 nuclear facilities and implemented the downgrade. This paper examines the multiple steps of the downgrade process. The examination provides useful information to other facilities contemplating or anticipating a similar transition. (authors)

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

Global Solutions Through Simulation For Better Decommissioning - 16457

Each nuclear facility is different due to their history and there is no rule for choosing a decommissioning strategy. There are three major decommissioning strategies. First, 'immediate dismantling', which means the decommissioning begins immediately after the transfer of waste and nuclear material. Second, 'deferred dismantling strategy', meaning the facility is maintained into a containment zone from thirty to one hundred years before being decommissioned. Finally, 'entombment', referring to the placement of the facility into a reinforced containment until the radionuclides decay and reach a level allowing the site release. When a strategy is decided many factors have to be taken into account. Into a major project such as a reactor decommissioning, there are many smaller projects and the decommissioning strategy can be different among these smaller projects. Very often, some entry data are not perfectly known, for example, the dosimetric activity has not been updated through time or after specific events. Because of uncertainties and/or hypothesis existing around projects and their high level of interdependency, global solutions are a good way to choose the best decommissioning strategy. Especially since each entry data has consequences on output results whether it is on costs, cumulated dose, waste or delays. Also the dose, delays or waste management, all have impact on costs. To obtain an optimal scenario into a special environment, it is necessary to deal with all these items together. This global solution can be implemented thanks to simulation in dedicated software which helps define the global strategy, optimize the scenario, and prevent contingencies. For a specific environment, when many scenarios have been developed and simulated, sensitivity studies are really important to choose the optimal decommissioning strategy. Sensitivity studies can be done with simulation tools by comparing results of scenarios directly into the software. This comparison helps to choose the optimal scenario according to which output data is considered as key determinant. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗