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At least 1,765 records · Page 98
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Hydrologic Nuclide Transport Models in Cyder, A Geologic Disposal Software Library - 13328

Component level and system level abstraction of detailed computational geologic repository models have resulted in four rapid computational models of hydrologic radionuclide transport at varying levels of detail. Those models are described, as is their implementation in Cyder, a software library of interchangeable radionuclide transport models appropriate for representing natural and engineered barrier components of generic geology repository concepts. A proof of principle demonstration was also conducted in which these models were used to represent the natural and engineered barrier components of a repository concept in a reducing, homogenous, generic geology. This base case demonstrates integration of the Cyder open source library with the Cyclus computational fuel cycle systems analysis platform to facilitate calculation of repository performance metrics with respect to fuel cycle choices. (authors)

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

Cyclus fuel cycle simulation capabilities with the CYDER disposal system model

An algorithm and supporting database for rapid thermal repository loading calculation was implemented in CYDER. This algorithm employs a Specific Temperature Change (STC) method and has resulted from combining detailed spent nuclear fuel composition data with a detailed thermal repository performance analysis tool from Lawrence Livermore National Laboratory (LLNL), Argonne National Laboratory (ANL), and the Used Fuel Disposition (UFD) campaign. By abstraction of and benchmarking against these detailed thermal models, CYDER captures the dominant physics of thermal phenomena affecting repository capacity in various geologic media and as a function of spent fuel composition. Abstraction based on detailed computational thermal repository performance calculations with the LLNL semi-analytic model has resulted in implementation of the STC estimation algorithm and a supporting reference dataset. This method is capable of rapid estimation of temperature increase near emplacement tunnels as a function of waste composition, limiting radius, waste package spacing, near field thermal conductivity and near field thermal diffusivity. The sensitivity analyses and validation efforts conducted in this work demonstrate the capability of the CYDER tool to provide repository capacity and performance metrics in the context of dynamic fuel cycle.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Vehicle Radiation Monitoring Systems for Medical Waste Disposal - 12102

Hospitals often declare their waste as being 'non-radioactive'; however this material often has excessive levels of radiation caused either by an accident or lack of control. To ensure the best possible protection against the accidental receipt of radioactive materials and as a safety precaution for their employees, waste-handling companies have installed large-scale radiation portal monitors at their weigh scales or entry gates of the incinerator plant, waste transfer station, and/or landfill. Large-volume plastic scintillator-based systems can be used to monitor radiation levels at entry points to companies handling medical waste. The recent and intensive field tests together with the thousands of accumulated hours of actual real-life vehicle scanning have proven that the plastic scintillation based system is an appropriate radiation control instrument for waste management companies. The Real-Time background compensation algorithm is flexible with automatic adjustable coefficients that will response to rapidly changing environmental and weather conditions maintaining the preset alarm threshold levels. The Dose Rate correction algorithms further enhance the system's ability to meet the stringent requirements of the waste industries need for Dose Rate measurements. (authors)

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DOE OSTI2012

Some Fundamental Experiments on Apparent Dissolution Rate of Gas Phase in the Groundwater Recovery Processes of the Geological Disposal System - 12146

The apparent dissolution rates of gas phase in the co-presence of solid phase were examined by in-room experiments in this study. The apparent dissolution rate of gas phase q (mol/m{sup 3}.s) was generally defined by q=aK{sub L}(γP{sub g}-c), where a (1/m) is specific surface area of the interface between gas and liquid phases, K{sub L} (m/s) is overall mass transfer coefficient, γ (mol/(Pa.m{sup 3})) is reciprocal number of Henry constant, P{sub g} (Pa) is partial pressure of gas phase, and c (mol/m{sup 3}) is the concentration of gas component in liquid phase. As a model gas, CO{sub 2} gas was used. For evaluating the values of K{sub L}, this study monitored pH or the migration rate of the interface between water/gas phases, using some experiments such as the packed beds and the micro channel consisting of granite chip and rubber sheet including a slit. In the results, the values of K{sub L} were distributed in the range from 5.0x10{sup -6} m/s to 5.0x10{sup -7} m/s. These values were small, in comparison with that (7.8x10{sup -4} m/s) obtained from the bubbling test where gas phase was continually injected into deionized water without solid phase. This means that the solid phase limits the local mixing of water phase near gas-liquid interfaces. (authors)

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DOE OSTI2012

Environmental Radio-Analytical Research in the Field of a New LILW Disposal Facility in Hungary - 12401

The new Hungarian National Radioactive Waste Repository was established in the granite of the Moragy Block Mountains (Bataapati) to store low and intermediate level radioactive waste originating from Paks Nuclear Power Plant. Before the start of the operation of the facility the environmental characteristics of the site and its vicinity, i.e. the so-called zero level was determined. The determination of the zero level is inevitable as the evaluation of the measurement data in the course of the operation of nuclear facilities should mainly be related to this zero level. In the course of the monitoring activity environmental elements, i.e. air, soil, water (springs, streams, precipitation, fall-out, wash-out, plant and animal samples were investigated from several points of view. From the samples radiocarbon, tritium, Sr-90, gamma emitters, gross alpha, gross beta, and field gamma measurements were carried out. Results reported show that the state preceding the operation of the facility can approximately be considered as the Hungarian background data. (authors)

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

Underwater characterization of control rods for waste disposal using SMOPY

Storage of spent fuel assemblies in cooling ponds requires careful control of the geometry and proximity of adjacent assemblies. Measurement of the fuel burnup makes it possible to optimise the storage arrangement of assemblies taking into account the effect of the burnup on the criticality safety margins ('burnup credit'). Canberra has developed a measurement system for underwater measurement of spent fuel assemblies. This system, known as 'SMOPY', performs burnup measurements based on gamma spectroscopy (collimated CZT detector) and neutron counting (fission chamber). The SMOPY system offers a robust and waterproof detection system as well as the needed capability of performing radiometric measurements in the harsh high dose - rate environments of the cooling ponds. The gamma spectroscopy functionality allows powerful characterization measurements to be performed, in addition to burnup measurement. Canberra has recently performed waste characterisation measurements at a Nuclear Power Plant. Waste activity assessment is important to control costs and risks of shipment and storage, to ensure that the activity level remains in the range allowed by the facility, and to declare activity data to authorities. This paper describes the methodology used for the SMOPY measurements and some preliminary results of a radiological characterisation of AIC control rods. After describing the features and normal operation of the SMOPY system, we describe the approach used for establishing an optimum control rod geometric scanning approach (optimum count time and speed) and the method of the gamma spectrometry measurements as well as neutron check measurements used to verify the absence of neutron sources in the waste. We discuss the results obtained including {sup 60}Co, {sup 110m}Ag and {sup 108m}Ag activity profiles (along the length of the control rods) and neutron results including Total Measurement Uncertainty evaluations. Full self-consistency checks were performed and these demonstrate the validity of the techniques. The results are described and analysed in the context of the measurement performance of the equipment. Different casks were fully characterized using a 60 mm{sup 3} CZT detector, to determine the total activities and spatial profiles. A total activity range measurement of 1x10{sup 8} - 1x10{sup 13} Bq/cm was found to be achievable. Finally, comments are made, based on our measurements, on the ability of this equipment for performing in-situ characterisation of wastes in the harsh environments typical of fuel assembly and waste storage ponds and silos. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Effects of Rangeland Evapotranspiration on Groundwater Recharge, Discharge, and Flow at the Tuba City, Arizona, Disposal Site - 17159

The US Department of Energy Office of Legacy Management is modeling groundwater flow and contaminant transport at a former uranium mill site near Tuba City, Arizona. A goal is to project groundwater travel times and flow volumes between the former mill site and Moenkopi Wash, a down-gradient stream. Aquifer recharge and discharge are sensitive model parameters; however, assigning representative rates is inexact and involves approximations. We applied a remote sensing algorithm to determine spatially variable evapotranspiration (ET), precipitation recharge, and groundwater discharge rates for use in a large scale groundwater flow model for the site. ET is the combination of evaporation and plant transpiration from soil and groundwater. We estimated landscape-scale ET over a 13-year period (2000 to 2012) for distinct plant communities within a 3531-hectare groundwater model domain (GMD), and then evaluated effects of ET on groundwater recharge and discharge within the GMD. Our empirical algorithm was derived from ground ET measurements, multispectral satellite imagery, and temperature data. Groundwater recharge or discharge rates were calculated for each plant community (or ET Zone) as the difference between precipitation (PPT) and ET rates. Recharge occurred in plant communities where PPT exceeded ET; discharge occurred where ET exceeded PPT. Estimates of groundwater recharge rates for upland plant communities that survive on meteoric water ranged from 0 to 88 mm yr{sup -1}. Estimates of groundwater discharge for phreatophyte plant communities ranged from 23 mm yr{sup -1} to 150 mm yr{sup -1}. Phreatophytes are plants that survive by extracting groundwater. Zero recharge occurred in plant communities where ET rates equaled annual average precipitation. An increase in groundwater recharge (PPT > ET) was associated with past land disturbances and heavy livestock grazing in upland areas. Groundwater discharge (ET > PPT) was highest in riparian phreatophyte communities, but lower than optimal in upland phreatophyte communities impacted by heavy grazing. Protecting phreatophyte communities from grazing at Tuba City could potentially increase ET from 153 mm yr{sup -1} to at least 500 mm yr{sup -1}. The validity of using the ET algorithm to estimate recharge and discharge was evaluated by comparing the net volumetric outflow rate for the model domain with base flow measurements collected from Moenkopi Wash. Modeled outflow approximated measured flow gains in the Wash, increasing our confidence in the ET algorithm and in the model. Results suggest that rangeland management practices that reduce groundwater recharge rates and increase groundwater discharge rates should be evaluated as part of an overall groundwater remediation strategy. (authors)

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Terrace Geochemistry at the Shiprock, New Mexico, Disposal Site - 17232

The objective of this investigation was to identify and differentiate potential non-mill-related water inputs to a shallow terrace groundwater system through the use of aqueous chemical and isotopic tracers at a former uranium- and vanadium-ore processing facility. Terrace groundwater in the vicinity of the Shiprock, New Mexico, site is hypothesized to be largely anthropogenic because natural rates of recharge in the terrace are likely insufficient to sustain a continuous water table in the terrace alluvial system, as observed in several analogue terrace locations east of the site and in response to post-mill dewatering efforts across the site. The terrace is composed of alluvial sand and gravel and weathered and unweathered Mancos Shale. Terrace groundwater exists and flows in the alluvium and to a much less extent in the Mancos Shale. Historical data established that in both the terrace and flood plain below the terrace, mill-derived uranium and sulfate is found primarily in the alluvium and the upper portion of the weathered Mancos Shale. Groundwater extraction is being conducted in the vicinity of former mill operations and in washes and seeps to de-water the formation and remove contamination, thus eliminating these exposure pathways and minimizing movement to the flood plain. However, past and present contribution of non-mill anthropogenic water sources may be hindering the dewatering effort, resulting in reduced remedy effectiveness. Groundwater source signatures can be determined based on chemical and isotopic ratios and are used to help identify and delineate both mill and non-mill water contributions. Aqueous chemical and isotopic tracers, such as {sup 234}U/{sup 238}U activity ratios and uranium concentrations, δ{sup 34}S{sub sulfate} and sulfate concentrations, tritium concentrations, and δ{sup 2}H{sub water} and δ{sup 18}O{sub water} are being used in this Phase I study. The aqueous chemical and isotopic analysis has identified areas on the terrace where groundwater is derived from mill-related activities and areas where the groundwater is associated with non-mill activities. A separate field effort of Phase II work will follow, including investigating additional locations for these isotopes and examination of δ{sup 18}O{sub sulfate}, δ{sup 34}S{sub sulfate}, and chloro-fluorocarbon signatures. (authors)

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

Effects of pH on deposition rate of supersaturated silicic acid around geological disposal system - 15245

For the migration assessment of radionuclides around geological repository, it is important to estimate the dynamic behavior of silicic acid under a high alkalinity condition due to the cementitious materials for the construction of the repository. This study examined the pH dependencies of the deposition behavior of supersaturated silicic acid in the co-presence of solid phase. The parameters for the deposition experiments were as follow: the pH was set to 8, 9 and 10, the initial saturated concentration was set to 2-8 mM, the amount of amorphous silica (350 m{sup 2}/g) as solid phase was set to 0.1-1.0 g. The experimental results showed that the initial supersaturated concentrations strongly affected the formation of colloidal silicic acid, increasing the deposition amount of silicic acid and decreasing the soluble silicic acid with time. In other words, the polymerization and the deposition of silicic acid simultaneously arose in these experiments. Furthermore, this study evaluated the apparent deposition rates of silicic acid by assuming the first-order reaction equation considering the specific surface area. As a result, the deposition rate constants, k, were in a narrow range of 10{sup -11} to 10{sup -10} m/s under all experimental conditions in this study. This means that the deposition rate constants do not depend both on pH-value (in the range from 8 to 10) and the initial concentration of supersaturated silicic acid. That is, the estimated deposition rate constants are useful in estimation of the deposition behavior of supersaturated silicic acid, such as the clogging in fractures (flow-paths) around the repository, even if the pH-value of groundwater gradually or dramatically changes. (authors)

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DOE OSTI2015

Interactive statistical decision tools (GiSdT): An open source software integration of decision analysis and stakeholder judgment for sustainable waste management, disposal and remediation - 15650

The vast majority of remediation and waste management decisions are made without quantitative consideration of economic and socio-political factors. They are made instead based on quantitative metrics of human health risk. Sustainable decisions need to be made based on all three 'pillars of sustainability' (economics, environment and social), and require understanding and characterization of the costs and values associated with each pillar. In addition, such decisions need to conform to regulatory or other legal requirements, which often constrains the decision space of interest. Although efforts are often made to include factors across all three pillars (for example, for decisions made under CERCLA), these efforts are usually qualitative, and hence difficult to defend. They lack technical defensibility, transparency and traceability. The purpose of GiSdT (Guided Interactive Statistical Decision Tools) is to provide a quantitative framework whereby all aspects of a decision problem, such as remediation and waste management decisions, can be addressed quantitatively, and hence, defensibly, transparently and traceably. Most decision-makers do not currently have access to useful or usable methods and approaches when are presented with choices that have significant impacts across all three pillars of sustainability. The goal of GiSdT is to provide that access by identifying or developing effective and user-friendly decision methods and approaches that empower decision-makers to explicitly and routinely incorporate all aspects of sustainability into their decision-making. To identify and develop these methods and approaches, GiSdT provides the tools needed for decision-makers and stakeholders to understand and characterize their knowledge of their current decision-making processes, and what methods and approaches they need to pro-actively and quantitatively address all aspects of sustainability in their decisions. GiSdT is an open source interactive framework program that provides the tools needed to address the relevant components of a sustainability-based decision problem, including describing the decision landscape, translating that landscape into goals and objectives, valuing the measurable attributes that describe each objective, identifying decision options and addressing the uncertainty in the attributes (e.g., human health risk, institutional controls) through appropriate probabilistic models. In addition to addressing these quantitative technical components, the GiSdT program is aimed at facilitating stakeholder involvement so that the perspectives, values and objectives are all relevant stakeholders are addressed explicitly in the decision making process. The technical underpinnings of our software program, called Guided Interactive Statistical Decision Tools (GiSdT), are described. (authors)

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

Mercury Speciation in Savannah River Site High-Level Waste: Determination and Implications for Waste Handling and Disposal - 16178

As part of a larger program to address mercury issues at the Savannah River Site, a number of samples from across the salt processing flowsheet have been collected and analyzed for several mercury species. The results indicate the presence of organomercury species, predominately methylmercury cation. This result was not expected, and it represents a significant paradigm shift in the understanding of mercury chemistry in high-level tank waste. Concentrations of total and soluble mercury have been measured as high as 0.5 g/L with methylmercury concentrations of at least fifty percent of that value. The distribution of mercury species being observed have ramifications to waste processing strategies. In particular, the mercury behavior across the cesium solvent extraction process has been examined. Leachates, from toxicity testing of the cementitious waste form used for decontaminated salt waste at Savannah River, have been tested and shows methylmercury as the dominant extractable species. (authors)

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

Developing a New National Programme and Implementation Plan for the Management and Disposal of Spent Fuel and Radioactive Wastes in Romania - 16391

The European 'Waste Directive' (2011/70/Euratom) required each Member State to report by August 2015 on their National Programme for management of spent fuel and radioactive wastes. In Romania, the Nuclear Agency (ANDR) was responsible for preparing the National Programme report, and this was done in a step-wise manner that involved the regulators and waste producers. The starting point for the process was an assessment of existing policy against the evolving situation in the nuclear sector in the country, most notably the decision to progress with the construction of two new CANDU reactors. The final agreed National Programme report submitted to the European Commission describes the activities currently undertaken to manage spent fuel and radioactive wastes in Romania. The report also sets out, at a high-level, the additional activities that will need to be taken in the future (and an indicative timeline), including those steps that will be required to implement a new surface repository for short-lived wastes, and a geological repository for spent fuel and long-lived wastes. Additional, on-going work is intended to lead to a revision of Government policy and the development of a more detailed implementation strategy, underpinned by a programme of R and D and robust financing plans. (authors)

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

Solutions for Disposal of Intermediate Level Waste in the UK - 16693

GNS mbH is a competence centre owned by of the German utilities and tasked with the management of spent fuel and nuclear waste of all activity levels arising from operation and decommissioning of the commercial German nuclear power plants. Waste management products and methods developed by GNS over the past decades are at present the standard solutions for their respective tasks in Germany. While regulatory environments in the nuclear industry vary strongly from country to country thus limiting the one-to-one portability of such established solutions, GNS has managed to offer its services abroad, with continuously growing success. Challenges and first results of GNS' activities in the UK are the subject of this paper. Content: GNS in Germany and UK; Ion Exchange Resin at Sizewell-B; Drying of wet Intermediate Level Waste at Bradwell NPP; Lessons Learnt in the UK; New Technology Optimised for UK waste.

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