Download or read book Criticality in the Far Field of a Granitic Repository for Used Nuclear Fuel written by Alex Salazar and published by . This book was released on 2018 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: A repository for used nuclear fuel (UNF) must employ several barriers to reduce the risk of a lethal dose to the biosphere over geological periods of time. It is presumed that waste canisters can be engineered to prevent a critical configuration of fissile material by design. However, given the quantity of UNF in interim storage in the United States intended for final deposition, a comprehensive failure scenario involving the repository-wide leaching of fissile isotopes from used fuel, radionuclide transport in groundwater, and re-concentration in the far-field may eventually present a concern for criticality. Such a criticality event may create a pathway for fission products to the environment if the host rock is compromised. This dissertation explores the impact of far-field criticality on repository performance over long periods of time. It attempts to integrate all necessary processes and considerations under a notion of conservatism favoring the formation of a critical mass from used nuclear fuel. A critical deposition is hypothesized to pose a threat to the material integrity of the host rock through the steady release of heat over time, as opposed to the explosive releases of energy considered in previous studies. In particular, the role of thermal creep is evaluated as a steady-state failure metric, which emphasizes the combined role of reactivity feedback mechanisms and heat transfer in determining the temporal extent of chain reactions underground. The failure scenario is isolated among other relevant features, events, and processes as the primary concern of the performance assessment for a crystalline granitic repository. Repository loading cases are established based on the uncertainty in the current inventory of used nuclear fuel. These source terms are used in a radionuclide transport model that incorporates the Latin hypercube sampling method to probe the uncertainty in the total accumulation of uranium from advection in fractures. The configurations of fissile material in host rock required for criticality are evaluated based on representative precipitate compositions obtained from the transport analysis, where the role of a reducing and reflecting region of shale is emphasized. Given the nature of the critical depositions as both open reactor systems and porous media, a thermo-hydrological analysis is employed to evaluate the coupled heat and mass transfer in the geology when energy is released from fission reactions. This analysis is motivated by the assumption that reactivity behavior with evolving water content and temperature must be fully coupled, and boundary conditions are imposed to evaluate a maximal extent of desaturation. The observed changes in fluid content and densities in the system over time are used to guide an integrated neutronics evaluation incorporating the Doppler effect. Feedback coefficients covering the simultaneous effects of Doppler broadening, the loss of moderator, and the arriving plume of uranium solutes from the repository array are applied to a quasi-steady-state heat transfer model. This model provides insight on the dynamic evolution of system temperature over time parametrized on the source term of incoming fissile material, and results are applied to a thermal creep model to evaluate total integrated strain and system failure. Given the time dependence of the creep phenomenon, optimal source terms of fissile material may be conducive to failure via creep. However, these mass fluxes exceed those observed in the transport analysis, which employed assumptions to maximize these quantities. The conditions under which repository performance can be impacted by steady-state criticality prove to be heavily dependent on the repository inventory and the specific choice of host rock. This mandates that a site intended for final UNF disposition be subject to increasing scrutiny in proportion to the amount of waste that is loaded. Based on the results of the study, it is strongly proposed that the threat of a far-field criticality event can be dramatically reduced by the introduction of depleted uranium to waste canisters. Overall, given the compounded effect of utilizing many heavily conservative assumptions in the study, the far-field criticality phenomenon is not deemed to be of especial importance to repository engineering, especially with additional enhancements to existing engineered barrier systems.
Download or read book Typical Repository Conditions for Generic Commercial and Defense High level Nuclear Waste and Spent Fuel Repositories in Crystalline Rock written by and published by . This book was released on 1984 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Criticality Issues with Highly Enriched Fuels in a Repository Environment written by and published by . This book was released on 1998 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents preliminary analysis of a volcanic tuff repository containing a combination of low enrichment commercial spent nuclear fuels (SNF) and DOE-owned SNF packages. These SNFs were analyzed with respect to their criticality risks. Disposal of SNF packages containing significant fissile mass within a geologic repository must comply with current regulations relative to criticality safety during transportation and handling within operational facilities. However, once the repository is closed, the double contingency credits for criticality safety are subject to unremediable degradation, (e.g., water intrusion, continued presence of neutron absorbers in proximity to fissile material, and fissile material reconfiguration). The work presented in this paper focused on two attributes of criticality in a volcanic tuff repository for near-field and far-field scenarios: (1) scenario conditions necessary to have a criticality, and (2) consequences of a nuclear excursion that are components of risk. All criticality consequences are dependent upon eventual water intrusion into the repository and subsequent breach of the disposal package. Key criticality parameters necessary for a critical assembly are: (1) adequate thermal fissile mass, (2) adequate concentration of fissile material, (3) separation of neutron poison from fissile materials, and (4) sufficient neutron moderation (expressed in units of moderator to fissile atom ratios). Key results from this study indicated that the total energies released during a single excursion are minimal (comparable to those released in previous solution accidents), and the maximum frequency of occurrence is bounded by the saturation and temperature recycle times, thus resulting in small criticality risks.
Download or read book Disposition of High Level Waste and Spent Nuclear Fuel written by National Research Council and published by National Academies Press. This book was released on 2001-07-05 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt: Focused attention by world leaders is needed to address the substantial challenges posed by disposal of spent nuclear fuel from reactors and high-level radioactive waste from processing such fuel. The biggest challenges in achieving safe and secure storage and permanent waste disposal are societal, although technical challenges remain. Disposition of radioactive wastes in a deep geological repository is a sound approach as long as it progresses through a stepwise decision-making process that takes advantage of technical advances, public participation, and international cooperation. Written for concerned citizens as well as policymakers, this book was sponsored by the U.S. Department of Energy, U.S. Nuclear Regulatory Commission, and waste management organizations in eight other countries.
Download or read book Evaluation of a Potential Nuclear Fuel Repository Criticality Lessons Learned written by and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the international geological congress written by Yuan Daoxian and published by VSP. This book was released on 1997-05 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume includes all aspects of environmental geology, i.e. the impact of different geological processes, the geological problems in large river development, trace elements and human health, geology of waste disposal, and environmental geology mapping.
Download or read book Chemical Abstracts written by and published by . This book was released on with total page 2762 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1988 with total page 1684 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Criticality Safety Analysis of a Spent Fuel Waste Package in a Tuff Repository written by B. H. Weren and published by . This book was released on 1983 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: An assessment has been performed of the criticality potential associated with the disposal of spent fuel in a tuff geology above the water table. Eleven potential configurations were defined which cover a vast range of geometries and conditions from the nominal configuration at emplacement to a hypothetical configuration thousands of years after emplacement in which the structure is gone, the fuel pellets disintegrated and the borehole flooded. Of these eleven configurations, four have been evaluated at this time. The results of this evaluation indicate that even with very conservative assumptions (4.5 w/o fresh fuel), criticality is not a problem for the nominal configuration either dry or fully flooded. In the cases where the condition of the waste package is assumed to have severely deteriorated, over long times, calculations were performed with less conservative assumptions (depleted fuel). An assessment of these calculations indicates that criticality safety could be demonstrated if the depletion of the fissile inventory during fuel irradiation is taken into account. A detailed discussion of the calculations performed is presented in this report. Also included are a description of the configurations which were considered, the analytical methods and models used, and a discussion of additional related work which should be performed.
Download or read book Environmental Geology written by Yuan Daoxian and published by CRC Press. This book was released on 2023-05-31 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume includes all aspects of environmental geology, i.e. the impact of different geological processes, the geological problems in large river development, trace elements and human health, geology of waste disposal, and environmental geology mapping.
Download or read book Criticality Safety Issues Associated with the Burial of Highly Enriched Nuclear Fuel in a Geologic Repository written by and published by . This book was released on 1992 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study is to provide some basic guidance regarding the criticality safety implications associated with long term burial of highly enriched nuclear fuel in a geologic repository. Generic calculations to determine the distance required to neutronically isolate neighboring fissile regions are reported. Two specific fuels are also addressed, Fort Saint Vrain and Shippingport PWR Core-2 Seed-2 (PWR). These fuels are addressed under both dry and flooded conditions. Fort Saint Vrain fuel contains a uranium-graphite fuel matrix, is graphite moderated and has a relatively low 235U loading (∼1 kg per element). PWR contains a uranium-zirconium fuel matrix, is water moderated, zircaloy clad and has a 235U loading of ∼15 kg per cluster. These two fuels are representative of many of the fuels currently stored at the Idaho Chemical Processing Plant (ICPP). The spent fuel storage system under consideration involves filling cylindrical canisters with spent nuclear fuel. These canisters are then to be placed into a geologic repository. Salt and tuff are the two most likely materials in which the canisters will be buried. Canisters will require sufficient material between them to ensure that the overall reactivity stays within acceptable limits. Fuels will also have to be shown to be critically safe under a variety of conditions. These conditions include flooding and the loss of the physical integrity of the fuel.
Download or read book SR 97 Main report written by and published by . This book was released on 1999 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High Level Radioactive Waste Management written by and published by . This book was released on 1994 with total page 720 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Far field Thermomechanical Response of Argillaceous Rock to Emplacement of a Nuclear waste Repository written by D. F. McVey and published by . This book was released on 1980 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Environment Abstracts Annual written by and published by . This book was released on 1992 with total page 1216 pages. Available in PDF, EPUB and Kindle. Book excerpt: This database encompasses all aspects of the impact of people and technology on the environment and the effectiveness of remedial policies and technologies, featuring more than 950 journals published in the U.S. and abroad. The database also covers conference papers and proceedings, special reports from international agencies, non-governmental organizations, universities, associations and private corporations. Other materials selectively indexed include significant monographs, government studies and newsletters.
Download or read book Deep Underground Disposal of Radioactive Wastes written by International Atomic Energy Agency and published by Bernan Press(PA). This book was released on 1985 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1996-09 with total page 1244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
