An International Spent Nuclear Fuel Storage Facility Exploring a Russian Site as a Prototype: Proceedings of an International Workshop (2005) / Chapter Skim
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The Management of High-Level Radioactive Wastes from the Mayak Production Association and Plans for the Creation of an Underground Laboratory
The Management of High-Level Radioactive Wastes from the Mayak Production Association and Plans for the Creation of an Underground Laboratory
Pages 225-239
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From page 225... ...
Implementation of this program has involved the following stages: · 19691971: creation of laboratory facilities for the solidification of solutions in a glass furnace using direct electrical heating · 19731977: testing of pilot facilities using model radionuclide-labeled solutions · 19861988: start up of the complex and regular operation of the first electric furnace · 19911997: regular operation of the second electric furnace · 2001: regular operation of the third electric furnace The first unit of the vitrification shop included two EP-500 electric furnaces, each capable of processing 500 liters of solution per hour. One furnace, which was put into operation in 1986, was used for one year and then shut down due to contamination of the water-cooled current feeds of its molybdenum electrodes.
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From page 226... ...
As illustrated in Figure 1, the basic technical outline of the process for the vitrification of high-level radioactive wastes includes the following elements: · solution preparation section, including a chain of various containment vessels · vitrification section, including an electric furnace with systems for solution correction, glass pouring, power supply, and cooling · gas treatment section, consisting of a number of gas cleaning devices and filters · transport section, including a moving conveyer, a chamber for the assembly of cases, and a protective shield · storage facility for the vitrified wastes The technical process is carried out as follows. Liquid radioactive wastes from the repository go into a vessel where the solutions are prepared for processing.
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From page 227... ...
227 Atmosphere Into Columns Absorption Filters furnace. Collector Condensate electric Additives EP-500/1-r Flux Furnace the Fluxing in and Electric Spent wastes Fuel Mixing Belt Wastes, radioactive of Conveyer vitrification of Repository diagram Container Schematic 1 Protective FIGURE
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From page 228... ...
The technical characteristics of the electric furnace are presented in Table 1. From the start of operation until May 2003 the complex processed 15,331 cubic meters of fluxed high-level radioactive solutions with a total activity of 364 million curies and produced 2946 metric tons of aluminophosphate glass.
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From page 229... ...
229 device; g pourin 7: block; skimmer 6: barrier; 5: feeder; 4: electrodes. plate; cover molybdenum 3: 11: line; glass; gas 2: molten 10: structure; receptor; furnace 9: 1: blocks; furnace.
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From page 230... ...
As a result, up to 500 metric tons of aluminophosphate glass with a total activity of 250300 curies per liter are produced over the course of a year, with this glass being stored in a specially equipped aboveground repository. Condensates from the steaming of the refined products and from the process of vitrifying the fluxed solutions are transferred for regeneration of the nitric acid, which is reused in the technical process, while the tritium condensate is discharged into a storage reservoir.
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From page 231... ...
As a result of this separation the majority of the wastes may be categorized as mid-level, while the separated fractions of strontium-cesium and transuranic elements may be solidified using small-volume remote-controlled equipment. Modernization of the existing facility to incorporate the partitioning concept would make it possible to optimize the technological High-level refined products from one extraction cycle, 30003500 m 3 Steaming Vat solution Condensate NaNO3 Fluxing Steaming H3PO4 Vitrification Tritium Regeneration of condensate acid Storage of phosphate glass, 500 metric tons, 250300 curies/kg Reuse in technological Reservoir No.
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From page 232... ...
in the amount of 300 kilograms per year with a total activity of 2 curies per year for alpha radionuclides. One special feature of the system is its capacity for simultaneously processing mid-level refined prod Medium-level High-level refined solutions from Plant products from one 235, 13,00018,000 m3, extraction cycle, 0.8-0.9 million curies 30003500m3 1025 curies/liter Condensate Condensate Steaming Regeneration of HNO3 Steaming Vat solution HNO3 reused in process Condensate to special disposal, 16,00021,000 m3 Vat solution, Fractionation 10-710-8 1,500 m3 curies/liter Refined product, Cs concentrate Sr concentrate Transuranic concentrate 4,500 m3 Averaging Vitrification Solidification Cementation Storage Storage Storage 7 metric tons of 0.3 metric tons ceramic 5200 metric tons cement borosilicate glass, compound, compound, 15,000 curies/liter 2 curies/liter Sr+Cs, 0.1 curies/liter FIGURE 4 Promising system for processing high-level and medium-level wastes using preliminary fractionation.
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From page 233... ...
PLAN FOR AN UNDERGROUND LABORATORY AT THE MAYAK PRODUCTION ASSOCIATION From the 1960s through the 1980s specialized geological survey organizations carried out comprehensive prospecting studies in areas adjoining the Mayak Production Association in northern Chelyabinsk Oblast to search for geological formations that would be suitable for the burial of liquid radioactive wastes. As a result of experimental studies it was concluded that this area lacked the necessary geological conditions for ensuring the reliable isolation of such wastes.
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From page 234... ...
The following areas for future work have been defined for the next stage in the process of creating a site for the deep burial of radioactive wastes: · detailed study of promising sites, to be conducted with the help of test wells and a range of intrawell, site, and deep-level geophysical studies · evaluation of the tension-deformation status of the sites at depths where the future underground laboratory would be located and reconstruction of the tectonic-dynamic situation in the geologic past · creation of a geodynamic model of the Mayak region and evaluation on this basis of the probable development of tectonic processes during the timeframes required for the long-term isolation of high-level radioactive wastes · determination of a site for the placement and construction of an underground laboratory The main objectives for constructing an underground laboratory lie in establishing the correctness of design solutions being developed with regard to the burial of radioactive wastes in promising sites within rock formations and con
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From page 235... ...
Regardless of the design for the facility, scientific research work in the underground laboratory is to include the following, as well as other topics: · provision of a repository for vitrified wastes · detailed studies aimed at proving that the site selected and the types of rocks surrounding it meet the demands necessary for ensuring the reliable isolation of wastes · study of the thermal, mechanical, and sorption properties of the surrounding rock · determination of the physicomechanical parameters of the structuraltectonic blocks, evaluation of lithostatic and tectonic violations, and study of the condition of the rock massif and underground structures under the influence of natural and man-made factors · study of the effect of technological burdens (thermal, radiation, and chemical impacts) on the condition of the rock massif and on heat and mass transfer conditions · study of the isolation capacities of various materials and engineering barrier designs under the influence of natural and engineered factors · experiments on the distribution of nuclides within the selected site in the rock massif after the burial of real wastes · study of the behavior and stability in real conditions of forms of solidified wastes and their packaging · study and evaluation of the qualities, means, and methods of controlling processes within the rock massif · development of equipment and technology for managing wastes and isolating them in real underground conditions During the period of construction and operation of the underground laboratory, personnel are to make and further develop technical decisions on the design of the underground solidified waste sarcophagus and the entire cycle of operations from the delivery of wastes until their final isolation.
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From page 236... ...
In the second stage, after the direction of natural flow filtration is determined, wells 4 and 5 are to be drilled, one in the direction of underground water flow movement and the other perpendicular to it. From the depth of 0 to 300 meters they are initially to be drilled at a diameter of 132 millimeters.
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From page 237... ...
Based on the results of hydrochemical and radiochemical research, studies are to be made on the effective rate of flow of underground water through fractured zones, the sorption properties of rock with regard to particular isotopes, and the migration of radionuclides in underground water under specific geological conditions. For this purpose, well geophysics methods (thermometry, gamma well logging, and resistivity measurement)
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From page 238... ...
Objectives for the laboratory research include the following: · verification of predictive data on gas separations during the underground waste storage process · detection of changes in rock properties due to the effects of radiation The following work is required to develop predictive assessments and ensure that the necessary data are available for the project: · determination of the threshold dose at the start of surface destruction of minerals and evaluation of the permissible time of exposure at various doses · study of the effect of temperature and irradiation on the physicalmechanical properties of various types of rock · study of the transformation of water content during irradiation and at temperatures from 20 to 200°C · study of a group of minerals and their compositions in the aim of using them as barriers to isolate the cases of wastes from the surrounding geological environment
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From page 239... ...
Costs for the initial complex total about $2 million, with the entire underground laboratory complex to cost around $5 million. Creation of the country's first such laboratory will allow the facility to become a research and demonstration center that will promote the comprehensive study of problems associated with the underground storage of solidified radioactive wastes and the demonstration of technical solutions and underground waste isolation methods.
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