An algorithm and results of calculation of the process of vacuum drying of a metal-concrete container intended for long-term "dry" storage of spent nuclear fuel are presented. A calculated substantiation of the initial amount of moisture in the container is given.Introduction. The problem of storage of spent nuclear fuel (SNF) has become pressing in recent times for the Russian Federation. The SNF of high-power channel-type reactors (HPCTRs), whose processing has not been found expedient because of the low residual content of fissionable nuclides, accounts for the considerable amount of SNF requiring long-term storage [1].Spent nuclear fuel is stored at present in near-reactor cooling pools (ponds) and separate spent-fuel storages located on the premises of atomic electric power plants under the conditions of the so-called "wet" storage. The overall capacities of these storages are not designed for long-term storage of the entire SNF accumulated during the years of operation of the atomic electric power plants.One method of solution of the above problem is the technology of compacted storage of spent fuel assemblies (SFAs) in pools [2], which makes it possible to double, in practice, the number of SNF-containing canisters compared to the original design. However, as calculations show, pools in the Russian Federation will soon be filled even in the case of the compacted method of SNF storage. Also, it should be noted that the compacted method of SNF storage aggravates the issues of safety of the existing storages and hinders access to the walls and bottoms of cooling pools with the aim of controlling the hermeticity of these structures.The period of stay of the SNF under water approximates the maximum permissible one (30 years) in many cooling pools. The safety and reliability of handling of the SNF under the conditions of "wet" storage of the fuel are largely determined by the preservation of the material of the fuel-element shells. During the "wet" storage, we have corrosion processes in the SFA boxes and degradation of the material of the fuel-element shells, which may finally lead to a loss of vacuum sealing by the fuel elements and to escape of radionuclides to production floor-areas and the environment.An alternative to the "wet" storage technology is the technology of "dry" storage of the SNF precooled in water to reduce radioactivity and heat release. In this case the fuel-storage conditions are improved, since water is a more aggressive medium than dry air or inert gases.In implementing the "dry" method of long-term (up to 40-50 years) storage of the HPCTR SNF, it was proposed that TUK-109 transport-package sets based on the metal-concrete container of the "Design Office for Specialized Machine Building Enterprise" (St. Petersburg) be used. These containers meet both the standards of safe storage and transportation of the SNF in the Russian Federation and the requirements of the International Atomic Energy Agency. Coincident with the development of the container structure, work on creation of the domestic...
The paper describes in brief the heat and mass transfer processes in the transfer of spent nuclear fuel of the RBMK-100 reactor from "wet" to "dry" cask storage. The algorithms are described and the results are presented of the "through" calculation of the heat and mass transfer processes in ampoules and in a metal-concrete cask at various stages of spent nuclear fuel management.Keywords: nuclear power plant, spent nuclear fuel, metal-concrete cask, vacuum drying, long-term storage of casks, computational modeling.Introduction. Storage of spent nuclear fuel (SNF) is an urgent problem for many countries with developed nuclear power industry. In the Russian Federation, as a result of many years of operation of nuclear power plants (NPP), an enormous amount of SNF has been accumulated, which is stored in both at-reactor cooling ponds and in separate spent fuel storage pools (SNFP) on the premises of the NPPs. The total volume of these storage pools is not intended for long-term "wet" storage of the full amount of accumulated fuel. An especially complicated situation was observed at NPPs with RMBK-1000 high-power channel reactors because of the limiting capacity of the at-plant SNF storages.In 2011, a unique event took place in nuclear power engineering of the Russian Federation -the Complex of SNF "dry" storage and management systems based on the dual-purpose (storage and transportation) metal-concrete transportpacking complex TUK-109 was put into trial-commercial operation at the Leningrad NPP. The creation of the Complex makes it possible to realize disposal of SNF from the site of the NPP for long-term storage or processing. The developed technology was subsequently unifi ed and extended to the Kursk and Smolensk NPPs.The present paper considers the heat and mass transfer processes in transferring spent nuclear fuel from "wet" to "dry" cask storage, describes the algorithms, and presents the results of their computational modeling.Formulation of the Problem. The transport-packing complex TUK-109 used for "dry" storage and transportation of SNF consists of a metal-concrete cask (MCC) and a damping housing (PDH) protecting the MCC against damages and seal failure in case of bad road accidents. Inside the MCC body, there is a case with 144 ampoules containing fuel element clusters (FEC).The process of transferring SNF from "wet" to "dry" cask storage includes the following technological stages [1]:
There are considered the methods of mathematical and physical modeling of the heatmasstransfer in storage facilities of different types {water pools, “dry” cask type storages}. There are shown the computational results, obtained in application to the storage facilities, located at nuclear power plant territory. There are considered the technological operations, connected with the spent fuel transference from interim “wet” storage to a longer term storage in casks facility {cask’s loading with fuel, its drying under vacuum}. Special attention is devoted to an accident situation in “wet” storage — a loss of the coolant circulation through pool and following loss of water due evaporation. Problems of further investigations are formulated.
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