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[en] The accident at the Japanese nuclear power plant (NPP) Fukushima-1 in March 2011 showed that possibility of accidents with potentially serious radiation consequences could not be excluded with large-scale measures for improvement of safety level. For spent nuclear fuel storage facilities, one of such accidents may be the interruption of heat removal from spent nuclear fuel (SNF) due to the failure of the cooling system as a result of disruption of the power supply system with the failure of backup power sources or rapid full dehydration of the wet SNF storage as a result of the destruction of building structures and its depressurization. The decision to take preventive measures in advance to minimize exposure to personnel and the public is based on conservative estimates of possible radioactive discharges. To perform such assessments, the operating organizations carry out a calculated justification of the thermal and hydraulic characteristics of the SNF system in the accident scenarios with long-term blackout and a violation of heat removal. APROS is one of the software tools that are used in SEC NRS for calculating the thermal-hydraulic characteristics of systems in transient modes by solving the equations of heat and mass transfer in a steam-water mixture. For more detailed calculations of the structural elements of spent fuel assemblies (SFA) temperature, the ANSYS software is used, which implements the finite element method. The results obtained with the help of the above simulation tools are used by specialists of SEC NRS to assess the protective measures developed by operating organizations.
[en] The French natural gas transmission network offers several entry and exit points (cross-border interconnections, LNG terminals, underground storage facilities), giving its users a choice between various supply combinations. Since 1 November 2018, the TRF has become the contractual framework for the French transmission network. It is built to a model that combines judicious investments in terms of infrastructure with contractual mechanisms which facilitate the management of the network's residual bottlenecks. A balanced supply management is required for the smooth running of the gas system in winter. The French operators, GRTgaz and Terega, must ensure the safety, efficiency and balance coverage of their networks at all times. In accordance with their obligations, the GRTgaz and Terega networks must have the necessary infrastructures to assure continuity in the transportation of gas, including in the event of a so-called P2 cold peak. In this context, in accordance with the Energy Code, art. L141-10, GRTgaz and Terega produce an annual Winter Outlook in order to verify compliance with these obligations and share their analysis of the coming winter with the market. The Winter Outlook is an exercise that makes it possible to assess the balance coverage for the French zone and downstream of the network bottlenecks for different gas demand scenarios and supply schemes. The Winter Outlook 2020-2021 is the 3. edition to be published that incorporates the provisions made as part of the creation of the TRF on 1 November 2018.
[en] The nuclear energy sector of Armenia includes one nuclear power plant — Armenian NPP (ANPP). ANPP consists of two units with Soviet design WWER-440/270 model reactor that is a version of the WWER-440/230 serial model with special seismic considerations in the design. Unit 1 started its commercial operation in 1976 and the Unit 2 in 1980. Both units were shut down shortly after the earthquake of December 7th, 1988. Following the completion of repair and safety upgrading activities Unit 2, after 6.5 years of shutdown, restarted operation in 1995 and it has been operational since then. Unit 1 reactor plant remains in long-term shutdown condition (with no fuel in the core). The Spent Fuel Pools (SFPs) of both units are currently in operation — the fuel discharged from the operating unit 2 reactor core is put first in the SFP of that unit, then, after several years of storage, is transferred to the SFP of the unit 1. When the decay heat is low enough the spent fuel assemblies are moved from the SFP of the unit 1 to the spent fuel interim ‘dry’ storage facility (Dry Casks for long term Storage of Spent Nuclear Fuel).
[en] The Federal Office for the Safety of Nuclear Waste Management (BfE) is the competent licensing authority for interim storage of spent nuclear fuel (SNF) and high-level radioactive waste (HLW) in Germany. The concept of dry interim storage comprises dual purpose casks (DPC) equipped with a double barrier lid system with permanent monitoring of its leak-tightness. Existing storage licences in Germany are limited to 40 years. Due to the time needed for site selection, licensing procedure, construction and commissioning of a deep geological repository (DGR), a prolongation of the interim storage period will be necessary to bridge the gap until final disposal. To demonstrate if safety requirements could be fulfilled by the transport and storage cask beyond the initially licensed 40 years additional research is required. Research towards material degradation e.g. ageing of cask materials or internals, fuel assembly behaviour and behaviour of storage facility buildings and operational equipment is the basis for the safety of prolonged SNF storage. To identify potential fields of further interest it is also necessary to acquire additional data for the above mentioned research. As interim storage facilities are a key step towards the final disposal, it is also necessary to conduct research towards the impact of prolonged interim storage on the final disposal, especially due to the increasing relevance of ageing effects like material degradation. This includes foremost data acquisition and storage as a prerequisite to enable a safety based choice of actions. Furthermore, as Germany is phasing out of nuclear energy, the knowledge management in the nuclear field gains enormous importance especially with regard to human resources. The BfE as licensing authority has initiated several research projects to cover the foresaid topics to be presented in this article. (author)
[en] It is envisaged that all spent nuclear fuel generated during the operation of the RBMK-1500 reactors at the Ignalina NPP will be stored in dry storage facilities for at least 50 years prior to its disposal into a deep geological repository. According to the Radioactive Waste Management Development Programme (approved in 2015) the construction of the repository is planned to be completed in 2066, and all SNF should be disposed of until 2073. Before the construction of the repository, various preparatory activities shall be performed: site selection, repository concept and designing, environmental impact studies, safety analysis, etc. There are two geological formations in the territory of Lithuania potentially suitable for the construction of the repository – crystalline rock and clayey formations. Dry storage casks that are currently used for RBMK-1500 SNF interim storage at Ignalina NPP site cannot be used for the disposal purposes. Therefore, SNF reloading from the storage casks into appropriate disposal canisters will be necessary. The type of the disposal canister depends on the geological formation in which the repository is constructed. According to the existing knowledge, copper canisters are considered appropriate for disposal into crystalline rock and steel canisters are suitable for clayey formations. This paper presents preliminary criticality and radiation safety evaluation of copper and steel canisters containing RBMK-1500 spent fuel. Radiation characteristics and dose rates on the surfaces of the canisters are modelled assuming SNF disposal after 50 and 100 year interim storage. (author)
[en] Fuel is periodically replaced in nuclear power plants (NPPs), generating “Spent Nuclear Fuel” (SNF). The paper attempts to calculate the relationships between the costs and the sizes of SNF storage facilities. This is done by estimating reduced-form equations based on publicly available data. The values reported here should not be considered as the only possible outcomes; they are used here to understand relative NPP owner economic incentives. The paper finds that once the NPP has been decommissioned, and only the on-site dry storage remains, there might not be a cost reason (from the point of view of the NPP owner/operator) to move the SNF to centralised facilities. However, there is a consensus that centralised facilities (a) would be more safe and secure than dispersed on-site storage locations, (b) would facilitate final disposal, and (c) can reduce the risks perceived by local communities near SNF storage facilities. (author)
[en] The minesite Konrad is going to be converted into a final storage facility for solid or consolidated radioactive waste with negligible heat generation. To investigate the flow in the exhaust channel "chimney" a test facility with 1:5 scaled mockup was built. 2O-PIV measurement technology was used to analyze the flow at the envisaged sample taking point. The main purpose of the tests was to forecast if the different criteria for homogenous flow defined by DIN ISO 2889 could be met. Two test parameters have been examined: (total) air volume flow and particle size. Only one of three investigated criteria was passed for all particle sizes and volume flows. Further investigations into adaptions of the exhaust channel "chimney" are necessary to fulfill all requirements for homogenous flow at the sample taking spot for all particle sizes and all (normal) operation status.
[en] Spent fuels (SF) assemblies from Paks Nuclear Power Plant (Paks NPP, Hungary) are placed in Spent Fuel Interim Storage Facility (SFISF) since 1997. The SFISF is a modular vault dry storage (MVDS) type design accommodating SF after a minimum of a few years of cooling time in the reactor decay pool. The SFs are stored individually and separately in the vault modules (VM) in airtight sealed fuel storage tubes (FST) filled with inert gas. Decay heat rejection is achieved by buoyancy driven air flow through the vault, passing over the exterior of the array of storage tubes. The capacity of the SFISF was planned on the total amount of the SFs arising from the planned 30-year lifetime of Paks NPP. To store these SFs a 33-vault facility was designed with 450 FST in each vault. Until now all together 24 vaults have been constructed. Sixteen vaults were built with 450 FST in each vault. To make the storage economically more efficient the number of FSTs was increased from 450 to 527 in the last eight vaults. This was provided by use of the built-in reserves of the design and the development of analyses techniques making it possible to reduce the conservatism in calculations. According to this modification the total capacity of the SFISF was increased by around 9%. At the millennium a decision was made to extend the lifetime of the Paks NPP with addition 20 years, resulting a significant growth in the amount of the SFs. In order to adjust the storage capacity a review of the design was carried out. The structural analysis showed that a number of 703 FSTs could be installed into the same geometry by modifying the charge face structure (CFS). Based on this number the total capacity could be increased by almost 20% compared to the original design. Considering the initial few years of cooling period and applying it for the whole storage facility the heat load could be higher than the design criteria. However, with the rearrangement of the SFs cooled for many years in the FSTs it is possible to solve this issue. The decay heat production of SFs stored for many years decreased to a level at which it is possible for them to be placed in a higher density redesigned vault with the new CFS design. By transferring the older SFs to the higher density vaults there will be enough free positions to place the newer SFs arriving from the NPP. Construction license with the newly increased storage arrangement was issued by the nuclear authority in 2017. The paper describes the design, modelling and licensing process of this capacity enhancement. (author)
[en] The paper describes the strategy adopted by Sellafield Ltd for management of the remaining lifetime arisings of AGR fuel from EDFE reactors. AGR reprocessing operations have completed at Sellafield but fuel will continue to be received, dismantled and consolidated in line with current practice. Spent fuel will be wet stored in existing facilities for an interim period until a disposal facility becomes available, extending fuel storage time from the current 5 years (for buffer storage pending reprocessing) to 80 years. The main safety issues associated with this interim storage strategy are ensuring the long term integrity of the fuel to be stored and the structure of the storage facility. The paper summarises research on fuel corrosion resistance and the pond structure inspection reports. Storage for the interim period requires changes to the operations of facilities and examples of these changes are given. (author)
[en] The one third of power generation in Armenia is from the Armenian Nuclear Power Plant (ANPP). Currently is under operation only second unit of ANPP. The safety of the ANPP is a top priority for the Government of Armenia. Strategy on the Safe Management of Radioactive Waste and Spent Nuclear Fuel and the Action Plan on its implementation was approved by Government Decrees in 2017 and 2019. The source of spent fuel is the ANPP. When its service life is expired, during refueling of the reactor core, fuel assembly is discharged from the reactor core and placed in cell of the Unit № 2 storage pool. Refueling is performed once in a year, when the reactor is shut down, depressurized and cooled down. Following discharge of spent fuel assembly from the reactor core it is tested for leak tightness. In case it is tight, a spent fuel assembly is placed in a cell of the storage pool. In case failed assemblies are detected they are placed in tight casings and stored in them. Following the required storage time (3-5 years), spent fuel assemblies are relocated into the spent fuel storage pool of № 1, where they are stored until reaching the parameters required for their 2 transferring to Dry Spent Nuclear Fuel Storage facility (DSNFSF) of NUHOMS-56 type located on Armenian NPP site. Spent fuel assemblies are placed in Dry Shielding Canister (DSC), which is filled with nuclear purity helium of retained overpressure. The DSC shielding and insulation are provided by massive reinforced concrete Horizontal Storage Module (HSM). Radioactive decay heat caused by DSC and HSM is removed using draught ventilation system, which operation is based on a passive natural convection. There are two buildings of the HSM built on the Armenian NPP site. (author)