atw 2018-05v6

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atw Vol. 63 (2018) | Issue 5 ı May DECOMMISSIONING AND WASTE MANAGEMENT 316 FA skeleton or damages to the foot and head pieces or even certain kind of debris can be accommodated by the Quiver. In contrast to the regular dispatch and loading of spent fuel assemblies under water in the spent fuel pool, the dispatch of the Quiver is performed outside the spent fuel pool on the reactor floor. This approach is motivated by the use of a much simpler technology and increase in process stability, than it would be required if processing and especially drying and welding is done under water in the spent fuel pool. This also yields an increase in process stability. However, this approach requires some addi tional equipment especially in terms of shielding. Figure 4 describes the dispatch i.e. the drying of the fuel and the closure of the Quiver by means of welding in general. The dispatch of a Quiver is assumed to last not longer than one week and results in a collective dose of less than 3,7 mSV including independent inspectors. The Quiver for the PWR cask CASTOR V/19 has received its Type B transport license in spring 2017 and its first storage license at an interim storage facility of a German NPP is expected in spring 2018. However, the first hot loadings and internal transport between different blocks of a multi-block NPP already took place in summer and fall 2016, respectively. Conclusion With the development of the new CASTOR® geo cask system GNS provides state-of-the-art high capacity dry storage cask system for costumers worldwide. In Combination with the newly developed GNS IQ Quiver system, it provides a comprehensive solution for the dry storage of spent UOX fuel, MOX fuel and even damaged fuel. Authors Linus Bettermann Roland Hüggenberg GNS Gesellschaft für Nuklear- Service mbH Frohnhauser Straße 67 45127 Essen, Germany Optimal Holistic Disposal Planning – Development of a Calculation Tool – Johannes Schubert, Anton Philipp Anthofer and Max Schreier 1 Optimisation potential of disposal planning The expected volume of radioactive waste from dismantling of nuclear facilities in the forthcoming scope and the opening of the Konrad disposal requires an optimised planning of the removal of radioactive waste. For the treatment of radioactive raw waste, with negligible heat generation, different conditioning processes are available. Thereby different waste volumes and masses with different properties can result even from the same raw waste. For final storage, each container has to be filled completely according to the repository conditions of the approved repository site Konrad. There are different variants available to combine the number of barrels and type of container. For example if 100 barrels should be packaged into ten containers there are 1.7x10 13 possibilities of combination if the type of container is chosen before. In addition there are variants of container load with bulk material and huge possibilities how components can be fixed in different types of container. These packaging variants can also be combined. For each variant, compliance to the final storage conditions regarding to the criteria radiology, material, volume and mass must be checked. Furthermore there are boundary conditions like missing places for | | Fig. 1. Workflow of calculation for optimisation of repository container packaging. handling, missing conditioning facilities or design of the site for using only specific containers. An optimisation can be realised according to the parameters repository volume, radiological utilization of the containers, exposure time and container costs. Moreover an optimisation of container loading requires a comparison of the loading variants regarding to the optimisation parameters. An optimisation of disposal and packaging planning saves repository volume, time, costs and exposure time for the staff. Therefore it is indispensable for an integrated disposal planning in the forthcoming volume [1]. Accordingly, for existing waste, all conditioning and loading variants must be calculated with all criteria like radiology, mass, volume, exposure time and costs. A combination of different loading variants results in iteration loops to find an optimal solution. This workflow is shown in Figure 1. For the planning of logistics, handling and shielding for determining the dose rate for the executive staff in individual handling steps, established simulation programs are available. The consideration of the change of Decommissioning and Waste Management Optimal Holistic Disposal Planning – Development of a Calculation Tool – ı Johannes Schubert, Anton Philipp Anthofer and Max Schreier
atw Vol. 63 (2018) | Issue 5 ı May | | Fig. 2. Parts of disposal planning, which can be replaced by a calculation tool. waste properties by conditioning processes and the possible combinations of packaging variants resulting therefrom are currently calculated manually. This complex process can be carried out by a calculation tool. With the data obtained at the removal planning, the calculation tool can carry out the planning and optimisation of conditioning and packaging and supports a repository documentation. Therefore the calculation tool supports the planning, optimisation and calculation of packaging according to the final storage conditions and prepares and simplify the repository documentation. This workflow is shown in Figure 2. 2 Characteristics of packaging planning During the post-operational phase of a nuclear installation, dismantling can be planned. This implies the planning of the dismantling as well as the planning of conditioning and packaging of the radioactive waste with a final disposal documentation. When disassembling, statements about the properties of the waste can be made. The required conditioning processes are dependent of the material properties. These properties such as volume, mass, state of matter and flammability will be changed by conditioning processes. For example, by high-pressure compression, the volume of raw waste can be reduced by up to 80 %, using incineration a reduction by 98 % can be achieved and by a combination of high-pressure compression and incineration, the waste can be reduced by up to 99 % [2]. By reducing the volume, the radioactivity is concentrated. Depending on raw waste and conditioning process, different volumes of radioactive waste with different properties result. This is crucial for packaging planning. The needed parameters for final storage of the waste results of material analyses and calculations. For all conditioning processes a qualification is necessary. Therefore evidences for the realization of the conditioning according to the given restrictions and corresponding conditioning systems at the site are needed. Moreover, there are various types of containers available in various categories for the final disposal packaging of radioactive waste. Furthermore, restrictions in terms of mass, volume, radiology and other waste properties are given in the final disposal conditions [3]. These restrictions must be checked for each container. The evidence for the permissibility of the used containers is also required. This could be implemented by manufacture certificates and handling instructions. Further influencing factors for choosing the type of container can be given by local boundary conditions of the site. Equipment for handling of only a specific type of container without the possibility to adapt the transport system to another type of container can be such an example. The available storage area inside of a site can be a logistic challenge which has to be accounted. Compliance to the transport regulations has to be given at every time inside the site and during transport. These restriction parameters for packaging which are necessary to be taken into account by a calculation tool for holistic waste management planning are shown in Figure 3. 3 Development of the calculation tool The calculation tool has a modular structure. In individual modules, the conditioning methods are determined, the change in waste properties such as volume and mass is calculated, the locally available conditioning procedures are determined and compared with the required procedures, loading time and equivalent dose are estimated and the compliance of the disposal conditions regarding volume, mass and radiology is checked. The modules are illustrated in Figure 4. From the calculation results of the individual modules, the optimal loading variant is determined and entered into the waste data sheet in accordance with the selected optimisation parameter like repository volume, loading time, container costs, volume utilization of the last container or radiological utilization. This is realised by the main module, where all information from the separate modules are evaluated. The user interface of the developed calculation tool consists of an input mask for waste-, conditioning- and container data and an output, where the optimal loading variant is described. In addition, a waste data sheet is created, where all information determined by the calculation tool are inserted automatically. The individual details, e.g. for description of the included material or dose rate are | | Fig. 3. Characteristics of packaging planning which must be accounted by a calculation tool for holistic disposal planning. DECOMMISSIONING AND WASTE MANAGEMENT 317 Decommissioning and Waste Management Optimal Holistic Disposal Planning – Development of a Calculation Tool – ı Johannes Schubert, Anton Philipp Anthofer and Max Schreier
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