Decom (Slovakia)

The paper is focused on the decommissioning process from the point of view of steam generator dismantling. A brief description of the steam generator (used in nuclear power plants with VVER 440 type reactor) and used computer code VISIPLAN 3D ALARA are given. The main part deals with the created model and dismantling strategy together with variable input parameters — decay time and decontamination. The obtained results — external exposure of workers and the influence of time and pre-dismantling decontamination — are studied. Also detailed analyses of every dismantling step considered are presented.

The aim of this contribution is development of methodology for verification of selected input calculation data (performance unit parameters, work group structure, and duration of time-dependent activities) of the OMEGA Code in the individual PSL (Proposed Standardised List) structure parts.

This paper describes the results of a survey and study performed for the European Commission on “Regulations Governing Radioactive Waste Disposal in EU Countries”. Its main purposes were to provide a survey of the regulations governing the disposal of all forms of radioactive waste in all EU Members States and, based on this study, to consider the potential for harmonization in different regulatory areas. Three key parts of the study are presented and the results discussed: collection and assessment of national data, including its verification by national stakeholders, application of multiattribute analysis methodology to identify optimal waste classification scheme and a workshop of national authorities regulating disposal of radioactive waste. For five determined regulatory issues, the workshop carried out a “strengths, weaknesses, opportunities and threats” (SWOT) analysis of the impacts of harmonization. Opinions expressed in the paper are those of the authors and do not represent the EC’s official position.

In 1999 was issued commonly by EC, IAEA and OECD the document “A Proposed Standardised List of Items for Costing Purposes in the Decommissioning of Nuclear Installations” (PSL). The main aim of this document was to establish a standard platform for structure of presented decommissioning costs. The decommissioning costs calculated in various projects have in general different structure and for presenting the decommissioning costs in PSL structure, additional recalculation or rearrangement of data are needed. This can increase the uncertainty of data or it is not sure if they really reflect the cost defined in the PSL structure. The paper describes a newly developed cost calculation code, which respect the PSL structure. The calculated costs data are compatible with the standardised structure. The code is intended to use for decommissioning planning of a NPP with a non-standard radiological situation, shutdown after an accident For this purpose the code has an integrated material and radionuclide resolved radioactivity flow control system in calculation process which enables a direct calculation link between the input material and radiological inventory data and the calculated costs and other decommissioning parameters for increasing the accuracy of calculated data. The code has an integrated cost allocating system for generating of user defined working breakdown structure of the decommissioning project with allocated costs calculated in PSL structure. The working breakdown structure can be on-line optimised using the standard Microsoft Office Project Planning tool software.

Abstract Packages of the non-standard radioactive waste have been, in present conditions of the Slovak Republic, defined as packages intended to be dispose by the producer and originally not covered by “the limits and conditions” of the Mochovce near surface repository, particularly waste acceptance criteria concerning the form of waste. Wastes cemented directly (homogeneous) to standard concrete containers reinforced by metal fibres (FRCs) or conditioned into 2001 drums before (heterogeneous: drums are inserted into FRCs and the FRCs void spaces are filled by cement mortar) were originally the only acceptable radioactive waste form in Mochovce repository. However, there has been an intention to dispose another, so-called “non-standard” types of waste: large metal pieces of waste transported and placed directly into repository vaults (i.e. cut into dimensions of individual vault). Second types of non-standard waste have been: dewatered spent ion exchange resins and storage tanks bottom sludge in drums, inserted into FRC with subsequent backfilling by cement mortar. Third group of these is represented by incinerator ashes in drums inserted to FRC directly or after compaction, again with subsequent backfilling of FRCs void spaces. As an answer for this challenge, the ALARA approach has been applied for pre-disposal management optimization of large metal pieces of waste. Four examples of waste arising from the Slovak decommissioned plant A-1 have been evaluated for various options of its management. This step is predominant to achieve a decision concerning disposal of the latter kind of waste. Regarding the disposal of mentioned dewatered waste and incinerator ashes in FRC, a new model has been applied to the assessment of long-term behavior of source term in the repository safety analyses. The new approach is sensitive to the form of waste package on the contrary to the source term model applied heretofore.