Intercomparison exercise on difficult to measure radionuclides in activated concrete—statistical analysis and comparison with activation calculations

This paper reports the results obtained in a Nordic Nuclear Safety Research project during the second intercomparison exercise for the determination of difficult to measure radionuclides in decommissioning waste. Eight laboratories participated by carrying out radiochemical analysis of 3H, 14C, 36Cl, 41Ca, 55Fe and 63Ni in an activated concrete. In addition, gamma emitters, namely 152Eu and 60Co, were analysed. The assigned values were derived from the submitted results according to ISO 13,528 standard and the performance assessments were determined using z scores. The measured results were compared with activation calculation result showing varying degree of comparability.

New methodological approaches in solving certification problem of historical solid radioactive waste sent for burial from Chornobyl Nuclear Power Plant

Two methodological approaches for radioactive waste (RAW) certification used in RAW management systems in Italy and France, are addressed. Their applicability was assessed in solving certification problem of historical waste accumulated at the Chornobyl NPP in comparison with the standard methods recommended by the IAEA. Testing new methodological approaches was carried out on the example of solid RAW (SRW) of operational origin, which were previously studied for the content of 24 radionuclides within their composition. The procedures for testing researchable methods have used the criteria for SRW acceptance for burial valid in SRW Treatment Plant, which met their current provisions and those ones planned for approval. It was established that the use of quantitative criteria applied in the algorithms of studied methodological approaches for radwaste certification can significantly reduce overestimation degree of summary activity of waste packages by way of removing from the list of difficult-to-measure radionuclides, whose presence can be neglected in view of negligible risk of exceeding the activity limits established for them. The methodological approaches addressed in this work allow optimizing radionuclide contents subject to mandatory measurement, or calculated determination of their activity in waste packages, and can be recommended to solve the problems when characterizing ChNPP’s historical waste transported for their final disposal.

IDEA: An Integrated Set of Tools for Sustainable Nuclear Decommissioning Projects

Projects Decommissioning of nuclear installations constitutes an important challenge and shall prove to the public that the whole nuclear life cycle is fully mastered by the nuclear industry. When ceasing operation, nuclear installations owners and operators are looking for solutions in order to assess and keep decommissioning costs at a reasonable level, to fully characterize waste streams (in particular radiological inventories of difficult-to-measure radionuclides) and to reduce personnel exposure during the decommissioning activities taking into account several project, site and country specific constraints. In response to this need, Tractebel Engineering has developed IDEA (Integrated DEcommissioning Application), an integrated set of computer tools, to support the engineering activities to be carried out in the frame of a decommissioning project. IDEA provides optimized solutions from an economical, environmental, social and safety perspective. IDEA is based on the integration of the following computer tools: LLWAA-DECOM, VISIMODELLER/VISIPLAN and DBS. The LLWAA-DECOM module has been developed for the radiological characterization of contaminated systems and equipment. The module constitutes a specific part of more general software that was originally developed to characterize NPP radioactive waste streams in order to assist the Operators when declaring the radiological inventory of critical nuclides, in particular difficult-to-measure radionuclides, to the Authorities. In the case of LLWAA-DECOM, deposited activities inside contaminated equipment (piping, tanks, heat exchangers ...) and scaling factors between nuclides, at any given time of the decommissioning time schedule, are calculated on the basis of physical characteristics of the systems and of operational parameters of the nuclear power plant. The VISIMODELLER tool, a user friendly CAD interface developed to ease the introduction of lay-out areas in a software named VISIPLAN. VISIPLAN is a 3D dose rate assessment tool for ALARA work planning, developed by the Belgian Nuclear Research Centre SCK•CEN. The DBS computer tool has been developed to manage the different kinds of activities that are part of the general time schedule of a decommissioning project. For each activity, when relevant, algorithms allow to estimate, on the basis of local inputs, radiological exposures of the operators (collective and individual doses), production of primary, secondary and tertiary waste and their characterization, production of conditioned waste, release of effluents, ... and enable the calculation and the presentation (histograms) of the global results for all activities together. Based on design and operating data from the Nuclear Power Plant to be dismantled and on the specificities of the country regarding radioactive waste management and disposal routes, IDEA will enable to prepare and manage a decommissioning project, in a sustainable way, leading to a greenfield or a reuse of the nuclear site after decommissioning of the plant. Moreover thanks to the characterization and definition of the optimal waste treatment and conditioning techniques, IDEA contributes to the long term safe management of the radioactive waste.