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INSIDER is an EU Horizon 2020 research project, within the topic NFRP-7 of the EURATOM programme, that aims to develop and validate a new and improved integrated characterization methodology and strategy for the nuclear decommissioning and dismantling operations (D&D) of nuclear power plants, and post-accidental land remediation of nuclear facilities under constrained environments. In line with this general objective, the definition and implementation of the practical considerations surrounding the radiological characterization of nuclear/radioactive facilities subject to a D&D programme is under development.. In-situ measurements are key for this radiological characterization. However, in some cases these measurements have to be carried out under constrained conditions, which poses some challenges to their realization. A constrained environment is a general term that includes all types of environment that hinder the choice of a non-destructive in-situ measurement method. In the context of this paper, it is applied to different situations: radioactive levels of the area to be characterised, difficult accessibility of this area, type and properties of the materials contained in it, as well as the possible presence of other environmental hazards, such as asbestos, chemical and/or organic/biological ones. In this context, an analysis of the suitability of existing methodologies for in-situ measurements in constrained environment is being carried out. The first step to accomplish this task is to describe the constrained environments that could appear in the different nuclear/radioactive facilities and their respective challenges. This paper includes a description of the different constrained environments, showing their corresponding challenges and a classification of the constraints, and it provides a series of tables linking the installations and areas inside them with the different constraints that appear. In the case of the radioactive constraints, a description of the expected level of their impact depending on the different D&D steps also appears. [ABSTRACT FROM AUTHOR]

In this paper, in-situ radiological characterisation by means of non-destructive techniques is studied and analysed in the context of the different constrained environments (identified as radioactivity, materials, accessibility and other hazards) that may be encountered in the nuclear facilities undergoing decommissioning and dismantling. As a complement to a previous paper (Aspe et al., 2020), the present one gives a global guidance to assist with the decision making process regarding the selection of in-situ measurement techniques that could be applied in such constrained environments. In addition, from the definition of the investigation objectives, and for each one of the most common in-situ measurement techniques, a brief description is given about the impact of the above constraints and how to integrate them onto the system definition, including the experimental design, the mechanical integration and the data management, to properly define the best radiological characterization methodology. Moreover, complementing this general view, all the phases – from initial to final – of a D&D programme were taken into account to provide basic recommendations, together with some particular dispositions, for the appropriate implementation of the chosen instruments. Strengths and weaknesses of the common detectors used for the different in-situ measurement techniques, as well as their recommended applications in nuclear facilities are also outlined. • Analysis on in-situ radiological characterisation by means of non-destructive techniques under constrained environments. • Guidance to assist with the decision for the selection of in-situ measurement techniques under constrained environments. • Description of the impact of the constraints and its integration to define the radiological characterization methods. • Provision of basic recommendations for the implementation of the chosen instruments. • Strengths and weaknesses of the common detectors used for in-situ measurement and their recommended applications. [ABSTRACT FROM AUTHOR]