Progress in Nuclear Science and Technology Volume 4 (2014) pp. 849-853 © 2014 Atomic Energy Society of Japan. All rights reserved. ARTICLE Assessment of potential options for conditional reuse of materials from nuclear installation decommissioning Matej Zachar a* , Vladimir Daniska a , Frantisek Ondra a , Jozef Pritrsky a and Vladimir Necas b a DECOM, a.s., Sibirska 1, 917 01 Trnava, Slovakia; b Slovak University of Technology in Bratislava, Faculty of Electrical Engineering and Information Technology, Ilkovicova 3, 812 19, Bratislava, Slovakia The nuclear installation decommissioning process is characterized by production of large amount of radioactive materials to be managed. The materials with radioactivity slightly above the unconditional release levels could be released conditionally for a specific industrial application in accordance with beforehand developed and evaluated scenario. This evaluation has to ensure that the limits for radiation exposure of workers and the public will not be exceeded. The paper gives an overview of representative options (scenarios) for reuse of conditionally released steel materials and recycled concrete from decommissioning. The main aim of the paper is to present the developed complex methodology for assessment of these options and its implementation to the relevant calculation tools. The first step in the methodology procedure is the identification of the activities which could lead to the exposure of the public or workers. For defined activities the external exposure of workers and the public is evaluated using the Visiplan 3D ALARA Planning tool. The internal exposure analysis is mainly based on the models for migration of radionuclides in the environment calculated in the GoldSim code. Based on the results of exposure evaluation, the critical exposure pathway is determined and conditional release levels of individual radionuclides are derived. Finally the amount and radioactivity of materials from decommissioning, fulfilling the limits for conditional reuse, are calculated in the decommissioning planning code OMEGA [1]. Keywords: decommissioning; conditional release and reuse; external exposure; internal exposure; conditional release levels; Visiplan 3D ALARA; GoldSim; OMEGA code 1. Introduction 1 As a result of decommissioning activities a wide range of material (waste) types with various physical, chemical, radiological and toxic characteristics arises. All the activities done in the decommissioning materials or waste management process are aimed to achieve:  Release the materials to the environment for reuse;  Safe isolation of the non-releasable materials from the environment within the radioactive waste (RAW) repository barriers. The releasing process is based on the concept of triviality of exposure, generally taken to mean that radiation risks to individuals and collective radiological impact, caused by the released material, is sufficiently low. In quantitative terms, the mentioned state is related to the stipulation that the effective dose expected to be incurred by any member of the public due to the released materials is of the order of 10 μSv or less during one year. Collective effective dose (sum of all of the individual doses to members of the public) is proposed *Corresponding author. Email: zachar@decom.sk to be lower than 1 manSv/year [2,3]. Internationally recommended principle for dose constraints 10 μSv/year (individual effective dose) / 1 manSv/year (collective effective dose) [3] creates a basis for derivation of unconditional release levels. The unconditionally released materials could be reused in the environment without any restriction from radiological point of view. On the other hand, there is a possibility to release the materials conditionally i.e. for specific application but the dose constraint 10 μSv/year has to be followed. The dose constraint could be higher e.g. Slovak legislation [4] defines the limit 50 μSv/year considering specific conditions. The definition of specific options for conditional reuse of materials followed by their assessment aimed to demonstrate the applicability of this concept is the main goal of the research project CONRELMAT (CONditional RELease of MATerials). Its main features are discussed in this paper. DOI: 10.15669/pnst.4.849