Methodology for identification of conditionally released materials from decommissioning using the OMEGA code - 59175

The nuclear facility decommissioning process is characterized by production of large volumes of radioactive materials to be managed. The materials with radioactivity slightly above the defined unconditional clearance levels could be released conditionally for a specified industrial application in accordance with developed scenario ensuring that the limits for radiation exposure of workers and public will not be exceeded. The paper presents the methodology for identifying and assessment of the physical and radiological parameters of material items suitable for using in defined scenarios of conditional reuse of materials resulting from the decommissioning process. The calculation of mentioned parameters is done by using the analytical code OMEGA with implemented calculation stream for evaluation the conditional release process. The necessary input parameters for the OMEGA code are maximum concentrations of each radionuclide in the conditionally released materials which do not cause the doses above the limit values for the possible scenarios of further use of materials outside the nuclear site. The examples of such scenarios are assessed and presented in other related papers proposed for the ICEM conference (e.g. papers ICEM2011- 59120 or ICEM2011-59128). Based on the inventory database of physical and radiological characteristics of decommissioned facility, the calculation algorithm separates the relevant material items with activity concentrations between unconditional and conditional clearance levels. The amount, material composition and radioactivity of such material items are declared as output parameters of the calculation and are also discussed in the paper. Such data could be used as one of the bases in the benefit analysis of potential application of conditional release within the frame of decommissioning waste management. (authors)