DOE OSTI2016
Each nuclear facility is different due to their history and there is no rule for choosing a decommissioning strategy. There are three major decommissioning strategies. First, 'immediate dismantling', which means the decommissioning begins immediately after the transfer of waste and nuclear material. Second, 'deferred dismantling strategy', meaning the facility is maintained into a containment zone from thirty to one hundred years before being decommissioned. Finally, 'entombment', referring to the placement of the facility into a reinforced containment until the radionuclides decay and reach a level allowing the site release. When a strategy is decided many factors have to be taken into account. Into a major project such as a reactor decommissioning, there are many smaller projects and the decommissioning strategy can be different among these smaller projects. Very often, some entry data are not perfectly known, for example, the dosimetric activity has not been updated through time or after specific events. Because of uncertainties and/or hypothesis existing around projects and their high level of interdependency, global solutions are a good way to choose the best decommissioning strategy. Especially since each entry data has consequences on output results whether it is on costs, cumulated dose, waste or delays. Also the dose, delays or waste management, all have impact on costs. To obtain an optimal scenario into a special environment, it is necessary to deal with all these items together. This global solution can be implemented thanks to simulation in dedicated software which helps define the global strategy, optimize the scenario, and prevent contingencies. For a specific environment, when many scenarios have been developed and simulated, sensitivity studies are really important to choose the optimal decommissioning strategy. Sensitivity studies can be done with simulation tools by comparing results of scenarios directly into the software. This comparison helps to choose the optimal scenario according to which output data is considered as key determinant. (authors)
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗