Sodium removal and decontamination process and decommissioning considerations for the PFBR components

The Prototype Fast Breeder Reactor (PFBR) is a sodium cooled pool type reactor of 500 MWe capacity. The reactor is being designed at IGCAR, Kalpakkam, India. It is planned to construct the reactor at Kalpakkam. In the PFBR plant Nuclear Steam Supply System (NSSS) components are either wetted with primary sodium or secondary sodium or some time both. Sodium cleaning is to be done before undertaking any maintenance work or disposal. The radioactivity of the primary sodium is significant compared to the secondary sodium. In this paper, primary sodium cleaning and decontamination of the components planned for PFBR are discussed. The choice of hard facing materials for NSSS components are also discussed. Sodium Removal: During the operation of the reactor there are two types of components, which are to be cleaned from sodium. These are 1) Core components and 2) Primary components. The location of the facility for sodium cleaning in the nuclear island is shown. The core components are handled by fuel handling machines where as the primary components are handled by respective flask. The components that are to be decontaminated are removed from the reactor when the reactor is in shutdown condition. The handling of the core components is based on fixed time duration and interval in the reactor. For the primary components, it is as and when required. The core component is not meant for decontamination but for reprocessing and the primary component needs to be decontaminated. The cleaning time of the core component is to be minimum and to be completed during the fuel handling campaign, which is 20 days. For the primary component, the cleaning of sodium can be done during reactor operation as well as shutdown condition. These considerations are taken during conceptual design stage of the reactor to evolve better design considering safety, economy, safe-disposal of the components and safe decommissioning of the plant. The sodium cleaning system has the following design features. A schematic flow sheet of the design features is given. The main objectives are: Minimize sodium sticking on the component. Safe operation. Minimum quantity of waste generation. Fast cleaning. Effective cleaning. No damage to the component