Currently, the EBR-II reactor is in a safe storage configuration with all primary and secondary systems drained of sodium, a passivation layer consisting of sodium bicarbonate exists on exposed sodium surfaces, and all primary and secondary systems inerted with a cover gas blanket. Full D&D of the facility will be resumed when necessary funding is obtained.

The Experimental Breeder Reactor-II (EBR-II) was shutdown in late 1994 after 30 years of successful operation. The detailed Safe Storage Work Plan describing the final condition of the EBR-II was implemented in October 2000. By that time many important steps had already been performed. Specifically, de-fuelling of the reactor, the design and construction of the sodium process facility and initial sodium processing had taken place. By the end of January 2001 the bulk primary system and secondary system sodium had been processed and packaged in the Sodium Process Facility (SPF) for disposal. Residual sodium was treated by passivation using a moist carbon dioxide treatment method. The objective was to leave all systems in a known, well documented configuration for future decommissioning, to minimize surveillance and maintenance activities and expenditures, to close sodium bearing systems for a minimal 20-year period, and provide recommendations for future reactor designs based upon the operating experiences from the plant.

The work was divided into 3 phases:

Phase I Decommissioning

The initial phase of decommissioning activities was reactor de-fueling, completed in December 1996. De-fueling was initiated in October 1994 and was completed 14 months later, 3 months ahead of schedule. De-fueling included:

• Removal of 637 fuel assemblies from the reactor core,
• Washing sodium coolant from each assembly and drying each assembly,
• Transfer of these assemblies to a hot-cell facility for disassembly and repackaging, and
• Transfer of the spent fuel into an interim storage.

Phase II Decommissioning

The second decommissioning phase was sodium coolant removal and reaction.

By late summer 2000 the secondary sodium coolant had been reacted to a solid sodium hydroxide waste and the primary sodium was being drained. Processing of the primary sodium was completed in March 2001. In addition to the sodium utilized as a EBR-II coolant, 372 tonnes, Argonne also stored the Fermi I NPP FBR primary sodium inventory of 281 tonnes. A total of 653 tonnes of sodium was converted to 1,450 tonnes of solid sodium hydroxide for disposal.

Phase III Decommissioning

The third and final phase of the decommissioning activity was the placement of the reactor and non-reactor systems in a radiological and industrially safe condition. A major component of Phase III was treatment of the residual radioactive sodium remaining within plant system piping and components. The conversion of the exposed residual sodium surfaces to a non-reactive layer of sodium carbonate was accomplished through a passivation process.

The EBR-II decommissioning activities were performed safely, effectively, efficiently and on schedule. Of primary interest are those recommendations stemming from the lessons learned in performing the decommissioning activities.