The Decommissioning of the ENEA RB3 Research Reactor in Montecuccolino

The ENEA RB3 reactor was a 100 Wth research installation owned and operated by ENEA, in its center of Montecuccolino near Bologna, from 1971 to 1989. It consisted of a cylindrical aluminium vessel, about 4.3 m high and 2.9 m in diameter, which could host various types of fuel elements suspended from the top of a special adjustable rack and submerged into moderating and cooling heavy water. Principal aim of the reactor was to provide neutronics data for the CIRENE NPP, a SGHWR that was being designed and then partially built in Latina starting from 1979. The specific RB3 core, surrounded by a graphite reflector and housed inside a concrete biological shielding, allowed to test easily very different fuel element configurations by changing their pitches and by regulating the heavy water level inside the vessel. The reactor design, similar to that of the ZED-II Canadian research facility, was originally developed by CEA for its Aquilon facility in Saclay in 1956; in fact, through a special arrangement between ENEA and CM, parts of the Aquilon facility were ultimately donated to ENEA at the end of the 60s for the construction of RB3. In 1989, the RB3 reactor was shut down, and in the late 2010 ENEA received by ministerial decree the authorization to its dismantling, with the aim of reaching the "green field" status and with the unconditional release of its building, which is actually owned by the University of Bologna. The dismantling activities started in May 2013 and were concluded at the end of 2014; after that, a campaign for the radiological characterization of the building was initiated and concluded in June 2015. Now, all the necessary site characterization activities are being conducted with the aim to present the results declaring the "green field" status before the end of 2017. This paper will present the three main pillars of the decommissioning of RB3, namely the strategy and methods for the dismantling, the strategy and methods for the radiological characterization of the building, and finally the strategy and methods for the radiological characterization of the site. The radionuclide limits imposed by the Italian Regulatory Body, together with the challenges encountered so far will be likewise shown and described.