Partial dismantling of the Avogadro RS-1 reactor

The Avogadro RS-1 reactor was a water-moderated and -cooled pool reactor of the MTR (materials testing reactor) type that operated from 1959 to 1971 at different thermal power levels, rising to a maximum of 7 MW(th) towards the end of that period. The dismantling operations began in July 1977 and were virtually completed by September 1978. The work was carried out on the basis of programmes and procedures approved in advance by the CNEN (Italian National Nuclear Energy Committee), under the constant supervision of the Sorin and Fiat health physics services. Before dismantling, some of the components of the reactor systems were put back into service. When the underwater exposure rate had been measured to determine the most suitable method of moving and chopping components for insertion into shielded containers, the components were dismantled and cut up into sections less than one metre in size. The work was carried out for the most part under water, either by means of a hydraulic chopper controlled from the side of the pool, or by divers who carried out the mechanical disassembly and cutting with arc welders in the pool itself. The containers holding the dismantled components were transferred to a store set up in a suitable area of the Sorin concern. At the end of the operations the pool was emptied and its inside surface decontaminated until the values obtained were such that access without any restriction from the health physics standpoint could be permitted. The dismantling process, carried out without any particularly sophisticated devices, proceeded smoothly and gave rise to no unforeseen difficulties. The whole-body dose absorbed by occupationally exposed personnel was 0.0175 man.sievert, and the individual radiation doses lay well below the maximum permissible levels