Reactor dismantling

Status: Ongoing
Period: 2000-2025

 

The core of the plant, were energy was produced from a nuclear source, is called nuclear island. It is the most difficult component to dismantle, since it contains the highest levels of residual radioactivity of the plant. The nuclear island consists of the confinement sphere of the reactor building, which, in turn, contains the fuel pool, the vessel (cylindrical container containing the nuclear reactor), the secondary steam generators, the cylindrical structure and all the accessories, systems and components to allow nuclear reaction and the removal of thermal energy (steam) from the reactor to the turbine. The nuclear island is annexed to the turbine building containing the turbo-generator and all the components of the thermal cycle. The first operations after the plant was halted in 1982, were: drainage of the reactor’s hydraulic circuits, removal of fuel elements and emptying of the fuel pool. In the period 1996-1998, the radioactive resins used in the water treatment of the thermal cycle for the BWR plant were conditioned. Sogin’s first operation, after acquiring the plant ownership in 1999, was the reclamation of reactor and turbine from asbestos. The operations carried out between 2008 and 2010 have produced waste containing asbestos; such waste was treated through super-compaction and then stored in the interim storage facilities of the plant. The vessel, which is the container where the nuclear reaction occurred, is located within the reactor building. The dismantling activities for the vessel are highly complex, due to the radioactivity level within the various components and the logistic restraints of the operations. Some operations will be performed under heads of water to ensure effective protection against ionizing radiations. The works will be divided in different stages:

  • Equipment restoration works, restoration of coatings, vessel flooding system and reactor canal. This stage also includes removing the materials in the reactor canal and in the upper part of the vessel (Premises L34 and L42).
  • Vessel opening and removal of radioactive materials and equipment used during the plant operation period and located in the upper part of the vessel.
  • Removal and dismantling of lower internals under heads of water.
  • Dismantling of vessel and primary circuit.
As far as the preliminary activities are concerned, the restoration of flooding systems for the pool and the canal are expected in 2019; such systems are necessary to implement the flooding operations. In June 2018, the canal of the reactor was opened, the biological screen was removed and immediately restored to access the vessel. This allowed the full recovery of the equipment and materials remained in the vessel after the custodial measures implemented in the early Nineties.