ASN Report 2017

429 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 15  - Decommissioning of Basic Nuclear Installations BNI 80 comprises five facilities: ཛྷ ཛྷ HAO North, spent fuel unloading and storage site; ཛྷ ཛྷ HAO South, in which the shearing and dissolution operations were carried out; ཛྷ ཛྷ the “filtration” building, which accommodates the filtration system for the pool of the HAO South facility; ཛྷ ཛྷ the HAO silo, in which are stored the hulls and end-pieces (fuel element cladding and ends) in bulk, fines coming essentially from shearing, resins and technological waste from operation of the HAO facility from 1976 to 1997; ཛྷ ཛྷ the SOC (Organised Storage of Hulls) comprising three pools in which the drums containing the hulls and end- pieces are stored. FUNDAMENTALS The nuclear safety issues associated with silo 130 Silo 130 was designed and built in compliance with the nuclear safety requirements in force in the 1960’s. The structure of the silo 130 civil engineering is today weakened by ageing and by the fire of 1981. Furthermore, the waste, which was initially stored dry, is now submerged in a large volume of water resulting from the extinguishing of the 1981 fire. The water is therefore in direct contact with the waste and can contribute to the corrosion of the carbon steel lining, which today is the sole containment barrier. One of the major risks therefore concerns the dispersion of radioactive substances into the environment (infiltration of the contaminated water into the water table). Another factor that can compromise the safety of silo 130 is linked to the nature of the substances present in the waste, such as magnesium, which is pyrophoric. Hydrogen, a highly inflammable gas, can also be produced by the phenomenon of radiolysis or corrosion (presence of water). These elements contribute to the fire and explosion risks. Grab SCHEMATIC OF RETRIEVAL AND PACKAGING OF THE WASTE FROM SILO 130 Harrow Piezometer Docking of a shielded enclosure Hermès/Mercure tower Reception unit Drum preparation station Filling and quantification unit Siding Elevator UNGG and miscellaneous technological waste Soil and rubble 1,400m 3 of effluents Shuttle system Drum docking station Drum filling station Transfer Silo 130