ASN Report 2018

NORMANDIE REGIONAL OVERVIEWOF NUCLEAR SAFETY AND RADIATION PROTECTION Orano Cycle has built a retrieval unit above the pit containing the waste and a new building dedicated to the storing and packaging operations. ASN had set 1 July 2016 as the start date for all the waste retrieval operations. In the light of the justifications provided by Orano Cycle concerning the technical difficulties encountered, ASN pushed back the operations start date to 30 April 2018. Orano Cycle, however, did not meet this new regulatory deadline, even though the ventilation system of the retrieval and packaging facilities was actively connected in 2018 and the tests important to safety prior to entry of the facilities into active service were also started in 2018. After noting during an inspection that waste retrieval had effectively not yet started in April 2018, and taking account of the new technical and organisational difficulties encountered during the tests, ASN asked Orano Cycle to propose a realistic deadline for starting waste retrieval, explicitly defining the margins on the critical path and the margins for residual risks, with justifications. The examination of the authorisation applications concerning the first retrieval phases continued in 2018. The old fission product solutions stored in the SPF2 unit of the UP2‑400 plant The licensee has chosen cold crucible vitrification for the packaging of the fission products resulting from the reprocessing of fuels from the Gas-Cooled Reactor series and containing molybdenum (UMo FP) in particular. The package thus produced is a Standard UMo Vitrified Waste Package (CSD-U). Operational application of cold crucible vitrification was authorised by resolution of 20 June 2011. Unforeseeable problems were encountered during its development and implementation. Consequently, Orano Cycle was unable to meet the end-of-retrieval deadline set at 31 December 2017 by ASN resolution of 26 June 2012 and asked for this deadline to be pushed back until the end of 2019, on the basis of the CSD-U package production rate in 2018. This application is currently being reviewed by ASN. 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 phenomena of radiolysis or corrosion (presence of water). These elements contribute to the fire and explosion risks. 70  ASN report on the state of nuclear safety and radiation protection in France in 2018