ASN Report 2022

Silo 130 Silo 130 is a reinforced concrete underground storage facility, with carbon steel liner, used for dry storage of solid waste from the reprocessing of Gas-Cooled Reactor (GCR) fuels, and the storage of technological waste and contaminated soils and rubble. The silo received waste of this type as from 1973, until the 1981 fire which forced the licensee to flood the waste. The leak-tightness of the water-filled silo is only ensured at present by a single containment barrier consisting of a steel “skin”. Today, the civil engineering structure of silo 130 is weakened by ageing and by the fire that occurred in 1981. The water is therefore in direct contact with the waste and can contribute to corrosion of the carbon steel liner. One of the major risks for this facility concerns the dispersion of radioactive substances into the environment (infiltration of contaminated water into the water table). The leak-tightness of silo 130 is monitored by a network of piezometers situated nearby. 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 phenomena of radiolysis or corrosion (presence of water). These elements contribute to the risks of fire and explosion. The scenario for retrieving and packaging this waste comprises four stages: • retrieval and packaging of the solid GCR waste; • retrieval of the liquid effluents; • retrieval and packaging of the residual GCR waste and the sludges from the bottom of the silo; • retrieval and packaging of the soils and rubble. Orano has built a retrieval unit above the pit containing the waste and a new building dedicated to the sorting and packaging operations. The various works conducted on silo 130 in 2022 enabled the licensee to validate industrial commissioning of the waste retrieval process. Quantitatively, 36 drums of waste were retrieved in 2022, bringing the total number of drums retrieved since the facility started operation in 2021 to about sixty. The licensee is nevertheless encountering numerous difficulties in terms of rates of waste retrieval and equipment reliability, which have a significant impact on the waste retrieval time frame. Waste retrieval has thus been stopped since the end of August 2022 following the rupture of the retrieval rake cable. ASN considers that the licensee must take measures to restore an operating capacity as close as possible to what was planned for at the design stage and must take into account the lessons learned for the other WRP projects. HAO silo and Organised Storage of Hulls The Oxide High Activity (HAO) facility (BNI 80) ensured the first steps of the spent nuclear fuel reprocessing process: reception, storage, then shearing and dissolution. The dissolution solutions produced in BNI 80 were then transferred to the UP2-400 industrial plant in which the subsequent reprocessing operations took place. BNI 80 comprises: • HAO North, spent fuel unloading and storage site; • HAO South, where the shearing and dissolution operations were carried out; • the “filtration” building, which accommodates the filtration system for the HAO South pool; • the HAO silo, in which are stored the hulls and end-pieces (fragments of cladding and fuel end-pieces) in bulk, fines coming primarily from shearing, and resins and technological waste from the operation of the HAO facility between 1976 and 1997; • the Organised Storage of Hulls (SOC) comprising three pools in which the drums containing the hulls and endpieces are stored. In 2022, the licensee continued the operations prior to retrieval of the waste from the HAO silo and implementation of the physical modifications defined on completion of the analysis of hard spots identified during the functional tests of the waste retrieval system. The efforts focused in particular on upgrading the cement encapsulation carriage for fines and resins. Resolution CODEP-DRC-2022-02887 of 15 July 2022 authorised the partial commissioning of the unit for retrieval and packaging of the waste from the HAO silo and the SOC pools in “ECE” drums. The time frames are consistent with the “integrated schedule” of the project transmitted in February 2022 to meet the requirements to keep to the schedule in accordance with resolution 2014-DC-0472 of 9 December 2014, amended. ABSTRACTS – ASN Report on the state of nuclear safety and radiation protection in France in 2022 79 Regional overview of nuclear safety and radiation protection • NORMANDIE •