Nuclear. Cotentin: on the Orano site, the first factory to be dismantled

The recovery site for old waste from silo 130 required the construction of a complete installation. (©DP)

For four years, theNuclear Safety Authority publishes thematic notebooks in an educational information approach on subjects relating to nuclear safety and radiation protection. The latest, released at the end of June 2022focuses on the challenges of dismantling : how to ensure the smooth running of this final phase in the life of a nuclear facility?

Dismantling, explains the ASN, concerns both the evacuation of radioactive substances and waste, operations to dismantle equipment and clean up structures and soils.

About ten nuclear reactors are at this stage, the first being Chooz in the Ardennes the dismantling of which was launched in 2007. There are also research reactors, laboratories and fuel production plants. There are also facilities for the storage and processing of spent fuel and waste, located on the site of The Hague (Channel) and operated by Orano.

New tools developed

Among these, the UP2-400 plant, the first fuel processing plant for first-generation reactors (UNGG), which operated from 1966 to 1998. In 32 years of operation, it processed 5,000 tonnes of fuel from from the gas graphite sector, and 4,500 tonnes from pressurized water reactors. Its decision was pronounced in 2003 and the dismantling decree published in November 2013.

“It contains very irradiating waste, such as technological waste, rubble, earth and sludge, sometimes stored in bulk, without prior sorting. Dismantling therefore takes place in parallel with waste recovery and conditioning operations, which require the implementation of complex and unique engineering processes. »

ASN

The Orano la Hague site includes seven basic nuclear installations, four of which, linked to UP2-400, are being dismantled: one of the liquid effluent treatment stations and the former spent fuel treatment workshop, the Haute oxide activity (HAO) which treated light water fuels, as well as the Elan IIB workshop which manufactured radioactive sources.

“For dismantling, each workshop is divided into several sites. Depending on their activity, we have to develop new tools, new means, which we have to test and validate before moving on to an industrial phase”, indicates the management of Orano. “It is not the same waste, it is not stored in the same way. The principle is to work remotely, with robots in particular. »

UP2-400: 38% progress

“The waste recovery and packaging sites are of particular importance, given the inventory of radioactive substances present and the old nature of the facilities storing them, which no longer meet current safety standards. With significant complexity, due to interactions with the factories operating on the site,” observes the ASN, which is very vigilant about the characterization and qualification of the processes.

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As with all nuclear activities, dismantling takes place over a long period of time. “For UP2-400, the dismantling will last until 2040, then it will be necessary to deconstruct the workshops specially set up for this dismantling. Overall, this will represent an overall budget of 4 billion eurosdue to 200 million per year. At the end of 2021, 38% of dismantling activities had been completed. 800 people work there every day on the site.

Silo 130: the construction site in the industrial phase

One of the emblematic projects undertaken in terms of dismantling concerns silo 130, to the northwest of the site. Its buried containment had been designed for the dry storage of solid waste produced during the stripping of irradiated fuel. It was mined from 1973 to 1981: there are magnesium sheaths, graphite liners, various technological waste, as well as earth and rubble.

A fire in the silo in 1981 forced Orano to drown the solid waste. Thus, the silo today contains solid waste, water used for extinguishing the fire and sludge.

A technically complicated project, including in terms of schedule. It is in fact a complete workshop, ensuring containment, that Orano has set up. All operations are remote controlled. A grapple system will catch the bulk waste, which is then conveyed by a belt, via a connecting tunnel between the silo and the new installation. The waste is then packaged in metal drums and stored under water on the site.

Recovery operations for bulky solid waste began in October 2019, gradually to fully control the recovery and packaging process. “To date, around fifty barrels have been produced and since April, we have entered the industrial phase”, specifies Orano.

For water recovery, a file was submitted to ASN in June. At the bottom, where Orano must take back low-particle waste, video mapping should make it possible to identify the waste. As for the earth and rubble, samples were taken at the end of last year and are being analyzed.

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