Demolition of chimney at Italian plant completed

The dismantling of the central chimney at the shutdown Garigliano nuclear power plant in Italy was completed yesterday, Societa Gestione Impianti Nucleari SpA announced. Preparations to demolish the 95-meter-high chimney began in March 2014.

The dismantling of the central chimney at the shutdown Garigliano nuclear power plant in Italy was completed yesterday, Societa Gestione Impianti Nucleari SpA (Sogin) announced. Preparations to demolish the 95-meter-high chimney began in March 2014.

The truncated cone-shaped chimney, made of reinforced concrete, had a diameter ranging between 5 meters at the bottom and 2m at the top (Image: Sogin)

Activities for the chimney demolition began in March 2014. Following system and machinery testing, waterproofing of the areas and consolidation of the structures, decontamination of the inner walls by scarification of the chimney was completed. This scarification work was carried out by a specifically designed and built Italian technology robot, which was guided remotely from the outside. The robot moved from inside the chimney from top to bottom, removing thin layers of lightly contaminated concrete. The decontamination allowed Sogin to demolish the chimney as a conventional structure.

The preparatory works were concluded in August 2016 with the removal of the platform placed on top of the structure, mounted to manage the air flow and support the handling equipment of the scarification robot inside the chimney.

A controlled crushing demolition technique was adopted for dismantling the chimney. Sogin said such a technique "showed the highest safety level and the ability to avoid possible consequences to the neighbouring structures, including the reactor building". Starting from the top of the chimney, the structure has been gradually dismantled, with the resulting materials falling inside the chimney itself.

The demolition works resulted in about 800 tonnes of concrete and 30t of metal. The contaminated material from the scarification totals about 7 cubic meters. This waste has been treated and placed in the on-site interim storage facility.

The Garigliano plant following demolition of the chimney (Image: Sogin)

The old chimney is to be replaced with a new 34-meter-high steel chimney, which will be needed for discharging the gaseous effluents from forthcoming decommissioning activities at the plant. Sogin said the design and technology adopted ensure that there will be no impact on the environment.

Sogin said the value of the activities performed, including construction of the new chimney, will total some €10 million ($12 million).

The Garigliano boiling water reactor was connected to the grid in January 1964 and was shut down in 1982. Decommissioning activities at Garigliano are expected to end between 2024 and 2028.

Italy operated a total of four nuclear power plants starting in the early 1960s, but decided to phase out nuclear power in a referendum that followed the 1986 Chernobyl accident. It closed its last two operating plants, Caorso and Trino Vercellese, in 1990. State-owned Sogin was established in 1999 to take responsibility for decommissioning Italy's former nuclear power sites and locating a national waste store.

Researched and written
by World Nuclear News