Reply #254: Chernobyl sarcophagus

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Construction of the Chernobyl sarcophagus.

The first task before construction started was to build a cooling slab under the reactor to prevent the hot nuclear fuel from burning a hole in the base. Coal miners were called up to dig the necessary tunnel below the reactor and by June 24, 1986 four hundred coal miners had built the 168 metre (551 ft) long tunnel. When the building became overly radioactive it became impossible to directly screw down the nuts and bolts or apply any direct welding to the sarcophagus, so this work was done by robots.

The seams of the sarcophagus, however, were not properly sealed. The entire construction process consisted of eight stages: clearing and concreting of territory around reactor unit 4, erection of initial ferro-concrete protective walls around the perimeter, construction of separation walls between units 3 and 4, cascade wall construction, covering of the turbine hall, mounting of a high-rise buttress wall, erection of supports and installation of a reactor compartment covering and finally the installation of a ventilation system.
More than 400,000 m3 of concrete and 7,300 tonnes of metal framework were used during the erection of the sarcophagus.

From Wikipedia here http://en.wikipedia.org/wiki/Chernobyl_Nuclear_Power_Plant_sarcophagus

The old sarcophagus will be replaced.

On September 17, 2007, it was announced that a new steel containment structure named the New Safe Confinement (NSC) would be built to replace the aging and hastily-built sarcophagus that currently protects reactor unit 4. The project, financed by an international fund managed by the European Bank for Reconstruction and Development (EBRD), will be designed and built by the French-led consortium Novarka, which includes the companies Bouygues and Vinci. Novarka will build a giant arch-shaped structure out of steel, 190 m (623 ft) wide and 200 m (656 ft) long to cover the old crumbling concrete dome that is currently in use.

This steel casing project is expected to cost $1.4 billion (£700 million, €1 billion), and expected to be completed in 2013.<9> A separate deal has also been made with the American firm Holtec to build a storage facility within the exclusion zone for nuclear waste produced by Chernobyl.

From Wikipedia here: http://en.wikipedia.org/wiki/Chernobyl_Nuclear_Power_Plant