Chernobyl Nuclear Power Plant sarcophagus

Chernobyl Nuclear Power Plant sarcophagus
Ukrainian: Укриття Чорнобильської АЕС
The sarcophagus in 2006. The tall chimney is an original part of the reactor building.
Location in Ukraine
Alternative names	Chernobyl Nuclear Power Plant Object Shelter
General information
Status	Deteriorated; succeeded by Chernobyl New Safe Confinement
Type	Confinement shelter
Location	Covering Reactor 4 of the Chernobyl Nuclear Power Plant, within the Chernobyl Exclusion Zone, near Pripyat
Country	Ukraine
Coordinates	51°23′23″N 30°05′57″E / 51.389636°N 30.099033°E / 51.389636; 30.099033Coordinates: 51°23′23″N 30°05′57″E / 51.389636°N 30.099033°E / 51.389636; 30.099033
Construction started	June 1986
Completed	November 1986
Demolished	To partially start in 2017 (estimated)

The Chernobyl Nuclear Power Plant sarcophagus or Shelter Object (Ukrainian: Об'єкт "Укриття") is a massive steel and concrete structure covering the nuclear reactor No. 4 building of the Chernobyl Nuclear Power Plant. It was designed to limit radioactive contamination of the environment following the 1986 Chernobyl disaster, by encasing the most dangerous area and protecting it from climate exposure. It is located within a large restricted area known as the Chernobyl Exclusion Zone. The original Russian name is "Obyekt Ukrytiye" (Объект "Укрытие"), which means "sheltering" or "covering", as opposed to sarcophagus. The sarcophagus locked in 200 tons of radioactive corium, 30 tons of highly contaminated dust and 16 tons of uranium and plutonium. In 1996 it was deemed impossible to repair the inside of the sarcophagus as radiation levels were estimated to be as high as 10,000 röntgens per hour (normal background radiation in cities is usually around 20-50 microröntgens per hour, and a lethal dose is 500 röntgens over 5 hours). A decision to replace the sarcophagus with the New Safe Confinement was taken, and a project to reconstruct the enclosure has since been completed.

The design of the sarcophagus started on May 20, 1986, 24 days after the disaster. Subsequent construction lasted for 206 days, from June to late November of the same year. 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 dug 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.