, image = Chernobylreactor 1.jpg , caption = The sarcophagus in 2006. The tall

chimney A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typ ...

is an original part of the reactor building. , location = Covering Reactor 4 of the Chernobyl Nuclear Power Plant, within the

Chernobyl Exclusion Zone The Chernobyl Nuclear Power Plant Zone of Alienation, Belarusian: Хона адчужэння Чарнобыльскай АЭС, ''Zona adčužennia Čarnobyĺskaj AES'', russian: Зона отчуждения Чернобыльской АЭС, ...

, near Pripyat , location_town = , location_country = Ukraine , coordinates = , start_date = June 1986 , completion_date = November 1986 , demolition_date = TBC 2020 , status = Deteriorated; succeeded by

Chernobyl New Safe Confinement The New Safe Confinement (NSC or New Shelter, rarely Arka) is a structure put in place in 2016 to confine the remains of the number 4 reactor unit at the Chernobyl Nuclear Power Plant, in Ukraine, which was destroyed during the Chernobyl disas ...

, cost = , references = , map_type = Ukraine , map_caption = Location in

Ukraine Ukraine ( uk, Україна, Ukraïna, ) is a country in Eastern Europe. It is the second-largest European country after Russia, which it borders to the east and northeast. Ukraine covers approximately . Prior to the ongoing Russian inva ...

, building_type = Confinement shelter , height = , alternate_name = Chernobyl Nuclear Power Plant Shelter Structure The Chernobyl Nuclear Power Plant sarcophagus or Shelter Structure ( uk, Об'єкт "Укриття") is a massive steel and concrete structure covering the

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...

number 4 building of the Chernobyl Nuclear Power Plant. Currently the sarcophagus resides inside the

New Safe Confinement The New Safe Confinement (NSC or New Shelter, rarely Arka) is a structure put in place in 2016 to confine the remains of the number 4 reactor unit at the Chernobyl Nuclear Power Plant, in Ukraine, which was destroyed during the Chernobyl disas ...

structure. The New Safe Confinement is designed to protect the environment while the sarcophagus undergoes demolition and the nuclear cleanup continues. The sarcophagus was designed to limit

radioactive contamination Radioactive contamination, also called radiological pollution, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirab ...

of the environment following the 1986

Chernobyl disaster The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the No. 4 reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. It is one of only two n ...

, by encasing the most dangerous area and protecting it from climate exposure. It is located within a large restricted area known as the

. The original Russian name is (), which means or , as opposed to sarcophagus. The sarcophagus locked in of radioactive lava-like corium, of highly contaminated dust and of

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

and

plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exh ...

. By 1996 the structure had deteriorated to the point where numerous stabilization measures were required. Internal radiation levels were estimated to be as high as per hour in certain areas (normal

background radiation Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources. Background radiation originates from a variety of source ...

in cities is usually around per hour, and a lethal dose is over 5 hours). It was decided that the sarcophagus would be replaced with a

, the construction of which was completed in 2017.

Construction

The design of the sarcophagus started on 20 May 1986, 24 days after the disaster. Subsequent construction lasted for 206 days, from June to late November of the same year. Due to high radiation levels, it was impossible to directly screw down the nuts and bolts or apply any direct welding to the sarcophagus, so this work was done remotely where possible. The seams of the sarcophagus, however, could not be fully sealed. The entire construction process consisted of eight stages: clearing and concreting of territory around reactor unit 4, erection of initial

reinforced concrete Reinforced concrete (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low ultimate tensile strength, tensile strength and ductility are compensated for by the inclusion ...

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 A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall. Buttresses are fairly common on more ancient buildings, as a means of providing support to act against the lateral (s ...

wall, erection of supports and installation of a reactor compartment covering and finally the installation of a ventilation system. More than of concrete and 7,300

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

s of metal framework were used during the erection of the sarcophagus. The building ultimately enclosed of heavily contaminated debris inside, together with contaminated soil. On 11 October 1986 the

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

Governmental Commission accepted a report entitled "Conclusion on Reliability and Durability of a Covering Constructions and Radiation Safety of Chernobyl NPP Unit 4 Reactor Compartment". The sarcophagus has over 60 bore holes to allow observation of the interior of the core. In many places the structure was designed to have ventilation shafts to allow some

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...

inside. Filtration systems have been put in place so that no radioactive material will escape through these holes.

Ongoing issues

4th block of the Chernobyl Nuclear Power Plant

The present shelter is constructed on top of the ruins of the reactor building. The "Mammoth Beam" that supports the roof of the shelter rests partly on the structurally unsound west wall of the reactor building that was damaged by the accident. The western end of the shelter roof is supported by a wall at a point designated axis 50. This wall is

and was cracked by the accident.

Designed Stabilisation Steel Structure

The DSSS is a yellow steel object that has been placed next to the wrecked reactor; it is 63 meters (207 ft) tall and has a series of

cantilever A cantilever is a rigid structural element that extends horizontally and is supported at only one end. Typically it extends from a flat vertical surface such as a wall, to which it must be firmly attached. Like other structural elements, a cant ...

s that extend through the western

wall, and is intended to stabilize the sarcophagus. This was done because if the wall of the reactor building or the roof of the shelter were to collapse, then large amounts of radioactive dust and particles would be released directly into the

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A ...

, resulting in a large new release of radioactivity into the environment. In December 2006 the "Designed Stabilisation Steel Structure" (DSSS) was extended until 50% of the roof load (about 400 tons) was transferred from the axis 50 wall to the DSSS.

Upper Biological Shield

A further threat to the shelter is the steel and concrete slab that formed the upper biological shield (UBS), situated above the reactor prior to the accident. This concrete slab was thrown upwards by the

explosion An explosion is a rapid expansion in volume associated with an extreme outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Supersonic explosions created by high explosives are known ...

in the reactor core and now rests at approximately 15° from vertical. The position of the upper bioshield is considered inherently unsafe, as only debris supports it in its nearly upright position. A collapse of the bioshield would further exacerbate the dust conditions in the shelter, possibly spreading some quantity of radioactive materials out of the shelter, and could damage the shelter itself. The UBS is a disk 17.7 meters in diameter, weighing 1000 tons. The shield is formally called ''Component E'' and nicknamed ''Elena''. The twisted fuel bundles still attached to it are called ''Elena's hair''.

Replacement

1121-Txernobylgo zentral nuklearrerako sarkofago berria-en

On 22 December 1988, Soviet scientists announced that the sarcophagus would only last 20–30 years before requiring restorative maintenance work. In 1998, with the help of the

European Bank for Reconstruction and Development The European Bank for Reconstruction and Development (EBRD) is an international financial institution founded in 1991. As a multilateral developmental investment bank, the EBRD uses investment as a tool to build market economies. Initially fo ...

, a conservation programme was completed that included securing the roof beams from collapsing. Nonetheless, the rain-induced

corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...

of supporting beams still threatens the sarcophagus' integrity. It was revealed that the water is leaking through the sarcophagus via holes in its roof, becoming radioactively contaminated, and then seeping through the reactor's floor into the soil. The

, rolled into place in November 2016, allows for the dismantling of the sarcophagus and for radioactive material to be removed. The containment was expected to replace the existing sarcophagus in 2015. However, delays and a €100 million funding gap caused a yearlong delay, before being moved into place in November 2016. , the building is undergoing testing of its installed systems.

References

Notes

External links

* {{Chernobyl disaster Chernobyl Nuclear Power Plant Sarcophagus Buildings and structures completed in 1986 Energy infrastructure completed in 1986 Buildings and structures in Pripyat Nuclear safety and security 1986 establishments in Ukraine