page_title: Chernobyl disaster
section_title: No. 4 reactor confinement
hierarchical_section_title: Chernobyl disaster / Long term site remediation / No. 4 reactor confinement
caption_attribution_description: English: The New Safe Confinement in final position over reactor 4 at Chernobyl Nuclear Power Plant.
context_page_description: The Chernobyl disaster was caused by a nuclear accident that occurred on Saturday 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. It is considered the worst nuclear disaster in history and was caused by one of only two nuclear energy accidents rated at seven—the maximum severity—on the International Nuclear Event Scale, the other being the 2011 Fukushima Daiichi nuclear disaster in Japan.
  The accident started during a safety test on an RBMK-type nuclear reactor, which was commonly used throughout the Soviet Union. The test was a simulation of an electrical power outage to aid the development of a safety procedure for maintaining reactor cooling water circulation until the back-up electrical generators could provide power. This gap was about one minute and had been identified as a potential safety problem that could cause the nuclear reactor core to overheat. It was hoped to prove that the residual rotational energy in a turbine generator could provide enough power to cover the gap. Three such tests had been conducted since 1982, but they had failed to provide a solution.
context_section_description: Soon after the accident, the reactor building was quickly encased by a mammoth concrete sarcophagus in a notable feat of construction under severe conditions. Crane operators worked blindly from inside lead-lined cabins taking instructions from distant radio observers, while gargantuan-sized pieces of concrete were moved to the site on custom-made vehicles. The purpose of the sarcophagus was to stop any further release of radioactive particles into the atmosphere, mitigate damage should the core go critical and explode, and provide safety for the continued operations of adjacent reactors one through three.
  The concrete sarcophagus was never intended to last very long, with a lifespan of only 30 years. On 12 February 2013, a 600 m² (6,500 sq ft) section of the roof of the turbine-building collapsed, adjacent to the sarcophagus, causing a new release of radioactivity and temporary evacuation of the area. At first it was assumed that the roof collapsed because of the weight of snow, however the amount of snow was not exceptional, and the report of a Ukrainian fact-finding panel concluded that the collapse was the result of sloppy repair work and aging of the structure. Experts warned the sarcophagus itself was on the verge of collapse.
  In 1997, the international Chernobyl Shelter Fund was founded to design and build a more permanent cover for the unstable and short-lived sarcophagus. It received more than €810 million and was managed by the European Bank for Reconstruction and Development (EBRD). The new shelter was named the New Safe Confinement and construction began in 2010. It is a metal arch 105 metres (344 ft) high and spanning 257 metres (843 ft) built on rails adjacent to the reactor No. 4 building so that it could be slid over top the existing sarcophagus. The New Safe Confinement was completed in 2016 and slid into place over top the sarcophagus on 29 November. The huge steel arch was moved into place over several weeks. Unlike the original sarcophagus, the New Safe Confinement is designed to allow the reactor to be safely dismantled using remotely operated equipment.
caption: New Safe Confinement in 2017
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