Chernobyl

The Chernobyl disaster (also known as the Chornobyl disaster) was a nuclear accident that occurred on April 26, 1986, at the No. 4 reactor in the Chernobyl Nuclear Power Plant near the city of Pripyat in the Soviet Union's Ukrainian SSR. It is one of only two nuclear energy accidents rated seven on the International Nuclear Event Scale, the other being Japan's 2011 Fukushima nuclear disaster. The initial emergency response, as well as subsequent environmental decontamination, involved over 500,000 personnel and cost an estimated 18 billion roubles—roughly US$68 billion in 2019, adjusted for inflation.

Following the reactor explosion, which killed two engineers and severely burned two more, a massive emergency operation was launched to extinguish the fire, stabilize the reactor, and clean up the ejected radioactive material. During the immediate response, 237 workers were hospitalized, with 134 showing signs of acute radiation syndrome. Among those hospitalized, 28 died within three months, all of whom were being treated for ARS. In the ten years that followed, 14 more workers (nine of whom had been hospitalized with ARS) died of causes that were mostly unrelated to radiation exposure.

The health effects of Chernobyl on the general population are unknown. As of 2011, there had been an excess of 15 childhood thyroid cancer deaths. A United Nations committee determined that the fallout has resulted in fewer than 100 deaths to date. The linear no-threshold model, a contested statistical model, makes determining the total eventual number of exposure-related deaths uncertain. The final total death toll predicted by models varies over the next few decades. The World Health Organization's most widely cited studies predict 4,000 deaths in Ukraine, Belarus, and Russia.

Following the disaster, Pripyat was replaced by the new purpose-built city of Slavutych. The USSR built the protective Chernobyl Nuclear Power Plant sarcophagus by December 1986. It reduced the spread of radioactive contamination from the wreckage and protected it from weathering. The confinement shelter also provided radiological protection for the crews of the undamaged reactors at the site, which were restarted in late 1986 and 1987. However, this containment structure was only intended to last for 30 years, and required considerable reinforcement in the early 2000s. The Shelter was supplemented in 2017 by the Chernobyl New Safe Confinement which was constructed around the old structure. This larger enclosure aims to enable the removal of both the sarcophagus and the reactor debris while containing the radioactive materials inside. Clean-up is scheduled for completion by 2065.

Date: 26 April 1986; 36 years ago
Time: 01:23 MSD (UTC+04:00)
Location: Chernobyl nuclear power plant, Pripyat, Chernobyl Raion, Kyiv Oblast, Ukrainian SSR, Soviet Union(now Ukraine)
Type: Nuclear and radiation accident
Cause: Reactor design flaws and human error
Outcome: INES Level 7 (major accident) see Chernobyl disaster effects
Deaths: Fewer than 100 deaths directly attributed to the accident. Varying estimates of increased mortality over subsequent decades (see Deaths due to the disaster)