Overview
- The disaster, which occurred April 26, 1986, followed a planned turbine test that disabled automatic safety systems on RBMK reactor 4 and pushed it into unstable low power.
- Pressing the AZ-5 emergency button drove in control rods with graphite tips that briefly increased reactivity, triggering a power surge, core melt, and two explosions that blew apart the unit.
- The IAEA attributes about 50 immediate deaths to the accident and estimates roughly 4,000 cancer cases, noting the release of more than 100 radionuclides including iodine‑131, cesium‑137, and strontium‑90.
- Authorities evacuated 162 settlements, including Pripyat, which once had over 45,000 residents who left homes, schools, and public buildings that still stand empty.
- Parts of the 30‑kilometer exclusion zone now host wildlife and limited tours that operators say deliver about 0.003–0.005 millisievert in a day, while containment built in 2016–2018 caps the site and final cleanup is projected for 2065.