Chernobyl disaster other undamaged reactors at the power station, with No. 3 continuing to produce electricity up into 2000. The accident motivated safety upgrades on all remaining Soviet-designed reactors in the RBMK (Chernobyl No. 4) family, of which eleven continued to power electric grids . The disaster began during a systems test on 26 April 1986 at reactor 4 of the Chernobyl plant near Pripyat and in proximity to the administrative border with Belarus and the Dnieper River. There was a sudden and unexpected power surge. When operators attempted an emergency shutdown, a much larger spike in power output occurred. This second
Effects of the Chernobyl disaster in 1988 to be "600,000 man Sv, equivalent on average to 21 additional days of world exposure to natural background radiation." The inhalation dose (internal dose) for the public during the time of the accident and their evacuation from the area in what is now the 30 km evacuation zone around the plant has been estimated (based on ground deposition of caesium-137) to be between 3 and 150 mSv. Thyroid doses for adults around the Chernobyl area were estimated to be between 20 and 1000 mSv, while for one-year-old infants, these estimates were higher, at 20 to 6000 mSv. For