Chernobyl disaster monument. Monument dedicated to the fireman and 'liquidators' who participated in the containment work after the Chernobyl nuclear disaster, Ukraine. On the 26th April 1986 reactor number 4 of the Chernobyl nuclear power plant exploded causing huge amounts of radiation to enter the atmosphere. It is considered the worst nuclear power plant disaster in history. Thousands of workers were involved in the clean-up, many of whom suffered the effects from exposure to radiation. A sarcophagus surrounding the reactor was erected by December 1986.