April 26 – Accident at the Unit 4. Governmental Commission for investigation of the accident causes and elimination of Chornobyl accident consequences had been created by the USSR Council of Ministers Order No 830. B.E.Shcherbina - Deputy Chairman of USSR Council of Ministers has been appointed as the commission head.
April 27 - Evacuation of the Pripyat and 10-km zone inhabitants.
April 27 - May 10 – Filling of a protective materials from helicopters in destroyed Unit 4.
May 2 – it has been accepted decision about evacuation of the population from ChNPP’s 30-km zone and from other communities fell under radioactive contamination. Power Units 1,2,3 transferred in temporary preservation mode.
May 6 – ChNPP’s personnel removed water from the ground floor of the Unit 4 suppression pool with the purpose to eliminate contact of the melted fuel with water. Sharp decreasing of releases. Beginning of ChNPP and Pripyat town territory, buildings and constructions decontamination.
May 9 - Decision of the CPSU Central Committee and USSR Council of Ministers "About decontamination works performance at the radioactively contaminated territories of Ukrainian SSR and Byelorussian SSR as a result of the accident at ChNPP".
May 16 - Governmental Commission has made the decision about long-term preservation of the destroyed power unit.
May 20 – Decree No 211 of the Ministries of the Middle mechanical engineering "About organization of construction management at Chornobyl NPP" (CM-605).
May 20 - July 15 - First stage of the "Shelter" construction. Preparation of area for civil work (retrieval of radiation sources, decontamination) deployment. Manufacturing of SO constructions and elements. Infrastructure creation (concrete factories, transport communications, social infrastructure, etc.).
June 3 - June 28 - Heat exchanger construction under a reactor foundation plate.
July 1 - According to the Decree No 394 of the USSR Energy Ministry ChNPP personnel ЧАЭС was transferred on shifts mode of work (15-15).
July 16 - September 15 - Second stage of SO construction. Performance of the major scope of civil work.
August 22 – it has been accepted the decision about additional evacuation of communities inhabitants in connection with the accident at ChNPP.
September 15 - November 30 - Third stage of SO construction. Completion of civil and erection works.
October 1 - Post accidental start-up of the Unit 1.
October 2 - Decision of the CPSU Central Committee and USSR Council of Ministers "About new town construction for Chornobyl NPP employees permanent residing".
November 5 - Post accidental start-up of the Unit 2.
November 30 - State Commission has accepted the preserved Unit 4 for maintenance.
December 3, 1987 – Post accidental start-up of the Unit 3.