Kozloduy nuclear power plant is the first nuclear power plant in Bulgaria and south-eastern Europe.
The beginning of the nuclear power engineering was laid on 15 July 1966 by signing the agreement for cooperation between Bulgaria and former Soviet Union for the construction of a nuclear power plant. Following a detailed feasibility study the site on the Danube river was selected in the proximity of the town of Kozloduy.
The designs for the plant were developed by Toploelektroproekt – Moscow and Energoproekt – Sofia. The main equipment was delivered by the Soviet Union, and some separate pieces of equipment from the former German Democratic Republic , Czechoslovakia and Hungary. The ground breaking ceremony for Kozloduy NPP was held on 14 October 1969. In April 1970 the large scale construction activities for the facility, still unique for the country in the present days, started. More than one hundred thousand construction and installation workers took part in the construction.
Some completely Bulgarian projects have been implemented for the first time in the world practice in the construction of nuclear power plants. Some of these technical solutions are significant engineering achievements foreign specialists have been interested in.
The construction of the main building of Kozloduy NPP started on 6 April 1970 -240 m long, 105 m wide and 40 m high. The reactor hall, turbine hall, ventilation center and the electrical devices of the 440 MW units are inside this building. In June 1972 the first reactor arrives from the Soviet Union, and on 20 November same year it was installed into the reactor cavity.

The construction and commissioning of the Bulgarian nuclear power plant was implemented in three stages:

• І stage: 1970 – 1975 Construction and commissioning of unit 1 and 2 with WWER-440 , model В-230, with two independent trains of the safety systems.
  Start-up of Unit 1: 1974
  Start-up of Unit 2:1975
  The official opening of Kozloduy NPP was on 4 September 1974.
  
• ІІ stage: 1973 – 1982 Construction and commissioning of Units 3 and 4 with WWER-440, upgraded model В-230 with three-fold redundancy of the safety systems .
  Start-up of Unit 3: 1980
  Start-up of Unit 4: 1982
  
• ІІІ stage: 1980 – 1991 Construction and commissioning of Units 5 and 6 with WWER-1000, model В-320 with containment and three-fold redundancy of the safety systems.
  Start-up of Unit 5: 1987
  Start-up of Unit 6: 1991
  

Following the commitments made by Bulgaria with regard to the accession to the EU, Kozloduy NPP stopped the operation of the first four units before the expiry of their design lifetime that is 30 fuel campaigns.

Since the beginning of 2007 Units 5 and 6 have remained in operation.

Following Decision of the Council of Ministers’ as of 20th December 2008, Units 1 and 2 were announced as radioactive waste (RAW) management facilities and along with the personal property have been transferred to State Enterprise Radioactive Waste (SE RAW). Pursuant to the decision Kozloduy NPP shall continue operating these units in compliance with the licences obtained for E mode of operation (without electricity and/or heat generation and storage of spent nuclear fuel at the reactor spent fuel pool) up to the moment of obtaining the relevant licences by SE RAW.
On 18th October 2010 the Bulgarian Nuclear Regulatory Agency issued licences to SE RAW for the operation of Units 1 and 2 as radioactive waste management facilities which shall be decommissioned and revoked Kozloduy NPP licences for operation of the first two units in E mode of operation.

Under a Council of Ministers’ Decree as of 19th December 2012, Units 3 and 4 have been announced as radioactive waste management facilities which are subject to decommissioning. In accordance with the Decree, the necessary real and personal properties shall be transferred to the State Enterprise Radioactive Waste. Until SE RAW obtains the required licences, Kozloduy NPP shall continue operating Units 3 and 4 in compliance with the existing licences for E mode of operation.

On 25th February 2013 the Bulgarian Nuclear Regulatory Agency issued licences to SE RAW for the operation of Units 3 and 4 as radioactive waste management facilities which shall be decommissioned. In connection with the issuance of the new licences to SE RAW, the licences of Kozloduy NPP for operation of Units 3 and 4 in E mode of operation were revoked.