Bulgaria is a signatory of the nuclear Non-Proliferation Treaty (NPT) and has signed and ratified the Comprehensive Test Ban Treaty (CTBT), being one of the 44 listed countries needed to sign and ratify for the CTBT to enter into force.
Bulgaria had six reactors operating at the Kozloduy nuclear power stations. All reactors are of the Soviet VVER design, the first four were the 440-230 model.
