Following a signed agreement between the European Commission and the government of Bulgaria, Unit 1 of Kozloduy Nuclear Power Plant was shut down for safety tests on 15 May 1996. Last winter, concern was expressed when Unit 1 was restarted by the Bulgarian government despite advice from EU experts that tests were needed to ensure that the reactor was safe. If the present tests show that the safety of Unit 1 needs to be improved, the necessary work will be carried out. The decision on whether to restart Unit 1 will be taken on the basis of common agreement between the main designer and Bulgarian and EU experts. The Commission will provide assistance from the PHARE technical assistance programme for the Central and East European countries for the tests and for helping with alternative energy supplies for winter 1996/1997. The Kozloduy Nuclear Power Plant generates around 40% of Bulgaria's electricity. The power plant has six nuclear reactors, of which Units 1 to 4 are of the oldest type of Soviet-designed pressurized water reactors. Units 5 and 6 on the other hand are the most modern type of Soviet nuclear reactors. In 1994 European experts expressed the opinion that the reactor pressure vessel (the reinforced container within which the nuclear reactions take place) of Kozloduy Unit 1 had to be tested to assess its safety. The Commission has been working closely with the Bulgarian government to ensure that until these reactors are permanently closed they are operated in the safest possible conditions.