A 1,000-megawatt reactor at Bulgaria\'s Kozloduy nuclear plant was temporarily shut down early Saturday due to a turbogenerator problem, but no rise in radioactivity was recorded, a statement said. \"Unit 6 of the Kozloduy plant was shut down by the turbogenerator\'s protection system,\" the plant said, adding: \"No change in the level of radioactivity has been registered.\" The unit was to be restarted by the end of the day. Kozloduy, Bulgaria\'s sole nuclear power plant, has two 1,000-megawatt reactors supplying about 30 percent of the country\'s power. Four older 440-megawatt reactors at the plant were shut down in 2002 and 2006 as conditions for Bulgaria\'s entry into the European Union.