Cracks were detected in the protective casings of a number of control rods at Bulgaria's sole nuclear plant, but there has been no release of radioactivity, the plant's operator said Thursday.
The cracks were detected during regular maintenance checks and refuelling of one of two reactors in operation at the Kozloduy nuclear plant, it added in a statement.
"Mechanical defects" or cracks were found in the protective casings of 37 control rods. As a result, the operator ordered the replacement of all 61 control rods and their casings at the 1,000-megawatt reactor number 5, the statement said.
The operation would not, however, affect initial plans to switch the reactor back into the national power grid early next month, the operator insisted.
This is the second such incident at Kozloduy within the past year, after similar cracks were found in 31 control rods of the number 6 reactor.
At that time, all of the control rods and casings were similarly replaced and the plant's chief executive was sacked.
Last week, maintenance engineers at Kozloduy detected increased levels of radioactivity in the containment of reactor 5, but reported no leakage outside the block.
Only two of Kozloduy's six reactors are actually operational, after the other four were shut down as one of the conditions for Bulgaria's accession to the European Union in 2007.
Explore further: Self-cooling solar cells boost power, last longer