Problem Shuts Down Chernobyl Reactor

A faulty cooling system pump has forced shutdown of the No. 3 reactor at Ukraine’s Chernobyl nuclear plant, nuclear safety officials said Monday.

No increase in radiation was recorded.

Operators detected the defect Sunday and ordered the reactor switched off, said Mykola Oberkovich, spokesman for Ukraine’s nuclear regulatory agency. It is unclear how long the pump has been broken.

Plant engineers are repairing the device and expect to restart the reactor Saturday, he said.

The Chernobyl plant was the site of the world’s worst nuclear accident, a disastrous explosion at reactor No. 4 in 1986. Reactor No. 2 has been idle since a huge fire in 1992.