BUCHANAN — A nuclear reactor at Indian Point has been shut down to repair a pump.

Entergy Nuclear, the plant’s owner, says there was no release of radioactivity.

The pump is one of four that supply cooling water to the Indian Point 2 reactor. An Entergy spokesman says operators had noticed an increase of water flow through the pump’s mechanical seal over the past two weeks. He says that on Monday night, the extra flow reached a point at which operators decided to shut down for a repair.

He says it’s not yet known how long Indian Point 2 will be offline. It had been 230 days since its last shutdown.

The other reactor at the plant, Indian Point 3, continued operating at full power.