Six workers were sprayed with the contaminated water and were being checked for radiation exposure, the Japan Broadcasting Corp. reported.
The plant's operator, the Tokyo Electric Power Co., said the workers detached the pipe from a joint near a desalination device.
About 7 tons (about 17,000 gallons) of highly radioactive contaminated water leaked during a period of about 50 minutes.
The water is now contained inside a barrier that surrounds the device, Tepco said.
Notable deaths of 2014 [PHOTOS]
Abducted Libyan can sue, British court rules