Waterford – Dominion is preparing to bring the Unit 3 reactor at Millstone Power Station back on line after a two-day voluntary shutdown to repair a small leak associated with the cooling system.

The leak was in a residual heat removal system linked to the reactor coolant system, according to an event report online. A shutdown was initiated around 8 p.m. Friday but the unit was brought off line gradually by Saturday morning, said Dominion Spokesman Ken Holt.

Dominion discovered the leak of about 80 drops a minute, which is equivalent to .084 gallons a minute, a month ago, but could not immediately repair it while the reactor was operating, and had scheduled a repair for September, Holt said. However, last week, the company also discovered seven hoses installed nearby in the mid-1990s that are not design compliant, he said.

The company then decided to voluntarily shut down the reactor, replace all seven hoses, which transport water used during shutdowns to cool the reactor, and fix the leak, he said.

The Nuclear Regulatory Commission’s inspectors monitored the work over the weekend, said NRC Spokeswoman Diane Screnci.