Update 4:14 p.m.

“The most important thing to understand regarding this shutdown is the health and safety of our employees and the public has never been impacted by this issue,” said Terry Young, Vice President of Nuclear Communications for Entergy.

He confirms the unplanned release of slightly radioactive water into Lake Michigan, but couldn’t say exactly how much.

“It’s really impossible to tell at this juncture what the length of this shutdown will be because we haven’t yet had a chance to identify what the issue is that we’re going to need to fix,” Young said.

This will be the third attempt to fix the leaky tank within the last year and a half.

“We have gone through pretty exhaustive measures on a couple of occasions to bring the plant offline and do just extensive testing and repairs and we’ll take a look at what’s causing the leak this time,” Young said.

I asked if it would make more sense to replace the tank instead.

“I really don’t know any background information on that in terms of what that would cost, I honestly couldn’t comment on that,” Young said.

Young notes the plant has had “a lot of success” at Palisades in the year and a half in “significantly improving performance.” The NRC recently upgraded the plant's safety rating after a series of problems in 2011 left it with one of the worst safety performance ratings in the country.

Last month Site Vice President Tony Vitale noted that a number of issues “have required repairs to be done with the plant offline and that’s unacceptable.” He says they’re reviewing their procedures to see if there’s something they should change.

“We’re diving into our programs and finding out why these issues are finding us instead of us finding them,” Vitale said in April.

“It is unfortunate that this is a recurrent issue that we are dealing with here,” Young said, “but our resolve is strong to fix this issue once and for all.”

Updated 1:11 p.m.

Officials from the Nuclear Regulatory Commission estimate 79 gallons of "slightly" radioactive water drained into Lake Michigan on Saturday.

NRC Spokeswoman Viktoria Mitlyng says the agency doesn’t know exactly how radioactive the water was, but based on general knowledge of where the water came from, there is no risk to public safety.

“The unplanned release of this radioactive water is not something you want to have happen,” Mitlyng added.

The water came from a large water tank on the roof of the Palisades plant’s control room. It holds 300,000 gallons of water in case of emergencies or a planned refueling outage.

The plant is located in Covert Township, about 70 miles southwest of Grand Rapids.

The plant shut down in June 2012 to repair the same tank. There was still a leak afterward, but it was a small leak.

Mitlyng says the leak rate jumped from about one gallon per day on Friday to about 90 gallons on Saturday. That crossed a 32-gallon-per-day threshold agreed to between the NRC and the plant.

Mitlyng says the radioactive water went down a drain on the roof, and that drain goes into a basin that feeds into a cooling system that uses water from Lake Michigan. So it’s assumed the water went out into the lake as well, Mitlyng said.

There have been times where water from the tank leaked into the control room below it, but Mitlyng says that did not happen over the weekend. An internal investigation of the NRC’s “historical handling” of the water tank leaks was launched in June 2012 and is still ongoing, Mitlyng said.

She says the NRC is sending another inspector to the site with expertise in this kind of tank.

The rest of the water in the tank will have to be drained into special containers before the tank can be inspected. It’s unclear how long that will take.

Mitlyng says the NRC will host a webinar to inform the public about the leak and give people a chance to ask questions. It has not been scheduled yet.