COVERT TOWNSHIP, MI -- The leak that shut down Palisades Nuclear Power Plant May 5 is one of a series of incidents that have bedeviled the nuclear reactor in recent years.

Nuclear Regulatory Commissioner Kristine Svinicki will tour Palisades Nuclear Power Plant on Monday, May 13, at the invitation of U.S. Rep. Fred Upton, who will accompany her.

Palisades officials will host an open house to answer questions from the public about the plant Tuesday, May 14, from 5 to 7 p.m. at the Beach Haven Event Center in South Haven.

Entergy Corp. bought Palisades from Consumers Energy in 2007 for $380 million. The one-reactor plant, which is located along Lake Michigan in Covert Township, supplies about 20 percent of the utility's power. The facility came online in 1971 and its license runs until 2031.

Below is a timeline of incidents at Palisades since 2007, based on NRC reports and previous MLive/Kalamazoo Gazette articles.

2007 -- Palisades' head of security resigned amid revelations he had fabricated some of his credentials.

2008 -- An NRC safety assessment found Palisades failed "to recognize and assess the impact of radiological hazards in the workplace." The NRC found that Palisades failed to determine how much radiation employees were exposed to after radiation monitors worn by the workers warned of an exposure.

August 2008 -- Five workers were trapped for 90 minutes inside a high-temperature area when a hatch malfunctioned. The NRC launched a probe and found the plant did not take proper precautions to prevent such occurrences.

2009 -- During an inspection, the NRC found that workers failed to notice a problem in the pool where spent fuel rods are kept. The finding, labeled a "low to moderate safety" risk that did not endanger the public, kept Palisades on the NRC's list of plants that required additional regulatory oversight for a second year. The plant's 2009 safety assessment also found problems with human performance regarding "error-prevention techniques."

May 2010

-- A Palisades manager left the control room without following protocol and the event was not reported within 24 hours, the NRC found.

January 2011

-- Palisades operated at 55 percent power for eight days after a cooling-water pump lost power when an electrical bus failed. The event did not represent a threat to health and safety, the NRC said.

May 2011

--

While NRC inspectors were conducting a routine test of the plant’s auxiliary feed water system, a turbine-driven pump was tripped. Investigators found a component of the pump that was greased and should not have been. The NRC classified the event as a "low to moderate" safety significance.

August 2011

-- The NRC launched a special inspection after the failure of a coupling that holds pipes together.

. Palisades replaced all couplings.

September 2011

-- Palisades shut down between Sept. 16 and Sept. 20 for repairs,

September 2011

Palisades shut down for a week after

Sept. 25, when a worker performing maintenance on an electrical panel when a piece of metal came into contact with another metal piece and caused an arc. There were no injuries reported. The NRC launched a special investigation,

the second in two months.

The investigation found that during the incident, which it named of "substantial significance to safety," Palisades did not follow proper safety protocols before the shutdown.

November 2011

-- The NRC bumped Palisades

of the May 2011 incident.

January 2012

-- Palisades shut down for 3-1/2 days

February 2012

-- The NRC

, making it among the four-worst performing reactors in the U.S. The downgrade came as a result of the two special investigations launched in 2011.

June 2012

-- Palisades shut down for a month

. Numerous cracks were found within the 300,000-gallon storage tank, according to reports. When the plant returned to service, the tank was still leaking, but due to its size, it did not pose a safety risk, the NRC found.

July 2012

-- An independent review of Palisades

The study, conducted by Conger & Elsea Inc. in January and February 2012, looked at plant operations related to human performance, safety-conscious work environment, problem identification and resolution.

August 2012

-- Palisades shut down

. The NRC sent a three-inspector team and launched a special inspection of the pressure-boundary leak. During the 30 days before the location of the leak was discovered, up to 10,000 gallons of radioactive water leaked from the containment vessel. The water was contained and did not pose a safety risk to the public, the NRC found.

September 2012

-- An NRC inspector found what it characterized as

. The water was not radioactive and did not represent a health or safety risk, the NRC said.

September 2012

-- Entergy

The New Orleans-based company said it paid the government $6 million in fees a year to take its waste. Since the Department of Energy has not done so, Entergy said it has spent an estimated $100 million storing the waste.

November 2012

-- Palisades shuts down for three days

.

November 2012

-- The NRC upgraded Palisades after an 11-day inspection in September found that Entergy

. The NRC ordered an additional 1,000 hours of inspections in 2013, on top of the standard 2,000 hours.

February 2013

-- Palisades shut down for six days to

. It was leaking 35 gallons of non-radioactive water an hour before the shutdown, the NRC said. The leak did not represent a threat to the public or the plant, the NRC said.

March 2013

-- Palisades was

according to a report by the independent Union of Concerned Scientists. The near-misses at Palisades resulted from long-standing problems, the UCS said, and it charged the NRC with failing to enforce violations.

May 2013

-- On May 5, Palisades shut down after the leak in the safety injection refueling water tank accelerated from one a day to 90 gallons within a 24-hour period, the NRC said. On May 4, before the shutdown,

, where it was extremely diluted, according to the NRC, and ended up in Lake Michigan. The NRC has sent an additional inspector to Palisades, and one of its health physicists is also investigating the incident. As of May 10, Palisades was still offline while workers and inspectors search for the source of the leak and make repairs.