Palisades Tank Leak Repaired — Safe to Restart

Prema Chandrathil
Region III Public Affairs Officer
 

palisades_smallAfter intense NRC scrutiny that confirmed the plant is safe to operate, the Palisades nuclear power plant in Michigan restarted Monday after more than a month shutdown.

In total 10 NRC inspectors performed a wide range of inspections to ensure the leak in a refueling water tank, the reason for the shutdown, was fixed.

Entergy employees identified a leak from the tank on May 5.The leak exceeded the level Entergy had committed to the NRC, which required the plant to shut down to ensure structural integrity of the tank.

The tank is used during refueling outages and to supply water to the reactor during emergencies. It has leaked before. That’s one reason why, in a July 2012 letter, the plant made a commitment to measure and trend daily leakage from the tank, and shut down the plant if the leak exceeded certain limits.

The NRC responded quickly once the leak was reported. The resident inspectors headed into the plant that Sunday, May 5, to closely follow Entergy’s actions to shut down the plant and inspect their efforts to identify the leak. We also sent a specialist with a background in materials engineering to further inspect the plant’s detailed actions to identify and repair the leak.

And we had additional inspectors review and assess the plant’s test and repair plan, look into the area beneath the tank, understand and analyze the stresses on the tank, review the root cause of the leak, and observe the actual welding and testing of the tank components.

NRC’s Region III also continued our commitment to openness and transparency by publicly documenting phone call discussions between Entergy and NRC management on this issue. Additionally, the region held a webinar on radioactive releases during which Region III staff addressed the public’s questions and concerns about the tank leak. More than 70 people participated in the webinar.

Going forward, the NRC will continue to make sure the tank remains safe. We will independently inspect the areas around the tank where leaks can be identified and will follow Entergy’s actions to monitor the tank. If small leaks are discovered we expect Entergy to evaluate them according to the NRC’s rules, and take appropriate action.

We have received dozens of calls and inquiries about this issue. We want to assure you that the public and plant workers continue to be safe. We remain committed to being open and transparent about issues of concern to the local public. To that end, we will hold an internet event to discuss NRC regulations regarding this tank and why Palisades was safe to restart. Once a date has been determined details will be posted on the NRC website.

How the NRC is Responding to the Cooling Water Leak At the Palisades Nuclear Plant

Prema Chandrathil
Region III Public Affairs Officer
 

On Friday, the Palisades plant in Covert, Mich., shut down so plant personnel could find and repair a leak somewhere in the reactor’s cooling water system. Soon after, the NRC dispatched an additional inspector from the Regional III office, located in Lisle, Ill., with a background in mechanical testing and repairs. He supplements the two NRC resident inspectors as they evaluate the plant’s repair activities.

palisades_smallFor more than a week now, the NRC resident inspectors on site have been following the actions taken by workers at Palisades to find the leak. The resident inspectors reviewed the data. They also watched plant workers as they isolated different parts of the system to conduct tests to try and identify exactly where the leak was coming from.

Plant workers caught the problem because the water level in the component cooling water system was going down slowly. This system uses non-reactor water to cool certain safety equipment. Per NRC regulations the system is required to be monitored. When the plant shut down the system was leaking about 35 gallons per hour. This water was captured and released to Lake Michigan through an established monitored release path. The leak did not place the plant or the public in danger.

It’s now believed a heat exchanger in the system is the source of the leak. A heat exchanger is basically a box that contains around 2,000 tubes. The tubes have water running through them to remove heat from equipment, such as seals or pumps. This heat exchanger plays an important role to cool necessary equipment during normal operation, but also during potential accident scenarios.

Palisades has two safety-related heat exchangers in this particular system; both are required by NRC regulations to be in working condition and ready to respond at a moment’s notice. With one of the two exchangers potentially not working right the plant decided to shut down before the regulations required it. NRC regulations state if there is a problem with the heat exchanger it would need to be fixed within 72 hours. If that’s not possible the regulations require the plant to shut down to find the leak and make the appropriate repairs. The plant will only be able to restart when the heat exchanger is working correctly.

Over the weekend all three NRC inspectors continued to monitor and assess the repair work to find and fix the leak. The NRC will continue to closely follow this event and observe how the plant goes about these activities with safety in mind from start to finish. We know the community is interested and concerned about these types of issues and continue to work to keep our commitment to ensure they are informed.

One of our initiatives is to provide summaries of conversations between the NRC and plant staff to the public. A summary of such a conversation about this leak, which took place on Thursday, Feb.14, will be available to the public in the near future. Our assessment of this issue will also be documented in a publically available inspection report.