Can a mothballed nuke plant be restarted? They’re trying in Michigan

Industry Discussions Nuclear Power
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According to information from Entergy, the Palisades Power Plant steam generators have a design with 8,519 tubes per unit, each with a diameter of ¾ inch.

NRC report claims 1400 tubes have stress corrosion cracking. Once these old steam generators are put under pressure and temperature there will be many more tube problems/failures. I think that these old steam generators should be replaced. This will cost several billion dollars and many years to complete which is more than the money they have gotten and operation in 2025 is a pipe dream. I think Holtec is just is taking all the money they can get on this pony and ride it until it is all gone with no power generation.

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Is Three Mile Island restart in better shape?

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Is Three Mile Island restart in better shape?

It is probably too early to tell, at least from the publicly available information. Holtec has been working on the Palisades restart for at least two years. Here is an article from September 2022.

Constellation only announced the restart plan for Three Mile Island (TMI) last month. So they are just beginning to establish the scope of everything that needs to be evaluated and repaired/replaced before getting approval from the NRC. It is not just the physical equipment that needs evaluation, but they also need to have enough reactor operators qualified at TMI in order to restart.

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One difference that might be important is that TMI is a Babcock & Wilcox design. The B&W plants use once-through steam generators, instead of the recirculating steam generators used at Palisades (and most other PWRs). B&W plants have generally had fewer steam generator corrosion problems, but they are not completely immune either. It is just a different design.

_ Pete

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There are only 5 operating Babcock & Wilcox reactors in the United States: Arkansas 1, Davis Besse, and Oconee 1, 2, and 3,

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As I cautioned above, the conditions of the Palisades’ steam generators are going to be critical for the viability of returning the plant to service. Rather than replacing the steam generators completely, it appears Holtec managers have decided to sleeve the SG heat exchanger tubes, to keep them in service.

Sleeving involves inserting a slightly smaller tube inside an existing tube, thereby strengthening it and reducing the chance for a leak. One problem, however, is these sleeves are only a few feet long, so only a portion of the steam generators will be protected, but those areas are likely where the corrosion problems are occurring. Specifically, the corrosion is usually at the Tube Support Plate (TSP) regions.

From the link:
Holtec’s inspections found more than 1,400 indications of corrosion cracking across more than 1,000 steam generator tubes at Palisades, according to a company filing with the NRC in October 2024. The tubes have not failed, Holtec CEO Krishna Singh told CNBC in February. Several had corrosion cracking with more than 70% penetration, according to the filing.

And:
“The techniques of repair which we’re using, which is called sleeving, has been done in about 10 plants across the world and in some plants is done every outage, so this is not new, exotic technology,” Trice said. “It is a common repair technique, and we expect it to be done on time and on schedule.”

Holtec’s repair plan is scheduled to start this summer following inspection and testing, spokesperson Nick Culp told CNBC. Holtec can go ahead with the tube repairs on its schedule, but the company does so at its own risk as the NRC will decide whether the repairs meet requirements in the end, Burnell said.

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If you are interested, a more detailed description of the sleeving method proposed for Palisades can be found here:
https://www.nrc.gov/docs/ML2504/ML25043A348.pdf

From the pdf:
A lattice tube support plate (TSP) sleeve is designed to repair tube degradation occurring at TSP intersections of SG tubes. A mechanical sleeve is a tube segment that is inserted into an existing SG tube and expanded to create an interference fit between the sleeve and the tube. The proposed sleeve uses hydraulic expansion to create the interference fit.

The tubing material for the sleeve is thermally treated Alloy 690. Section 3.4.3 discusses the basis for selecting Alloy 690 as the sleeve material. The sleeve is fabricated with sealing ribs on the outside diameter (OD) of eight expansion areas. The profile of these ribs, when combined with the sleeve expansions, gives the sleeve improved leak limiting characteristics compared to the expansion of a smooth sleeve. The free span sleeve/tube joints are produced by a controlled hydraulic expansion process. A total of eight joints are produced simultaneously, with four above and four below the TSP.

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Alloy 690 is a type of Inconel steel with high chromium and nickel components, making it highly resistant to the type of corrosion that occurs in nuclear steam generators. Alloy 690 replaces the earlier Alloy 600 material used in older steam generators.

Another issue is the existing steam generators are going to be rather radioactive after years of service. This makes work inside them more difficult, and much of the sleeving work will have to be done remotely.

Bottom line: Sleeving is a cheaper and faster alternative than replacing the entire steam generators, but it is only a partial solution. The Holtec managers evidently think it is a good enough solution.

_ Pete

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One more step toward restart of Palisades…

The NRC has approved the restart environmental assessment.

https://www.reuters.com/sustainability/us-approves-environmental-review-michigan-nuclear-plant-restart-2025-05-30/

WASHINGTON, May 30 (Reuters) - The U.S. on Friday said Holtec’s planned restart of the Palisades nuclear power plant in Michigan would not harm the environment, a needed step in its plan to become the first such plant to return from permanent shutdown.

The Nuclear Regulatory Commission conducted the environmental review of the Palisades reactor restart with the Department of Energy’s Loan Programs Office.

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However, the steam generator issues remain.
Also from the Reuters link:
Alan Blind, engineering director at the plant from 2006 to 2013, said in an editorial this month that if steam generator problems lead to a shutdown, it would “erode public confidence, damage investor trust, and raise serious safety concerns.”

The NRC is reviewing Holtec’s proposed repairs, said Scott Burnell, an agency spokesperson. “Holtec must demonstrate the Palisades steam generators will fulfill their safety functions before the plant restarts,” Burnell said.

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A short statement from the NRC on the environmental assessment:

_ Pete

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Here is a progress report on the Palisades restart. They appear to be on track.

New fuel has arrived at the plant…

From the link:

“Following the completion of technical reviews, the US Nuclear Regulatory Commission (NRC) on 24 July this year approved the transfer of operating authority for the plant and its independent used fuel storage facility from Holtec Decommissioning International LLC to Palisades Energy LLC. It also approved the reinstatement of various documents and programmes that were in place prior to the shutdown, including the technical specifications, emergency plan, emergency action levels, and physical security plan, as well as programmes for quality assurance, maintenance, and in-service inspections. In late August, Holtec announced that Palisades had resumed operational status.”

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Also:

“The plant also recently received and installed the second of two fully refurbished primary coolant pump motors, which is essential to recirculate the reactor coolant. The chemical cleaning of the secondary side of the steam generators is also under way. This work follows successful completion of refurbishing of the steam generators’ tubes earlier this summer and is intended to ensure long-term reliability and efficiency of the plant.”

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The “refurbishing of the steam generators’ tubes” is probably the tube sleeving procedures discussed earlier in this thread. That sleeving appears to be complete, and they are performing a chemical cleaning of the secondary side of the steam generators. I was deeply involved in such a chemical cleaning at one of the plants I worked at. The cleaning is supposed to dissolve and wash away the sludge that tends to build up on the bottom tubesheet and tube supports. If they can do it right, the cleaning and sleeving should extend the life of the steam generators at least several years.

_ Pete

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Fourth quarter this year restart planned per the article. Seems to be on schedule.

Please keep us advised.

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Now it looks more like the first part of 2026. It is not unusual for the restart schedule to slip a bit. Nuclear plants are complicated pieces of machinery. The following article mentions the steam generator tube sleeving, which is a big operation to get those heat exchangers back to a suitable condition.

_ Pete

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A significant setback happened last year, when an inspection found that thousands of tubes from the plant’s steam generator were cracked and needed repair.

Opponents of the restart blamed Holtec for not properly protecting the steam generator system when it went offline. They’ve also argued the steam generator itself needs to be replaced.

But Holtec has moved forward with a plan to insert sleeves into the tubes to fortify them.

Federal regulators have given initial approval for the plant to return to operating status, but other hurdles remain before power generation can resume.

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I remember well when San Onofre Nuclear Generating Station (SONGS) was shutdown by NRC order because of leaking steam generator tubes. Steam generators are Achilles Heel of pressurized nuclear power plants in the USA.

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They just started loading fuel into the Palisades reactor. Sure, the schedule has slipped from their initial optimistic target. Palisades is an old plant, and nobody expected the new owner to attempt a restart when the plant was originally permanently shut down.

But now that they are loading fuel, that means most of their repair and refurbishment items are compete. Actual restart could be a few weeks or a few months away, if all goes well.

After they get the reactor critical and generating nuclear heat, the next milestone, and perhaps a subject of concern, will be monitoring the main turbine for vibration when it is at speed and loaded. Its been a long time since that turbine and generator were actually producing power.

_ Pete

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