Limerick Nuclear Generating Plant Had Inoperable Coolant System, Plant Reports To NRC

This story was updated Monday at 4:30 p.m. with information from Exelon.

LIMERICK TOWNSHIP, PA — The high-pressure coolant injection system at Exelon's Limerick Generating Plant was reported as inoperable to the Nuclear Regulatory Commission on Thursday, and by Monday afternoon Exelon reported the all related systems were again fully operational.

News of what the company called an "event" made its way to social media over the weekend, leaving residents near the Pottstown-area nuclear power plant wondering exactly what an inoperable high-pressure coolant injection system means, and how dangerous it might be.

Edwyn Lyman, Director of Nuclear Power Safety at the Union of Concerned Scientists tweeted on Sept. 24 "The Limerick-1 nuclear reactor in Pennsylvania is operating without a functioning high-pressure emergency core cooling system after it failed a surveillance test. @NRCgov will allow it to operate for up to 30 days in this condition — 16 days longer than the tech specs allow."

Asked when an update would come, Lyman replied, "Not likely to get an update until the system is repaired. You could try contacting @NRCgov but they will just tell you the increased risk is 'acceptable.'"

Dave Marcheskie, Regional Communications Manager, Exelon Generation, explained in a statement Monday afternoon what occurred in the reported event. "Limerick Generating Station is equipped with several redundant and diversified automated safety systems. During a scheduled test on Sept. 23, operators determined that one of the three automated systems that controls cooling water pressure was not operating automatically. The other two systems were operating automatically, and the third system was scheduled for repairs and could have been operated manually."

Marcheskie added, "The unit continued to generate electricity at full power, and repairs were successfully completed Sept. 26. All three automated systems are now fully operational."

Lyman's Tweet is confirmed in a Sept. 23 NRC report on the U.S. government website for the Nuclear Regulatory Commission.

The report made to the NRC says the "event" happened Sept. 23 at 2:43 p.m., that it was a non-emergency and that response to the event fell under "accident mitigation." The NRC was notified four hours after the event happened, at 6:46 p.m. on Thursday, according to the report.

The report from Limerick Generating Station stated, "During planned testing of the Unit 1 high-pressure coolant injection (HPCI) system, flow controller oscillations occurred which prevented successful completion of the surveillance test. Operators secured Unit 1 HPCI and declared the system inoperable."

The inoperable HPCI "placed the licensee (Limerick Generating Station) in a 14-day limiting condition for operation that was extended to 30 days after their risk-informed completion time evaluation was done. The licensee has notified the NRC Resident Inspector," the report said.

The event was reported by Kris Strausser. The HQ OPS Officer was Howie Crouch, according to the report. While this report represents the company reporting an incident to the NRC, the Nuclear Regulatory Commission does not yet show a record of its own inspection of the event. The most recent inspection report filed by the NRC was on Aug. 20.

A Safety Fact Sheet published by Exelon in 2011 explains the Limerick Generating Station is a dual unit General Electric Boiling Water Reactor with a concrete steel-lined containment structure; it is cooled by natural draft cooling towers. The main source of cooling water for Limerick is supplied by the Schuylkill River.

What Does It Even Mean?

So what's going on inside a boiling water nuclear reactor (BWR) that might explain what the reported inoperability of a high-pressure coolant injection system means?

A diagram is published by the Nuclear Regulatory Commission explains that inside the nuclear reactor system, water is converted to steam, and then recycled back into water by a part called the condenser, to be used again in the heat process.

"Since radioactive materials can be dangerous, nuclear power plants have many safety systems to protect workers, the public, and the environment," the NRC page said. "These safety systems include shutting the reactor down quickly and stopping the fission process, systems to cool the reactor down and carry heat away from it, and barriers to contain the radioactivity and prevent it from escaping into the environment. Radioactive materials, if not used properly, can damage human cells or even cause cancer over long periods of time."

With that useful information, a better explainer might be an animated diagram of the process that can be viewed here.

Limerick's Unit 1 reactor began producing power in 1986 and is licensed to operate through 2024. It provides 1,149 total net megawatts of electrical capacity at full power. The Unit 2 reactor began producing power in 1990 and is licensed to operate through 2029. It provides 1,146 total net megawatts of electrical capacity at full power, according to Exelon documents.

With license renewal, Limerick Generating Station Unit 1 and Unit 2 will be able to continue operating until 2044 and 2049.

Nuclear energy plants in the United States are licensed to operate for 40 years at a time, under the Atomic Energy Act of 1954.

The Limerick plant employs approximately 860 people. Exelon's website reminds the community, "We've been part of the Pottstown community for decades, providing hundreds of well-paying jobs and millions of dollars in economic support, including about $5.3 million in taxes annually for schools, roads, and other public services."

This Patch reporter formerly worked reading hundreds of NRC inspection reports as part of a month-long writing project related to the 30th anniversary of the March 1979 accident at Three Mile Island. She found the majority of the code violations identified by NRC inspectors at nuclear power plants were categorized as "of very low safety significance" as is likely the case in the Sept. 23 "event" that was reported as a "non-emergency."

With no disaster imminently related to an event, the findings get "Green" ratings, the lowest on a color scale. White is next on the scale of danger, representing "low to moderate risk." Yellow means the safety risk is "substantial" and Red, of course, means "high." Yellow or Red ratings rarely happen.

The Nuclear Regulatory Commission defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of, concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about, concerned primarily with ingestion of food and liquid contaminated by radioactivity.

A map and the Pennsylvania Emergency Management (PEMA) evacuation plan can be viewed here.

KI Tablets Are Out There

On Sept. 7, after the Schuylkill River and tributaries flooded in Hurricane Ida's fallout across eastern Pennsylvania, residents near four PA nuclear power plants were able to pick up potassium iodide tablets at public locations. Potassium iodide, or KI, helps protect the thyroid gland against harmful radioactive iodine and can be taken by anyone who is not allergic to it. In the interest of emergency preparedness, the Pennsylvania Department of Health the free distribution of KI tablets on Sept. 9 and 16.

Pennsylvania's four active nuclear facilities are: Limerick Generating Station; Peach Bottom Atomic Power Station on the Susquehanna River in Delta; Susquehanna Steam Electric Station in Luzerne County; Beaver Valley Power Station in Shipppingport; and recently closed is Three Mile Island Generating Station in Middletown.

The tablets are available to all Pennsylvanians who live or work within 10 miles of the four active nuclear power plants by visiting a distribution center listed below, calling the Department of Health at 1-877-PA-HEALTH, or visiting a county and municipal health department or state health center.

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