Nuclear regulators probe two recent incidents at Peach Bottom plant

Nuclear regulators flagged two recent incidents at York County's Peach Bottom nuclear power plant that didn't pose an immediate danger to residents but nonetheless raised concerns from government regulators and a local watchdog group.

The U.S. Nuclear Regulatory Commission initially issued a white level issue — meaning an event of "moderate concern," according to NRC spokesperson Neil Sheehan — over a May power-loss incident that resulted in an emergency reactor shutdown at the plant located in Peach Bottom Township.

A less severe green issue was raised after inspectors found in August that a discharge valve connected to water pipes in Unit 2 was not automatically closing as it was designed to do.

Both issues are still going through the NRC's regulatory process, Sheehan said. They could result in increased scrutiny at the plant.

Sheehan said the May incident occurred during a construction project on an electrical grid the plant is connected to. Unexpected issues caused the breakers in the plant's switchyard to disconnect some of the power flowing to the reactor in Unit 2, he said.

When an electrical disruption is sensed, he said, the plant’s power system will respond with a partial reactor shut down and insert several control rods into the core to slow down nuclear fission. During the May incident, however, a plant operator caused a full shut down when they cut the remaining flow of power to the reactor. That halted all nuclear fission.

When a spokesperson for Constellation Energy, the company that owns and operates Peach Bottom, was asked about the power loss incident, they issued a statement saying they are reviewing the NRC's inspection report and that there was no risk to public safety during the incident.

Once Constellation responds to the report, Sheehan said the NRC will finalize its inquiry into the event.

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Eric Epstein, a longtime local nuclear energy watchdog, said his organization — Three Mile Island Alert — is satisfied with how the NRC is handling the rector shut down issue, they think there is inconsistency in how the NRC handles issues when it comes to the discharge valve problem.

Specifically, Epstein said a malfunctioning water valve should be more cause for concern than the current green-level issue advisory.

"Green is like getting a detention," he said. "White is pretty serious; that's like being called down to the principal's office."

Epstein, citing NRC reports, noted that the discharge valve issue was initially identified in 2016 but never addressed because testing protocols at the time didn't require the valve to shut on its own.

Peach Bottom uses a boiling water reactor in which water is heated by the nuclear core to produce steam. The steam then spins a turbine which powers a generator to produce electricity. Steam that is not used up in the turbine goes into a condenser to be cooled down.

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There are several pipes with water from the Susquehanna River being pumped through them in the condenser. This causes the steam to cool, recondense and run through the reactor again. Water in the condenser pipes comes in from the river through an intake valve and then is pumped back out through a discharge valve and does not come into contact with any radioactive substances.

Constellation found one of the discharge valves was stuck open instead of automatically closing while in use in 2016, according to NRC records. This lowered that pipe's water flow noticeably when compared to the other pipes in the system.

According to the NRC, the valve issue was identified again during an August inspection unrelated to the May emergency shutdown. NRC inspectors observed the lower water flow during their August inspection. No Constellation report about the valve issue had been made until the NRC requested it from Constellation, according to the NRC inspection report.

After an NRC follow up inspection in late September related to the emergency shutdown, the NRC published an inspection report. The report, which was sent to Constellation, reviewed the NRC’s findings for the two issues and shed light on why the water discharge valve had not been fixed.

NRC inspectors reviewed valve operating and shut down procedures, prior maintenance records and interviewed equipment operators. In the report, the inspectors found that Constellation's testing methods at the time did not require operators to check if valves could close properly — allowing the issue to go undetected for years.

With one of the condenser pipe valves left open, the flow of water in its pipe was measured at 3,300 gallons per minute, according to NRC documents. Pipes with a functioning discharge valve, had their flow of water measured at the normal 5,000 gallons per minute.

While that may not seem like a major difference, Epstein said it could be crucial in an emergency.

“In the event of an accident," he said, "half the flow that would go to the emergency pumps wouldn’t have been available.”

Sheehan, however, said the condenser has several pipes with cooling water. Even during an accident, he said the reduced water flow from one of the pipes would not be enough to cause an issue because there were still several other fully functioning water pipes in the condenser.

Since issuing the inspection report in late October, the NRC has not made its final decision on next steps. Even if the NRC finalizes the white label for the power loss issue, Sheehan said white issues typically do not rise to the level of monetary fines. The NRC may, however, increase oversight of operations at Peach Bottom.

— Reach Noel Miller at [email protected] or via Twitter at @TheNoelM.