2 Pilgrim shortcomings ongoing since plant opened
Posted Sep 29, 2017
Recent ‘more than minor’ infractions had been undetected since early 1970s.
PLYMOUTH — When federal regulators recently conducted an inspection at Pilgrim Nuclear Power Station that is done every three years to ensure certain systems can perform as designed, components in two of the six systems chosen for testing fell short.
Both shortcomings had been ongoing and undetected since the reactor opened in the early 1970s. And both had the potential to affect systems needed in an emergency.
Nuclear Regulatory Commission inspectors classified the shortcomings as “of very low safety significance,” although they said both could lead to more significant safety concerns. One plant critic said the results from the small sampling were troubling.
“They chose six systems, and they found problems in two out of six,” said Mary Lampert, president of Pilgrim Watch. “That gives the plant a 67 percent. If they had chosen another six systems, would the results have been the same?”
One violation was found in the low-temperature limit setting being used for two massive condensate storage tanks and their pipe networks.
The system supplies water to cool the reactor in an emergency.
Maintaining the correct water temperature, by seeing that it does not fall too low, prevents brittleness from developing and breaking from occurring. The inspectors found that the low temperature limits used by Pilgrim operators fell short of design standards. Operators focused their attention on the low temperature limits in the metal tanks “rather than the more limiting material service temperature of the downstream safety-related piping,” they wrote.
In their report, inspectors call the finding “more than minor because, if left uncorrected, the performance deficiency would have the potential to lead to a more significant safety concern.”
David Lochbaum, director of the Nuclear Safety Program for the Union of Concerned Scientists, put the possible outcome in simple terms: “If the piping broke, it matters little if the condensate storage tank water remains unfrozen — the water would not reach the reactor vessel where it would be needed for cooling.”
The federal team noted, in its analysis, that since the plant opened 45 years ago, “the minimum temperature limits to preclude brittle fracture behavior in the associated piping system were not correctly translated into station procedures.”
The second infraction was related to one of Pilgrim’s emergency diesel generators, needed to power essential safety equipment when off-site power is lost. Diesel generators are equipped with control systems that regulate voltage and frequency of the electricity they supply. The diesel generators at Pilgrim were designed for electricity within a frequency range of 57 to 63 hertz (cycles per second).
Inspectors found that the trigger point for the alarm set to alert operators of a problem with frequency was set at too low a hertz level. If the frequency fell too low but not low enough to trigger the alarm, it could cause the motor on the generator to burn out.
Inspectors classified the infraction as more than minor because it adversely affected the “objective to ensure the availability, reliability and capability of systems that respond to initiating events to prevent undesirable consequences.”
The inspection team also concluded the violation reflected a shortcoming in human performance. “Between approximately 1971 and August 2017, Entergy had not adequately implemented an emergency diesel generator under-frequency limit into their procedures,” the report said. “Specifically, Entergy had not verified that the emergency generator alarm setpoint was in accordance with design basis requirements.”
A spokesman for Entergy submitted a written statement on the company’s behalf: “The report is important, and we will carefully review the two findings the NRC characterized as very low safety significance. We work to continuously strengthen our ability to self-identify and resolve issues in a timely, effective manner.”
Entergy has entered the findings into its corrective action program “to ensure resolution and to prevent recurrence.”
Lochbaum said that to conclude a performance grade of 67 percent, based on problems found in two out of six systems, was “misleading.”
“While the team examined only six components, they essentially put those six components under a microscope,” he wrote in an email. “Each component has dozens of facets. The NRC found fault with two of the facets in this case.”
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