Pilgrim scram valve fails again
Is this a sign of an aging plant past its prime?
The second “event” at Pilgrim in as many weeks – the failure of a “scram discharge valve” – is also the second time this particular valve has failed in the last two months.
The scram discharge volume valve – referred to in the event releases as CV-302-22B – failed Feb. 18, a week after the blizzard knocked out power to the plant. (In another case of twos, Pilgrim also lost power twice during the storm.). The valve failed again last Friday, March 1.
According to the Union of Concerned Scientists (UCS), the CV-302-22B is one of the valves on the drain line from the scram discharge volume, a metal tank that is supposed to contain all of the water vented during a scram (a sudden, rapid, shut down of the reactor).
“When a scram signal occurs,” the UCS reported, “this valve automatically closes, or is designed to do so. Whether it does so is another matter.”
For critics of the plant, including EcoLaw.org Founder Meg Sheehan, this is a sure sign that the plant is past its prime.
“Pilgrim is old and worn out,” Sheehan wrote on her blog this week. “It presents an unacceptable risk to our region, and this is just one more example of that.”
A 1975 report on reactor safety, widely known as the Rassmussen Report, argues against that conclusion.
That report specifically stated that the valves in question have only a “one in a million” chance of interfering with a reactor shut down.
But the UCS said the Brown’s Ferry Nuclear Power Plant in Alabama must have hit the lottery, because in 1980 a plugged scram discharge valve prevented plant operators from successfully removing all of its control rods, three times, before the reactor staff was able to complete a planned shut down of their reactor.
That event at Brown’s Ferry did not occur during an emergency, however, and the 15 minutes it took to withdraw all of the reactor’s control rods did not, therefore, result in a disaster.
This week’s failure of Pilgrim’s scram valve, the official event notice released by Pilgrim concluded, “has no impact on the health and safety of the public.”
Plant staff had actually been monitoring the valve since it first failed in mid-February.
“A similar event report was generated for the same valve on Feb. 18, 2013,” the event-notification report states. “Compensatory measures applicable to the original event report included a revised lubrication application and additional surveillance testing.”
In other words, Pilgrim has been testing this valve since it first failed.
According to the NRC, the valve was lubricated, retested and restored to operability soon after the issue was discovered.
But tests conducted March 1, Pilgrim stated, “did not meet opening stroke time operability requirements for the valve.”
According to the NRC, during the power outages that shut down the plant twice during the February blizzard, the valve worked properly to support the scram.
“That is, it closed within the timeframe necessary to support the scram,” NRC spokesman Neil Sheehan told the Old Colony.
“The problem resulting in the report on Feb. 18 was discovered,” Neil added, “during routine surveillance testing conducted on these valves in the ‘open’ direction and was unrelated to any of the shutdowns.”
The NRC spokesman acknowledged that this valve plays an important role in supporting the scram function.
“That said, nuclear power plants have numerous systems and components that are important to safety,” Neil said. “The ‘defense-in-depth’ approach for nuclear power plants is based on multiple layers of safety through redundant systems and equipment.”
Neil wouldn’t comment directly on the assertion that the problems with this valve were related to the plants overall age.
“The company (Entergy) is continuing to evaluate the exact cause of the slowness of the valve to operate in the open direction,” Neil concluded. “Our inspectors will review the results of that review.”