The Nuclear Regulator Commission (NRC) said it had issued mid-cycle assessment letters to the nation's 99 operating commercial power plants, which concern their performance form January through June of 2016. At the cycle's end on June 30, the NRC said that 96 of the plants were running in the two highest performance categories.
Of the 96 best-performing plants, 87 fully met all safety and security performance objectives and were inspected by the federal regulator using the normal “baseline” inspection program, which is designed as an appropriate regulatory response to plants that are operating at the highest standards.
Nine of those reactors needed to resolve one or two items of low safety significance, the NRC said. For these plants, inspection mandates are ramped up slightly, requiring additional inspection and follow-up of corrective actions. Plants with this level of concern included Davis-Besse in Ohio, Indian Point in New York, Oyster Creek and Salem in New Jersey, Prairie Island 2 in Minnesota, River Bend in Louisiana, Sequoyah 1 in Tennessee and Vogtle 1 and 2 in Georgia.
That leaves two performance rating categories, including the third level, requiring additional inspections relative to the second level, involvement of senior management and increased oversight into the causes of the degraded performance. However, no reactors in the country were placed in this category in the first half of the year.
Three plants were in the fourth performance category, which requires an intensified regulatory response in terms of inspections and analysis of the problem and corrective mandates. There is no fifth level of performance standard. If conditions deteriorate beyond level four, plants are ordered to close.
The NRC said Arkansas Nuclear One, Units 1 and 2 and the Pilgrim power plant in Massachusetts were in the fourth performance category. Arkansas Nuclear One's two units were in this category because of two safety findings of substantial significance. Pilgrim was in this category because of long-standing performance issues of low-to-moderate safety significance that remain a concern to the regulator.
According to NRC records, Pilgrim, a 685 MW boiling water reactor north of Boston was subject of four low to moderate level findings in the first half of the year, which is an improvement from the last six months of 2015, when it was hit with seven problems that were rated Green, the lowest incident category in the NRC system.
This week, Pilgrim suffered an unplanned shutdown, due to high water levels in the core, according to an NRC event report. Pilgrim, owned by Entergy Corporation and slated for closure in 2019, said the problem was the result of a feedwater control valve that was not working properly.
Power magazine reports that Pilgrim's frequent problems are often the result of faulty steam isolation valves (MSIV). Failures of main steam isolation valves resulted in an unplanned shut down in August 2015 and resulted in a White level finding in March of that year.
The NRC placed Arkansas Nuclear One, Units 1 and 2 in the fourth category in end-of-cycle letters issued in March 2016 concerning performances of 2015. NRC Director Bill Dean said the assessments were “the result of a holistic review of operating performance at each domestic power reactor facility.”
While issues at Pilgrim are the result of low-level concerns that continue to plague the plant, concern at Entergy's Arkansas Nuclear One are the result of a series of significant incidents at the plant, including a March 31, 2013, accident in which a Unit 1 generator's stator fell during a maintenance operation, resulting in one fatality and in eight worker injuries, four of them considered serious. The unit was shut down and repairs were estimated at up to $120 million.
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