Energy Northwest's nuclear power plant near Richland was the only one in the nation to have three special inspections by the Nuclear Regulatory Commission in 2013, according to a report by the Union of Concerned Scientists.
No other U.S. plant has had that many special inspections in a single year since the group began preparing annual nuclear power plant safety reports four years ago.
"Time will tell whether the trio of near misses at the Columbia Generating Station was merely bad luck or indicative of broader programmatic deficiencies," the report said.
Energy Northwest objected to the term "near misses," saying the NRC found no violation during two of the special inspections.
The violations the NRC found related to the third inspection were categorized as "green" -- having very low safety significance. Energy Northwest was not cited.
The Columbia Generating Station started the year with a strong enough performance that the NRC placed it in a category that requires only routine oversight and it remained in that category during and after the special inspections, according to Energy Northwest.
Energy Northwest identified potential security issues on Feb. 6 and Sept. 12, and reported them to the NRC "out of an abundance of caution," Energy Northwest spokesman Mike Paoli said. That led to two special inspections.
Information about the security issues was not made public by the NRC, a policy adopted in response to the Sept. 11 terrorist attacks.
The third issue that led to a special inspection began with the discovery during the spring refueling outage that an air filter had been installed backward in 2012. It was part of a heat exchanger system that cools a room housing electrical circuit breakers and batteries to provide direct current to switches and alarms. Dust and materials from the air filter on the cooling coils reduced the cooling capacity of the system.
However, there was no concern about the cooling system being able to keep the room cool during normal operations and an alarm would have sounded if temperatures rose enough to create a problem, according to Energy Northwest. A separate backup system was available to provide cooling in case of an emergency.
Five green violations were found, but the Union of Concerned Scientists said safety margins, while reduced, had not been compromised.
However, the report said the group was concerned that the NRC inspectors had to press Energy Northwest to find underlying causes.
That was not the case, Paoli said.
Energy Northwest was evaluating degradation to the air handling units when the NRC raised issues about whether Energy Northwest was documenting the evaluation to the level required based on its significance, said Don Gregoire, Energy Northwest's director of regulatory affairs. But the thoroughness of the investigation was not at issue.
Two more green violations were issued as the NRC recommended that evaluation and testing programs for devices to minimize corrosion or to test the tubes in the air-handling units be broadened to better detect problems.
The remaining green violations were because there should have been specific guidelines on how to install filters to prevent the backward filter and because an air conditioning unit performed below requirements, but only slightly below, according to Energy Northwest.
The Union of Concerned Scientists said it was concerned that fixes made related to the cooling system at Energy Northwest in 1989 had been undermined since then. The fixes were required by the NRC at all plants across the nation in 1989.
Energy Northwest said NRC had accepted its improved program and had been inspecting the cooling system to the program's requirements since 1989.
w Annette Cary: 582-1533; firstname.lastname@example.org; Twitter: @HanfordNews