Washington (Platts)--6Sep2012/652 pm EDT/2252 GMT

The number of nuclear power reactors under heightened oversight by the US Nuclear Regulatory Commission more than doubled in first-half 2012, to 41 units from 15 in second-half 2011, according to data released by the agency late Thursday.

As of June 30, 62 of 104 operating nuclear units in the US "fully met all safety and security performance objectives and were inspected by NRC using the normal inspection program," the agency said.

Those are the plants in the first column of the oversight process. In the five-column action matrix of NRC's reactor oversight process, Column 1 plants require the least amount of agency oversight, while plants in Column 4 receive the most NRC attention short of a mandated shutdown under the "unacceptable performance" criteria of Column 5.

Thirty-four units were in Column 2, "assessed as needing to resolve one or two items of low safety significance. This represents an increase from the previous oversight cycle," NRC said.

Six units were in Column 3 "with degraded performance," it said.

The Tennessee Valley Authority's Browns Ferry-1 unit in Alabama is in Column 4 "and requires increased oversight due to a safety finding of high significance, which will include additional inspections to confirm the plant's performance issues are being addressed," NRC said.

Omaha Public Power District's Fort Calhoun in Nebraska "is in an extended shutdown with significant performance issues and is currently under a special NRC oversight program distinct from the normal performance levels," so it will not receive a mid-cycle assessment, the agency said.

NRC spokesman David McIntyre said in an interview Thursday that the increase in oversight during the first half of the year reflects "the NRC at work."

Staff at the agency's Office of Nuclear Reactor Regulation, which oversees operating US nuclear power plants, is "not worried" about the jump in the number of plants under increased oversight, partly because many of the reactors are in Column 2 and have "only one or two minor issues" to address, McIntyre said.

The ROP "is designed to find issues before they become major problems, and to fix them before they become major," McIntyre said.

Nuclear Energy Institute spokesman Steven Kerekes said in an email reply to questions Thursday that "in part," the rise in increased oversight reflects the reintegration this year of security inspection findings into the ROP's action matrix. Previously, security findings were considered under a separate part of the ROP from safety findings, Kerekes said.

--Steven Dolley, steven_dolley@platts.com --Edited by Lisa Miller, lisa_miller@platts.com