As Japan grapples with a nuclear reactor crisis in the aftermath of the devastating earthquake and tsunami, many in the U.S. have been wondering about the safety of nuclear power plants closer to home.

In a well-timed report issued yesterday, the Union of Concerned Scientists examines a number of incidents and "near-misses" at plants in the United States in 2010 and gives the U.S. Nuclear Regulatory Commission mixed reviews on its role as the nation's nuclear safety inspector.

The timing of the report is also significant as it coincided with President Obama's announcement yesterday that he has asked the NRC to perform a comprehensive review of the safety of all nuclear plants in the U.S.

The UCS report looked specifically at 14 special inspections that the NRC conducted and documented last year in response to safety problems, security concerns, and other issues at different nuclear plants. Though the group commended the NRC for its positive actions in certain incidents, it also found that the agency tolerated known safety problems in other cases.

As one of several positive examples of the NRC's effectiveness, the UCS cited the agency's reaction to an incident at the Oconee nuclear plant in South Carolina. After fixing a problem with a crucial safety value at its Unit 1 reactor, the owner didn't feel the need to test the same components at Units 2 and 3 despite the NRC's insistence. But the agency refused to budge.

"NRC inspectors persistently challenged lame excuse after lame excuse until the company finally agreed to test the other two units," the report noted. "When it did so, their systems failed, and NRC inspectors ensured that the company corrected the problems."

But the report highlighted several examples where it felt the NRC failed to act in the public's interest.

In one case at the Peach Bottom nuclear facility in Pennsylvania, workers at the plant were required to periodically test the control rods, which are used to control chain reactions. To circumvent regulations that would have forced a plant shutdown, workers slowed down the control rod testing, said the report. Inspectors from the NRC knew about both the problem with the rods and the plant's attempts to skirt past the testing, according to the UCS, but failed to respond properly.

The UCS did acknowledge that its review of the 14 incidents in question were just a cross-section and didn't necessarily represent the NRC's "best and worst actions" of last year.

"Instead, the examples highlight patterns of NRC behavior that contributed to these outcomes," the report said. "The positive examples clearly show that the NRC can be an effective regulator. The negative examples attest that the agency still has work to do to become the regulator of nuclear power that the public deserves."

In response to the UCS's findings, a spokesman for the NRC told CNET that the agency has not yet had a chance to review the report, but it did issue the following statement:

"We can say that the NRC's current Reactor Oversight Process has been in place since April 2000 and has worked effectively to gauge the performance of U.S. nuclear power plants. It does so through a combination of Performance Indicators, such as the number of unplanned shutdowns, and NRC inspection findings. If the NRC observes any indications of declining performance, the agency can ratchet up its oversight to ensure issues are being addressed in a timely manner. The NRC does not hesitate to increase its level of scrutiny wherever and whenever that is warranted."

The NRC said further: "It is important to note that many of these issues were caught by NRC inspectors who are at the plants on a daily basis. This is a cataloguing of NRC actions on things either found by us or brought to us by the operator."

The report itself is the first in a new annual series from the UCS to look at safety-related issues at nuclear power plants and examine the NRC's effectiveness in addressing them. Formed more than 40 years ago with nuclear power plant safety its initial focus, the UCS is a nonprofit alliance with over 250,000 members, including physicists, biologists, teachers, students, and business people.