Severe nuclear power plant accidents pose a "very small" risk to the American public's health because plant operators should have enough time to prevent damage and stop radioactive material from being released, federal regulators said today.

The Nuclear Regulatory Commission issued a draft report today that analyzed two plants in Pennsylvania and Virginia and said preliminary findings show U.S. reactor operators can prevent accidents.

If an accident does occur, NRC said, there is virtually no risk of immediate deaths and the public will see only a "very, very small increase" in the risk of long-term cancer deaths.

"The calculated cancer fatality risks from the selected, important scenarios analyzed in [the study] are ... millions of times lower than the general U.S. cancer fatality risk," the commission said.

The agency analyzed possible accidents at Dominion's Surry Power Station near Surry, Va., and Exelon Corp.'s Peach Bottom Atomic Power Station near Delta, Pa. Those plants typify the bulk of the United States' nuclear fleet -- namely, boiling water reactor and pressurized water reactor designs, NRC said.

The commission said it reached its findings by combining up-to-date information about the plants' layout and operations with local population data and emergency preparedness plans.

The study, called the "State-of-the-Art Reactor Consequence Analyses" (SOARCA), found there is "essentially zero risk" that a severe accident would cause early deaths from radiation exposure.

In the most severe accidents, NRC staff found, core damage would begin within one to three hours and the reactor vessel would begin to fail in about eight hours. Notably, radioactive material would be released at Peach Bottom within eight hours and within 25 hours at the Surry plant if operators there could not restore cooling.

Overall, NRC said radioactive releases were found to be "delayed, smaller, and more dispersed relative" to earlier NRC studies.

The agency's analysis arrives almost one year after Japan's Fukushima Daiichi nuclear reactor complex was slammed by a magnitude-9 earthquake and tsunami, which caused three of the reactors to melt down and release radioactive material.

NRC said it was just wrapping up its report last year when the accident occurred, and that Fukushima had many similarities to scenarios that could unfold at the Peach Bottom plant.

Although the Japanese crisis prompted NRC to re-evaluate its safety regulations, commission staff said today that no plants in the United States were found to be dangerous and safety upgrades currently under way are simply "enhancements."

NRC staff members said they plan to issue a final report to the full five-member commission this summer, and the panel could then decide to ask for further studies.

Click here to read the NRC report.