Chernobyl was directly responsible for at least 56 deaths and as many as 4,000 more, according to the World Health Organization, though other estimates vary, and spread radioactive material as far as the U.K. Three Mile Island has never been conclusively linked to any deaths or health effects, though some individuals may have received radiation doses of as high as 100 millirems. An average American is exposed to an average of 360 millirems per year from natural sources of radiation, such as cosmic rays from space.
And nuclear power plants have been operating in the U.S. for 50 years without exposing workers or residents in surrounding areas to excessive radiation. "Radiation is mundane, it's a weak carcinogen," says Rod Reed, a senior health physicist at the NRC. "It leads to very mundane changes, not three-eyed fish."
In fact, a typical coal-fired power plant exposes local residents to as many as 18 millirems of radiation yearly, whereas a nuclear power plant emits less than six millirems per annum, according to researchers at Oak Ridge National Laboratory.
Reed adds: "Radiation should be respected, not feared."
Ultimately, the safety of a nuclear power plant depends on the operation of its various safety systems, from cooling water to the control rods that modify or halt the nuclear reaction. Such shutdowns are known as "scrams". (Their name derives from the safety control rods that were moved by ropes on the first primitive reactor. To prevent a runaway reaction, an ax wielder stood ready to literally chop the rope, which would drop the control rods and stop nuclear fission if a meltdown was imminent—so literally safety control rod ax man.) Scrams can occur for everything from a loss of coolant to a loss of auxiliary power.
And there's a new problem that has appeared in recent years with surging demand for new parts: counterfeits. The NRC has found fake and possibly faulty valves and breakers—those not actually verified to stand up to the rigors of a nuclear power plant—at two facilities, according to a notice in 2008. "These recent examples have not found their way into the safety systems of our nuclear plants, but I'm sure you can appreciate the seriousness of the situation if that were to happen," NRC commissioner Peter Lyons said in a speech to the ANS last June. "The volume of the flow of parts and components will surge with new plant construction, and we all must remain vigilant."
"The nuclear industry in general is an industry where it's in our best interest that everybody builds safe and reliable plants," said Steve Winn, executive vice president of strategy, environment and nuclear development at Princeton, N.J.–based utility NRG Energy, in an interview with Scientific American in 2007. "All of us are only as good as the weakest member of the group."
The goal for nuclear power plant operators and builders is to reduce the risk of a serious accident to less than one in 100,000 or more years, according to the NRC. "There is no such thing as zero risk," the commission's Ricci says. "We cannot guarantee perfect protection."
But there has already been a core damage event in the U.S. nuclear industry—TMI Unit 2—"so we've already blown the goal," says Rick DeVercelly, a former operator at the Vermont Yankee and James A. Fitzpatrick (near Oswego, N.Y.) nuclear plants, and now a trainer at the NRC.