Ten years ago Tuesday, an accident at the Three Mile Island plant in Pennsylvania changed the way Americans view nuclear power.

Unhappily, those changes could persist even though they are based on emotions unwarranted by the facts.The facts are that:

- Even though a faulty valve ended up totally disabling TMI's Unit 2, the reactor remained intact.

- Indeed, the containment features of the reactor worked, holding in an estimated 18 billion curies of radioactivity - more than 100 times the amount released in the 1986 accident at the Chernobyl reactor in Russia.

- Though some radioactive material was released into the environment, it was insignificant. The only serious health effects were trauma resulting from fright.

- The bottom line is that no member of the public has ever been harmed by a U.S. nuclear power plant.

Yet the fears generated by what happened at Three Mile Island were so massive and persistent that not a single new nuclear power plant has been ordered in the U.S. since that episode and more 100 than have been canceled.

But Americans didn't cancel or curtail their demands for more electricity. As a result, they keep using more coal, oil, and gas even though these fuels impair public health by fouling the air we all breathe.

Maybe a clean, cheap source of energy will be provided by the apparent research breakthrough in Utah on cold fusion. Maybe. But even if all goes well, it could take a decade or two before this new technique gets out of the laboratory and into practical application.

Meanwhile, there are some encouraging developments regarding fission power. Science has developed new reactors that are smaller, simpler, and safer. Tough rules imposed since Three Mile Island have sharply reduced unplanned automatic shutdowns at U.S. nuclear reactors. What's more, the Nuclear Regulatory Commission is on the verge of adopting rule changes, including design standardization, that could speed the approval of nuclear plants.

After 10 years of exaggerated fears since Three Mile Island, it's time the U.S. stopped turning its back on nuclear power and started facing this promising source of abundant power more confidently.