LOU DOBBS: In another concern in the war against terrorism, the nation's nuclear power plants: are they vulnerable to assault? We have a report for you tonight that may well shock you . . . . Another potential target for terrorists could well be the nation's nuclear power plants. There are more than 100 of them, and an attack from the air or ground could prove, of course, catastrophic.

Steve Young has the story.

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STEVE YOUNG, CNN CORRESPONDENT (voice-over): At its annual conference in Vienna, the International Atomic Energy Agency said this week that, like the World Trade Center, America's nuclear power plants were built to withstand hits by big 1960s jets, not today's wide- bodied, fully-fueled behemoths.

DAVID KYD, INT'L ATOMIC ENERGY AGENCY: If it were successful, which is a very extreme scenario, then the containment could be breached and the cooling system of the reactor could be impaired to the point where radio activity might well be set free.

YOUNG: It took four or more terrorists to turn hijacked planes into instruments of catastrophe. But just three mock terrorists, in controlled exercises run since 1993 by the Nuclear Regulatory Commission, have brought dozens of U.S. nuclear plants to the brink of war game meltdown.

PAUL LEVENTHAL, NUCLEAR CONTROL INSTITUTE: In half the cases of the 103 operational reactors in the country, they failed to repel this very small force, and they were able to simulate destruction of redundant cooling systems that would result in, if it were real, destruction, sever damage to core and a meltdown.

YOUNG: This tape of a terrorist test, obtained from a Congressional source, was shot by a nuclear utility in the South. The company passed the NRC exercise with flying colors, even added music for an internal pep rally. But there was nothing to celebrate after it faced a later test and flunked, even though plant operators get six months advance notice, to the day.

Before last week's horrors, the power industry was trying to convince the Nuclear Regulatory Commission to back off and let atomic power plants run their own terrorist tests. MONEYLINE today tried asking NRC Chairman Richard Meserve where he stands on that now. A spokesman said he decided this was not the appropriate time to do an interview.

JOSEPH COLVIN, NUCLEAR ENERGY INSTITUTE (industry lobbyist): The intent of proposing the changes to the security program were to enhance the effectiveness and the completeness of our evaluations of our security programs.

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YOUNG: The Nuclear Control Institute (industry critic) is now calling for National Guard troops to be stationed at the nation's 103 nuclear power plants to guard against ground terrorism. It also wants the emplacement of radar-control anticraft weapons operated by the military, to prevent terror from above -- Lou.

DOBBS: Steve, any response on those questions?

YOUNG: Not yet, Lou. And you have to consider that in the scenario, as horrible as the death toll is behind me, you can see a death toll double and triple in long-range cancer.

DOBBS: Steve, Thank you very much. Steve Young.