He warned that there are dangers of more leaks and told people living within 19 miles of the Fukushima Dai-ichi complex to stay indoors to avoid radiation sickness.
Chief Cabinet Secretary Yukio Edano said a fourth reactor at the complex was on fire and more radiation had been released.
"Now we are talking about levels that can damage human health. These are readings taken near the area where we believe the releases are happening. Far away, the levels should be lower," Edano said.
The cascading troubles in the nuclear plant compounded the immense challenges faced by the Tokyo government, already struggling to send relief to hundreds of thousands of people along the country's quake- and tsunami-ravaged coast where at least 10,000 people are believed to have died.
About 190 people had been exposed to some radiation from the plant, officials said.
The Fukushima Dai-ichi plant is in a high-frequency earthquake zone about 170 miles northeast of Tokyo.
Quakes are possible in Tennessee.
TVA's Browns Ferry plant in Athens, Ala., is built to withstand a quake with a magnitude of 6 from the New Madrid fault, according to TVA.
Smith said that while tsunamis are out of the question, earthquakes and hurricanes are possible in Tennessee along with a break in a major dam along the Tennessee River where TVA's reactors lie, which could cause a major catastrophe here.
Smith said that the industry needs to re-evaluate its safety systems and that TVA needs to slow down its rush to build nuclear reactors.
The facilities basically boil water to create steam to turn turbines that generate electricity. Less risky options are available, he said.
A long-term analysis and plan that TVA has just completed and for which he served as an advisory panel member show that energy efficiency and alternative energy sources could offset any perceived need for nuclear power for the time being, Smith said.
Alexander notes lessons
Alexander said there are always risks with every form of energy and no one has ever died in the United States because of a commercial nuclear reactor.
While lessons should be learned, the power source shouldn't be put aside, he said.
"The 1.6 million of us who fly daily would not stop flying after a tragic airplane crash," he said.
Nuclear power provides about 15 percent of the world's electricity and about 30 percent in the TVA system, which provides electricity to almost all of Tennessee and parts of six other states.
Questions that have arisen in the situation in Japan include the safety of the pools of highly radioactive used fuel that are found at the plants, and also the safety of mixed-oxide fuel, usually called MOX, made with plutonium. It's used at one reactor there.
TVA is considering fueling with MOX, using plutonium from dismantled nuclear weapons, at some of its reactors and also has spent fuel pools at all of its plants, as do many reactors around the United States.
They are not in reactor containment buildings, which are the most strongly fortified of any structure at a plant.
Arjun Makhijani, president of the Institute for Energy and Environmental Research, said the pools, which have high levels of cesium 137 and the metal zirconium, can spontaneously combust if the temperature gets high enough, resulting in a fire "that would burn like a sparkler" as it released radioactivity.
"Many of the vulnerabilities are in the spent fuel pools," he said.
Makhijani, who has a doctorate in engineering from the University of California at Berkeley where he specialized in nuclear fusion, has advocated along with others for years for dry cask storage of nuclear waste.
It's a process that Germany has taken to but the United States has seemed reluctant to adopt, perhaps because it would be at a cost to the industry, he said.
Plutonium, which is found in MOX fuel, makes the fuel more difficult to control, he said.
Japanese protests have been strong against MOX fuel and also, at times, against nuclear power.
French power is 80 percent nuclear
The French, who get 80 percent of their electricity from nuclear reactors, were among those alarmed at the situation in Japan.
The French Embassy in Japan had warned on its website that there was a possibility that a radioactive plume of smoke could be released in an explosion that "could reach Tokyo within a few hours, depending on the direction and speed of the wind," according to Reuters.