By WRCB Staff

CHATTANOOGA (WRCB) -- As we watch what's happening at the Fukushima Plant, we can't help but remember TVA's commitment to nuclear power, with Sequoyah at our front door, Watts Bar and Browns Ferry not far away.

For some in-depth explanation of what's going on at the nuclear power plant in Japan, we turned to a local expert.  David Lochbaum is Director of the Nuclear Safety Project and member of the Union of Concerned Scientists.

He says it's a tragic reminder that there is risk with nuclear power.

"This event is worse than a nightmare, because you wake up from a nightmare," Lochbaum told Channel 3 Eyewitness News.

He was in WRCB studios on Wednesday to record an interview to air Thursday on NBC's TODAY Show.

The earthquake and tsunami in Japan have produced the scenario nuclear engineers, like Lochbaum, thought they'd only theorize about.

Meltdown may be imminent, when reactor temperatures soar past 2,200 degrees causing fuel pellets and their containment tubes to melt and flow like lava.

"If it's successful burning through the sides or through the floor of the containment, you've created a pathway for radioactivity released by the meltdown to get outside of containment," says Lochbaum.

Levels so high, even when the lava mass cools to a rock-like substance, radiation emitted would kill a person before the heat.

How wide the danger zone depends on a number of factors.

"There are some cases around Chernobyl where 15 miles away is cleaner than 100 miles away due to the deposition from rainfall," says Lochbaum.

Lochbaum says the best case scenario, Japanese workers regain control of the cooling pools so the damage is contained at the reactor cores. 

"Most likely, this will slide past Chernobyl into first place on the atomic disaster list," says Lochbaum.

Here in the U.S., Lochbaum says all of our nuclear power plants are vulnerable if hit by the triple whammy suffered in Japan, a failure of power, back-up and battery  and a tsunami wouldn't have to be the cause.

According to the Nuclear Regulatory Commission, the Sequoyah Nuclear Plant in Soddy-Daisy, is in the top five at risk plants for an earthquake causing catastrophic failure.

Aside from natural disaster, the NRC reports 40 of the 104 nuclear power plants across America don't meet fire safety regulations.

"In the US, we have very good safety regulations.  Problem is, we have too many plants that don't meet those regulations," says Lochbaum.

TVA called off a media tour, Wednesday, at Watts Bar, site of the nation's only nuclear reactor currently under construction "while the industry focuses on events in Japan."