Tshe “impossible” is underway in Japan. A 9.0 magnitude earthquake has badly shaken up several “indestructible” nuclear plants. Reactor No. 1 at the quake-damaged Fukushima Daiichi Nuclear Power Station is in partial meltdown, and reactor No. 3 may soon join it.

In an act of naked desperation, plant officials are blindly pumping seawater into reactor No. 1 in an effort to cool its fuel rods.

In all, four nuclear plants across northeast Japan are damaged, with a total of six reactors now having trouble cooling their radioactive uranium fuel rods. The worst off is the Fukushima Daiichi nuclear complex, where the No. 1 reactor containment building exploded on Saturday when radioactive hydrogen gas was vented from the containment vessel inside it.

As day three of this disaster drew to a close, I reached former Nuclear Regulatory Commissioner Peter Bradford by phone at his home in Peru, Vermont. Now an adjunct professor at Vermont Law School, Bradford was a Carter-appointee to the Nuclear Regulatory Commission (NRC) and was on duty for the partial meltdown at Three Mile Island in 1979.

“It’s very hard to know what’s going on,” says Bradford with a grim calm. “During Three Mile Island very much of what we believed to be true on day three turned out to be untrue in subsequent days. Even now, we still don’t know how much radiation was actually released. It was less than was later released at Chernobyl.”

If the containment vessel at the partially melted-down Fukushima reactor No. 1 holds, most of the radiation should be held within the site.

That is the Three Mile Island scenario, which the International Atomic Energy Agency rates as a four on its Nuclear and Radiological Events Scale. The crisis in Japan is, so far, a five. Chernobyl was a seven.

If the containment vessel breaks – or is already broken, cracked and leaking due to the earthquake – and if the meltdown keeps going, officials would have to switch from trying to cool the reactor to burying it with tons of sand and cement. That would be the Chernobyl scenario, and it would mean that massive amounts of radioactive iodine, cesium and other very poisonous stuff would escape into the atmosphere.

This contamination would be deadly close to the site, but could reach the West Coast and even the East Coast of the United States – though in a very defuse form.

In the United States we have 23 reactors of the same General Electric design as Fukushima No. 1. We also have atomic plants built on fault lines. For example, the Diablo Canyon Nuclear Power Plant’s units 1 and 2 not far from Santa Barbara; and outside San Clemente there’s the San Onofre Nuclear Generating Station, which has three reactors, two of which are still running. Environmentalists protested the opening of these plants along the California coast in a region of regular and often violent seismic activity. But concerns were brushed aside with assurances that all contingencies had been accounted for.

The American fleet of 103 atomic reactors is old and rickety. But more dangerous than old equipment may be overconfidence among regulators. “The phrase ‘it can’t happen’ here is an invitation to disaster,” says Bradford.

The only thing that could make our nukes safer would be a campaign of constant, careful, rigorous (and expensive) inspection and maintenance. But the NRC does not require that. During his campaign, Obama called the NRC “a moribund agency… captive of the industry that it regulates.” And the private companies running the plants are doing all they can to squeeze more money from the aging nuke fleet.

Christian Parenti is a contributing editor at The Nation.