GWEN IFILL: In the U.S., the Food and Drug Administration has banned imports of dairy products and produce from areas near the Fukushima plant.
Now, the impact on the nuclear energy industry here at home. There hasn't been a nuclear accident in the U.S. since Three Mile Island in 1979, but opposition to building nuclear plants in this country is on the rise. A CBS poll found half of all Americans now opposed to new reactors, up from 34 percent in 2008.
The Union of Concerned Scientists also points out that the government found a series of safety problems at 14 U.S. reactors in 2010. None led to a serious accident.
NewsHour science correspondent Miles O'Brien reports on where U.S. nuclear policy stands right now.
MILES O'BRIEN: It was the perfect storm meeting an imperfect design. And now the U.S. nuclear industry is bracing for a backlash, even as it breaks ground on what it hoped was a new era.
The Fukushima Daiichi nuclear power plant almost made it through, but almost is not good enough in this business.
JAMES MAHAFFEY, "Atomic Awakening": At its core, it's very simple. It's the -- implementation of it becomes extremely complicated.
MILES O'BRIEN: As engineer and author Jim Mahaffey explains, a nuclear power plant runs on uranium-235, pound for pound at least three million times more energetic than a gallon of gasoline. Pellets of the radioactive element are stacked in long zirconium rods.
When they are clustered in just the right way, atoms begin splitting in a chain reaction called fission, which boils water, creating steam to spin huge turbine generators.
JAMES MAHAFFEY: There's nothing particularly safe about releasing a billion watts of energy in a modest-size concrete building. So, what you do is, you force it to be safe by engineering. Every complication in a nuclear plant is to make it so it won't kill you.
MILES O'BRIEN: When an earthquake hits, control rods that absorb neutrons automatically drop into the fuel cluster to stop the fission. That worked fine at Fukushima.
EDWIN LYMAN, Union of Concerned Scientists: But even if you do shut down the reaction, the fuel still gives off heat, a lot of heat for a very long time. And that's because, when you split uranium, you generate what are called fission products. These are radioactive isotopes that decay at a rate so that they generate a lot of heat. And you have to worry about that heat for a long time.
MILES O'BRIEN: Physicist Ed Lyman is with the Union of Concerned Scientists.
EDWIN LYMAN: That's why you need to continue to provide a lot of cooling even after the reactor shuts down for some period of time, because if you don't have that cooling, the temperature can rise to the point where it will actually destroy the fuel.
MILES O'BRIEN: The water pumps are designed to keep running on power from the grid, but the earthquake knocked that out. Diesel generators are the last line of defense, but in this case, they were swamped by the tsunami. And that is the Achilles' heel that turned this into the worst reactor meltdown since Chernobyl.
If they had had that emergency power, we wouldn't be seeing what we're seeing right now, presumably, though?
JIM FERLAND, Westinghouse Americas: Absolutely not. If those diesels had not been destroyed in the tsunami, it would have been a -- the plant would have gone into a normal shutdown evolution.
MILES O'BRIEN: Jim Ferland is president of Westinghouse Americas, which is building a new generation of nuclear reactors that do not rely on emergency power during a so-called station blackout.
If you're in a blackout situation, the water comes down and goes on the -- in between the outside layer and the inner layer there of that...
JIM FERLAND: That's right.
MILES O'BRIEN: The AP1000 reactor has a passive cooling system, a reservoir of water at the top of the containment vessel designed to circulate for three days using only gravity and convection.
WILLIAM MEADER, Westinghouse Americas engineer: We don't know the details of what occurred, but we think this design could have -- maybe could have -- maybe could have prevented that.
MILES O'BRIEN: How will we know if this really will work in the real world?
WILLIAM MEADER: The way we know this will really work is we're going to go over to Sanmen to test this. This is what we do, is, we do the design.
MILES O'BRIEN: Startup test director Bill Meader is part of a team headed to the Sanmen nuclear plant in China. It is the first AP1000 nuclear plant. And they plan to wring it out and bring it online over the next few years.
Sanmen is slated to be the first, but not the last, of this Generation III+ design. Utilities in Georgia and South Carolina are building four of them. They are the first new nuclear power plants to be built in the U.S. in 30 years.
Would you say there was or is a nuclear renaissance in the United States?
JIM FERLAND: I would say both. I would say, clearly, there was a nuclear renaissance. And the fundamental drivers behind the nuclear renaissance remain in place today. We have a growing demand for electricity in the United States.
There's an awful lot of emphasis today, as there should be, on clean energy generation, CO2, reducing air emissions. And nuclear fits that bill very well.
MILES O'BRIEN: It looks like a furnace and a hot water heater, but its a little more complicated, isn't it?
GREG WEAVER: A little bit more, but, really, not that much more.
MILES O'BRIEN: Greg Weaver runs a first-of-its-kind facility to train Westinghouse engineers on how to run an AP1000 reactor. This rig contains many of the valves, sensors and pumps as in the real thing. It is connected to a computerized control room simulator that is filled with screens and mice, instead of analog gauges and switches.
How much does this increase safety, having this kind of awareness?
PAUL HIPPELY, Westinghouse simulator trainer: Oh, significantly. It gives you the familiarity for the operators, so they have a good understanding and they can react better than in -- with the familiarity of the events.
MILES O'BRIEN: Paul Hippely runs this state-of-the-art simulator. The goal here is to make running a nuclear power plant easier, more standardized, more automated.
Charles Ferguson heads the Federation of American Scientists.
CHARLES FERGUSON, Federation of American Scientists: Humans sometimes can compound errors. And so now the shift is to more kind of economical design, of more of a simpler design, design that is using more of the natural forces of nature to put these complex machines, these nuclear power plants, into safer conditions.
MILES O'BRIEN: The experts will remind you, if the operators at Three Mile Island had simply watched and taken no action on that fateful day in 1979, there would have been no meltdown. Instead, when a valve got stuck, they scrambled to save a pump, misinterpreting instruments, causing a partial meltdown.
Is the human being still the weak link in nuclear power?
JAMES MAHAFFEY: It is a weakness. It's being phased out. New reactors, the III+ generation, the IV generation, it's a turnkey operation. And you don't even have to turn the key anymore. You just walk in and indicate in some way that you would like for the power to start flowing, and the reactor will start itself up and do it quite efficiently.
MILES O'BRIEN: But for all the advancement touted by Westinghouse, the nuclear industry still has not grappled with another Achilles' heel: what to do with its radioactive waste.
Not a single country with nuclear power has opened a long-term storage site for the used uranium. In the U.S., plans to create such a facility at Yucca Mountain, Nev., have stalled, despite exhaustive and dramatic tests aimed at demonstrating the material is safe to ship and store.
The upshot? Spent fuel rods, which are still radioactive, but no longer useful in a reactor, are routinely stored in pools of water to keep them cool and provide a radiation shield. In Japan, the pools are elevated above the reactor, cheaper and easier that way, but as the Japanese struggle to keep the spent fuel at Fukushima from burning, a reminder of another design flaw. There are 31 reactors in the U.S. of the same design.
EDWIN LYMAN: What's more frightening is that, in this country, those pools are -- have much more spent fuel in them than pools in Japan at the affected reactors.
MILES O'BRIEN: We pack them more densely in the U.S.?
EDWIN LYMAN: That's right. The -- those pools were not designed to hold as much fuel as they currently do.
MILES O'BRIEN: Nuclear operators say the pools have been upgraded to accommodate the added fuel. They say they are taking notes as details of the accident in Japan come to light, reminded that an identical valve failure that started the trouble at Three Mile Island occurred at another nuclear plant in Ohio 18 months before. But that crucial piece of information was not shared.
Marvin Fertel Heads the Nuclear Energy Institute, which represents operator of all 104 nuclear power plants in the U.S.
MARVIN FERTEL, Nuclear Energy Institute: There's no question it's going to impact the perception of the industry. I think that we need to do a really good job, as an industry and as a government and as a credible regulator, of explaining to the American public why the plants are safe, why we are taking things from Japan and making the plants safer, if that's necessary. I don't think it's going to affect the plants that are going forward right now.
MILES O'BRIEN: But U.S. regulators have yet to give Westinghouse final design certification for its AP1000 reactors, even as the work continues in Georgia and South Carolina. They were expected to receive it by the end of the summer, but there is opposition brewing on Capitol Hill.
Congressman Edward Markey of Massachusetts says the AP1000 needs further testing. He fired off a letter to the Nuclear Regulatory Commission, writing, "Taxpayer dollars should not be spent on reactors that could be at risk of suffering a catastrophic core meltdown in the event of an aircraft strike or a major earthquake."
Westinghouse insists its new reactor design is safe, but the company is willing to make design changes, if required.
JIM FERLAND: If there are lessons learned coming out of Japan that rightfully should be included in the AP1000, they will. If it takes a little extra time, so be it.
MILES O'BRIEN: But the safety does not come cheap. A nuclear plant is astronomically expensive, $8 billion, give or take. And there would likely be no construction in the U.S. without government loan guarantees.
U.S. taxpayers are guaranteeing $18.5 billion in loans to finance new reactors. The Obama administration is pressing ahead with plans to add another $36 billion in guarantees.
CHARLES FERGUSON: There are those who are critics saying, wait a minute. When does this end? Do we keep subsidizing this industry? Shouldn't -- shouldn't this be a mature industry? When is it going to able to stand on its own two feet?
JIM FERLAND: My take is that the loan guarantees will help kick-start this industry. It makes it a little bit easier for a utility to make the decision to build. So, the loan guarantees, to me, make sense.
MILES O'BRIEN: But does nuclear power make sense? It's expensive, very complex and accidents can be devastating. Before the meltdown in Japan, American support for nuclear power as an alternative to fossil fuels had reached a new high. But that support appears to be evaporating quickly and opponents of nuclear power are emboldened.
Robert Alvarez is with the Institute for Policy Studies.
ROBERT ALVAREZ, Institute for Policy Studies: Nature has a way of greatly exceeding the assumptions and scientific assumptions and statistics and engineering judgment of the nuclear industry. There is no nuclear renaissance. I think that we are looking at a moribund industry that's going to probably stay that way in this country.
MILES O'BRIEN: The nuclear industry in the U.S. may be awakening from a long slumber just in time to grapple with a dreaded nightmare.
GWEN IFILL: This evening, the Nuclear Regulatory Commission voted to conduct new safety reviews of U.S. reactors in response to the Japan disaster.