NOVA

NARRATOR

In Japan, the bright lights never stop burning. The nation has an insatiable need for energy, but virtually no natural resources to generate it. To meet demand here, they bet big on nuclear power. (translated): We blindly believed nuclear plants were completely safe, immune from accidents, and the cheapest source of energy. But the meltdowns at Fukushima Daiichi changed everything. (explosions) (speaking Japanese) (translated): To avoid another Fukushima, we should close all nuclear plants. (demonstrators shouting in Japanese) Like the rest of the world, Japan is at a crossroads.

LAKE BARRETT

Can they get along without nuclear? Sure. The price is going to be very, very high for them. Wind and solar are not going to run the Ginza lights.

NARRATOR

How will we power the planet without wrecking the climate?

CHARLES TILL

If you really do wish to do something about climate change, nuclear is the path. We don't use nuclear, because we got freaked out in the '70s.

CROWD

No more nukes!

NARRATOR

There are some innovative ideas on the drawing boards.

LESLIE DEWAN

For my generation, we are much more concerned about climate change and global warming. We're not going to rule anything out because the issue is so important.

NARRATOR

But given its checkered past, how realistic is atomic power? Are we ready for the "Nuclear Option"? Right now on NOVA.

Major funding for NOVA is provided by the REPORTER

Breaking news-- a violent earthquake off Japan's northeast coast has rocked the nation.

REPORTER

A 7.9 earthquake in Japan, a powerful...

NARRATOR

It began with an epic earthquake at sea... (man speaking Japanese)...which spawned a giant tsunami... (man speaking Japanese)...a 45-foot high wall of water. (loud crash) It rolled over the Fukushima Daiichi nuclear power plant......triggering a cascade of failures. Three hydrogen gas explosions. (explosions) Three meltdowns. The uncontrolled release of radioactivity into the ocean and into the air. It contaminated a huge swath of land......prompting the evacuation of more than 100,000 people in a 12-mile radius. The worst affected areas, northwest of the plant, remain off-limits, abandoned. No one will be able to live here for a very long time. As the groundwater passes through the plant, it gets mixed in with the contaminated water... It's now been nearly six years since the meltdowns at Fukushima. I've been reporting on this since it happened. Six trips in as many years. I've traveled up and down the desolate evacuation zone. We are about a kilometer from the Fukushima Daiichi plant, geing particularly high readings here-- 34 microsieverts per hour. Victims who lost so much in the earthquake and tsunami in limbo, unsure when, or if, they can return home. (man speaking Japanese) (translated): I lost three family members-- my mother, my wife, and my oldest son.

WOMAN (translated)

I thought if we fixed the house, we could return here to live. I thought that when we left. But now that I see it, there's no way, no way. (sobbing)

O'BRIEN

And many are understandably opposed to nuclear power. (translated): From now on, I don't want them to build another nuclear plant ever again. That is a sentiment shared all over Japan. In Tokyo, the drumbeat remains steady. Protesters still regularly gather outside the prime minister's office to demand a permanent shutdown of all the nuclear power plants. The owner of Fukushima, the Tokyo Electric Power Company, or TEPCO, is pushing hard for permission to restart another sprawling nuclear power facility on the west coast of Japan. The Kashiwazaki-Kariwa atomic plant is the largest in the world. Or was. (shouting in Japanese) Today at KK, the operators are simulating disasters. But the plant remains closed, like nearly every other nuclear power facility in Japan. After the meltdowns at Fukushima,

TEPCO invested heavily in safety upgrades here

a 50-foot-high seawall; and watertight doors; on high ground, a fleet of backup generators and fire engines; and a five-million-gallon holding pond, designed to keep water flowing down to the reactor cores as a last resort. The price tag-- nearly $5 billion. Despite all of that, the provincial governor is opposed to a restart, as are most people who live here. (translated): I have young children. In my opinion, nuclear plants should be eliminated. (translated): Honestly, I don't want them to resume. (translated): With the impact of Fukushima, I don't want to use nuclear plants in the future.

O'BRIEN

Before the Fukushima disaster, Japan derived 30% of its electricity from 54 nuclear reactors. There were extensive plans to build two dozen more. The goal-- generate half of their electricity with nuclear by 2030. (horn honking) Now the nation relies on imported fossil fuels to fill the gap. (shouting in Japanese) Japan is at a crossroads. And so is the rest of the world. How can we answer the relentless demand for more energy without burning fossil fuels, the chief culprit in global warming? Unlike fossil fuels, nuclear is a potent source of energy that does not generate any of the greenhouse gases like carbon dioxide that trap heat in the atmosphere, warming our planet. A nuclear reactor is fueled by uranium, an element that naturally splits apart, releasing atomic particles called neutrons. It's called fission. And uranium fission can induce more fission. When a loose neutron fires into a nearby uranium nucleus, the atom becomes unstable and quickly splits. Each time an atom splits it generates heat. It's used to boil water. The steam turns turbines, generating electricity without releasing any carbon dioxide into the atmosphere. Renewable sources of energy may seem like safer, simpler ways to generate carbon-free power. But without a practical means of storing what they produce, are they reliable enough? We expect electricity on demand. What happens when the sun doesn't shine? What happens when the wind doesn't blow? We don't have a battery technology that can meet the rigorous performance requirements of the grid-- namely, super-low cost and super-long service lifetime.

MICHAEL AZIZ

Wind and solar have been growing rapidly, but we have so little storage now that even if it grows very rapidly, it'll be a long time before it has a big impact.

NATHAN MYHRVOLD

We need to have base load carbon-free power. And nuclear is a great example of something that is base load carbon-free power. (siren wailing)

O'BRIEN

But since the dawn of the nuclear age...

NEWSREEL ANNOUNCER

That signal means to stop whatever you're doing and get to the nearest safe place fast.

O'BRIEN

...fear of atomic bombs, radiation, and concerns about storing the radioactive waste have made nuclear power seem too risky.

CROWD

No more nukes! No more nukes! No more nukes!

O'BRIEN

Fukushima is a lesson in what happens when these hypothetical risks become all too real. It was one of the largest nuclear power plants in the world. Today it is still a busy, crowded workplace, but now a dangerous decommissioning site. My invitation to see it up close was unique. What next? Does three have a lot? Yes, yes... But even with special permission, getting inside is not easy, by design. Radioactive contamination has gone down, but not nearly enough to dispense with the Tyvek suits, three layers of socks, and gloves, and full face respirators. 4,000 workers endure the ritual every day. They work long and hard without access to water or a toilet. It's like being an astronaut on a spacewalk. But this mission is less scripted and rehearsed. There is no playbook. (translated): The biggest challenge is that we've never done anything like this. No one in the world has this experience. Naohiro Masuda is TEPCO's Chief Decommissioning Officer-- the man in charge of this unprecedented cleanup. It's neither a job he sought, nor could have imagined when he began working for the utility 30 years ago. (translated): My generation joined the company to generate electricity with nuclear power. That was our purpose in life. So when it comes to decommissioning work, I feel there's a bit of a dilemma, like, what is our goal here? And we still need to decide what we're going to do. For that, we need to rely on the knowledge of people around the world. He relies heavily on this man. For them to come out and to publicly say, "We need help," is different for them. Lake Barrett is one of a very select group who has some experience wi a job like this.

REPORTER

There was an accident at the Three Mile Island nuclear power plant...

O'BRIEN

The Nuclear Regulatory Commission appointed him to manage the decommissioning of Three Mile Island Unit 2 after it melted down in 1979, releasing a negligible amount of radiation into the atmosphere. There's a lot of similarities between TMI and Fukushima, and there's also a lot of differences. Fukushima is much more complex. The damage is much greater. There's three melted cores. But the fundamentals of how you address this and how you recover are similar. We are now five feet into the core. Boy, a lot of debris. So where is the melted fuel at Fukushima? In the type of reactors that were built there the uranium fuel sits inside rods, underwater, in a steel pressure vessel, surrounded by a concrete and steel containment structure inside a reactor building. All those layers of protection are there in case the cooling water stops flowing. If that happens, it quickly boils away, exposing the fuel, and it melts, turning into radioactive magma. Engineers have sent robotic cameras into the containment structure to try to get a glimpse, but the cameras quickly fail after they are bombarded by radiation. They do know the damaged cores are inside their containment structures, but it is likely that they melted through the reactor pressure vessels onto the concrete floor below.

BARRETT

Is it in one big vertical lump on the floor underneath it, or did it come down and flow like lava in a volcano, and move out to the sides? We don't know yet.

O'BRIEN

Answering the question won't be easy. It's just too hazardous to get anywhere near the melted fuel. But a team of scientists and engineers from the Los Alamos National laboratory is helping TEPCO get some answers.

MAN

Channel seven's on? Channel seven's on.

O'BRIEN

They are building a sensing device that detects muons, which begin as subatomic particles in outer space before reaching the Earth's atmosphere. They can be used as a tool to see the melted uranium fuel. Muons are stopped... slowed... or deflected, depending on the density of the matter they are passing through. Muons are like heavy electrons. They don't have a nuclear interaction. In this demonstration, they used muon detectors to create an MRI-like image of this half sphere of lead. At Fukushima, muon detectors like these, placed strategically around the very dense uranium cores, can work together to pinpoint the location and shape of the melted fuel. The technique works... in simulations. We can see where the core was, we can see the bottom of the pressure vessel, and we can see if there's material in the core region, if there's material that's in the bottom of the pressure vessel. And we can actually measure if there's any uranium there, if there's a lot of uranium there, how much is left. So this is really good news. The detectors will be run for months to gather sufficient data to give engineers the sharpest possible picture inside a lethally hazardous place that none of them can ever visit. At Fukushima right now, the most urgent problem is water-- a steady torrent of radioactive water. The plant is wedged between a mountain range and the Pacific. When the rain falls, it flows toward the ocean on the surface and underground. The earthquake on March 11, 2011 created numerous breaches in the basements of the reactor buildings. To keep the melted uranium cores cool, TEPCO pumps in 100,000 gallons of water each day.

BARRETT

The water touches the core, becomes highly contaminated, and flows out through these penetrations that are leaking onto the floor of the reactor building.

O'BRIEN

That's where it mixes with groundwater that has seeped into the basement. 100,000 gallons of water is contaminated each and every day. To keep it from leaking into the ocean, they employ a network of pumps, sending the water through a series of huge filtering plants that use various types of fine-grained materials that naturally attract and bind with radioactive elements. They remove cesium, strontium, plutonium and about 60 others. All that remains is a radioactive form of hydrogen called tritium.

KEN BUESSELER

Tritium is very hard. It's in water itself. That's something that you just can't remove by any methods that I know of in a straightforward way on that scale. So they're going to have to release it.

O'BRIEN

Dangerous as that may sound, scientists say the risk is relatively low.

BUESSELER

Tritium was not released in very high quantities from Fukushima relative to what we released in the atmosphere in the 1960s when we blew off hydrogen bombs. There was a lot of tritium put into our oceans. So we're going to be adding in a small amount of tritium to an ocean that already has tritium in it.

O'BRIEN

In the meantime, they are storing the tainted water in tanks. Lots of tanks. They have to finish construction of a new one about every other day to keep up. A plateau above the destroyed reactors now brims with more than 1,000 of them. They hold more than 264 million gallons of water. While TEPCO has enough space to keep building them for years, it is clearly not a sustainable solution, and yet the government has refused to issue a permit that would allow the utility to start draining the tanks. To get there, they're going to have to rebuild the public confidence that they understand and trust the people that are telling them these messages. And ultimately that people realize you can't just keep building tanks forever-- there has to be a limit. Meanwhile, TEPCO is desperately trying to reduce the amount of groundwater that becomes contaminated in the first place. They have encircled the damaged reactors with 1,500 pipes that go 100 feet deep. They are filled with coolant that is 22 degrees below zero, creating a mile-long underground barrier of frozen soil. The hope is it will deflect the groundwater away from the melted fuel. But why ice? (translated): When my boss told me that I was being assigned here, I had my doubts. But there are a large number of buried pipes and cables around the nuclear reactor buildings. So it's not possible to use a continuous wall of steel or concrete underground. The technique is routinely used on construction sites to temporarily stabilize the ground. But nothing at this scale, designed to work for years, has ever been tried before.

DALE KLEIN

My concern is, if you have water flowing through the site and you build a barricade, does TEPCO really understand where that water goes? Is it going to go over the wall, is it going to go under the wall, is it going to go around the wall? (speaking Japanese)

O'BRIEN

In March of 2016, they turned it on, but the groundwater is still seeping in. No one knows if it will ever work. The engineers here face huge challenges ahead. The job won't be finished for 30 or 40 years.

BARRETT

Nothing of this magnitude has ever been done before. It can be done, I believe, with the technologies that exist and will be developed as we go forward. But no, nothing of this magnitude has ever been done by mankind.

O'BRIEN

They are being watched by a scared, skeptical populace. And unfortunately, scientists can offer little reassurance. Biophysicist David Brenner is Director of the Center for Radiological Research here at Columbia University Medical Center. In my opinion, everybody who lived in Fukushima prefecture and even outside who got some very low level of radiation exposure, and that's pretty well everybody, would be subject to a very small increase in cancer risk. But beyond that, scientists cannot say anything conclusive about their long-term risk of developing cancer or genetic defects.

BRENNER

The individuals in Fukushima prefecture want to know, "what are the real effects of the radiation that I was exposed to?" And we can't give them the answers that they need, and that's a really unfortunate situation. I personally find it a very frustrating situation.

O'BRIEN

About 18,000 people died as a result of the earthquake and tsunami on March 11, 2011. But no one has died by radiation from the meltdowns. So, is the lesson of Fukushima to stop, or to build better, safer nuclear plants? Plants that employ a host of new technologies that matured long after most of our current fleet of nukes was designed?

MYHRVOLD

I think the right interpretation of the accident at Fukushima is we should go all out on nuclear innovation. If the Japanese had replaced these elderly plants with modern plants, Fukushima wouldn't have happened.

O'BRIEN

The first reactors at Fukushima Daiichi were designed and built when this technology was still young.

MYHRVOLD

The Fukushima plant designed in the 1960s was literally a slide-rule-era plant. you know, there's a few calculations in that era they could have done on a mainframe, but that mainframe has less power than... certainly than you do in your cell phone.

O'BRIEN

The design that failed at Fukushima is an early model boiling water reactor. There are currently 32 reactors of this vintage still running in the world. In all there are about 450 nuclear reactors generating 11% of the planet's electricity. In the U.S., nuclear power fills about 20% of the nation's power demand. The vast majority of nuclear power plants were built with technology and techniques from the '60s and '70s and are water-cooled. Despite steady improvements over the years, water-cooled reactors still have a serious vulnerability... a station blackout that stops the crucial pumps that keep cooling water flowing. This is what happened at Fukushima. To make fission robust enough to generate power, uranium is enriched, shaped into pellets, and then stacked into fuel rods. This ensures lots of uranium atoms are close enough to each other to allow a healthy chain reaction. To manage the rate of the reaction, control rods that absorb neutrons are moved in and out of spaces among the fuel. During an emergency shutdown, or SCRAM, the control rods are pushed all the way in, terminating the chain reaction. The earthquake of March 11, 2011, prompted an automatic SCRAM at Fukushima. But it also brought down the crucial transmission lines that connected the plant to the power grid. Then the tsunami waves wiped out the emergency backups, the generators and batteries designed to keep electric pumps pushing water over the reactor cores while they cooled down.

JOSE REYES

Currently, the existing fleet of reactors use pumps and diesel generators and AC and DC power to provide the cooling to the nuclear reactor core. If you lose connection to the grid, essentially you have no way of cooling that core.

O'BRIEN

Jose Reyes is a nuclear engineer at Oregon State University. In the early 2000s, he and his team partnered with Westinghouse Toshiba to design the prototype for a new generation water-cooled nuclear reactor called the AP1000. It has an emergency water reservoir above the reactor. It is designed to prevent a meltdown for as long as 72 hours, using gravity and convection, but no electricity. If the reactors at Fukushima could have coped for that long, the meltdowns would not have happened. Four of these AP1000s are now under construction in Georgia and South Carolina, and four more in China. So what you're looking at here is the reactor vessel in the center... But more recently, Reyes is focused on smaller and, he thinks, better things. He is the cofounder and chief technology officer for an Oregon-based company called NuScale.

REYES

In our design, the reactor vessel sits inside the containment, and then that whole system, the containment and the reactor vessel, sits underwater underground. And that's the whole safety system for this plant.

O'BRIEN

NuScale reactors are small and modular-- designed to be operated in clusters, completely submerged in a four-million-gallon pool of water. Each can generate about 50 megawatts of electricity, enough to power nearly 40,000 homes. So 12 of them linked together could service 450,000 homes, or about as much as a conventional nuclear power plant.

REYES

As we've gone through the patent process, some of the patent examiners have said, "This is too simple. How is this possible that this hasn't been done before?"

O'BRIEN

Unlike Fukushima, where critical coolant pumps had to keep running for the reactors to cool down, NuScale has designed a plant that requires no pumps and no electricity at all.

MAN

So a lot of these are tied to actual valves. Okay.

O'BRIEN

Right now, they are still trying to validate the concept and clear the massive regulatory hurdles. It will take many years, but NuScale already has a customer, the Utah Associated Municipal Power Systems. The plant will actually be built across the state line in Idaho, at the federal government's premier nuclear power test site, a storied place emerging from a long nuclear winter.

TILL

When I came to Argonne in 1963, I was then 28, 29 years old. The world was my oyster.

O'BRIEN

When Chuck Till first came to the Argonne National Laboratory, it was a great time to be a nuclear physicist, a golden era.

CHARLES TILL

A lot of things had been discovered, but very many had not. The things that would be necessary for civilian nuclear power to be a success basically had not been explored. And at Argonne you were right in the center of it.

O'BRIEN

Argonne's vast testing site in the Idaho desert is ground zero for nuclear power generation. More than 50 novel reactor designs have been built and tested here since 1949. It is hallowed ground for nuclear engineers.

TILL

The beginnings of nuclear power were here. The beginnings of useful nuclear power were here.

At 1

50 p.m. on December 20, 1951, four 200-watt light bulbs started burning here with electricity generated by the Experimental Breeder Reactor number 1, the first-ever nuclear power plant. Besides the fact that it proved splitting atoms could generate power, it also demonstrated a very clever way to do it. The fuel was cooled with liquid metal-- sodium mixed with potassium, which has a low melting point. It absorbs more heat and has a much higher boiling point than water. It meant the reactor did not need to be encased in a thick steel pressure vessel designed to keep water in liquid form like a pressure cooker. It was inherently safer, or so the scientists hoped.

They built this reactor to test the concept

Experimental Breeder Reactor Number Two.

TILL

The Experimental Breeder Reactor Number Two is a reactor that's known to all nuclear programs around the world. It is a full-scale plant and it proved all kinds of firsts in nuclear power. It's now about five minutes till test time.

O'BRIEN

It made history on April 3, 1986.

MAN

One minute until the test.

O'BRIEN

When they staged a bold demonstration of how a liquid metal reactor can handle multiple failures.

MAN

Three, two, one, start. (alarm rings)

TILL

In the turbine hall was an assemblage of people that came from all over the world. They had nuclear programs and they wanted to see this because the reactors don't behave this way. Reactors can't be relied upon to shut themselves down.

O'BRIEN

The first demonstration foreshadowed Fukushima-- a station blackout and a loss of coolant flow to the hot nuclear core. Mark!

TILL

They just shut off the coolant supply. And, I mean, to do that in a normal reactor, you'd have an explosion. You could see the power going straight up. (beeping) The next thing, of course, was everybody's head swiveled back to where we were, the Argonne people were, wondering, "Are they running?" (laughs)

O'BRIEN

The demonstration went as hoped. The power trace went up like that, came down well below where it had to come down, and the reactor just quietly shut itself down. Deprived of any cooling, this reactor did not melt down or explode. But how? Remember, to sustain a healthy chain reaction, uranium atoms must be close enough to each other so the neutron bullets can hit their targets. When the liquid sodium coolant pumps stop, the temperature initially rises, expanding the reactor core, dispersing the uranium atoms. As a result, the chain reaction is reduced, causing the temperature to go down. So the laws of physics and the robust cooling capacity of liquid sodium metal bring it automatically to a safe shutdown. At the time of that dramatic test, Chuck Till thought this was the dawn of a new era. He envisioned widespread commercial use of sodium reactors based on this design.

TILL

Absolutely. The world was going to need massive amounts of energy and here was the way. There was no doubt. Sodium-cooled reactors, properly designed, are safer. I say that without question.

O'BRIEN

So why don't we have them? We were stopped.

REPORTER

There has been a nuclear accident at the Chernobyl atomic power plant.

O'BRIEN

A few weeks after that demonstration, a reactor at the Chernobyl nuclear power plant in the Soviet Union blew up during an ill-conceived test. Chuck Till's success was totally eclipsed. This is a model of the Navy's first nuclear-powered submarine, the Nautilus. But the seeds of the demise for sodium reactors were planted many years earlier by this man, Admiral Hyman Rickover, the father of the nuclear navy. This is the reactor, or the atomic pile. There is uranium in here. He selected nuclear reactors cooled with water to propel the Nautilus, the first nuclear-powered submarine. (klaxon blaring) The design made a lot of good sense for the Navy. It was the right mix of size, simplicity, and safety. Among other things, sodium explodes when exposed to water. The huge Pentagon investment in the research and development of this technology gave it a big leg up on other ideas, including liquid metal reactors. (applause) About the same time, President Eisenhower delivered his famous "atoms for peace" speech at the UN. So my country's purpose is to help us move out of the dark chamber of horrors into the light. He hoped to change the way the world thought about splitting atoms, from bombs to light bulbs. He wanted to export U.S. nuclear power technology, and he was in a hurry to beat the Soviets. Adapting the nuclear navy technology for use on land offered the fastest path to market. In 1957, the first commercial atomic power plant in the U.S. opened near Pittsburgh, in Shippingport, Pennsylvania. Admiral Rickover personally oversaw the design and construction. Very quickly, reactors cooled with water became the norm. For 20 years, utilities went on a nuclear building binge. But then in the 1970s, environmentalists took aim at nuclear power. The fear of radiation and the inextricable link to atomic weapons and their proliferation changed the equation. Protesters viewed nuclear power as inherently unsafe, too complex and costly. And, indeed, as the safety regulations increased, so did the cost of building the plants. The Achilles' heel of nuclear power is that you can't protect against every conceivable accident. You can put a lot of extra safeguards into place and really lower that uncertainty as much as you can, but that will raise the cost of nuclear power when it's already unaffordable. By the mid-'70s, the atomic energy party was winding down. And then came the movie. This is Jack Goddell. We have a serious condition. You get everybody into safety areas and make sure that they stay there. The China Syndrome premiered on March 16, 1979. It is the story of an evil corporation cutting corners, leading to a nuclear meltdown.

MAN

The number of people killed will depend on which way the wind is blowing, render an area the size of Pennsylvania permanently uninhabitable, not to mention the cancer that would show up later.

O'BRIEN

Twelve days later, in Pennsylvania, life seemed to imitate art at Three Mile Island, the seriousness of the meltdown there unwittingly embellished by Hollywood. Support for nuclear power evaporated. Still, in the Idaho desert, Chuck Till's EBR-2 kept going, running safely for 30 years. Mr. Speaker, the President of the United States! (applause) But it was better at sustaining fission than political and popular support. The program was canceled by President Clinton in 1994. We are eliminating programs that are no longer needed, such as nuclear power research and development.

TILL

The whole system, when it was shut down, was pristine, 30 years of operation. What a very unfortunate scene.

O'BRIEN

But now, more than 20 years later, the intensive search for carbon-free power is prompting a fresh look at new nuclear technology. In the face of climate change reality, the money is starting to flow in this direction again. The federal government has placed some new bets on nuclear innovation. In Idaho, they are taking some of the old test reactors out of mothballs.

MARK PETERS

The fact that we're restarting that tells us that we're restarting a testing infrastructure to start to develop the next generation of nuclear power.

O'BRIEN

Argonne's test site is now called the Idaho National Laboratory. Its director, Mark Peters, oversees several partnerships with the private sector to improve technology, the state-of-the-art in water cooled reactors known as generation three. But the main goal is to commercialize generation four.

PETERS

Generation four are future reactors that are based on different concepts, different core designs, different coolants. I'm quite excited about where we're at today.

O'BRIEN

And so is his predecessor, Chuck Till.

TILL

It surprises me when I go on the internet and see how many allusions there are to the things that we did. And I hope that the work that my colleagues have done in that decade from 1984 to 1994 pays off. The nation has fumbled around, in my view, for 20 years unnecessarily.

O'BRIEN

But now Chuck Till's vision may finally be gaining some critical mass. (applause) I'm going to talk today about energy and climate. This time one of the drivers for nuclear power technology is not an admiral, but rather a captain... of industry. And so what we're going to have to do at a global scale is create a new system. Microsoft founder Bill Gates is among a handful of entrepreneurs with seemingly bottomless pockets making big bets on nuclear power. At a TED conference in 2010, he publicly announced he had co-founded a company called TerraPower. Nathan Myhrvold and I actually are backing a company that perhaps surprisingly is actually taking the nuclear approach. His partner is his former chief technology officer at Microsoft, Nathan Myhrvold. When we first started investing in TerraPower and getting it going, we had a lot of people come and look at us, kick the tires. That was the era when Silicon Valley was into clean tech. And they all said, "Oh, my God, this is risky." But Bill and I thought that it being risky doesn't mean you shouldn't do it. (chuckles) In fact, perversely, that's exactly when you should do it. It's when everybody else says, "No, I can't... I can't do it." It's something that is a risk that's not for the faint of heart. Here they are working on a 21st-century take on sodium reactors. It is designed to run without reprocessing and refueling.

MYHRVOLD

With the TerraPower reactor, you fuel it and you don't take them out for 60 years. During that period of time, you'll get enormously more energy out than you would get from the same uranium if you put it in a conventional plant.

O'BRIEN

Unlike water-cooled reactors, this one does not need the equivalent of premium gas-- uranium that is refined to greater potency in a complex, expensive process called enrichment. But the enrichment process has leftovers. The biggest stockpile in the U.S. is here in Paducah, Kentucky, at a uranium enrichment plant. These leftovers, called depleted uranium, can be used to fuel the TerraPower reactor. If this works, it would be a game changer for nuclear power, in part because it would virtually eliminate the need to store depleted nuclear fuel, one huge unresolved problem.

MYHRVOLD

With our reactors, Paducah, Kentucky, becomes the energy capital of the United States, because Paducah alone has enough of this low-level nuclear waste, the depleted uranium, that we could run all of America's electricity needs for 750 years.

O'BRIEN

But TerraPower faces big regulatory hurdles. The Nuclear Regulatory Commission is accustomed to licensing water-cooled reactors. When it comes to innovative technology like this, the rules haven't even been written. So TerraPower has found a customer that is less constrained by regulation

and public relations

China. It's where its first plant will be built.

MYHRVOLD

So far, from a technical perspective, we've solved every technical problem that's occurred. But I can't tell you, "Oh yes, we've already been successful." It's going to be many more years of hard work before we are successful. And stop. So we made a crazy bet and we're going to keep making that crazy bet. And I'd love to have more competition. I'd love to say, "You know, we're neck and neck with three other companies," because that's what moves things forward.

O'BRIEN

It appears Nathan Myhrvold will get his wish. A D.C.-based think tank, Third Way, conducted a survey in 2015 and found more than 40 startups across the U.S. developing advanced nuclear power designs. These atomic business plans have lured more than a billion dollars in investment. I think a lot of it might just be the changing demographics of nuclear engineers that now there are a large number of young nuclear engineers who think, "I have a really good idea. "I'm going to flesh out this technology. "I'm going to raise some funding. I'm going to see if I can do this on my own." How much do you have to worry about free fluorine formation? Leslie Dewan is one of the young entrepreneurs leading this revolution. Yeah, because that's what I'm hoping. It's a new generation with a different outlook. Atomic power doesn't carry the same stigma for them. They are more concerned about powering the planet while addressing climate change. All of this led Leslie to MIT to study nuclear engineering. This is a general trend around the world. She was a grad student on the day the tsunami hit Fukushima.

DEWAN

It was especially shocking to me because when I first heard the news, I thought there are overblown media reports but I trust that everything will be okay. But it went orders of magnitude beyond what I had thought the worst-case-scenario accident was going to be.

O'BRIEN

And yet she didn't waver in her goal to build a new kind of nuclear power plant.

DEWAN

It made me want to work even harder on developing newer types of reactors that don't have the same cooling requirements and that are even more robust in the case of even more extreme accident scenarios.

O'BRIEN

She became enamored with some nuclear technology first developed 50 years ago at another national laboratory, this one in Oak Ridge, Tennessee. It's called a molten salt reactor. Not table salt, liquid fluoride salts. Unlike the TerraPower reactor that uses liquid metal to cool solid uranium fuel, this inventive design turns that idea around.

DEWAN

A molten salt reactor uses liquid fuel rather than solid fuel.

O'BRIEN

With liquid fuel, the size and shape of the container is crucial. Pumping the fuel into a cylindrical vessel places uranium atoms close enough to each other to sustain a nuclear chain reaction. If something goes wrong and it starts to overheat, the liquid expands and the uranium atoms become too dispersed to maintain fission. So it starts cooling down passively. And in the case of a total loss of station power, like Fukushima, the design employs another safety feature. Below the reactor chamber is an emergency reservoir. The drain leading to the reservoir is plugged by the same salt mixture, but it is refrigerated so that it freezes solid. Without electricity to keep it cool, the plug quickly melts, and the liquid fuel drains into the emergency reservoir. Unlike the reactor chamber, the shape and size of the emergency reservoir ensures the uranium atoms are too far apart to sustain a chain reaction. It cools down and eventually freezes. Crisis averted. At Oak Ridge, they successfully ran and tested a molten salt reactor for four years. The design works.

DEWAN

Even in the worst type of accident scenario, even if you don't have any external electric power like what happened at Fukushima, even if you don't have any operators on site, they're able to shut themselves down.

O'BRIEN

The basic science is well understood, but building a reactor that can withstand something as corrosive as a very hot bath of salt is a huge engineering challenge. It is the focus of early testing for Leslie's startup company, Transatomic.

DEWAN

We can make something that works for five years, that works for ten years. Like, that we certainly know. What we are trying to figure out now is whether we can use newer materials or new methods of corrosion control to extend the lifetime of the facility because ultimately we care about making this low cost. If you have to replace your key components every ten years, it's not going to be cheaper than coal. And if it's not cheaper than coal, then it's not worth doing.

O'BRIEN

But coal and all fossil fuels carry another cost to the environment. In Japan, with the nukes mothballed, they have kept the lights burning by burning imported fossil fuels, mostly liquid natural gas.

The result

a steady increase in greenhouse gas emissions, reversing the nation's ambitious reduction plan signed just two years before the Fukushima disaster.

DEWAN

If you're concerned about climate change, you need to be open to nuclear power. I think that there is no way that the world will meet its carbon reduction goals without including nuclear in the mix.

O'BRIEN

All over the world, the demand for energy grows, exponentially in emerging economies. China opens a new coal-fired power plant about once a week. Can the world respond to the relentless demand for energy without worsening climate change? Is it time to rethink the nuclear option? The fate of the whole planet depends on us renewing our energy system with renewables and with nuclear. And if we step back from that, we are going to create a tremendous problem for future generations. This NOVA program is available on DVD. To order, visit shopPBS.org, or cal1-800-play-PBS. NOVA is also available for download on iTunes.