Hitler's Sunken Secret

PBS Airdate: November 8, 2005
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NARRATOR: In 1938, the Third Reich is in ferment, as Hitler prepares to plunge Europe into war. Within months, the German army will begin a top secret research program to develop nuclear weapons. It is based on experiments performed in Berlin that showed, for the first time, that the atom can be split, unleashing immense power. German scientists were the first to start work on the atom bomb, but they would never finish the job. Just why has always been a mystery.

In search of clues to solve this mystery, a team of underwater archaeologists has come to this lake in Norway. They're looking for the cargo that was on board this sunken ferry.

BRETT PHANEUF (ProMare): Look at that.

FREDRIK SOREIDE (ProMare): There's something there, isn't it?

NARRATOR: Is the key to the Nazi nuclear bomb about to emerge from the icy depths of a Norwegian lake? Hitler's Sunken Secret, right now on NOVA.

Google is proud to support NOVA in the search for knowledge: Google.

Major funding for NOVA is provided by the Howard Hughes Medical Institute, serving society through biomedical research and science education: HHMI.

And by the Corporation for Public Broadcasting, and by contributions to your PBS station from viewers like you. Thank you.

NARRATOR: For 60 years the icy waters of Norway's Lake Tinn have held a secret. Today, its peaceful shores show little sign of the conflict that raged here in World War II, but under Nazi occupation, this region witnessed a deadly underground war of spies and saboteurs. The battle was for one thing above all: a mysterious substance called heavy water that the Norwegian resistance fought desperately to keep out of German hands.

In 1944, in a daring act of sabotage, a passenger ferry carrying several barrels of heavy water was sent to the bottom of Lake Tinn. Now a team of underwater archaeologists is looking for those barrels. They want to know what's really inside them, because they may contain the key to the only weapon that could have won the war for Hitler, a Nazi nuclear bomb.

The story begins on April 9th, 1940, when Nazi Germany invaded the small neutral country of Norway. Taken by surprise and betrayed by Nazi sympathizers in their own government, the Norwegians could offer little resistance. As opposition crumbled, the Germans headed straight for the remote area around Lake Tinn, to take control of Norway's most valuable industrial enterprise. High in the mountains, at the head of the Rjukan valley, was the Vemork hydroelectric plant, once the world's largest power station.

The Norsk Hydro company used that power to make ammonia, the basis of fertilizer and explosives, both vital to the German war effort. But inside the Norsk Hydro plant was a room of specialized equipment that made something even more valuable.

PER F. DAHL (Physicist, Lawrence Berkeley National Laboratory, Retired): What have we here then? Well, look here, the original stuff, the high concentration cells.

NARRATOR: Physicist and historian, Per Dahl, is an expert on what happened here during World War II.

PER F. DAHL: We're really looking here at a piece of history, the original high concentration cells for producing heavy water.

NARRATOR: Heavy water was a strange new form of water that had only recently been discovered, and Norsk Hydro was making small quantities to supply scientists around the world who were investigating its properties. As soon as they took over the plant, the Germans set about increasing production.

PER F. DAHL: They doubled the production apparatus, expanding the high concentration cells from the initial nine to 18, doubling the production. By 1942, they were seeking a tenfold increase in the production of heavy water. At the same time, the security 'round the plant in Rjukan was drastically heightened as well.

NARRATOR: Nobody could understand why. But every move the Germans made was being watched, both inside the factory and out.

KNUT LIER HANSEN (Hydro Saboteur): A group of us, particularly the organized labor at the factory, wanted to create a movement to fight the Germans underground.

NARRATOR: Knut Lier Hansen became a key member of this secret resistance, determined to figure out the German obsession with heavy water.

KNUT LIER HANSEN: The heavy water, we had no idea at all what it really was and why the Germans paid so much attention to it; it had to be something important.

NARRATOR: The resistance communicated its concern to British intelligence in London.

KNUT LIER HANSEN: The home forces had established a radio station, so there was a steady stream of messages sent to England by radio.

NARRATOR: To the British, the developments at Vemork were deeply alarming. They knew something the Norwegians didn't: heavy water could be used to make nuclear explosives. It looked as if German scientists were trying to build an atomic bomb.

PER F. DAHL: If I were a physicist in London and realized what was going on in Norway with the heavy water business, I would have been mighty worried.

NARRATOR: So began two years of secret warfare to thwart the manufacture of heavy water. Norwegian commandos blew up the plant, but the Germans had it working again within three months. Then the U.S. Eighth Air Force bombed Vemork, but the heavy water plant survived unscathed.

Eventually, in 1944, members of the resistance learned that the entire production plant and 15 tons of partially purified heavy water were to be shipped to Germany. They passed the information on to London asking what they were to do.

The reply was swift: "Stop the heavy water reaching Germany."

But how? With only days to plan, it fell to Knut and his group to find a way. The plant was closely guarded, but on its journey to Berlin, the heavy water would be transported in barrels down the Rjukan Valley by train; it would then travel the length of Lake Tinn by ferry.

KNUT LIER HANSEN: I personally thought that the only place that they would never be able to recover the barrels from would be the bottom of Lake Tinn.

NARRATOR: But the saboteurs knew that sinking the ferry would almost certainly mean the death of friends and neighbors. Could a few barrels of water really be that important? They sent a message to London.

NORWEGIAN SABOTEUR (Dramatization): Doubt whether the effect of the operation is worth the reprisals which must be reckoned on. Stop. As we cannot decide how important the operation is, we request a reply soonest—if possible, this evening.

NARRATOR: London replied immediately.

LONDON UNDERGROUND (Dramatization): The matter has been considered, and it is decided that it is very important to destroy the heavy water. Stop. Hope it can be done without too great misfortune. Stop. We send our best wishes for success in the work.

KNUT LIER HANSEN: A message came back that this plan should be carried out, the heavy water destroyed once and for all, unambiguously put, regardless of the loss of life. So we started the operation.

NARRATOR: In a 1947 Norwegian film, Knut and his colleagues reenacted their daring mission.

KNUT LIER HANSEN: We studied drawings of the ferry. At the bottom was a hatchway leading to the bilges. We unscrewed the floor cover to place a time bomb at the bottom of the ferry.

NARRATOR: While his colleagues planted the bomb, Knut stood guard. Suddenly, they were spotted.

KNUT LIER HANSEN: There was a guard who asked us what we were doing there. I told him a lie and wondered whether I'd have to kill him. But he felt sorry for us and said he would turn a blind eye and let us go, as long as we didn't tell anyone. He was going off duty at 6:00, and so the guard on the next shift went down with the ferry.

NARRATOR: The next morning, the railway flat cars with their cargo of barrels rolled on board the ferry. Meanwhile, in the hold, the improvised time bomb still ticked away. The Hydro was due to sail at 9:30, but at 10:00 it had still not left the dock.

The ferry's delay meant that Halvard Asskildt and his fiancée Solveig Holgen just got there in time.

HALVARD ASSKILDT (Hydro Survivor): We were late—we were celebrating my birthday—so we had to run the last bit to get to the ferry on time.

NARRATOR: Finally, the ferry left the dock.

HALVARD ASSKILDT: We had cake and food from my parents, and we were sitting downstairs in the saloon. Suddenly, there was a bang; the boat was shaking. We thought we'd hit something.

NARRATOR: The ferry was rapidly filling with smoke and water. Halvard was faced with a terrible dilemma: his fiancée couldn't swim.

HALVARD ASSKILDT: Solveig wanted me to jump. She knew she couldn't swim, but I told her she would have to jump. She said, "Okay, you first, and I'll follow."

I jumped, but she just stayed there and went down with the boat. It's hard for me to talk about this. She was very young and beautiful.

NARRATOR: Fourteen local people drowned in the icy waters of Lake Tinn. But in all other respects, the mission seemed to be a success. The ferry and its cargo sank just where the saboteurs had planned, in the deepest part of the lake, where the Germans could never recover the barrels.

KNUT LIER HANSEN: I was so elated. I'd never run so fast, so that we could get a message to England. It was as if I had angel's wings; that's how fast I ran, just to inform them that the operation had been successful. And the congratulatory telegrams started coming in.

NARRATOR: But mixed with the congratulations was concern. Something about the operation didn't seem quite right.

KNUT LIER HANSEN: The Germans did not seem to feel that there was any reason to protect the shipment. They just sent it on its way. And the Chief Engineer at Vemork had also not heard anything about a German guard for this transport.

NARRATOR: London was suspicious. Had it all been too easy?

LONDON UNDERGROUND (Dramatization): With regard to the ferry, please make absolutely sure that the barrels on it were not dummy ones substituted by the Germans. Stop.

NARRATOR: Did the Germans fool the Norwegian resistance? After the war, it became clear that some barrels containing heavy water had indeed made it to Berlin. What was in those barrels that went down with the Hydro? And what was the real significance to the Germans of the heavy water from Vemork? This is one of the last great mysteries of World War II, and there's only one way to solve it.

To investigate, marine archaeologist Brett Phaneuf has assembled a team to dive to the wreck of the Hydro and bring back an intact barrel from its secret cargo.

BRETT PHANEUF: I'm fascinated by World War II, and mostly what I'm fascinated by is that it's within living memory, and yet there's so many discrepancies. And in this case, there are some really glaring inconsistencies in what really was on the Hydro. Where was it really headed? Why was it so easy to scuttle? All these things that don't add up. So, we want to find out: is it really heavy water? And if it is, was it all of the heavy water? Or is there some heavy water that went somewhere else? And the only way to do that is to go back and look.

NARRATOR: But it won't be easy. Five tons of special equipment are needed to penetrate one of the world's deepest lakes, so Brett has recruited a Norwegian team with experience in these waters.

BRETT PHANEUF: There's Jonny, who is just a boundless ball of energy. You can't contain him, always optimistic, so he's been really excited about telling the whole story for Norway.

JONNY SKOGSTAD : It was touching, you know, a very big part of the history, and suddenly me and Thor Olav, small locals, you know, found out that this is the starting of the race for nuclear weapon.

BRETT PHANEUF: And then we've got Thor who's a typical stoic sort of Norwegian, you know, obviously in charge when you see him out on the lake. And then there's Fredrik, who's my partner in crime. We think up the crazy missions together, then figure out how to get it all to the field so we can tell these stories.

BRETT PHANEUF: But what was its condition?

FREDRIK SOREIDE: That was very good condition.

BRETT PHANEUF: Was it good?



NARRATOR: Perhaps the most important piece of equipment is the team's R.O.V., or remotely operated vehicle.

FREDRIK SOREIDE: All right, this is the R.O.V. that we are going to use to look at the ferry. And we have a number of thrusters on it that pushes it forward and up and down in the water. Actually, anybody that plays Nintendo or Playstation could do it.

It's got a very good lighting system on it and a very good camera. We also have a sonar in the front which helps us navigate and tells where everything is on the seafloor.

NARRATOR: From eyewitness reports of the sinking, they have a good idea of where to start looking for the Hydro. Thor prepares to dive. It will take about 20 minutes for the R.O.V. to descend to the bottom of Lake Tinn.

BRETT PHANEUF: You can see how steep the mountains are, and basically it just continues like that underwater. So we're 300 meters from shore, but it's 400 meters deep. So it's more than a 45-degree slope to depth.

NARRATOR: A cloud of sediment signals the R.O.V.'s safe arrival at the bottom of the lake.


NARRATOR: They begin searching the lakebed. Suddenly, the sonar starts to pick up the shape of a hull.

FREDRIK SOREIDE: This is the sonar image of the shipwreck, so it shows us we are about 25 meters away from the ship. So it should come into view on the video screens in a few seconds, actually. So we're closing in, as you can see.

There we go.

BRETT PHANEUF: Oh look at that. It's beautiful. It's a big ship.

Can you still read the name? Can you see text?


BRETT PHANEUF: It looks fantastic. It's in great shape.

So, where are we? Right at the bridge there?


BRETT PHANEUF: It's so strange to see a wreck in a lake as opposed to the ocean. It's just completely clean. In the ocean, you know, you get so much fuzz on the wreck, and there's just nothing on this at all.

FREDRIK SOREIDE: See the lantern there?


THOR OLAV SPERRE: It's nice...60 years...I think it's still working if you pick it up.

NARRATOR: The ferry is in remarkable condition, but so far there's no sign of its cargo, the barrels that supposedly held heavy water. If the team does manage to find and salvage one intact, they'll need to analyze its contents, so Brett has asked physicist Dave Wark, an expert in the nuclear properties of heavy water, to join them in Norway.

DAVE WARK (Imperial College London): Well, of course I've known what happened here during the war for many years; the contents of those barrels had a major impact on the course of history. And I'm just fascinated to see what we find when we finally get one up.

NARRATOR: Before the outbreak of war, the manufacture of heavy water was just a sideline for Norsk Hydro. It came about because, to make chemical fertilizer, the company needed hydrogen, and hydrogen could be made from water.

DAVE WARK: Norsk Hydro were using hydroelectricity to make hydrogen. It's actually not a very hard thing to do. If you pass electricity through water, which is H2O, you can break it apart into hydrogen and oxygen.

So, as you can see, we are collecting hydrogen here in this test tube, which is basically all that Norsk Hydro were doing, just on a vastly larger scale. And then they'd take the hydrogen and use it to make fertilizer.

NARRATOR: But a few years before the war, scientists made an extraordinary discovery, a new kind of hydrogen, in which the nucleus contained an extra neutron, making it heavier. They called it deuterium. Just like normal hydrogen, deuterium combined with oxygen to make a new kind of water, heavy water.

DAVE WARK: We call it heavy water for a very simple reason. I've got some heavy water here that we've frozen into heavy ice, and if I just drop it into this glass of ordinary water, you can see it sinks straight to the bottom.

Now, heavy water is actually present in ordinary water. It's about 0.01 percent, or, in other words, in this five liters of ordinary water, there's about that much heavy water.

And one of the side effects of the process of breaking up water into oxygen and hydrogen is the heavy water is very slightly harder to break up than, than the light water, and so you end up with the water that's left behind having a slightly higher concentration of heavy water. And if you do this again and again and again and again and again and again and again, you can eventually end up with this, which is essentially pure heavy water. This is from Norsk Hydro. It's 99.76 percent pure heavy water.

NARRATOR: It was for this seemingly harmless substance that Norwegian resistance sank the Hydro.

BRETT PHANEUF: That's not a barrel, is it? What is that?

THOR OLAV SPERRE: It's a pipe.

BRETT PHANEUF: Oh, a stack. Okay.

NARRATOR: As Thor maneuvers the R.O.V. around the wreck of the Hydro, the team can begin to piece together the last desperate moments of the civilian passengers.

FREDRIK SOREIDE: This is the first class section.

BRETT PHANEUF: All right. Okay, it's got four windows, just like on we're here, then. We're on the starboard side of the wreck.



FREDRIK SOREIDE: The ceilings have been...

BRETT PHANEUF: Oh, the ceiling's gone.

THOR OLAV SPERRE: You can see the doors where the people was fighting to get out.

BRETT PHANEUF: Oh, we're right at the...

THOR OLAV SPERRE: It's the bow.

BRETT PHANEUF: Oh, it's the bow. Oh, it's going down into the sediment. Look at that. So the whole forward part of the ship sort of disappears. It's amazing.

NARRATOR: After the explosion, the ferry sank bow first, and the saloon where Halvard Asskildt and his fiancée were sitting is now buried in the lakebed.

In the confusion, Halvard had left his fiancée for dead. But miraculously, Solveig survived and witnessed what happened to some of the cargo.

SOLVEIG ASSKILDT (Hydro Survivor): I was probably dragged under by the undertow from the boat, and I somehow ended up getting caught in the propeller. I was badly cut and bruised. And the second time I emerged, I managed to grab hold of the lifebuoy crate.

I couldn't see a lot, but I did see a barrel next to me, although I have no idea what was in it. A man was trying to get up onto it, but he didn't manage, and he drowned.

NARRATOR: Eventually Solveig was picked up by a fishing boat and taken to the same farm as her fiancé Halvard.

HALVARD ASSKILDT: Hard to describe such a moment. It's not really possible.

NARRATOR: Solveig's account confirms that barrels were indeed aboard the Hydro. But where are they now? And if they floated, they couldn't have been full of heavy water.

BRETT PHANEUF: Are we very close to the stern now? Or is that a rail car there? Is that...oh, that's one of the flat cars, okay. Boy, that thing is absolutely mangled, though. All the wood's gone on it. Or is that the underside we're looking at? I see. Okay, so it's flipped over.

We've just seen one of the rail cars sort of flipped upside down, sort of mangled up a little bit.

NARRATOR: The flat cars should have been loaded with the barrels, but everything has been badly crushed. Then the team gets its first glimpse of the cargo.

THOR OLAV SPERRE: Here are some barrel, crushed barrel. Here.

NARRATOR: The barrel has been broken open. No one will ever know what it originally contained.

But then, a little further on, the R.O.V. reveals more barrels.

FREDRIK SOREIDE: Two barrels lying on the seafloor.

BRETT PHANEUF: Look at that. Oh, that one's wedged under. I wonder how many others got under the wreck when it sank. They don't look in bad shape.

FREDRIK SOREIDE: Yeah, they seem to be in good shape.

NARRATOR: The wreck of the Hydro is a Norwegian war grave. Thor decides that these barrels are too close, and decides to back away.

THOR OLAV SPERRE: This is a very special feeling, because when you know that it's a lot of people who drowned and the history around it, it's very... yeah, so you have some feelings, yes.

NARRATOR: Encouraged by finding barrels which seem to have survived the sabotage, the team starts to search the area around the wreck, hoping to find another intact barrel which might still contain heavy water.

But why were the Germans and Allies so obsessed with this substance? The answer lies in a discovery based on experiments done in Germany on the eve of the war, a discovery which would have momentous consequences.

DAVE WARK: The story of nuclear energy really starts in 1938, in Berlin, when German physicists found that if you have a uranium nucleus and you hit it with a neutron, you can split it apart, or fission it, into two smaller nuclei, releasing quite a bit of energy.

Now, the key point is, in addition to energy, it also releases more neutrons, which can fission more uranium, releasing more neutrons, fissioning more uranium, causing a chain reaction which, in principle, can release vast amounts of energy.

Now, this opened up the very worrying possibility—which was clear to physicists right away—of making nuclear explosives of tremendous power.

NARRATOR: Hitler's armies were already on the march through Europe. Physicists worldwide suddenly realized there would be a race to develop nuclear weapons. If Germany won it, nothing could stop the Nazis.

Professor Mark Walker is an expert in German wartime nuclear research.

MARK WALKER (Union College): Certainly was reason for the Allies to have fear about a German nuclear weapons project. Although many excellent scientists fled Hitler's Germany in 1933, Germany still had very good physicists. Among the best was a theoretical physicist, Werner Heisenberg. He'd helped create quantum mechanics in the 1920s, won a Nobel Prize for it. Heisenberg was obviously a brilliant scientist, and if nuclear weapons were possible, then he was good enough to get the job done, to actually help Germany make a nuclear weapon.

NARRATOR: With the stage set for World War II, the German military was the first to begin a secret nuclear research program. Recruited along with Heisenberg was his brilliant young protégé Carl Friedrich von Weizsäcker.

CARL FRIEDRICH VON WEIZSÄCKER (Interviewed in 1992): When I first understood that nuclear weapons might be possible—that was in February '39 —then I felt, if such a weapon is possible, there will be somebody who makes it. And if there is somebody who makes it, it will be used. And then I felt, "This is the most important thing which will happen in my life." And my reaction was: "It is true that Hitler will begin a war this year, but Hitler will not persist, but the bomb will be there forever. And therefore, since I am a physicist and I am able to work in this field, and since I am politically interested, I must, in any case, enter this field. I cannot keep outside."

NARRATOR: Working together, Heisenberg and von Weizsäcker soon made a crucial discovery. Before the war, scientists had realized that you couldn't make a nuclear bomb from ordinary uranium, but the two German physicists worked out how, in theory, you could turn uranium into the raw material for a bomb.

MARK WALKER: The Germans recognized that natural uranium cannot be used as an explosive, but you can put it in a nuclear reactor, you can have a sustained controlled nuclear fission chain reaction, and what happens is that the natural uranium, some of it, is transformed into element 94, a transuranic element we now call plutonium, and plutonium is a nuclear explosive.

CARL FRIEDRICH VON WEIZSÄCKER: I realized that to make a bomb would be possible with what we now call plutonium, directly, and that plutonium or eka-uranium as I then said, would be produced in reactors, by the fact that the reactor works.

NARRATOR: But to turn these ideas into reality, the Germans needed one vital ingredient: heavy water.

DAVE WARK: In order to make a reactor work, you have to slow the neutrons down by colliding them with something we call a moderator, which slows them down without absorbing them. And it turns out that, in principle, the best moderator is actually heavy water.

And the Germans soon realized that if they had enough heavy water as a moderator, they could actually make a reactor work with natural uranium, and from that they could extract plutonium and produce a nuclear explosive. And, and that's then the link between heavy water, which by itself is harmless, and nuclear explosives.

NARRATOR: But the Germans were not the only ones to work out a theoretical route to the atom bomb. Scientists in Britain came to the same conclusion, and when America entered the war in December 1941, the two Allies pooled their scientific resources in the vast Manhattan Project.

DAVE WARK: People tend to think of the Manhattan Project as a few physicists on a mesa in New Mexico. In fact, it had the largest industrial facility ever built in the world: the gaseous diffusion plant at Oak Ridge. It included the huge reactor facilities at Hanford, facilities at Berkeley and Chicago, and it was bigger than the U.S. auto industry of the time. It spent a huge amount of money. It was really an enormous effort.

NARRATOR: Allied scientists knew all their work would be in vain if the Germans got there first. But German progress depended on a steady supply of heavy water, which British intelligence and the Norwegian resistance were determined they would not get.

At the dive site, the team has finally met with success. They've sighted several barrels, including one that looks intact. They're getting ready to lift it as physicist Dave Wark arrives.


DAVE WARK: Hello, I'm Dave.

BRETT PHANEUF: Brett. How are you? This is Fredrik.

FREDRIK SOREIDE: Hello. Pleased to meet you.

DAVE WARK: Pleased to meet you.

FREDRIK SOREIDE: We've found nine barrels so far, one on the ship and then eight on the lake floor around the ship, two very close to the shipwreck. And we have selected the one that looks the best. That's about 60 meters away from the shipwreck itself. And it looks complete, and we hope that it will contain heavy water.

JONNY SKOGSTAD: So we're heading for that one now.

NARRATOR: On the lakebed, the R.O.V. inches toward the target.

FREDRIK SOREIDE: Yes, it's a barrel at the end of it.

DAVE WARK: Oh yeah.

BRETT PHANEUF: Ah, that's a barrel.


DAVE WARK: Can you read anything on the end of it?

FREDRIK SOREIDE: Is it a five? Upside down five?

JONNY SKOGSTAD: I don't know. See? It could be.

NARRATOR: To lift the barrel, a specially designed grapple has been attached to one of the R.O.V.s. Thor has to position it in exactly the right place over the rim.

THOR OLAV SPERRE: This is just once.

DAVE WARK: You get one try?

THOR OLAV SPERRE: Yes, it's only one try.


FREDRIK SOREIDE: Cross your fingers.

JONNY SKOGSTAD: Yes, we do. Contact.

No, where is it?

DAVE WARK: It slipped off.

JONNY SKOGSTAD: You have enough tether out?

DAVE WARK: Oh, there.

NARRATOR: The next delicate step is to let go of the grapple.

ALL: There.

FREDRIK SOREIDE: And they're off. Okay. And then the connector is hanging—you can see the connector's hanging there—so we have to pull out that one too. Okay, now this is the point of no return; now it either comes or it doesn't.

DAVE WARK: When you pull it up?

NARRATOR: The barrel is buried deep in the mud. They'll have to pull very hard to get it out.

FREDRIK SOREIDE: They're just discussing if the rope will take the tension or not.

DAVE WARK: Isn't now a bad time to worry about that?

FREDRIK SOREIDE: That's what he's saying.

Pull. Pull up. Go on and pull. That's what he's saying.

THOR OLAV SPERRE: Okay, they're pulling.

DAVE WARK: No sign of any movement yet. Can they tell how much force they're putting onto that winch?

JONNY SKOGSTAD: No, not exactly.

FREDRIK SOREIDE: Suddenly it will just go. Yeah, it will pop free. So it's hard to say exactly when it's going to happen.

There is a slight movement in it. Okay. It's coming, it's coming. Okay.

DAVE WARK: Boom! Goodbye. A barrel on a bungee.

And did you see the bottom of the barrel when it came up? The paint was still on it.

Don't drop it!

NARRATOR: The underwater cameras on the R.O.V. provide the first close look at the barrel in 60 years. It appears intact, but the smallest of holes is enough to contaminate any heavy water it may contain with lake water. Luckily, the process of electrolysis which concentrated the heavy water should have left traces, which will allow Dave to test for contamination.

DAVE WARK: The barrels contain heavy water, we hope. But to make the heavy water, to separate it originally, they had to add something else to make the water conduct electricity. They added something called potash lye, which is actually potassium hydroxide, which will make the water very caustic. Now, we measure whether water is caustic or not on a scale called pH. Well, now we're going to want to know whether the pH in the barrel is different than the pH in the lake water, so I have to know what the pH in the lake water is. So now I'm going to test it and find out.

Okay, now you can see it's about nine, which is a little higher than you expect for ordinary water, but still much less than you would expect for the material in the barrels, which should have a pH of about 14. So when we open up a barrel, if it's 14, it's probably uncontaminated. If it's nine, it's just lake water.

THOR OLAV SPERRE: We have a barrel in very good shape, I think.

FREDRIK SOREIDE: We have secured the barrel with two straps, because we couldn't lift it out of the water with this hook that we've put on it; that would be too much stress on the barrel. It's still going to be quite a bit of stress on the barrel as we lift it through the water, take that very slowly, and make sure it doesn't bump it and things like that.

DAVE WARK: It was absolutely fascinating to actually see that barrel come up. You think of the Second World War as something that happens in grainy old movies from your dad's era. You don't think of it as something immediate. And to see the actual barrel come up out of the water is an amazing experience.

JONNY SKOGSTAD: But can you see the number here now?

Yes. It's 26.

DAVE WARK: It's perfect, the corrosion goes at one angle and the dirt goes in another, and there's a little clear sector left, and the 26 is right in the middle of it like it was planned that way.

JONNY SKOGSTAD: But you know, nothing is pouring out, and it's full of something.

DAVE WARK: Well, we've got the barrel, and we can clearly read the number on the end of it, which is fantastic. It's barrel Number 26.

NARRATOR: So the question is, have the contents of the barrel been contaminated with lake water?

JONNY SKOGSTAD: Oh, it's coming. It's coming up, Dave.

DAVE WARK: Yeah, just go very slowly; let it release the pressure.

FREDRIK SOREIDE: It's amazing. It comes up and you take off the lid.

JONNY SKOGSTAD: The gasket is good still, you know?

DAVE WARK: Yeah, they built them good back then.

JONNY SKOGSTAD: Very good. Look here. It's still boiling.

DAVE WARK: Be careful here, careful, careful, careful. Precautions being taken here; potassium hydroxide is very, very caustic.

JONNY SKOGSTAD: It looks clear.

DAVE WARK: There it is.

JONNY SKOGSTAD: This I think is good stuff, Dave.


JONNY SKOGSTAD: It's not like water, you know? It's a bit more softer viscosity.

DAVE WARK: I'm now going to measure the pH, just put this meter in the solution and wait a few minutes for it to equilibrate.

JONNY SKOGSTAD: It's good stuff?

FREDRIK SOREIDE: Fourteen, that's your guess, wasn't it? Are you satisfied?



DAVE WARK: Sixty years! It's exactly the way it was the day they put it in there. I will be damned!

JONNY SKOGSTAD: Yes you will. Okay, shake hands with this. And do I also get a kiss? No?

DAVE WARK: Fantastic.

JONNY SKOGSTAD: They sank it and believed it should never come to the surface again. Everyone said it's gone forever. But after 60 years it's still there, you know.

DAVE WARK: Well, I mean, it's an incredible feeling. It was a heck of a lot of work to get this. So we have to get this back to the lab in London, so we can find out what the purity of the heavy water really is.

NARRATOR: Because, amazingly, the number of the barrel is still legible, Dave will be able to do far more than just check if it contains heavy water. In the archives of Norsk Hydro, Per Dahl has found documents describing the entire shipment aboard the Hydro when it sank.

PER F. DAHL: Here is a list of the various barrels transported on the Hydro ferry, and the amount of heavy water in each of those barrels in various concentrations.

NARRATOR: According to this manifest, the concentration of heavy water in barrel 26 was just one percent. To detect such a low concentration will require careful analysis. At Imperial College, London, Dave and his colleagues compare the infrared spectrum of the water molecules from the barrel with the spectra from samples of different known concentrations of heavy water.

DAVE WARK: We've tested the samples of heavy water here at Imperial quite a few times, and we can say, with considerable confidence, that that water is enriched in heavy water.

NARRATOR: The result is unequivocal.

DAVE WARK: It's about 1.1 percent, plus or minus 0.2 percent, heavy water, which, interestingly, is pretty much exactly what the manifest said it would be.

NARRATOR: So one mystery about the Hydro has been forever laid to rest.

DAVE WARK: We've learned there really was heavy water on the Hydro. Any speculations that the Germans had pulled some sort of swap are just not true; the shipping manifest appears to be largely correct.

NARRATOR: And that helps to clear up another puzzle. The manifest shows that the low-numbered barrels which contained the high concentration heavy water were little more than half full. That explains why some of them floated. It was probably these barrels, recovered by the Germans, which ended up in Berlin as reports after the war suggested. But it also raises a troubling question. It's clear from the manifest that most of the barrels contained only very dilute heavy water. Despite the apparent size of the shipment, the total quantity of pure heavy water was quite small.

PER DAHL: The Germans would have needed a total of about five tons of heavy water to get a heavy water reactor, nuclear reactor, running. The list here informs us, essentially, that about half a ton of heavy water was being transported to Germany.

NARRATOR: The Hydro was carrying far too little heavy water for even one reactor, let alone the 10 or more that would have been needed to make enough plutonium for a nuclear weapon. So, were the Allies right in their belief that the heavy water was destined for a bomb project? Did the Germans in fact want it for some other purpose?

Within a few months of the sinking of the Hydro in 1944, Allied armies were advancing across Europe. Following closely behind the frontline troops was a secret operation, code named Alsos. Its mission was to find the Nazi nuclear weapons program the Allies were sure must exist.

For months, Alsos scoured newly-liberated Europe and found nothing. Then, just days before the final German surrender, they came to Haigerloch, a small town in Bavaria. Beneath a church there was a cave, and inside they found the intended destination of the Norwegian heavy water: a makeshift laboratory with a single experimental reactor that German scientists still had not gotten to work.

The Nazi nuclear bomb, which had inspired so much fear, turned out to be a mirage. There was no German equivalent of the vast Manhattan Project.

The reason, believes historian Mark Walker, can be found in a decision made in early 1942, just at the time when the Allies were also deciding whether to embark on the Manhattan Project.

MARK WALKER: In early 1942, precisely when the Allies are getting concerned about Norwegian heavy water, American officials and German officials make crucial decisions about their nuclear weapons projects. Interestingly, scientists in both countries said the same thing; the scientific results were essentially the same. Scientists in both countries said, it'll take a couple of years, but nuclear weapons are possible. Now, in America it was assumed that the war was going to take a long time: "These weapons will be done before the end of the war, therefore we have to try to make them." In Germany it was assumed that: "If we don't win the war quickly, we will lose; these weapons might be interesting for the future, but they're no help to us now. It would be a waste of energy, money, and time to try to make them."

NARRATOR: So German nuclear research was transferred to civilian control. The Hydro shipment was destined for an experimental reactor project. It was of no military significance, which is why it was only lightly guarded. So it seems that the doubts the Norwegian resistance expressed about the value of sinking the Hydro were justified. Had Allied intelligence known what we know today, they might well have agreed that the shipment was not worth stopping.

PER F. DAHL: I would say that the Allies were not paranoid, as such. Rather, they were surprisingly uninformed about what was going on in Germany in nuclear physics.

DAVE WARK: The German program was very leaky. They were telling journalists in cafes what they were up to, and yet, the Allies don't seem to have made much of an effort to really penetrate this program and learn more about it. I would call that a critical intelligence failure.

NARRATOR: None of this, of course, takes away from the heroism of Knut Lier Hansen and his comrades. They chose to take up arms against a brutal invader at great risk to themselves. They knew their actions would lead to the death of innocent civilians; but the bitter truth is that World War II, like most modern wars, claimed mainly the lives of the innocent.

DAVE WARK: They asked London. London said immediately, "Sink it." And they did what they were told. It would be like asking me to blow up the 8:45 train to London. I'd be absolutely certain there'd be friends, maybe even relatives of mine on that train, but if there's any chance that Hitler's going to get an atomic bomb, what else can you do?

BRETT PHANEUF: I think you have to look at it and get it all straight for once and for all, for everybody, for the history books, and not worry about who might be offended, because it's not about that. It's not about criticizing what they did. I would have done it if I had been given the orders. I like to think that I'd follow the orders.

DAVE WARK: I don't think I would have had the guts to do what they did.

BRETT PHANEUF: No. They were special guys though.

NARRATOR: The sinking of the Hydro was just one part of a daring Norwegian resistance effort. Hear more of the story on NOVA's Web site. Hitler's Sunken Secret: find it on

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Hitler's Sunken Secret

Produced by
David Sington

Directed by
Duncan Copp

Narrated by
Neil Ross

Associate Producer
Sarah Kinsella

Edited by
Christy Hanna

Clive North

Sound Recordist
Kevin Meredith

Underwater Camera
Mike Valentine

Judith Edelman

Paul Chandler

Production Manager
Selina Kay

Online Editor and Colorist
Mike Curd

Audio Mix
Danny Finn

Special Thanks
Brian Desmond
Per Pynten
Ingelin Bystom
Norsk Industriarbeidermuseum
Thor Olav Sperre
Jonny Skogstad
Jon Olav Boen
Karl Ingar Asland
Jan Borgen
Oystein Haugan
Norges Hjemmefrontmuseum
Rjukan Turistkintor
Chemistry Department Imperial College London
Lydia Wilson

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Musikvergnuegen, Inc.

Additional NOVA Theme Music
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Post Production Online Editors
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Jonathan Renes
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Senior Researcher
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A NOVA Production by DOX Productions Ltd for WGBH/Boston in association with ZDF and National Geographic Channel International

© 2005 WGBH Educational Foundation

All Rights Reserved

Hitler's Sunken Secret

Nazis and the Bomb

Nazis and the Bomb
How close were the Germans to a nuclear weapon?

Norwegian Resistance Coup

Resistance Coup

A midnight raid was the master stroke of a broad insurgency.

See the Spy Messages

See the Spy Messages
Read the actual telegrams sent between Norway and London.

Dangerous Water

Dangerous Water
What is heavy water, and what makes it a threat?


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