When you learn History at school, many facts are put aside by lack of time and interest.
I studied in France and therefore was taught about WWII from a French perspective. This is why I was never told about the role Norway played at that time.
I only learnt about the importance of the Norwegian resistance this year when my father and godfather decided to go on a day trip to Rjukan to visit a factory where heavy water was produced.
I’ve heard about heavy water before and knew that it was used to produce bombs but my knowledge stopped there.
To be honest, I wasn’t very pleased to go to Rjukan because it meant that I had to drive as my father had a lumbago. And driving in Norway isn’t really a pleasure: the speed limit is too low and there are too many swings and sheeps.
But when you’ve low expectations, you’re rarely disappointed. And it turned out that I was very happy with my day.
The Vemork power plant was completed in 1911 and was the world’s largest hydropower station at that time. Its main purpose was to fix nitrogen for the production of artificial fertilizer.
In 1934, at Vemork, Norsk Hydro built the first commercial plant capable of producing heavy water as a byproduct of fertilizer production.
But what exactly is heavy water?
Like ordinary H2O water, each molecule of heavy water 2H20 or D20 contains 2 hydrogen atoms and 1 oxygen atom.
The difference, though, lies in the hydrogen atoms. Indeed, in ordinary water, each hydrogen atom is composed of just a single proton in its nucleus while in heavy water each hydrogen atom is composed of a neutron and a proton in its nucleus. Therefore, heavy water is heavier.
In its pure form, heavy water has a density about 10% greater than water, but is otherwise physically and chemically similar than plain water.
Heavy water is found in plain water in the ratio of 1 D atom to 5,000–7,000 H atoms.
How was heavy water discovered?
In 1913, chemists Arthur Lamb and Richard Leen tried to find a definitive value for the density of pure water, but despite meticulous experiments, they kept getting varying results. Their “failure” was, in retrospect, an important evidence for the existence both of heavy water and isotope.
Heavy water was finally discovered in natural water by Harold Urey and E.F Osborn in 1932 using the technology of spectroscopy.
And the first sample of pure heavy water was then isolated by electrolysis in 1933 by Gilbert Newton Lewis.
How is heavy water produced?
Heavy water is naturally present in plain water, so it’s more accurate to speak about “isolating” rather than “producing” it.
Separating heavy water from plain water requires significant quantity of water because, as we saw above, heavy water is found in plain water in the ratio of 1 D atom to 5,000-7,000 H atoms.
The electrolysis technique consists in sending an electric current through water to separate it into its elements, relying on the fact that H20 breaks more readily than D20. Consequently, the residual water left after electrolysis is relatively rich in D20.
Heavy water is then purified by reprocessing the residual water over and over again.
From its opening in 1911, Vemork produced artificial fertilizer by fixing nitrogen from air thanks to electrical arcs. But the method was inefficient and was replaced by electrolysis in 1927.
In 1934 heavy water was produced as a byproduct of the fertilizer production.
With the discovery of nuclear fission in December 1938, heavy water became a component of early nuclear research because it could slow the neutrons so they could react with the uranium in the reactor.
The Germans took the control of the Vemork plant and therefore the production of heavy water just after the occupation of Norway in April 1940.
About a month after, the Nazis increased the heavy water production. The British intelligence feared that they would use the water to develop an atomic bomb.
The Allies and the Norwegian resistance fighters had to act and set up sabotage actions.
Vemork was easy to oversee thanks to its remote location, perched on the edge of a cliff and only accessible by a bridge spanning a deep ravine.
Not less than 4 military operations were required to completely destroy the heavy water production and stop Hilter’s ambition.
Operation Freshman – 19 November 1942
It all began in March 1942 when a Norwegian engineer had successfully sailed to Britain and was parachuted back to Telemark after 10 days of intensive training to gather intelligence about the production of heavy water. Having several contacts within Vemork, he was able to roughly identify the disposition of German troops and other defences.
On 19 October 1942, 4 Norwegians were dropped west of Rjukan. They were all local boys and knew the area well. Their task was to prepare the sabotage operation and to send radio messages to England.
A month later, on 19 November 1942, a British sabotage group of 34 specially-trained men was dispatched from England. Their task was to destroy the heavy water plant at Vemork.
But then disaster struck. The weather conditions were extremely bad and the 2 planes crashed. Those who weren’t killed outright were taken prisoner, tortured and then executed.
The 4 Norwegians were forced to spend the winter hiding in the harsh wilderness of the mountain, eating what was left of their rations, and supplementing their diet with wild reindeer meat.
Operation Gunnerside – 27 February 1943
After the disastrous Operation Freshman, London decided that a new group was to join forces with the former group and carry on the sabotage.
On 16 February 1943, a new group composed of 6 young Norwegians soldiers specially trained for the mission were parachuted but landed 50 km away from the planned position and had to walk many days into a blizzard before they met their compatriots.
On the evening of 27 February 1943, the saboteurs started skiing towards the Vemork plant.
Following the failed Freshman attempt, the Germans had put mines, floodlights, and additional guards around the plant. While the mines and lights remained in place, security of the actual plant had slackened somewhat over the winter months. However, the single 75 m bridge spanning the deep ravine, 200 m above the river was guarded 24/24 so their only possibility to reach the factory was to cross the gorge.
Just over midnight, they managed to blow up the heavy water production without being detected. The explosion tore apart the heavy water cells and 500 kilos of heavy water went down the drain. There were no prisoners, and not a life was lost during the operation. The operation was a success.
Bombing Vemork and Rjukan – 16 November 1943
Although this attack did no irreparable damage to the plant, it did stop the production for several months.
The Allies concluded that a repeat commando raid would be extremely difficult, as the Nazis had been considerably improved the security around the site.
On 16 November 1943, the American Forces bombed Vemork and Rjukan without having first informed or consulted the Norwegian government in London.
Over 700 bombs were dropped over Vemork but only 18 hit the plant. The hydrogen facility and the power station were considerably damaged but only about 60 kilos of heavy water was destroyed during the operation, less than a month’s work.
The Germans were forced to abandon their plans for producing heavy water, but the raid claimed more than 20 Norwegian lives.
Sinking D/F Hydro – 20 February 1944
The Germans were convinced that air raids would result in further serious “hits” and decided to abandon the plant and move remaining stocks and critical components to Germany in 1944
The saboteurs discovered the plan and received the order from London to destroy the heavy water shipment at all costs and by any means.
The weakest link in the transport chain was the ferry carrying the train across Lake Tinnsjø and it was then decided that they had to sink the ferry.
The night before the ferry was due to depart, the saboteurs easily managed to place time explosive charges on board as it wasn’t guarded.
On 20 February 1944, D/F Hydro was half-way across the lake when the charge explosed. The ferry sank within minutes, taking the vital heavy water down with it to rest at a depth of 460 meters. 4 Germans and 14 Norwegians perished, but the battle for heavy water was now finally over in Norway as Germany’s atomic bomb development program was halted.
The heavy water plant in Vemork was closed in 1971 when the , and, in 1988 the old power station became the Norwegian Industrial Workers Museum.
The new power station opened in 1971 and is located in the mountains inside the old one.
The hydroelectric power station ceased operations in 1971 when the new one opened in the mountains inside the old one. It was converted into the Norwegian Industrial Workers Museum in 1988. As for the hydrogen/heavy water plant, it was demolished later in the 1970s.
If you want to learn more about the Heavy water war, you can watch the american film “Heroes of Telemark” from 1965 or the TV series “The Saboteurs” from 2015. But if you’re looking for something more authentic, you should definitely watch the Norwegian-French film “The Battle for Heavy Water” (original title: Kampen om tungvannet), which features performances by some of the original participants in the raid!