Leif Tronstad

Chemistry professor in Trondheim and WWII hero of Telemark

On May 1st 1936, Leif Tronstad was appointed professor of technical inorganic chemistry at The Norwegian Institute of Technology in Trondheim. Born and raised in the village of Sandvika near Oslo in 1903, he was a top honours graduate <“innstilling til Kongen”> of 1927 from the same institution, and received his doctorate there in 1931.

The scientist
Tronstad’s academic career brought him in close contact with the leading European scientists in his field. His first major scientific contributions came in 1928–29 when he was a guest scientist in the laboratories of professor Freundlich at Berlin. Tronstad improved greatly a method for measuring extremely thin oxide coatings on metal surfaces, a vital property of light metals like aluminium. After receiving his doctorate, Tronstad went to Cambridge, to research and improve the polarized light method of studying films on metals further. It can be employed for just that range of thickness where alternative methods are least useful. Moreover, the method can be used for the continuous study of a film in situ during its growth in almost any environment.

In Britain he made and maintained personal scientific contacts that became important both for the war effort, and for Norwegian science as a whole during and after the war. An obituary in “Nature” of 1945 describes him as follows: “Tronstad was greatly attached to Great Britain, where he had many friends. His modesty, sincerity and cheerful good-humour were appreciated by all who met him. He had numerous interests outside science; for example, he was a fine athlete, being in his student days a member of the relay team which set up a Norwegian record for the 4 x 400 metres distance; he was also a lover of natural beauty, and took pride in Norwegian country folk and customs.”

Leif Tronstad was highly talented both as scientist and teacher. He was one of the youngest professors in the country, popular alike with students and colleagues, and had a rare ability to stimulate the students’ enthusiasm. He attracted the best students, leading them to independent scientific work. Being a modest person, treating all as equal, and always helpful, it is a worthy cliché to say he was loved by both students and co-workers. In his research he both created a stimulating scientific environment, and a productive one. Alone or with co-workers, Tronstad published some 80 scientific papers. The figure is impressive taking into account the short period he actually was involved in science. The papers covered a variety of topics; 41 on metal surfaces and corrosion, 14 on heavy water, deuterium and deuterium derivatives, 5 on fuel-related topics, like coal from Svalbard, and the rest on various aspects of metals. He was a member of the Royal Norwegian Society of Sciences and Letters in Trondheim, and in 1940 vice-president of the Norwegian Chemical Society.

The heavy water and the atomic bomb
After Harold Urey’s discovery of heavy water in 1932, the main concern was with its chemical and biological properties. No thought of nuclear energy production arose at the time, although the use of deuterons (“heavy hydrogen”) as bombarding particles in nuclear experiments had been quickly taken up. The energy resources needed for separation of heavy water on a large scale already existed in Norway, in the country’s vast investment in hydroelectric power.

In 1933 Leif Tronstad, in association with Jomar Brun, the head of Norsk Hydro’s hydrogen electrolysis plant, realized that the conditions for large-scale production of heavy water existed at Norsk Hydro's plant in Rjukan, where large amounts of water were already being electrolyzed for producing ammonia for nitrogen fertilizer. Brun, also a graduate from The Norwegian Institute of Technology in Trondheim, had been employed by Norsk Hydro since 1928. Together they drew up a plan for the industrial production of heavy water. It was in many ways an astonishing venture as a large amount of equipment had to be built – hundreds of combined electrolysis, combustion and condensation cells – into a cascade process, coupled with recycling, culminating in more than 99 % pure heavy water. This was the first industrial scale production of heavy water in the world. Although the market must have been uncertain, Norsk Hydro built a plant according to Tronstad’s and Brun’s design, next to the generator building at Vemork, just outside Rjukan in Telemark County. By January 1935 the material was becoming available in amounts of more than 100 g at 10 % of the American price at the time, and in 1938 about 80 kg was produced.

This engagement by Tronstad and Brun would soon greatly benefit the WWII fight to prevent the possible construction of a German atomic bomb. Scientifically, Tronstad and Brun themselves did important standards work on the physical constants of heavy water.

The intelligence officer
Quite a different aspect of Tronstad’s life and career – and perhaps more widely known – stems from his professional background as an officer. During his studies at The Norwegian Institute of Technology he finished a military education, obtaining the rank of second lieutenant in 1927, in the Norwegian Army Corps of Waponry <”hærens våpentekniske korps”>. In wartime he was to report to the HQ in Oslo. On the day of the German invasion of Norway, April 9th 1940, he informed the students to report to the nearest army mobilising centre. Himself he headed by car with his family for Oslo. Under way he learned that Oslo was already occupied, and stopped in the Dovre mountains to organise volunteers from the local rifle associations for a line of defence. This was familiar terrain, as the family had a cabin in the area. When the war operations in southern Norway ceased in the late spring of 1940, he joined the underground resistance.

After the German capture of the Rjukan heavy water plant in May 1940 nothing more was heard about the subject for a year, until a strange message from the Norwegian underground reached British intelligence in the summer of 1941, referring to "heavy water": production was being increased on German orders, was additional information desired? The British intelligence officer most certainly did desire it, and queried back for addi¬tional information.

One of the Norwegians who got to know the visiting Germans at the heavy water plant well was the engineer Jomar Brun, who had helped to design the Rjukan plant.

The Germans had forced Norsk Hydro to step up its production. By the end of 1941, the output was about 100 kg per month more, and further production improvements were in the making. Jomar Brun, still in charge of the electrolysis plant, kept Leif Tronstad informed of these developments. Receiving a last minute warning that he was hunted by the Gestapo, Tronstad escaped to Sweden, and arrived in England on September 21, presenting himself as the source for the previous information. The handling British Intelligence officer – who also had a scientific background – was astonished to discover that he knew the man's name and work. But knowledge of the Rjukan facility was not Tronstad's only asset; behind him in Scandi¬navia he had left two well-placed friends – Njål Hole, a young Norwegian scientist who had taken his degree in physics at Trondheim in 1938, and Harald Wergeland, also a technology graduate from Trondheim, and a friend of the German nuclear physicist Karl Wirtz. Wergeland was in Oslo, where he was already active in the Norwegian underground, and Hole was working in Manne Siegbahn's laboratory at the University of Stockholm, where he saw Lise Meitner almost daily. Tronstad maintained his contacts with Wergeland and Hole, giving British intelligence in the fall of 1941 a frail network of agents in Sweden and Norway who reported on German in¬terest in the Rjukan heavy water plant. After the war both Hole and Wergeland were appointed professors at The Norwegian Institute of Technology in Trondheim.

But on his arrival in Britain Tronstad also brought bad news. In the fall of 1941 heavy water production at Rjukan had been increased ten times and was now more than 4 kilograms a day. When the discoverer of heavy water, Harold Urey, visited Britain that November, it was arranged for him to meet with Tronstad. The British very much wanted American help in developing the atomic bomb and hoped that a firsthand report of German interest would spur them on. Like the British, Urey concluded immediately from Tronstad's report that German orders for heavy paraffin meant they must be working on a reactor.

It was a combination of Tronstad's news and a simple process of elimi¬nation that convinced the British that the Rjukan plant should be made a top pri¬ority of British intelligence. They had given a lot of thought to identifying the vulnerable points in any German bomb program. Many dif¬ferent materials would be required for a German bomb, but only two of them were difficult to obtain – uranium and heavy water. Whereas the production of uranium had several sources, and not so easy to stop, the Norsk Hydro heavy water production plant at Vemork was vital.

The sabotage actions at Vemork – “Heroes of Telemark”
Upon his arrival in England, Tronstad’s own request was to enter active service, but of course this was denied by the Norwegian military authorities in England, as he was too valuable. He eventually obtained the rank of major and became a leader of a unit with special responsibility for operations against Norwegian industry and coastal shipping, training of commando units for operations in Norway (“kompani Linge”), and technical guidance in sabotage. One of his first tasks were, however, to work out a complete guide to Norwegian industry of importance to the wartime economy. He was in close contact with both the SOE and the Norwegian resistance.

In January 1942, the Germans summoned Brun to Berlin, where he met the German physicist Karl Wirtz – which he knew very well – and other German scien¬tists in Kurt Diebner's office to discuss yet another expansion of heavy water production at Rjukan. Later, at Wirtz's invitation, Brun visited Berlin-Dahlem. Although he was not shown through the secret laboratory Wirtz had designed, he did see in Wirtz's office two large glass jars con¬taining some thirty-six gallons of heavy water. Brun remarked that glass seemed an oddly fragile container for more than a month's production of heavy water at the Rjukan plant.

Only a few months after his trip to Berlin, Brun came into contact with Einar Skinnarland, a native of Rjukan and an agent for the British Special Operations Executive (SOE). Skinnarland communicated detailed intelligence about the plant from Brun to England.

Leif Tronstad vigorously resisted proposals to bomb the plant: if the liquid-ammonia storage tanks at the chemical complex were hit in a raid, every citizen in the nearby town of Rjukan would be threatened. Tronstad’s and Brun’s thorough knowledge of the facility would prove crucial in planning and completing the sabotage missions to come. It was understood from the outset that a sabotage raid would be hazardous in the extreme and run the risk of alerting the Germans to British interest in the field. Also at risk was [the Rjukan engineer] Jomar Brun, who received notice from Tronstad through the underground in mid-October 1942 to pack up and depart for Britain without delay, which he did. In was in fact Winston Churchill himself that had wanted Brun to come to England, showing the attention the heavy water received at the highest level.

The first attempt at destroying the heavy water plant, in November 1942, using commandoes in gliders, failed tragically. In England, careful plans were made for a second attempt.

In February 1943 a brilliantly executed operation by a team of Norwegian SOE-agents destroyed all of the final-stage concentration cells, along with the heavy water contained in them. Production was, however, resumed in May 1943. In November the plant was badly damaged in an American air raid, and in December, by German orders, the production of heavy water there was discontinued, with a view to setting up a replacement operation in Germany itself. However, there remained stocks of material near Rjukan awaiting transport to Germany. In February 1944 the ferry that was to transport it on the first stage of that journey was sunk in another daring sabotage operation, which ended this particular phase of the war.

The sabotage operations at Rjukan was later to be judged the most successful sabotage actions in German-occupied territory during WWII.

It should also be noted that Leif Tronstad was involved in the intelligence work behind the successful bomb attacks against the German missile-testing site at Peenemünde, that seriously hampered the production of V-2 rockets.

During his years in Britain Tronstad became closely connected to other Norwegian expatriate scientists, and member of The Technical Committee in the Norwegian High Command <”Forsvarets Overkommandos Tekniske Utvalg”>. This group convinced the Norwegian authorities in Britain that science was important, a notion not so easily accepted by politicians before the war. The activities in this Committee led to the establishment of the Norwegian Defence Research Establishment in 1946. Through the close contact with the British scientists, Norwegian scientists gained important insight for the post-WWII era.

Operation Sunshine – the protection of hydroelectric powerplants and indutry
Another of Tronstad’s duties were to safeguard the hydro-electric industrial plants in southern Norway, like Norsk Hydro, from possible scorched-earth operations by the occupying forces. He arranged to be parachuted into the country to organize the Norwegian resistance forces to counter this. In October 1944, a party led by him landed on the Hardanger Plateau.

In March 1945 Tronstad and two companions had lured the local county sheriff – known for his collaboration with the German occupiers ¬– to come to their cabin. They wanted to find out what he knew about resistance work in the area, and what he had told the Gestapo. But the sheriff’s brother had followed their skitrails in the snow to the cabin. His assault on them came by surprise, and Tronstad and one of his fellow resistance fighter were killed in the turmoil. The sheriff and his brother left hurriedly. After the war they were both sentenced for the murders.

Leif Tronstad was buried may 30th 1945 in Oslo with full military honours. Among the numerous decorations he received for his activities were the Order of the British Empire. Several streets have later been named after him, both in Oslo and Trondheim.

Jomar Brun survived the war, and was in 1951 appointed the first professor of technical electrochemistry at The Norwegian Institute of Technology in Trondheim. This was his alma mater were he had graduated in 1926, as a fellow student of the Nobel prize laureate in chemistry for 1968, Lars Onsager.

Selected sources/Further reading:

- Norwegian article about Tronstad.

- Dahl, Per F. 1999. Heavy Water and the Wartime Race for Nuclear Energy. Bristol/Philadelphia: Institute of Physics Publishing.

- Powers, Thomas. 1993. Heisenberg's War: The Secret History of the German Bomb.

- Brun, Jomar. Brennpunkt Vemork 1940-1945. ISBN 82-00-06864-1, 119 pages (1985), Universitetsforlaget.