The place that changed the world

Heavy water cellar at Vemork, Norway, opens


Photo: M. Smatana / NIA
The Vemork hydroelectric power plant and the heavy water cellar, at Rjukan, Norway, is surrounded by a dramatic landscape.

Tinn, Norway

The events at the heavy water cellar at Vemork, Norway, have been called one of the most successful acts of sabotage in World War II. The cellar was the target of Norwegian soldiers under British command in the nights between Feb. 23 and 28, 1943.

After years of excavation and planning, the original cellar officially reopened on June 18. A new museum facility covers and protects the cellar. It tells the story of the historical events at the site where they took place.

The heavy water cellar located at the Vemork hydroelectric power plant near Rjukan, Norway, is a historic national heritage site of significant national and international importance. Here, visitors experience the history of the famous sabotage action that took place at Vemork 79 years ago.

Anna Hereid, director of Norwegian Industrial Workers Museum (NIA) said:

“In the light of present-day Europe, it is vital that we place great emphasis on telling the story about past times. As the scene of one of the most spectacular events in the war history of Norway, the heavy water cellar is a major destination for education in history and a monument to the Second World War.

“Surrounded by a dramatic landscape, the cellar and the new museum will be a place for learning and reflection, where innovative design and technology will ensure engaging means of conveying history.”


Image: Point AS
Illustration of the new museum facility will cover and protect the heavy water cellar at Vemork in Rjukan, Norway.

A successful act of sabotage

Operation Gunnerside in February 1943 was an extraordinarily courageous act of sabotage. The Hydrogen Production Factory at Vemork was fortified and heavily guarded in a nearly inaccessible part of Norway.

Penetrating this inaccessible location in the frozen mountains of Telemark, Norwegian commandos successfully destroyed the heavy water production that might have made it possible for the Nazi regime to develop an atomic bomb.

The operation was carried out without a single shot being fired, and the saboteurs escaped. Some of them went skiing for 17 days to get over the border to Sweden.

The spectacular story of the heavy water sabotage is known worldwide, especially through movies like Operation Swallow: The Battle for Heavy Water from 1948, The Heroes of Telemark by Anthony Mann from 1965, and The Heavy Water War from 2015.

The leader of the action, Joachim Rønneberg, was 23 years old at that time. Throughout his lifetime, he repeatedly stated that the cellar where the action was carried out must be made available to the public. That’s what has happened now.

heroes of telemark

Photo: Leif Tronstad collection
The true heroes of Telemark: Men from the Gunnerside team together in London. Behind from left: Hans Storhaug, Kasper Idland, and Birger Strømsheim. Front from left: Fredri Kayser and Joachim Rønneberg.

An archaeological project of great value

The heavy water cellar was built in 1935 and was part of the Hydrogen Production Factory at Vemork, opened in 1929. The factory was demolished in 1977, but in September 2016, the NIA began an excavation using an industrial archaeological method to find the original site of the World War II sabotage effort. On Oct. 5, 2017, the historical discovery was made; the heavy water cellar was found intact and in very good condition.

Dissemination of the findings of the excavation uncovered unique historical and cultural wartime/industrial heritage elements. The site will be of great value for organizations and individuals, local and regional, as well as international, for researchers, educators, tourists, and the public in general.

A special focus of the industrial archaeological excavation was to gain more know­ledge of the specific target of the Norwegian saboteurs in the heavy water cellar. All that was found has been kept intact for better understanding, observation, and research by current and future generations.

The largest power plant in the world

The first hydroelectric power plant at Vemork was an important part of Norsk Hydro’s industrial adventure in Notodden and Rjukand and a key element in the development of the Second Industrial Revolution in Norway. The power plant was the world’s largest when it was put into operation in 1911.

The Second Industrial Revolution contributed to changing the young nation of Norway and thus creating what still stands as one of the world’s best examples of a modern democratic welfare society.

The new museum facility has been constructed above the historic heavy water cellar and will present the cellar in its actual original state, as part of NIA’s work to preserve and present cultural heritage.

About the heavy water cellar

The Hydrogen factory at Vemork, in Rjukan, Norway, started production in 1929.

•    Hydrogen production requires large amounts of electricity. Therefore, the factory was erected close to the hydro-electric power plant at Vemork.

•    Production of hydrogen was part of Norsk Hydro’s change of technology, when the German Haber-Bosch process was introduced in 1928-1929.

•    Hydrogen is involved in the production of ammonia (NH3), which is used in the production of fertilizers.

•    Hydrogen production also made it possible to produce deuterium (D2O) heavy water.

•    During World War II, four military operations were aimed at the heavy water production at Vemork and Rjukan. Operation Freshman (1942) (Grouse was part of Freshman), Operation Gunnerside (1943), American bombing of Vemork and Rjukan (1943) and the sinking of the Tinnsjø ferry DS Hydro (1944).

•    Rjukan-Notodden industrial heritage is a UNESCO World Heritage Site (2015).

•    The heavy water cellar at Vemork is a part of the NIA and officially opened on June 18, 2022.

About the NIA |

•    NIA was founded on Nov. 3, 1983, with the social responsibility to promote knowledge about working culture, hydropower, electric power, and the electrochemical industry in Norway, as well as local cultural history, regional war history, culture/cultural heritage and art.

•    The foundation consists of: Vemork Power Plant, Tinn Museum, Heddal Bygdetun, Tuddal Bygdetun, Rjukanbanen, and Telemark Art Museum.

•    The museum functions as a world heritage center for Rjukan, Notodden Industrial Heritage Site. It is part of the Norwegian world heritage treasury and  was entered on the list of UNESCO World Heritage sites. in July 2015.

This article originally appeared in the July 8, 2022, issue of The Norwegian American.

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The Norwegian American

The Norwegian American is North America's oldest and only Norwegian newspaper, published since May 17, 1889.