The construction of the reactor cavern at the Lucens experimental nuclear power plant, November 13, 1964. (Keystone)
Keystone/Alain Gassmann
The entrance to the construction site of the nuclear power plant in May 1965. (Keystone)
Keystone
Employees handling fuel rods at the experimental nuclear plant in December 1966. (Keystone)
Keystone
Preparations for operational staff in radiation protection equipment to enter the reactor cavern at the Lucens plant after the accident on January 21, 1969. (Keystone/Joe Widmer)
Keystone/Joe Widmer
The control room at the Lucens plant, January 30, 1968. (Keystone)
Keystone
Workers at the Lucens nuclear plant were kitted out with protective clothing before entering the reactor cavern after the accident. Here pictured on January 29, 1969.
Keystone
Nearly ten years after the Lucens reactor accident, opponents of nuclear power plants at the anti-nuclear demonstration in Lucens in May 15, 1978. (Keystone)
Keystone
Fifty years ago today, a nuclear meltdown occurred in Switzerland’s first experimental nuclear power station. Built in an underground chamber in Lucens in the western part of the country, it was the site of the worst nuclear accident in Swiss history.
The plant was opened in 1962, with the aim of not only producing energy, but also allowing Switzerland to develop a reactor bearing the “Made in Switzerland” label and enabling experiments with nuclear energy.
But these plans were pushed aside when disaster struck in the plant’s reactor cavity on January 21, 1969. A pressure tube burst which created a power surge leading to the reactor malfunctioning and an explosion. Luckily, a member of staff who was scheduled to be working on the reactor at the time was found safe and sound elsewhere. The plant’s underground design also prevented people and the environment from being harmed.
The accident’s severity registered at 5 out of a possible 7. The concentration of leaked cooling gas that was behind the door of the reactor cavity was lethal. It wasn’t even possible to measure the radioactivity because it was above the maximum level on the measuring instruments.
But the reactor cavern was not completely sealed: the radioactivity spread to the control room 100 metres away. In the machine cavern closest to the reactor, a team involved in shutting down the turbine had been exposed to radiation. A witness report said that since the decontamination showers had been out of order, the workers had to shower in a temporary facility without hot water.
The government ordered an inquiry into the incident and a report was eventually published ten years later. The Swiss Association for Atomic Energy found there had been no major negligence on the part of the plant’s managers. The cause of the incident was corrosion in a pressure tube, brought about by humidity.
This content was published on
Over the next fortnight, some 300 tons of material will be transported 160 kilometres to a temporary site in the north of the country. “It’s the end of a historic chapter relating to the 1950s and 1960s, when nuclear stations were pioneered in our country,” the Swiss Association for Atomic Energy said in a statement…
This content was published on
At some point during my time inside the dome-shaped structure containing the reactor of Switzerland’s most powerful nuclear plant I became contaminated – perhaps a grain of radioactive dust had settled on my back and mingled with a bead of sweat. I was one of a dozen journalists to visit the open reactor at Kraftwerk…
You can find an overview of ongoing debates with our journalists here . Please join us!
If you want to start a conversation about a topic raised in this article or want to report factual errors, email us at english@swissinfo.ch.