The Swedish university that once hid a nuclear reactor under its campus
In short: Long before it was a global leader in engineering, KTH Royal Institute of Technology operated a high-stakes laboratory 25 meters underground. In the shadow of Stockholm's residential streets, scientists managed a live nuclear reactor, driven by a Cold War mission to master the power of the neutron.
The roots of KTH trace back to 1697, when Christopher Polhem, the 'father of mechanics' in Sweden, established the Laboratorium Mechanicum. What began as a collection of mechanical models for teaching evolved through the School of Mechanics (founded 1ob798) into the Technological Institute in 1827. While the institution's early years focused more on craftsmanship than advanced engineering, a period of reorganization under Joachim Åkerman in the late 1840s introduced formal entrance tests and rigorous scientific training.
One of the university's most daring chapters occurred in the post-WWII era. Following the American deployment of nuclear weapons, Swedish leadership sought to research nuclear defense. This led to the construction of Reaktor 1 (R1), a 300 kW reactor—later expanded to 1 MW—located 25 meters beneath the KTH campus. Despite the risk to the approximately 40,000 residents living within a 1 km radius, the reactor achieved criticality on 13 July 1954. It remained a cornerstone of Swedish nuclear research until its decommissioning in 1970, when the dangers of operating a reactor in a dense urban area became too great.
Today, KTH is a premier global institution, ranked 74th in the 2025 QS World University Rankings. It has transitioned from a small collection of books and mechanical models into a massive research engine, providing one-third of Sweden's research and engineering education. The university's motto, 'Vetenskap och konst' (Science and Art), reflects this legacy: 'art' refers not to aesthetics, but to the 'art of engineering'—the practical application of scientific knowledge.
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- Summary by Intellect · source: KTH Royal Institute of Technology
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