R1 was the first nuclear reactor of Sweden. It was a research reactor located at the Royal Institute of Technology (KTH) campus at Valhallavägen in central Stockholm, in the rock beneath the current-day Q buildings. The reactor was active from July 13, 1954 to June 6, 1970. The reactor was dismantled, and there is nothing left of it today; the reactor hall however still exists.
The capacity of the reactor was originally 300 kW but was later increased to 1 MW.