The professorship fell through when the Minister for Education, Tage Erlander, unexpectedly became the Prime Minister of Sweden in 1946, but Borelius and Klein ensured that she had the salary of a professor, if not the title. In 1949, she became a Swedish citizen, but without surrendering her Austrian citizenship thanks to a special act passed by the Riksdag. Plans were approved for R1, Sweden's first nuclear reactor, in 1947, with Eklund as the project director, and Meitner worked with him on its design and construction. In her last scientific papers in 1950 and 1951, she applied magic numbers to nuclear fission. She retired in 1960 and moved to the UK where many of her relatives were.