context: The first nuclear reactor was built and launched in December 1942 in the United States under the leadership of E. Fermi. The first reactor built outside the United States was ZEEP, launched in Canada on September 5, 1945 [1]. In Europe, the first nuclear reactor was the F-1 installation, which was launched on December 25, 1946 in Moscow under the leadership of IV Kurchatov [2]. By 1978, about a hundred different types of nuclear reactors were already operating in the world.
question: When was the world's first nuclear reactor launched?
answers.text: December 1942