UNITED KINGDOM:
Sloop HMS Snipe launched.
ITALY: Rome: Mussolini's daughter Edda is jailed for aiding Fascism.
USA: Washington: The McMahon Act (or Atomic Energy Act of 1946) is passed.
Like most legislation that dramatically impacts a nation's international relations was focused on domestic concerns. the primary focus of the Act was defining the control and development of atomic stuff (energy/weapons/etc.). During the war, it was under the military. The Federation of American Scientists and the Atomic Scientists of Chicago lobbied hard to ensure that after the war control was in civilian hands.
The Act created the Atomic Energy Commission and handed all atomic authority to the Department of Energy. Which is why to this day the DoE develops and tests American nuclear weapons for the military.
The prohibition on information sharing had a wide range of unintended impacts from Britain pursuing an independent nuclear force to Canada pursuing an independent reactor design, and the only use of the 'declarative power' of the Canadian Federal government (The Cdn Constitution (at the time British North America Act) enables the Federal Government to 'declare' an item of Provincial responsibility critical to the security of the state and move it to Federal constitutional authority - natural resources are a Provincial responsibility, except for uranium mining) (Dave Hornford)
Destroyer USS Warrington commissioned.