What is heavy water from ww ll?

Answer 1

Heavy water is water formed using higher proportions of deuterium and tritium, unstable and heavier isotopes of hydrogen, for ease of storage of those particles before use in nuclear reactions.

Answer 2

Same as heavy water now: D2O

In WW2 German scientists working on military uses of nuclear energy had made a mistake in measuring the neutron capture crosssection of graphite and decided it was not a usable moderator (material to slow energetic fission neutrons to thermal energies) for a reactor, instead they turned to heavy water. This was a serous mistake in wartime as there was only one plant in the world at the time that produced it in industrial quantity, Norsk Hydro in Norway, and the production costs are high. Graphite can be made almost anywhere and is cheap to produce.

The Allies repeated attacked the Norsk Hydro plant, slowing production and eventually forcing Germany to attempt to move it to Germany. However Norwegian Partisans sank the Ferry carrying these materials with a planted bomb (resulting in significant Norwegian loss of life as well as the Heavy Water and equipment).

The Manhattan Project used Graphite in their early test reactors and plutonium production reactors and had produced almost enough plutonium for the Trinity test bomb before Germany surrendered, and by July 1945 enough for at least 3 MK-III Fatman bombs: Trinity, Nagasaki, and one that was assembled but not used due to the Japanese surrender.

The German nuclear project still had yet to build their first Heavy Water test reactor and had not begun serious bomb design work at all by the time Germany surrendered. Some scholars speculate that Werner Heisenberg (leader of the German project) did not even understand the possibility of deliverable fission bombs until he read the British newspapers on the bombs dropped on Japan, but figured out how to make them the same day.

The Japanese nuclear project was even further behind: they were still just trying to build large cyclotrons to measure crosssections with. Even a small test reactor was years in the future.