https://en.wikipedia.org/wiki/Tritiated_water references Jones (1952). "The Triple Point Temperature of Tritium Oxide". A Google Scholar search shows publications about "tritium oxide" in the late 1940s, like https://aip.scitation.org/doi/abs/10.1063/1.1746932 from 1948.

The linked-to piece says "1966, after nearly four years of work".

That puts at least 14 years minimum between them, and likely more.