Who interpreted the data that led to the understanding of nuclear fission?

Answer 1

Like so much of what we know, no single scientist can take the credit for figuring it all out. Lots of researchers and theorists attacked this problem and all of them built on the discoveries that came before them. Bequerel's discovery of radioactivity was vital, as was the work of the Curies. Ernest Rutherford created the first atomic model, which was later improved by Niels Bohr to incorporate quantum physics. Lots of other names can be added to the chain of discovery.

But the short answer is that nuclear fission was discovered Otto Hahns and Fritz Strassmann when bombarding uranium attoms with neutrons (Fermi came close but refused to accept the conclusion that fission was occuring). Evidently though, Hahns and Strassman couldn't quite make sense of their data and it was the calculations of Lise Meitner that led to the conclusion that fission had occurred and that some of the mass of the atom is converted to energy. Thus some argue that Lise Meitner is the one that should be credited w. discovering fission.

Answer 2

It was not a single person but Fermi generaly is given the most credit. see http://www.uic.com.au/nip50.htm
in 1932 Cockcroft and Walton produced nuclear transformations by bombarding atoms with accelerated protons
in 1934 Irene Curie and Frederic Joliot found that some such transformations created artificial radionuclides
in 1935 Enrico Fermi found that a much greater variety of artificial radionuclides could be formed when neutrons were used instead of protons.
In 1939 Otto Hahn and Fritz Strassman in Berlin showed that the new lighter elements were barium and others which were about half the mass of uranium, thereby demonstrating that atomic fission had occurred
Lise Meitner and her nephew Otto Frisch, calculated the energy release from this fission