[6] His group had responsibility for characterizing radioactive isotopes created by the fission of uranium and for developing a process for chemical separation of plutonium.

[5] In 1945 he was a member of the Clinton Laboratories team, with Jacob Marinsky and Lawrence E. Glendenin, that isolated the previously undocumented rare-earth element 61.

[7][8] Marinsky and Glendenin produced this element (later named "promethium") both by extraction from fission products and by bombarding neodymium with neutrons.

[12] Coryell was among the Manhattan Project scientists who in 1945 signed the Szilárd petition urging President Harry S. Truman not to use the first atomic bomb "without restriction," urging him instead to "describe and demonstrate" its power and give Japan "the opportunity to consider the consequences of further refusal to surrender.

[6] After World War II he joined the Massachusetts Institute of Technology (MIT) in 1945 as a faculty member in inorganic and radiochemistry.