Some of this information is here...
Note the section on fuel melt tests.
Fuel Meltdown Tests: 1956-1959
At Oak Ridge National Laboratory (Tennessee) and elsewhere, the Atomic Energy Commission contracted varous private companies to conduct fuel meltdown tests. Meltdown studies with zirconium-uranium assemblies in a steam atmosphere were conducted by MSA Research corporation to provide data on fission product release, melt characteristics, and hydrogen formation. Some of the major results were:
the major fission products released are xenon and iodine with as much as 60% and 25% escpaing, respectively,
actual fission product release was greatly reduced by condensation in the reactor vessel,
core meltdown in a steam atmosphere results in considerable production of hydrogen gas, but that the possibility of a hydrogen explosion is small due, in part, to the lack of oxygen.
In another test at INEL in 1958, a series of meltdown studies with field releases of fission products were conducted to determine release quantities, airborne activity, and ground deposition of fission products.
In the TREAT experiments (Transient Reactor Test Facility) of 1959, a special reactorwas built to study nuclear fuel melting in thermal reactors. Although primarily suited to fast-reactor studies, the facility was also used for general meltdown research. FLECHT: 1970 - 1985
Performed by GE and Westinghouse, to assess the ability of emergency core cooling systems to cool the fuel pins and cladding during emergency conditions. It was demonstrated that the ECCS is designed to provide sufficient coolant to the core under most emergency conditions.