Radiometric dating equation used
This also made for rapid heating of the earth interior (cool to start with).
Furthermore, there is evidence that the main radioactive elements were concentrated in a layer low in the mantle and came to the surface progressively after that.
With high c values, it can be shown that atomic particles moved faster, proportional to c. The high-speed neutrons were not near the uranium nucleii long enough to produce any reaction, just as high-speed neutrons are today.
As the water vapor condensed and reformed, the reaction would pick up the pace again.
-- some quotes on radiocarbon dating Change in Decay Rates Atomic Ages Cesium 133 Oldest Living Tree?