What Would It Mean if the Rate of Radioactive Decay Was Accelerated by a Billion?

Even before man, some of the uranium deposits in the earth's crust should have gone crit just like at the oclo nuclear reactor. So if we have a uranium laden rock that seems to date from before the flood, we'd want to ask why it didn't melt or blow up. The real worry comes when we hit the billionfold radiation spike that happened during the flood. We should be talking about a global disaster that was much worse than just a flood.