What could have sped up decay rates? The following comment by Keith Wanser, a creationist physicist, quoted in Creation Ex Nihilo 21(4) p. 40 is significant: Actually, it turns out that when you get the nucleus "excited", decay is going to be much quicker, making things look vastly "older". People have been talking recently about magnetic stars giving off big bursts of gamma rays; there are all sorts of ways that radiometric "clocks" could have been reset catastrophically, during the Flood, for example.
In fact, when the nucleus gets excited, it takes time for it to settle down.  This means that rates of decay may have been faster for some time after the Flood.