It's certainly more than enough for a global economic breakdown, since the idea is to give the enginneers time to put the reactor and hot fuel rods into a longer term stable state. For some designs (undamaged) this simply involves lowering a neutron shield that waits inside the reactor, and the heat level will slowly reduce to the point that additional water supply is no longer pressing. For some designs this actually requires that some (all?) of the hot fuel be removed by very well trained operators and placed into open storage pools, with or without neutron shielding between the rods. Most of the open storage pools are not designed to collect rainwater for level maintaince, but do you really think that should it become obvious, the engineers can't arrange such things for most or all of the power plants?
In the longer term we've got to stop encasing the fuel and fission products inside a flammable metal (zirconium) and surrounding them with a ready source of hydrogen (water). Commercial reactors and the waste they produce really are a disaster waiting to happen.
Switch to a liquid fuel design using stable fluoride salts as a medium and you get fuel and waste that requires higher temperatures than decay heat can produce to stay in liquid form. In the event of an accident the entire mass cools and freezes into an inert solid instead of catching on fire.