For some time I’ve been using TNT as the explosive material for Samus’ power bombs, but I suspect that I’ve been doing this incorrectly all this time, simply because nuclear bombs use fissiles, material capable of sustaining a nuclear fission chain reaction. While the use of G. I. Taylor’s method, (R^5 ρ) / t^2  isn’t incorrect, the assumption that power bombs use TNT is. Indeed, TNT is one of the most common explosives, but for nuclear weapons? I don’t think so. That would be Uranium-235.
From UC Davis ChemWiki,  we are told that the amount of mass lost in the fission process is equal to 3.2 × 10^-11 J. We are then asked how much energy would be released if 1 gram of U-235 undergone fission. The equation for this is as follows:
(1.00 g. 235-U) × (1 mol 235-U/235 g. 235-U) × (6.022 × 10^23 atoms 235-U/1 mol 235-U) × (3.2 × 10^-11 J/1 atom 235-U)
This is equal to 8.2 ×10^10 J. We don’t know the volume of Samus’ power bombs, but that’s all right. The required critical mass for U-235 with a neutron reflector is 15 kg.  This is obviously more than 1 g., so with the aforementioned calculation, just how much energy would come from 15 kg. of U-235? A total of 1,230,025,531,914,893.62 J, or 293.98 kilotons of TNT. I’m sure some may take issue with this calculation, but even if only 2% of U-235 actually blew up like it happened with Little Boy (a different bomb of its own), that still leaves us with 5.88 kt of TNT.