Series 3 spoilers for "Devil You Know"
The destruction on Netu was achieved by sending a Tok'ra supplied bomb to a sub-terrainean position before it blew, and Netu was only a moon, therefore by implication smaller than a planet.
| What is interesting is to think about the consequences of firing at the surface of a world full of naquada deposits. But well, this isn't relevant since the naquada needs to be part of the vessel's weapons in order to be accepted. |
We get this in S4's "Chain Reaction, and the effect is significant, even though it is effectively only trace naquadah in the soil, if I remember, and the naquadah certainly isn't part of the bomb...
Just for the record,
| What is interesting to note is that when Ra added naquada to the atomic bomb transported by O'Neil(l) on Abydos, and yet nothing apparent protruded from the device, which means that Ra was able to add only very little portions of naquada inside the bomb. |
The naqaudah WASN'T already in the bomb - you will recall that the whole final assault came to pass as Jack's team brought the naquadah into the base of the pyramid - since it went back outside with them (the team trapped outside hid behind it) there was no naquadah in the bomb when it transported.