Seeing as the place was literally a ship graveyard, there were naturally defenses to stop this sort of thing. A massive portal surrounded the Corvette, like a secondary shield. Only it wasn't shielding the ship. It was there to absorb the massive amounts of firepower that detonated, and it dropped out the firepower a good distance away from Sovereign.
A large barrier surrounded the areas around the graveyard which had radiation within them. The barriers were coated with seals which absorbed the radiation. As the seals appeared as runes, attached to the barrier, pulsing with different auras, the barrier shut down and the runes scattered into different areas of the graveyard to serve as a new defense in case someone else came to the area.