theory as to why the jumpgate in texas exploded
Cause of explosion: damaged or overloaded superconductor. When that superconductor blew, it'd have massive power. But I doubt enough to scatter heavy elements across an entire solar-system. But...
if it used a dual reactor, and one of them was a FUSION reactor, using H-fuel...
That would provide more than enough explosive force to scatter heavy elements.
Now the heavy elements themselves would come from the fuel of the second reactor- MOX.
The second reactor would be a fission reactor, probably a backup that only powers the tertiary functions of the jumpgate (like communication arrays, sensors, etc). Things that don't require the immense energy needed to conduct a space-warp fold.
But those reactors would hold refined MOX (read: nearly pure uranium) and thus provide the radioactive materials needed to create radiation fields across the solar system. The greatest concentrations of heavy elements would be closest to the explosion. The rest would be scattered further out.
If most of the fuel was undetonated, then it would have been scattered by the explosion. The scatterings would emit the radiation fields you've been picking up.