As the planet collapses, the whole Lexylnian population gets evacuated, and head towards Musen.
The tacterians are easily able to detect this, And immedietly come down to help. They realize they should've gave the LSF more of a warning on how massive the plutonium explosion would be, They immedietly come down, And attempt to make up for it; Giving them basically all of the technology they have. Including mass materializers, Inter-galactic-cluster transport, and ask if they should build a planet-sized city in their system to escort the survivors too.
Soon after this, the core solidifies, And the magnetic field seases
The intial plutonium explosion triggers a chain reaction - The core basically explodes, The mantle above it sinks, Gelogic activity at the surface drastically increases as the crust sinks with the mantle, and all the explosion heats up the surface.
They hit the plutonium, gold, platinum, and silver rich core, But the plutonium instintly ignites, A huge explosion occures, the mine collapses, and nuclear fallout is in the area.