The Astral Core Formulation has several requirements.
Aside from having the Celestial Fragment as a catalyst, he needed four other types of energy to create his Core.
There are many types of energy that he can use but since this can only be done once, he had to choose the best form of energy he'll use.
He previously asked Avalon to prepare all the necessary requirements. In the end, it actually changed his plan and created a better option for him.
Instead of using thermal energy, Avalon suggested using the unique core of his Lotus Mech Frame model. All Mech Frames of this model have Radiant Wave Spectrum Technology. In general terms, it was a powerful microwave radiation emitter. By activating it on its silver right arm, any enemy Mech Frame it touches would fry its electronics and heavily warp the frame itself, making the machine unsalvageable.
This technology was all thanks to the unique Ion-Sting Reactor it possesses.