Constraint-Conditioned Closure Analysis of the May 2026 Orange County Methyl Methacrylate Storage Tank Incident

On May 21, 2026, a 34,000-gallon storage tank containing methyl methacrylate (MMA) at the GKN Aerospace facility in Garden Grove, California, entered a self-reinforcing thermal runaway event associated with exothermic polymerization. The incident triggered mass evacuations, emergency declarations, and ongoing investigations. This paper applies the framework of constraint-conditioned closure (Dominik, 2026) to interpret the event as the stabilization of a runaway reaction pathway under degraded storage constraints. Using publicly available timeline data and established MMA polymerization behavior, we map four closure viability factors — intermediate persistence (I), propagation continuity (Q), dissipative resistance (D), and final-state stabilization (B) — onto the observed progression of the incident. Particular attention is given to the roles of MEHQ inhibitor depletion and the Trommsdorff–Norrish auto acceleration effect in transitioning the system from constrained stability toward self-sustaining runaway behavior. A simplified phenomenological heat-balance model calibrated against public observations reproduces the approximate temporal progression of the event and demonstrates that modest reinforcement of inhibitor stability, cooling capacity, or mitigation accessibility would likely have prevented runaway stabilization. The analysis is intended not as a definitive forensic reconstruction, but as a systems-level interpretive framework for understanding interacting constraint failures in large-volume reactive monomer storage.