Modeling heat transfer and kinetics in a PETN RP-1 exploding bridgewire detonator: an aging study

Exploding bridgewire (EBW) detonators have a wide range of applications. Teledyne RP-1 is a common commercial EBW, which has a low density pressing (initial pressing; IP) of pentaerythritol tetranitrate (PETN) explosive against the bridgewire. RP-1 detonators may be stored or experience environments that have the potential to induce electrical current across the bridgewire. These currents are likely low amplitude; however, these induced currents could result in localized heating of the PETN surrounding the bridgewire. This heating could act as a miniaturized cook-off experiment leading to unsafe conditions. Understanding how the miniaturized cook-off experiment affects the structure of the PETN within the EBW detonators is crucial to safety store and deploy EBW in environments that cause the localized heating. COMSOL Multiphysics simulations provide a platform to understand thermal degradation of processes such as these. In this study, we found that closed-circuit currents equal to or greater than 6.25 A will cause thermal runaway leading to ignition of the PETN, while currents of 6.125 A and 6 A will lead to thermal damage or aging of the PETN surrounding the bridgewire.