Detonating solid plastic bonded explosives (PBX) formulated with the insensitive molecule triaminotrinitrobenzene (TATB) exhibit measurable reaction zone lengths, curved shock fronts, and regions of failing chemical reaction at abrupt changes in the charge geometry. A recent set of "hockey puck" experiments measured the breakout times of diverging detonation waves at ambient temperature LX-17 (92.5% TATB plus 7.5% Kel-F binder) and the breakout times at the lower surfaces of 15 mm thick LX-17 discs placed below the detonator-booster plane. The LX-17 detonation waves in these discs grow outward from the initial wave leaving regions of unreacted or partially reacted TATB in the corners of these charges. This new experimental data is accurately simulated for the first time using the Ignition and Growth reactive flow model for LX-17, which is normalized to detonation reaction zone, failure diameter and diverging detonation data. A pressure-cubed dependence for the main growth of reaction rate yields excellent agreement with experiment, while a pressure-squared rate diverges too quickly and a pressure-quadrupled rate diverges too slowly into the LX-17 below the booster equatorial plane.