OFFICIAL showing that the reaction induction time increases with increasing inhibitor content in the explosive. Table 3: Isothermal Test - Time (hours) to Reaction at 55 oC Treatment Isothermal Sample 1 Isothermal Sample 2 0 units Inhibitor 0 0 1 unit Inhibitor 15 83 2 units inhibitor 188 526 The induction times varied between samples, as expected given the diversity of samples tested, but the trend of increasing induction time with increasing inhibitor was consistent. A dataset of inhibitor level vs time to reaction was accumulated for the most reactive samples tested over a year. Analysis of the dataset showed a consistent function across the samples analyzed. Given the significant difference in reactivity across sites and the potential for reactivity to change through the mining cycle, annual testing against at least 12 carefully selected samples from each site remains a key pillar to confirm products are suitable for the current and expected conditions. ARC and Modelling Results While the central focus was the isothermal test data, the ARC provided further evidence that supported the conclusions from the isothermal results. The first test that was conducted was a heat-wait-search (HWS) test, used to quickly screen different mixtures for thermal safety. The test starts at ambient temperature (25 oC) and cycles through 3 modes: 1) Heat mode ramps the temperature to the next preset increment, generally 5 oC 2) Wait modes allows some time for the sample temperature to equilibrate 3) Search mode tracks the sample temperature and if self-heating is detected, the instrument matches the sample temperature to prevent heat loss. Thermal runaway onset is the temperature where the self-heating rate exceeds 0.2 oC per minute. This is normally followed by an escalating temperature, termed thermal runaway. Figure 4 shows pure AN, AN + Pyrite and the reactive ground system of AN, Pyrite and naturally occurring weathering products exhibit progressively lower thermal runaway onset temperatures of 226 oC, 116 oC and 45 oC, respectively, demonstrating a significant reduction in thermal stability.
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