Initiation of ignition

Fig. 11.21 shows the results of TG and DTA measurements on mixtures of AP particles and catalysts. The endothermic peak observed at 513 K is caused by the crystal structure transformation of AP from orthorhombic to cubic. A two-stage exothermic decomposition occurs in the range 573-720 K. The decomposition of the AP is seen to be drastically accelerated by the addition of catocene. The exothermic peak accompanied by mass loss occurs before the AP crystal transformation. Although the AP is sensitized by the addition of carborane, no effect is seen on the AP decomposition. The results indicate that carborane acts as a fuel component in the gas phase but does not catalyze the decomposition of AP. Thus, the critical friction energy is lowered due to the increased reaction rate in the gas phase. The results imply that the initiation of ignition by friction is caused by the ignition of the gaseous products of the AP pyrolants.PI... 

In addition, there are a few more impact machines which are more relevant for the study of mechanism of initiation of ignition or explosion of HEMs on impact rather than their impact sensitivity. A lot of research in this direction has been carried out at the Cavendish Laboratory, Cambridge University, UK by Bowden, Yoffe, Field and their coworkers [53-59]. 

Autoignition Temperature (AIT) The auto ignition temperature of a substanee, whether solid, liquid, or gaseous, is the minimum temperature required to initiate or eause self-sustained eombustion, in air, with no other souree of ignition. 

Minimum Ignition Energy (MIE) Initiation of flame propagation in a combustible mixture requires an ignition source of adequate energy and duration to overcome heat losses to the cooler surrounding material. Dust and vapor... 

Considering the relatively small, controlled amount of com-husfihles in an LWR, it is surprising Jiiit fiiL S at nuclear power plants. should be important. The first incident to attract attention was the fire in the San Onofre cable trays (FRPJ). This was followed by spontiiiieous combustion of uncured polyurethane foam in the cable seals at Peach Bottom 1 (1971). The incident at Browns Ferry in 1975 was similar, except that a candle ignited the polyurethane foam. These events showed the effectiveness of fire as an initiator of multiple system failures -... 

According to Giesbrecht et al. (1981), there was a delay of 10 to 25 seconds between the moment of the initial large release and the moment of ignition. The explosion must have been very violent in view of the extensive structural damage to the plant. The high death toll was due to the high population density in the vicinity of the point of release. 

Hoff (1983) studied the effect of igniting natural gas after a simulated pipeline rupture by firing a bullet into the gas mixture. The tests were on a 10-cm diameter pipeline operating at an initial pressure of 60 bar and a gas throughput of 400,000 mVday. The openings created in the pipeline simulated full-bore ruptures. Maximum flame speeds of approximately 15 m/s, and maximum overpressures of 1.5 mbar were measured at a distance of 50 m. 

Whereas currently most studies deal with azides, a similar effort devoted to other metal salts such as nitrates and chlorates would be an important step toward understanding electrical initiation of pyrotechnics, and conversely to making possible safe, non-expl igniters. For instance, a study by Maycock (Ref 4) shows that those azides, perchlorates, and nitrates in which the solid state shows absorption on the long wavelength side of the anionic excitation band in soln, are the most unstable members of the respective series. Consequently, there is a direct relationship between the absorption spectra of pyrotechnic oxidizers and their respective sensitivities... 

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