Production and Spatial Distribution of Nitric Oxide from Nuclear Explosions

Appendix 1 Production and Spatial Distribution of Nitric Oxide from Nuclear Explosions 

There have been numerous estimates [49—52, 72] of the yield of nitric oxide per megaton (Mt) of explosion energy, and these have been reviewed by Gilmore [72]. Nitric oxide is produced by heating and subsequent cooling of air in the interior of the fireball and in the shock wave. 

The spherical shock wave produces nitric oxide by heating air to temperatures above 2200 K. This air is subsequently cooled by rapid expansion and radiative emission, while the shock front moves out to heat more air. At a particular temperature the cooling rate becomes faster than the characteristic time constant for maintaining equilibrium between NO and air. For cooling times of seconds to milliseconds the NO concentration freezes at temperatures between 1700 and 2500 K, corresponding to NO concentrations of 0.3-2 %. Gilmore [72] estimates a yield of 0.8 x 10 NO molecules per Mt for this mechanism. 

The shock wave calculation of NO production does not take into account the fact that air within the fireball center contains approximately one-sixth of the initial explosion energy, having been heated by the radiative growth mechanism described earlier. This air cools on a time scale of several seconds by further radiative emission, entrainment of cold air, and by expansion as it rises to higher altitudes. These mechanisms are sufficiendy complex that one can only estimate upper and lower limits to the quantify of NO finally produced. 

A lower limit to total amount of NO finally produced may be obtained by assuming that aU of the shock-heated air is entrained into the fireball and again heated to a high enough temperature to reach equilibrium. This is possible since the 

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