Coral surface bursts

The results of correlation studies reported in Refs. 2, 4, and 7 indicated that the fractionation behavior of most fission products was remarkably similar for coral surface bursts, bursts on the surface of deep and shallow seawater, and bursts at altitudes sufficiently great to avoid entrainment of soil or water in the fireball and cloud. Furthermore, the correlations showed no clear-cut dependence on the explosive yield of the device. This report extends the treatment to a near-surface event on silicate soil. 

Transient Test Air Bursts Coral Surface Burst Silicate Surface Bursts... 

Samples from the following events were analyzed Castle Bravo, Castle Koon, Redwing LaCrosse, Redwing Zuni, Redwing Tewa, and from Johnie Boy. Koon samples from three different altitudes were analyzed but only one of the Johnie Boy samples (842L). Additional Johnie Boy samples have been analyzed by Russell (6). Details of all events and samples are reported elsewhere in this volume (5), except for LaCrosse and for Tewa. LaCrosse was a coral surface burst of about 40 kilotons whose cloud topped out at 12,000 meters. The sample analyzed (054) was collected at 6500 meters and at 2.6 hours after the event. 

The size distributions of the particles in cloud samples from three coral surface bursts and one silicate surface burst were determined by optical and electron microscopy. These distributions were approximately lognormal below about 3/x, but followed an inverse power law between 3 and ca. 60 or 70p. The exponent was not determined unequivocally, but it has a value between 3 and 4.5. Above 70fi the size frequency curve drops off rather sharply as a result of particles having been lost from the cloud by sedimentation. The effect of sedimentation was investigated theoretically. Correction factors to the size distribution were calculated as a function of particle size, and theoretical cutoff sizes were determined. The correction to the size frequency curve is less than 5% below about 70but it rises rather rapidly above this size. The corrections allow the correlation of the experimentally determined size distributions of the samples with those of the clouds, assuming cloud homogeneity. 

In this paper we report on the results of size distribution measurements of cloud samples from three coral surface bursts and one silicate surface burst and present the results of the calculations of the sedimentation correction. 

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