Radioactivity Trapped in Melt Produced by a Nuclear Explosion

An inventory of ¹³⁷Cs, ¹⁰⁶Ru, ¹²⁵Sb, ¹⁴⁴Ce, ¹⁵⁵Eu, ⁹⁰Sr, ³H, and assorted activation products in glass recovered in postshot cores from the Piledriver Event indicates that 60% of these fission products produced by the nuclear explosion are retained in the sampled glass. Chemical analyses of the major constituents of the glasses closely resemble those of the preshot rock except for the water content (which decreases) and conversion of original ferric iron to ferrous iron. Water in the glasses is close to the amount expected if quasiequilibrium existed at the time of quenching; however, the amount of tritium in water contained by the glass is considerably below anticipated amounts. Calculations indicate that cavity pressure (56 bars) was about half overburden pressure (121 bars) at the time water ceased to evolve from the cooling melt. Not unexpectedly, rubble in the chimney at horizons immediately above the shot point is enriched in volatile fission products relative to ¹⁴⁴Ce and shows heterogeneous distribution of radioactivity. Some evidence of devitrification in the glasses was noted, but high-pressure polymorphs of original mineral constituents were not recognized.