Characterizing major and trace element concentrations, and radioactivity in bulk glass samples from the trinity atomic test

Abstract

Glass fragments (16 green glasses and 2 red glasses) were handpicked from crushed Trinitite. X-ray diffraction studies revealed that these samples were essentially pure glass with the exception of minor amounts (less than 4 wt%) of quartz (which acts as a diluent) in some samples. The concentrations of 45 elements in the Trinity glasses were determined using Instrumental Neutron Activation Analysis. Plutonium-239 concentrations were determined by measuring the activity of fission products produced during thermal neutron irradiation of the glasses. The activity of various radionuclides was determined by gamma ray spectroscopy. Elemental concentrations were also determined for 12 arkosic sand samples from the Trinity site. The Trinity glasses are essentially a mixture of arkosic sand, radionuclides and elements from the atomic device, and elements associated with the structures in the immediate vicinity of the test site. Comparison of glass chemistry to the arkosic sand chemistry allows an assessment to be made of the addition and removal of various elements during glass formation.

Ba-133 and Cs-137 are linearly related to the Pu-239 + U-235_device content of the glasses. Barium (Baratrol) was used in the device and Ba-133 activity has a positive y-intercept, which suggests that some of the Ba-133 activity may be due to activation of Ba in the arkosic sands. For Cs-137, the y-intercept is negative which suggests a depletion of Cs-137 in the glasses. The present-day Am-241 activity shows a linear relationship with Pu-239 activity (r² = 0.99). Am-241 is derived via beta decay of Pu-241, and the Pu-241/Pu-239 activity ratio can be used to distinguish different Pu sources. For the Trinity glasses, this ratio is 0.70 ± 0.16.

Relative to the arkosic sand elemental concentrations, the glasses are depleted in As, Br, Cs, Sb, Se, and Zn presumably because of their relatively high volatility. The depletion of several other elements (Co, Ir, Mg, Ni, V, W) may be due to their removal by metallic droplets during glass formation. Relative enrichment of U, Mo, Ti, and Ba is due to addition of these elements from the atomic device and associated structures.

The residual activity of Eu-152 is used to determine the distance of individual glass samples from ground zero. Most of the samples fall between 40 and 50 m (near the edge of the glass free crater formed during the atomic explosion). Similar results were obtained for a different batch of samples using residual Co-60 activity. The inference is that the material that comprises the bulk of the glass originated close to ground zero and was distributed across the site as an ejection blanket. Material from the atomic bomb was added during the formation of this ejection blanket.