Application of various laboratory assay techniques to the verification of the comprehensive nuclear test ban treaty. Analyses of samples from Kuwait and from AFTAC

摘要

Various laboratory assay techniques were applied to two particulate air filters from Kuwait and to one filter salted artificially. The monitoring system, run by the PIDC in Arlington, identified (sup 137)Cs but no (sup 134)Cs in the air samples. Long-term counting using a 100 % HPGe detector in laboratory did not reveal (sup 134)Cs either. Upper limit of the activity ratio (sup 134)Cs/(sup 137)Cs was estimated to be 0.015 which is below the expected average value of the Chernobyl fall-out (0.025). This finding may indicate that the Cs in the sample has other origin than Chernobyl fall-out. Radiochemical methods to purify Cs from the bulk material were investigated. However, because of low yield, the preliminary efforts failed to improve detection limits. The high-resolution gamma-spectrometry of the artificial sample (AFTAC) identified the following man-made radionuclides: (sup 95)Zr/(sup 95)Nb, (sup 103)Ru, (sup 137)Cs, (sup 140)Ba/(sup 140)La, (sup 141)Ce, (sup 147)Nd. (sup 241)Am was found in alpha spectrometry. The isotope ratios indicate that the sample is produced early in November 1996. The presence of Am shows that the material is most likely irradiated high-burnup uranium or plutonium containing transuranium elements before irradiation. Advantages of mass spectrometry were studied and the preliminary results are very promising. However, a separate programme for sample preparation should be launched. (orig.). 5 refs.