REPRODUCIBILITY OF IMP MEASUREMENTS DOE/ERSP TECH NOTE NO. 21.0 DATED: 19 February 1980 AUTHOR: Joel Jobst, EG&G, Inc. Raphael J. Jaffe, EG&G, Inc. The determination of specific concentrations of transuranic elements in large quantities of soil is subject to errors and uncertainties. One such uncertainty is attributed to IMP measurements of the specific concentration of 24lam, which are subject to both systematic variations and counting statistics. A simple experiment has been conducted in order to estimate the IMP error. IMP l, equipped with detector 483, was driven to stake 3-N-0.5 on Pearl. This was a "total lift" area; that is, all brush and surface soi] had been removed to a depth of several inches. The terrain was relatively flat, the soil rather moist because a rain had soaked the area in early morning hours. A 300-second calibration was done with the standard EG&G 900-second measurements were made of 3-N-0.5. calibration source. Then eight consecutive A noon calibration was made and nine more measurements were obtained at 3-N-0.5; finally an evening calibration was made at the close of the day's work. The 17 measurements of 2414m and !8%Cs obtained are plotted in Figure B-21-1 in the order in which they were obtained. These data, and the three calibration measurements, suggest that no systematic drift occurred during the day. For the calibrations, the 24l am photopeak concentrations were 620.5 + 66.4, 604.1 + 64.7 and 609.6 + 65.3 pCi/g. The measured 24. am and “Cs concentrations obtained for location 3-N-0.5 are shown in Table B-21-1. Run 241 Am (pCi/g) 137Cs (pCi/g) 632 633 8.1 + 1.4 7.7 + 1.3 9.6 + 1.3 9.6 + 1.3 634 8.4 + 1.4 9.5 + 1.3 635 7.6 + 1.3 9.9 + 1.3 636 637 7.7 + 1.3 8.2 + 1.4 10.3 + 1.4 10.1 + 1.3 638 639 8.3 + 1.4 7.9 + 1.3 10.0 + 1.3 9.7 + 1.3 641 7.9 + 1.3 10.2 + 1.4 642 8.3 + 1.4 9.5 + 1.3 643 644 645 9.0 + 1.4 7.8 + 1.3 7.8 + 1.3 9.5 + 1.3 10.1 + 1.3 10.2 + 1.4 646 7.7 + 1.3 9.8 + 1.3 647 648 649 8.2 + 1.4 8.2 + 1.4 8.9 + 1.4 10.5 + 1.4 B-2]-1 10.0 + 1.3 10.2 + 1.4 a TABLE B-21-1. AMERICIUM AND CESIUM REPEAT MEASUREMENTS