Calibration Two soil samples, in which 241Am concentrations had been previously determined in the laboratory, were taken to Ursula and several measurements taken with the samples in place. The samples were removed and reinserted into the holder each time a count was taken. The results are given in Table B-6-1. The soil samples used in the calibration were composed of dry soil, previously calibrated in the EIC laboratory. For a simple estimate of the uncertainty of the results, we assume + 1 pCi/g 241.4m or + 15%, whichever is greater, assuming a 5 minute count and low background. If weight and moisture eontent are not known, the uncertainty increases. After many samples have been counted by the IMP and processed by lab analysis, it is intended that an addendum in this Tech Note be prepared, summarizing the comparisons.* Testing Soil samples were counted at the Cape Mixan site and the IMP shed as well as truck samples at Kickapoo. The system seems to work adequately as designed. The following are observations, suggestions and recommendations in regard to applications of the technique: 1. Soil samples should be counted in an area where the 137Cs and 60Colevels are low. At the Cape Mixan area levels were high producing background counts under the 241Am peak of 400 counts. Background at the IMP shedis about 20 counts in 5 minutes, 2. Dry soil in the petri dish must be estimated or measured. Currently, we are estimating 100 grams while we are waiting for a scale to be delivered. 3. To determine soil content above or below 400 pCi/g TRU for truck samples, a counting time of 150 seconds is adequate. TABLE B-6-1. CALIBRATION RESULTS OF IMP SOIL SAMPLE COUNTING SYSTEM IMP I, Detector 496 Soil Sample pCi Net Count IMP II, Detector 513 in 2414M Ratio Peak (5 min) pC i/count pCi 11.43 11.83 11.31 12.07 12.90 12.04 11.37 11.20 10.77 4,479 4,479 4,479 4,479 4,479 4,479 10,895 10,895 4,479 4,479 4,479 4,479 4,479 4,479 4,479 953 921 396 371 350 372 394 400 416 SoilSample Average = 11.66 + 0.63 Net Count in 2414m Ratio Peak (5 min) pCi count 426 446 512 486 456 436 Average = 9.77 + 0.67 *See Tech Note 6.1. B-6-2 10.51 10.04 8.75 9.22 9.82 10.27