TABLE 3-4. CONVERSION FACTORS RELATING THE NET PHOTOPEAK COUNT RATE(CPS) FOR 1387CsTO SOURCE ACTIVITY IN THE SOIL AND TO EXTERNAL EXPOSURE RATE, AS A FUNCTION OF SOURCE DISTRIBUTION, FOR A DETECTOR HEIGHT OF 7.4 METERS. 137Cs Conversion Factors Average Activity in the Top z cm Relaxation Length sZ / External Exposure Rate at the l Meter Level P l/e (em) 5 Zz (em) (pCi/g) eps 0 5 13 8.2 15 25 40 60 4.1 2.6 1.6 1.1 10 10 0 10 3 10 15 25 40 7.9 6.3 5.2 3.7 2.5 3.6 3.7 1.7 0 5 10 15 8.8 7.9 6.4 3.6 29 3.4 4.3 40 60 3.3 eps 2.6 60 15 ( 2R/h) 3.1 2.2 SOIL SAMPLE MEASUREMENTS In April 1978, a method was devised to use the IMP for gamma counting soil samples. It was designed as a screening technique to classify samples with 241 am above or below 1.5 pCi/g. Samples above that level were transferred to the Radiation Counting Laboratory for accurate measurement. As the majority of soil samples were below the screening level, the IMP soil sample measurement technique greatly reduced the workload on the Radiation Lab, shortening the lag time in obtaining data. As confidence in IMP measurements grew, the technique was used with increasing frequency. The philosophy of DOE/ERSP Procedure No. 21 was maintained. Samples above a certain activity level were counted by the Radiation Lab and an additional 10 percent of the samples measured were counted by the Radiation Lab as a quality control check. About 1,000 samples were screened for the Aomon Crypt excision project, and about 1,100 for the northern islands subsurface sampling and excision program. For the latter project, having data available within hours after sample collection was invaluable, and allowed an iterative boundary definition method to be utilized. IMP sample screening also was effectively used for a number of special investigations such as: Kickapoo beach debris samples; Cactus crater lip soil sampling; and occasional samples suspected of being too high in activity to be allowed in the Radiation Lab soil preparation - counting facilities. Occasionally, debris was measured upon request of JTG to determine relative content of 24lam, 13%Cs, and 6%Co., 102