exposure period for background The background exposure was essentially all contributed by cosmic radiation during the 3-month exposure period and during the aircraft flight to LLL. Additional TLD's were stored on the periphery of the lead pig to identify possible inadvertent exposures. The average background exposure for the two types of TLD's was subtracted from all field Nal scintillator response — uR/h determination. measurements so that the results represent only the terrestrial radiation exposure rates. o We found that sunlight had a negligible effect on this packaging arrangement. Fig. ! L l ! Comparison of responses of the Nal scintillator and the 2. pressurized ion chamber. results obtained with the Nal linear, deviates more markedly from scintillator and the pressurized ion chamber is presented in Fig. 2. the L:l relationship. The TLD results indicated that The ion chamber readings have been the cosmic-ray contribution at that latitude. i lon chamber response — uR/h The correspondence between the reduced by 3.3 uR/h, | 10 20 30 40 50 60 70 80 The the CaF, TLD's overresponded by 2 approximately 214 relative to the Lif. figure shows that the Nal seintilla- This is consistent with similar tor overresponded because of its studies made at Enewetak Atoll and nonlinear energy characteristics. with environmental monitoring per- The discontinuity at about 30 UR/h formed by LLL in the U.S. occurs at a range switching point response varies with energy and this on the scintillator. ratio (1.21) corresponds to an Three locations The over- were measured on both Low and high average gamma energy of about 500 range, and those results are keV. shown in Solid On the circles. This is reasonable based on the Ca¥, 2 enhanced low-energy response 13 scintillation instrument's low and the predominance of range of 0 to 30 uR/h, a correspondence activities distributed in the soil. near 1:1 is observed. the correspondence, though as JUL Go 08 aera range, On the higher To assess “os the beta contribution to the Lil’ exposure rates, various