120 exposure period for background determination. 110 The background exposure was essentially all contributed by cosmic radiation during the 3-month exposure period and during Additional TLD's were stored on a | @ 2 the periphery of the lead pig to 6 identify possible inadvertent The average background exposure for the two types of TLD's 5 = 9 2 was subtracted from all field measurements so that the results represent only the terrestrial radiation exposure rates. 100 c the aircraft flight to LLL. exposures. > 0 We found that sunlight had a negligible effect on this packaging arrangement. t 0 | ! 40 50 60 | 70 80 lon chamber response — uR/h Fig. 2. Comparison of responses of the Nal scintillator and the The correspondence between the pressurized ion chamber. results obtained with the Nal scintillator and the pressurized 10 20 30 linear, deviates more markedly from ion chamber is presented in Fig. 2. the 1:1 relationship. The TLD results indicated that The ion chamber readings have been reduced by 3.3 uR/h, the cosmic-ray the CaF. TLD's overresponded by contribution at that latitude. approximately 21% relative to the LiF. The figure shows that the NaI scintilla- 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 circles. On the This is reasonable based on the CaF, 2 enhanced low-energy response 137... 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. range, On the higher the correspondence, though To assess the beta contribution to the LiF exposure rates, various