120 exposure period for background determination. The background 0 Nal scintillator response — uR/h exposure was essentially ail 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 100 90 80 70 measurements so that the results represent only the terrestrial radiation exposure rates. 0 We found that sunlight had a negligible “effect on this packaging arrangement. Fig. 2. The correspondence between the results obtained with the Nal 0 10 20 30 40 50 60 70 80 lon chamber response — uR/h Comparison of responses of the Nal scintillator and the pressurized ion chamber. scintillator and the pressurized linear, deviates more markedly from ion chamber is presented in Fig. 2. the 1:1 relationship. The ion chamber readings have been . The TLD results indicated that 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 Nal scintilla- This is consistent with similar tor overresponded because of its studies made at Enewetak Ato11+ and nonlinear energy characteristics. with environmental monitoring per- The discontinuity at about 30 UuR/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. the CaF, enhanced low-energy response On the This is reasonable based on scintillation instrument's low and the predominance of 1376. 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