GAMMA RADIATION FROM DEPOSITED FISSION PRODUCTS 237 angular distribution of the primary photons and the total dose rate expected per unit source concentration can then be calculated for infinitehalf-space geometry, using the best available decay schemes. The response of the detector in terms of estimated peak counts per unit flux is obtained in the laboratory as a function of angle by using standard monoenergetic gamma sources, and a simple calculation then provides a conversion factor from estimated peak counts to dose rate”! The second method of obtaining component dose rates is to relate the total detector response in bands bracketing the three peaks characterizing the major natural emitters by means of three simultaneous equations. This is similar to the technique used in many laboratory spectrometric analyses except that, instead of determining the coeffi- cients of these equations by calibration with standard sources, which is not practical for our case of an infinite-half-space geometry, we obtained them by applying regression analyses to a large number of spectra, using the dose-rate predictions from the absorption peak areas.’ This band method is more amenable to routine data-analysis procedures and also provides more precise individual dose-rate determinations, CALIBRATION VERIFICATION The analysis of spectra by these methods provides the type of in- formation shown in Table 1. The particular locations were chosen at random to demonstrate the consistency of our results over a wide range of natural, fallout, and cosmic dose rates. The consistency obtained is in fact the ultimate justification for our procedures. The column labeled “Spectrometer” is the total terrestrial gamma dose rate inferred from the spectra by dividing the total energy in the spectra between 0.15 and 3.4 Mev by an empirically determined conversion Table 1—-REPRESENTATIVE SURVEY RESULTS Dose rates, ur/hr Total gamma Natural gamma Fallout gamma Date Ion chamber Spectrometer K U_ Th 1 2 Cosmic ray Memphis, Apr. 1963 11.8 11.2 1.8 1.7 2.7 5.0 5.3 3.5 Lake Charles, Apr. 1963 8.4 8.6 0.7 0.9 1.9 5.2 5.0 3.4 Bonnydoon, Calif. Denver, Oct. 1962 Oct. 1962 Oct. 1963 13.6 12.8 16.3 13.4 12.7 15.4 8.5 7.7 4.0 2.2 2.5 2.5 1.9 1.5 8.7 1.8 12 0.6 0.9 1.0 0.6 4.0 4.0 6.3 5.3 1.0 1.3 0.4 2.9 2.6 3.6 12.7 14.9 3.8 3.5 3.0 1.1 2,1 1.5 5,0 5.2 4.8 2.9 3.5 2.8 4.1 1.7 3.6 3.5 3.6 Town Tenn. La. Colo, Clallam Bay, Wash. North Conway, N. H. Oct. 1962 Aug, 1962 Sept. 1963 May 1964 13.2 10.7 11.0