CRLR - LAT - THE QUALITY OF GAMMA RADIATION FROM AN EXTENDED SOURCE OF Tal62, Karl Eklund, P. E. Grant, S. S. Holland, and R. L. Liboff, 26 April 1955. CONFIDENTIAL-RESTRICTED DATA, Special Report (u) The object of this work was to determine the dose rate and the spectral energy distribution of gamma radiation above an extended plane source Tal82, (u) The differential number spectra, integral dose spectra, and the absolute dose rate are shown as measured on a contaminated area at Dugway Proving Ground and as determined by theoretical analysis. ( There is sufficient agreement between the results of the SpencerFano method and the experimental data to justify use of the theory in the analysis of RW contaminated fields. This theoretical attack ylelds, in the ideal case, spectral distribution for the number, energy, and dose as well as absolute determination of the dose rate. (u) For an extended source of tat82 | the per cent of the total dose due to photons with energies below 100 kev is negligible. Thus, since present military standard radiac instruments do not measure radiation energies below 80 kev, and are accurate to 5% to 104, it is evident that the limitations of these instruments are not detrimental to their use in the case of Tal82, (u) For an infinite plane source of telb2 scattered radiation constitutes approximately 20% of the total dose, and so mist be considered in determining the effects of such sources, (u) At 3 ft above a paiform plane source of Talé2 | the dose rate, D is given by: D = (59.6x10-*)S where D is in milliroentgens per hour and §S is the source strength in curies per square mile. This equation applies only if the above ideal conditions are fulfilled. Recently it has been observed that in the production of T_l 82 appreciable successive neutron capture occurs, making the determination of true source strength difficuit. In such a case, one would then not expect agreement between measured and calculated dose rates.