The spectral distribution of gamma radiation over the contaminated surface of Earth

The principle possibility of remote measuring the soil surface contamination according to the profile of energy spectrum of gamma radiation incident on a detector is studied basing on numerical calculations by the Monte Carlo method. 137Cs (Ej=0.66 MeV) is studied as an emitter. It is shown that the spectrum profile may reflect the size of the surface contaminated up to area of the order of 105 m2 in the case of uniform radioactivity distribution. The optimal height of detector location above Earth surface for ground-level measurements is 3-5 m, that for measurements from air is 50 m. The depth of radiator distribution in a soil influences most sharply the high-energy spectrum part and the initial energy peak first