A scintillator is set in tube or hole in soil (Fig. 1,3) and it measures the counting rate profile c(z) of gamma-active nuclide photopeak. An inversion calculation, from this profile, is presented to determine the activity profile q(z) of radioactive nuclide in soil. The stratified or plane symmetry of the nuclide distribution is assumed, so that q and c depend only on z. In inversion calculation the q(z) is determined by iteration with the integral c(z) velence integral from x=0 to infinity of K(z',z)q(z')dz' so long that fitting is the best. The kernel K(z', z) is in [1]. ~(137)Cs activity profiles, from the photo-peak (662 keV) profiles, are determined by using a 1" NaI(Tl) scintillator in tubes, which were in soils before Chernobyl, or in holes in peat. I started 1986 and the first result is in Fig. 3. In spring of 1987 STUK took my project concerning the cesium activities on swimming shores. I determined surface activities (the arrangement a of Fig. 2) in southern Finland, and also there in the tubes of the ground- and soil water sites of Hydrological office (today in Environmental Institute) I then used the arrangement b of the equipment in Fig. 2 for cesium profile determinations. ~(134)Cs was also in interests. Its disturbing effects in ~(137)Cs determinations were tried to eliminate. In profile calculations the density profile rho(z) ought to be considered. Its increase with water content can be determined by neutron moisture measurement or in other ways. In calculations I tried to consider the tube walls and snow on the ground. The Rayleigh scatterings (Fig. 4) have so small scattering angles that they cause no troubles. Polarization has effects in the both scatterings. The differential Klein-Nishina scattering cross section can be necessary to be multiplied by S(x,Z) [2], where x velence sin(theta/2)/lambda; lambda is the initial photon wave length, theta scattering angle and Z atomic number. S E [0,1] and S(0,Z) velence 0 for all elements. The compilation of S(x,Z) in [3] I have used. The instrument in Fig. 2 is not so pulse height stabilized as should be. In future measurements the peat density instrument [4,5] I shall use, because it has the good stabilisation, from Nucletronics.
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