X-RAY PHOTOELECTRON STUDY OF SAMPLES CONTAINING REACTOR-FUEL FROM LAVA AND PRODUCTS GROWING ON IT WHICH FORMED AT CHERNOBYL NPP DUE TO THE ACCIDENT

X-Ray photoelectron studies have been carried out for the samples of f uel-containing mass (FCM) from ''lava'' and unidentified crystalline s ubstance - the ''new product'' grown on it that were formed due to the accident at the 4th Unit of chernobyl nuclear power plant (CNPP). The stoichiometric composition of FCM and ''new product'' samples is dete rmined. It has been discovered that FCM samples contain U(n+) ions of various oxidation degrees (0 less-than-or-equal-to n less-than-or-equa l-to 6), Zr(n+) and Si(n+) ions in these samples have oxidation degree s n less-than-or-equal-to 4. These FCM samples include ions of lower o xidation degrees (ZrO, SiO, U2O3, UCn etc.) in relation to more stable oxides (ZrO2, SiO2, UO2 etc.). It is found that the ''new product'' i s double salt of uranium Na4UO2(CO3)3 with impurities of Na2CO3, Na2SO 4. NaOH and H2O where atoms of Na are partially replaced by atoms of K . Using the characteristics of the fine structure of the XPS spectra t he uranium-ligand interatomic distance in the double salt has been est imated. It has been found that interatomic distance in the uranyl grou p R(U-L) = 0.174 nm and in axial plane of uranyl group R(U-L) = 0.239 - 0.260 nm. It has been shown that in the ''new product'' samples ther e is significantly more uranium (19 mass %) than in FCM samples (4 mas s%).