The results of experimental determination of the forms of uranium and radionuclides Sr-90, Cs-137, Eu-154, Pu-238, Pu239+240, Am-241, and Cm-244 in the bottom sediments of the premises 001/3 of the "Shelter" object are presented. By the sequential extraction procedure, the following amounts are determined: water-soluble, exchange, carbonate, and acidsoluble forms of uranium, fission products (Sr-90, Cs-137, Eu-154), and transuranium elements (Pu-238, Pu239+240, Am-241, Cm-244) in the bottom sediments in the premises 001/3 on a mark of -2.60 m of auxiliary systems of the reactor compartment of the "Shelter" object. The concentration of uranium in the bottom sediments of room 001/3 is equal 3.1 +/- 0.5 g/kg. The specific activity of Sr-90 and Cs-137 in the bottom sediments is within the range of 6.108 - 1.109 Bq/kg, and Pu239+240 and Am-241 within the range of 6.105 - 8.106 Bq/kg. Radionuclides Sr-90, Cs-137, Eu-154, Pu-238, Pu239+240, Am-241, and Cm-244 in the bottom sediments are in different chemical forms that will define their different potential mobility. Uranium and Cs-137 in the bottom sediments of premises 001/3 mainly are in exchange forms. The amount of watersoluble forms of uranium and cesium is 1.5 - 3 %. The basic amount of Sr-90, more than 60 % is carbonate soluble in a weak acid at.. 4.8. More than 65 % of Pu-238 and Pu239+240 in the bottom sediments are in acid-soluble forms. The mobility of Eu-154, Am-241, and Cm-244 in the bottom sediments is much higher than that of plutonium; at pH 4.8 more than 40 % of Am-241 goes to a soluble state. The ratio between the activities of Cs-137/Sr-90, Sr-90/Pu239+240, Am-241/Pu239+240, and Cm-244/Pu239+240 in the bottom sediments considerably differ from the analogical relations of radionuclides in a fuel containing materials of the "Shelter" object.
