DEVELOPMENT OF HIGHLY SENSITIVE TECHNIQUES FOR DETERMINATION OF CONCENTRATIONS OF FISSION MATERIALS IN WATER MEDIA USING THIN-LAYER INORGANIC SORBENTS AND PLASTIC TRACK DETECTORS

A technique for determining the uranium concentration in the VVER-1000 primary coolant and natural fresh water was developed. Thin-layer ino rganic sorbents based on Ti and Ce hydroxides (thickness being tens of mug cm-2) were used for increasing the uranium concentration. After e xposure in the experimental solution, thin-layer inorganic sorbents we re irradiated by thermal neutrons when positioned in close contact wit h plastic track detectors; the latter were then etched electrochemical ly. A Lavsan film, 180 mum thick, was used as a detector for fission f ragments. Detection sensitivity for uranium in ammonia-boron-potassium solution and distillate is a hundred or a thousand times higher than for the case of the track detector irradiated by neutrons directly in the solution. A detection limit for uranium in solutions is no worse t han 3 x 10(-12) g cm-3. It is defined, mainly, by a natural contaminat ion of the sorbent by uranium. High sensitivity, a low detection limit , and simplicity of the technique in practice make it feasible for sol ving the problems of nuclear reactor radiation safety, radio-ecology a nd other research fields.