Accumulation of uranium, transuranium and fission products on stainless steel surfaces II. Sorption studies in a laboratory model system

• Published in: Journal of radioanalytical and nuclear chemistry 2011-06, Vol.288 (3), p.943-954
• Main Authors: Kádár, P., Varga, K., Baja, B., Németh, Z., Vajda, N., Stefánka, Zs, Kövér, L., Cserny, I., Tóth, J., Pintér, T., Schunk, J.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Diagnostic Radiology; Hadrons; Heavy Ions; Inorganic Chemistry; Mathematical models; Monolayers; Nuclear Chemistry; Nuclear Physics; Physical Chemistry; Sorption; Stainless steels; Surface chemistry; Tubes; Uranium; X-ray photoelectron spectroscopy
• ISSN: 0236-5731; 1588-2780
• DOI: 10.1007/s10967-011-1038-6

Within the frame of a joint project, the accumulation of the uranium and transuranium (TRU) species on some structural materials used at Soviet made VVER-type pressurized water reactors (such as heat exchanger tube of steam generators and stainless steel canister material) has been studied. The experiments were carried out in a laboratory model system. During the sorption studies, boric acid coolants provided by the Paks Nuclear Power Plant (Paks NPP) were circulated for a period of 30 h. Solution and tube samples obtained in the course of above experiments were analyzed by independent methods (α- and γ-spectrometry, ICP-MS, SEM-EDX, voltammetry and XPS). The experimental results reveal that: (i) the surface excess of the TRU nuclides studied is extremely low (less than 1% of a monolayer coverage); (ii) the surface excess of uranium species measured on the SG tube surfaces is significantly higher, after 30 h sorption period (Γ sample  = 1.0 μg cm −2 U ≅ 3.7 × 10 −9  mol cm −2  UO 2 ) exceeds a monolayer coverage; (iii) the mechanistic features of the contamination processes (specific or non-specific adsorption, deposition of colloidal and/or disperse particles) depend decisively upon the nature of the studied radionuclides and the chemical structure and composition of the oxide layer formed on stainless steel surfaces.