The combination of electrochemical studies with radiotracer methods can help solve many electrochemical and corrosion problems, such as the corrosion of the structural material of nuclear power plants and the contamination and decontamina­tion of the corrosion products.

Important factors of contamination and decontamination are the sorption pro­cesses which, as discussed previously, can be well studied by radiotracer methods. In such studies, the radioactivity of the solution and/or the solid phase, including the electrodes in the electrochemical studies, can be measured. The radioactivity of the surface is proportional to the surface excess concentration of the sorbed spe­cies. The measurements frequently can be obtained by stopping the process and
measuring the activities after sampling. In addition, the processes can also be stud­ied in situ. The in situ methods are based on the thin-layer principle. This means that the self-absorption of beta particles with low and medium energy, as well as gamma- or X-ray radiation below 20 keV energy, is so high that the detectors can observe the radiation of only a thin liquid layer. If the solution phase is eliminated from the surface of the solid (electrode), the radioactivity of the sorbed species can be determined. It can be achieved in three ways:

1. In the foil method, the detector and the solution of the labeled adsorbate is separated by the adsorbent deposited on a thin foil (or the adsorbent itself is the foil).

2. In the thin-layer method, the solution is continuously circulated in a thin layer (about 0.5 mm) between the detector and the electrode.

3. In the so-called electrode sinking method, which is the combination of the two previous methods, radioactivity is measured alternatively in the two positions of the electrode. Sinking to the bottom where the background is very low, the surface excess concentration is measured, while in a position higher than the range of the beta radiation, the radioactiv­ity of the solution is measured.

Further Reading

Atkins, P. W. (1998). Physical Chemistry. 6th edition. Oxford University Press, Oxford.

Bartha, L. (1967). Observation of recrystallization of tin by autoradiography. J. Appl. Radiat. Isot. 18:789-790.

Crank, J. (1979). The Mathematics of Diffusion. Clarendon Press, Oxford.

Elektrochemie, Z. Berichte der Bunsengesellschaft fur physikalische Chemie. 56:380-386. http://onlinelibrary. wiley. com/doi/dx. doi. org/10.1002/bbpc.19520560427/abstract. May 3, 2010.

Gerischer, H. Vielstich, W. (1952). Untersuchungen mit radioaktiven Indikatoren uber Austausch — und Diffusionsvorgange an Silberelektroden.

Haissinsky, M. (1964). Nuclear Chemistry and its Applications. Addison-Wesley, Reading, MA.

Hoffman, R. E. and Turnbull, D. (1951). Lattice and grain boundary self-diffusion in silver. J. Appl. Phys. 22:634-639.

Imre, L. (1933). Grenzflachengleichgewichte und innere Gleichgewichte in heterogenen Systemen. Teil I. Z. Phys. Chem. Abt. A 164:343-363.

Imre, L. (1933). Zur Kinetik der Oberflachenvorgange an Kristallgittern. II. Die Elementar — prozesse bei der Ausbildung einer aus mehreren Komponenten bestehenden Grenzschicht. Z. Phys. Chem. Abt. A 164:327-342.

Imre, L. (1942). Uber die Anwendbarkeit der radioaktiven Indikatormethode zur Bestimmung Der Oberflache fester Korper I. Kolloid Z. 99:147-157.

Imre, L. (1944). Uber die Anwendbarkeit der radioaktiven Indikatormethode zur Bestimmung der Oberflache fester Korper II. Kolloid Z. 106:39-46.

Kazarinov, V. E. and Andreev, V. N. (1984). Tracer methods in electrochemical studies. In: Comprehensive Treatise of Electrochemistry (eds. Yeager, E., Bockris, J. O’M., Conway, B. E., Sarangapani, S.). Plenum Press, New York, NY, London, pp. 393-443.

Konya, J. (1977). Study of surface reactions of the Fe/Fe heterogeneous isotope-exchange system with a radioactive indicator (59Fe), part I. Determination of iron exchange cur­rent. J. Electroanal. Chem. 84:83-91.

Konya, J. and Baba, A. (1980). Study of surface reactions of the Fe/Fe heterogeneous iso­tope-exchange system with a radioactive indicator (59Fe), part II. Rates of anodic and cathodic part-processes at corrosion potential. J. Electroanal. Chem. 109:125—139.

Nagy, N. M. and Konya, J. (2005). The relations between the origin and some basic physical and chemical properties of bentonite rocks illustrating on the example of Sarmatian ben­tonite site at Sajobabony (HU). Appl. Clay Sci. 28:257—267.

Nagy, N. M. and Konya, J. (2009). Interfacial chemistry of rocks and soils. Taylor & Francis, Boca Raton, FL.

Philibert, J. (1991). Atom Movements. Diffusion and Mass Transport in Solids. Les Editions de Physique, Paris.

Sheppard, C. W. (1948). The theory of the study of transfers within a multi-compartment sys­tem using isotopic tracers. J. Appl. Phys. 19:70—76.

Solomon, A. K. (1949). Equations for tracer experiments. J. Clin. Invest. 28:1297—1307. < http://www. ncbi. nlm. nih. gov/pmc/articles/PMC439688/pdf/jcinvest00400-0051.pdf > (accessed 25.03.12.)

Varga, K., Hirschberg, G., Baradlai, P. and Nagy, M. (2001). Combined application of radio­chemical and electrochemical methods for the investigation of solid/liquid interfaces. In: Surface and Colloid Science (ed. Matijevic, E.), vol. 16. Plenum Press, New York, NY, pp. 341—393.

Varga, K. (2004). The role of interfacial phenomena in the contamination and decontamina­tion of nuclear reactors. In: Radiotracer Studies of Interfaces, Interface Science and Technology (ed. Horanyi, G.), vol. 3. Elsevier B. V., Amsterdam, pp. 313—358.