Chapter 5
Metallic Technetium, Corrosion,
Technetium Alloys and Its Behavior
in Spent Nuclear Fuel
Electrochemical studies on the technetium as a radioactive waste component focus
on several aspects related to the waste immobilization and recycling, including:
(a) Tc reactions in nitric acid solutions;
(b) redox interactions of the technetium with other elements, such as actinides, as
well as its catalytic effect on the decomposition of hydrazine and other reducing
agents;
(c) Tc chemistry in alkaline aqueous solutions of high ionic strength used for the
radioactive waste disposal;
(d) separation of the technetium from other elements in non-aqueous systems.
The fission process generates numerous isotopes (stable and radioactive) of
various elements that are present in the nuclear fuel pellets as a contamination.
Based on their different chemical properties, these elements are often classified into
four groups (Kleykamp 1985a):
1. fission gases and other volatile fission products (e.g. Xe, Kr, I)
2. fission products forming oxide precipitates (e.g. Rb, Cs, Zr, Nb, Mo)
3. fission products dissolved in the fuel matrix (Sr, Nb, rare elements like Y, La,
Ce, Pr, Pm, Sm)
4. fission products forming metallic precipitates (e.g. Tc, Rh, Ru, Pd, Ag, Cd, In,
Sn, Mo).
Some of these elements may belong to more than one group. For example, molybdenum can form both metallic precipitates and oxide forms, while relatively volatile
tellurium exists as oxides, cocreates metallic precipitates and can be dissolved in the
fuel matrix. The tendency to the formation of oxides of selected elements present
in the spent nuclear fuel (SNF) is presented by the Ellingham diagram (Kleykamp
1985a), which shows lines of coexistence of a metal and its oxide as a function of
temperature. As an example of a chemical equilibrium of reactions of the fission
products, one may recall the technetium–technetium oxide system (5.1).
© Springer Nature Switzerland AG 2021
M. Chotkowski and A. Czerwi´ nski, Electrochemistry of Technetium,
Monographs in Electrochemistry, https://doi.org/10.1007/978-3-030-62863-5_5
109
Metallic Technetium, Corrosion,
Technetium Alloys and Its Behavior
in Spent Nuclear Fuel
Electrochemical studies on the technetium as a radioactive waste component focus
on several aspects related to the waste immobilization and recycling, including:
(a) Tc reactions in nitric acid solutions;
(b) redox interactions of the technetium with other elements, such as actinides, as
well as its catalytic effect on the decomposition of hydrazine and other reducing
agents;
(c) Tc chemistry in alkaline aqueous solutions of high ionic strength used for the
radioactive waste disposal;
(d) separation of the technetium from other elements in non-aqueous systems.
The fission process generates numerous isotopes (stable and radioactive) of
various elements that are present in the nuclear fuel pellets as a contamination.
Based on their different chemical properties, these elements are often classified into
four groups (Kleykamp 1985a):
1. fission gases and other volatile fission products (e.g. Xe, Kr, I)
2. fission products forming oxide precipitates (e.g. Rb, Cs, Zr, Nb, Mo)
3. fission products dissolved in the fuel matrix (Sr, Nb, rare elements like Y, La,
Ce, Pr, Pm, Sm)
4. fission products forming metallic precipitates (e.g. Tc, Rh, Ru, Pd, Ag, Cd, In,
Sn, Mo).
Some of these elements may belong to more than one group. For example, molybdenum can form both metallic precipitates and oxide forms, while relatively volatile
tellurium exists as oxides, cocreates metallic precipitates and can be dissolved in the
fuel matrix. The tendency to the formation of oxides of selected elements present
in the spent nuclear fuel (SNF) is presented by the Ellingham diagram (Kleykamp
1985a), which shows lines of coexistence of a metal and its oxide as a function of
temperature. As an example of a chemical equilibrium of reactions of the fission
products, one may recall the technetium–technetium oxide system (5.1).
© Springer Nature Switzerland AG 2021
M. Chotkowski and A. Czerwi´ nski, Electrochemistry of Technetium,
Monographs in Electrochemistry, https://doi.org/10.1007/978-3-030-62863-5_5
109