5 Metallic Technetium, Corrosion, Technetium Alloys …
137
Although
99 Tc is a long-lived radioisotope, presence of high amounts of other
short lived FP may result in a radiolysis of the materials containing the spent nuclear
fuel. Therefore, an analysis of the electrochemical properties of technetium in nuclear
fuel reprocessing systems must include evaluation of influence of the radiolysis on
the stability of ionic forms of technetium. A detailed discussion of the radiolytic
processes that involve technetium species goes beyond the subject of this monograph. Here, we focus only on selected general information on radiolytic stability of
technetium(VII and IV) that are crucial for better understanding its redox chemistry.
A recent work of Ghalei et al. (2018) deals with characterization of radiolytic
decomposition of (NH 4 ) 2 TcCl 6 or TcO
−
4 in bicarbonate and carbonate solutions.
Under gamma irradiation the hexachlorotechnetates(IV) transform into carbonate
complexes of Tc(IV) with [Tc 2 (μ−O) 2 (CO 3 ) 4 (H 2 O) 4 ]
4− structure proposed by the
authors. The pertechnetates, on the other hand, are much more resistive to the radiolysis than the hexachlorotechnetates(IV) when the carbonates are present in the
solution.
Earlier works (e.g. Lukens et al. 2001, 2002) indicated that irradiation of the
pertechnetates in alkaline solutions in the presence of, e.g., nitrates leads to the
formation of Tc(IV). Also Sekine et al. (2004) reported generation of TcO 2 colloids in
solutions with pH > 2 and containing the pertechnetates which were subjected to irradiation with bremsstrahlung. Technetium with a low oxidation state, most likelyTc(I)
in f ac−[Tc(CO) 3 (gluconate)]
2− species, has been found in nuclear waste stored at
Hanford Reservation (Lukens et al. 2004). In turn, Denden et al. (Denden et al.
2013) observed that under alpha irradiation technetium, initially present in highly
acidic solutions as pertechnetates, transforms into oxopolymeric Tc(IV) species.
More information on the radiolysis of various technetium species and actinides in
alkaline solutions with various compositions can be found in WHC-EP-0901 report
(Pikaev et al. 1996).
References
Abdulaziz R, Brown LD, Inman D et al (2016) Predominance diagrams of spent nuclear fuel
materials in LiCl–KCl and NaCl–KCl molten salt eutectics. Int J Electrochem Sci 11:10417–
10435
Abdulaziz R (2016) Electrochemical reduction of metal oxides in molten salts for nuclear
reprocessing. PhD thesis, University College London, p 143
Adachi T, Ohnuki M, Yoshida N et al (1990) Dissolution study of spent PWR fuel: Dissolution
behavior and chemical properties of insoluble residues. J Nucl Mater 174:60–71
Aihara H, Arai Y, Shibata et al (2016) Characterisation og the insoluble sludge from the dissolution
of irradiated fast breeder reactor fuel. Proc Chem 21:279–284
Asakura T, Kim S-Y, Morita Y et al (2005) Study on electrolytic reduction of pertechnetate in nitric
acid solution for electrolytic extraction of rare metals for future reprocessing. J Nucl Radiochem
Sci 6(3):267–269
Bebko J (2011) Spectroelectrochemical investigations of pertechnetates reduction in the environment of sulfuric and nitric acid. Master thesis, University of Warsaw (in polish)
Box W (1968) Electrolyte for the electrodeposition of technetium. US Patent 3 374 157
137
Although
99 Tc is a long-lived radioisotope, presence of high amounts of other
short lived FP may result in a radiolysis of the materials containing the spent nuclear
fuel. Therefore, an analysis of the electrochemical properties of technetium in nuclear
fuel reprocessing systems must include evaluation of influence of the radiolysis on
the stability of ionic forms of technetium. A detailed discussion of the radiolytic
processes that involve technetium species goes beyond the subject of this monograph. Here, we focus only on selected general information on radiolytic stability of
technetium(VII and IV) that are crucial for better understanding its redox chemistry.
A recent work of Ghalei et al. (2018) deals with characterization of radiolytic
decomposition of (NH 4 ) 2 TcCl 6 or TcO
−
4 in bicarbonate and carbonate solutions.
Under gamma irradiation the hexachlorotechnetates(IV) transform into carbonate
complexes of Tc(IV) with [Tc 2 (μ−O) 2 (CO 3 ) 4 (H 2 O) 4 ]
4− structure proposed by the
authors. The pertechnetates, on the other hand, are much more resistive to the radiolysis than the hexachlorotechnetates(IV) when the carbonates are present in the
solution.
Earlier works (e.g. Lukens et al. 2001, 2002) indicated that irradiation of the
pertechnetates in alkaline solutions in the presence of, e.g., nitrates leads to the
formation of Tc(IV). Also Sekine et al. (2004) reported generation of TcO 2 colloids in
solutions with pH > 2 and containing the pertechnetates which were subjected to irradiation with bremsstrahlung. Technetium with a low oxidation state, most likelyTc(I)
in f ac−[Tc(CO) 3 (gluconate)]
2− species, has been found in nuclear waste stored at
Hanford Reservation (Lukens et al. 2004). In turn, Denden et al. (Denden et al.
2013) observed that under alpha irradiation technetium, initially present in highly
acidic solutions as pertechnetates, transforms into oxopolymeric Tc(IV) species.
More information on the radiolysis of various technetium species and actinides in
alkaline solutions with various compositions can be found in WHC-EP-0901 report
(Pikaev et al. 1996).
References
Abdulaziz R, Brown LD, Inman D et al (2016) Predominance diagrams of spent nuclear fuel
materials in LiCl–KCl and NaCl–KCl molten salt eutectics. Int J Electrochem Sci 11:10417–
10435
Abdulaziz R (2016) Electrochemical reduction of metal oxides in molten salts for nuclear
reprocessing. PhD thesis, University College London, p 143
Adachi T, Ohnuki M, Yoshida N et al (1990) Dissolution study of spent PWR fuel: Dissolution
behavior and chemical properties of insoluble residues. J Nucl Mater 174:60–71
Aihara H, Arai Y, Shibata et al (2016) Characterisation og the insoluble sludge from the dissolution
of irradiated fast breeder reactor fuel. Proc Chem 21:279–284
Asakura T, Kim S-Y, Morita Y et al (2005) Study on electrolytic reduction of pertechnetate in nitric
acid solution for electrolytic extraction of rare metals for future reprocessing. J Nucl Radiochem
Sci 6(3):267–269
Bebko J (2011) Spectroelectrochemical investigations of pertechnetates reduction in the environment of sulfuric and nitric acid. Master thesis, University of Warsaw (in polish)
Box W (1968) Electrolyte for the electrodeposition of technetium. US Patent 3 374 157