Journal of Nuclear and Radiochemical Sciences, Vol. 6, No. 3, pp. 237-241, 2005

Chemical Behaviour of Tc(IV) Complexes under Alpha Irradiation in Chloride MediaF. Poineau, M. Fattahi,* and B. Grambow
SUBATECH UMR 6457 (Université de Nantes, Ecole des Mines, IN2P3/CNRS), 4 rue Alfred Kastler, BP 20722,
F-44307 Nantes cedex 03, France
Received: July 31, 2005; In Final Form: September 30, 2005
In order to study the stability of Tc(IV) complexes in chloride media under alpha radiation produced by a cyclotron, an electrochemical cell was developed. In this cell, the stability of TcCl62−, TcCl5(H2O) −, Tc2OCl104−, TcnOy(4n−2y)+
and TcO2 .xH 2 O were studied in 3 M chloride media with a pH range from 0.3 to 2.5. The stability of a
(TcCl62− /TcCl5(H2O) − /Tc2OCl104−) mixture was also investigated during alpha irradiation under a constant current.
These studies showed that TcCl62− is a very stable compound whereas chloro-oxygenated compounds were oxidized to Tc(VII). Consequently, the relative stabilities of the Tc(IV) complexes in 3 M chloride media under alphairradiation was determined.

1. Introduction

2. Experimental

One option retained for management of nuclear waste is storage in deep underground which presents naturally reducing conditions (absence of oxygen and reducing potential). Nevertheless,the presence of nuclear waste and its radiation associated maylead to the radiolysis of the surrounding media and to the formation of radiolytic compounds. Among these nuclear wastes, 99Tc
is considered as one of the most important fission products: it
represents 10% of the mass of fission product and has an important toxicity (T1/2 = 2.01 × 105 y, β− emitter). That is why studies
on the behaviour of technetium are of great importance.
In the storage media, Tc could be present in Tc(IV) or even
Tc(III) forms. The behaviour of Tc under radiation depends on
the radiolytic species formed : in presence of organic compounds (formate,1 EDTA,2 alcohol t-butyl3, 4) radiolysis leads to
the reduction of Tc(VII) to Tc(IV) and formation of colloids orpolymers whereas in non organic media, oxidation of Tc(IV) to
Tc(VII) is observed.5, 6
After 10 000 years of deposit, alpha emitters will be the preponderant radioactive elements in the spent fuel. Then alpharadiolysis will be the dominant radiolytic process. After thisperiod, 99 Tc will also be present in the spent fuel and in thecase of an alteration of the confinement barrier, the Tc species
could be in contact with the water radiolysis products. In thiscontext, the stability of Tc(IV) complexes under alpha radiation
was studied in aqueous media.
Many researches on the speciation of Tc(IV) were carriedout in chloride media. Recent studies7, 8 have shown that speciation of Tc(IV) between pH = 0 and pH = 2.5 is dominatedby polymeric species. For this reason, in our work, the stability of Tc(IV) complexes was studied in 3 M chloride. Thesestudies were carried out under alpha radiation produced by acyclotron. Furthermore, an electrochemical cell was speciallydeveloped: it was used to study the stability of Tc(IV) complex
under alpha radiation. It has also been used in other works tostudy influence of alpha radiolysis on the stability of UO2 (Ref.
9) and nuclear glass.10
In this work, we present the effects of alpha radiation on
Tc(IV) stability in chloride media in absence and presence ofan electrochemical potential.

2.1. Electrochemical cell and experimental set-up. Alpha
irradiation by a cyclotron has already been used to study the
influence of alpha radiolysis on stabilities of radio-elements.11
The experimental set-up was composed of electrochemicalcells which presented a reduced volume in order to minimize
dilution of radiolytic product. Those cells have an optical window with a thickness < 500 µm that allowed the transmissionof alpha particles.
The cell developed for ours studies, presents a volume of 30
ml and an optical window made of silica with a thickness of
130 ± 10 µm. The cell (Figure 1) consists of: a reactional block
for solution, a cover used to maintain the electrochemical system and a collimator.
The collimator (Ø 6 mm) was designed in order to focus
alpha beam through solution. It also permits to maintain the
optical window whose tightness is assured by an O-ring. The
solutions were homogenized by a magnetic stirrer and permanently purged by Argon bubbling during irradiation.
The electrochemical system is composed of 3 electrodes purchased from Radiometer Analytical, S.A. The working electrode*Corresponding author. E-mail: fattahi@subatech.in2p3.fr. FAX:
+33-2-5185-8452.

C

D

A
B

E

H
F

α
G

Figure 1. Set-up used for alpha radiolysis experiment.
A: argon bubbling, B: auxiliary electrode, C: working electrode, D:
reference electrode, E: cover, F: reactional block, G: magnetic stirrerand H: collimator.

© 2005 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 12/28/2005

238 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005

Scintillation analyzer). The scintillation cocktail used was
ULTIMA GOLD ABTM (Packard). UV-Vis spectra between
each irradiation were recorded on a Shimadzu 2401 double
beam spectrometer in 1 cm cell. Ultra pure water was used as
the reference.
3. Results
All experiments were performed in the aim of describing the
behaviour of Tc(IV) complexes under alpha irradiation. In thiswork, our studies were focused on 3 M chloride media with a
pH range from 0.3 to 2.5 since the speciation of Tc(IV) in thisdomain is well documented.7, 8 According to their results,
Tc2OCl104− is dominant in a pH range from 0 to 1 and TcnOy(4n−2y)+over pH = 1.3. At [Tc] = 10−4 M, TcnOy(4n−2y)+ begin to precipitate in TcO2.xH2O at pH = 2.27. Thus, irradiations of TcCl62−
and Tc2 OCl10 4 − were carried out at pH = 0.3 and those of a
TcnOy(4n−2y)+/TcO2.xH2O mixture at pH = 2.5. The stability of a
TcCl62− /TcCl5(H2O) − /Tc2OCl104− mixture in [Cl−] = 3 M, pH =1 was also studied under a constant current (i = –500 µA).
3.1. Irradiation of TcCl62−. TcCl62− (Tc = 9.85.10−5 M) was
irradiated in a 3 M chloride medium (pH = 0.3), with a dose rateof 117.43 Gy.min−1. Changes of absorption spectra during irradiations are presented in Figure 2.
Figure 2 reveals that TcCl62− is practically stable under alphairradiation. After irradiation with a dose of 11700 Gy, only 4% of TcCl62− was transformed. Thus, the initial radiolytic yield
was found to be –(3.40 ± 1.13).10−10 mol.J−1, which is 1000 lower
than that of Fattahi et al5 under gamma radiation in the same
medium.
Under the same experimental conditions, the alpha irradiation of a 3 M chloride solution (pH = 0.3) without Tc led to theapparition of a specie characterized by an absorption band at
230 nm. According to literature data [14] this band is characteristic of the radiolytic product Cl3−.
3.2. Irradiation of a TcCl 6 2 − /Tc 2 OCl 10 4 − mixture. A
TcCl62− /Tc2OCl104− mixture (Tc = 10.95.10−5 M) was irradiatedin a 3 M chloride solution (pH = 0.3) with a dose rate of 117.43
Gy.min−1. Changes of absorption spectra during irradiations
are presented in Figure 3 and the evolution of Tc species in
Figure 4.
Figure 3 and 4 confirm the stability of TcCl62− and revealed
that irradiation of Tc2OCl10 4− leads to its oxidation to TcO 4 −.
This reaction is characterized by disappearance of the band at
354 nm (ε = 9307 M−1cm−1) of Tc2OCl104− and the apparition at
287 nm (ε = 2316 M−1cm−1) of the band characteristic of TcO4 −.
Consequently, the hypothesis that irradiation of Tc2 OCl10 4 −leads to its oxidation to Tc(VII) was proved. The initial radiolytic yields of the Tc species are presented in Table 1.
3.3. Irradiation of a TcnOy(4n−2y)+ /TcO2.xH2O mixture. A
TcnOy(4n−2y)+/TcO2.xH2O mixture ( Tc = 9.9.10−5 M) was irradiated in a medium of [Cl−] = 3 M and pH = 2.5, with a dose rate32.5B) 11 700 Gy : (TcCl 62-/Cl 3-)

Cl 3-A) 0 Gy : (TcCl 62-)2

Absorbance(XR 140) is made of a platinum plate (1 cm × 4 cm). The auxiliary electrode (XR 110) is constituted of a platinum plate (5 mm
× 5 mm). This electrode is installed in a lounge (Al 120) in
order to isolate oxidation products that may form at this electrode during reactions. The reference electrode is an Ag/AgClelectrode (XR 300), E = 248 mV/ ENH).
These electrodes were installed on a glass cover CP 4R which
was settled and screwed on the cell cover. This electrochemicalsystem was connected to a PGP 201 potentiometer equippedwith voltamaster 4, which allows to work under constant current
or potential and provides analyses by cyclic voltammetry. This
experimental set-up was then settled on an ionisation chamberand controlled from the outside of the cyclotron alveolus throughlarge coaxial cables.
Alpha irradiation was performed at the CERI cyclotron(CNRS-Orleans). This cyclotron generates alpha particles(4He2+) in an energy range from 5 MeV to 45 MeV. Energy of
28 MeV was chosen for all the Tc experiments. The calculations from SRIM2000 code indicated that 4 He2+ (28 MeV)
passed into the cell carrying energy of 5–6 MeV and a penetration depth in solution about 45 µm. The rest of energy wasabsorbed by the cell window and by the titanium windows of
the ionization chamber. The alpha beam was monitored during
the experiments as a function of the measured 4He2+ current on
the ionisation chamber. During all the experiments, the currentof 4He2+ flux in solution was fixed in the range from 10 nA to 50
nA. The irradiation time depending of experience, vary between
5 mn to 40 mn. The duration of an experiment is around 1h30.
2.2. Dosimetry and H2O2 measurement. Doses were measured using the Fricke’s dosimetry12 which is based on the oxidation of Fe(II) to Fe(III) by water radiolysis products. The
Fe(II) solution used was 1 mM FeSO 4 prepared in a 0.4 M
H2SO4 solution. The concentration of Fe(III) was then determined by UV-Vis measurement at 304 nm (ε = 2197 M−1cm−1).
The radiolytic yield G (Fe(III)) used for the dose calculations
was 1.06 10−6 mol. J−1.
The concentrations of H2O2 produced during the irradiation
were measured using the Ghormley’s method13 which is basedon oxidation of I− to I3 − by H2O2. The 1 mM iodide solution,used in this work, was prepared by dissolving KI in a 0.1 M
NaOH solution. The measurement protocol is showed as follows: 1) A phthalate buffer solution (pH = 6) was added to the
KI solution. 2) The [I3−] was then determined by UV-Vis measurement at 350 nm (ε = 28000 M−1cm−1). 3) The concentrationof H2O2 in solution was finally determined from the concentration of I3−.
2.3. Chemical and Sample preparation. The NaTcO4 solution used for all syntheses was purchased from Cerca, Co
France. All chemicals used are of analytical purity and all
solutions were prepared with Milli-Q water.
The stock solution of TcCl62− (0.02 M, 6 M HCl) was prepared by heating TcO4− at 90 ˚C in concentrated HCl. The stock
solution was kept in the dark at an inert gas glove box.
The stock solution of Tc2OCl10 4− (8.8 mM) in [Cl−] = 3 M,
pH = 0.3 was synthesised by using the method recently developed.8 The TcCl62− /Tc2OCl10 4− mixture in 3 M chloride solution (pH = 0.3, [Tc] = 10.95.10 −5 M) was prepared from
Tc2OCl104− and TcCl62− stock solutions.
The TcnOy(4n−2y)+/TcO2.xH2O solution was prepared by diluting TcCl62− in a medium of [Cl−] = 3 M and pH = 1. The pH
was adjusted to 2.5 by NaOH. The solution was kept in an inert
gas glove box, sealed and carried to Orleans cyclotron facility
under inert atmosphere to avoid oxidation.
The mixture TcCl 6 2 − / TcCl 5 (H 2 O) − / Tc2 OCl10 4 − used forexperiment under constant current was synthesised by reduction (i = –500 µA) of TcO4 − in the electrochemical cell in 3 M
chloride solution (pH = 1).
2.4. Other techniques. 99Tc analysis was performed using
liquid scintillation counting: Packard 2550 TR/AB Liquid

Poineau

1.5

1

0.5

0
200

250

300

350

400

450

500

Wavelength nm

Figure 2. Change of absorption spectra of TcCl62− during alpha irradiation. Operating conditions: dose rate: 117.43 Gy.min−1; atmosphereargon; [Tc] = 9.85.10−5 M, [Cl−] = 3 M, pH = 0.3.

J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005 239

Chemical Behaviour of Tc(IV) Complexes under Alpha Irradiation
0.9

2
1.8
1.6

0.6

AbsorbanceAbsorbance

1.4
1.2
1

0 Gy : (Tc2OCl104-/TcCl62-)

0.81174 Gy

0.6

0.3

0 Gy : (TcnOy(4n-2y)+/TcO2.xH2O)

4697 Gy

0.415265 Gy : (TcO4-/TcCl 62-)0.2

1713 Gy : (TcO4- )

0
200

250

300

350

400

450

500

550

0

600

200

250

300

350

400

Wavelength nm

450

500

550

600

650

700

Wavelength nm

Figure 3. Change of absorption spectra of a Tc2OCl104− /TcCl62− mixture during alpha irradiation. Operating conditions: dose rate: 117.43
Gy.min−1; atmosphere argon; [Tc] = 10.95.10−5 M, [Cl−] = 3 M, pH =0.3; doses: 0 Gy, 1174 Gy, 4697 Gy and 15365 Gy.

Figure 5. Change of absorption spectra of a TcO2.xH2O/TcnOy(4n−2y)+mixture during alpha irradiation. Operating conditions: dose rate:
28.55 Gy.min−1; atmosphere argon; [Tc] = 9.9.10−5 M, [Cl−] = 3 M, pH= 2.5; doses: 0 Gy and 1713 Gy.
0.000120.0001

C : TcO4-

0.00010.00008

0.00006[Tc] M[Tc] M

0.00008-

C : TcO4

0.00004

A : TcnOy(4n-2y)+

0.00006

0.00004

B : TcO2.xH2O

A : Tc2OCl1040.00002

B : TcCl62-

0.00002

0
0

2000

4000

6000

8000

10000

12000

14000

16000

0

18000

0

Dose Gy

200

400

600

800

1000

1200

1400

1600

1800

Dose Gy

Figure 4. Concentration of Tc species as a function of dose duringalpha irradiation of a Tc2OCl104− /TcCl62− mixture. Operating conditions: [Cl− ] = 3 M, pH = 0.3; atmosphere argon. Dose rate: 117.43
Gy.min−1. A: Tc2OCl104−, B: TcCl62− and C: TcO4 −.

Figure 6. Concentration of Tc species as a function of dose duringalpha irradiation of a TcO2.xH2O/TcnOy(4n−2y)+ mixture. Operating conditions: [Cl−] = 3 M, pH = 2.5; atmosphere argon. Dose rate: 28.55
Gy.min−1. A: TcnOy(4n−2y)+, B: TcO2.xH2O and C: TcO4 −.

TABLE 1: G Values for TcO4 −, TcCl62− and Tc2OCl104− in 3
M Chloride, pH = 0.3 Under Alpha Radiation

TABLE 2: G Values for TcO4 − and TcnOy(4n−2y)+ in 3 M
Chloride (pH = 2.5) Under Alpha Radiation

CompoundG (mol.J−1)

CompoundG (mol.J−1)

Tc2OCl10 4−
TcCl62−
TcO4 −–9.05.10−9–2.70.10−10
1.02.10−8

TcnOy (4n−2y)+
TcO4 −–1.09.10−7
1.12.10−7

Dose rate: 28.55 Gy.min−1, argon atmosphere−1

Dose rate: 117.43 Gy.min , argon atmosphere
14

B : H2O2 without Tc

12

10[H2O2]10-5 M

of 28.55 Gy.min−1. During this experiment, the Tc concentration was measured using liquid scintillation after filtration
through a 0.2 µm membrane filter. The changes of absorption
spectra during irradiations are presented in Figure 5 and theevolution of Tc species in Figure 6.
These figures reveal the complete oxidation of Tc(IV) species to Tc(VII) after a dose of 1713 Gy. The initial radiolytic
yield for the soluble Tc species are presented in Table 2.
During this experiment the concentration of H2O2 was determined using Ghormley’s method (Figure 7). The value of[H 2O2 ] produced in presence of Tc(IV) was compared to thevalue obtained without Tc. The initial radiolytic yield of H2O2
without Tc was then determined: G(H2O2) = 1.23. 10−7 mol.J−1.
Meanwhile, in presence of Tc(IV), H2O2 or OH. radicals werecompletely consumed in a dose range from 0 Gy to 400 Gy.
3.4. Irradiation of a TcCl62− /TcCl5 (H2O)− /Tc2OCl104− mixture under constant current. Aim of this experiment is to
study the behaviour of Tc(IV) complexes during alpha irradiation under reducing potential: a mixture TcCl62− /TcCl5(H2O) − /Tc2OCl10 4− was irradiated in a 3 M chloride solution (pH = 1)
with a dose yield of 34.40 Gy.min−1 under a constant courant (i= –500 µA). During irradiation, the electrochemical potential
fluctuated between –420 mV and –450 mV/(Ag/AgCl). The

8

A : H2O2 with Tc
642

H2O2 = 0
0
0

200

400

600

800

1000

1200

1400

1600

1800

Dose Gy

Figure 7. Concentration of produced H 2O2 with A) and B) for inabsence and in presence of Tc(IV) during irradiation of a 3 M chloride solution (pH = 2.5); atmosphere argon. Dose rate 28.55 Gy.min−1.

changes of absorption spectra during irradiations are presented
in Figure 8 and the evolution of Tc species in Figure 9. Analysesof Figure 8 and 9 reveal that the electrochemical potential can
not impede the oxidation of Tc(IV) to Tc(VII). The experimental yields of Tc species are presented in Table 3.

240 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005

Poineau

1.2

1Absorbance

0.8

0 Gy : (TcCl 62-/ TcCl5(H2O)-/ Tc2OCl104-)0.6

860 Gy0.41720 Gy
3096 Gy : (TcO4- / TcCl62-)

0.2

0
220

270

320

370

420

470

Wavelength nm

Figure 8. Change of absorption spectra of a TcCl62− /TcCl5 (H2O) − /Tc2OCl104− mixture during alpha radiation under a constant current (i= –500 µA). Operating conditions: dose rate: 34.40 Gy.min−1; atmosphere argon; [Tc] = 8.10−5 M, [Cl−] = 3 M, pH = 1; doses: 0 Gy, 860
Gy, 1720 Gy and 3096 Gy.
0.00006

D : TcO4-

0.00005

stable than oxygenated Re(IV) complexes. Furthermore, literature data reveal that the Tc(VII)/Tc(IV) potential value depends
on the number of chlorine atoms in the Tc(IV) structure: thispotential is equal to 0.595 V/ENH for Tc(IV) = TcO(OH)2 (Ref.
16) and 0.849 V/ENH for Tc(IV) = TcCl5 (H2O) −.17 Thus, theincreasing of Tc(VII)/Tc(IV) potential value with the number ofchlorine atoms can also explain the relative stability of the
Tc(IV) complexes.
Consequently, the experiment performed in [Cl−] = 3 M, pH= 1 showed that TcCl62−, which exhibits six chlorine atoms in
its structure, is the most stable of Tc(IV) complexes whereas
TcCl5(H2O) − and Tc2OCl104− with each one five chlorine atoms/
Tc are less stable. Between these two compounds, TcCl5(H2O) −is less stable than Tc2OCl104−, which is probably due to the presence of π bonding in the [Tc-O-Tc] 6+ structure8 which stabilizes
more strongly the valence IV than the H2O ligand of TcCl5(H2O)−.
In a [Cl− ] = 3 M solution (pH = 2.5), the measurement of[H2O2] in absence and presence of Tc(IV) have proved that thiscompound is involved in the radiolytic oxidation of Tc(IV),which corresponds to the previous studies realised undergamma radiation.5, 18 Among the reaction proposed,18 one isthe oxidation of Tc(IV) to Tc(V) followed by disproportionation of Tc(V) to Tc(VI), Tc(IV) and Tc(VII):[Tc] M

0.00004

Tc(IV) + H2O2 → Tc(V) + OH. + OH−
2Tc(V) → Tc(VI) + Tc(IV)
2Tc(VI) → Tc(VII) + Tc(VI)0.00003

A : TcCl620.00002

B : TcCl5(H2O)0.00001

C : Tc 2OCl104-

0
0

500

1000

1500

2000

2500

3000

3500

Dose Gy

Figure 9. Concentration of Tc species as a function of dose duringalpha irradiation of a TcCl62− /TcCl5(H2O) − /Tc2OCl104− mixture undera constant current (i = –500 µA). Operating conditions: [Cl−] = 3 M,
pH = 1; atmosphere argon. Dose rate: 34.40 Gy.min−1. A: TcCl62−, B:
TcCl5(H2O) −, C: Tc2OCl104− and D: TcO4 −.

TABLE 3: G Values for TcO 4 − , TcCl 62− , Tc 2 OCl10 4− andTcCl5 (H2O) − in 3 M Chloride (pH = 1) During Alpha Radiation Under a Constant Current (i = –500 µA)
Compound2−

TcCl6
Tc2OCl10 4−
TcCl5 (H2O) −TcO4 −

G (mol.J−1)−9–2.8.10–8.66.10−9–1.58.10−8
2.98.10−8

Dose rate: 34.40 Gy.min−1, argon atmosphere

Nevertheless, if oxidation of Tc(IV) to Tc(VII) occurs exclusively according to (1), (2) and (3), it implies that G(Tc(VII) =(1/2) G(H 2O2 ). Considering the experimentally determined
G(Tc(VII)) and G(H2O2) values: 1.12 10−7 mol.J−1 and 1.23 10−7mol.J−1, respectively, it appeared that G(Tc(VII) > (1/2)G(H2O2):
this result indicated that other mechanisms than (1), (2) and (3)took place in the Tc(IV) oxidation.
Furthermore, irradiation of NaCl solution leads to formationof chlorinated species19: Cl2.−, Cl2 and Cl3 −, these species may
also be involved in Tc(IV) oxidation .
It has been discussed 5 that under gamma radiation, Cl2.− isinvolved in Tc(IV) oxidation. The mechanisms proposed arelisted below:
Tc(IV) + Cl2.− → Tc(V) + 2Cl−
Tc(V) + Cl2.− → Tc(VI) + 2Cl−
Tc(VI) + Cl2.− → Tc(VII) + 2Cl−

We showed in this paper that under alpha irradiations, theTc(IV) complexes in 3 M chloride media undergo oxidation to
Tc(VII). In the same medium, non irradiated solution of Tc(IV)complexes are stable against oxidation for times equivalent tothose of irradiation experiments. Under alpha radiation, TcCl62−
is the most stable and the species having cores of the [Tc-O-Tc] 6+
and [Tc(µ-O)2Tc] 4+ structures were oxidized easily.
The determination of the initial radiolytic yields allows toclassify the Tc(IV) complexes according to their stabilities:
TcCl62− > Tc2OCl104− > TcCl5(H2O) − > TcnOy(4n−2y)+.
This order suggested that the stability of Tc(IV) complexes
depends on the number of oxygen and chlorine atoms in the
structure. The presence of chlorine atoms in the structure canincrease the stability of the Tc(IV) complexes, which is due tothe electron donation capability of chlorine atoms. It is noteworthy that this phenomena has already been observed for rhenium15: the chlorinated Re(IV) complexes are obviously more

(4)
(5)
(6)

Considering the presence of H2O2 and Cl2−, it was proposedthat G (Tc(VII) can be formulated as :G (Tc(VII) = 1/3 G(Cl2.−) + 2/3 G(H2O2)

4. Discussion

(1)
(2)
(3)

(7)

However, in the present work, we think that the mechanism
described in (4), (5) and (6) may occur in the Tc(IV) oxidation.
Nevertheless, the presence of Cl 3 − during alpha irradiation,
indicates that this species may also be involved in Tc(IV) oxidation. Radiolytic oxidation of Tc(IV) in concentrated chloride
media can be considered as a complex process. And for clarifying the mechanisms of this oxidation, further experiments bypulsed alpha radiolysis have to be performed in order to specify
the different chlorinated radicals in absence and presence ofTc.
5. Conclusion
This work showed that among the Tc(IV) complexes underalpha irradiation TcCl62− is stable whereas the other complex
undergo oxidation to TcO4 −. This work has permitted to classify the Tc(IV) complexes as function of their stabilities underalpha radiation.

Chemical Behaviour of Tc(IV) Complexes under Alpha Irradiation

J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005 241- It showed that H2O2 is involved in the radiolytic oxidation of
Tc(IV)- The experiments realised under electrochemical potential
proved that in spite of a reducing potential the radiolytic oxidation of Tc(IV) can still occur. This result indicated that ina deep storage media, without organic species, the mobility of
Tc can be dependant on TcO4 − produced by the radiolytic oxidation of Tc(IV) compounds.

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For understanding better the oxidation mechanisms, it will
be interesting to perform experiments by alpha pulsed radiolysis in presence and absence of Tc(IV) and determine the role ofchlorinated radicals. In this aim, the cell developed in thiswork will be used for further experiments on 99Tc at the future
cyclotron of Nantes.
Acknowledgements. Authors want to thank G. Blondiaux
director of CERI laboratory (CNRS-Orleans) and his staff forproviding beam time and for technical assistance during experiment.
We also acknowledge M. Dialinas and T. Milleto (SUBATECHNantes) for technical advices and the fabrication of the electrochemical cell.
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