1. THE ROLE OF A CHOICE OF THE TARGET FORM FOR 99Tc TRANSMUTATION
А.А. Kozar’,
V.F. Peretrukhin,
K. E. G e r m a n
Frumkin Institute of Physical Chemistry and Electrochemistry of RAS,
31/4 Leninsky prosp., Moscow, , Russia,

2. IT’S WELL KNOWN (SINCE 2000) - 99Tc transmutation can be the source of artificial stable ruthenium 100–102Ru, the second of the mjst interesting elements of the Periodic table. Such ruthenium has been synthesized as a result of a neutron irradiation of Tc targets up to 20 – 70 % burn-up (for 3 different groups of Tc targets) in experiments at SM high-flux reactor in 1999 –

3. 2
Russian Tc - Transmutation program ( ) Tc(n,g)100Tc(b)100Ru
= Pessimistic

4. for the 1st and 2nd targets batches
Tc transmutation experiment (IPCE RAS – NIIAR, ) In IPC RAS a set of metal disc targets (10x10x0.3 mm) prepared and assembled in two batches with total weight up to 5 g. Transmutation experiment was carried out at high flux SM-3 reactor ( NIIAR, Dimitrovgrad )
2nd batch: Ft > 2 1015 cm-2s-1
1st batch: Ft=1.3 1015 cm-2s-1
99Tc burnups have made:
34  6 % and 65  11 %
for the 1st and 2nd targets batches
----
The high 99Tc burn-ups were reached and about 2.5 g of new matter - transmutation ruthenium were accumulated as a result of experiments on SM-3 reactor
These values are significantly higher of burnups 6 and 16 % achieved on HFR in Petten earlier

5. IRRADIATION OF 99Tc METAL TARGETS IN NUCLEAR HIGH FLUX REACTORS3
IRRADIATION OF 99Tc METAL TARGETS
IN NUCLEAR HIGH FLUX REACTORS
Petten transmutation experiment
99Tc targets: metal cylinders Ø 4.8 mm and with height of 25 mm
99Tc burn-up in Petten reactor are 6 % (T1) and 16 – 18 % (T2).
Dimitrovgrad transmutation experiment on SM high-flux reactor
99Tc targets: metal disks Ø 6.0  0.3 mm and with thickness of 0.3  0.02 mm
Total targets mass is 10 g

6. 99Tc BURN-UP AND HALF-CONVERSION PERIOD4
99Tc BURN-UP AND HALF-CONVERSION PERIOD
Measured and calculated 99Tc burn-up and half-conversion periods in SM reactor.
99Tc burn-up in Petten reactor are 6 % (T1) and 16 – 18 % (T2).
99Tc half-conversion period
 2160 eff. days.
Fig. 2. Calculated dependence of 99Tc burn-up on irradiation time () and its experimental values () for 3 groups of targets.

7. ARTIFICIAL Ru ACTIVITY DECAY5
ARTIFICIAL Ru ACTIVITY DECAY
Actinide content in Tc: 5•10–8 g An per g of Tc (better values are expensive!)
Actinide fission product 106Ru (T1/2=371.6 days) can’t be separated from artificial Ru by chemical methods.
Activity of 106Ru + 106Rh in artificial Ru
 - , days  - , 29.8 sec
106Ru (pure  -radiator, γ is absent)  106Rh  106Pd (stable)
106Rh has 2 main  -lines with energies keV and keV
In Rh activity in Ru from 20 % burn-up targets later  2100 days {5.7 T1/2 (106Ru)} after irradiation stop:
15  2 Bk/g of Ru  total activity of pair 106Ru + 106Rh  30 Bk/g of Ru
Later 10 years after irradiation stop: = 3.2  0.4 Bk/g of Ru < = 3.7 Bk/g 
 Since 2010 artificial Ru from 20% burn-up targets can be used without limitation
Artificial Ru separated from 45 % and 70 % burn-up targets can be used in non-nuclear industry 9 and 8 years after synthesis correspondingly

8. ARTIFICIAL STABLE RUTHENIUM PURIFICATION FROM 106Ru
Relative yield Y of 106Ru nuclei recoiling from spherical grains of technetium powder, in dependence on their diameter D (average fission-fragment path length is about 8 microns).

9. 7
Transformation of disks Ø 6 mm × 0.3 mm in cylindrical targets Ø 6 mm × 6 mm
Fig. 4. Relative position of Tc (Tc-Ru) grains in heterogeneous target.

10. Possible target chemical substances8
Possible target chemical substances
Tc Metal Tc
Tc Carbide Tc6C
Tc Dioxide TcO2
Tc Disulfide TcS2
and its mixtures with inert matter

11. Target substances 1. Metal9
Target substances 1. Metal
Starting material :
TcO2
NH4TcO4
R4NTcO4
Sample type :
Ordinary Powder metal
Fused metal
Single crystal
Foil
Instrumentation
Furnaces
6% H2|Ar industurial balloon mixture
Ingots
Rolling-mill
et cetera…

12. 1. Bulk Tc metal Set-up used for fusion and casting of Tc metal11
1. Bulk Tc metal
Set-up used for fusion and casting of Tc metal
Single crystal Tc metal

13. 1. Tc metal – foil, X-ray study12
1. Tc metal – foil, X-ray study
d: 20 micrometers
Systematic absence of X-ray reflex
= Preferential orientation of crystallites with C axe perpendicular to the foil surface

14. 1. Tc metal – foil, assembling13
1. Tc metal – foil, assembling
Spacer grid-bush with 99Tc targets (1) and aluminium core (2) of capsule for loading in reactor.

15. 1. Tc metal – foil chemical consequences12
1. Tc metal – foil chemical consequences
Dissolution in HNO3 dramatically slowed-down starting from 20% Tc to Ru conversion
Possible to increase the dissolution rate by aggressive agents addition (Ag2+, IO4-) but corrosion problems arises
Possibly the best reprocessing procedure – burning in O2 – not approved by industry to date

16. Target substances 2. Tc Carbide
Orthorhombic Tc metal is formed at low C content

17. Target substances 2. Tc Carbide
Tc6C – non-stoechiometry
Tc6C + nC excess carbon for no slowing-down
Tc6C – formed by :
Tc + C reaction
Tc + C6H6
R4NTcO4 thermal decomposition in Ar

18. Target substances – Tc carbide 2. Tc6C + nC excess carbon
EXAFS study of Tc6C + nC [1] – wavelet presentation
[1] K.German, Ya.Zubavichus ISTR2011

19. 1. Tc carbide chemical consequences12
1. Tc carbide chemical consequences
Dissolution of Tc is more active as no RuC is known and so it is’nt formed during transmutation of Tc carbide to Ru - Tc and Ru being stabilized in separate phases
Drawback: Possible mechanical inclusions of Tc in Ru residue at high burn-ups
Mixtures with C excess could be the best choice because resonance energy neutrons are participating in transmutation due to enhanced thermolisation inside the target

20. 1. Tc dioxide chemical consequences12
1. Tc dioxide chemical consequences
Preparation by chemical reduction – high impurity content
Preparation from NH4TcO4 – similar to Tc metal
Target instability due to excess O released (Ru is stabilised as metal)
Some Tc2O7 formed at high burn-up
This target material is not recommended

21. Preparation of artificial stable Ruthenium by transmutation of Technetium
New Ruthenium is almost monoisotopic Ru-100, it has different spectral properties
It is available only to several countries that develop nuclear industry
Tc target material:
Tc metal powder / Kozar (2008)
Tc – C composite Tc carbide / German (2005)
Rotmanov K. et all. Radiochemistry, 50 (2008) 408 :

22. Conclusions
99Tc transmutation can be the source of artificial stable ruthenium 100–102Ru.
Metal homogeneous Tc targets are possible
Tc carbide targets are favorabale
Artificial ruthenium demanded exposure during 8 – 10 years for application without restrictions
Application of heterogeneous targets with nuclear-inert stuff to reduce a 106Ru radioactivity in artificial Ru
The target form effect the artificial ruthenium purity at equal Tc nuclear density in irradiated volume.

23. Transformation of disks in cylinders in the conditions of identical irradiated volume could allow to lower 106Ru concentration in artificial ruthenium. The minimum fission-fragment path length in Tc metal makes about 5 microns (average fission-fragment path length is about 8 microns). The corresponding form of a heterogeneous target is a tablet consisting of a mix of spherical Tc metal particle in diameter of 5 microns and a nuclear-inert stuff with Tc average density which in 20 times is less, than Tc metal. In this case all fission-fragments, including 106Ru, escape the Tc (Tc-Ru) grains to stuff. The average distance between Tc spherical grains is about 23 microns, between their surfaces is about 18 microns at regular distribution of Tc particles in a target.
Fission-fragment path length in the most applicable nuclear-inert materials (such as ZrO2, Y2O3, MgAl2O4, MgO, Y3Al5O12, SiC, Al2O3, ZrO2-Y2O3, ZrO2-CaO and many others) makes 12 – 15 microns, hence hit probability of 106Ru fission-fragments in the next Tc grain is negligibly small. Artificial ruthenium from such target would be almost free from 106Ru nuclei. Additional purification of commercial Tc from actinide impurities would be not necessary at a choice of such target form instead of metal disks. In this case artificial ruthenium could be applied in non-nuclear field through 3 – 3.5 years after an irradiation, necessary to decay of transmutation product 103Ru (T1/2 = 39.3 days).

24. References
1. V. Peretroukhine, V. Radchenko, A. Kozar’ et al. Technetium transmutation and production of artifical stable ruthenium. // Comptes Rendus. – Ser. Chimie. – – Tome 7. – Fascicule 12. – P – 1218.
2. А.А. Kozar’, V.F. Peretroukhin, K.Vразличные химические методы, а ские методы, а общий технеций, ка мишеналла рутения трансмутацией . Rotmanov, V.A. Tarasov. The elaboration of technology bases for the artificial stable ruthenium preparation from technetium-99 transmutation products. // 7th International Symposium on Technetium and Rhenium – Science and Utilization. Moscow, Russia, July 4 – 8, – Book of Proceedings. – P – Publishing House GRANITSA, Moscow, – 460 p.
3. А.А. Kozar’, V.F. Peretroukhin, K.Vразличные химические методы, а ские методы, а общий технеций, ка мишеналла рутения трансмутацией . Rotmanov, V.A. Tarasov. The elaboration of technology bases for the artificial stable ruthenium preparation from technetium-99 transmutation products. // Ibid. – P. 113.

25. Thank you for the attention !