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2014-German-Kozar-Transmutation-ISTR

Technetium transmutation in nuclear reactors

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2014-German-Kozar-Transmutation-ISTR

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  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, 119071, Russia, • kozar@ipc.rssi.ru • guerman_k@mail.ru

  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 reactorin 1999 – 2003 .

  3. 2 Russian Tc - Transmutation program (1992-2003)------------------------------------------------------------------------------------------------------------------------------------------------------------------------------99Tc(n,g)100Tc(b)100Ru = Pessimistic

  4. 2 Tc transmutation experiment (IPCE RAS – NIIAR, 1999-2008)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 1015cm-2s-1 1st batch: Ft=1.3 1015cm-2s-1 99Tcburnups 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. 3 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 of0.3  0.02 mm • Total targets mass is 10 g

  6. 4 99Tc BURN-UP AND HALF-CONVERSION PERIOD Measured and calculated99Tcburn-up and half-conversion periods in SM reactor. 99Tc burn-up in Petten reactor are 6 % (T1)and16 – 18 % (T2). 99Tc half-conversion period 2160 eff. days. Fig. 2. Calculated dependence of 99Tcburn-up on irradiation time () and its experimental values () for 3 groups of targets.

  7. 5 ARTIFICIAL Ru ACTIVITY DECAY Actinide content in Tc: 5•10–8 g An per g of Tc (better values are expensive!) Actinide fissionproduct106Ru (T1/2=371.6 days) can’t be separated from artificial Ru by chemicalmethods. Activity of 106Ru + 106Rh in artificial Ru  -, 371.6 days -, 29.8sec 106Ru (pure-radiator, γ is absent) 106Rh  106Pd (stable) 106Rh has2main -lines with energies 511.8 keVand 621.8 keV In 2006 106Rh activity in Ru from 20 % burn-up targets later 2100 days {5.7 T1/2 (106Ru)} afterirradiation stop: 15  2 Bk/g of Ru total activity of pair106Ru + 106Rh  30 Bk/gof 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. 6 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 incylindrical targets Ø 6 mm × 6 mm Fig. 4. Relative position of Tc (Tc-Ru) grains in heterogeneous target.

  10. 8 Possible target chemical substances • Tc Metal - Tc • Tc Carbide - Tc6C • Tc Dioxide - TcO2 • Tc Disulfide - TcS2 • and its mixtures with inert matter

  11. 9 Target substances1. Metal • Starting material : • TcO2 • NH4TcO4 • R4NTcO4 • Sample type : • OrdinaryPowder metal • Fused metal • Single crystal • Foil Instrumentation • Furnaces • 6% H2|Ar industurial balloon mixture • Ingots • Rolling-mill • et cetera…

  12. 11 1. Bulk Tc metal • Set-up used for fusion and casting of Tc metal • Single crystal Tc metal

  13. 12 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. 13 1. Tc metal – foil, assembling • Spacergrid-bush with 99Tc targets (1) and aluminiumcore(2) of capsule for loading in reactor.

  15. 12 1. Tc metal – foilchemical 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 substances2. Tc Carbide • Orthorhombic Tc metal is formed at low C content

  17. Target substances2. 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 carbide2. Tc6C + nC excess carbon • EXAFS study of Tc6C + nC [1] – wavelet presentation [1] K.German, Ya.Zubavichus ISTR2011

  19. 12 1. Tc carbidechemical 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. 12 1. Tc dioxidechemical 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. – 2004. – Tome 7. – Fascicule 12. – P. 1215 – 1218. • 2. А.А. Kozar’, V.F. Peretroukhin, K.Vразличные химические методы, а ские методы, а общий технеций, камишеналла 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, 2011. – Book of Proceedings. – P. 113. – Publishing House GRANITSA, Moscow, 2011. – 460 p. • 3. А.А. Kozar’, V.F. Peretroukhin, K.Vразличные химические методы, а ские методы, а общий технеций, камишеналла 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 !

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