Ilias, Jaca, Spain 5 of December 2006 Se-82 purification: distillation and rectification procedures

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ILIAS, Jaca , Spain 5 of December 2006

  • Se-82 purification: distillation and rectification procedures

  • Kornoukhov Vasily

  • INR RAS (Moscow)

  • for IChHPS (Nizhny Novgorod) and IRE (Moscow)


LAL, Orsay , Spain 1 – 2 of June 2006 SuperNEMO: radiopurity requirements

  • Tl-208 (232Th chain) <= 2 Bq/kg

  • (<= 1.5 ppt of Th-232)

  • Bi-214 (238U chain) <= 10 Bq/kg

  • (< = 10 ppt of U-238)





ILIAS, Jaca , Spain 5 of December 2006 SuperNEMO: dangerous isotopes from 232Th chain

  • Th-232, Ra-228, Th-228

  • We must remove Th and Ra

  • How to check the procedure:

  • Th: 232Th (MS), 228Th (HPGe: 208Tl  line)

  • Ra: 228Ra (HPGe: 228Ac line)





ILIAS, Jaca , Spain 5 of December 2006 SuperNEMO: dangerous isotopes from 238U chain

  • Ra-226

  • We must remove Ra

  • How to check the procedure:

  • Ra: 226Ra (Champagne method, HPGe: 214Bi line)



ILIAS, Jaca , Spain 5 of December 2006 SuperNEMO: dangerous isotopes and elements

  • 238U chain:

  • Ra-226

  • 232Th cain:

  • Th-232, Ra-228, Th-228

  • Conclusion: we must remove Ra and Th



ILIAS, Jaca , Spain 5 of December 2006 Industrial scale production of 82Se

  • At present

  • the only technology for industrial scale production of 82Se is centrifugation method

  • and

  • only site for ~ 100 kg-scale production is Svetlana (the ECP, Siberia)



ILIAS, Jaca , Spain 5 of December 2006 82Se transformation at Svetlana (the ECP) (V.Kornoukhov for ILIAS meeting, Orsay, April 2005)

  • Patent #… is “valid” in Russia only

  • natSe  natSeF6 centrifugation  82SeF6

  • 82SeF6  (glow discharge)  82Se + …

  • 82Se washing with H2O (to remove F-ions)

  • Distillation of 82Se in vacuum

  • “Chemical features” of impurities (chemical forms): fluorine compounds (!)



ILIAS, Jaca , Spain 5 of December 2006 General remarks concerning the problem:

  • (+)

  • Se is material for semi-conductive industry: there are many methods for its purification;

  • (-)

  • 82Se is a result of chemical transformation through SeF6 compound, and behavior of U-, Th-, Ra-impurities presented in such product (fluorine compounds) could be quite different of impurities in selenium produced accordingly to standard technology.





ILIAS, Jaca , Spain 5 of December 2006 Some properties of elementary selenium

  • Molecular composition of Se:

  • Vapor (at 700 – 1300 K): Se2 – Se8

  • Melt (at 494.3 – 958.4 K): mixture of cyclo-Se8, katenapoly-Sen

  • (n = 102 – 103), and polycyclo-Sen in chemical equilibrium.

  • Solid: Seα, Seβ – Se8, Sehex. - Sen  

  • Melting Point, K. Se - 443; Se - 453; Sehex – 494,3

  • Boiling point, K – 958.4

  • Density, g/cm3: Seα – 4.46; Seβ - 4.50; Se hex. – 4.717; Seliq (550 K) – 3.918

  • Industrial sources of Se of technical grade (99.0 – 99.7 %):

  • Production of sulfuric acid and non-ferrous metals



ILIAS, Jaca , Spain 5 of December 2006 Distillation procedure & NEMO detector

  • Group from INR RAS (in 1997):

  • 116Cd distillation for NEMO-3 detector

  • (two portions, 0.15 kg + 0.15 kg):

  • good result!



ILIAS, Jaca , Spain 5 of December 2006 Physical methods of Se purification

  • Distillation methods:

  • 1. One – Stage (Simple) distillation

  • 2. Multi-Stage distillation methods:

  • a.  Repeated simple distillation of purified product from previous stages.

  • b.  Rectification – multi-stage counter – current method, realized in one apparatus and in one process.















ILIAS, Jaca , Spain 5 of December 2006 Organizations/institutes could be involved in purification of 82Se

  • Russia (distillation method):

  • Svetlana (the ECP, Siberia)

  • Kurchatov Institute (Moscow)

  • The IChHPS (Nizhny Novgorod)

  • The Institute of Rare Earths (Moscow)

  • Mendeleev Institute (Moscow)

  • USA (“wet” chemistry):

  • INEEL (Idaho Falls)

  • Coordinator (ILIAS/SuperNEMO):

  • Dominique Lalanne



ILIAS, Jaca , Spain 5 of December 2006 The IChHPS & the IRE: goal and content of work

  • Goal: Foundation and selection of technique for production of high-purity 82Se according to the requirements of SuperNEMO project; its technological realization for production of ~100 kg.

  •  Parameters of the product

  • Elementary selenium enriched with 82Se isotope with the content of impurities of Th, Ra (U)  10-10 at.% ( 1 ppt).

  • Requirements to technology 

  • - The yield of the product is 90-95% (to be specified during investigations)

  • - Output of technological scheme and equipment is 5-10 kg/cycle

  • -  The process instrumentation should preclude the unrecovered losses of 82Se even in force majeur (destruction of equipment)

  • -   To exclude the isotopic dilution during purification procedures



ILIAS, Jaca , Spain 5 of December 2006 The IChHPS& the IRE: content of work

  • 1. Thermodynamic and experimental evaluation of chemical and aggregate forms of the limiting impurities and of their relative volatility in selenium produced from SeF6.

  •  2. Experimental verification of purity of Se with natural isotopic composition with respect to the limiting impurities purified by multi-stage vacuum distillation and rectification. Verification of abilities of these methods during production of kilograms amounts of Se extracted from SeF6.

  •  3. Selection of technological process scheme with optimization by numerical methods of the degree of purity, output capacity and reliability.

  •  4. Fabrication of equipment for the process with output capacity of 5-10 kg/cycle.

  •  5. Production of pilot lots, characterization of the product, modifications of the selected scheme and technological modes.







ILIAS, Jaca , Spain 5 of December 2006 Last stage of Se purification and Rn extraction



ILIAS, Jaca , Spain 5 of December 2006 Conclusion

  • At present the only technology for 82Se production is centrifugation method and only site for 100 kg- scale production is Svetlana (the ECP, Siberia)

  • “Chemical features” of impurities in such a product (chemical forms): fluorine compounds.

  • Multi-stages distillation and rectification methods of purification: the IChHPS and the IRE are ready to start purification of Se in the framework of ILIAS.

  • Quality control with “champagne” method could be easy organize at very last stage of the purification procedure








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