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

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