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Controlling Se-82 Purification Procedure: SuperNEMO

Learn how to control the purification procedure for Se-82 (Bi-214) in SuperNEMO to ensure the removal of dangerous isotopes from the 238U chain, such as Ra-226. This includes measurements, the Champagne method, and the use of a proportional counter.

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Controlling Se-82 Purification Procedure: SuperNEMO

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  1. ILIAS, Jaca , Spain 5 of December 2006 Se-82 purification: how to control the procedure (Bi-214)? Kornoukhov Vasily INR RAS Moscow

  2. LAL, Orsay , Spain 1 – 2 of June 2006SuperNEMO: radiopurity requirements Tl-208 (232Th chain) <= 2 mBq/kg (<= 1.5 ppt of Th-232) B-214 (238U chain) <= 10 mBq/kg (< = 10 ppt of U-238)

  3. 238U 4,51·109 y 234U 2,47·105 y  234mPa 1,18 min    234Th 24 d 230Th 8,0 ·104 y  226Ra 1602 y T1/2 ~ 103 - 109 y  T1/2 ~ days 222Rn 3,824 d T1/2 ~ minutes  218Po 3,05 min  214Bi 19,7 min  214Pb 26,8 min

  4. ILIAS, Jaca , Spain 5 of December 2006 SuperNEMO: dangerous isotopesfrom 238U chain Ra-226 We must remove Ra How to check the procedure: Ra: 226Ra (HPGe: 214Bi g-line, Champagne method)

  5. ILIAS, Jaca , Spain 5 of December 2006 SuperNEMO: how to measure/control Ra-226? • Radiometric measurements: HPGe, NaI(Tl) • Champagne technique: 226Ra  222Rn (gas) proportional counter bkg (a’sparticles): ~ 1 events/day  10-5 Bq/kg of sample ~ 10 mBq/kg of sample

  6. ILIAS, Jaca, Spain 5 of December 2006 Champagne method: general principle of operation 226Ra (1622 y)  222Rn (3,82 days, noble gas)  3 a’sparticles 222Rn (3,82 d) 218Po(3,05 min)214Pb(26,8 min)214Bi (19,9 min)214Po (164 ms) We just count number of a – decays with proportional counter of very small volume (~ 1 cm3) and with background of ~ 1 – 0,1 events/day (DL ~ 10 – 1,0 mBq/kg of sample)

  7. ILIAS, Jaca, Spain 5 of December 2006 Proportional counter • Low background miniaturized proportional counter was designed for Ar-37 and Ge-71 counting (Homestake Cl-Ar, GALLEX, SAGE) • New version of PC from INR RAS, Moscow (NIM A349 (1994) 466-472) with bkg for a-counting ~ 1 count / 10 days and direct filling with working gas under LN temperature (- 196 oC).

  8. ILIAS, Jaca , Spain 5 of December 2006 Champagne method: general scheme(NEMO-3 Collaboration: NIM A469 (2001) 159-163)

  9. ILIAS, Jaca , Spain 5 of December 2006 Champagne method: results(NEMO-3 Collaboration: NIM A469 (2001) 159-163) Sample Mass mBq/kg mBq/kg of sample Champagne HPGe Frejus Cd metal 200 g 0.33 +/- 0.05 < 2 • Nd2O3 200 g 2,3 +/- 0,2 < 17 • Mo-powder 50 g < 1 < 3,3 • Mo-foil (AMAX) 11 g 1445 +/- 60 1500 +/- 167 • HCl 1,67 +/- 0,15 < 2 • HNO3 < 0,25 - • H2O (DI) < 0,018 -

  10. ILIAS, Jaca , Spain 5 of December 2006 Extraction set up

  11. ILIAS, Jaca , Spain 5 of December 2006 PC is into LN bath (Rn freezing)

  12. ILIAS, Jaca , Spain 5 of December 2006 PC calibration

  13. ILIAS, Jaca , Spain 5 of December 2006 PC is in well-type NaI(Tl)

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

  15. ILIAS, Jaca , Spain 5 of December 2006 Conclusion • SuperNEMO: dangerous isotope from 238U chain is Bi-214(Ra-226), A  10 Bq/kg. • Emanation (“champagne”) method is well developed in INR RAS • The sensitivity is (101) Bq/kg of mass of sample. • Emanation (“champagne”) method and purification procedure based on distillation/rectification method could be used as single integrated method/procedure. The extraction system and last stage of distillation/rectification set up could be easy fitted to each other.

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