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Determination of Sr-89/Sr-90 in primary cooling water

Determination of Sr-89/Sr-90 in primary cooling water. Nuclear Chemistry Department of Chemistry Philipps-University Marburg. Steffen Happel. Method. Extraction of Strontium by solid phase extraction (SPE) using EiChroms Sr-spec ® resin (prepacked column)

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Determination of Sr-89/Sr-90 in primary cooling water

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  1. Determination of Sr-89/Sr-90in primary cooling water • Nuclear Chemistry • Department of Chemistry • Philipps-University Marburg Steffen Happel

  2. Method • Extraction of Strontium by solid phase extraction (SPE) using EiChroms Sr-spec® resin (prepacked column) • Determination of Sr-89/Sr-90 by liquid scintillation counting and Cerenkov counting • Sr recovery to be determined by AAS (Sr-carrier) • Sr-90: 0.5 MeV (Cerenkov-Detection efficiency < 0.5 %) • Sr-89: 1.5 MeV • Y-90: 2.3 MeV • Y needs to be separated from Sr

  3. Primary cooling water: • Variety of different radionuclides • B(OH)3 > 1000 ppm • Np/Pu • Cs

  4. B(OH)3 • No measureable retention on Sr-spec® column • precipitation during evaporation • Removal by cation-exchange • B(OH)3 is not retained on exchange resin • sample preconcentration

  5. Cs • Cs is retained on Sr-spec® column (up to 1 %) • can cause interference in liquid scintillation counting • need to remove when in large excess compared to Sr • removal: -precipitation by adding ammonium phosphomolybdate -use of second Sr-spec™ column -ion-exchange chromatography Horwitz et al.

  6. Cs removal by ion-exchange chromatography • 60 -70 % of the Cs-activity is removed by washing the ion-exchange resin with 10 mL 2.5 M HNO3 and 10 mL 0.1 M HNO3 • less than 10 % of the Sr-activity is removed • to be optimized • disadvantage: loss of Sr

  7. Np/Pu • both retained strongly under high-acid conditions • would interfere in liquid scintillation counting • can be removed by the use of oxalic acid Horwitz et al.

  8. B(OH)3-removal

  9. Strontium extraction

  10. LSC- Option • 5 mL Aliquot + 15 mL scintillation cocktail • - total radioactive strontium • 15 mL Cerenkov-counting • - Sr-89 activity • Sr-90 activity calculated by subtracting Sr-89 activity from total Sr activity • take aliquot to determine Sr-recovery (AAS)

  11. Cerenkov-Option • 20 mL Cerenkov counting • - Sr-89 activity • take aliquot to determine Sr-recovery (AAS) • wait for sufficient Y-90 ingrowth (2-8 days) • add Y-carrier and evaporate to dryness • add 5 mL 8 M HNO3 and load on to Sr-spec® column • strip Y from column with 10 mL 8 M HNO3 • submit collected eluents for Cerenkov counting • take aliquot to determine Y-recovery (AAS)

  12. LSC-Option - results within 1 day - Sr-90 activity only few % of total Sr-activity - need good calibration - mixed waste (scintillation cocktail) Cerenkov-Option - no mixed waste - single point calibration for Sr-89 and Y-90 - wait for Y-90 ingrowth - more accurate - less interference by other radionuclides Comparison of Options

  13. Because of Y-90 ingrowth samples should be counted within 3 hours • crown-ether bled from the column causes luminescence, therefore underground counting should be done with an appropriate blank sample

  14. Determination of Sr-89/90 using Sr-spec® • Sr-spec®shows high selectivity for Sr • Sr content should not exceed 5 mg per sample • easy method • need only few chemicals • no HCl used • results within 1 day (LSC-Option) • no mixed waste (Cerenkov-Option) • good Sr-recovery (about 50%)

  15. EiChrom, Inc.RWE AGKKW BiblisDr. Ralf Sudowe

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