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

Determination of Sr-89/Sr-90
in primary cooling water
Steffen Happel
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Nuclear Chemistry
Department of Chemistry
Philipps-University Marburg
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
Primary cooling water:
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Variety of different radionuclides
B(OH)3 > 1000 ppm
Np/Pu
Cs
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
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.
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 Sractivity is removed
• to be optimized
• disadvantage: loss of Sr
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.
B(OH)3-removal
Strontium extraction
LSC- Option
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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)
Cerenkov-Option
• 20 mL Cerenkov counting
• - Sr-89 activity
• take aliquot to determine Sr-recovery (AAS)
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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)
Comparison of Options
• 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
• 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
Determination of Sr-89/90 using Sr-spec®
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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%)
EiChrom, Inc.
RWE AG
KKW Biblis
Dr. Ralf Sudowe