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

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• 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)

• 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:

• 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 Sr-activity 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

• 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)

• 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®

• 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 AGKKW Biblis

Dr. Ralf Sudowe