Empore™ strontium rad disks: validation procedure for strontium-90 analysis in radioactive wastes

⁹⁰Sr determination in radioactive waste is currently supported by Eichrom™ Sr-spec concentration columns. This research was aimed at finding a faster and easier technique, leading to identical results. It was chosen to make use of the 3M Empore™ membranes.

It was deliberatly decided not to follow RP515 procedure (US Department of Energy). ⁹⁰Y will be counted by liquid scintillation after EDTA elution. Official accreditation needs to verify every validation test.

Information concerning the specificity of the membranes has been reviewed. Uncertainty calculation of the activity, as well as the detection limit, are described. The enlarged uncertainty (k = 2) reaches to about 10% for a ⁹⁰Sr activity of 2Bq/L. The detection limit obtained with this procedure reaches to about 50mBq/L for a sample of 0.5L and a 10h counting time. A selectivity test detects the possibility of ⁸⁹Sr presence which could disturb the ⁹⁰Sr determination. Robustness of the method is mainly assured by the use of a tracer (⁸⁵Sr as in RP515). The analysis of non aqueous biological samples has been carried out for accuracy. It required an adaptation of the preparation process. Linearity was tested on a range from 0 to 18.5Bq/L ⁹⁰Sr. The results of 38 routine samples obtained by the Empore™ Sr Rad Disks were compared with those obtained by the Eichrom Sr-spec columns protocol. This comparison showed a good correlation between the two techniques.