Study on several issues related to ⁹⁰Sr activity detection in seawater using DGA resin method

Artificial radionuclide ⁹⁰Sr in seawater has always been one of the important nuclides in marine radioactivity monitoring surveys. Due to systematic issues such as outdated methods, poor decontamination effectiveness, and long analysis cycles, there are problems with the current methods. In this study, we investigated several issues encountered during the application of the DGA resin method to analyze ⁹⁰Sr in seawater, such as co-precipitation and DGA separation effecting on quantitative separation of Sr, the impact of the waiting time after ⁹⁰Sr-⁹⁰Y separation, DGA purification ability for Y separation, and the recovery rate for entire process. The results indicate that: (1) Both iron hydroxide and calcium fluoride have relatively weak carrier abilities for strontium, up to 97% of strontium in seawater is retained in the supernatant of iron hydroxide co-precipitation, indicating that ⁹⁰Sr-⁹⁰Y disequilibrium occurred after iron hydroxide co-precipitation enrichment; (2) The DGA resin has weak strontium adsorption properties, with over 90% of enriched residual strontium being removed during the DGA resin rinsing with sample solution; (3) The waiting time from ⁹⁰Sr-⁹⁰Y separation to measurement should be controlled within 20-40 hours; (4) 20 mL of 0.25 M hydrochloric acid is sufficient to elute 10 mg of yttrium and eliminate residual yttrium on the resin; (5) For the seawater samples, above 70% of the overall chemical recovery rate may be obtained using the DGA resin method.