Automated Radioanalytical System for the Determination of ⁹⁰Sr in Environmental Water Samples by ⁹⁰Y Cherenkov Radiation Counting

Abstract

Strontium-90 is an environmental contaminant at several U.S. Department of Energy sites, including the Hanford site, Washington. Due to its high biological toxicity and moderately long half-life of approximately 29 years, groundwater and surface water contamination plumes containing 90Sr must be closely monitored. The highly energetic beta radiation from the short-lived 90Y daughter of 90Sr generates Cherenkov photons in aqueous media that can be detected by photomultiplier tubes with good sensitivity, without the use of scintillation cocktails. A laboratory-based automated fluid handling system coupled to a Cherenkov radiation detector for measuring 90Sr via the high-energy beta decay of its daughter, 90Y, has been assembled and tested using standards prepared in Hanford groundwater. A SuperLig 620 column in the system enables preconcentration and separation of 90Sr from matrix and radiological interferences and, by removing the 90Y present in the sample, creates a pure 90Sr source from which subsequent 90Y ingrowth can be measured. This 90Y is fluidically transferred from the column to the Cherenkov detection flow cell for quantification and calculation of the original 90Sr concentration. Preconcentrating 0.35 L sample volumes by this approach, we have demonstrated a detection limit of 0.057 Bq/L using a 5 mL volume Cherenkov flow cell, which is below the drinking water limit of 0.30 Bq/L. This method does not require that the sample be at secular equilibrium prior to measurement. The system can also deliver water samples directly to the counting cell for analysis without preconcentration or separation, assuming that the sample is in secular equilibrium, with a detection limit of 7 Bq/L. The performance of the analysis method using a preconcentrating separation column is characterized in detail and compared with direct counting. This method is proposed as the basis for an automated fluidic monitor for 90Sr for unattended at-site operation.

Hybrid Nanoparticle–Polymer Brush Composites for Detection of Low‐Level Radiostrontium in Water

“…In many cases, reliable detection of 90 Sr is problematic due to its generally low concentration in the environment. A reliable radiological monitoring system requires highly selective, sensitive, and stable techniques, especially for pure beta emitters such as 90 Sr. A variety of methods, including solvent extraction, ion exchange, precipitation, among others, have been developed for the separation of strontium . In all cases, a selective molecule or a functional group (such as crown ether derivatives) is used that has a higher affinity for Sr 2+ relative to other similar ions (Ca 2+ , Pb 2+ ) and especially radioactive isotopes of Ba and Ra that have a similar chemical behavior.…”

“…One successful detection scheme is based on detection of Cherenkov radiation generated by the high‐energy electrons produced by 90 Y, the daughter element of 90 Sr beta decay . This approach assumes that the 90 Sr and 90 Y are in a secular equilibrium in the groundwater environment that is both difficult to prove and control due to a clear difference in the chemistry of the two isotopes.…”

“…Another approach allows time for secular equilibrium to be established following extraction of 90 Sr using a strontium selective solid‐phase extraction material such as the commercial product SuperLig 620 (SL) . Extraction of 90 Sr from groundwater creates a pure 90 Sr source from which subsequent 90 Y ingrowth can be then monitored . These previous reports demonstrated low detection limits (57 mBq L −1 ) and the versatility of SL as an extractive material under a wide range of operating conditions .…”

Hydrothermal removal of Sr2+ in aqueous solution via formation of Sr-substituted hydroxyapatite

“…Radiostrontium ( 90 Sr and 89 Sr), a contaminant produced in the nuclear fission of 235 U and 239 Pu [1], is generally found in the high level waste (HLW) of nuclear reaction or groundwater [2,3]. Because 90 Sr has persistent radioactivity and biological toxicity, and long half-life of 28.9 years, it should be removed from HLW to protect humanity and environment [4].…”

Study of Distribution Coefficient of 90Sr on Citumbuk Bentonite and Sukaramai Kaolinite

“…Sr releases into the environment and inserted into human body through the food chain, Sr can substitute Ca +2 ion in human bone structure and increase the risk of diseases such as leukemia [1].…”