Strontium-90 (90Sr) is a major contaminant at nuclear legacy sites. The mobility of 90Sr is primarily governed by sorption reactions with sediments controlled by high surface area phases such as clay and iron oxides. Sr2+ adsorption was investigated in heterogeneous unconsolidated aquifer sediments, analogous to those underlying the UK Sellafield nuclear site, with grainsizes ranging from gravels to clays. Batch sorption tests showed that a linear Kd adsorption model was applicable to all grainsize fractions up to equilibrium [Sr] of 0.28 mmol L-1. Sr2+ sorption values (Kd; Langmuir qmax) correlated well with bulk sediment properties such as cation exchange capacity and surface area. Electron microscopy showed that heterogeneous sediments contained porous sandstone clasts with clay minerals (i.e. chlorite) providing an additional adsorption capacity. Therefore, gravel corrections that assumed that the > 2 mm fractions are inert were not appropriate and underestimated Kd(bulk) adsorption coefficients. However, Kd (<2 mm) values measured from sieved sediment fractions, were effectively adjusted to within error of Kd (bulk) using a surface area dependant gravel correction based on particle size distribution data. Amphoteric pH dependent Sr2+ sorption behaviour observed in batch experiments was consistent with cation exchange modelling between pH 2-7 derived from the measured cation exchange capacities. Above pH 7 model fits were improved by invoking a coupled cation exchange/surface complexation which allowed for addition sorption to iron oxide phases. The overall trends in Sr2+ sorption (at pH 6.5-7) produced by increasing solution ionic strength was also reproduced in cation exchange models. Overall, the results showed that Sr2+ sorption to heterogeneous sediment units could be estimated from Kd (<2 mm) data using appropriate gravel corrections, and effectively modelled using coupled cation exchange and surface complexation processes.

Strontium-90 (90Sr) is a major radioactive component that has attracted great attention, but its detection remains challenging since there are no specific energy rays indicative of its presence. Herein, a biosensor that is capable of rapidly detecting Sr2+ ions is demonstrated. Simple colorimetric method for sensitive detection of Sr2+ with the help of single-stranded DNA was developed by preparing MnO2 nanorods as oxidase mimic catalysis 3,3\',5,5\'-tetramethylbenzidine (TMB). Under weakly acidic conditions, MnO2 exhibited a strong oxidase-mimicking activity to oxidize colorless TMB into blue oxidation products (oxTMB) with discernible absorbance signals. Nevertheless, the introduction of a guanine-rich DNA aptamer inhibited MnO2-mediated TMB oxidation and reduced oxTMB formation, resulting in blue fading and diminished absorbance. Upon the addition of strontium ions to the system, the aptamers formed a stable G-quadruplex structure with strontium ions, thereby restoring the oxidase-mimicking activity of MnO2. Under the best experimental conditions, the absorbance exhibits a linear relationship with the Sr2+ concentration within the range 0.01-200 μM, with a limit of detection of 0.0028 µM. When the concentration of Sr2+ from 10-8 to 10-6 mol L-1, a distinct color change gradient could be observed in paper-based sensor. We successfully applied this approach to determine Sr2+ in natural water samples, obtaining recoveries ranging from 97.6 to 103% with a relative standard deviation of less than 5%. By providing technical solutions for detection, our work contributed to the effective monitoring of transportation of radioactive Sr in the environment.

BACKGROUND: The Fukushima Daiichi Nuclear Power Plant accident (2011) released large amounts of radioactive substances into the environment and generated highly radioactive debris. Post-accident countermeasures are currently in the phase of fuel debris removal, which requires the analysis of radioactive contaminants in the environment and fuel. The spectra of solely β-emitting nuclides, such as 90Sr, overlap; thus, an effective method for nuclide separation is desired. Since conventional methods for high-dose sample analysis pose substantial exposure risks and generate large amounts of secondary radioactive waste, faster procedures allowing for decreased radiation emission are highly desirable.
RESULTS: In this study, we developed a 90Sr2+ quantitation technique based on liquid scintillation counting (LSC)-coupled capillary transient isotachophoresis (ctITP), along with two-point detection and relying on the rapid concentration, separation, and fractionation of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-complexed 90Sr2+ in a single run. The applicability of our method for the analysis of real-world samples was verified by conducting addition-recovery experiments using a seawater reference material and radioactive liquid waste obtained from the radioactive waste treatment facility at the Japan Atomic Energy Agency. The recovery determined by LSC was 95-113%, indicating successful quantitative analysis. 90Sr recovery was determined to be 90.1% from a contaminated water sample obtained from the Fukushima Daiichi Nuclear Power Plant, which was analyzed using the standard addition of 90Sr. The sensitivity (detection limit = 0.016 Bq) of the proposed method on a radioactivity basis was equal to or higher than that of the conventional method using ion exchange-LSC (0.012-0.07 Bq).
UNASSIGNED: Our method allows for the handling of high-dose radioactive samples at the microliter level and is substantially faster than conventional ion exchange protocols, whereas ctITP has not been used for practical applications due to inaccurate collection and lack of a suitable chemical system. The concentration-separation-fractionation protocol in ctITP is successful due to the existence of a rare inert Sr2+ complex and precise fractionation. This study establishes a pathway toward safer and more practical analysis of radionuclides.

The pure beta emitter 90Sr (T1/2 = 28.8y) is a typical contaminant released by nuclear accidents and nuclear explosions. In the event of a nuclear disaster, it is crucial to identify radioactive pollutants quickly, to expedite the public\'s awareness of radiation exposure. In this work, a rapid 90Sr analysis protocol using thermal ionization mass spectrometry (TIMS) was developed for milk samples. With the improved sample preparation, Sr separation, and a newly developed TIMS method, 18 milk samples can be analyzed in less than 30 h and only 1 mL of cow milk is required for the complete analysis. The minimum detectable activity concentration of 90Sr is affected by the stable Sr concentration therefore, it is around 500 mBq·kg-1 (∼100ag·g-1). Additionally, 87Sr/86Sr isotope ratios (0.71518(9)-0.74132(4)) were determined for the first time in Japanese cow milk samples.

This study introduces an efficient method for determining 90Sr activity levels in seawater, reducing the processing time to <3 h for 50 L of seawater. The key feature of the proposed method is the chemical separation of 90Y when it is in equilibrium with 90Sr, which is achieved by utilizing custom-made sample-loading equipment and an automated radionuclide separation instrument. As a result, the procedure consistently yields a recovery rate > 90 % for 90Y. Investigations of 90Sr levels were conducted in the ocean southeast of Jeju Island from November 2021 to January 2023. Owing to the regional ocean circulation, this region was among the first within the Korean Peninsula to experience the impact of the Fukushima-accident-derived radionuclides. Throughout the investigation period, the observed 90Sr activity concentration ranged from 0.57 to 1.0 Bq m-3. No distinct temporal variation of 90Sr was observed in the selected area during the investigation.

90Sr and 137Cs activity concentrations were determined by radiometric methods in 76 soil samples (soil, litter, rain gutter deposit, and roadside sediment samples) affected by the Fukushima Dai-ichi Nuclear Power Station (FDNPS) accident and collected from the Fukushima exclusion zone. The 90Sr and 137Cs activity concentrations were in the range of 3 to 1050 Bq kg-1 (median 82 Bq·kg-1) and 0.7 to 6770 kBq·kg-1 (median 890 kBq·kg-1), respectively (decay correction date: March 15, 2011). A strong positive correlation was found between 90Sr and 137Cs activity concentration and higher mobility of 90Sr was confirmed in Japanese soil samples. The activity ratio of 90Sr/137Cs in 85% of all samples was in the range of 5.0 × 10-5 to 5.0 × 10-4 with a median of 1.2 × 10-4. From the activity ratio values it was concluded that the 90Sr released to the atmosphere was only around 0.0003-0.02 PBq which is negligible compared to the Chernobyl accident (∼10 PBq) or other nuclear accident contaminations. From the standpoints of radioecology and radiation safety, 137Cs remains the primary pollutant of the FDNPS accident.

In the vicinity of the Chornobyl Nuclear Power Plant (ChNPP), the cooling pond (CP) was an artificially maintained reservoir with water levels regulated to 7 m above the Pripyat River until May 2014, when its pumps stopped operating, resulting in a natural drawdown. To investigate the surface-groundwater system before and after the drawdown, we evaluated the spatial and temporal changes in 90Sr and 137Cs radionuclide concentrations and groundwater levels in the shallow unconfined aquifer near the ChNPP from 2010 to 2019. Additionally, we compared water levels and 90Sr concentrations in Azbuchin Lake, wetlands inside the CP, and the Pripyat River. Using three-year averages before (2011-2013) and after (2017-2019) the drawdown period, we found that 90Sr concentrations significantly increased up to 102 kBq/m3 in the Pripyat River floodplain, north of ChNPP, exceeding the WHO drinking water guideline of 10 kBq/m3. In contrast 137Cs concentrations ranged consistently between 10 and 100 Bq/m3. The groundwater levels decreased over 50 cm at approximately 65 % of shallow monitoring wells and up to 6 m near the CP. The 90Sr concentration increases in some wells at the Pripyat River floodplain were associated with decreased dilution rates from the CP due to the reduced CP leakage, causing changes in groundwater flow direction and decreases in groundwater velocity. From the new finding of this study that the drawdown increased 90Sr concentrations near the floodplain, we estimated the 90Sr flux and contribution to the Pripyat River and the 90Sr contribution did not change significantly after the drawdown. However, radionuclides may accumulate more at the floodplain in the future; therefore, additional monitoring is required to verify 90Sr transport from areas of elevated concentrations and its impact on groundwater in the aquifer.

Nuclear weapons testing in the atmosphere during the 1950s and 1960s deposited fallout throughout the world, exposing all humans to food and water before the Limited Test Ban Treaty ended large-scale tests. The largest effort to measure in vivo fallout in humans, performed by Washington University (USA), collected over 300,000 deciduous teeth to document a sustained increase in Strontium-90 (Sr-90) during testing and a sharp decline after the test ban. Sr-90 patterns and trends in teeth were consistent with those of bones and milk. Sr-90 is still detectable in about 100,000 of the teeth, which were never tested. Tooth donors were born during atmospheric testing (1946-1965) and thus exposed to fallout in utero and during infancy/childhood, when exposures pose the greatest health risk. Preliminary analysis of global fallout\'s health risk in the United States indicates recent cancer mortality in several high-fallout areas exceeded that of states with the lowest fallout, peaking for the cohort born in the early 1960s, when fallout was highest. These findings support subsequent measurement of Sr-90 in deciduous teeth of persons who died of diseases such as cancer, along with controls, a novel approach to assessing fallout hazards.

Extramedullary plasmacytoma (EMP) is a benign round cell tumor that is most commonly found in cutaneous locations in dogs and occurs less frequently in the oral cavity. They are highly radiosensitive, are distinct from systemic multiple myeloma syndrome and wide surgical excision is typically curative. This report describes five cases of non-invasive oral EMP in dogs treated with a combination of marginal excision and strontium-90 plesiotherapy. All five cases had narrow or incomplete margins on histopathologic evaluation but experienced no recurrence after combination therapy. Plesiotherapy radiation may offer a potential adjunct treatment for non-invasive oral EMP by providing a superficial dose of radiation that complements a less invasive surgical removal. The combination of plesiotherapy and marginal excision may offer an alternative to wide surgical excision for non-invasive oral EMPs.

When artificial radionuclides are released into the atmospheric environment, one of the important processes by which they affect the human radiation dose is the direct deposition of the radionuclides onto crop surfaces. Because leafy vegetables are consumed while fresh and often raw, the mass interception coefficient [= concentration in food (Bq/kg dry mass (DM) or fresh mass)/total deposition (Bq/m2)] is a key parameter for estimating radionuclide concentrations in crops after the deposition of radionuclides on plant stands. However, such data are still sparse, especially for radiostrontium (89Sr and 90Sr). To enhance the mass interception coefficient data for leafy crops, we used global fallout 90Sr data in leafy crops harvested in 1963-1965 and the deposition data for the corresponding crop growing period. Geometric mean values of the mass interception coefficient of 90Sr for leafy crops were 2.8 m2 kg-1 DM for spinach, 0.60 m2 kg-1 DM for cabbage, and 1.3 m2 kg-1 DM for Chinese cabbage. For comparison, we measured naturally occurring 7Be in giant butterbur leaves, and the results showed that the data were similar to those of 90Sr for spinach. These data were similar to the previously obtained data by single spike radiotracer experiments. Therefore, in the case of nuclear emergency situations, mass interception coefficient data obtained using global fallout 90Sr and/or naturally occurring 7Be should be valuable to estimate radioactivity contamination levels of radiostrontium directly deposited on leafy crops.