Determination of 93Mo in Radioactive Samples of Sulfuric Acid Media from Nuclear Facilities.

93Mo is an important radionuclide in view of radioactive waste repository because of its long half-life and high mobility in the environment. 93Mo decays by electron capture without any measurable gamma ray emission. The concentration of 93Mo in most of the radioactive waste is many orders of magnitude lower than the major activation product radionuclides, which makes the accurate determination of 93Mo a big challenge. A new analytical method for the determination of 93Mo in sulfuric acid media from nuclear power reactor was developed. 93Mo was separated from most of the radionuclides by cation exchange chromatography followed by the removal of sulfate by CaSO4 precipitation. A further purification of 93Mo, especially from anion species of 51Cr and 125Sb, was achieved by anion exchange chromatography and a short alumina column separation. The chemical yield of 93Mo in the entire separation procedure reached about 75%, and the decontamination factors for all potential interfering radionuclides were 1.5 × 106-1.6 × 108. The purified 93Mo was measured by liquid scintillation counting through counting its low-energy Auger electrons. A detection limit of 2 mBq/g for 93Mo in 50 g sample was achieved by this method, which enables the quantitative determination of 93Mo in most of the radioactive samples in the decommissioning waste and coolant water of nuclear power reactors. The developed method has been successfully applied to determine 93Mo in coolant water of nuclear power reactors, providing a robust analytical approach of 93Mo for the radiological characterization of radioactive wastes.

Distribution of Anthropogenic 129I in the Western South China Sea and Its Application for Tracing the Sources and Movement of Pollution.

Anthropogenic 129I has been dispersed all over the world and could be utilized as an oceanographic tracer based on its conservative nature in the ocean. The first datasets of 129I and 127I were obtained by analysis of seawater of 36 water columns collected in the western South China Sea during August-September 2018. The measured 129I concentrations decreased with depth from (0.93-1.61) × 107 atoms/L in the upper 200 m to (0.04-0.14) × 107 atoms/L at 1500 m, indicating a clear anthropogenic source in the upper layer, mainly originated from the global fallout. The riverine input of the deposited 129I on the catchment area of the Mekong River is an important source besides the direct deposition in the seas. The water mass with high 129I from the Mekong River water moves to the east at 11°N by the North Nansha Current in the surface layer (2-25 m). The exponentially decreasing 129I level with depth indicates that the vertical dispersion of 129I from the upper to the lower layer was mainly through slow diffusion, and the deep water at more than 1500 m was not significantly contaminated by the upper layer water at least in the past 70 years.

Determination of 241Am in Environmental Samples: A Review.

The determination of 241Am in the environment is of importance in monitoring its release and assessing its environmental impact and radiological risk. This paper aims to give an overview about the recent developments and the state-of-art analytical methods for 241Am determination in environmental samples. Thorough discussions are given in this paper covering a wide range of aspects, including sample pre-treatment and pre-concentration methods, chemical separation techniques, source preparation, radiometric and mass spectrometric measurement techniques, speciation analyses, and tracer applications. The paper focuses on some hyphenated separation methods based on different chromatographic resins, which have been developed to achieve high analytical efficiency and sample throughput for the determination of 241Am. The performances of different radiometric and mass spectrometric measurement techniques for 241Am are evaluated and compared. Tracer applications of 241Am in the environment, including speciation analyses of 241Am, and applications in nuclear forensics are also discussed.

On the Quality Control for the Determination of Ultratrace-Level 236U and 233U in Environmental Samples by Accelerator Mass Spectrometry.

Our recent attempt to determine ultratrace-level 236U and 233U in small-volume seawater samples was challenged by high and unstable procedure blanks in our environmental radioactivity laboratory, which used to be a spent fuel research facility. Through intercomparison experiments with different laboratories and background checks on the chemical reagents and laboratory dust, the resuspended U-bearing dust was identified as the dominating source of the 236U and 233U contamination. With the implementation of background control (especially dust control) measures, the procedure blanks and detection limits of 236U and 233U for the radiochemical separation procedure have been significantly improved by three orders of magnitudes. With well-controlled blanks, the analytical precision for 236U and 233U predominantly relies on the AMS counting statistics. Background check and dust control are strongly recommended before the analyses of environmental-level long-lived radionuclides (such as 236U and 233U) that are conducted in the former or active nuclear facilities, even if clearance of radioactivity relevant for radioprotection was achieved.

High-Resolution Tritium Profile in an Ice Core from Camp Century, Greenland.

We measure 3H in an ice core from Camp Century. The temporal distribution of 3H concentration in the ice core corresponds generally well with the historical record of explosive yields of atmospheric nuclear weapons tests. Maximum 3H values observed in 1962-1963 are comparable to those in ice core or precipitation in many other locations in the Northern Hemisphere. There is no indication that significant 3H contamination was locally released into the air during the operation of the Camp Century reactor. It is, however, somewhat surprising that several prominent 3H peaks are still observed after 1980. We suggest that these are associated with airborne 3H releases from the civil nuclear industry. A wavelet analysis during 1970-2017 indicates the primary frequency of variability in the 3H record is annual 3H peaks. These annual peaks can be combined with the 3H spikes from global fallout of known nuclear weapons tests to benchmark and evaluate theoretical ice core dating scales back to the 1950s. A positive correlation is observed between annual 3H average concentration and variability of Arctic Oscillation (AO). This highlights the value of 3H as a potential tracer for air masses and airborne pollutants in the Arctic.

70-Year Anthropogenic Uranium Imprints of Nuclear Activities in Baltic Sea Sediments.

A strongly stratified water structure and a densely populated catchment make the Baltic Sea one of the most polluted seas. Understanding its circulation pattern and time scale is essential to predict the dynamics of hypoxia, eutrophication, and pollutants. Anthropogenic 236U and 233U have been demonstrated as excellent transient tracers in oceanic studies, but unclear input history and inadequate long-term monitoring records limit their application in the Baltic Sea. From two dated Baltic sediment cores, we obtained high-resolution records of anthropogenic uranium imprints originating from three major human nuclear activities throughout the Atomic Era. Using the novel 233U/236U signature, we distinguished and quantified 236U inputs from global fallout (45.4-52.1%), Chernobyl accident (0.3-1.8%), and discharges from civil nuclear industries (46.1-54.3%) to the Baltic Sea. We estimated the total release of 233U (7-15 kg) from the atmospheric nuclear weapon testing and pinpointed the 233U peak signal in the mid-to-late 1950s as a potential time marker for the onset of the Anthropocene Epoch. This work also provides fundamental 236U data on Chernobyl accident and early discharges from civil nuclear facilities, prompting worldwide 233U-236U tracer studies. We anticipate our data to be used in a broader application in model-observation interdisciplinary research on water circulation and pollutant dynamics in the Baltic Sea.

Determination of Ultralow Level 135Cs and 135Cs/137Cs Ratio in Environmental Samples by Chemical Separation and Triple Quadrupole ICP-MS.

An analytical method was developed for the determination of ultralow level 135Cs in environmental samples by chromatographic separation of cesium with AMP-PAN and AG50W-X8 columns and sensitive measurement of cesium isotopes with triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS). Cesium was simply released by acid leaching using aqua regia from environmental solid samples and preconcentrated on AMP-PAN column. The cesium adsorbed on the column was effectively eluted with NH4Cl solution without dissolving the AMP. The excessive amount of NH4Cl in the eluate was removed by sublimation in the presence of small amount of LiCl. The remaining barium and other interfering elements such as Mo, Sn, Sb, and Li were efficiently removed using cation exchange chromatography (AG50W-X8). The decontamination factors of this procedure are above 4 × 107 for barium and 4 × 105 for molybdenum; the chemical yields of cesium are more than 85% for samples of less than 10 g. This method enables to separate cesium from large size of samples for the determination of ultralow level 135Cs, avoiding the problem of removal of a huge amount of Mo in the dissolved AMP. Intrinsic 137Cs in the environmental samples measured by gamma spectrometry before and after separation was used as internal isotope dilution standard for quantitative determination of 135Cs without complete release and recover of radiocesium. The interference of barium (135Ba and 137Ba) to the ICP-MS measurement of 135Cs and 137Cs was further suppressed to 8 × 10-5 by using N2O as the reaction gas in ICP-MS/MS at a flow rate of 0.7 mL/min, so a total suppression of 2 × 10-12 for Ba was achieved, making the isobaric interference of Ba isotopes to the measurement of 135Cs and 137Cs in environmental samples negligible. A detection limit of 9.1 × 10-17 g/g for 135Cs and 137Cs was achieved for 60 g samples. The developed method was validated by analysis of standard reference materials (IAEA-375, IAEA-330, and IAEA-385) and successfully applied for the determination of 135Cs concentrations and 135Cs/137Cs ratios in soil samples collected from Denmark, Sweden, and Ukraine. The 135Cs/137Cs isotopic ratios in Danish soil (2.08-2.68) were significantly higher than that from Sweden and Ukraine (0.65-0.71), indicating different sources of radiocesium. This work demonstrated the application of 135Cs/137Cs as a unique fingerprint for discriminating the sources of radioactive contamination and estimating their contribution to the total inventory, which will be useful for nuclear forensics and environmental tracer studies.

Determination of Ultratrace Level 135Cs and 135Cs/137Cs Ratio in Small Volume Seawater by Chemical Separation and Thermal Ionization Mass Spectrometry.

The atomic ratio of 135Cs/137Cs is a powerful fingerprint for distinguishing the source terms of radioactive contamination and tracing the circulation of water masses in the ocean. However, the determination of the 135Cs/137Cs ratio is very difficult due to the ultratrace level of 135Cs (<0.02 mBq/m3) and 137Cs (<2 Bq/m3) in the ordinary seawater samples. In this work, a sensitive method was developed for determination of 135Cs concentration and 135Cs/137Cs ratio in seawater using chemical separation combined with thermal ionization mass spectrometry (TIMS) measurement. Cesium was first preconcentrated from seawater using ammonium molybdophosphate-polyacrylonitrile column chromatography and then purified using cation exchange chromatography to remove the interferences. With this method, decontamination factors of 6.0 × 106 for barium and 1800 for rubidium and a chemical yield of more than 60% for cesium were achieved. By using glucose as an activator, the ionization efficiency of cesium was significantly improved to 50.6%, and a constant high current of Cs+ (20 V) can be maintained for more than 180 min, which ensures sensitive and reliable measurement of low level 135Cs and 137Cs. Detection limits of 4.0 × 10-17 g/L for both 135Cs and 137Cs for 200 mL seawater were achieved, which enables the accurate determination of 135Cs concentration and 135Cs/137Cs ratio in a small volume of seawater samples (<200 mL). The developed method has been validated by analysis of seawater reference material IAEA-443. Seawater samples collected from the Greenland Sea, Baltic Sea, and Danish Straits have been successfully analyzed for 135Cs concentrations and 135Cs/137Cs ratios, and the results showed that 135Cs concentrations in the seawater of the Baltic Sea is much higher than that in the Greenland Sea, which is attributed to the high deposition of Chernobyl accident derived radiocesium in the Baltic Sea region.

Dynamic Flow Approaches for Automated Radiochemical Analysis in Environmental, Nuclear and Medical Applications.

Automated sample processing techniques are desirable in radiochemical analysis for environmental radioactivity monitoring, nuclear emergency preparedness, nuclear waste characterization and management during operation and decommissioning of nuclear facilities, as well as medical isotope production, to achieve fast and cost-effective analysis. Dynamic flow based approaches including flow injection (FI), sequential injection (SI), multi-commuted flow injection (MCFI), multi-syringe flow injection (MSFI), multi-pumping flow system (MPFS), lab-on-valve (LOV) and lab-in-syringe (LIS) techniques have been developed and applied to meet the analytical criteria under different situations. Herein an overall review and discussion on these techniques and methodologies developed for radiochemical separation and measurement of various radionuclides is presented. Different designs of flow systems with combinations of radiochemical separation techniques, such as liquid-liquid extraction (LLE), liquid-liquid microextraction (LLME), solid phase extraction chromatography (SPEC), ion exchange chromatography (IEC), electrochemically modulated separations (EMS), capillary electrophoresis (CE), molecularly imprinted polymer (MIP) separation and online sensing and detection systems, are summarized and reviewed systematically.

Anthropogenic 236U in Danish Seawater: Global Fallout versus Reprocessing Discharge.

This work focuses on the occurrence of 236U in seawater along Danish coasts, which is the sole water-exchange region between the North Sea-Atlantic Ocean and the Baltic Sea. Seawater collected in 2013 and 2014 were analyzed for 236U (as well as 238U and 137Cs). Our results indicate that 236U concentrations in Danish seawater are distributed within a relatively narrow range of (3.6-8.2) × 107 atom/L and, to a certain extent, independent of salinity. 236U/238U atomic ratios in Danish seawater are more than 4 times higher than the estimated global fallout value of 1× 10-9. The levels of 236U/238U atomic ratios obtained are comparable to those reported for the open North Sea and much higher than several other open oceans worldwide. This indicates that besides the global fallout input, the discharges from the two major European nuclear reprocessing plants are dominating sources of 236U in Danish seawater. However, unexpectedly high 236U/238U ratios as well as high 236U concentrations were observed at low-salinity locations of the Baltic Sea. While this feature might be interpreted as a clue for another significant 236U input in the Baltic Sea, it may also be caused by the complexity of water currents or slow turnover rate.

Analysis of Technetium Species and Fractions in Natural Seaweed Using Biochemical Separation and ICP-MS Measurement.

An extremely high accumulation and retention of technetium in marine plants, especially brown seaweed, makes it a unique bioindicator of technetium. In the present work, a novel approach was developed for the speciation analysis of technetium in seaweed, wherein a series of biochemical separations was exploited to isolate different species of technetium. Inductively coupled plasma mass spectrometry (ICP-MS) was applied for the measurement of 99Tc after thorough radiochemical preconcentration and purification. The results show that the distribution of technetium species in seaweed is relatively dispersive. Besides the inorganic species of TcO4-, most of technetium (>75%) combined with organic components of seaweed such as algin, cellulose, and pigment. This investigation could provide important fundamental knowledge for studying the processes and mechanisms of 99Tc accumulation in the natural seaweed.

Method for (236)U Determination in Seawater Using Flow Injection Extraction Chromatography and Accelerator Mass Spectrometry.

An automated analytical method implemented in a flow injection (FI) system was developed for rapid determination of (236)U in 10 L seawater samples. (238)U was used as a chemical yield tracer for the whole procedure, in which extraction chromatography (UTEVA) was exploited to purify uranium, after an effective iron hydroxide coprecipitation. Accelerator mass spectrometry (AMS) was applied for quantifying the (236)U/(238)U ratio, and inductively coupled plasma mass spectrometry (ICPMS) was used to determine the absolute concentration of (238)U; thus, the concentration of (236)U can be calculated. The key experimental parameters affecting the analytical effectiveness were investigated and optimized in order to achieve high chemical yields and simple and rapid analysis as well as low procedure background. Besides, the operational conditions for the target preparation prior to the AMS measurement were optimized, on the basis of studying the coprecipitation behavior of uranium with iron hydroxide. The analytical results indicate that the developed method is simple and robust, providing satisfactory chemical yields (80-100%) and high analysis speed (4 h/sample), which could be an appealing alternative to conventional manual methods for (236)U determination in its tracer application.

Rapid multisample analysis for simultaneous determination of anthropogenic radionuclides in marine environment.

An automated multisample processing flow injection (FI) system was developed for simultaneous determination of technetium, neptunium, plutonium, and uranium in large volume (200 L) seawater. Ferrous hydroxide coprecipitation was used for the preliminary sample treatment providing the merit of simultaneous preconcentration of all target radionuclides. Technetium was separated from the actinides via valence control of technetium (as Tc(VII)) in a ferric hydroxide coprecipitation. A novel preseparation protocol between uranium and neptunium/plutonium fractions was developed based on the observation of nearly quantitative dissolution of uranium in 6 mol/L sodium hydroxide solution. Automated extraction (TEVA for technetium and UTEVA for uranium) and anion exchange (AGMP-1 M for plutonium and neptunium) chromatographic separations were performed for further purification of each analyte within the FI system where four samples were processed in parallel. Analytical results indicate that the proposed method is robust and straightforward, providing chemical yields of 50-70% and improved sample throughput (3-4 d/sample). Detection limits were 8 mBq/m(3) (0.013 pg/L), 0.26 µBq/m(3) (0.010 fg/L), 23 µBq/m(3) (0.010 fg/L), 84 µBq/m(3) (0.010 fg/L) and 0.6 mBq/m(3) (0.048 ng/L) for (99)Tc, (237)Np, (239)Pu, (240)Pu and (238)U for 200 L seawater, respectively. The unique feature of multiradionuclide and multisample simultaneous processing vitalizes the developed method as a powerful tool in obtaining reliable data with reduced analytical cost in both radioecology studies and nuclear emergency preparedness.

Half-century trends of radioactivity in fish from Danish areas of the North Sea, Kattegat, and Baltic Sea.

This work reports comprehensive time-series datasets over the past 50 years for natural (210Po) and anthropogenic (134Cs and 137Cs) radionuclides in three fish species (cod, herring and plaice) from Danish marine areas covering the North Sea, Kattegat, and Baltic Sea. Impact from the global fallout of atmospheric nuclear weapons testing, radioactive discharges from the European nuclear reprocessing plants and release from Chernobyl accident are clearly detected in the fish samples. While 210Po concentrations in each fish species demonstrated comparable levels across the three regions without notable temporal trends, significantly higher median 210Po concentration was observed in the lower trophic level fish, namely herring and plaice, compared to cod. In contrast, 137Cs concentrations in all three species steadily decrease over time after the Chernobyl-attributed peaks in late 1980s in the entire study area, whereas 137Cs always demonstrated higher concentrations in cod than herring and plaice. Our calculated concentration factors (CFs) for 137Cs in this work indicate that the mean CFs for 137Cs over the past 50 years are significantly different across the three species, following the order of cod < herring < plaice. Based on the time-series data, ecological half-lives (Teco) of 137Cs in fish from Danish marine areas were estimated to evaluate the long-term impact of anthropogenic radioactive contamination in different regions. Our results indicate no significant difference in Teco across different fish species, whereas the weighted mean Teco for fish in the Baltic Sea (29.3 ± 3.9 y) is significantly longer than those of the North Sea (9.8 ± 0.9 y) and Kattegat (11.7 ± 1.2 y), reflecting the strong 'memory effect' of the Baltic Sea due to its slow water renewal. However, the dose assessment demonstrates that the contribution of the natural radionuclide 210Po to ingestion dose from fish consumption is 1-2 order of magnitude higher compared to that of 137Cs.

Vertical distribution of 241Am in the southern Baltic Sea sediment profiles.

The contamination of the Baltic Sea with radioactive substances occurred due to the global fallout of atmospheric nuclear weapon tests and the Chernobyl disaster. The knowledge of 241Am in the sediments of the Baltic Sea is limited. Thus, this study aimed to determine 241Am in sediment cores collected from the southern Baltic Sea. Time-based distributions were derived from age-depth profiles using the 210Pb dating method and further corroborated by 137Cs profiles. The activities of 241Am were measured by alpha spectrometry after radiochemical purification. The results show divergences in the concentrations of 241Am at the local level, varying from 0.017 ± 0.001 Bq·kg-1 at the Gotland Basin station to 3.19 ± 0.23 Bq·kg-1 in the Gdansk Basin. These findings enhance our understanding of the radioactive contamination levels in the Baltic Sea and serve as a crucial reference dataset for future assessments and management strategies to mitigate the environmental impact of radionuclides in the region.

Method for determination of neptunium in large-sized urine samples using manganese dioxide coprecipitation and 242Pu as yield tracer.

A novel method for bioassay of large volumes of human urine samples using manganese dioxide coprecipitation for preconcentration was developed for rapid determination of (237)Np. (242)Pu was utilized as a nonisotopic tracer to monitor the chemical yield of (237)Np. A sequential injection extraction chromatographic (SI-EC) system coupled with inductively coupled plasma mass spectrometry (ICPMS) was exploited to facilitate the rapid column separation and quantification. The analytical results demonstrated satisfactory performance of the MnO(2) coprecipitation as indicated by the high chemical yields close to 100% and high separation capacity of processing up to 5 L of human urine samples. The MnO(2) coprecipitation process is simple and straightforward in which a batch (8-12) of samples can be pretreated within 4 h (i.e., <0.5 h/sample). In connection with the automated column separation and ICPMS quantification, which takes less than 1.5 h in total, the overall analytical time was on average less than 2 h for each sample. The high effectiveness and sample throughput make the developed method well suited for urine bioassay of (237)Np in routine monitoring of occupationally internal radiation exposure and rapid analysis of neptunium contamination level for emergency preparedness.

Bead injection extraction chromatography using high-capacity lab-on-valve as a front end to inductively coupled plasma mass spectrometry for urine radiobioassay.

A novel bead injection (BI) extraction chromatographic microflow system exploiting a high-capacity lab-on-valve (LOV) platform coupled with inductively coupled plasma mass spectrometric detection is developed for rapid and automated determination of plutonium in human urine. A column attached to the LOV processing unit is loaded online with a metered amount of disposable extraction chromatographic resin (up to 330 mg of TEVA (abbreviation for tetravalent actinides)) through programmable beads transport. Selective capture and purification of plutonium onto the resin beads is then performed by pressure driven flow after preliminary sample pretreatment. The analytical results demonstrate the large capacity of bead surfaces for uptake of Pu within the tailor-made LOV platform that fosters processing of large-sized biological samples, e.g., 1 L of human urine, along with good reproducibility for automatic column renewal (0.319 ± 0.004 g, n = 5). The chemical yields of plutonium were averagely better than 90% under the optimal experimental conditions, and the entire analytical procedure could be accomplished within a short time frame (<3 h) as compared to manual counterparts (1-2 days). Therefore, the developed system is well suited for expedient analysis of low-level plutonium in urine of exposed individuals as required in emergency situations.

Sequential injection method for rapid and simultaneous determination of 236U, 237Np, and Pu isotopes in seawater.

An automated analytical method implemented in a novel dual-column tandem sequential injection (SI) system was developed for simultaneous determination of (236)U, (237)Np, (239)Pu, and (240)Pu in seawater samples. A combination of TEVA and UTEVA extraction chromatography was exploited to separate and purify target analytes, whereupon plutonium and neptunium were simultaneously isolated and purified on TEVA, while uranium was collected on UTEVA. The separation behavior of U, Np, and Pu on TEVA-UTEVA columns was investigated in detail in order to achieve high chemical yields and complete purification for the radionuclides of interest. (242)Pu was used as a chemical yield tracer for both plutonium and neptunium. (238)U was quantified in the sample before the separation for deducing the (236)U concentration from the measured (236)U/(238)U atomic ratio in the separated uranium target using accelerator mass spectrometry. Plutonium isotopes and (237)Np were measured using inductively coupled plasma mass spectrometry after separation. The analytical results indicate that the developed method is robust and efficient, providing satisfactory chemical yields (70-100%) of target analytes and relatively short analytical time (8 h/sample).

Sequential injection approach for simultaneous determination of ultratrace plutonium and neptunium in urine with accelerator mass spectrometry.

An analytical method was developed for simultaneous determination of ultratrace level plutonium (Pu) and neptunium (Np) using iron hydroxide coprecipitation in combination with automated sequential injection extraction chromatography separation and accelerator mass spectrometry (AMS) measurement. Several experimental parameters affecting the analytical performance were investigated and compared including sample preboiling operation, aging time, amount of coprecipitating reagent, reagent for pH adjustment, sedimentation time, and organic matter decomposition approach. The overall analytical results show that preboiling and aging are important for obtaining high chemical yields for both Pu and Np, which is possibly related to the aggregation and adsorption behavior of organic substances contained in urine. Although the optimal condition for Np and Pu simultaneous determination requires 5-day aging time, an immediate coprecipitation without preboiling and aging could also provide fairly satisfactory chemical yields for both Np and Pu (50-60%) with high sample throughput (4 h/sample). Within the developed method, (242)Pu was exploited as chemical yield tracer for both Pu and Np isotopes. (242)Pu was also used as a spike in the AMS measurement for quantification of (239)Pu and (237)Np concentrations. The results show that, under the optimal experimental condition, the chemical yields of (237)Np and (242)Pu are nearly identical, indicating the high feasibility of (242)Pu as a nonisotopic tracer for (237)Np determination in real urine samples. The analytical method was validated by analysis of a number of urine samples spiked with different levels of (237)Np and (239)Pu. The measured values of (237)Np and (239)Pu by AMS exhibit good agreement (R(2) ≥ 0.955) with the spiked ones confirming the reliability of the proposed method.

Simultaneous determination of femtogram levels of 237Np, 239Pu, and 240Pu in environmental solid samples using extraction chromatography and ICP-MS/MS.

An analytical method based on triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) was developed for simultaneous determination of femtogram levels of 237Np, 239Pu, and 240Pu in environmental samples. By carefully controlling the valence states of Np and Pu in the entire separation procedure using a simple single extraction chromatographic column (TK200), the consistent behavior of Np and Pu was achieved, allowing for the reliable application of 242Pu as the chemical yield tracer for 237Np, 239Pu, and 240Pu. A high decontamination factor of 3.2 × 107 for the most critical interfering element, uranium, was achieved in the chemical separation step. The interferences of 238U1H+ and peak tailing of 238U+ during the measurement of plutonium isotopes were effectively eliminated by utilizing 7.5 mL/min He-1.1 mL/min CO2 as reaction gases in the octupole collision/reaction cell and employing sequential quadrupole mode for mass separation in ICP-MS/MS. Specifically, the interference of 238U1H+ was reduced to 10-6 and the peak tailing of 238U+ to 10-10, surpassing the performance of measurement method without reaction gases by 3 orders of magnitude. The developed method enables the accurate determination of femtogram levels of 237Np, 239Pu, and 240Pu in the samples with U/Np and U/Pu atom ratios of up to 1017 and 1012, respectively. The developed method was validated by analyzing standard reference materials and spiked soil samples.