High purity 47Sc production using high-energy photons and natural vanadium targets.

Scandium-47 (47Sc) is of high value for targeted radiotherapy and theranostics; we report a novel, cost-effective approach to produce high-purity 47Sc via photonuclear reactions with natural vanadium. Irradiation at 20 MeV photon end-point energy produces >99.998% pure 47Sc, while irradiation at 38 MeV produces 98.8 ± 1.6% pure 47Sc. Experimental data suggest producing greater than 100 mCi (3700 MBq) of 47Sc using this approach may be feasible. Future research into refinement and scale-up to support pre-clinical research is recommended.

Rapid Separation of Photofissioned Uranium Products via a Single-Pass Multiplexed Chromatographic Fission Product Separation System.

Current state-of-the-art fission product separations frequently involve multiple independent separation columns and sample manipulation processes; to couple these processes together, multiple evaporation and transposition steps are often required. The addition of these steps results in lengthy separation times, increased analysis costs, the potential for sample loss, and release of radioactive contamination. We report a new semiautomated method for the rapid separation of U, Zr, Mo, Ba, Sr, Te, and lanthanide fission products from irradiated uranium samples. Chemical yields for U, Zr, Ba, Sr, Te and the lanthanides from less than 3-day old uranium fission product samples are consistently greater than 90%, while those of Mo are greater than 70%. This method minimizes the use and addition of oxidation and reduction reagents that often cause issues with retention and separation. Uranium dissolution and fission product separations using this single-pass method are achievable in under 2 h, representing a significant improvement over traditional gravimetric uranium fission product separation procedures.

Carbon-14 content in surface soils near atmospheric and below ground nuclear detonations.

Global and regional releases of 14C have resulted from nuclear weapons testing activities; assessment of the chemical behavior and mechanisms of environmental transport and deposition of this radionuclide can assist remediation strategy development efforts and provide insights into global carbon cycling processes. This work reports a systematic evaluation of 14C in surface soils taken from the Nevada National Security Site. Surface soil samples are derived from above- and underground test locations, with underground test sites representing a range from near complete containment to uncontrolled radioactive releases. Only one surface soil taken from a underground test location (i.e. the Baneberry shot) shows elevated 14C concentrations (319 ±â€¯9 pMC) in addition to elevated concentrations of 137Cs, 60Co and 152Eu above regional backgrounds. Surface soils from above-ground test locations show extremely high 14C content (~1000 to 10,000 pMC); elevated concentrations of 152Eu and 60Co for these soils are also observed, with 137Cs at or below background levels. Taken together, these data suggest that 14C in surface soils from above-ground tests is primarily derived from in-situ neutron activation of the native soil material, whereas 14C in surface soils from underground tests may be from either recondensed particulate material or soil activation.

237Np analytical method using 239Np tracers and application to a contaminated nuclear disposal facility.

Environmental 237Np analyses are challenged by low 237Np concentrations and lack of an available yield tracer; we report a rapid, inexpensive 237Np analytical approach employing the short lived 239Np (t1/2 = 2.3 days) as a chemical yield tracer followed by 237Np quantification using inductively coupled plasma-mass spectrometry. 239Np tracer is obtained via separation from a 243Am stock solution and standardized using gamma spectrometry immediately prior to sample processing. Rapid digestions using a commercial, 900 W "Walmart" microwave and Parr microwave vessels result in 99.8 ± 0.1% digestion yields, while chromatographic separations enable Np/U separation factors on the order of 106 and total Np yields of 95 ± 4% (2σ). Application of this method to legacy soil samples surrounding a radioactive disposal facility (the Subsurface Disposal Area at Idaho National Laboratory) reveal the presence of low level 237Np contamination within 600 m of this site, with maximum 237Np concentrations on the order of 103 times greater than nuclear weapons testing fallout levels.

Extraction chromatographic separations of tantalum and tungsten from hafnium and complex matrix constituents.

Tantalum (Ta), hafnium (Hf), and tungsten (W) analyses from complex matrices require high purification of these analytes from each other and major/trace matrix constituents, however, current state-of-the-art Ta/Hf/W separations rely on traditional anion exchange approaches that show relatively similar distribution coefficient (Kd) values for each element. This work reports an assessment of three commercially available extraction chromatographic resins (TEVA, TRU, and UTEVA) for Ta/Hf/W separations. Batch contact studies show differences in Ta/Hf and Ta/W Kd values of up to 106 and 104 (respectively), representing an improvement of a factor of 100 and 300 in Ta/Hf and Ta/W Kd values (respectively) over AG1×4 resin. Variations in the Kd values as a function of HCl concentration for TRU resin show that this resin is well suited for Ta/Hf/W separations, with Ta/Hf, Ta/W, and W/Hf Kd value improvements of 10, 200, and 30 (respectively) over AG1×4 resin. Analyses of digested soil samples (NIST 2710a) using TRU resin and tandem TEVA-TRU columns demonstrate the ability to achieve extremely high purification (>99%) of Ta and W from each other and Hf, as well as enabling very high purification of Ta and W from the major and trace elemental constituents present in soils using a single chromatographic step.

Fukushima Daiichi reactor source term attribution using cesium isotope ratios from contaminated environmental samples.

RATIONALE: Source term attribution of environmental contamination following the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster is complicated by a large number of possible similar emission source terms (e.g. FDNPP reactor cores 1-3 and spent fuel ponds 1-4). Cesium isotopic analyses can be utilized to discriminate between environmental contamination from different FDNPP source terms and, if samples are sufficiently temporally resolved, potentially provide insights into the extent of reactor core damage at a given time. METHODS: Rice, soil, mushroom, and soybean samples taken 100-250 km from the FDNPP site were dissolved using microwave digestion. Radiocesium was extracted and purified using two sequential ammonium molybdophosphate-polyacrylonitrile columns, following which (135)Cs/(137) Cs isotope ratios were measured using thermal ionization mass spectrometry (TIMS). Results were compared with data reported previously from locations to the northwest of FDNPP and 30 km to the south of FDNPP. RESULTS: (135)Cs/(137)Cs isotope ratios from samples 100-250 km to the southwest of the FDNPP site show a consistent value of 0.376 ± 0.008. (135)Cs/(137)Cs versus (134)Cs/(137)Cs correlation plots suggest that radiocesium to the southwest is derived from a mixture of FDNPP reactor cores 1, 2, and 3. Conclusions from the cesium isotopic data are in agreement with those derived independently based upon the event chronology combined with meteorological conditions at the time of the disaster. CONCLUSIONS: Cesium isotopic analyses provide a powerful tool for source term discrimination of environmental radiocesium contamination at the FDNPP site. For higher precision source term attribution and forensic determination of the FDNPP core conditions based upon cesium, analyses of a larger number of samples from locations to the north and south of the FDNPP site (particularly time-resolved air filter samples) are needed.

(135)Cs/(137)Cs isotopic composition of environmental samples across Europe: Environmental transport and source term emission applications.

(135)Cs/(137)Cs isotopic analyses represent an important tool for studying the fate and transport of radiocesium in the environment; in this work the (135)Cs/(137)Cs isotopic composition in environmental samples taken from across Europe is reported. Surface soil and vegetation samples from western Russia, Ukraine, Austria, and Hungary show consistent aged thermal fission product (135)Cs/(137)Cs isotope ratios of 0.58 ± 0.01 (age corrected to 1/1/15), with the exception of one sample of soil-moss from Hungary which shows an elevated (135)Cs/(137)Cs ratio of 1.78 ± 0.12. With the exception of the outlier sample from Hungary, surface soil/vegetation data are in quantitative agreement with values previously reported for soils within the Chernobyl exclusion zone, suggesting that radiocesium at these locations is primarily composed of homogenous airborne deposition from Chernobyl. Seawater samples taken from the Irish Sea show (135)Cs/(137)Cs isotope ratios of 1.22 ± 0.11 (age corrected to 1/1/15), suggesting aged thermal fission product Cs discharged from Sellafield. The differences in (135)Cs/(137)Cs isotope ratios between Sellafield, Chernobyl, and global nuclear weapons testing fallout indicate that (135)Cs/(137)Cs isotope ratios can be utilized to discriminate between and track radiocesium transport from different nuclear production source terms, including major emission sources in Europe.

Mechanical environmental transport of actinides and ¹³7Cs from an arid radioactive waste disposal site.

Aeolian and pluvial processes represent important mechanisms for the movement of actinides and fission products at the Earth's surface. Soil samples taken in the early 1970's near a Department of Energy radioactive waste disposal site (the Subsurface Disposal Area, SDA, located in southeastern Idaho) provide a case study for studying the mechanisms and characteristics of environmental actinide and (137)Cs transport in an arid environment. Multi-component mixing models suggest actinide contamination within 2.5 km of the SDA can be described by mixing between 2 distinct SDA end members and regional nuclear weapons fallout. The absence of chemical fractionation between (241)Am and (239+240)Pu with depth for samples beyond the northeastern corner and lack of (241)Am in-growth over time (due to (241)Pu decay) suggest mechanical transport and mixing of discrete contaminated particles under arid conditions. Occasional samples northeast of the SDA (the direction of the prevailing winds) contain anomalously high concentrations of Pu with (240)Pu/(239)Pu isotopic ratios statistically identical to those in the northeastern corner. Taken together, these data suggest flooding resulted in mechanical transport of contaminated particles into the area between the SDA and a flood containment dike in the northeastern corner, following which subsequent contamination spreading in the northeastern direction resulted from wind transport of discrete particles.

137Cs activities and 135Cs/137Cs isotopic ratios from soils at Idaho National Laboratory: a case study for contaminant source attribution in the vicinity of nuclear facilities.

Radiometric and mass spectrometric analyses of Cs contamination in the environment can reveal the location of Cs emission sources, release mechanisms, modes of transport, prediction of future contamination migration, and attribution of contamination to specific generator(s) and/or process(es). The Subsurface Disposal Area (SDA) at Idaho National Laboratory (INL) represents a complicated case study for demonstrating the current capabilities and limitations to environmental Cs analyses. (137)Cs distribution patterns, (135)Cs/(137)Cs isotope ratios, known Cs chemistry at this site, and historical records enable narrowing the list of possible emission sources and release events to a single source and event, with the SDA identified as the emission source and flood transport of material from within Pit 9 and Trench 48 as the primary release event. These data combined allow refining the possible number of waste generators from dozens to a single generator, with INL on-site research and reactor programs identified as the most likely waste generator. A discussion on the ultimate limitations to the information that (135)Cs/(137)Cs ratios alone can provide is presented and includes (1) uncertainties in the exact date of the fission event and (2) possibility of mixing between different Cs source terms (including nuclear weapons fallout and a source of interest).

Neptunium(V) sorption to goethite at attomolar to micromolar concentrations.

Sorption of 10(-18)-10(-5)M neptunium (Np) to goethite was examined using liquid scintillation counting and gamma spectroscopy. A combination approach using (239)Np and long lived (237)Np was employed to span this wide concentration range. (239)Np detection limits were determined to be 2×10(-18)M and 3×10(-17)M for liquid scintillation counting and gamma spectroscopy, respectively. Sorption was found to be linear below 10(-11)M, in contrast to the non-linear behavior observed at higher concentrations both here and in the literature. 2-site and 3-site Langmuir models were used to simulate sorption behavior over the entire 10(-18)-10(-5)M range. The 3-site model fit yielded Type I and II site densities of 3.56 sites/nm(2) (99.6%) and 0.014±0.007 sites/nm(2) (0.4±0.1%), consistent with typical "high affinity" and "low affinity" sites reported in the literature [21]. Modeling results for both models suggest that sorption below ~10(-11)M is controlled by a third (Type III) site with a density on the order of ~7×10(-5)sites/nm(2) (~0.002%). While the nature of this "site" cannot be determined from isotherm data alone, the sorption data at ultra-low Np concentrations indicate that Np(V) sorption to goethite at environmentally relevant concentrations will be (1) linear and (2) higher than previous (high concentration) laboratory experiments suggest.