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This Review summarizes a range of analytical techniques that can be used to detect, quantify, and/or distinguish between isotopes of iodine (e.g., long-lived ¹²⁹I, short-lived ¹³¹I, stable ¹²⁷I). One reason this is of interest is that understanding potential radioiodine release from nuclear processes is crucial to prevent environmental contamination and to protect human health as it can incorporate into the thyroid leading to cancer. It is also of interest for evaluating iodine retention performances of next-generation iodine off-gas capture materials and long-term waste forms for immobilizing radioiodine for disposal in geologic repositories. Depending upon the form of iodine (e.g., molecules,more » elemental, and ionic) and the matter state (i.e., solid, liquid, and gaseous), the available options can vary. In addition, several other key parameters vary between the methods discussed herein, including the destructive vs nondestructive nature of the measurement process (including in situ vs ex situ measurement options), the analytical data collection times, and the amount of sample required for analysis.« less

Glass-bonded sodalite composite waste forms have been developed for the immobilization of liquid radioactive wastes resulting from off-gas treatment during aqueous reprocessing of used nuclear fuel, with a particular focus on 129I. The proposed composite waste form is comprised of aluminosilicate ceramic phases containing volatile radionuclides bonded with a glassy matrix. In this work, a suite of ten candidate low-temperature glass binders (ZnO-Bi2O3-based glasses and a Na2O-B2O3-SiO2 glass) were examined. Six glasses were mixed with caustic scrubber waste simulant previously converted into a sodalite-rich material (to provide glass fractions of 10 and 20 wt.%), uniaxially pressed into pellets, and sinteredmore » at 350 °C or 550 °C for 8 h in air. Iodine retention after heat treatment was assessed by neutron activation analysis, showing retention of 67-100 % of expected iodine. The aqueous durabilities of the resulting materials were then determined, following the ASTM C1308 standard test, showing iodine releases of 1 to 23 g m-2 after 4 d. The cumulative iodine release for the best performing system (a zinc-bismuth-borate glass binder) was <1 g m-2, and its iodine retention from processing was 67 %. The iodine releases compared favorably with other waste forms. In parallel, this best-performing composition was also consolidated via hot isostatic pressing (HIP) in a stainless-steel canister at 550 °C for 2 h under 100 MPa pressure. The HIPed sample was produced at the ~20 g scale and showed improved densification and minimal reaction with the canister.« less

In this second part of a multipaper series, we present results from outdoor aerial measurements of surrogate distributed gamma-ray sources. Here we detail the design, manufacture, and testing of 300 individual ~7 mCi Cu-64 sealed sources at the Washington State University (WSU) research reactor and their deployment in various source patterns (each comprising up to 100 point sources) during the aerial measurement campaign. We show the results of two such measurements, in which approximate source shapes and qualitative source intensities can be seen from the count rate versus position plots, even without performing reconstructions. We also detail our efforts inmore » ground-truthing the deployed sources and comparing measured gamma-ray data to model predictions. In particular, we compare measured versus expected count data using the Poisson deviance formalism of Part I to evaluate whether the fielded surrogate point-source arrays “look like” their truly continuous distributed source analogs. More generally, we find that the point-source array technique provides high source placement accuracy, relative ease of quantifying the true source configuration, scalability to source dimensions of ≲100 m, ease of reconfiguration and removal, and relatively low dose to personnel. Finally, we consider potential improvements and generalizations of the point-source array technique for future measurement campaigns.« less

Abstract Catalysts for the oxidation of NH ₃ are critical for the utilization of NH ₃ as a large‐scale energy carrier. Molecular catalysts capable of oxidizing NH ₃ to N ₂ are rare. This report describes the use of [Cp*Ru(P ^{t Bu} ₂ N ^Ph ₂ )( ¹⁵ NH ₃ )][BAr ^F ₄ ], (P ^{t Bu} ₂ N ^Ph ₂ =1,5‐di(phenylaza)‐3,7‐di(tert‐butylphospha)cyclooctane; Ar ^F =3,5‐(CF ₃ ) ₂ C ₆ H ₃ ), to catalytically oxidize NH ₃ to dinitrogen under ambient conditions. The cleavage of six N−H bonds and the formation of an N≡N bondmore » was achieved by coupling H ⁺ and e ⁻ transfers as net hydrogen atom abstraction (HAA) steps using the 2,4,6‐tri‐ tert ‐butylphenoxyl radical ( ^t Bu ₃ ArO ^. ) as the H atom acceptor. Employing an excess of ^t Bu ₃ ArO ^. under 1 atm of NH ₃ gas at 23 °C resulted in up to ten turnovers. Nitrogen isotopic ( ¹⁵ N) labeling studies provide initial mechanistic information suggesting a monometallic pathway during the N⋅⋅⋅N bond‐forming step in the catalytic cycle.« less

Catalysts for the oxidation of NH₃ will be critical to utilize NH₃ as a large-scale energy carrier. Molecular complexes have not been shown to catalyze the oxidation of NH₃ to N₂. We report Ru- catalyzed oxidation of ammonia to dinitrogen under ambient conditions using the molecular complex [Cp*Ru(P^tBu₂N^Ph₂)(¹⁵NH₃)][BAr^F₄]. Mediating the cleavage of six N-H bonds and the formation of an N≡N bond was achieved by coupling H⁺ and e^- transfers as net hydrogen atom abstraction steps using the 2,4,6-tri-tert-butylphenoxyl radical (^tBu₃ArO•) as the H atom acceptor. Employing an excess of ^tBu₃ArO• under 1 atm of NH₃ gas at 23 °Cmore » resulted in up to six turnovers. As a result, nitrogen isotopic (¹⁵N) labeling studies provide mechanistic insights to confirm the N≡N bond forming step in the catalytic cycle.« less