Behavior Of Iodine Research Articles

Iodine in Metal-Organic Frameworks at High Pressure.

Capture of highly volatile radioactive iodine is a promising application of metal-organic frameworks (MOFs), thanks to their high porosity with flexible chemical architecture. Specifically, strong charge-transfer binding of iodine to the framework enables efficient and selective iodine uptake as well as its long-term storage. As such, precise knowledge of the electronic structure of iodine is essential for a detailed modeling of the iodine sorption process, which will allow for rational design of iodophilic MOFs in the future. Here we probe the electronic structure of iodine in MOFs at variable iodine···framework interaction by Raman and optical absorption spectroscopy at high pressure ( P). The electronic structure of iodine in the straight channels of SBMOF-1 (Ca- sdb, sdb = 4,4'-sulfonyldibenzoate) is modified irreversibly at P > 3.4 GPa by charge transfer, marking a polymerization of iodine molecules into a 1D polyiodide chain. In contrast, iodine in the sinusoidal channels of SBMOF-3 (Cd- sdb) retains its molecular (I2) character up to at least 8.4 GPa. Such divergent high-pressure behavior of iodine in the MOFs with similar port size and chemistry illustrates adaptations of the electronic structure of iodine to channel topology and strength of the iodine···framework interaction, which can be used to tailor iodine-immobilizing MOFs.

Uptake and distribution of organo-iodine in deep-sea corals

Understanding iodine concentration, transport, and bioavailability is essential in evaluating iodine's impact to the environment and its effectiveness as an environmental biogeotracer. While iodine and its radionuclides have proven to be important tracers in geologic and biologic studies, little is known about transport of this element to the deep sea and subsequent uptake in deep-sea coral habitats. Results presented here on deep-sea black coral iodine speciation and iodine isotope variability provides key information on iodine behavior in natural and anthropogenic environments, and its geochemical pathway in the Gulf of Mexico. Organo-iodine is the dominant iodine species in the black corals, demonstrating that binding of iodine to organic matter plays an important role in the transport and transfer of iodine to the deep-sea corals. The identification of growth bands captured in high-resolution scanning electron images (SEM) with synchronous peaks in iodine variability suggest that riverine delivery of terrestrial-derived organo-iodine is the most plausible explanation to account for annual periodicity in the deep-sea coral geochemistry. Whereas previous studies have suggested the presence of annual growth rings in deep-sea corals, this present study provides a mechanism to explain the formation of annual growth bands. Furthermore, deep-sea coral ages based on iodine peak counts agree well with those ages derived from radiocarbon (14C) measurements. These results hold promise for developing chronologies independent of 14C dating, which is an essential component in constraining reservoir ages and using radiocarbon as a tracer of ocean circulation. Furthermore, the presence of enriched 129I/127I ratios during the most recent period of skeleton growth is linked to nuclear weapons testing during the 1960s. The sensitivity of the coral skeleton to record changes in surface water 129I composition provides further evidence that iodine composition and isotope variability captured in proteinaceous deep-sea corals is a promising geochronometer as well as an emerging tracer for continental material flux.

I2‐Triggered Reductive Generation of N‐Centered Iminyl Radicals: An Isatin‐to‐Quinoline Strategy for the Introduction of Primary Amides

AbstractAn efficient and alternative isatin‐to‐quinoline strategy illustrates the metal‐like behavior of molecular iodine in the N−O reduction of ketoxime acetates. This process involves N−O/C−N bond cleavages and C−C/C−N bond formation to furnish pharmacologically significant quinoline‐4‐carboxamide derivatives. In this process, metal catalysts and extra oxidants are unnecessary. Mechanistic studies confirm the crucial role of molecular iodine in the iminyl radical generation process, in that molecular iodine can catalyze single‐electron reduction coupling reactions in a manner similar to transition metals.magnified image

Thermodynamics of soluble fission products cesium and iodine in the Molten Salt Reactor

The present study describes the full thermodynamic assessment of the Li,Cs,Th//F,I system. The existing database for the relevant fluoride salts considered as fuel for the Molten Salt Reactor (MSR) has been extended with two key fission products, cesium and iodine. A complete evaluation of all the common-ion binary and ternary sub-systems of the LiF-ThF4-CsF-LiI-ThI4-CsI system has been performed and the optimized parameters are presented in this work. New equilibrium data have been measured using Differential Scanning Calorimetry and were used to assess the reciprocal ternary systems and confirm the extrapolated phase diagrams. The developed database significantly contributes to the understanding of the behaviour of cesium and iodine in the MSR, which strongly depends on their concentration and chemical form. Cesium bonded with fluorine is well retained in the fuel mixture while in the form of CsI the solubility of these elements is very limited. Finally, the influence of CsI and CsF on the physico-chemical properties of the fuel mixture was calculated as function of composition.

Objective image characterization of a spectral CT scanner with dual-layer detector

This work evaluated the performance of a detector-based spectral CT system by obtaining objective reference data, evaluating attenuation response of iodine and accuracy of iodine quantification, and comparing conventional CT and virtual monoenergetic images in three common phantoms. Scanning was performed using the hospital’s clinical adult body protocol. Modulation transfer function (MTF) was calculated for a tungsten wire and visual line pair targets were evaluated. Image noise power spectrum (NPS) and pixel standard deviation were calculated. MTF for monoenergetic images agreed with conventional images within 0.05 lp cm−1. NPS curves indicated that noise texture of 70 keV monoenergetic images is similar to conventional images. Standard deviation measurements showed monoenergetic images have lower noise except at 40 keV. Mean CT number and CNR agreed with conventional images at 75 keV. Measured iodine concentration agreed with true concentration within 6% for inserts at the center of the phantom. Performance of monoenergetic images at detector based spectral CT is the same as, or better than, that of conventional images. Spectral acquisition and reconstruction with a detector based platform represents the physical behaviour of iodine as expected and accurately quantifies the material concentration.

Chemoselective Oxidative Esterification and Iodocyclization of Hydroxyalkynyl Aldehydes

AbstractWe have described the chemoselective behavior of iodine in the oxidative esterification and electrophilic iodocyclization of hydroxyalkynyl aldehydes that contain a primary alcohol moiety. In the presence of an alcohol, which serves as the nucleophile and solvent, the reaction of the hydroxyalkynyl aldehydes and I2 proceeds through a hemiacetal species to give alkyl 4‐(3‐hydroxyalkynyl)benzoate esters. In CH2Cl2, these substrates undergo an electrophilic iodocyclization through a cyclic iodonium ion to provide a synthetic route for the formation of the bioactive dihydrofuran/pyran ring system.

Capture of Iodine Species in MIL-53(Al), MIL-120(Al), and HKUST-1(Cu) Periodic DFT and Ab-Initio Molecular Dynamics Studies

The potential use of three metal–organic frameworks (MIL-53(Al), MIL-120(Al) and HKUST-1(Cu)) to adsorb iodine species (I2 and ICH3), which can be released during a severe nuclear accident, is investigated using periodic dispersion density functional theory for the first time. Competitive adsorption of iodine in the presence of water molecules is also characterized for the hydrophilic HKUST-1(Cu). In the first step, we have found that the absolute values of interaction energies of I2 and ICH3 are higher in the hydrated form of HKUST-1(Cu) than in the dehydrated one, which is of very high interest for iodine trapping. In a second stage, iodine species are strongly adsorbed in MIL-53(Al) than in MIL-120(Al) and HKUST-1(Cu) MOFs and therefore this material could potentially trap iodine compounds. Moreover, we study the influence of the functionalization of the MIL-53(Al) organic linkers on the adsorption behavior of iodine and it turns out that the substitutions does not present a significant effect for this...

Study of iodine releases from epoxy and polyurethane paints under irradiation and development of a new model of iodine-Epoxy paint interactions for PHEBUS and PWR severe accident applications

A new model of iodine-Epoxy paint interaction under irradiation has been developed with new relevant data to better reproduce and predict how much iodine could be released in the environment in case of a severe accident in a Pressurized Water Reactor. Its application to the modelling of volatile iodine behaviour in PHEBUS-FPT-3 test is presented and shows that other phenomena might govern the iodine volatility in the mid and long term. A broader analysis of the gaseous iodine behaviour is finally presented, highlighting the need to identify and model new gaseous chemical reactions that might play a significant role on iodine volatility.

First-principle studies of radioactive fission productions of Cs/Sr/Ag/I adsorption on silicon carbide in HTGR

Silicon carbide (SiC) is one of the important fuel-element materials in high-temperature gas-cooled reactors (HTGRs), and learning the adsorption behavior of radioactive fission products on the SiC surface is essential for source-term analysis in HTGR. In this study, the adsorption behavior of cesium, strontium, silver, and iodine on β-SiC is investigated using first-principle calculations. We find that the interactions between the adatoms and SiC substrate are strong for all four types of nuclides with binding energy of approximately 1–3 eV. These results are confirmed again by analysis of the charge density difference and density of state. Furthermore, the adsorption rates of the four nuclides are obtained, and we explain that these nuclides display significant adsorption rate on the SiC surface but are not easily desorbed, which shows that the solid fission products have difficulty penetrating through the SiC. These results demonstrate that in HTGR, intact SiC could effectively obstruct the diffusion of fission products from the uranium dioxide in tri-isotropic (TRISO) particles to the primary circuit, which are first obtained in a micro perspective.

Organic and inorganic colloids impacting total iodine behavior in groundwater from the Datong Basin, China

The geochemical behaviors of colloids in aquifers played an important role in determining the fate of iodine in groundwater system. To decipher the impact of colloids on iodine mobilization in aquifers, three successive pore-sized colloids filtration (0.45μm, 30kDa and 5kDa) were conducted on in-situ during groundwater sampling. The results showed that the distribution ratios (f) of total iodine (IT) and iron in the dissolved solution (i.e., 5kDa ultrafiltered) were from 0.78 to 0.99 and from 0.56 to 0.94, respectively. Natural organic matter (NOM) in the colloidal fractions obtained the f values ranging from 0.14 to 1.00. The decreased Eh values from recharge area to discharge area indicated redox potential of groundwater system changed from oxidizing to reducing along groundwater flowpath, and interestingly, the corresponding iodine fractions in groundwater were decreasing in dissolved solution and increasing in colloidal fractions. Inverse correlation between Fe and DOC and positive correlation between iodine and DOC suggested the occurrence of reductive dissolution of iron oxyhydroxides and degradation of organic iodine in groundwater system. Iodine distribution increased in dissolved solution and decreased in colloids with pH increase. Moreover, as pH increased, f (Fe) and f (DOC) decreased in dissolved solution and increased in colloids. Relatively weak correlation of f (IT) with f (Fe) and strong relationship between f (IT) and f (DOC) in the large grain size fractions suggested the Fe-OM complexes controlled iodine distribution in groundwater, which depends on the presence of Fe bridges. Negligible association of iodine with Fe and NOM in the small grain size fractions might be attributed to the effects of abundant OH− content in groundwater.

First-principle studies of radioactive fission productions Cs/Sr/Ag/I adsorption on chrome–molybdenum steel in Chinese 200 MW HTR-PM

Chrome–molybdenum steel (2·1/4Cr1Mo) is one of the main products of steam generation. The adsorption behaviors of radioactive fission products on 2·1/4Cr1Mo surface are critical in the analysis of HTR-PM. Here, the adsorption behavior of cesium, strontium, silver and iodine on 2·1/4Cr1Mo was investigated with first-principle calculations that the Ag and I atoms prefer to be adsorbed at the square hollow site of the face-centered cubic iron cell with a binding energy of about 1 and 3 eV, respectively. In contrast, Cs and Sr atoms are not adsorbed on the surface of the 2·1/4Cr1Mo. These results are again confirmed via analysis of charge density differences and the densities of state. Furthermore, the adsorption rates of these fission products show that only I and Ag have significant adsorption on the metal substrate. These adsorption results explain the amount of adsorbed radionuclides for an evaluation of nuclear safety in HTR-PM. These micro-pictures of the interaction between fission products and materials are a new and useful way to analyze the source term.

An age-specific biokinetic model for iodine

This paper reviews age-specific biokinetic data for iodine in humans and extends to pre-adult ages the baseline parameter values of the author’s previously published model for systemic iodine in adult humans. Compared with the ICRP’s current age-specific model for iodine introduced in Publication 56 (, pp 45–48), the present model provides a more detailed description of the behaviour of iodine in the human body; predicts moderately higher doses to the thyroid for short-lived isotopes of iodine; predicts similar doses to the thyroid for isotopes with half-time greater than a few hours; and, for most iodine isotopes, predicts substantially higher doses to salivary glands, stomach wall, liver, and kidneys.

Overview of the VERDON-ISTP Program and main insights from the VERDON-2 air ingress test

In order to reduce the uncertainties concerning source term assessment under LWR severe accident conditions, the International Source Term Program has been launched. Four main R&D research axes have been addressed in this program: iodine behaviour in the RCS and containment, study of the boron carbide effect on fuel degradation and FP release, study of the air effect on fuel and FP behaviour, FP release from high burn-up UO2 and MOX fuels.As far as the source term quantification is concerned, four VERDON tests have been defined and were performed in the VERDON laboratory at the CEA Cadarache Centre. We present an overview of these four tests, devoted to the study of FP release from high burn-up UO2 and MOX fuels. We focus on the VERDON-2 air ingress test performed on MOX fuel with a specific loop dedicated to FP release and transport. It addressed two issues: Ru release under mixed steam-air conditions following lower head failure and transport/re-volatilization of Ru and volatile FPs in the primary circuit. The latter was performed thanks to the implementation of thermal gradient tubes exposed at different phases of the sequence. In this configuration, the VERDON facility combines the ability of the analytical approach to identify and understand the physical phenomena involved, with a semi-integral approach, which allows the results to be applied to source term assessments for reactor application. This VERDON-2 test has shown a rather unexpected low release of ruthenium from the MOX sample and no re-volatilization from the thermal gradient tubes. On the contrary, a significant re-volatilization of iodine has been observed when switching to mixed steam-air conditions, as well as a low, but measurable amount of iodine transported under gaseous form downstream of the thermal gradient tubes.

Electrochemical Behavior of Iodine on Nano Gold Doped in H2TiO3

Electrochemical Behavior of Iodine on Nano Gold Doped in H2TiO3

SU-G-IeP2-09: Iodine Imaging at Spectral CT with a Dual-Layer Detector

Purpose: To evaluate the attenuation response of iodine and the accuracy of iodine quantification on a detector-based spectral CT scanner. Methods: A Gammex 461A phantom was scanned using a dual-layer detector (IQon, Philips) at 120 kVp using helical acquisition with a CDTIvol of 15 mGy to approximate the hospital's clinical body protocol. No modifications to the standard protocol were necessary to enable spectral imaging. Iodine inserts at 6 concentrations (2, 5, 7.5, 10, 15, 20 mg/ml) were scanned individually at the center of the phantom and the 20 mg/ml insert was additionally scanned at the 3, 6, and 12 o'clock positions. Scans were repeated 10 times. Conventional, virtual monoenergetic (40–200 keV) and iodine-no-water images (with pixel values equal to iodine concentration of corresponding tissue) were reconstructed from acquired data. A circular ROI (diameter=30 pixels) was used in each conventional and monoenergetic image to measure the mean and standard deviation of the CT number in HU and in each iodine-no-water image to measure iodine concentration in mg/ml. Results: Mean CT number and contrast-to-noise ratio (CNR) measured from monoenergetic images increased with decreasing keV for all iodine concentrations and matched measurements from conventional images at 75 keV. Measurements from the 20 ml insert showed the CT number is independent of location and CNR is a function only of noise, which was higher in the center. Measured concentration from iodine-no-water images matched phantom manufacturer suggested concentration to within 6% on average for inserts at the center of the phantom. Measured concentrations were systematically higher due to optimization of iodine quantification parameters for clinical mixtures of iodine and blood/tissue. Conclusion: Spectral acquisition and reconstruction with a dual-layer detector represents the physical behavior of iodine as expected and accurately quantifies the material concentration. This should permit a variety of clinical applications including lesion characterization, vessel patency, and myocardial perfusion. This study was performed as part of a research agreement among Philips Healthcare, University Hospitals of Cleveland, and Case Western Reserve University.

THAI experimental programme for containment safety assessment under severe accident conditions

Abstract The THAI (THAI = Thermal hydraulics, Hydrogen, Aerosols, Iodine) experimental programme aims to address open questions concerning the behavior of hydrogen, iodine and aerosols in the containment of water cooled reactors. Since its construction in 2000, THAI programme is being performed in the frame of various national projects (sponsored by German Federal Ministry for Economic Affairs and Energy, BMWi) and two international joint projects (under auspices of OECD/NEA). THAI experimental data have been widely used for the validation and further development of Lumped Parameter (LP) and Computational Fluid Dynamics (CFD) codes with 3D capabilities. Selected examples of code benchmark exercises performed based on the THAI data include; hydrogen distribution experiment (ISP-47 and OECD/NEA THAI code benchmark), hydrogen combustion behaviour (ISP-49), hydrogen mitigation by PARs (OECD/NEA THAI-2 code benchmark), iodine/surface interactions, iodine mass transfer, and iodine transport and multi-compartment behaviour (EU-SARNET and EU-SARNET2), thermal-hydraulic tests (German CFD-network). In the present paper, a brief overview on the THAI experiments and their role in the containment safety assessment is discussed.

Iodine Benchmarks in the SARNET Network of Excellence

Accurate calculation of iodine behavior in the containment is very important in determining the potential radioactive release to the environment in light water reactor severe accidents (SAs). Of particular significance is the behavior of gas phase iodine, particularly organic iodine, which is difficult to remove by filtration, e.g., in containment venting systems. Iodine behavior is closely linked with the containment thermal hydraulics, which have a major influence on the distribution of iodine throughout the containment atmosphere and sump. In the European 7th Framework SARNET project, European Commission (EC) cofunded from 2007 to 2013, SA modeling code capability was assessed through two integral benchmarks. In the first, the basis was the German THAI Iod-11/12 tests, where molecular iodine transport with atmospheric flows and iodine interactions with steel surfaces were emphasized. In the second, data from the international Phébus FPT3 test were used, where all aspects of SAs were studied from core degradation, fission product (FP) release, circuit transport/deposition, and containment behavior using realistic FP sources. Thermal hydraulics in the containment were simpler, being well-mixed, and radiolytic interactions of iodine, e.g., with painted surfaces, were studied. These interactions may be an important source of organic iodine in the containment atmosphere. The two benchmarks are thus complementary. In the FPT3 exercise, the calculations could predict the containment thermal hydraulic conditions fairly well. For the more detailed data from THAI, differences were noted for atmospheric flows and relative humidities, outside experimental uncertainties, affecting iodine behavior. The FPT3 iodine results themselves showed a spread in calculated results outside data uncertainties, indicating the need for model improvements in this area, e.g., for radiolytic interaction of iodine with paint. Experimental programs to generate the necessary data needed for code improvement have been recently completed, e.g., in the OECD/THAI, THAI2, BIP, and BIP2 projects, or are in progress, in OECD/STEM and EC/PASSAM. When model improvements have been made, repeat benchmarks are planned to check progress toward code convergence with experimental data, e.g., under the aegis of the new NUGENIA association of which SARNET now forms a part.

SARNET benchmark on Phébus FPT3 integral experiment on core degradation and fission product behaviour

The importance of computer simulations in the assessment of nuclear plant safety systems has increased dramatically during the last three decades. The systems of interest include existing or proposed systems that operate, for example, normal operation, in design basis accident conditions, and in severe accident scenario beyond the design basis. The role of computer simulations is especially critical if one is interested in the reliability, robustness, or safety of high consequence systems that cannot be physically tested in a fully representative environment. In the European 7th Framework SARNET project, European Commission (EC) co-funded from 2008 to 2013, the Phébus FPT3 experiment was chosen as a code benchmark exercise to assess the status of the various codes used for severe accident analyses in light water reactors.The aim of the benchmark was to assess the capability of computer codes to model in an integral way the physical processes taking place during a severe accident in a pressurised water reactor (PWR), starting from the initial stages of core degradation, fission product, actinide and structural material release, their transport through the primary circuit up to the behaviour of the released fission products in the containment.The FPT3 benchmark was well supported, with participation from 16 organisations in 11 countries, using 8 different codes. The temperature history of the fuel bundle and the total hydrogen production were well captured. No code was able to reproduce accurately the final bundle state, using as bulk fuel relocation temperature, the temperature of the first significant material relocation observed during the experiment. The total volatile fission product release was well simulated, but the kinetics were generally overestimated. Concerning the modelling of semi-volatile, low-volatile and structural material release, the models need improvement, notably for Mo and Ru for which a substantial difference between bundle and fuel release was experimentally observed, due to retention in the cooler upper part of the bundle. The retention in the primary circuit was not well predicted, this was due mainly the non-prototypic formation of a boron-rich blockage in the rising line of the FPT3 steam generator, simulated in the circuit as a single external cooled U tube. The deposition mechanism and the volatility of some elements (Te, Cs, I) could be better predicted.Containment vessel thermal hydraulics, designed in the experiment to be well-mixed, were well calculated. Concerning the containment aerosol depletion rate, only stand-alone cases (in which the input data were derived from experimental data) provided acceptable results, whilst the integral cases (in which the input data came from circuit calculations) tended to largely overestimate the total aerosol airborne mass entering the containment.The disagreement of the calculated total aerosol airborne mass in the containment vessel with the measured one is due to the combination of a general underestimation of the overall circuit retention and overestimation of fission product and structural material release.Calculation of iodine chemistry in the containment turned out to be a major challenge. Its quality strongly depends on the correct prediction of chemistry speciation in the integral codes. The major difficulties are related to the presence of high fraction of iodine in gaseous form in the primary circuit during the test, which is not correctly reproduced by the codes. This inability of the codes compromised simulation of the observed iodine behaviour in the containment.In the benchmark a significant user effect was detected (different results being obtained by different users of the same code) which had to be taken into account in analysing the results. This article reports the benchmark results comparing the main parameters calculated and observed, summarising the results achieved, and identifying the areas in which understanding needs to be improved. Relevant experimental and theoretical work is under way to resolve the issues raised.

Electrochemistry of Iodide, Iodine, and Iodine Monochloride in Chloride Containing Nonhaloaluminate Ionic Liquids.

The electrochemical behavior of iodine remains a contemporary research interest due to the integral role of the I(-)/I3(-) couple in dye-sensitized solar cell technology. The neutral (I2) and positive (I(+)) oxidation states of iodine are known to be strongly electrophilic, and thus the I(-)/I2/I(+) redox processes are sensitive to the presence of nucleophilic chloride or bromide, which are both commonly present as impurities in nonhaloaluminate room temperature ionic liquids (ILs). In this study, the electrochemistry of I(-), I2, and ICl has been investigated by cyclic voltammetry at a platinum macrodisk electrode in a binary IL mixture composed of 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C2mim][NTf2]). In the absence of chloride (e.g., in neat [C2mim][NTf2]), I(-) is oxidized in an overall one electron per iodide ion process to I2 via an I3(-) intermediate, giving rise to two resolved I(-)/I3(-) and I3(-)/I2 processes, as per previous reports. In the presence of low concentrations of chloride ([Cl(-)] and [I(-)] are both <30 mM), an additional oxidation process appears at potentials less positive than the I3(-)/I2 process, which corresponds to the oxidation of I3(-) to the interhalide complex anion [ICl2](-), in an overall two electron per iodide ion process. In the presence of a large excess of Cl(-) ([I(-)] ≈ 10 mM and [Cl(-)] ≈ 3.7 M), I(-) is oxidized in an overall two electron per iodide ion process to [ICl2](-) via an [I2Cl](-) intermediate (confirmed by investigating the voltammetric response of ICl and I2 under these conditions). In summary, the I(-)/I2/I(+) processes in nonhaloaluminate ILs involve a complicated interplay between multiple electron transfer pathways and homogeneous chemical reactions which may not be at equilibrium on the voltammetric time scale.

Capture of iodine and organic iodides using silica zeolites and the semiconductor behaviour of iodine in a silica zeolite

During the reprocessing of spent nuclear fuel rods, a highly moist off-gas mixture containing various volatile radioactive species, such as iodine (I2), organic iodides and nitric acid, is produced.