Behavior Of Iodine Research Articles

Nutrient speciation and hydrography in two anchialine caves in Croatia: tools to understand iodine speciation

Despite iodine being one of the most abundant of the minor elements in oxic seawater, the principal processes controlling its interconversion from iodate to iodide and vice versa, are still either elusive or largely unknown. The two major hypotheses for iodate reduction involve either phytoplankton growth in primary production, or bacteria during regeneration. An earlier study intended to exploit the unusual nature of anchialine environments revealed that iodide is oxidised to iodate in the bottom of such caves, whereas reduction of iodate occurs in the shallower parts of the water column. This investigation was made on the hypothesis that study of the nitrogen and phosphorus nutrient systems within the caves might offer a bridge between the iodine chemistry and the marine bacteria which are assumed to be the agent of change of the iodine in the caves. Accordingly, the hydrography, the nutrient chemistry, and some further iodine studies were made of two anchialine caves on the east coast of the Adriatic Sea in Croatia. Iodate and iodide were determined by differential pulse voltammetry and cathodic stripping square-wave voltammetry, respectively. Total iodine was determined indirectly, as iodate, after oxidation of reduced iodine species with UV irradiation and strong chemical oxidants. Nutrient concentrations were measured by spectrophotometry. Nutrient profiles within the well stratified water columns indicate a relatively short-lived surface source of nitrate and phosphate to the caves, with a more conventional, mid-water, nutrient regeneration system. The latter involves nitrite and ammonium at the bottom of the halocline, suggestive of both autotrophic and heterotrophic microbial activity. High iodate/low iodide deep water, and conservative behaviour of total inorganic iodine were confirmed in both systems. Iodate is reduced to iodide in the hypoxic region where nutrient regeneration occurs. The concentrations of organic iodine were surprisingly high in both systems, generally increasing toward the surface, where it comprised almost 80% of total iodine. As with alkalinity and silica, the results suggest that this refractive iodine component is liberated during dissolution of the surrounding karst rock. A major, natural flushing of one of the caves with fresh water was confirmed, showing that the cave systems offer the opportunity to re-start investigations periodically.

PWR iodine speciation and behaviour under normal primary coolant conditions: An analysis of thermodynamic calculations, sensibility evaluations and NPP feedback

Iodine is one of the most important fission products due to its high fission yield, significant radiobiological hazard and potential volatility. Its environmental and biological risks have been extensively studied in case of a severe reactor accident. Nevertheless, little information is available about iodine behaviour under normal Pressurize Water Reactor (PWR) operating conditions. The work reported explores the behaviour of different iodine species (I −, I 3, I 2, HOI and IO −) during full power periods, transient periods (power reductions and depressurizations) and shutdowns. Thermodynamic calculations were conducted, and their results are compared with previous predictions and with the experimental data provided by nuclear power plants (NPP). Based on thermodynamic calculations and NPP feedback, it was concluded that iodine speciation depends primarily on the redox potential and water radiolysis. • The experimental values confirm that the iodine ionic form I − is the major species during normal operation (I 2 < 2%) and shutdowns (I 2 < 9%). • During shutdowns: - High [I 2] (20–40%) can be observed in the presence of fuel failures following an iodine spike during power or pressure variations. The fuel oxidation by radiolysis products can lead to I 2 formation inside the gap and its subsequent release through cladding defects. - Once in the primary coolant, I 2 is transformed into I − or IO 3 − / IO 4 − , depending on the water oxidation conditions. • The lithium concentration and the primary coolant temperature seem to have a secondary influence on iodine speciation, while the existence of a redox potential threshold appears to be the main factor controlling the formation of volatile and non-volatile iodine forms. This paper summarizes the major results of the iodine thermodynamic studies and PWR feedback, permitting some possible recommendations for inclusion in the NPP guidelines in order to master iodine’s behaviour. Future work is proposed. Redox potential measurements at high temperatures, coupled with thermodynamic estimations and radiolysis analysis, should be considered as useful tools to specify the optimal conditions for limiting iodine volatisation and I 2 absorption.

ICONE19-43331 Multi-Compartment COCOSYS-AIM Analysis of the Iodine Behavior in a Reactor Containment during a Severe Accident

ICONE19-43331 Multi-Compartment COCOSYS-AIM Analysis of the Iodine Behavior in a Reactor Containment during a Severe Accident

REVIEW: Iodine Determination by Inductively Coupled Plasma Spectrometry

Iodine is a chemical element with critical physiological roles and its determination using instrumental analysis is not trivial. Inductively coupled plasma spectrometry associated with either optical emission (ICP-OES) or mass spectrometry (ICP-MS) may be employed, but each alternative presents limitations considering iodine behavior in argon plasma and the occurrence of interferences. Sample preparation is also a critical issue when using sample introduction by pneumatic nebulization due to memory effects. This critical review discusses the literature dealing with sample preparation followed by ICP-OES or ICP-MS for iodine determination in a plethora of samples. It is shown that the best figures of merit may be reached using sample preparation in alkaline medium followed by ICP-MS measurements.

Application and Validation of ASTEC Code in the Analysis of Fission Product Release and Transport Processes Taking Place in the Phébus and the STORM Facilities

This paper presents an overview of the activities carried out in the framework of the SARNET project by the CIEMAT, INR, JRC/IE, GRS, UJV, and VUJE partners involved in the validation of ASTEC on fission product (FP) release and transport experiments simulating severe accident conditions in the reactor circuit and containment.These activities were mainly devoted to the analysis of the Phébus experiments, FPT0, FPT1, and FPT2, which provided fundamental reference data for the severe accident research. The ELSA, SOPHAEROS, CPA, and IODE modules were used for FP release from the bundle, transport in the circuit, containment thermal hydraulics and aerosol behavior, and iodine behavior in containment, respectively. Studies on aerosol behavior in the STORM experiments and iodine behavior in the ThAI experiments are also summarized.The paper describes not only the results of validation of some stand-alone or several coupled code modules but also the results of first integral calculations, when all the relevant modules of the ASTEC code were used to model the FP release and transport. In the integral calculations, no boundary conditions are to be defined by the code users for most of the code modules, but only at such interfaces were the boundary conditions applied in the experiment. The integral calculation allows more objective judgment about the combined uncertainties of the calculated results.Together with overview of the progress in the validation of the main ASTEC modules, this paper also points out what needs to be improved in the modeling of future ASTEC V2 code versions.

Modeling the dynamics of iodine in the protective shell during accidents in nuclear power plants with VVER

During a loss-of-coolant and core meltdown accident at a nuclear power plant fission products enter the atmosphere inside the protective shell. One of the main factors determining the effect on the environment, the dose loads in personnel and the general public in the first days after the accident is radioactive iodine. To evaluate the mass of the radioactive iodine entering the environment, it is necessary to calculate its concentration in the protective shell. The model developed to describe the dynamics of iodine and the computational module in the integrated code make it possible to perform numerical modeling of the behavior of iodine in the protective shell in the case of accidents at nuclear power plants with VVER reactors. The model makes it possible to take account of the effect of physicochemical processes on the formation of volatile forms of iodine as well as the dynamics of thermohydraulic parameters on the iodine distribution. Verification showed an adequate description of the dynamics of the volatile forms of iodine in the protective shell.

Iodine-Mediated Solvent-Controlled Selective Electrophilic Cyclization and Oxidative Esterification of o-Alkynyl Aldehydes: An Easy Access to Pyranoquinolines, Pyranoquinolinones, and Isocumarins

Chemoselective behavior of iodine in different solvents in the electrophilic iodocyclization of o-alkynyl aldehydes is described. o-Alkynyl aldehydes 3a-t on reaction with I2 in CH2Cl2 with appropriate nucleophiles provides pyrano[4,3-b]quinolines 4a-f, via formation of cyclic iodonium intermediate Q; however, using alcohols as a solvent as well as nucleophile, o-alkynyl esters 5a-y were obtained selectively in good to excellent yields via formation of hypoiodide intermediate R. Subsequently, o-alkynyl esters were converted in to pyranoquinolinones 6a-i and isocoumarin 6j by electrophilic iodocyclization. This developed oxidative esterification provides a novel access for the chemoselective synthesis of esters 5q-u from aldehydes 3n-p without oxidizing primary alcohol present in the substrate.

ChemInform Abstract: Interaction of Fluoroxenonium Triflate, Fluorosulfate, and Nitrate with Alkenes. Stereochemical Evidence for the Electrophilic Noble Gas Cation Addition to the Carbon-Carbon Double Bond.

Reactions of fluoroxenonium triflate (1), fluorosulfate (2), and nitrate (3), prepared from XeF 2 and the corresponding acids in CH 2 Cl 2 at −50°C, with cyclohexene and 1-hexene result in β-fluoroalkyl triflates, fluorosulfates, and nitrates. Triflate 1 reacts with cyclohexene with exclusive formation of the cis isomer 5, the analogous reactions of fluorosulfate 2 and nitrate 3 give mixtures of the corresponding cis and trans isomers. Reactions of 1-hexene with reagents 1−3 lead to mixtures of two regioisomers with domination of the Markovnikow type of addition. The stereochemical result of these reactions is rationalized in terms of an electrophilic attack by the positive xenonium ion on the π-electrons of the double bond with intermediate formation of organoxenonium species in analogy with the behavior of the isoelectronic iodine(III) species

ChemInform Abstract: Synthesis and Mass Spectrometric Behaviour of Iodine Allogibberic Acid Compounds.

ChemInform Abstract: Synthesis and Mass Spectrometric Behaviour of Iodine Allogibberic Acid Compounds.

ASTEC, COCOSYS, and LIRIC Interpretation of the Iodine Behavior in the Large-Scale THAI Test Iod-9

The large-scale iodine test Iod-9 of the German Thermal hydraulics, Hydrogen, Aerosols, Iodine (THAI) program was jointly interpreted by means of post-test analyses within the THAI Circle of the Severe Accident Research NETwork (SARNET)/Work Package 16. In this test, molecular iodine (I2) was injected into the vessel dome of the 60 m3 THAI vessel to observe the evolution of its distribution between water, gas, and surfaces. The main processes addressed in Iod-9 are (a) the mass transfer of I2 between the gas and the two sumps, (b) the iodine transport in the main sump when it is stratified and then mixed, and (c) the I2 adsorption onto, and desorption from, the vessel walls in the presence and absence of wall condensation. The codes applied by the THAI Circle partners were the Accident Source Term Evaluation Code (ASTEC)-IODE (IRSN, Saint Paul Lez Durance, France), Containment Code System (COCOSYS)-Advanced Iodine Model (AIM) (GRS, Garching, Germany), and Library of Iodine Reactions in Containment (LIRIC; AECL, Chalk River, ON, Canada). ASTEC-IODE and the Advanced Iodine Model (AIM) are semi-empirical iodine models integrated in the lumped-parameter codes ASTEC and COCOSYS, respectively. With both codes multicompartment iodine calculations can be performed. LIRIC is a mechanistic iodine model for single stand-alone calculations. The simulation results are compared with each other and with the experimental measurements. Special issues that were encountered during this work were studied in more details: I2 diffusion in the sump water, I2 reaction with the steel of the vessel wall in gaseous and aqueous phases, and I2 mass transfer from the gas to the sump. Iodine transport and behavior in THAI test Iod-9 are fairly well simulated by ASTEC-IODE, COCOSYS-AIM, and LIRIC in post-test calculations. The measured iodine behavior is well understood and all measured data are found to be consistent. The very slow iodine transport within the stratified main sump was simulated with COCOSYS only, in a qualitative way. Consequently, this work highlighted the need to improve modeling of (a) the wet iodine adsorption and the washdown from the walls, (b) the I2 mass transfer between gas and sump, and (c) the I2/steel reaction in the gaseous and aqueous phases. In any case, the analysis of the large-scale iodine test Iod-9 has been an important validation step for the codes applied.

Modeling of Iodine Radiochemistry in the ASTEC Severe Accident Code: Description and Application to FPT-2 PHEBUS Test

In the case of a hypothetical severe accident in a nuclear power plant, iodine is one of the fission products of major importance. It may be present in various gaseous forms that could be released to the environment, impacting population health. In such a case, the amount released (the so-called “source term”) has to be estimated in order to help the safety authorities protect the population from radiological consequences. This estimation is one of the main objectives of the Accident Source Term Evaluation Code (ASTEC) that is developed jointly by the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and the German institute Gesellschaft für Anlagen- und Reaktorsicherheit. ASTEC is composed of various modules able to model the nuclear reactor behavior during an accident. One of these modules, named IODE, predicts iodine behavior in the reactor containment. It is able to model the kinetics of about 35 chemical reactions and mass transfer processes. IODE is validated against separate effect tests, semi-integral experiments, and integral experiments. This paper presents the experimental phenomena that would take place in reactor containment in the case of a severe accident. Then, IODE is used to model the experimental gaseous concentration of organic and inorganic iodine in the PHEBUS FPT-2 test carried out by IRSN. The comparison of experimental data and the modeling show a general good agreement for inorganic iodine even if some differences are evidenced. For organic iodides the modeling is not satisfying. These differences might be explained by the deficiencies of some models and by some assumptions that still have to be validated by dedicated experiments.

Reassessment of Reactor Coolant and Iodine Chemistry under Accident Conditions

Under severe accident conditions, the chemistry of reactor coolant could be significantly different from that under normal operating conditions. Injection of standby liquid control (SBLC) solution, release of fission product cesium (Cs) from damaged fuel rods, and addition of NaOH and Na2S2O3 in spray water will certainly enhance the alkalinity of water. In addition, oxidation of fuel cladding (zircaloy) by hightemperature water and steam would produce a significant amount of hydrogen, and hydrogen in water could effectively suppress water radiolysis and make the water more reducing. It is believed that the chemistry and transport behavior of iodine released from damaged fuel rods are strongly dependent on the chemistry of reactor water under accident conditions, and it is expected that the released iodine will most likely remain in nonvolatile forms in water. The chemistry of reactor coolant and the activities of iodine released from a damaged core are reviewed in detail in this paper.

Recent advances on containment iodine chemistry

The 5th FWP EURSAFE Project highlighted iodine chemistry in the containment as one of the issues requiring further research in order to reduce source term uncertainties. Consequently, a series of studies was launched in the 6th FWP SARNET Project aimed at improving the predictability of iodine behaviour during severe accidents via a better understanding of the complex chemical phenomena in the containment. In particular, SARNET has striven to foster common interpretation of integral and separate effect test data, production of new or improved models where necessary, and compilation of the existing knowledge of the subject. The work has been based on a substantial amount of experimental information made available from bench-scale projects (PARIS and EPICUR), via intermediate-scale tests (CAIMAN) to large-scale facilities (SISYPHE, THAI and PHEBUS-FP). In the experimental field, particular attention has been paid to two specific issues: the effects of radiation on both aqueous and gaseous iodine chemistry, and the mass transfer of iodine between aqueous and gaseous phases. Comparisons between calculations and results of the EPICUR and CAIMAN experiments suggest that the aqueous phase chemistry is reasonably well understood, although there are still some areas of uncertainty. Interpretation of integral experiments, like PHEBUS-FPT2, indicated that radiation-induced conversion of molecular iodine into particulate species (I x O y ) could be responsible for the gaseous iodine depletion observed in the long-term. However, the results of much simpler, small-scale experiments have shown that further improvements in understanding and modelling are still needed. Mass transfer modelling has been extended to cover evaporating sump conditions based on SISYPHE data; however, application of this model to the larger scale THAI experiments seems not to be straightforward. In addition to these two major issues, some specific studies have been carried out concerning the potential effect of passive autocatalytic hydrogen recombiners on iodine volatility. The RECI analytical experiments have shown that metal iodides (namely CsI and CdI 2) are not stable and yield gaseous iodine when heated, in a humid atmosphere, at temperatures representative of recombiner operation. Another important undertaking successfully carried out has been the compilation of an Iodine Data Book, which provides a critical review of the experimental data and modelling approaches that have been used in the development of iodine source term methodologies. This should assist in a proper use of such models, and inform their future development.

Behaviour of radioactive iodine and bromine from aqueous solutions on the ion-exchange resin Duolite A-113

The iodide and bromide forms of the ion exchange resin Duolite A-113 were equilibrated separately with respectively labelled iodide and bromide ion solutions of different concentrations, varying from 0.005 M to 0.100 M in the temperature range of 26.0°C to 43.0°C. The distribution coefficient Kd values calculated for iodide and bromide ion exchanges increase with the ionic concentration of the external solution; however, with a rise in temperature, the Kd values calculated were found to decrease. Also, the Kd values were higher for iodide exchanges than for bromide exchanges.

オホーツク海および日本海に胚胎する表層型ガスハイドレート鉱床における間隙水のハロゲンと放射性ヨウ素同位体（&lt;sup&gt;129&lt;/sup&gt;I）の地球化学

Sulfate, halogen, and radioactive 129I concentrations were determined in pore waters associated with massive gas hydrate deposits in shallow sediments along the boundary between the Amurian and Okhotsk plates in the Okhotsk Sea and Japan Sea. Because of the strong biophilic behavior of iodine and weaker behavior of bromine, in contrast to conservative chlorine, in the marine system and the presence of a long-lived radioisotope of iodine (129I), these analyses are useful for determining the age and nature of source organic materials responsible for hydrocarbons, mostly methane, in gas hydrates. Rapid sulfate decreases with depth reflect active methane migration toward the seafloor, particularly around gas hydrate-bearing sites at both locations. While salt exclusion from gas hydrates during crystallization is likely to have resulted in the downward increase of Cl, and potentially Br and I concentrations, gas hydrate dissociation at depth caused a gentle dilution of pore waters. Biophilic Br and I concentrations rapidly increase with depth, reaching 1500 and 400 μM at the core bottom, respectively, indicating that upwelling fluids are enriched in Br and I derived from marine organic materials degraded in deep sediments. The 129I/I ratios thus reflect the potential ages of source formations of iodine and associated methane, providing ∼35 Ma northeast off Sakhalin Island in the Okhotsk Sea and ∼30 Ma in the Umitaka Spur-Joetsu Knoll region in the eastern margin of the Japan Sea. These ages correspond well with the initial activities of the Amurian and Okhotsk plates and the subsequent opening of the Japan Sea, which formed the present geological setting of the northeastern margin of the Eurasian continent. Active plate motions led to the rapid accumulation of organic-rich sediments that are responsible for iodine and methane in gas hydrate occurring along the plate boundary.

Perchlorate and iodine: a novel focus on newborns

ADVERTISEMENT RETURN TO ISSUEPREVEnvironmental NewsNEXTPerchlorate and iodine: a novel focus on newbornsThe behavior of perchlorate and iodine in women differs from in vitro data.Rebecca RennerCite this: Environ. Sci. Technol. 2008, 42, 21, 7731Publication Date (Web):September 17, 2008Publication History Published online17 September 2008Published inissue 1 November 2008https://doi.org/10.1021/es8024758Copyright © 2008 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views827Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSUBJECTS:Beverages,Dairy products,Impurities,Iodine,Perchlorates Get e-Alerts

A simple probabilistic approach to evaluate radioiodine behavior at severe accidents: Application to PHEBUS test FPT1

A simple probabilistic approach is proposed to quantify the relative importance of selected processes and mechanisms which govern the behavior of radioiodine under conditions pertaining to a postulated severe accident. In principle, these are sensitivity studies of a dedicated, small event tree which describes the iodine behavior at an accident. The emphasis is put on the processes taking place in containment at a late phase of the accident. Here, volatile species of iodine (volatile iodine: I 2 and various organic iodides) could form from the species which were transported from RCS to containment originally as non-volatile. The relative importance of the processes leading to volatile iodine formation in containment is, for a long time, a subject of some dispute among the international research communities. The proposed probabilistic insight could be one of the many ways to address these complicated questions. In this work, the probabilistic approach was tested against the results of the well-documented PHEBUS FPT1 experiment. The small containment iodine event tree was processed by the EVNTRE code with a direct call from within the tree to the detailed iodine chemistry program calculating the speciation of iodine in containment. The French program IODE, as a part of the ASTEC suite of codes, has been used for this purpose. The results of this sensitivity study of PHEBUS FPT1 are promising as for the possibility to use such (or similar) probabilistic method for thorough analyses of uncertainties linked with the iodine behavior in containment at an accident. Similar approach could be used even for the iodine behavior modeling in whole-plant PRA analyses.

Superiority of K-edge XANES over LIII-edge XANES in the Speciation of Iodine in Natural Soils

Environmental behavior of iodine is of great importance especially related to the release of radioiodine from the processing of nuclear fuel, nuclear accidents, etc. To understand the fate of radioactive iodine in soil-water systems, it is necessary to establish a speciation method of iodine in soil. XANES is one of the most important candidates and we compared the performance of L(III)-edge and K-edge XANES for this purpose. In particular, fluorescence XANES with a multi-element semiconductor detector is essential for the measurement of XANES spectra for trace amounts of iodine in natural soil samples. When comparing L(III)- and K-edges, L(III)-edge XANES can be useful for the speciation due to its ability to distinguish various iodine species in their XANES spectra. However, at L(III)-edge measuring iodine L(alpha) emission, the proximity of its energy to those of Ca K(alpha) and K(beta1) causes a large contribution of background X-rays in the XANES spectra, since Ca is a major element in soil. Thus, it was concluded that K-edge XANES is more useful than L(III)-edge for the speciation of iodine in natural soils owing to its lower detection limit. The K-edge XANES was successfully applied to the speciation of natural iodine in a soil sample (iodine concentration: 55.8 mg/kg), showing that iodine is present in the sample as organo-iodine species incorporated in humic substances.

Microbial Contribution to Global Iodine Cycling: Volatilization, Accumulation, Reduction, Oxidation, and Sorption of Iodine

Iodine is an essential trace element for humans and animals because of its important role as a constituent of thyroid hormones. If the anthropogenic iodine-129 ((129)I, half-life: 1.6×10(7) years), which is released from nuclear facilities into the environment and has a long half-life, participates in the biogeochemical cycling of iodine, it potentially accumulates in the human thyroid gland and might cause thyroid cancer. Therefore, it is necessary to obtain better information on the behavior of iodine in the environment for accurate safety assessments of (129)I. Major pathways of iodine cycling are the volatilization of organic iodine compounds into the atmosphere, accumulation of iodine in living organisms, oxidation and reduction of inorganic iodine species, and sorption of iodine by soils and sediments. Considerable geochemical evidence has indicated that these processes are influenced or controlled by microbial activities, although the precise mechanisms involved are still unclear. This review summarizes current knowledge on interactions between microorganisms and iodine, with special emphasis on newly isolated bacteria possibly contributing to the cycling of iodine on a global scale.

Diffusion Behavior of Organic Carbon and Iodine in Low-heat Portland Cement Containing Fly Ash

AbstractThe diffusion of radionuclides in cementitious materials used as an engineered barrier is an important parameter in the performance assessment of the sub-surface repository system used for low-level radioactive waste disposal in Japan. In particular, organic carbon-14 and iodine-129 would provide large contributions to the dose evaluation, because of their low ability to be adsorbed on cementitious materials. In this study, the diffusion of acetate and iodide in hardened cement pastes was examined by through-diffusion experiments. Low-heat Portland cement containing 30 wt% fly ash (FAC), which is a candidate cement material for the construction of the sub-surface repository, was prepared for the diffusion experiments. The effective diffusion coefficients, De, of the trace ions for hardened FAC cement pastes were estimated to be on the order of 10-13 m2 s-1 at the beginning of the diffusion experiments. Then, the rate of diffusion of the trace ions decreased over the experimental period of 1-15 months. This is probably due to the change in the microstructure of the FAC as the result of a pozzolanic reaction. After a few months, the values of De were estimated to be on the order of 10-14 m2 s-1. These results suggest that an engineered barrier made of FAC can act as an effective barrier inhibiting the diffusion of trace ions such as organic carbon and iodine.