Iodine Retention Research Articles

Separation of iodine produced from fission using silver-coated alumina

A method developed for the preparation of silver-coated alumina, a new material for retention of iodine from alkaline solution is described. Experiments were carried out, oriented to the purification step of 99Mo produced by uranium fission, based on the retention of radioiodine in this material. Iodine retention, as well as molybdenum non-retention, were found, both with excellent results. Further tests showed that the incorporation of this material has no influence on the subsequent 99Mo retention in ion exchange resins. The elution of the radioiodines retained was tested with satisfactory results. This new material can be used not only for improving the 99Mo purification and working conditions, but also as the basis of a method for recovering the fission produced 131I.

Metastatic Thyroid Cancer Unresponsive to Conventional Therapies: Novel Management Approaches Through Translational Clinical Research

In this contribution, we review the limitations of the currently applied "standard" treatments for well-differentiated, non-medullary thyroid cancer (ThyrCa), and describe the molecular and cellular biologic basis of potential novel therapeutic modalities currently under study and/or development. Conventional therapy for ThyrCa consists of total/near-total thyroidectomy, radioiodine (RAI or 131I), and long-term thyroid hormone "suppressive" therapy (THST). RAI therapy remains the cornerstone of the "standard" management strategies for metastatic ThyrCa, and when administered under optimal conditions can achieve either eradication or long-term clinical "control" of the disease. Despite increasing sophistication in the protocols using 131I over the last 30 years, no significant down-trend has been observed in the annual mortality rate for this disease, a fact reflecting the existence of a "core" population of patients with RAI-"resistant" disease. The molecular basis for this phenomenon is believed to be the progressive tumoral de-differentiation over time, with loss of (or marked decrease in) the expression of cellular components responsible for iodine uptake, organification and retention. Adjuvant methods to RAI, such as radiosensitizers and lithium carbonate, provide only marginal additional therapeutic effect. Further, the role of non-RAI-based modalities, such as secondary extensive metastatectomies with curative intent, external beam radiotherapy, and cytotoxic chemotherapy (mainly with doxorubicin-based regimens) has been unfortunately limited to highly selected cases. Palliative methods for acute clinical management of widely metastatic ThyrCa are also presented, along with anecdotal evidence for the potential therapeutic role for octreotide and its radiolabeled therapeutic peptide analogs, selective estrogen receptor modulators (SERM's), as well as bisphosphonates. Translational "bench-to-bedside" research has recently led to the identification of the transcriptional machinery as a valid target for future therapeutic efforts in ThyrCa. Indeed, pre-clinical studies with a variety or agents that affect the rate of thyroid-specific gene transcription, i.e. retinoids, DNA methyltransferase inhibitors, and histone deacetylase inhibitors, have shown their potential for induction of re-differentiation, growth inhibition, promotion of apoptosis and cell cycle regulation. These concerted genomic effects of the above compounds will probably yield novel types of therapies in the clinical arena, especially for RAI-non-avid tumors. Retinoid analogs have already been used in pilot studies in ThyrCa patients with limited success. These re-differentiating agents have raised our expectations for a type of therapy for this malignancy based on a solid molecular rationale, while future progress in the domains of tissue-targeted gene therapy and anti-angiogenesis is eagerly awaited.

Study of a ternary system silica/humic acids/iodine: Capabilities of the nuclear microprobe

Nuclear microprobe by coupling the resonant nuclear reaction 12 C( p, p) 12 C and proton-induced X-ray emission (PIXE) at 1.725 MeV has showed its capabilities to study a ternary system silica slide/humic acids (HA)/iodine. The nuclear reaction on carbon-12 permits the determination of thickness (from 8 nm to 2.5 μm ) of HA films sorbed on mineral surfaces, whereas PIXE simultaneously allows the quantification of trace elements scavenged by HA. The results obtained on the ternary system have evidenced a heterogeneous distribution of HA onto silica slides (presence of organic clusters of variable thickness) and confirmed the trace elements/organic matter association. Moreover, the data suggest a role played by HA in the retention of iodine onto silica slide surfaces.

Absorption of iodine from aqueous solutions on nuclear reactors alloys

Iodide ions I-, molecular iodine I2 and iodate ions IO3 - absorption has been studied on the three alloys which are present, in majority, in french nuclear reactors: Inconel 600, Zircaloy and 304L stainless steel. Iodide and iodate anions are not absorbed on the three considered alloys and contribute only for a negligible quantity to iodine retention on the nuclear reactors materials. Molecular iodine is absorbed according to: 304 stainless steel < Zircaloy < Inconel 600. Influence of pH has been studied: absorption increases in acidic medium and decreases in basic medium. Molecular iodine absorption increases with temperature.Phenomenons which occur with iodine during the cold shutdown of a nuclear reactor and during its restart are discussed from the point of vue of iodine volatilization risk.

Effects of humine compounds on iodine utilisation and retention and on the function of the thyroid gland

Effects of sodium humate (HuNa), containing 61.9% of humic acids in dry matter, on utilisation and retention of dietary iodine were investigated in balance experiments carried out in pigs. A control group was fed a commercial diet containing 0.1 mg of iodine per kg. The daily intake of iodine was 129.2 µg per animal or 4.08 µg per kg live weight. The recommended intake of dietary iodine is 0.25 to 0.30 mg per kg at 88% dry matter. The experimental group (HuNa) was fed the same diet supplemented with 3% of sodium humate which contained 0.5 mg of iodine per kg at 90.04% dry matter. The supplementation increased the daily intake to 141.4 µg per animal, or 4.45 µg per kg live weight. The supplementation of HuNa increased significantly the amount of iodine excreted in faeces (53.2 ± 11.0 vs. 43.0 ± 6.47 µg per animal per day; P < 0.05) and nonsignificantly the urinary iodine excretion (31.8 ± 8.93 vs. 29.0 ± 11.3 µg per animal per day). Differences between the HuNa and the control groups in blood serum iodine concentrations (18.8 vs. 18.1 µg per litre) and urinary iodine concentrations (32.5 vs. 34.4 µg per litre) were nonsignificant. It is evident from the concentrations that the pigs suffered from a serious iodine deficiency. Compared with controls, the HuNa group showed significantly higher triiodothyronine concentration (P < 0.05) and nonsignificantly lower thyroxine and iodine concentrations in blood serum. Dietary iodine utilisation was lower in the HuNa than in the control group (62.3 vs. 66.6%). The results show that utilisation of dietary iodine was limited and that sodium humate (humic acids) reduced iodine utilisation and retention and affected also other parameters indicating their goitrogenic effects.

Probabilistic Accident Consequence Uncertainty Analysis of the Dose Calculations Module in the COSYMA Package

Uncertainty analysis of the dose calculation module of the COSYMA accident consequence assessment code has been undertaken, involving the following steps: (1) Expert judgement techniques were applied to assess uncertainties in measurable parameters determining external and internal doses. (2) The data obtained were used to calculate distributions on the dose quantities required as code input parameters. (3) The effect of uncertainties in dose quantities was analysed for a range of COSYMA end points, including the extent of countermeasures and incidences of early and late health effects, and the most important uncertainties were identified for inclusion in an overall uncertainty analysis of COSYMA. Parameters identified as making the largest contributions to uncertainty included external doses and location factors, residence times of materials on skin, breathing rates, and respiratory tract deposition and retention parameters, for the extent of countermeasures and early health effects, and caesium and iodine retention parameters for late effects.

Retention of iodine in yttria stabilized zirconia

The diffusion behavior of iodine in yttria stabilized zirconia (YSZ) was investigated as a function of the temperature. Iodine implantation was performed in this cubic solid solution by irradiating material samples with 1 MeV iodine ions. The distribution of iodine was evaluated by using TRIM computer calculation and measured by Rutherford backscattering spectrometry (RBS) using 5 MeV 4He particle. The iodine profile was quantified after successive temperature steps. At each step the maximum temperature was held for 2 h. It was found, that the iodine profile remained unchanged up to 1373 K. At 1573 K iodine diffused significantly. The iodine profile was measurable up to 1773 K. Even at this high temperature a significant iodine retention is observed. The diffusion coefficient of iodine (3.5 ± 1.4 × 10 −15 cm 2 s −1) is of the same order as the temperature extrapolated data of iodine in monoclinic/tetragonal zirconia.

Thermal and photon-stimulated reactions of iodobenzene on Ag(111)

The thermal and nonthermal surface reactions of iodobenzene adsorbed on Ag(111) have been studied with temperature programmed desorption (TPD), Auger electron spectroscopy (AES), and time-of-flight (TOF) mass spectrometry. At 105 K iodobenzene adsorbs molecularly. Submonolayer coverages of iodobenzene dissociate to form iodine atoms and phenyl groups on the surface. The I atoms desorb in a broad peak near 800 K, and the phenyl groups recombine to form biphenyl that desorbs in a broad peak near 370 K. Monolayer iodobenzene desorbs at 197 K, and the multilayer desorbs at 175 K. Pulsed-laser excitation of one monolayer (ML) of iodobenzene with 248 and 351 nm light results in CI bond cleavage and retention of iodine and phenyl fragments on the surface. For coverages greater than 2 ML, pulsed excitation with 248 nm light leads to phenyl radical and iodine atom ejection into the gas phase. The TOF spectra for the iodine and phenyl photofragments were fit with two components. The calculated translational temperatures of the two atomic iodine components were 3350 ± 150 K and 1300 ± 130 K. The calculated translational temperature of the two phenyl components was 4050 ± 200 K and 2050 ± 200 K. In multilayers, iodobiphenyl, biphenyl and benzene were produced in photo-induced bimolecular reactions.

Iodine-steel reactions under severe accident conditions in light-water reactors

Owing to large surface areas, the reaction of volatile molecular iodine (I 2) with steel surfaces in the containment may play an important role in predicting the source term to the environment. Both wall retention of iodine and conversion of volatile into non-volatile iodine compounds at steel surfaces have to be considered. Two types of laboratory experiment were carried out at Siemens (KWU) in order to investigate the reaction of I 2 at steel surfaces representative for German power plants. 1. (1) For steel coupons submerged in an I 2 solution at T = 50, 90 or 140 °C the reaction rate of the I 2−I − conversion was determined. No iodine loading was observed on the steel in the aqueous phase tests. I 2 reacts with the steel components (Fe, Cr or Ni) to form metal iodides on the surface which are all immediately dissolved in water under dissociation into the metal and the iodide ions. From these experiments, the I 2−I − conversion rate constants over the temperature range 50–140 °C as well as the activation energy were determined. The measured data are suitable to be included in severe accident iodine codes such as IMPAIR. 2. (2) Steel tubes were exposed to a steam-I 2 flow under dry air at T = 120 °C and steam-condensing conditions at T = 120 and 160 °C. In dry air, I 2, was retained on the steel surface and a deposition rate constant was measured. Under steam-condensing conditions there is an effective conversion of volatile I 2 to non-volatile I − which is subsequently washed off from the steel surface. The I2−T − conversion rate constants suitable for modelling this process were determined. No temperature dependence was found in the range 120–160 °C.

New model for describing urinary iodine excretion: its use for comparing different oral preparations of iodized oil

Iodine excretion in urine after oral dosing with iodized oil is influenced by various factors involved in the retention and elimination of iodine by the body. In a study comparing different treatments of severely iodine-deficient schoolchildren from Malawi, a hyperbolic function was found to describe changes in urinary iodine concentration over time more adequately than a simple exponential function. Compared with oil A, comprising ethyl esters of iodized fatty acids, the retention and elimination of iodine from oil B, comprising triacylglycerol esters of iodized fatty acids, were significantly greater. The mean duration of effectiveness of oral iodized oil, based on urinary iodine concentrations > 0.40 mumol/L, was estimated to be 13.7, 9.9, and 52.5 wk for a single dose of iodized oil A (490 mg I), a split dose of iodized oil A (2 x 245 mg I), and a single dose of iodized oil B (675 mg I), respectively. Dividing the dose of oil A into two equal amounts given on consecutive days did not improve its efficacy.

Renal effects of iodixanol in experimental animals.

The effects of the new nonionic dimeric hexa-iodinated contrast media (CM) iodixanol on renal function and morphology were investigated in 7 independent studies in rats, rabbits and monkeys and compared with other iodinated CM. No significant effect on serum creatinine levels was seen at doses up to and including 5 g I/kg in rats and 10.5 g I/kg in rabbits. An immediate and transient increase in proteinuria was found in rabbits when 10.5 g I/kg was administered as a bolus, and when 12.5 g I/kg was administered as a slow infusion in a comparative study with several CM. Increased serum elimination half-life was shown by measuring serum iodine concentrations after the infusion of 12.5 g I/kg. The effect of a high dose of iodixanol on proteinuria and elimination half-life were in this study in the same range as those of the monomeric nonionic CM, but less pronounced than those of the monomeric ionic CM. Reduced renal capacity was induced in male rats by performing unilateral nephrectomy 4 weeks before i.v. injection of iodixanol or iopamidol (2g I/kg). The administration of CM did not affect renal function monitored as serum concentrations of creatinine and urea. The vacuolation of renal proximal tubular cells and kidney iodine retention were investigated in rats 48 hours after administration of different doses of iodixanol or iotrolan. The no-effect level for vacuolation was 0.5 g I/kg for both CM. Iodine retention was higher in male than females rats, and was higher for iodixanol than iotrolan at the 2 highest dose levels (3 and 5 g I/kg). No difference in iodine retention was found at the other dose levels (0.25-1g I/kg). The reversibility of renal proximal tubular vacuolation after administration of iodixanol was studied in male rats (1.2 g I/kg) and monkeys (1.2 and 3.6 g I/kg). The vacuolation was more pronounced in rats than in monkeys. Vacuolation was completely reversed in all rats 3 weeks after dosing, and 2 of 3 monkeys 3 days after a dose of 1.2 g I/kg. The degree of vacuolation evident in renal percutaneous biopsy specimens from monkeys 14 days after i.v. administration of iodixanol at a dose of 3.5 g I/kg was not significantly different to that in control animals. In conclusion, iodixanol affected renal function to the same degree as did the nonionic monomeric and dimeric comparative media, but to a lesser degree than the ionic monomers. The degree of renal proximal tubular cell vacuolation induced by iodixanol seems to be species-dependent, being less pronounced and more quickly reversed in monkeys than rats.

Iodine and microbial interactions in an organic soil

Iodine-129 in groundwater discharging from a geologic disposal vault could accumulate in wetlands by chemical sorption onto low pH, highly organic solid surfaces or by direct or indirect microbial processes. Previous work indicated that saturation of anion sorption sites, microbial toxicity, or swamping of the I reduction/oxidation reaction decreased the retention of a wetland sphagnum for iodine with increased iodine porewater concentrations. Bog water and peat of an iodine-rich bog were studied to elucidate the role of micro-organisms in the retention and accumulation of iodine in a temperate wetland. Agar plate culture of a wide spectrum of microbes, including yeasts and moulds, with bog groundwater showed anaerobes to be more sensitive to high iodine concentrations than aerobes. Toxicity to anaerobes may occur at 110 mg I litre −1 groundwater. Although iron-related and slime-forming bacteria were not affected at 2000 mg I litre −1, iodine was toxic to sulphate-related bacteria (SRB), as indicated by Biological Activity Reaction Tests. A 50% reduction in the SRB population occurred at groundwater concentrations of 75 mg I litre −1. Microbe enumeration in iodine-rich bog groundwater, using acridine orange staining, showed that the native wetland microbe population was sensitive to concentrations in excess of 200 mg I litre −1 groundwater. Three independent experiments confirm the toxicity threshold concentration for anaerobic and native microbes is ~100mg I litre −1 groundwater. Iodine sorption to fresh peat was slightly slower and more limited under anoxic conditions. Autoclaving the peat, reinoculation following autoclaving and a sucrose addition all inhibited iodine sorption. These results suggest that microbes may only play a minor and indirect role in iodine sorption through the decomposition of organic matter.

Environmental behaviour of radionuclides deposited after the reactor accident of Chernobyl and related exposures.

Several radioecological experiences with isotopes of ruthenium, iodine, caesium and barium, obtained after the reactor accident of Chernobyl, are reported. It was found that for a wet deposition barium was the element with the highest retention on grass. The retention of caesium was lower by a factor of 1.6, retention of iodine by a factor of 2.4 and retention of ruthenium by a factor of 3.5. Former data on the caesium transport in cereals from leaves to grain were confirmed. Depending on the conditions the iodine transfer factor for milk varied between 0.002 and 0.007 d.kg-1. The caesium transfer factor for milk was (0.003 +/- 0.0006) d.kg-1 and was found to be relatively constant in the years 1986-1988. In 1991, the values were higher by a factor of 2-5. Radioecological model results of whole-body burdens in Southern Bavaria showed a reduction of the caesium ingestion doses due to countermeasures and spontaneous changes of consumption habits in the first 2 months by a factor of 5 and till the end of 1987 by a factor of 1.5. The model results agree well with the range of measured whole-body burdens. One month after the deposition, the external exposures in urban environments due to ruthenium, caesium and barium isotopes were found to be reduced by a factor of 2, compared with open lawns, in the case of iodine the reduction was even a factor of 2.5. External exposures of a population group from the Munich area were determined by thermoluminescence dosimetry. The results are in accordance with the spectral measurements of external dose rates in urban environments.

Aryl azides as photolabels. Retention of iodine during photochemical ring expansion of an iodinated tyrosine derivative

In contrast to the photochemical behaviour of iodinated aromatic azides with iodine and azide in the same ring, iodinated N-(4-azidobenzoyl)tyrosine readily undergoes singlet photochemistry with ring expansion and trapping of nucleophiles while retaining iodine substituents in the phenol nucleus.

Consideration of Cesium and Iodine Chemistry and Transport Behavior during the Three Mile Island Unit 2 Accident

Data from the Three Mile Island Unit 2 (TMI-2) accident have shown that only small amounts of iodine and cesium escaped the plant, on the order of tens of curies. To assess the chemical and physical processes responsible for such a limited release, a detailed investigation of iodine and cesium chemical and transport behavior during the core degradation phase of the TMI-2 accident was initiated. Analyses indicate elemental iodine and cesium release from fuel, which subsequently reacts with the high-temperature steam/hydrogen effluent to produce the gaseous species Csl and CsOH. Partial condensation and chemisorption of CsOH in the upper reactor plenum and on hot-leg piping is also predicted, where loss of the CsOH molecule from a mixture of H2O, Csl, CsOH, and HI gases in chemical equilibrium can result in destabilization of the Csl molecule to replace CsOH, forming HI in the process. Likewise, Csl reaction with borated water is predicted to have resulted in partial conversion of Csl to cesium borate and HI. A combination of Csl, HI, and CsOH is therefore assessed to be the principal form of iodine and cesium transport leaving the reactor vessel during core degradation. These species were subsequently dissolved in water, resulting in large-scale retention of fission product iodine and cesium.

Uptake and retention of strontium, iodine and caesium in lowland pasture following continuous or short-term deposition

Data from the extensive routine environmental monitoring programme around the nuclear reprocessing plant at Sellafield, West Cumbria, are analysed for soil to plant uptake of strontium, iodine and caesium. Relative to the top 10 cm of soil, dry weight concentration ratios derived for lowland pastures for strontium, caesium and iodine are 9, 3 and 2 respectively. Long-term trends indicate a ‘spring flush’ of activity in vegetation, although this is not statistically significant. Uptake of caesium and iodine is highest generally for mosses and lichen and lowest for grass. The vegetational field loss of these elements over the first 50 days following deposition, is described by: Sr: R eff (t) = 0.7e −1.15t + 0.25e −0.049t + 0.05e −0.011tI: R eff(t) = 0.7e −1.26t + 0.25e −0.17t + 0.05e −0.092tCs: R eff(t) = 0.6e −0.87t + 0.2e −0.20t + 0.16e −0.065t + 0.04e −0.011t where t is in days. The functions are consistent with the effects of washoff and grazing. Equilibrium plant:soil concentration ratios are established for caesium within about 8 months following short-term deposition. Soil distribution profiles for caesium imply a half-time for transfer through the surface layers of about 6 years.

Low Level Iodine Detection by TXRF Spectrometry

A special measurement technique has been developed to measure very low level iodine concentrations. The gas and water samples to be analysed are taken from the POSEIDON facility at PSI where retention of iodine in water pools in conjunction with light water reactor safety analysis is under investigation. The amount of iodine was measured by means of a Total Reflectance X-Ray Spectrometer (TXRF).

Iodine Retention and Thyroid Dysfunction in Patients on Hemodialysis and Continuous Ambulatory Peritoneal Dialysis

Povidone-iodine is frequently used as an antiseptic in patients on chronic dialysis. In order to determine if the use of povidone-iodine affects thyroid function in these patients, we measured serum iodine and thyroid hormone levels in dialysis patients prior to and following discontinuation of topical povidone-iodine antiseptics. Serum inorganic iodine levels were elevated initially in nearly 90% of the patients (19 on hemodialysis, 12 on continuous ambulatory peritoneal dialysis [CAPD]). Following discontinuation of povidone-iodine, iodine levels over a 3-month period decreased modestly in patients on CAPD (n = 5) and were unchanged in patients on hemodialysis (n = 5). Total and free thyroxine levels were frequently low but did not correlate with protein-bound or inorganic iodine levels and did not change after discontinuation of povidone-iodine. Thyrotropin levels correlated significantly (r = .62, P less than .01) with inorganic iodine levels in patients on hemodialysis, but not for patients on CAPD. We conclude that abnormal thyroid function tests are common in dialysis patients but are not related to iodine retention or to the routine use of topical povidone-iodine-containing antiseptics.

Transfer of Molecular Fission Products Between a Gas and a Surface, with Application to Iodine Retention in a Granular Bed

Included in a project on a filtered and vented system for mitigating reactor meltdown accident consequences, FILTRA, a computational model, was developed for the investigation of iodine adsorption and desorption in a granular bed. The model considers physical adsorption, chemisorption, and desorption of free molecules carried by a gas through the bed. The calculational results show good agreement with experiments. A simplified version of the model has been used for calculating condensation and vaporization of volatile fission products in the primary circuit. The radioactive decay was ignored.

Thiocyanate Feeding with Low Iodine Diet Causes Chronic Iodine Retention in Thyroids of Mice*

Effects of KSCN on thyroidal iodine metabolism were studied in weanling mice fed a low iodide diet (LID) labeled continuously with 125I as iodide. The addition of KSCN (0.3 and 0.6 mg/g diet) resulted in the accumulation of an unusual iodinated protein within the follicles of the mouse thyroids. After 60 days, total thyroidal iodine was 4 times greater than in controls without thiocyanate. The iodinated protein was essentially insoluble at pH 8.0 and was very slowly released from the thyroids; it contained more MIT than DIT and little thyroid hormone. By use of three isotopes (125I, 127I, and 131I) and auto-radiographs, there were shown different iodinated proteins synthesized during high and low iodine intakes and coexistent but segregated in the colloid. Low doses of perchlorate or iodide inhibited or prevented accumulation of the essentially insoluble iodinated protein. It is suggested that when mouse thyroids are iodine depleted, thiocyanate increases the formation of an essentially insoluble iodinated thyroglobulin within the thyroid. Only a small fraction of the iodination may have occurred by this route, but the rate of formation exceeded the rate of release, so the product continuously accumulated.