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Method for iodine radionuclides separation from primary coolant samples
Abstract
A method is presented for isolating iodine isotopes from aqueous coolant of the nuclear power plants’ first circuit. At first, all forms of iodine radionuclides are converted into molecular form by the sequential addition of a carrier–potassium iodide, as well as hydroxylamine chloride, nitric acid and potassium nitrite. Then molecular iodine is transferred into the gas phase and volatile iodine radionuclides are immobilized on a membrane impregnated with metallic silver. The main advantage of the method is high selectivity of iodine release in relation to radionuclides interfering with the measurement of its activity.
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In order to improve the adsorption speed of iodine from water, MIL-101 with extra-large specific surface area (3054 m2/g) was chosen as a base material, and then, Ag was doped into MIL-101 to enhance its adsorption capacity through an incipient-wetness impregnation method. With the characterization of SEM-EDS, TEM, XRD, XPS, TGA, IR, and BET techniques, the resulting Ag was identified to be stay in the framework of MIL-101 stably in the form of AgII (generally, AgII cation isn’t stable). However, after the adsorption of I- anions, AgII stay in the cages of MIL-101 in the form of AgI. It is important to note that, all adsorbents show high adsorption speed of iodine in solution. The equilibrium adsorption time of the adsorbents were acquired by only a few minutes, which can be attributed to its large BET surface area. An interesting note is that, when the doping amount of Ag is less than 9%, the iodine anions adsorption capacity of Ag@MIL-101 is greater than its theoretical adsorption capacity. It shows that both physical adsorption and chemical adsorption are existed in the adsorption process. This study hopefully leads to a new and highly efficient Ag-based adsorbent for iodide adsorb from solutions.
This work, by one of the most prominent investigators in the field, is a comprehensive and much-needed tool for the teaching and practice of radioanalytical chemistry. It encompasses a concise theoretical background, laboratory work, and data interpretation. It also contains chapters on the most current and visible applications of radioanalytical techniques. Its emphasis on the practical aspects on laboratory setup and operation make it a valuable tool for training professionals and students alike. © 2007 Springer Science+Business Media, LLC. All rights reserved.
Radioactive iodine isotopes which are produced in nuclear power plants and used in medical research institutes could be a serious threat to the health of many people if accidentally released to the environment since the thyroid gland can absorb and concentrate them from a liquid. For this reason, uptake of iodide anions was investigated on microrosette-like δ-Bi2O3 (MR-δ-Bi2O3). The MR-δ-Bi2O3 adsorbent showed a very high uptake capacity of 1.44 mmol g-1 by forming insoluble Bi4I2O5 phase. The MR-δ-Bi2O3 also displayed fast uptake kinetics and could be easily separated from a liquid after use due to its novel morphology. In addition, the adsorbent showed excellent selectivity for I- anions in the presence of large concentrations of competitive anions such as Cl-, NO3-, SO42- and CO32-, and could work in a wide pH range of 4-11. This study led to a new and highly efficient Bi-based adsorbent for iodide capture from solutions.
The results of investigations carried out in the past 15–20 years in the chemistry of radioactive iodine in the gas phase and in aqueous media of various compositions are described systematically and analyzed. The prospects for practical application of the obtained data in various fields of nuclear power industry including accidents at nuclear power plants and enterprises engaged in spent nuclear fuel reprocessing are estimated. The bibliography includes 206 references.
Ion exchange between aqueous protons and surface Hg and Cu sites on cinnabar (HgS) and chalcocite (Cu{sub 2}S) are examined by potentiometric titrations at 25 {degree}C in 1, 0.1, 0.01, and 0.001 M NaCl solutions. Cinnabar and chalcocite surfaces are negatively charged at pH > 3, presumably due to deprotonation of exposed thiol groups. Despite the anionic nature of the two metal sulfide surfaces, iodide sorbs strongly to both. Measured distribution ratios ({Kappa}{sub d}) far exceed those reported for all other minerals; maximal {Kappa}{sub d}`s of 1375 mL/g (Cu{sub 2}S) and 3080 mL/g (HgS) were observed between pH 4 and pH 5 and were substantial at all pH`s measured (4 < pH < 10). Iodide sorption apparently occurs by exchange of hydroxyls attached to Hg and Cu sites. 18 refs., 3 figs.
Problems of fuel failure monitoring in life tests of new cores for nuclear power installations are formulated. General mechanisms
of reference radionuclide release into in the water coolant of a nuclear reactor for various fuel conditions are considered.
A scheme of radiochemical monitoring is suggested, and problem-specific methods are developed for fuel failure monitoring.
Examples of resolving monitoring problems at multiple and single failures are given.
Samples of primary coolant at two pressurized water reactors in the United States have been collected and analyzed to determine the fraction of the radioiodine present in volatile forms. The volatile species, I² and organic iodides, would be available for prompt release following a steam generator tube rupture (SGTR) accident, which overpressurizes the secondary coolant system and causes venting to the atmosphere. Coolant samples were collected at full power, during power reduction at the start of an outage, and up to 48 h after shutdown. Radioiodine concentrations spiked as power was decreased, and an increase in the volatile species fraction to â¼20% was seen with 2 h of shutdown. A second peak of 30 to 40% volatile species occurred at â¼ 1.5 days after shutdown, but is not significant for SGTR accidents.
The previous study reported that BiPbO2(NO3) is one of the most promising candidate materials for removing and immobilizing radioactive iodide. In that case, the solution
contained only dissolved NaI and did not contain competing anions. This paper reports the reactivity of BiPbO2(NO3) with iodide ions in simulated radioactive liquid waste. This liquid contains many components, especially highly concentrated
NaNO2, Na2CO3 and NaNO3. The obtained results show that BiPbO2(NO3) is useful for removing iodide ion from the simulated radioactive liquid waste but that there is a problem which should be
resolved in the future. The problem is that a competing anion, HCO3
−, interferes with the exchange reaction, and only the surfaces of the BiPbO2(NO3) crystals are used for the reaction.
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−, I3, I2, 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 (I2 < 2%) and shutdowns (I2 < 9%).•During shutdowns:-High [I2] (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 I2 formation inside the gap and its subsequent release through cladding defects.-Once in the primary coolant, I2 is transformed into I− or , 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 I2 absorption.Highlights► Few data is available about iodine behaviour under normal PWR operating conditions. ► This study provides the characteristic iodine speciation in PWR primary coolant. ► The conclusions are based on thermodynamic calculations and experimental analysis. ► Iodine ionic form is the major specie during full power and shutdown. ► Iodine speciation mainly influenced by redox potential: secondary effect of [Li] and T.
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