Adsorption of gaseous iodine-131 at high temperatures by silver impregnated alumina

To prevent radioactive iodides from releasing into the environment in an accident of a nuclear power plant,silver-impregnated alumina(Ag/Al2O3)was fabricated,and its performance of radioactive iodine adsorption from high-temperature gas was tested.The silver loadings on alumina were obtained by ICP-OES and the texture properties of Ag/Al2O3were characterized by N2adsorption-desorption.The Ag/Al2O3was of reduced specific surface(107.2 m2/g at 650?C).Crystalline phases of Ag/Al2O3were confirmed through XRD characterization.After calcination at 650?C for 2 h,the crystalline phase of Ag/Al2O3changed.The131I-removal efficiency of Ag/Al2O3was tested at 100,250,350,450 and 650?C,with good decontamination factor values for the radioactive iodine.Silver-impregnated alumina can be applied as adsorbents to remove radioactive iodine at high temperatures in nuclear accident.     

用放射性甲基碘做示踪剂测量核通风系统除碘效率不同试验方法的比较研究

研究了硫酸二甲酯法、三甲基氯硅烷-磷酰基乙酸三甲酯法和同位素交换法在碘吸附器性能试验及核通风系统除碘效率试验中应用的优缺点。对三种方法的试验产率、试剂及残液毒性、试验可靠性及设备稳定性等方面进行了综合研究。研究结果表明:硫酸二甲酯法由于试剂毒性而在应用上受到一定限制;三甲基氯硅烷-磷酰基乙酸三甲酯法作为低毒性试验方法总体满足现场试验要求,但由于该方法所用试剂对试验设备会造成一定侵蚀,因此需要作一些改进;同位素交换法作为一种新颖的试验方法具有毒性低、产率高、操控简单稳定、风险较低等优点,推荐使用。     

Characterization and storage of radioactive zeolite waste

For the safe storage of zeolite wastes generated by the treatment of radioactive saline water at the Fukushima Daiichi Nuclear Power Station, this study investigated the fundamental properties of herschelite adsorbent and evaluated its adsorption vessel for hydrogen production and corrosion. The hydrogen produced by the herschelite sample is oxidized by radicals as it diffuses to the water surface and thus depends on the sample's water level and dissolved species. The hydrogen production rate of herschelite submerged in seawater or pure water may be evaluated by accounting for the water depth. From the obtained fundamental properties, the hydrogen concentration of a reference vessel (decay heat = 504 W) with or without residual pure water was evaluated by thermal–hydraulic analysis. The maximum hydrogen concentration was below the lower explosive limit (4%). The steady-state corrosion potential of a stainless steel 316L increased with the absorbed dose rate, but the increase was repressed in the presence of herschelite. The temperature and absorbed dose at the bottom of the 504 W vessel were determined as 60 °C and 750 Gy/h, respectively. Under these conditions, localized corrosion of a herschelite-contacted 316L vessel would not immediately occur at Cl^? concentrations of 20,000 ppm.     

Removal of radioactive cesium from solutions by zinc ferrocyanide

Adsorption of 134Cs from aqueous solution by zinc ferrocyanide, and the effect of experimental conditions on the adsorption were investigated. Preliminary results showed that zinc ferrecyanide was very efficient as an absorbent. Over 98% of 134Cs could be removed by zinc ferrocyanide of 0.33 g.L-1 from 134Cs solution (Co) of one hour and the suitable pH ranged 1～10. No significant differences on 134Cs adsorption were observed at 0～50℃, or in solutions containing Ca2 , Fe3 , Mg2 , HCO3-, CO32-, CI- and SO42-, even though they are 1000 times higher than the anions or cations in groundwater. However, the adsorption rates decreased when solutions contained K or Na . The adsorption process could be described by Freundlich and Langmuir adsorption equations.     

Removal of radioactive isotopes from sewage

Data are cited on the purification of sewage from radioactive isotopes by methods of coagulation and ion exchange.It is shown that by the successive use of the indicated rnethods, low-activity sewage may be purified to the maximum perrnissible concentration (MPC) for all radioactive isotopes. The removal of radioactive isotopes from waste solutions by ion exchange resins is directly dependent on the salt composition of the solutions.Translated from Atomnaya Énergiya, Vol. 18, No. 6, pp. 623–626, June, 1965     

Adsorption behaviors of iodide anion on silver loaded macroporous silicas

A macroporous silica-based silver loaded adsorbent was synthesized by grafting the silver complexes of thiourea(Ag(tu)3NO3) into a silica-based copolymer support(Si O2-P). The adsorbent was used to uptake iodide anions(I–) by batch and column techniques. The kinetic and saturated adsorption experiments were carried out by varying the shaking times and initial concentration of I–. Experimental results shown that the kinetic adsorption of I–was controlled by a pseudo second order model and the saturated adsorption of I–was controlled by the chemisorption mechanism, which followed a Langmuir adsorption equation. The breakthrough curve of I–had a S-shaped profile. The column efficiency was estimated to be over 90%.     

Solidification of borate radioactive resins using sulfoaluminate cement blending with zeolite

The solidification of borate radioactive resins using sulfoaluminate cement (SAC) blending with zeolite was investigated, and the performance of SAC–zeolite matrix for immobilizing borate resin was evaluated based on the compressive strength, leachability and mineral phases of solidified waste forms. The experimental results showed that the 28 d compressive strength of resin SAC–zeolite waste forms was 18.8 MPa, the cemented waste forms meet the requirement of water, freezing, irradiation and impact resistance tests. The leaching processes of Cs⁺ and Co²⁺ were diffusion-limit step. The leachability of Cs⁺ was higher than Co²⁺ no matter what the matrix contained zeolite or not, but leachability of both cations was reduced by adding 5% zeolite. For SAC–zeolite matrix, the leaching rates of Cs⁺ and Co²⁺ were 6.40 × 10⁻⁵ cm/d and 1.62 × 10⁻⁷ cm/d, and the cumulative leaching fractions were 2.9 × 10⁻³ cm and 2.3 × 10⁻⁵ cm, respectively. The X-ray diffraction (XRD) analysis suggested that B(OH)₄⁻ was incorporated by substitution of SO₄⁻ in the crystalline structure of ettringite (3CaO·Al₂O₃·3CaSO₄·32H₂O).     

Removal of Co2+ from radioactive wastewater by polyvinyl alcohol (PVA)/chitosan magnetic composite

Cobalt is one of the toxic radioactive elements and the removal of Co²⁺ from radioactive wastewater has received increasing attention in recent years. In this paper, polyvinyl alcohol (PVA)/chitosan magnetic composite was prepared and used for Co²⁺ removal. The effect of initial pH, contact time and initial Co²⁺ concentration on Co²⁺ adsorption was investigated. The kinetics, thermodynamic and isotherms of Co²⁺ sorption onto the composite were determined. The results showed that pseudo second-order equation could be used to describe the Co²⁺ removal process. The maximum sorption capacity was calculated to be 14.39 mg/g at pH 6.0 and 30 °C using the Langmuir model. The analysis of FTIR and SEM-EDAX were performed before and after Co²⁺ sorption onto the PVA/chitosan magnetic beads, revealing that the functional groups –NH₂ and –OH played main role in Co²⁺ sorption process. PVA/chitosan magnetic composite is promising adsorbent for removing Co²⁺ radioactive wastewater.     

Removal of radioactive cobalt ion in high temperature water using titanium oxide

The adsorption of Co²⁺ on titanium oxide (TiO₂) has been experimentally evaluated as a function of temperatures in the range 20–280°C. The selectivity experiments showed that corrosion products such as Co²⁺, Ni²⁺ and Mn²⁺ in reactor water are preferentially adsorbed at high temperatures. The data suggest that there are two reaction mechanisms, i.e. an ion exchange reaction at low temperatures, and chemical adsorption with the formation of insoluble cobalt meta-titanate (CoTiO₃) on the TiO₂ surface at high temperatures.     

Removal of cesium from radioactive wastewater using magnetic chitosan beads cross-linked with glutaraldehyde

A novel magnetic chitosan bead cross-linked with glutaraldehyde was prepared, characterized and applied for Cs(I) removal from aqueous solution. Characteristics and mechanism of Cs(I) removal were investigated. The equilibrium data of Cs(I) adsorption by magnetic chitosan beads were fitted using the Langmuir,Freundlich, Tempkin, Redlich–Peterson(R–P), Slips and Dubini–Radushkevich(D–R) models. The maximum adsorption capacity was estimated at 3.86 mg/g from the Langmuir isotherm. FTIR study revealed that N atom was mainly involved in Cs(I) sorption by magnetic chitosan.The magnetic chitosan is a promising adsorbing material for treating Cs(I)-containing radioactive wastewater.     

Use of poly(methyl methacrylate) in radioactive waste management: I. Radiation stability and degradation

In this study, in order to understand the possible use of PMMA in radioactive waste management as a solidifying agent, radiation stability of the PMMA was studied by gamma irradiations at two different dose rates of 1485 and 82.8 Gy/h. The total dose of irradiation was up to 523 kGy. Degradation nature was tested by studying the changes in mechanical and thermal properties with rate and total dose of irradiation. Ultimate tensile strength and toughness first increased and then decreased with total irradiation dose. Half value dose (HVD) for elongation was 148 kGy and it was 178 kGy for tensile strength at the dose rate of 1485 Gy/h. Half value dose was found from the extrapolation of experimental data as 228 kGy for elongation and 205 kGy for tensile strength at the dose rate of 82.8 Gy/h. The FTIR spectral analysis showed depolymerization degradation of polymer with irradiation. It was concluded from experimental results that PMMA can be used for embedding radioactive wastes.     

Use of poly(methyl methacrylate) in radioactive waste management: II. Monte Carlo simulations

Radioactive waste is generated from the nuclear applications and it should properly be managed in a radioactive waste management system. Different methods are available for treatment and conditioning of radioactive waste. Polymers can be used in the radioactive waste management as an embedding matrix. Poly(methyl methacrylate (PMMA) is a possible candidate material that can be used in the low level radioactive waste management. In this study, based on total resistible dose for PMMA, maximum waste activity that can be embedded into a waste drum was found via Monte Carlo simulations. In addition, Monte Carlo simulations for radioactive waste embedded into above mentioned polymer was performed and the dose rate distribution in the polymer matrix was determined for the initial and different periods of 15.1, 30.2 and 302 years after embedding of waste. Changes of mechanical properties in the polymer embedded waste drum was simulated for PMMA embedded waste matrices based on experimental data.