Jan John

Cesium sorption from concentrated acidic tank wastes using ammonium molybdophosphate-polyacrylonitrile composite sorbents

Ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) composite sorbents have been evaluated for the removal of cesium from Idaho National Engineering and Environmental Laboratory (INEEL) concentrated acidic tank waste. Batch contacts were performed to qualitatively evaluate the effects of increased nitric acid, sodium and potassium. An equilibrium isotherm was generated with simulated concentrated tank waste solutions and fit to the Langmuir equation. Additional batch contact experiments were performed to determine if mercury, plutonium and americium would sorb onto AMP-PAN. Dynamic sorption was evaluated in column tests employing 1.5 cm3 columns operating at 5, 10 and 20 bed volumes of flow per hour. Results indicate, as expected, that dynamic cesium sorption capacity is reduced as the flowrate is increased. Calculated dynamic capacities for cesium were 22.5, 19.8 and 19.6 mg Cs/g sorbent, for 5, 10 and 20 bed volume per hour flows, respectively. The thermal stability of loaded AMP-PAN was evaluated by performing thermogrovimetric analysis (TGA) on samples of AMP, PAN (polymer), and AMP-PAN. Results indicate that AMP-PAN is stable to 400 °C, with less than a 10% loss of weight, which is at least partially due to loss of water of hydration. The evaluation of AMP-PAN indicates that it will effectively remove cesium from concentrated acidic tank waste solutions.

Composite absorbers of inorganic ion-exchangers and polyacrylonitril e binding matrix V. Influence of ionising radiation on the leachability of t37Cs from cemented composite NiFC-PAN absorber

Methods of preparation of granules of inorganic ion exchangers as well as methods for improvement of granular strength of these materials are reviewed. The resulting ion exchangers are classified in three groups—“intrinsic”, supported and composite ion exchangers. Their properties are compared and possibilities of their technological application are evaluated. A new method of preparation of inorganic-organic composite sorbents of inorganic ion-exchangers and polyacrylonitrile binding matrix is described, advantages and disadvantages of such sorbents are discussed. Proposed fields of application include tratment of liquid radioactive and/or hazardous wastes, decontamination of natural water as well as analytical applications.

Composite absorbers consisting of inorganic ion-exchangers and polyacrylonitrile binding matrix

Both cementation and vitrification was shown by preliminary experiments to be applicable for treatment of the spent composite absorbers with polyacrylonitrile binding matrix for final disposal. Loadings of cement mix with composite absorbers up to 5–9% (w/w) were achieved Admixtures of natural clinoptilolite were found to improve compressive strength of the samples. The presence of PAN binding polymer was found not to disqualify the composite absorber tested from final treatment by vitrification.

Radiation formation of colloidal silver particles in aqueous systems.

This paper reports on the formation of silver nanoparticles initiated by gamma and UV radiation in various aqueous solutions. Inorganic precursors were used for radiation and/or photochemical reduction of Ag(+) ions to a metallic form. The influence of various parameters on the nucleation and formation of colloid particles was studied. Attention was also focused on the composition of the irradiated solution. Aliphatic alcohols were used as scavengers of OH radicals and other oxidizing species. The influence of the stabilizers on the formation and stability of the nanoparticles was studied.

Application of New Inorganic-Organic Composite Absorbers with Polyacrylonitrile Binding Matrix for Separation of Radionuclides from Liquid Radioactive Wastes

Inorganic-organic composite absorbers consisting of finely divided inorganic ion-exchangers incorporated into a binding matrix of modified polyacrylonitrile are described. List of the available absorbers is given. Their properties (namely chemical and radiation stability) are specified. Examples of application for the treatment of liquid radioactive waste of various origin are described in detail. Further, possibilities of absorbers regeneration and treatment for final disposal are discussed.

Influence of diluent alkyl substitution on the extraction of Am(III) and Eu(III) by a 6,6´-bis(1,2,4-triazin-3-yl)-2,2´-bipyridine ligand dissolved in alkylated cyclohexanone diluents

Abstract Several alkylated cyclohexanones were investigated as potential diluents for the selective extraction of Am(III) from Eu(III) from nitric acid solutions by the CyMe4-BTBP ligand. No significant extraction of either of the metal ions was observed for these diluents themselves. In the extractions from 1 M HNO3, 3-methylcyclohexanone and 4-methylcyclohexanone gave comparable results to cyclohexanone whereas in the extractions from 4 M HNO3, 2-methylcyclohexanone, 3-methylcyclohexanone and 4-methylcyclohexanone all gave superior results. For the monomethylated diluents, DAm and SFAm/Eu decreased in the order of alkyl substitution 2 > 4 ∼ 3. However, alkyl substitution of cyclohexanone significantly slows down the extraction kinetics compared to cyclohexanone, and the position of alkyl substitution was found to play an important role in the solvents properties. 3-Methylcyclohexanone was identified as the most promising of the diluents.

Separation of radionuclides from chemical and electrochemical decontamination wastes

A multistage process combining photocatalytic degradation of organic complexes and complexants followed by separation of the radionuclides by ion exchange was developed and tested for the treatment of aqueous waste from chemical or electrochemical decontamination of NPP primary circuit internals. In these solutions, both the oxalic and citric acids could be quantitatively degraded within 10-12 hours of irradiation by 254 nm UV radiation in the presence of TiO2 photocatalyst. For the group radionuclides separation, a standard cation exchanger was found to be preferable to any of the set of the tested inorganic-organic composite absorbers.

17th Radiochemical conference: RadChem 2014 Mariánské Lázně, 11–16th May 2014

The 17th Radiochemical Conference—RadChem 2014, was held in the Casino conference centre in Marianske Lazně, Czech Republic, on the 11–16th May 2014. As usual in its more recent history, the conference was coorganized by the Department of Nuclear Chemistry, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague (DNC FNSPE CTU), Czech Chemical Society, and Ioannes Marcus Marci Spectroscopic Society. Together with the ‘‘International Conference on Nuclearand Radiochemistry (NRC)’’ series, the RadChem series form the pillars of the pan-European conference series organised on behalf of the Division of Nuclear and Radiochemistry of the European Association for Chemical and Molecular Sciences (DNRC EuCheMS). Traditionally, RadChem 2014 was organised in cooperation with the International Atomic Energy Agency (IAEA) and was sponsored by the International Union of Pure and Applied Chemistry (IUPAC). Over its 50? years long tradition, the conference has gained a good reputation among the researchers in the field of nuclearand radiochemistry as a platform for the presentations of research results and for the discussions about current issues. It offers a great opportunity to establish new contacts with local and foreign colleagues, especially for young researchers and students.

Joint Bratislava–Prague studies of radiocarbon and uranium in the environment using accelerator mass spectrometry and radiometric methods

A research program has been established between Bratislava and Prague groups to study natural and anthropogenic radionuclides in the environment using both Accelerator Mass Spectrometry (AMS) and radiometric methods. The first studies have focused on 14C activity variations in the atmosphere and biosphere with the aim to evaluate an impact of Czech and Slovak Nuclear Power Plants (NPP) on the environment, and on the development of AMS technique for investigation of actinides (mainly uranium isotopes) in the environment.

Thiacalixarenes: radiation stability and Eu/Am extraction in synergistic systems with COSANs

The radiation stability of thiacalixarenes was not studied systematically, yet. This paper focuses on the stability of two thiacalix[4]arene molecules dissolved in 1,2-dichloroethane or cyclohexanone towards irradiation from 60Co source or linear electron accelerator. The determination of thiacalixarene residual concentration using HPLC method was compared with the assessment of the change in the extraction efficiency, i.e. the change of the distribution ratios of americium and europium in solvent extraction experiments with COSAN molecules. Extraction properties of synergistic mixtures containing irradiated and non-irradiated thiacalixarenes were compared. It was shown that irradiation significantly negatively influences extraction properties of the mixtures.