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Abstract  

In our present study, the reprocessability of a self-reinforced PP composites (SRPPC) prepared by compression molding was studied. The composite materials (handled separately, based on the related matrix material) were ground, then extruded five times and injection molded after the first and fifth cycle in order to investigate the behaviour of the material during reprocessing. As a reference, the matrices of the composites were also reprocessed and injection molded similarly to the composites. On the manufactured specimens, static (tensile and flexural) and dynamic mechanical tests (Charpy) were performed. The melting and crystalline characteristics were studied by Differential Scanning Calorimetry (DSC). The probable decomposition caused by multiple extrusions was followed by the Melt Volume Rate (MVR). The results indicated that in case of commercial materials there is no significant degradation even after multiple reprocessing cycles; therefore, the reprocessability of SRPPC products has no hindrance. The presence of α-iPP reinforcement in the rPP-based composites after reprocessing results in increased inclination for crystallization and consequently leads to improved mechanical stiffness compared to rPP neat matrices.

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Abstract  

Current status on the chemical aspects of nuclear fuel reprocessing is presented with special emphasis on the Purex process which continues to be the process of choice for the last four decades. Better decontamination from fission products, new methods for uraniumplutonium partitioning and removal of actinides from high active waste are challenging areas in process chemistry. The development work on TRUEX and DIAMEX process for treating high active waste is briefly described. An overview of pyrochemical processes, which are important for Integral Fast Reactor Concept, is presented.

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Abstract  

By simulation experiments with a 10–5 mol/l solution of iodododecane labeled with131I in n-dodecane the influence of various materials and conditions, which are possible in nuclear fuel reprocessing, has been investigated. The formation of decomposition products was detected via HPLC with a radioactivity monitor. By means of252Cf plasma-desorption mass spectrometry (PDMS) the decomposition products were identified. It was found that a temperature of 100°C favored the formation of iodoalkanes with chain lengths of C1 to C11. The presence of TBP(tri-n-butyl-phosphate) accelerated the decomposition of iodododecane. In pure TBP only iodobutane was formed as a decomposition product.

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Abstract  

N,N-dimethylhydroxylamine (DMHA) is a novel salt-free reducing reagent used in the separation U from Pu and Np in the reprocessing of power spent fuel. This paper reports on the radiolysis of aqueous DMHA solution and its radiolytic liquid organics. Results show that the main organics in irradiated DMHA solution are N-methyl hydroxylamine, formaldehyde and formic acid. The analysis of DMHA and N-methyl hydroxylamine were performed by gas chromatography, and that of formaldehyde was performed by ultraviolet–visible spectrophotometry. The analysis of formic acid was performed by ion chromatography. For 0.1–0.5 mol L−1 DMHA irradiated to 5–25 kGy, the residual DMHA concentration is (0.07–0.47) mol L−1, the degradation rate of DMHA at 25 kGy is 10.1–30.1%. The concentrations of N-methylhydroxylamine, formaldehyde and formic acid are (8.25–19.36) × 10−3, (4.20–36.36) × 10−3 and (1.35–10.9) × 10−4 mol L−1, respectively. The residual DMHA concentration decreases with the increasing dose. The concentrations of N-methylhydroxylamine and formaldehyde increase with the dose and initial DMHA concentration, and that of formic acid increases with the dose, but the relationship between the concentration of formic acid and initial DMHA concentration is not obvious.

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Abstract  

The chemistry of reprocessing, the recovery and purification of plutonium from uranium and fission products produced in the fuel of a nuclear reactor, was surveyed and is described. Reprocessing presented unique chemical problems because of the intense radioactivity, the extreme degree of separation required, and the diversity of elements present. These challenges were met, and improved processes have evolved with time. After 50 years, improvements are still being introduced into the classical solvent extraction processes. In the future, integration of process steps across the entire fuel cycle and increased attention to waste management and environmental considerations are anticipated.

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Abstract  

A method has been investigated for high-speed and efficient recovery of palladium from reprocessing waste of spent nuclear fuel by mixing the matrix feedstock with a small amount of KI and an appropriate inert solvent (such as kerosene) as collecting agent. Equilibrium of the reaction can be obtained in less than 30 sec. Percent recovery of palladium is more than 97%. Decontamination coefficient is high. No loss of effectiveness of the system was observed below 1×106 rad of irradiation.

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Abstract  

The laboratory apparatus used for the analysis of highly radioactive solutions produced by the Eurochemic plant in the chemical reprocessing of irradiated fuel, is described briefly. The analyses of the samples, which contain high concentrations of γ-emitting nuclides and plutonium, must be carried out in lead-shielded airtight boxes because of the radiation exposure hazard. A description of the remotely operated equipment for aliquot pipetting, density determination, potentiometric titration, extraction, dilution and colorimetric determination is given.

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Abstract  

A 10–5 mol 1–1 solutiopn of idododecane in n-dodecane was used to simulate a kerosene sample from nuclear fuel reporcessing. Several methods were developed for the quantitative removal of iodododecane from the n-dodecane solution. Decomposition to elemental iodine was achieved either by washing with hyperazeotropic nitric acid or by exposure to a high-intensity UV-light. Quantitative removal of iodododecane from n-dodecane was achieved by absorption on silver nitrate impregnated materila or on activated charcoal, which was impregnated with potassium thiocyanate or 1,4-diazabicyclo-2,2,2-octance. The reaction could be accelerated by stirring or heating. Thus a quantitative absorption of idododecane could be achieved within a few minutes. The results of the experiments were confirmed by absorption of iodoorganic compounds from kerosene of the Karl sruhe nuclear fuel reprocessing plant (WAK) on the tested material.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Ravi, S. Ravi, A. K. Deepa, A. K. Deepa, S. Susheela, S. Susheela, P. V. Achuthan, P. V. Achuthan, S. Anil Kumar, and U. Jambunathan

Summary  

A method has been developed for the estimation of 90Sr in reprocessed uranium oxide samples obtained from the Purex processing of natural uranium spent fuel discharged from the research reactor. The method employs a combination of precipitation and solvent extraction procedure to eliminate other beta-impurities prior to resorting to the estimation of 90Sr by beta-counting. 106Ru was eliminated by volatalizing with perchloric acid, uranium was removed by carrier precipitation with strontium as sulphate. The sulphate precipitate was converted to carbonate and dissolved in nitric acid. 234Th and 234Pa were eliminated by synergistic solvent extraction using tri-n-butyl phosphate and thenoyl trifluoroacetone extractant mixture in xylene. An iron scavenging step was included to remove any residual impurities. Finally, strontium is precipitated as SrC2O4 . H2O. The separated 90Sr activity was followed to check the equilibrium growth of 90Y.

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Abstract  

In kerosene samples from nuclear fuel reprocessing, iodoalkanes with chain-lengths from C4 to C13 have been identified. The kerosene samples were purified by means of solid-phase extraction. By this method other fission products like125Sb and106Ru were quantitatively removed from the solution. The only remaining radioactive nuclide was thus129I. The iodoorganic compounds in the kerosene from the solvent were enriched from 6000 Bq/L to 100 000 Bq/L129I by vacuum distillation. Chromatographic separation by HPLC, fractionation, and -measurement of the fractions showed that at least one polar and one nonpolar iodoorganic compound were present. Derivatisation of the iodoorganic compounds with, 1,4-diazabicyclo-2,2,2-octane to quatermary ammonium salts and252Cf plasma desorption mass spectrometry of the products revealed that the main iodoorganic constituents in the kerosene were iodobutane as polar and iodododecane as nonpolar compound in approximately equal concentrations.

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