Papers by Julio Takehiro Marumo
Brazilian Journal of Radiation Sciences, Apr 30, 2021
Radiation-induced advanced oxidation processes have been proposed for the treatment of various ty... more Radiation-induced advanced oxidation processes have been proposed for the treatment of various types of wastes. However, electron beam technologies for the removal of recalcitrant compounds in petroleum wastes are still poorly understood. This work aims at evaluating the effects on the degradation of organic matter from oil sludge by electron beam irradiation. Characterization methods were employed to identify the chemical elements present in the waste. Radiometric analysis was performed to identify radionuclides and measure dose rates. Preliminary immobilization of the untreated waste with cement indicated resistance values very close to the minimum established in national regulation. To treat the waste, an electron beam accelerator, model Dynamitron II, with variable current up to 25 mA was employed and the irradiation doses ranged from 20 to 200 kGy. Solutions were prepared with an initial H 2 O 2 concentration of 1.34 mol•L-1. The effects on the removal of total organic carbon are discussed.
Environmental Science and Pollution Research, Jun 20, 2020
Rice and coffee husks (raw and chemically activated) are examined as potential biosorption materi... more Rice and coffee husks (raw and chemically activated) are examined as potential biosorption materials regarding their capacity to remove U (total), 241 Am, and 137 Cs. The physical parameters evaluated were the morphological characteristics of the biomass, real and apparent density, and surface area. Contact times for the batch experiments were 0.5, 1, 2, and 4 h, and the concentrations tested ranged between 10% of the total concentration and the radioactive waste itself without any dilution. The results were evaluated by experimental sorption capacity, ternary isotherm, and kinetics models. The kinetics results showed that equilibrium was reached after 2 h for all biomass. Raw coffee husk showed the best adsorption results in terms of maximum capacity (q max) for all three radionuclides, which were 1.96, 39.4 × 10 −6 , and 46.6 × 10 −9 mg g −1 for U, Am, and Cs, respectively. The biosorption process for the raw and activated rice husks was best represented by the Langmuir ternary isotherm model with two sites. For the coffee husk, in the raw and activated states, the biosorption process was best described by the modified Jain and Snoeyink ternary model. These results suggest that biosorption with these biomaterials can be applied in the treatment of liquid organic radioactive waste containing mainly uranium and americium.
The ion-exchange resin is commonly used in the cooling water purification of nuclear reactors, fo... more The ion-exchange resin is commonly used in the cooling water purification of nuclear reactors, for removing radioactive elements. As the resin is used for long periods of time inside the reactor system, it becomes radioactive. After the useful life of the resins is over, its reutilization becomes inappropriate, and for that reason, the resin is considered radioactive waste. To ensure environment security, the direct solidification of spent ion exchange resin by cementation is currently the main immobilization process, decreasing its release to the environment. This immobilization consists in a mixture of water, cement and radioactive waste. Because of its characteristic of contraction and expansion, the incorporation of resin is limited in 10%, causing high costs in its direct immobilization. Therefore, it is recommended the utilization of a pre-treatment, capable of reducing the resins volume, degrading them, and increasing the load capacity in the immobilization. This work aims to develop a method of degradation of ion spent resins from the nuclear research reactor of Nuclear and Energy Research Institute (IPEN), Brazil, using the Fenton's reagent (hydrogen peroxide and a catalyst). Three forms of the resin were used: cationic (IR 120P), anionic (IRA 410) and a mixture of both resins. The reactions were conducted by varying the amounts of catalyst, hydrogen peroxide and temperature. The resin degradation was confirmed by the presence of CaCO 3 as a white precipitate resulting from the reaction between the Ca(OH) 2 and the CO 2 from the resin degradation. The experiments showed two good different types of method to degrade the resin. One of them is used for cationic or anionic resin and, the other, was used for a mixture of them. Both of these methods will be described in this work with their respective results.
Portland cement materials are widely used as engineered barriers in repositories for radioactive ... more Portland cement materials are widely used as engineered barriers in repositories for radioactive waste. The capacity of such barriers to avoid the disposed of radionuclides to entering the biosphere in the long-term depends on the service life of those materials. Thus, the performance assessment of structural materials under a series of environmental conditions prevailing at the environs of repositories is a matter of interest. The durability of cement paste foreseen as backfill in a deep borehole for disposal of disused sealed radioactive sources is investigated in the development of the repository concept. Results are intended to be part of the body of evidence in the safety case of the proposed disposal technology. This paper presents the results of X-Ray Diffraction (XRD) Analysis of cement paste exposed to varying temperatures and simulated groundwater after samples received the radiation dose that the cement paste will accumulate until complete decay of the radioactive sources.
Journal of Radioanalytical and Nuclear Chemistry, Jun 10, 2012
Ion-exchange resins and activated charcoal beds are employed for purification of the cooling wate... more Ion-exchange resins and activated charcoal beds are employed for purification of the cooling water that is pumped through the core of pool type nuclear research reactors. Once expended, these media are replaced and become radioactive wastes that contain low concentrations of long-lived fission and activation products, uranium isotopes and transuranium elements. Determination of the radioactive inventory is of paramount importance in the management of such radioactive wastes, which, besides high-energy photon emitters that can be identified and quantified directly by gamma-ray spectrometry, also contain pure alpha, pure beta and low-energy photon emitters whose quantitative determination require radiochemical separation. These later are collectively known as difficult to measure (DTM) radionuclides. A characterization program embracing the DTM radionuclides is currently in progress for spent ion-exchange resins and activated charcoal beds that were definitively withdrawn from the water cleanup system of the IEA-R1 nuclear research reactor. Radiochemical methods used in the characterization program include separations with specific anionic resins, chromatographic extractions and co-precipitation, which enabled the measurement of the activity concentrations of 90 Sr, 234 U, 235 U, 238 U, 238 Pu, 239?240 Pu, 241 Pu, 241 Am and 244 Cm. An enhanced retention of uranium and transuranium elements was observed in the activated charcoal compared to the ion-exchange resins as a result of the tendency of actinides to undergo hydrolysis in aqueous solutions.
Environments, Nov 15, 2018
One of the most common treatment methods for spent ion exchange resins is their immobilization in... more One of the most common treatment methods for spent ion exchange resins is their immobilization in cement, which reduces the release of radionuclides into the environment. Although this method is efficient, it considerably increases the final volume of the waste due to its low incorporation capacity. This work aims to evaluate the degradation of ion exchange resins by the Fenton process (H 2 O 2 /Fe 2+). The resin evaluated was a mixture of cationic and anionic resins, both non-radioactive. The reactions were conducted by varying the catalyst concentration (25, 50, 100, and 150 mmol L −1) and the volume of hydrogen peroxide. Three different temperatures were evaluated by varying the flow of reactants, which were 50, 60, and 70 • C. Cement specimens were prepared from the treated solutions and two parameters were assessed-namely, final setting time and axial compressive strength. The results showed that the experimental conditions were suitable to dissolve the resins, and the Fe 3+ produced as precipitate during the experiments increased the resistance of the final product. The immobilized product complied with the limits established by regulation.
International Journal of Environmental Science and Technology, Sep 13, 2017
The treatment of radioactive liquid waste containing organic compounds was always a cause for con... more The treatment of radioactive liquid waste containing organic compounds was always a cause for concern to radioactive waste management facilities because the processes available are expensive and difficult to manage. Biosorption has been studied as a new process in simulated wastes as an alternative to treating them. Among the potential biomass, the coconut fiber has very attractive features that allow the removal of radionuclides using a low-cost biosorbent. The aim of this study was to evaluate the capacity of coconut fiber to remove uranium, americium, and cesium from real radioactive liquid organic waste. Experiments with the biosorption of these radionuclides in coconut fiber were made including (1) preparation, activation, and characterization of biomass and (2) biosorption assays. The biomass was tested in raw and activated form. Biosorption assays were performed, adding the biomass to real waste solutions. The solutions contain natural uranium, americium-241, and cesium-137. The contact times and the concentrations range were varied. The radioisotopes remaining concentration in the solutions was determined by inductively coupled plasma optical emission spectrometry and gamma spectrometry. The results were evaluated by maximum experimental sorption capacity and isotherm and kinetics ternary models. The highest sorption capacity was observed with the activated coconut fiber, with values of 2 mg/g of U (total), 70E-06 mg/g of Am-241 and 40E-09 mg/g of Cs-137. These results suggest that biosorption with activated coconut fiber can be applied in the treatment of radioactive liquid organic wastes containing uranium, americium-241, and cesium-137.
Waste Management Symposia, Oct 28, 2020
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Papers by Julio Takehiro Marumo