Optimisation by mathematical modeling of physicochemical characteristics of concrete containers in radioactive waste management

A method for obtaining an optimal concrete container composition used for storing radioactive waste from nuclear power plants is developed. It is applied to the radionuclides 60Co, 137Cs, 85Sr, and 54Mn. A set of recipes for concrete composition leading to an optimal solution is given

The role of intraparticle diffusion in the sorption of Cu2+ ions onto hydroxyapatite

The Cu2+ sorption onto HAP was investigated as a function of time, in the concentration range 5·10-4 - 5·10-3 mol/dm3. The experimentally obtained kinetic data were fitted with the intraparticle diffusion model. The correlation coefficients were low considering the overall reaction period. However, q versus t0.5 plots could be divided into three segments, out of which the second linear segment can be attributed to the intraparticle diffusion. Intraparticle diffusion rate constants (ki) increased from 3.57·10-3 to 7.80·10-3 mmol/g min0.5 with the increase of the initial Cu2+ concentration. As the lines did not pass through the origin it was concluded that intrapaticle diffusion is not the only rate-controlling step.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Ispitivanje uticaja fizičko-hemijskih svojstava sorbenata koštanog porekla na imobilizaciju jona Co2+ i Sr2+

Cilj istraživanja predstavlja ispitivanje mogućnosti imobilizacije jona Co2+ i Sr2+ sirovim i tretiranim životinjskim kostima kao biosorbentom. Određivan je uticaj različitih tretmana (hemijske degradacije, degradacije na povišenim temperaturama) na fizičko-hemijska svojstva životinjskih kostiju. Za karakterizaciju uzoraka životinjskih kostiju korištene su standardne metode: termička analiza (TG-DTG-DTA), infracrvena spektroskopska analiza (IC), rendgenska difrakciona analiza (XRD), BET metoda određivanja specifične površine, određivanje tačke nultog naelektrisanja metodom uravnotežavanja, dok je atomska apsorpciona spektrometrija - AAS korištena za merenje koncentracije jona metala. Na osnovu fizičko-hemijskih analiza biosorbenata, kao i poređenja kapaciteta i mehanizama imobilizacije jona Co2+ i Sr2+, uspostavljene su korelacije između različitih tretmana, strukture i sorpcionih svojstava

The evaluation of radionuclides removal using clinoptilolite, hydroxyapatite and their mixtures

The sorption properties of clinoptilolite and hydroxyapatite towards Cs1+, Co2+, and Sr2+ ions were compared, under the same experimental conditions. Cs1+ was preferably sorbed by natural clinoptilolite. Conversely, synthetic hydroxyapatite exhibited higher sorption capacities for Co2+ and Sr2+, while the sorption of Cs1+ was negligible. It was shown that, as a consequence of different affinity towards investigated cations, application of mixed clinoptilolite/hydroxyapatite sorbent represents a good strategy for the purification of effluents containing a mixture of Cs1+, Co2+ and Sr2+.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Poređenje japanskih i srpskih bentonita u kompoziciji cement-jonoizmenjivačka smola-bentonitna glina

To assess the safety of disposal of radioactive waste material in cement, curing conditions and time of leaching radionuclides 137Cs have been studied. Leaching tests in cement-ion exchange resins-bentonite matrix, were carried out in accordance with a method recommended by IAEA. Curing conditions and curing time prior to commencing the leaching test are critically important in leach studies since the extent of hydration of the cement materials determines how much hydration product develops and whether it is available to block the pore network, thereby reducing leaching. Incremental leaching rates Rn(cm/d) of 137 Cs from cement-ion exchange resins-bentonite matrix after 60 days were measured. In this paper we compared two bentonite clay as sorption componente, from Japan and Serbia. The results presented in this paper are examples of results obtained in a 30-year concrete testing project which will influence the design of the engineer trenches system for future central Serbian radioactive waste disposal center.Da bi se procenila bezbednost odlaganje radioaktivnog otpadnog materijala u cementu, prouĉavan je stepen izluţivanja radionuklida 137Cs. Testovi izluţivanja radjeni su za kompoziciju cementa-jonoizmenjivaĉke smole i bentonita i sprovedene su u skladu sa postupkom preporuĉenog od IAEA. Vreme sušenja pre otpoĉinjanja liĉing testa je od suštinske vaţnosti u studijama izluţivanja, jer uticaj hidratacije cementa odreĊuje koliko se hidratacija proizvoda razvija i da li je od uticaja na blokadu pora, ĉime se smanjuje curenje radionuklida iz matriksa . U ovom radu poredjena su dva bentonita kao sorpcione komponente , iz Japana i Srbije . Rezultati prikazani u ovom radu su primeri rezultata 30-godišnjeg projekta sistema inţenjerskih rovova za buduće srpsko centralno odlagalište radioaktivnog otpada.XXVIII Симпозијум Друштва за заштиту од зрачења Србије и Црне Горе, 30. септембар - 02. октобар 2015.Proceedings: [https://vinar.vin.bg.ac.rs/handle/123456789/9668

Mathematical modelling of immobilization of radionuclides Cs-137 and Co-60 in concrete matrix

Transport phenomena involved in the leaching of a radioactive material from a cement composite matrix are investigated using an empirical method employing a polynomial equation. To assess the safety for disposal of radioactive waste-cement composition, the leaching of Cs-137 and Co-60, from a waste composite into a surrounding fluid has been studied. Leaching tests were carried out in accordance with a method recommended by IAEA. Determination of retardation factors, K-F and coefficients of distribution, k(d), using a simplified mathematical model for analyzing the migration of radionuclides, have been developed. Transport phenomena involved in the leaching of a radioactive material from a cement composite matrix are investigated using an empirical method employing a polynomial equation. In our experiment we have analized mechanism of Cs-137 and Co-60 leaching values during a period of 60 days. Results presented in this paper are examples of results obtained in a 25-year mortar and concrete testing project, which will influence the design of the engineered trenches system for a future central Serbian radioactive waste storage center. (C) 2010 Elsevier Ltd. All rights reserved

Immobilization of Cs-137 and Co-60 in concrete matrix

To assess the safety for disposal of radioactive waste-cement-bentonite composition, the leaching of Cs-137 and Co-60, from a waste composite into a surrounding fluid has been studied [Burns, R.H. Atomic Energy Rev. 9 (1971) 547; Hashimoto, I., Deshpande, K.B. and Thomas, S.H. I and EC Fundamentals 3 (1964) 213]. Leaching tests were carried out in accordance with a method recommended by IAEA [Atomic Energy Rev. 9 (1971) 195]. Determination of retardation factors, K-F and coefficients of distribution, k(d), using a simplified mathematical model for analyzing the migration of radionuclides, has been developed. In our experiment we have achieved the lowest leaching values after 60 days. Results presented in this paper are examples of results obtained in a 20 year mortar and concrete testing project, which will influence the design of the engineered trenches system for a future central Serbian radioactive waste storage center. (C) 2003 Elsevier Ltd. All rights reserved

Leaching study on the process of solidification of radionuclide Co-60 in concrete

To assess the safety for disposal of radioactive waste-cement composition, the leaching of Co-60 from a waste composite into a surrounding fluid has been studied. Leaching tests were carried out in accordance with a method recommended by the IAEA. Determination of retardation factors, K, and coefficients of distribution, k(d), using a simplified mathematical model for analyzing the migration of radionuclides, has been developed. Results presented in this paper are examples of results obtained in a 30-year mortar and concrete testing project, which will influence the design of the engineered trench system for a future central radioactive waste disposal center

Leaching of Cs-137 from spent ion exchange resins in cement-bentonite clay matrix

The leaching rate of Cs-137 from the spent cation exchange resins in cement-bentonite matrix has been studied. The solidification matrix was a standard Portland cement mixed with 290350 (kg/m(3)) spent cation exchange resins, with or without 2-5% of bentonite clay. The leaching rates from the cement-bentonite matrix for Cs-137:(3.2- 6.6) x 10(-4)(cm/d), after 125 days were measured. From the leaching data the apparent diffusivity of cesium in cement-bentonite clay matrix with a waste load of 290-350 (kg/m(3)) spent cation exchange resins was measured for Cs-137: (1,5- 26) x 10(-5)(cm(2)/d), after 125 days. The results presented in this paper are part of the results obtained in a 20-year mortar and concrete testing project, which will influence the design of radioactive waste management for a future radioactive waste disposal center

Effect of curing time on the fraction of Cs-137 from cement matrix

To assess the safety of disposal of radioactive waste material in concrete, curing conditions and time of leaching radionuclides Cs-137 have been studied. Leaching tests in concrete were carried out in accordance with a method recommended by IAEA [Atomic Energy Review 9 (1971) 195-207]. Curing conditions and curing time prior to commencing the leaching test are critically important in leach studies since the extent of hydration of the cement materials determines how much hydration product develops and whether it is available to block the pore network, thereby reducing leaching. Results presented in this paper are examples of results obtained in a 10-year concrete testing project which will influence the design of the engineer trenches system for future central Serbian radioactive waste storing center. (C) 2003 Elsevier Science Ltd. All rights reserved