Development of the process regime for cementing salt concentrates from the Volgodonsk nuclear power plant

Zakharova, K. P.; Khimchenko, O. M.; Sukhanov, L. P.; Александров, В. В.; Sal’nikov, A. A.; Khromovskikh, E. V.; Pushkarev, V.V.

doi:10.1007/s10512-007-0140-x

Cited by 5 publications

(5 citation statements)

References 2 publications

(1 reference statement)

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“…High ability of clay materials to sorb Cs radionuclides allows the use of these materials as additives in cementation of liquid radioactive wastes, in particular, of NPP bottom residues [7]. When studying the effect of various clay materials on the strength of cement matrices and on the radiocesium leaching from them, we used a solution simulating additionally evaporated bottom residue from an NPP with RBMK reactor.…”

Section: Cementation Of Npp Bottom Residuesmentioning

confidence: 99%

Sorption of Cs, Sr, U, and Pu radionuclides on natural and modified clays

et al. 2012

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The ability of natural and modified montmorillonite clays from Belgorod oblast to sorb Cs, Sr, U, and Pu radionuclides was studied. The clays were modified by treatment with metal (Li + , Na + , K + , Mg 2+ , Ca 2+ , Fe 2+ , Zn 2+ ) chloride solutions or aqueous HCl. The natural and modified clays studied show high performance in sorption treatment of solutions to remove Cs radionuclides. The natural clay and the Na and Mg forms of clays show the best sorption characteristics with respect to Cs. The distribution coefficient K d of 137 Cs in sorption on the above samples from a 0.1 M NaNO 3 solution is (1.1-1.4) × 10 4 cm 3 g -1 , which is 4-5 times higher compared to natural clinoptilolite. The Sr, U, and Pu radionuclides are sorbed on the examined clay samples to a considerably lesser extent. The K d values in sorption of these radionuclides from tap water are lower by 2-3 orders of magnitude than in sorption of Cs. Addition of clay materials in the course of cementation of liquid radioactive wastes, including NPP bottom residues, allows the rate of radiocesium leaching from the hardened cement compounds to be decreased by a factor of 5-16. The most efficient sorption additive in cementation of NPP bottom residues is natural montmorillonite clay.

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Section: Cementation Of Npp Bottom Residuesmentioning

confidence: 99%

Sorption of Cs, Sr, U, and Pu radionuclides on natural and modified clays

et al. 2012

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“…However, the nuclear power plant bottoms have a more complex chemical composition differing from that indicated above by, first and foremost, the presence of sodium borate and sodium and potassium hydroxides in substantial concentrations (tens and hundreds of grams per liter) as well as oxalates and complexones (e.g., EDTA) and surfactants (e.g., OP-10) [10,11]. This greatly complicates hydration and solidification processes for the cement material and can negatively affect the properties of the cement compound.…”

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confidence: 94%

“…This greatly complicates hydration and solidification processes for the cement material and can negatively affect the properties of the cement compound. For example, it is known that tetraborates retard hydration of cement considerably [10]. The effect of the components listed above on the properties of the matrix material developed for direct-pour cells was studied in the present work.…”

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confidence: 97%

“…A model solution of nuclear power plant bottoms from evaporation of liquid radwastes was used to study solidification. The composition of this solution was chosen on the basis of the data from [10][11][12] and is presented in Table 1. A solution modeling medium-level wastes from radiochemical production containing 300 g/liter sodium nitrate was used for comparison.…”

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confidence: 99%

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Direct-pour cementation of nuclear power plant bottoms

Козлов¹,

Slyunchev²,

Kir'yanov

et al. 2012

At Energy

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The possibility of cementing nuclear power plant bottoms and storing the compound obtained in direct-pour cells is examined. The results of development work on a similar technology for solidifying medium-level liquid wastes from radiochemical production at the Industrial Association Mayak are shown. Experimental results on solidification of nuclear power plant bottoms using the prescriptions developed are presented. The flowability, water separation, and heat emission during solidification of cement solutions as well as the strength and water-and freeze-resistance of the solidified compound are determined. The proposed mix ensures that the cement compound with the solidified, nuclear power plant bottoms meets the technological and normative requirements.One of the principal forms of radwastes from nuclear power plants are the bottoms from evaporation of low-and medium-level liquid wastes. Such wastes are solidified by cementation. This is explained by the comparative simplicity of the practical implementation and satisfactory quality of the compound obtained [1].Solidification can be conducted in a special periodic-or continuous-action mixer after which the cement solution is dispensed into containers or a repository cell as well as directly in the container used for storing the compound. The continuous operating mode of the mixer is more productive, but in this method it is difficult to secure composition constancy of the compound. The periodic regime permits more accurate dispensing of the components at each operation. Ordinarily, steel drums or concrete containers with volume 1-3 m 3 are used as the storage volume. Containers can be moved and classified, for example, according to the type and activity of the solidified wastes and the monitoring status of the packing. In addition, heightened requirements are not imposed on the mobility of the cement solution and the heat-release during hydration. It should be noted that this is the most widely used technical solution for nuclear power plants.The drawbacks of this storage method are a larger number of technological operations, considerable cost of the containers, and suboptimal filling of the storage volume. These drawbacks are absent when the compound is placed in directpour facilities, where the solidified wastes are placed directly into large-volume cells -about 100 m 3 -whose walls are an engineered barrier.The solidification of high-salt content wastes from the GTF facility in the radiochemical complex at Hanford (USA) can serve as an example of the organization of the process. In the 1980s, 3800 m 3 of sulfate-phosphate liquid radioactive wastes were solidified and placed in storage [2]. The 38 m long, 15 m wide, and 10 m deep reinforced concrete storage cell with walls ranging in thickness from 0.6 to 1.2 m at height 9.1 m was filled with cement compound. The remaining space

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“…matrix [5]. Evidently, cementing at elevated temperature complicates the apparatus used for the process.…”

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confidence: 99%

Incorporation of bottoms from nuclear power plants into a matrix based on portland cement and silicic additives

2011

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The solidification of partially evaporated bottoms of RBMK and VVER with salt concentration 500-650 g/liter by compositional binders consisting of Portland cement and silicic additives -aerosil, microsilica, opoka, silicic acid, liquid glass, and diatomite is examined. The additions were used to obtain matrices that satisfy the requirements of safe storage of cemented radwastes. The partition coefficients of 137 Cs in partially evaporated bottoms are determined for all additives studied. The most effective additive for solidification of partially evaporated bottoms of VVER is diatomite. Matrices with diatomite have strength 50-81 kg/cm 2 , the rate of leaching of 137 Cs ~ 10 -3 -10 -4 g/(cm 2 ·day) and the fill with respect to salts reaches 20.9 wt.%. On the solidification of partially evaporated RBMK bottoms the most effective hardening additives are aerosil and microsilica and the most effective sorbing additives are bentonite, opoka, and diatomite. The matrices so obtained have strength 59-93 kg/cm 2 , 137 Cs leach rate ~ 10 -3 -10 -4 g/(cm 2 ·day) and contain to 25.1 wt.% salts.The liquid radwastes formed during the operation of a nuclear power plant are mainly in the form of the bottoms of evaporation facilities. Since the capacities of storage facilities for the bottoms of most nuclear power plants are close to being filled, they must be freed up by converting the bottoms into the solid state. Liquid bottoms can be converted into solid radwastes by means of cementing, bituminization, and deep evaporation resulting in a salt melt. The simplest and most readily available method is cementing. The main drawbacks of this method are low strength of the cement matrices, low filling with respect to salts, long setting time, i.e., low rate of solidification, incomplete solidification of the liquid phase with high water/cement ratio [1]. The filling of the matrix with respect to salts can be achieved by increasing the concentration of dissolved substances in the solidified solution and the water/cement (W/C) ratio. Any increase of the concentration of dissolved substances by additional evaporation of the bottoms is limited by the maximum solubility of the salts contained in them, and increasing the W/C ratio above 0.5 decreases the strength of cement matrices.Cemented solid wastes must satisfy the following requirements: the strength under bilateral compression must be at least 4.9 MPa, the 137 Cs leach rate must be at least 1·10 -3 g/(cm 2 ·day), the decrease of the strength of the compound after tests for freeze resistance and after holding in water for 90 days must be no more than 25% [2].The best known and effective method of increasing the strength of cement matrices with W/C > 0.5 is introducing into the composition a reinforcing additive -asbestos [3,4]. The drawback of this method is a sharp decrease of the mobility of the cement suspensions, which impedes their output from the mixer.At the Volgodonskaya nuclear power plant the partially evaporated bottoms with salt concentration 700-1000 g/liter are solidifi...

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Development of the process regime for cementing salt concentrates from the Volgodonsk nuclear power plant

Cited by 5 publications

References 2 publications

Sorption of Cs, Sr, U, and Pu radionuclides on natural and modified clays

Sorption of Cs, Sr, U, and Pu radionuclides on natural and modified clays

Direct-pour cementation of nuclear power plant bottoms

Incorporation of bottoms from nuclear power plants into a matrix based on portland cement and silicic additives

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