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Spark plasma sintering of UO2 fuel composite with Gd2O3 integral fuel burnable absorber
Papynov E.K.,Shichalin O.O.,Belov A.A.,Portnyagin A.S.,Buravlev I.Yu,Mayorov V.Yu,Sukhorada A.E.,Gridasova E.A.,Nomerovskiy A.D.,Glavinskaya V.O.,Tananaev I.G.,Sergienko V.I. 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.8
The paper studies spark plasma sintering (SPS) of industrially used UO2-based fuel containing integral fuel burnable absorber (IFBA) of neutrons Gd2O3. Densification dynamics of pristine UO2 powder and the one added with 2 and 8 wt% of Gd2O3 under ultrasonication in liquid has been studied under SPS conditions at 1050, 1250, and 1450 C. Effect of sintering temperature on phase composition as well as on O/U stoichiometry has been investigated for UO2 SPS ceramics. Sintering of uranium dioxide added with Gd2O3 yields solid solution (U,Gd)O2, which is isostructural to UO2. SEM with EDX and metallography were implemented to analyze the microstructure of the obtained UO2 ceramics and composite UO2- Gd2O3 one, particularly, open porosity, defects, and Gd2O3 distribution were studied. Microhardness, compressive strength and density were shown to reduce after addition of Gd2O3. Obtained results prove the hypothesis on formation of stable pores in the system of UO2-Gd2O3 due to Kirkendall effect that reduces sintering efficiency. The paper expands fundamental knowledge on pros and cons of fuel fabrication with IFBA using SPS technology.
Papynov, E.K.,Belov, A.A.,Shichalin, O.O.,Buravlev, I. Yu,Azon, S.A.,Golub, A.V.,Gerasimenko, A.V.,Parotkina, Yu. А.,Zavjalov, A.P.,Tananaev, I.G.,Sergienko, V.I. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7
In the present study, an original spark plasma sintering-reactive synthesis (SPS-RS) method for minerallike ceramic materials based on SrAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub> feldspar-like skeleton structure was used for the first time, promising solid-state matrices for reliable immobilization of high-energy <sup>90</sup>Sr. The method is based on the "in-situ" reaction of a mixture of SrO, Al<sub>2</sub>O<sub>3</sub> and SiO<sub>2</sub> oxides when heated by a unipolar pulsed current under compacting pressure. The phase and elemental composition structure were studied. The dynamics of the consolidation of the reaction mixture of oxides was studied in the range of 900-1200 ℃. The study found the temperature of the high-speed (minutes) SPS-RS formation of single-phase SrAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub> composition ceramic in the absence of intermediate reaction products with a relative density of up to 99.2% and compressive strength up to 145 MPa and a strontium leaching rate of 10<sup>-4</sup>g/cm<sup>2</sup>·day.
Panasenko A.E.,Shichalin O.O.,Yarusova S.B.,Ivanets A.I.,Belov A.A.,Dran'kov A.N.,Azon S.A.,Fedorets A.N.,Buravlev I. Yu,Mayorov V. Yu,Shlyk D. Kh,Buravleva A.A.,Merkulov E.B.,Zarubina N.V.,Papynov E. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9
A new approach to the use of rice straw as a difficult-to-recycle agricultural waste was proposed. Potassium aluminosilicate was obtained by spark plasma sintering as an effective material for subsequent immobilization of 137Cs into a solid-state matrix. The sorption properties of potassium aluminosilicate to 137Cs from aqueous solutions were studied. The effect of the synthesis temperature on the phase composition, microstructure, and rate of cesium leaching from samples obtained at 800e1000 C and a pressure of 25 MPa was investigated. It was shown that the positive dynamics of compaction was characteristic of glass ceramics throughout the sintering. Glass ceramics RS-(K,Cs)AlSi3O8 obtained by the SPS method at 1000 C for 5 min was characterized by a high density of ~2.62 g/cm3 , Vickers hardness ~ 2.1 GPa, compressive strength ~231.3 MPa and the rate of cesium ions leaching of ~1.37 107 g cm2 $day1 . The proposed approach makes it possible to safe dispose of rice straw and reduce emissions into the atmosphere of microdisperse amorphous silica, which is formed during its combustion and causes respiratory diseases, including cancer. In addition, the obtained is perspective to solve the problem of recycling long-lived 137Cs radionuclides formed during the operation of nuclear power plants into solid-state matrices.