Prevention of Contaminant Propagation into Grounds using SHS Method

1. PREVENTION OF RADIOACTIVE AND SOME OTHER CONTAMINANTS PROPAGATION INTO THE GROUNDS BY SHS-METHOD G. KSANDOPULOa, A. BAIDELDINOVAb, S. KARTKUZHAKOVb G. XANTHOPOULOUc, a. ICP, Almaty - Kazakhstan b. "Floga" company, Almaty - Kazakhstan c. Demokritos Institute - Athens - Greece  Athens, 8-9 October 2008

2. MAIN PURPOSE • Processing of greater amounts of polluted components for utilization of radioactive and chemically dangerous wastes and neutralization of polluted materials, for prevention their migration into the soil and to adjacent ambiences (atmosphere and hydrosphere)

3. Methods of radioactive and chemically dangerous wastes isolation • Immobilization into phosphate and borosilicate glasses (do not prevent radionuclides penetration into the environment in the case of long- term burial) • Obtaining matrix materials (mineral-like ceramics analogs rock forming minerals is more stable thermodinamically than glasses) • Cold pressing with following annealing • Hot pressing • Synthesizing from melt All this 3 methods connected with complicate equipment, heat- and corrosion-resistant materials for crucibles, high energy consumption 4. SHS (technological simplicity, absence of external heating sources and complicate equipment)

4. MAIN IDEA • Agglomeration of the ground in separate matrixes by means of a binding agent (10-% solution of sodium tetraborate (Na2B2O4· 4H2O) and 10-% solution of sodium tetraborate with sodium monosilicate (Na2B2O4· 4H2O + Na2SiO3· 9H2O) • Packing them into natural reactors (pits, trenches) • Filling the empty spaces between them with the charge of welding mixture (combustible mixture, composed of metal oxide and a reducer, for example, powdered aluminium) • Initiation of combustion in the wave regime.

5. Main components of the soil samples taken in the Semipalatinsk region of Kazakhstan Also: Al2(Si,Al)4O10(OH)2, chamozit (Fe, Mg,Mn,Al)6(Si,Al)4O10 ,amorphous phase

6. The chemical composition of the model material

7. The optimum diameters of sphere agglomerates for any welding mixture kis the reactor space factor ( ratio of agglomerates volume (4/3πr3 .n) to total volume off reactor), ρais the density of agglomerates, ρwm is the density of the welding mixture, Cais the heat capacity of agglomerates, qwm is the heat effect of SHS reaction, Tmt is the ground caking temperature, h is the thickness of recrystallizated layer of the agglomerate

8. Agglomerates of ground caked into a block by SHS-method with the composition on the basis of Fe3O4 and chromite concentrate Tcomb=1950oC CaO-Al2O3-SiO2 sintering temperature 1300-1540oC Magnetite +Al=> Fe3O4, Fe, FeAl2O4 Chromite+Al=> FeCr2O4, (Mg,Fe)(Al0.75Cr0,25)O4 Bulk density of SHS mixture on base Fe3O4 is 2g/cm3

9. Water-stability of caked agglomerates of ground with different welding mixtures and space factor of the reactor (from 0.5 to 0. 7) B - Fe3O4+Al (k = 0.5); C - Fe3O4+Al (k = 0.6); D - Fe3O4+Al (k = 0.7); E - Fe2O3+Al (k = 0.5); F - chromite concentrate +Fe2O3+Al (k = 0.5); G - chromite concentrate +Fe2O3+Al (k = 0.6); H - chromite concentrate +Fe2O3+Al (k = 0.7) 740 hours = 30 days

10. Change of mass of matrix sample under the long-term influence of 30% nitric acid • B - Fe3O4+Al (k = 0.5); C - Fe3O4+Al (k = 0.6); D - Fe3O4+Al (k = 0.7); E - Fe2O3+Al (k = 0.5); F - chromite concentrate +Fe2O3+Al (k = 0.5); G - chromite concentrate +Fe2O3+Al (k = 0.6); H - chromite concentrate +Fe2O3+Al (k = 0.7)

11. Optimization • The soil radioactive components fixing optimization in mechanically strong block with chemically stable spinel matrix is possible due to preparation of sphere soil agglomerates of 2 sizes.Due to such approach reduced welding composition quantity and increased volume of roasting soil of one load. This led to economy of expensive material and makes cheaper all technology. • Replacement of reducer, expensive aluminum powder with cheaper component. Silicon and its alloys(for example, Al-Si alloy silumin) can be used as reducer in metallo-thermic processes. First of all thermal effect of silicon reaction with iron oxide is enough high. For the reaction:3Si + 2Fe2O3 → 4Fe + 3SiO2 it is – 2462 J/g or 980,2 kJ/mol. Secondary, the main silumin phase is aluminium; silicon content is 3 and more percent. The most approachable piston silumin contains 11-13% of silicon. Thirdly, the silumin wastes (cars pistons) are cheap raw material. Thermo-physical parameters of SHS process with silumin use show, that there is phase recrystallization of soil agglomerate surface layer in the reactor and formation of minerals (quartz, corundum, albite, hercynite) as a result of layers combustion. According to the tests this composition has satisfactory to requirements mechanical and chemical resistance according to tests.

12. Conclusion • The elaborated method of immobilization of radioactive and chemically dangerous components spread in grounds uses the peculiarities of self-propagating high-temperature synthesis combined with agglomeration of polluted materials. • SHS based on processes of combustion allows obtaining refractory minerals which are similar to natural ones in the structure and phase composition having mechanical strength and high chemical stability. • Agglomeration provides the possibility for treatment and decontamination of greater volumes of polluted materials with considerably less consumption of welding SHS-mixture and, hence, its most expensive component – powdered aluminium. • The proposed technology provides high degree of mechanization process that it is important, when working with harmful substances.