PREVENTION OF RADIOACTIVE AND SOME OTHER CONTAMINANTS PROPAGATION INTO THE GROUNDS BY SHSMETHOD

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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
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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)

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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)

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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.

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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
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The chemical composition of the model material
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The optimum diameters of sphere agglomerates for
any welding mixture

• k is the reactor space factor ( ratio of
  agglomerates volume (4/3 p r3 . n) to total
  volume off reactor),
• ?a is the density of agglomerates,
• ?wm is the density of the welding mixture,
• Ca is 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

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Agglomerates of ground caked into a block by
SHS-method with the composition on the basis of
Fe3O4 and chromite concentrate
Tcomb1950oC CaO-Al2O3-SiO2 sintering temperature
1300-1540oC
Magnetite Algt Fe3O4, Fe, FeAl2O4
ChromiteAlgt FeCr2O4, (Mg,Fe)(Al0.75Cr0,25)O4
Bulk density of SHS mixture on base Fe3O4 is
2g/cm3
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Water-stability of caked agglomerates of ground
with different welding mixtures and space factor
of the reactor (from 0.5 to 0. 7)

• B - Fe3O4Al (k 0.5) C - Fe3O4Al (k 0.6)
  D - Fe3O4Al (k 0.7)
• E - Fe2O3Al (k 0.5) F - chromite
  concentrate Fe2O3Al (k 0.5)
• G - chromite concentrate Fe2O3Al (k 0.6)
  H
  - chromite concentrate Fe2O3Al (k 0.7)

740 hours 30 days
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Change of mass of matrix sample under the
long-term influence of 30 nitric acid

• B - Fe3O4Al (k 0.5) C - Fe3O4Al (k 0.6)
  D - Fe3O4Al (k 0.7) E - Fe2O3Al (k
  0.5) F - chromite concentrate Fe2O3Al (k
  0.5) G - chromite concentrate Fe2O3Al (k
  0.6)
  H - chromite concentrate Fe2O3Al (k
  0.7)

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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
  reaction3Si 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.

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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.