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Encapsulation of High-Level Radwaste

#2959


High-Level Radioactive Waste Encapsulation with the Use of Pyrocarbon and Silicon Carbide Coatings

Tech Area / Field

  • CHE-ANL/Analytical Chemistry/Chemistry
  • ENV-RWT/Radioactive Waste Treatment/Environment
  • ENV-WDS/Waste Disposal/Environment

Status
3 Approved without Funding

Registration date
17.12.2003

Leading Institute
NPO Lutch, Russia, Moscow reg., Podolsk

Supporting institutes

  • State Enterprise Krasnaya Zvezda, Russia, Moscow\nKhlopin Radium Institute, Russia, St Petersburg\nAll-Russian Research and Designing Institute of Complex Energetic Technology, Russia, St Petersburg

Collaborators

  • Argonne National Laboratory (ANL) / West, USA, ID, Idaho Falls

Project summary

The objective of the proposed Project is increase of handling safety of high-level radioactive wastes (HLW) by deposition of pyrocarbon and silicon carbide protective coatings. The other goals of the work are: investigation of properties of prepared materials, substantiation of safety of encapsulated waste disposal in geological formations.

Among the most significant radionuclides in a composition of HLW determining the long-term potential danger are:

  • fission products 90Sr, 93Zr, 134Cs, 137Cs, 99Tc; 129I and other.
  • residual amounts of uranium, plutonium and neptunium;
  • transplutonium elements 241Am, 243Am, 242Cm, 244Cm and daughter radioactive products.

The necessity of isolation of wastes containing these radionuclides is extremely important and urgent problem of the countries having such waste in their territory. It is generally accepted to include waste into a stable matrixe (phosphate and borosilicate glass, glass-metal compositions, Synroc-type matrix).

At the same time it is difficult to predict behaviour of these materials disposed in geological formation under effect of radiation, heat and ground waters during period of few thousands years. In this connection search of additional artificial barriers on a path of radionuclides release from solidified high-level radioactive waste is carried out.

The basic requirements to such protective barriers are:

  • Radiation and chemical stability;
  • Low permeability including diffusion one;
  • Enough level of mechanical strength.

Pyrocarbon and silicon carbide meet these requirements and can be used as coating materials for solidified high-level radioactive wastes.

Within the framework of the Project it is offered to carry out various investigations, particularly:

  • Analysis of the nomenclature of high-level radioactive wastes for encapsulation, choice of the form and technology of wastes conditioning for encapsulation.
  • Choice of flow chart of pyrocarbon and silicon carbide coating deposition on solidified high-level radioactive wastes.
  • Designing and manufacture of experimental installation for encapsulation of high-level radioactive wastes simulators by deposition of pyrocarbon and silicon carbide coating on their surface.
  • Preparation of encapsulated products with simulators of high-level radioactive wastes, investigation of physicochemical properties of prepared materials.
  • Development of mathematical models and software for investigation and substantiation of safety of disposal of encapsulated high-level radioactive wastes in geological formations.

As the result of research and development work under the proposed Project will be:
  • Determined the list of high-level radioactive wastes and radionuclides composition (or separate fractions), composition of a matrix for solidified wastes and technology of solidification.
  • Chosen material and parameters of high-level radioactive wastes (or separate fractions) encapsulation.
  • Developed drawings, made equipment and mounted experimental installation for encapsulation of high-level radioactive waste simulators.
  • Carried out experiments on wastes encapsulation and investigation of physicochemical properties (strength, corrosion stability, diffusion permeability and other).
  • Developed software and conducted calculations on determination of coating parameters with maximum ecological effect.
  • Given initial data for large-scale installation for encapsulation of HLW with reference to problems of Industrial Association Mayak.

The work will be carried out with use of the special equipment. Leading experts in the field of waste processing, material science and mathematical modeling will be attracted for investigations.

Implementation of the proposed Project as a whole will allow to solve the problem of conditioning of high-level radioactive wastes more successfully and will ensure ecological safety of their disposal in geological formations.

The results of activity are of interest not only for Russian plants processing HLW, but also for all countries having radioactive waste in their territory being subject to disposal.


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