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Membrane Catalytic Reactor for Spent Fusion Fuel

#1984


Development of a Membrane Catalytic Reactor for Recovery of a Spent T-D Mixture of Fusion Facilities

Tech Area / Field

  • FUS-MCS/Magnetic Confinement Systems/Fusion
  • FUS-HSF/Hybrid Systems and Fuel Cycle/Fusion
  • MAN-MAT/Engineering Materials/Manufacturing Technology
  • MAT-ALL/High Performance Metals and Alloys/Materials

Status
3 Approved without Funding

Registration date
04.09.2000

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • A.V. Topchiev Institute of Petrochemical Synthesis, Russia, Moscow

Collaborators

  • Forschungszentrum Karlsruhe Technik und Umwelt / Tritium Laboratory, Germany, Karlsruhe\nMax-Plank-Institut für Plasmaphysik / ITER Joint Work Site, Germany, Garching\nTufts University, USA, MA, Medford\nENEA, Italy, Frascati\nForschungszentrum Karlsruhe Technik und Umwelt, Germany, Karlsruhe

Project summary

Tritium-deuterium gas mixture used as a fuel in fusion facilities deteriorates during the operation due to helium isotopes accumulation and occurrence of hydrogenous isotopes and other impurities caused T-D plasma interaction with structural materials.
Therefore, fuel cycle of such facilities must include the stage of a spent fuel gas mixture (SFGM) cleanup and recovery (extraction of tritium and deuterium from impurities containing hydrogen isotopes). Cleanup and recovery of SFGM is important with respect to gain in economy of fusion facilities, particularly, of energetic ones (e.g. thermonuclear reactor ITER being developed by the world community), and in terms of ecology (reduction of radioactive tritium release into the atmosphere).
Currently developed SFGM cleanup circuits are based on the use of selective permeability of Pd-base alloys to hydrogen isotopes; the problem of hydrogen isotopes extraction from hydrogenous impurities is usually solved by conducting appropriate chemical reactions on catalysts.
Known designs for SFGM cleanup are supposed to use apparatus with tubular-capillary filter elements (FE) made of Pd-base alloy dopped with silver, gold, platinum and ruthenium.
Apparatus with filter elements as a set of tubes of small diameter have some disadvantages:
· the lack of industrial technologies for making capillary tubes with less than 100m wall thickness restricts capacity of this apparatus design by productivity, lifletime and cost;
· complicated production technology of a filter unit composed of a large number of in-parallel-connected capillaries;
· low maintainability of tubular apparatus.
Available circuits of hydrogen isotops recovery are based on their transfer into free (elementary) state by means of one or other chemical reactions and their filtering from a mixed gas through palladium-base membranes. The change of hydrogen isotopes into a free state is carried out on catalysts placed in separate apparatus-catalytic reactors or inside capillary palladium tubes of the filtering purification apparatus.
Separate hydrogen isotopes filtration and extraction from impurities adds complexity introduction and overview to the SFGM recovery system and to its operation. Combination of these processes by placing catalyst into filtration capillaries of tubes adds much complexity to the design, technology and operation.
This project proposes to use the scheme combining hydrogen isotopes cleanup and extraction from impurities.
However, in contrast to other systems, specially prepared separation element and a filter membrane are planned to be used as a catalyst of hydrogen isotopes extraction from impurities. In this case catalytic decomposition of molecules should occur at surfaces of the separation element an membrane, but hydrogen and its isotopes removal from the mixture through membrane shifts reaction equilibrium toward final products production and increase in conversion degree, increasing the extent of hydrogen isotope extraction.
These bifunctional membranes were developed by the IPCS scientists.
In parallel with the use of a new membrane material, it is proposed to change from traditional tubular-capillary design of the apparatus for SFGM cleanup and recovery to design using flat membranes.
As shown by the analysis, this apparatus design will offer much higher performance and economic efficiency both at the production stage and in operation.
Idea of the project is based on works of scientists involved in the project implementation.
IPCS specialists are among leading Russian specialists in membrane technology of hydrogen purification and membrane catalysis.
VNIIEF project recipients have gained great experience and have considerable technical potential to develop apparatus and technologies for handling tritium-containing materials.
This project offers to develop apparatus in which:
· new palladium alloy will be used with better as compared with available, specific hydrogen permeability and physical-chemical properties, which is free of other hard-to-get and expensive precious metals;
· new filter element design will be developed with flat membranes, which will combine hydrogen isotopes recovery and cleanup, will be more technologically effective and reliable both in production and operation;
· 2,5 times higher specific efficiency of SFGM cleanup will be achieved in comparison with existing apparatus;
· with identical efficiency the proposed apparatus will contain 4-10 times less palladium, the elements will be 20 times cheaper than tubular ones, and apparatus will be 1.5 - 2 times cheaper than tubular - capillary designs.
The proposed project falls in the category of applied research in the operational development of fusion facilities fuel cycle, particularly ITER.
Results of research performed during the project implementation will be also of scientific and practical interest to specialists dealing with extremely pure hydrogen (chemical, metallurgical, semiconductor industry) or to those involved in hydrogenous product synthesis (chemical, food, pharmaceutical industry).
Hydrogen is also studied as environmentally safe fuel and effective energy carrier; in these areas, research planned in the project may be used to create hydrogen cleanup systems having better technical and economic characteristics in comparison with available ones.
Developed under the project design of laboratory apparatus for SFGM cleanup and recovery, and gained experience will allow the project participants further development of production prototypes of the apparatus for specific technological purposes.
Thus, the project implementation will result in the development of SFGM cleanup and recovery apparatus based on new materials and apparatus of advanced design.
Implementation of the project will make it possible for RFNC-VNIIEF specialists, involved in nuclear weapons development, to redirect their talents, technological and production activities to the solution of an acute international scientific and technical problem, as well as to contribute to the solution of FF SFGM cleanup and recovery problems and to the development of ultrapure hydrogen production technology.


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