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Neutron Multiplier for ITER Blanket

#3987


Examination of Radiation-Induced Damage in Candidate Materials of Neutron Multiplier for the Test Blanket Module of the International Thermonuclear Experimental Reactor (ITER)

Tech Area / Field

  • FIR-MAT/Materials/Fission Reactors
  • PHY-SSP/Solid State Physics/Physics

Status
3 Approved without Funding

Registration date
09.09.2009

Leading Institute
NIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad

Collaborators

  • Forschungszentrum Karlsruhe Technik und Umwelt / Institute für Materialforschung, Germany, Karlsruhe

Project summary

Project goal. This Project is aimed to develop methodology of high temperature irradiation tests of beryllium specimens and its compounds at radiation damage and gas transmutant accumulation rates close to those planned under fusion reactor conditions, as well as to study beryllium structure evolution at irradiation temperatures of 450 - 800°C and damage dose of 1 dpa.

Investigation state. Beryllium is a promising material for fusion reactors application. Beryllium will be used as a plasma facing material in the first wall of the vacuum chamber and as a neutron multiplier in the test blanket module of the first International Thermonuclear Experimental Reactor (ITER) which is under construction in Cadarache, France. Parameters of beryllium irradiation in ITER reactor as a prototype of the II Generation fusion reactor (DEMO) will be as allows: operating temperatures 250-850ºC, damage dose of the order of 1 dpa.

This is a few work aimed to investigations of radiation damage of beryllium and its compounds under high temperature neutron irradiation (above 400°C), however, the existing work witnesses that at the high temperatures, the diffusive mobility of gas transmutants intensively accumulated in beryllium under fusion reactor operation increases significantly. The mobile gas atoms diffuse in the grain body and on the grain boundaries and form gas-filled pores or bubbles. In practice, these processes lead to changes in geometry and structure distortion as well as to material cracking and flaking. Thus, experimental study of beryllium structure damage at high irradiation temperatures is very urgent.

In regard to methodology, the problem consists in the fact that the fusion reactor spectrum has a large part of neutrons at the energy of 14 MeV which assures simultaneously high rates of radiation damage and gas transmutant accumulation. Thus, to valuable study of structural changes in beryllium, it is necessary to use special neutron sources that are the far future task. This work proposes to use the fact that beryllium has high n-α reaction sections in the thermal neutrons too, and therefore, it is possible in principle to use existing fission reactors with such relation of thermal and fast neutrons that while irradiating they have helium accumulation and beryllium structural damage rates close to the damages in the fusion reactor ITER. The preliminary neutron calculations indicate that at present, channels of high flux research reactor SM (Dimitrovgrad, Russia) are the better place for such experiments.

Influence of the proposed Project on the progress in the given area.

  1. Development and testing of the proposed methodology will give to investigators a powerful instrument for studying microstructure evolution of beryllium and its compounds under the specific effect of fusion spectrum neutrons at high temperatures. At present, the need in development of such methodology is very urgent due to the necessity to investigate radiation damageability of beryllium to be used in the fusion reactors ITER and DEMO.
  2. High temperature irradiation of beryllium and its compounds will be performed using developed methodology at 450-800 °C up to the damage dose of 1 dpa. First, the comprehensive kinetic study of radiation damages in beryllium and its alloys will be carried out at high irradiation temperature. Necessary kinetic relationships will be obtained for further development of the calculation model of microstructure evolution under neutron irradiation.

Competence of the Project participants in the given area.

During 40 years RIAR specialists perform investigations of radiation resistance of beryllium as a material for nuclear reactors of different purposes. For that, RIAR possesses of some research reactors for materials irradiation and a modern material science complex for post-irradiation examinations that allows realizing all scope of needed investigations under the given Project. During this time, RIAR specialists accumulated a great experience of large project implementation on beryllium study as a reactor material.

This project will be implemented by competent specialists including doctors of sciences, their scientific work on the indicated problem are regularly presented at international conferences and published in foreign reviews.

Expected results and their application.

Under this project the following work will be performed:

  • development and testing of methodology for beryllium specimens and pebbles irradiation under material damage parameters maximum close to those planned in fusion reactor ITER;
  • temperature dependences of thermal and physical properties changes of beryllium and its compounds, direct information using electron microscopes on the initiation and evolution of porous and dislocation microstructure will be obtained. The obtained data will be a basis to precise mechanisms of radiation structural damages and to construct analytical dependences characterizing changes in the main structural parameters in function of irradiation temperature.

Application area:
  • developed methodology will be called for irradiation tests of the promising grades of beryllium and its compounds in fusion reactors ITER and DEMO at the design parameters;
  • obtained results can be used in future for calculation models development of changes in structure and physical-mechanical properties under irradiation in the reactors ITER and DEMO;
  • results of the performed work will be published in the scientific literature, presented on seminars and conferences with the purpose to use the developed methodology for other investigations as well as to search for proposals on the practical implementation of the notions developed in the justification of materials for the fusion reactors ITER and DEMO.

Data on the work scope. The project implementation provides for following work scope:
  1. Calculating justification of the reactor experiment including identification of the irradiation cell, designing of the irradiation rigs, neutron-physical calculation of the spectrum and neutron intensity, calculation of the damage dose and transmutant accumulation in the specimens.
  2. Irradiation rig preparation and testing in the reactor SM that includes fabrication of tree irradiation rigs, their irradiation in the reactor SM at the temperatures 450, 600, 800 °C up to the damage dose of 1dpa under continuous temperature control during irradiation.
  3. Methodic base preparation for post-irradiation examinations that provides for adaptation of the existing facility for specimen type-sizes and measurements automation.
  4. The post-irradiation examinations including geometrical size measurements, determination of the physical (electrical resistivity, dynamic modulus of elasticity, hydrostatic density), and thermo-physical (heat expansion coefficient, thermal diffusivity) characteristics as well as micro structural investigations by scanning and transmission microscopy.
  5. Isothermal annealing of the irradiated beryllium specimens aimed to determine kinetic of transmutation helium release and study of the thermal stability and mechanisms of radiation defects and pore annealing.
  6. Final report preparation and issue.

Roles of foreign Collaborators. The Project Collaborator is Forschungszentrum Karlsruhe (FZK), Germany. The Institute for Materials Research I being part of FZK referred by Dr.Anton Moeslang and its specialists, is the leading European Center for development and investigations of beryllium materials for the fusion reactors ITER and DEMO. FZK has a great experience in investigations of beryllium materials irradiated in the European nuclear reactors and is ready to use this experience for cooperation under the Project.

The Collaborator will organize fabrication of beryllium and its compound specimens of the agreed type-sizes of BW companies production (“Brach Wellman”, USA, GVT “Goraeb Ferzuhtechnik”, Germany, and NGK, Japan), and will deliver theirs in RIAR. Later, beyond this project, the Collaborator will perform additional structural investigations of the irradiated specimens by analytical electronic microscopy method after completing testing of these specimens at RIAR. For this purpose, it is planned to return back this part of the specimens but now beyond the envisaged ISTC Project according to the particular supply contract free of charge.

Therefore, the results obtained on one material by two laboratories will be compared increasing validity and representativity of these results.

The Collaborator’s role in this Project will also consist in scientific-technical support and assistance for work execution under the Project in a respect of interests of different scientific organizations interested in successful achievement of the Project goals. The cooperation with the Collaborator is realized in form of scientific technical information exchange, mutual carrying out of experiments and investigations, discussions of the work progress and the obtained results in any acceptable forms.

Technical approaches and methodology. The work methodology consists in complex approach to the irradiation tests of beryllium and its compound and post-irradiation examinations accentuated on irradiation conditions in the area of previously non investigated, the most significant parameters for the designed fusion reactors. The work will be implemented on the modern technical base with using the reactor SM and experimental investigation methods that will permit to achieve the Project goals.


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