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Structure of Irradiated Materials

#0597


Fundamental Research of Materials Structure and Properties Changes Resulted from Irradiation by Means of Complex of Modern Physical Methods

Tech Area / Field

  • FIR-MAT/Materials and Materials Conversion/Fission Reactors

Status
8 Project completed

Registration date
04.04.1996

Completion date
15.01.2007

Senior Project Manager
Tocheny L V

Leading Institute
MIFI, Russia, Moscow

Supporting institutes

  • NIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad\nAll-Russian Scientific Research Institute of Non-Organic Materials named after A. Bochvar, Russia, Moscow

Collaborators

  • Global Nuclear Fuel , USA, NC, Wilmington

Project summary

Goals of the project:
a) Four classes of materials will be investigated during the work on the project:

- Zr alloys;
- Ni-Cr alloys;
- electroinsulating materials;
- shape-memory effect alloys.

b) Improvement of nuclear reactor exploitation safety and reorientation of specialists working in the nuclear weapons sphere to decision of peaceful problems.

The most important zirconium-type alloys under the investigation are zirconium-niobium, zirconium-niobium-iron-tin alloys and some others. The alloys were developed up to date by probes, without prediction study, nevertheless the atomic industry satisfied their needs enough. The further development of the industry is directed towards reactor safety improvement under high burn-up (60-70 MW a day/t of U) and extension of life-time of fuel elements up to 6-7 years. These items demand a more argued approach to the production to be trust and development of the materials with higher level of corrosional and mechanical stability properties under exploitation,-i.e. with more high level of radiation stability. There is no theory, describing adequately and precisely enough the corrosion destruction of these alloys and taking into account the presents of Fe, Sn and Nb atoms in them with various concentrations. The corrosion models development is restrained because of lack of information on redistribution and chemical state of enriching elements, iron and tin for example, in the metal and in oxide films both under reactor irradiation and in simple autoclave conditions at T=350 °C and at P=16.8 MPa. During the project implementation the corrosion processes and structure changes of these alloys, irradiated in the neutron field with fluence up to ~1023 n/cm2 (E > 0.1 MeV) will be investigated. The results of these investigations will give the possibility to clear up the reasons of accelerated corrosion, redistribution of Fe and Sn atoms connection both in alloys with initial structure and in their oxide films, the last being obtained during reactor irradiation. The reasons for reduction of radiation stability under high burn up conditions will be cleared up also.

The alloys on the base of nickel and chromium belong to the other class of construction materials often applicable. These alloys have good corrosion stability, but radiation blistering' may take place in them, the reasons of which are not still clear. In the project it is planing to investigate whether the initial stage of the polymorphal phase transition under the influence of irradiation is possible. The transition is accompanied by forming a short-range order in the location of atoms. One can probably obtain an alloy with optimal combination of radiation and corrosion stability possessing additionally good physical and mechanical characteristics due to this transition. The looking for of this optimum is included in the project.

Insulators investigations are included. Their utilization in flows of ionizing radiation must have structure and characteristics changes which have to be controllable and predictable. This is important for stabilization of the autocontrol circuits work.

The shape memory alloys are reasonable to be utilized in nuclear reactors automatic circuits, the last being sensitive to reactor regime changes. Though their using for necessities of nuclear engineering is tempting, it is limited because of lack of information on changes of their properties in powerful radiation flows. It is planing to obtain such information.

The plan includes both modeling of radiation and corrosion properties of materials and their experimental study of new materials with improved radiation and corrosion stability.

Experimental program of the project includes the study the changes of material properties under influence of the radiation within the nuclear reactors (the experimental reactor of MEPhI, the test reactor of NIIAR, Dmitrovgrad, the pulse reactor of VNIIEF, Arzamas-16, and the test reactor FEI, Obninsk) and of a beam of accelerated particles (the accelerator of FEI-Obninsk).

Expected results


1. Development of theoretical models of radiation defects generation, redistribution of atoms in different alloys and different phase generation under irradiation, the development of new technique based on methods of nuclear physics.
2. Obtaining new data on dislocation crystal structure and phase contents of radiation-stabilized zirconium based alloys, data on structure and kinetics growth of oxide films on their surface and chemical element redistribution among matrix, secondary phase and oxide film under reactor and autoclave condition having been obtained as well.
3. Phase diagram of Ni-Cr date and development of representations on phase creation and growth of phases and their stability under irradiation from accelerators and reactors will be restricted. The investigation results may be used for creation of Ni-Cr alloys with improved radiation stability.
4. nfluence of radiation effect on kinetics of phase transitions in titanic-nickel alloys having shape memory effect will be revealed. On the basis of results obtained recommendations for the "know-how" of alloys with stabilized shape memory effect for connecting elements in nuclear reactors should be produced.
5. Systematic data on influence of intensive flows of radiation of various kinds on conductivity and defect generation in insulators will be obtained. On the basis of results obtained radiation technologies should be developed for creating insulating materials stable at high fluence.

Foreign collaborators

The Recipients are ready for any collaboration with any organization which is interested in above mentioned investigations.


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