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Structure of Fuel Elements


Study of Structure of Materials Based on U-Pu-Zr alloy, their Thermodynamic Properties and Interaction with Materials of Fuel Element Shell under Quasi-Isothermal Conditions and Conditions of Non-stationary Exposure

Tech Area / Field

  • FIR-FUE/Reactor Fuels and Fuel Engineering/Fission Reactors

3 Approved without Funding

Registration date

Leading Institute
VNIITF, Russia, Chelyabinsk reg., Snezhinsk

Supporting institutes

  • All-Russian Scientific Research Institute of Non-Organic Materials named after A. Bochvar, Russia, Moscow

Project summary

The goal of the Project is to obtain characteristics of U-Pu-Zr system and to study behavior of U-Pu-Zr-based metallic fuel in accidental conditions simulating coolant loss at atomic plant.

One of the options for atomic energy evolution is development of fast neutron reactors with metallic fuel on the basis of system U-Pu-Zr. Concepts of such reactors have been developed both in Russia and abroad. At present there is a successful project EBR-2 under way developed at U.S. Argon National Laboratory. It should be pointed out that as a result of considerable nuclear weapons cuts a large amount of weapon-grade nuclear materials - plutonium and uranium - is released. Current needs of civil industry in these fissile materials are limited, and the most promising and metal consuming direction in disposition is plutonium use as fuel for civil reactors, and in particular, for fast neutron reactors.

At the same time interest towards the fast neutron reactors is caused by their safer operation compared to thermal neutron reactors.

The metallic fuel on the basis of the system U-Pu-Zr is high active in terms of interaction with shell materials. Besides that it has a complex phase and element composition. During exposure the phase composition changes and the fuel elements are redistributed, therefore there is a permanent interest towards data referred to fuel behavior under exposure in different modes.

For practical use of such alloys as fuel for atomic power reactors we need to address a wide range of issues of both technological and fundamental nature, some part of them being addressed under this Project.A scientific merit of the work planned involves

obtaining of new fundamental results based on application of original methods for investigation of radiation defect formation and kinetics of radiation simulated processes in alloys, obtaining thermodynamic characteristics of U-Pu-Zr system, as well as data on change of phase composition at fuel interaction with materials of fuel elements shell.

We propose to study dependencies of defect accumulation rate in alloys with different structure morphology at small degree of burning out reached during exposure in burst reactor. To determine small concentrations of the accumulated defects we assume to use such research method as positron-electron annihilation. We'll study mutual diffusion of fuel elements both under isothermal conditions and under conditions of impulse exposure.

During the project implementation we plan to perform the following activities: manufacture samples for different kinds of research both before and after the exposure; pursue experiments on the sample exposure with neutron impulses in research reactors YAGUAR and IGRIK at different impulse duration, their number, and temperature; perform different metal-physical investigations of the samples before and after the exposure, such as metallographic, X-ray diffraction, electron-microscopic, study of electrical resistance change under isothermal conditions and in the process of neutron impulse irradiation; micro-X-ray-spectral investigation of impulse exposure influence under high temperatures on the diffusion zone width in shell and redistribution of components and phase formation in the system U-Pu-Zr; investigation of annihilation parameter change in exposed and non-exposed samples by the method of positron annihilation.

The research in the case of exposure by a single neutron pulse with duration of 40-2000 mcs will enable to investigate material behavior during deviation from normal mode of stationary reactors operation in situations similar to accidents with coolant loss at initial stages.

Preliminary results of investigating thermodynamic and diffusion properties of the system U-Pu-Zr were presented by the authors of the project at the International Conference "Actinides-93" (U.S.), and at International Workshop "Calculational and Experimental Support of Research on Safety of Nuclear Energy and Its Fuel Cycle" (Moscow, 1993). Major peculiarities of methods for investigating radiation damage and irradiation devices were presented at the 1st Urals International Workshop on Physics of Radiation Damage of Metals and Alloys (Snezhinsk, Russia, 1995).

While implementing the Project it is planned to use unique burst reactors and methods developed specially to obtain characteristics of fissile materials under non-stationary exposure conditions.

Participation of foreign collaborators in the Project could involve providing of their materials for the research, joint discussions of measurement results, verification of measurement methods, etc.

During implementation of the project it is planned to enlist a large number of high level specialists working in the area of weapon development and production, investigation of plutonium properties, and technology of its compounds manufacture that, on the one hand, will ensure a high scientific level of the project, and on the other hand, will contribute to reorientation of the scientists to work in peaceful areas.


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