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Uranium Dioxide Properties

#0534


Complex Investigation of Uranium Dioxide and Mixed Uranium-Plutonium Dioxide Fuel's Properties for Prediction of Performance and Operating Characteristics and Verification of Calculating Models of Fuel elements for Operative and Advanced NPP.

Tech Area / Field

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

Status
8 Project completed

Registration date
28.12.1995

Completion date
15.03.2001

Senior Project Manager
Tocheny L V

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

Supporting institutes

  • MIFI, Russia, Moscow\nNIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad\nState Holding Company "Ulba", Kazakstan, Ust Kamenogorsk

Collaborators

  • Belgonucléaire, Belgium, Brussels\nFRAMATOME / Nuclear Fuel, France, Lyon\nEuropean Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe

Project summary

Although the last years of nuclear energetics development the dioxide fuel has been sufficiently investigated, however more profound knowledge of its performance characteristics is necessary both out-of-pile conditions and under irradiation.

Moreover it is not necessary to obtain experimental measurements of properties only but and to carry out comparative analysis of previous regularities and its additional processing.

It is proposed to design the techniques of investigations, to perform experimental-analitical investigation or to define more precisely the dependencies of next uranium and uranium-plutonium dioxide characteristics for samples with different sizes and composition:

1. Densification at the beginning of irradiation in the temperature range of 600° С to 2000° С and for fission rates up to 1х103 fissions/(cm3)x(sec).

2. Heat capacity in the temperature range up to melting point.

3. Thermal conductivity ( as function of temperature and composition.

4. Melting temperature from fission products accumulation.

5. Temperature of brittle-elastic transition as function of composition.

6. Fission gas accumulation from temperature, amorphisation degree, structure, burnup, initial density and more accurate definition of fission gas accumulation mechanisms.

7. Free and suppressed swelling versus burnup and temperature of irradiation.

8. Thermoelectric power effects and electrophysical properties changes as a function of irradiation parameters and correlations its with thermal, physico-chemical properties.

9. Fission rates influence on mechanical interaction between fuel and cladding.

10. High-temperature and radiation-induced creep.

11. Strengths characteristics at compression and tensile.

12. Redistribution of fissile components over the volume.

Uranium dioxide, plutonium dioxide and their mixtures of various composition have been proposed to use as materials for investigation. Dioxides with dopes of unfissile components and different structure should be used to investigate the enhancement of plasticity.

Technical Approach and Methodology.

At each stage of the project the methods will be employed:

- methods of in-pile investigations of nuclear fuels;

- theoretical and experimental methods of physical phenomena studies based on analytical approach to the solving problems;

- methods of mathematical simulation of the inpidual complex physical processes by different approximation.

Expected Results.

Expected experimental and analytical investigations and the processing of available and accumulated data will permit to deepen the notions about physical and physicochemical phenomena in the materials and the constructions of fuel-elements and to define more precisely the calculation's techniques of prediction the fuel-elements lifetime. It is proposed to define more precisely the dependences of thermal and mechanical properties, the fuel-elements dimensional stability and gas release from irradiated tablets on the technological properties of fuel tablets, their composition, structure, main technological regimes and the properties of raw materials. Considerable efforts will be structure, main technological regimes and the properties of raw materials. Considerable efforts will be directed on the improvement and the development a techniques of physical experiment and increase the precision of measurements during the project.

The results of analytical treatment of experimental data will be used to correct the operating programs that allows to increase the reliability of calculation by reason of decrease the conservatively of calculated estimations on base of the taken assurance coefficient. The increase of correction at the definition of connections the fuel ceramic tablet's technological characteristics of the different composition and the technological production peculiarities of the experimental samples with the fuel ceramics performances, taking into account the physicochemical processes under irradiation, will allow to give some suggestions directed on further increase the fuel-element's quality for industrial production and provide with increased demandes of prevention of accidents during the exploitation of nuclear reactors. Worthy of note, that the results of investigation the experimental fuel's ceramics produced on base of the plutonium dioxide and the uranium-plutonium dioxides of different composition (with requirements of the fuel-elements for thermal and fast breeder reactors ), which will be obtained during the project, will be used for the estimations on possibility of weapons plutonium application as the fissile component of ceramic dioxide composition. All solutions of this project will be decided with a glance to guaranteeing of required definiteness and statistical reliability of the measurements and result's treatments which are necessary for the calculations predictive the fuel-element's behaviour at the different emergencies and burnup levels as is also a maximum.

Execution of this project will provide with performance of licence's basis for high values of the nuclear fuel's burnup of the uranium, plutonium and the mixed fuels, the increase of the fuel-elements lifetime on condition that the level of thermal and mechanical interaction between the uranium dioxide and uranium-plutonium fuel-elements and cladding from the zirconium alloies and the level of physico-chemical interaction are decreases.

This project allows to use complex and expensive equipment more effective and to attract the scientists and engineers, who have made substantial contributions to the ever developing area of nuclear weapons, for deeper investigations of uranium dioxide fuels used in European water-cooled reactors. When experimental data's volume will be obtain in the form of sets included structure,composition and properties, it will be presented a reference book for international exchange of information.


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