## Abstract

The basic concepts of the fuel rod modelling was reviewed and their limitations are discussed.Three more general modelling concepts are briefly outlined: one-dimensional models versus 2-D or 3-D models; steady-state versus transient modelling; empirical versus mechanical models. The fuel rod behaviour is determined by thermal, mechanical and physical processes such as densification, swelling, gas release, irradiation damage etc. It is shown that the macroscopic behaviour of a fuel rod is to a large extent determined by the local UO{sub 2} microstructure. Any fuel rod model must include the solution of the heat conduction equation and the principal mechanical equations i. e. equilibrium and compatibility, together with constitutive equations. The basic limitations from the different assumptions made for the solution of the governing equations are identified. It was shown that the thermal and the mechanical analysis are strongly coupled and therefore errors are propagated. The individual correlations and processes are also not error-free and in only some cases can individual errors be estimated. There is almost for all processes a good understanding of the dominating parameters but the unsolved problem is how local quantities such as pores and grain structure, stresses etc. evolve during the irradiation. Thus the wrong input data
More>>

Lassmann, K;
O`Carroll, C;
Van de Laar, J;
Ray, I;

^{[1] }Stefanova, S;^{[2] }Chantoin, P^{[3] }- Commission of the European Communities, Karlsruhe (Germany). European Inst. for Transuranium Elements
- Bylgarska Akademiya na Naukite, Sofia (Bulgaria). Inst. za Yadrena Izsledvaniya i Yadrena Energetika
- International Atomic Energy Agency, Vienna (Austria)

## Citation Formats

Lassmann, K, O`Carroll, C, Van de Laar, J, Ray, I, Stefanova, S, and Chantoin, P.
Main concepts and objectives of fuel performance modelling and core development.
Bulgaria: N. p.,
1994.
Web.

Lassmann, K, O`Carroll, C, Van de Laar, J, Ray, I, Stefanova, S, & Chantoin, P.
Main concepts and objectives of fuel performance modelling and core development.
Bulgaria.

Lassmann, K, O`Carroll, C, Van de Laar, J, Ray, I, Stefanova, S, and Chantoin, P.
1994.
"Main concepts and objectives of fuel performance modelling and core development."
Bulgaria.

@misc{etde_456063,

title = {Main concepts and objectives of fuel performance modelling and core development}

author = {Lassmann, K, O`Carroll, C, Van de Laar, J, Ray, I, Stefanova, S, and Chantoin, P}

abstractNote = {The basic concepts of the fuel rod modelling was reviewed and their limitations are discussed.Three more general modelling concepts are briefly outlined: one-dimensional models versus 2-D or 3-D models; steady-state versus transient modelling; empirical versus mechanical models. The fuel rod behaviour is determined by thermal, mechanical and physical processes such as densification, swelling, gas release, irradiation damage etc. It is shown that the macroscopic behaviour of a fuel rod is to a large extent determined by the local UO{sub 2} microstructure. Any fuel rod model must include the solution of the heat conduction equation and the principal mechanical equations i. e. equilibrium and compatibility, together with constitutive equations. The basic limitations from the different assumptions made for the solution of the governing equations are identified. It was shown that the thermal and the mechanical analysis are strongly coupled and therefore errors are propagated. The individual correlations and processes are also not error-free and in only some cases can individual errors be estimated. There is almost for all processes a good understanding of the dominating parameters but the unsolved problem is how local quantities such as pores and grain structure, stresses etc. evolve during the irradiation. Thus the wrong input data for local processes is considered as one of the main source of uncertainty. Fission gas release and swelling could not be described by the corresponding equations without introducing some free parameters. The center line predictions of two codes for FUMEX blind exercise are given. It is stated that since the D-COM exercise in 1984, fuel rod performance codes have been improved considerably and must be now considered as mature tools for further optimisation of fuel rods. 1 tab., 12 figs., 22 refs.}

place = {Bulgaria}

year = {1994}

month = {Dec}

}

title = {Main concepts and objectives of fuel performance modelling and core development}

author = {Lassmann, K, O`Carroll, C, Van de Laar, J, Ray, I, Stefanova, S, and Chantoin, P}

abstractNote = {The basic concepts of the fuel rod modelling was reviewed and their limitations are discussed.Three more general modelling concepts are briefly outlined: one-dimensional models versus 2-D or 3-D models; steady-state versus transient modelling; empirical versus mechanical models. The fuel rod behaviour is determined by thermal, mechanical and physical processes such as densification, swelling, gas release, irradiation damage etc. It is shown that the macroscopic behaviour of a fuel rod is to a large extent determined by the local UO{sub 2} microstructure. Any fuel rod model must include the solution of the heat conduction equation and the principal mechanical equations i. e. equilibrium and compatibility, together with constitutive equations. The basic limitations from the different assumptions made for the solution of the governing equations are identified. It was shown that the thermal and the mechanical analysis are strongly coupled and therefore errors are propagated. The individual correlations and processes are also not error-free and in only some cases can individual errors be estimated. There is almost for all processes a good understanding of the dominating parameters but the unsolved problem is how local quantities such as pores and grain structure, stresses etc. evolve during the irradiation. Thus the wrong input data for local processes is considered as one of the main source of uncertainty. Fission gas release and swelling could not be described by the corresponding equations without introducing some free parameters. The center line predictions of two codes for FUMEX blind exercise are given. It is stated that since the D-COM exercise in 1984, fuel rod performance codes have been improved considerably and must be now considered as mature tools for further optimisation of fuel rods. 1 tab., 12 figs., 22 refs.}

place = {Bulgaria}

year = {1994}

month = {Dec}

}