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In the present paper is described how the steady state and transient fuel rod performance code TRANSURANUS can be used for safety analyses of WWER reactors, as an example a rod ejection accident, resulting in Reactivity Initiated Accident (RIA), is analysed.

A simple one-point kinetics model has been incorporated into the version v1m2j99 of the TRANSURANUS code. This simple model is characterised by an effective delayed neutron fraction beta, a neutron generation time lambda (uppercase), an effective decay constant lamba (lowercase) for the delayed neutrons and constant temperature coefficient gamma (uppercase) of the reactivity for fuel and moderator.

Four representative fuel rods of the KOLA-3 data set from the International Fuel Preformance Database (IFPE Database) have been analysed employing the latest TRANSURANUS-WWER version. The main findings are:

-The enhanced fission gas release abeve 40MWd/kgU cannot be modelled with the standard fission gas release models. An attempt has been made to include the formation of the High Burnup Structure in the fission gas release model. Although reasonable results are obtained, further research is needed to better understand the mechanisms of the enhanced fission gas release at high burnup. This statement is valid for fuel rods of Western design as well for WWER fuel rods.

-The MATRO-N1 correlations for cladding creep and swelling lead to a systematic under-prediction of the radial and axial deformation. These results could indicate that pellet cladding interaction starts already at 20 to 25 MWd/kgU. The empirical correlation gives better results and is recommended unless the discrepancy obtained by the MATRO-N1 correlation can be resolved.

Additional information

Authors: MANALOVA ET AL, Institute for Nuclear Research And Nuclear Energy, Sofia (BG);LASSMANN ET AL, ITU, Karlsruhe, (DE)
Bibliographic Reference: Oral Report: 3rd International Seminar on WWER Fuel Perfomance Modelling and Experimental Support 4-8 October 1999, Pamporovo (BG)
Availability: 1 as paper EN 60771 ORA
ISBN: 954-9820-30-3
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