English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In PWR severe accident scenarios, involving a relocation of corium (core melt) into the lower head, the possible failure mode of the reactor pressure vessel (RPV), the failure time, the failure location and the final size of the breach are regarded as key elements, since they play an important part in the ex-vessel phase of the accident. In the framework of the LHF and OLHF programmes, the failure time and failure location predictions were obtained using numerical modelling and agreed reasonably well with the experimental values. However the final size of the failure is still an open issue. Analyses of both the LHF and OLHF experimental data (as well as of that from the Swedish FOREVER experiments) do not enable an assessment of the final size of the breach (in relation with the testing conditions and results). Indeed, the size of breach depends on the mode of crack propagation which is directly related to the variability in behaviour of the RPV material at high temperatures. To determine crack propagation and failure final size, 3D modelling would thus be needed with an adequate failure criterion which takes into account this material behaviour variability. This paper presents an outline of the methodology being used in a current research programme of IRSN, in partnership with CEA and INSA LYON. The aim is to model crack opening and crack propagation in French RPV lower head vessels under severe accidents conditions and to develop a new failure criterion for the 3D finite element models. CONCLUSIONS The numerical models developed in the framework of the LHF and OLHF programmes, have shown their capacity to predict the lower head failure time and the crack opening location. The results from the OLHF1 benchmark are generally similar for the different codes and are also in quite agreement with the experimental data. However, the study of mechanical property variability performed in the framework of this benchmark, showed that the maximum discrepancy relating to failure time could be as high as 33%. For a more accurate prediction of a crack's location and its propagation (leading to the final breach) only 3D finite element models are realistic. However all models are not yet able to correctly predict the crack propagation, mainly due to the variability in mechanical behaviour of the RPV material at high temperatures. To improve predictions, more investigation and work are required on the tearing criterion. The current joint experimental programme between IRSN/CEA/INSA Lyon, on the characterization of the French RPV materials, now in its final stages, would allow us to: predict the brittle/ductile behaviour of RPV materials from their chemical/metallurgical composition, characterize the vessel steel tearing properties at high temperatures. This will allow a better understanding of the influence of metallurgical composition on the kinetics of tearing which can initially be validated by simulating tests on tube, before being used to simulate the tearing propagation in the case of a reactor. The Japan Society of Mechanical Engineers NII-Electronic Library Service 15 International Conference on Nuclear Engineering Nagoya, Japan, April 22-26, 2007 ICONE15-10018 1 Copyright © 2007 by JSME A PROGRAMME ON CRACK OPENING AND PROPAGATION OF A LOWER HEAD DURING A HYPOTHETICAL PWR SEVERE ACCIDENT V. Koundy, C. Caroli Institut de Radioprotection et de Sûreté Nucléaire vincent.koundy@irsn.fr – cataldo.caroli@irsn.fr J.M. Gentzbittel, P. Matheron, L. Nicolas Commissariat à l'Energie Atomique jean-marie.gentzbittel@cea.fr – pmatheron@cea.fr laetitia.nicolas@cea.fr M. Coret Institut National des Sciences Appliquées michel.coret@insa-lyon.fr

ICONE15-10018 A PROGRAMME ON CRACK OPENING AND PROPAGATION OF A LOWER HEAD DURING A HYPOTHETICAL PWR SEVERE ACCIDENT